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Purpose: The cornea is richly innervated by the trigeminal ganglion (TG) and its function supported by secretions from the adjacent lacrimal (LG) and meibomian glands (MG). In this study we examined how pigment epithelium-derived factor (PEDF) gene deletion affects the cornea structure and function., Methods: We used PEDF hemizygous and homozygous knockout mice to study effects of PEDF deficiency on corneal innervation assessed by beta tubulin staining, mRNA expression of trophic factors, and PEDF receptors by adjacent supporting glands, corneal sensitivity measured using a Cochet-Bonnet esthesiometer, and tear production using phenol red cotton thread wetting., Results: Loss of PEDF was accompanied by reduced corneal innervation and sensitivity, increased corneal surface injury and tear production, thinning of the corneal stroma and loss of stromal cells. PEDF mRNA was expressed in the cornea and its supporting tissues, the TG, LG, and MG. Deletion of one or both PEDF alleles resulted in decreased expression of essential trophic support in the TG, LG, and MG including nerve growth factor, brain-derived neurotrophic growth factor, and GDNF with significantly increased levels of NT-3 in the LG and decreased EGF expression in the cornea. Decreased transcription of the putative PEDF receptors, adipose triglyceride lipase, lipoprotein receptor-related protein 6, laminin receptor, PLXDC1, and PLXDC2 was also evident in the TG, LG and MG with the first three showing increased levels in corneas of the Pedf+/- and Pedf-/- mice compared to wildtype controls. Constitutive inactivation of ERK1/2 and Akt was pronounced in the TG and cornea, although their protein levels were dramatically increased in Pedf-/- mice., Conclusions: This study highlights an essential role for PEDF in corneal structure and function and confirms the reported rescue of exogenous PEDF treatment in corneal pathologies. The pleiotropic effects of PEDF deletion on multiple trophic factors, receptors and signaling molecules are strong indications that PEDF is a key coordinator of molecular mechanisms that maintain corneal function and could be exploited in therapeutic options for several ocular surface diseases.

Purpose: Lacrimal gland excision (LGE) has been utilized in several studies to model aqueous tear deficiency, yet sex as a biological variable has not been factored in to these reports. This study compared corneal pathology in male and female mice following LGE-induced dry eye., Methods: An LGE of either the extraorbital lacrimal gland (single LGE) or both the extraorbital and intraorbital lacrimal glands (double LGE) was performed in male and female C57BL/6J and Balb/cJ mice to produce dry eye of graded severity. Following excision, tearing was evaluated with phenol red thread, and corneal fluorescein staining was scored to quantify the severity of damage. Corneas were evaluated for apoptosis by the TUNEL assay and for cell proliferation using Ki67 staining. Furthermore, corneas were harvested and analyzed for macrophages via flow cytometry., Results: Baseline tearing levels were similar in male and female mice, and LGE resulted in comparable reductions in tearing with the lowest levels recorded after double LGE. As determined by fluorescein staining, LGE produced more severe damage to the cornea in female C57BL/6J and Balb/cJ mice. Double LGE increased TUNEL and Ki67 staining in the cornea, with greater increases found in female mice. Furthermore, LGE produced a greater increase in the total number of corneal macrophages in female mice., Conclusions: These results indicate that female mice are more susceptible to LGE-induced corneal damage. The mechanisms involved in producing these sex differences still need to be elucidated but may involve increased inflammation and macrophage infiltration.

Purpose: Ocular pain and discomfort are the most defining symptoms of dry eye disease. We determined the ability of topical progesterone to affect corneal sensitivity and brainstem processing of nociceptive inputs., Methods: Progesterone or vehicle gel was applied to the shaved forehead in male Sprague Dawley rats. As a site control, gel also was applied to the cheek on the side contralateral to corneal stimulation. Corneal mechanical thresholds were determined using the Cochet-Bonnet esthesiometer in intact and lacrimal gland excision-induced dry eye animals. Eye wipe behaviors in response to hypertonic saline and capsaicin were examined, and corneal mustard oil-induced c-Fos immunohistochemistry was quantified in the brainstem spinal trigeminal nucleus., Results: Progesterone gel application to the forehead, but not the contralateral cheek, increased corneal mechanical thresholds in intact and lacrimal gland excision animals beginning <30 minutes after treatment. Subcutaneous injection of the local anesthetic bupivacaine into the forehead region before application of progesterone prevented the increase in corneal mechanical thresholds. Furthermore, progesterone decreased capsaicin-evoked eye wipe behavior in intact animals and hypertonic saline evoked eye wipe behavior in dry eye animals. The number of Fos-positive neurons located in the caudal region of the spinal trigeminal nucleus after corneal mustard oil application was reduced in progesterone-treated animals., Conclusions: Results from this study indicate that progesterone, when applied to the forehead, produces analgesia as indicated by increased corneal mechanical thresholds and decreased nociceptive responses to hypertonic saline and capsaicin.

Purpose: To compare corneal biomechanical properties after in vivo and ex vivo cross-linking (CXL) using rose bengal-green light (RGX) or riboflavin-UVA (UVX)., Methods: Corneas of 30 rabbits were treated in vivo by the two CXL modalities monolaterally (Group 1) or bilaterally (Group 2). Rabbits in Group 1 were euthanized 1 month after treatments and in Group 2 two months after treatment. Ex vivo CXL was also performed. Eyes were measured by Scheimpflug air puff corneal deformation imaging (Corvis ST) under constant IOP. Corneal deformation parameters were assessed. Inherent corneal biomechanical properties were estimated using inverse finite element modeling., Results: Peak to peak distance decreased 16% 2 months after RGX, and 4% and 20% 1 and 2 months after UVX, respectively. The equivalent Young's modulus (Eeq) increased relative to the control during the post treatment period for both RGX and UVX. The Eeq increased by factors of 3.4 (RGX) and 1.7 (UVX) 1 month and by factors of 10.7 (RGX) and 7.3 (UVX) 2 months after treatment. However, the Eeq values for ex vivo CXL were much greater than produced in vivo. The ex vivo Eeq was greater than the 1-month in vivo values by factors of 8.1 (RGX) and 9.1 (UVX) and compared with 2 month by factors of 2.5 (RGX) and 2.1 (UVX)., Conclusions: These results indicate that corneal stiffness increases after CXL, and further increases as a function of time after both RGX and UVX. Also, while biomechanical properties determined after ex vivo CXL are indicative of corneal stiffening, they may not provide entirely accurate information about the responses to CXL in vivo.

Purpose: The purpose of this study was to use noncontact optical coherence elastography (OCE) to evaluate and compare changes in biomechanical properties that occurred in rabbit cornea in situ after corneal collagen cross-linking by either of two techniques: ultraviolet-A (UV-A)/riboflavin or rose-Bengal/green light., Methods: Low-amplitude (≤10 μm) elastic waves were induced in mature rabbit corneas by a focused air pulse. Elastic wave propagation was imaged by a phase-stabilized swept source OCE (PhS-SSOCE) system. Corneas were then cross-linked by either of two methods: UV-A/riboflavin (UV-CXL) or rose-Bengal/green light (RGX). Phase velocities of the elastic waves were fitted to a previously developed modified Rayleigh-Lamb frequency equation to obtain the viscoelasticity of the corneas before and after the cross-linking treatments. Micro-scale depth-resolved phase velocity distribution revealed the depth-wise heterogeneity of both cross-linking techniques., Results: Under standard treatment settings, UV-CXL significantly increased the stiffness of the corneas by ∼47% (P < 0.05), but RGX did not produce statistically significant increases. The shear viscosities were unaffected by either cross-linking technique. The depth-wise phase velocities showed that UV-CXL affected the anterior ∼34% of the corneas, whereas RGX affected only the anterior ∼16% of the corneas., Conclusions: UV-CXL significantly strengthens the cornea, whereas RGX does not, and the effects of cross-linking by UV-CXL reach deeper into the cornea than cross-linking effects of RGX under similar conditions.

Purpose: We investigated how the microRNA (miRNA) modifies the expression of silent mating type information regulation 2 homolog 1 (SIRT1) in diabetic corneas., Methods: The bioinformatic assay was used to predict which miRNAs might regulate the expression of SIRT1. A lipid transfection protocol was used to upregulate or knockdown the miRNA expression in TKE2 cells. Adenovirus-expressing short interfering RNA was used to knockdown the expression of SIRT1 in TKE2 cells and Ins2(Akita/+) mice were used to evaluate how miRNA promotes diabetic corneal epithelial wound healing. Cell cycle status was determined by flow cytometry assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to analyze the cell viability., Results: Nine miRNAs were selected for quantitative PCR (qPCR) detection after bioinformatics analysis. The miR-204-5p merited further investigation, because it was increased almost 5-fold in diabetic corneal epithelia compared to nondiabetic control corneal epithelia. Using luciferase activity assay, we identified SIRT1 was a direct target of miR-204-5p. The results of flow cytometry and MTT assay demonstrated that downregulation of miR-204-5p increased TKE2 cell growth and restored cell cycle progression in high glucose (HG) conditions by the regulation of Cyclin D1 and p16. Furthermore, we showed downregulation of miR-204-5p promoted HG attenuation of corneal epithelial wound healing via upregulation of SIRT1 in Ins2(Akita/+) mice., Conclusions: Our data provide firm evidence of a role for miR-204-5p in the direct regulation of SIRT1 in diabetic corneas and identified the miR-204-5p-mediated regulation of SIRT1 contributes to the delay of epithelial cell cycle traversal in diabetic keratopathy. : Chinese Abstract., (Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: We correlated scleral IOP to assigned IOP using pneumatonometry in cadaver eyes before and after Boston type I keratoprosthesis (KPro) implantation., Methods: Corneal IOP and scleral IOP at the superonasal, superotemporal, inferotemporal, and inferonasal quadrants were measured using pneumatonometry in six cadaver eyes cannulated with an infusion line with assigned IOP held at 20, 30, 40, and 50 mm Hg. Measurements of scleral IOP at the same location were repeated after a KPro was implanted. Correlations between scleral IOP and assigned IOP were analyzed for the entire group of eyes, and for each individual eye before and after KPro. One eye was tested by another masked grader for interobserver variability., Results: Scleral IOP measured higher than corneal IOP by a mean of 13.2 mm Hg. For group analysis, pre-KPro scleral IOP had a positive and linear correlation with assigned IOP in all quadrants (P < 0.00001), and this correlation was preserved after KPro implantation (P < 0.00001). There was strong interobserver agreement in all measurement sites (P < 0.001). In analyses of individual eyes, scleral IOP measured at the inferotemporal quadrant confirmed the strong linear association between scleral IOP and assigned IOP before and after KPro for all study eyes. A Bland-Altman plot showed that the difference in scleral IOP between pre-KPro and post-KPro eyes fell mostly within ± 5 mm Hg., Conclusions: Scleral IOP measured by pneumatonometry may be used to estimate IOP in cadaver eyes with and without keratoprosthesis. This may be a potential modality for assessing IOP for patients with corneal pathology or keratoprosthesis.

Purpose: To compare the clinical results of cultivated oral mucosal epithelial cell sheet transplantation (COMET) of substrate-free sheets with those of COMET of amniotic membrane (AM)-based sheets., Methods: Sixteen eyes receiving COMET of substrate-free sheets (substrate-free group) were studied retrospectively and compared with disease-, age-, and ocular surface status-matched eyes undergoing COMET with AM serving as the substrate (AM group). Each group consisted of six eyes with chemical injury, six with pseudo-ocular cicatricial pemphigoid, two with Stevens-Johnson syndrome, and two with ocular cicatricial pemphigoid. Graft survival rate, best-corrected visual acuity (BCVA), and neovascularization (NV) were assessed., Result: In all 32 eyes, the entire corneal surface on which the cultivated autologous oral mucosal epithelium sheet had been placed was free of epithelial defects at postoperative day 2. The success rates of COMET at 12 months after surgery were 62.5% in the substrate-free sheet group and 43.8% in the AM group. A Kaplan-Meier curve revealed that the graft survival rate in the substrate-free group was significantly superior to that in the AM group (P = 0.046). Mean postoperative BCVA improved significantly at 1, 3, and 6 months in the substrate-free sheet group, and BCVA was significantly better than that in the AM group at all time points. Postoperative NV improved significantly in the substrate-free group at all time points., Conclusions: A better midterm clinical outcome was achieved with COMET of a substrate-free cell sheet than with COMET of AM as a substrate for treating severe stem cell deficiency.

Purpose: To investigate the changes in functional visual acuity (VA) and higher order aberrations in dry eye patients., Methods: In this prospective comparative case series, 22 right eyes were classified into those with or without superficial punctate keratopathy (SPK) in the central cornea of 22 patients with Sjögren syndrome; 10 right eyes of 10 normal subjects served as the control. Serial measurements of VAs using a functional VA measurement system and higher order aberrations using a wavefront sensor were performed under blink-free conditions without topical anesthesia over a 10-second period. The parameters for each measurement were compared among the SPK-positive and -negative and normal groups. The correlation between those parameters was also analyzed., Results: Dry eye with SPK showed significant deterioration of visual function and optical quality compared with dry eye without SPK and in normal eyes, as detected by both the visual maintenance ratio (VMR; P < 0.05) and the variation of VA (P < 0.05) and by comalike and total higher order aberrations (P < 0.05). Moreover, the severity of epithelial damage at the central cornea correlated significantly with VMR (P < 0.01) and variation of VA (P < 0.01) as well as comalike (P < 0.05) and total higher order aberrations (P < 0.05). The dry eye group without SPK showed minor visual deterioration compared with normal eyes, as detected only by VMR (P < 0.05)., Conclusions: Optical disturbances at the central optical zone of the cornea in dry eye disease may affect visual performance. Functional VA measurement may be an applicable method of evaluating visual performance in dry eyes that is as efficient as wavefront aberration measurements.

PURPOSE. This study seeks to characterize corneal functions and complications in a streptozocin (STZ)-induced rat model of type I diabetes mellitus (DM) and to understand the pathogenesis of diabetic keratopathy. METHODS. DM was induced via STZ injection in Sprague-Dawley rats. Body weight, length, and corneal size were measured and compared with the age-matched normal controls. Corneal morphology and histology were evaluated with slit lamp, digital confocal microscopy and hematoxylin and eosin staining. Tear secretion was measured with cotton threads, and corneal sensitivity was determined with an esthesiometer. Protein expression and distribution were assessed with Western blotting and immunohistochemistry. Wound healing was determined using an in vivo corneal epithelial debridement model. RESULTS. Compared with the normal control rats, STZ rats had reduced body weight, and body length, but minimally affected corneal size. No significant changes in ocular surface regularity, corneal thickness, and morphology were noted in diabetic corneas. STZ rats showed stronger Rose Bengal staining, decreased tear secretion, slightly attenuated sensitivity, less innervation, delayed epithelial wound healing, and impaired epidermal growth factor receptor signaling in their corneas. While the expression of adherens junction protein β-catenin, and tight junction proteins occludin and ZO-1 was unchanged, the formation of these junctions after wound closure was delayed. CONCLUSIONS. Pathogenesis of diabetic keratopathy involves multiple tissues and/or cell types and several events including reduced tear secretion, impaired innervation, weakened cell junction, and altered wound responses. These insights may prove useful for the clinical translation of evolving strategies for the management and treatment of diabetic corneal complications.

Purpose: To investigate binocular visual acuity and depth of focus when one eye forms images through a typical pupil diameter aperture (4 mm) and the other eye through a small pupil of 1.5-mm diameter., Methods: Using a recently developed adaptive optics binocular visual simulator, through focus monocular and binocular visual acuity were measured in three subjects under specially simulated visual conditions: right eyes had "small aperture" vision through a 1.5-mm pupil diameter and left eyes had normal vision through 4-mm pupil diameter. The measurements were performed in photopic and mesopic conditions., Results: An increase in binocular and monocular (for the small-aperture eye) depth of focus was measured with respect to the 4-mm pupil diameter eye. It ranged from 1 to 1.5 diopter (D) depending on the threshold requirement and the visibility conditions. For photopic conditions, the J2 visual acuity level was reached at 1 D of defocus for the 4-mm pupil diameter case, while for the 1.5-mm, the J2 level was reached at 2.5 D. Binocular summation occurred only in far vision conditions (no defocus added). For near vision, binocular visual acuity closely followed the values of monocular visual acuity for the eye with the smaller aperture., Conclusions: The small-aperture effect to increase depth of focus in the human eye was successfully implemented in a binocular visual simulator. Although certain limitations exist, the small-aperture approach provided a simple but attractive solution to increase depth of focus in the human eye.

Purpose: To evaluate by vector analysis the corneal astigmatic changes occurring in keratoconic corneas during a 3-year follow-up and to determine the relationship between these changes and other clinical changes., Methods: Keratoconic eyes (n = 114) of 75 patients ranging in age from 14 to 70 years were retrospectively reviewed in four different centers. In all cases, a 3-year follow-up was completed after the diagnosis of keratoconus. Visual, refractive, keratometric, aberrometric, internal astigmatism (IA), and pachymetric changes were evaluated during the follow-up. In addition, corneal astigmatic changes were evaluated by examining the following parameters, using a modification of the Alpins vectorial method: evolutive astigmatism (EA) and angle of error (AE)., Results: An increase in the magnitude of refractive (P = 0.02) and corneal astigmatism (P = 0.05) was found. The mean magnitude of EA was 1.21 ± 0.97 D at 3 years, with no significant changes at each annual visit (P ≥ 0.52). Mean absolute AE increased significantly by the end of the follow-up (P < 0.01). Absolute AE and the increase in corneal astigmatism were found to correlate at 2 years (r = 0.675, P < 0.01). This correlation became poorer at 3 years (r = 0.352, P = 0.02). The magnitude of the EA was also found to be significantly correlated with central corneal thinning (r = -0.441, P = 0.02). Multiple regression analysis revealed that the magnitude of EA at 3 years correlated significantly with the baseline sphere and IA (R² = 0.86, P < 0.01)., Conclusions: Corneal vector astigmatic changes are related to some signs of keratoconus progression and are therefore predictive.

Purpose: To measure the density of cells in different layers of the cornea and to determine whether morphologic changes of the subbasal corneal nerve plexus are present in eyes with the pseudoexfoliation (PEX) syndrome., Methods: Twenty-seven patients with unilateral PEX syndrome and 27 normal controls were investigated. All eyes underwent corneal sensitivity measurements with an esthesiometer and in vivo confocal microscopic study. Densities of the epithelial, stromal, and endothelial cells were measured. The density and tortuosity of the subbasal corneal nerve plexus were also evaluated., Results: Eyes with PEX syndrome had significantly lower cell densities in the basal epithelium (P = 0.003), anterior stroma (P = 0.007), intermediate stroma (P = 0.009), posterior stroma (P = 0.012), and endothelium (P < 0.0001) than in the corresponding layers of normal eyes. PEX eyes also had lower subbasal nerve densities and greater tortuosity of the nerves than normal eyes. Fellow eyes of patients with PEX also had significantly lower densities of the basal epithelial and endothelial cells than the normal eyes. Corneal sensitivity was significantly decreased in PEX eyes, and this was significantly correlated with the decrease of basal epithelial cell and subbasal nerve densities., Conclusions: These results have shed light on understanding of the pathogenesis of decreased corneal sensitivity in eyes with PEX syndrome. PEX syndrome is probably a binocular condition for which keratopathy of the fellow eye also requires observation.

Purpose: To evaluate the role of umbilical cord serum therapy in cases of acute ocular chemical burns., Methods: In a double-blind prospective randomized controlled clinical study, 33 eyes of 32 patients with acute ocular chemical burns of grade III, IV, and V severity were randomized into three groups: umbilical cord serum (n = 12), autologous serum (n = 11), and artificial tears (0.5% HPMC+0.3% glycerin; n = 10). In addition, all eyes received standard medical therapy. The parameters evaluated were pain score, size, and area of epithelial defect, extent of limbal ischemia, corneal clarity, and symblepharon formation. The patients were followed up at day 1, 3, 7, 14, and 21 and at the end of months 1, 2, and 3., Results: Mean time to complete epithelialization was 21.16 ± 26.81, 56.6 ± 35.5, and 40.13 ± 35.79 days in cord serum, autologous serum, and artificial tears groups respectively (P = 0.02). By day 21, the mean percentage decrease in epithelial defect diameter was 94.63 ± 11.99 with cord serum compared with 53.17 ± 34.81 and 64.22 ± 42.43 with autologous serum and artificial tears, respectively (P = 0.01). By month 3, the extent of limbal ischemia with cord serum showed a mean percentage decrease of 73.43 ± 25.51 compared with 35.64 ± 25.60 and 43.71 ± 28.71 with autologous serum and artificial tears, respectively (P = 0.008). More patients had clear corneas with cord serum compared with autologous serum and artificial tears (P = 0.048). No significant difference was seen between the groups with regard to symblepharon formation (P = 0.07)., Conclusions: Umbilical cord serum therapy is more effective than autologous serum eye drops or artificial tears in ocular surface restoration after acute chemical injuries. (www.controlled-trials.com number, ISRCTN08131903.).

Purpose: To examine the role of Bowman's layer (BL) on the nature of anterior corneal regeneration after excimer laser phototherapeutic keratectomy (PTK)., Methods: A cohort of 13 patients underwent PTK to remove either 7 mum of BL for treatment of primary recurrent corneal erosions (RCE; six patients) or complete BL removal (15-mum ablation) to treat RCE or poor vision secondary to map-dot-fingerprint (MDF) dystrophy (seven patients). Clinical examinations and laser-scanning in vivo confocal microscopy (IVCM) were conducted before surgery and at a mean of 4 and 8 months after surgery., Results: Total BL removal resulted in a significant decline in subbasal nerve density at 4 months (P = 0.007) that barely recovered to preoperative levels at 8 months (P = 0.055). With BL partially present, subbasal nerve density did not significantly change from preoperative levels. Superficial, wing, and basal epithelial cell density recovered to preoperative levels within 4 months after PTK, regardless of the presence of BL. Subepithelial keratocytes, however, were more densely distributed in corneas without BL relative to those with a partial BL present (P = 0.005), and increased anterior keratocyte reflectivity was noted in all eyes without BL and in no eye with a partial BL present., Conclusions: Subbasal nerve regeneration is delayed and subepithelial keratocyte density and reflectivity remain elevated up to 10 months after total BL removal by PTK. The results provide initial evidence for a possible role of BL in facilitating rapid stromal wound healing and an associated recovery of anterior corneal transparency and the restoration of epithelial innervation after epithelial trauma.

Purpose: To determine corneal biomechanical parameters measured with the Reichert Ocular Response Analyser (ORA) in Singaporean children, and to assess their possible correlations with refractive error and biometry., Methods: This was a cross-sectional study of 271 subjects from the Singapore Cohort Study of Risk Factors for Myopia (SCORM). Corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), and cornea-compensated intraocular pressure (IOPcc) were measured with the ORA. Spherical equivalent refraction was assessed with an autokeratorefractometer and axial length by contact ultrasound A-scan biometry. Height, weight, and blood pressure were measured., Results: The mean age of the study population was 13.97 +/- 0.89 years, the distribution of the sexes was almost equal (138 boys, 50.9%), and most were Chinese (186 subjects, 68.6%). The mean (+/-SD) CH and CRF were 11.78 +/- 1.55 (range, 6.93-16.53) and 11.81 +/- 1.71 (range, 7.83-16.83) mm Hg. CH and CRF did not vary significantly with age (P = 0.24; 0.61), sex (P = 0.21; 0.08), or race (P = 0.23; 0.36). CH and CRF did not vary with myopia status (P = 0.79; 0.83) or axial length (Pearson correlation coefficient [r] = -0.11 and -0.05, P = 0.08 and 0.40). Multivariate analyses were performed with CH, CRF, or CCT as the dependent variable and age, sex, race, weight, IOPcc, CCT, SE refraction, and corneal curvature as covariates. CH was significantly associated with IOP (regression coefficients [beta] = -0.22 [95% confidence interval = -0.27 to -0.17]), CCT (beta = 0.03 [0.02-0.03]) and corneal curvature (beta = -1.13 [-2.08 to -0.19]). CRF was significantly associated with IOP, CCT, and corneal curvature (beta = 0.08 [0.02-0.14]; 0.03 [0.03-0.04], and -1.39 [-2.54 to -0.23], respectively). The only factor that was predictive of decreased CCT was Malay or Indian race (P = 0.03 and <0.001), compared with Chinese., Conclusions: The CH and CRF values in our study on Singaporean children are slightly higher than in adult studies. CH and CRF are not associated with refractive error or axial length. Flatter corneas are associated with lower CH and CRF readings.

Purpose: To determine the impact of visual impairment and eye diseases on quality of life (QOL) in an older population of Andhra Pradesh in southern India., Methods: The World Health Organization (WHO) QOL (WHOQOL) instrument was adapted as a health-related quality of life (HRQOL) instrument for administration to adults participating in the Andhra Pradesh Eye Disease Study. Participants aged 40 years and older (n = 3702), 99.4% of the 3723 eligible, who underwent interview and detailed dilated ocular eye evaluation by trained professionals were included in this study. Psychometric properties of the HRQOL instrument were evaluated among visually impaired people. Relationships among overall QOL scores and presenting visual acuity in the better eye, specific eye diseases, and demographic variables were examined., Results: Internal consistency was high for the entire questionnaire (alpha = 0.94). Each item of the QOL scale had an adequate item-total correlation (range, 0.25-0.77) greater than 0.2. After adjusting for demographic variables and ocular disease, Subjects with blindness had significantly lower QOL scores. Subjects with glaucoma or corneal disease independent of visual acuity had lower scores than subjects without those eye diseases. Subjects with cataract or retinal disease had significantly lower scores than those without cataract or retinal disease in the model without visual acuity but not when visual acuity was added to the model., Conclusions: Decreased QOL was associated with the presence of glaucoma or corneal disease independent of visual acuity and with cataract or retinal disease as a function of visual acuity. Visual impairment from uncorrected refractive errors was not associated with decreased QOL.

Purpose: To explore changes in corneal sensitivity that develop in patients with dry eye and the relationship between sensibility and severity of the dry eye disease., Methods: Experiments were performed in 44 patients with dry eye and 42 healthy individuals. Corneal sensitivity was measured with the Belmonte noncontact gas esthesiometer. Mechanical (air jets at flow rates from 0 to 200 mL/min, reaching the corneal surface at 34 degrees C), thermal (cold or warm air at subthreshold flow rates changing corneal basal temperature +/-1 degrees C), and chemical stimuli (air containing 0% to 50% CO2 at subthreshold flow rate and temperature at the cornea of 34 degrees C) were applied to the center of the cornea to determine the sensitivity threshold for each stimulus modality. The clinical state of the ocular surface was also explored, measuring the fluorescein tear break-up time, the degree of corneal staining with fluorescein and Lissamine green, and tear production with the Schirmer test., Results: Both in control subjects and patients with dry eye, the corneal thresholds for mechanical, chemical, and thermal stimulation increased with age. Moreover, the thresholds for the three modalities of stimuli were significantly higher in patients with dry eye than in control subjects. In both groups, individual mechanical, chemical, and thermal thresholds correlated significantly. Also, high thresholds in patients with dry eye correlated with the intensity of fluorescein and Lissamine green corneal staining but not with the results of the Schirmer test., Conclusions: Patients with dry eye exhibit corneal hypoesthesia after mechanical, thermal, and chemical stimulation that appears to be related to damage to the corneal sensory innervation.

Purpose: Corneal wound healing is impaired in diabetic cornea. The purpose of this study was to examine patients with type 1 diabetes mellitus for changes in corneal morphology and to correlate corneal sensitivity, subbasal nerve morphology, and degree of polyneuropathy with each other., Methods: Forty-four eyes of 23 patients with diabetes and nine control eyes were included. Corneal sensitivity was tested with a Cochet-Bonnet esthesiometer (Luneau, Paris, France), and corneal morphology and epithelial and corneal thickness were determined by in vivo confocal microscopy. The density of subbasal nerves was evaluated by calculating the number of long subbasal nerve fiber bundles per confocal microscopic field. The degree of polyneuropathy was evaluated using the clinical part of the Michigan Neuropathy Screening Instrument (MNSI) classification, and retinopathy was evaluated using fundus photographs., Results: A reduction of long nerve fiber bundles per image was noted to have occurred already in patients with mild to moderate neuropathy, but corneal mechanical sensitivity was reduced only in patients with severe neuropathy. Compared with control subjects the corneal thickness was increased in patients with diabetes without neuropathy. The epithelium of patients with diabetes with severe neuropathy was significantly thinner than that of patients with diabetes without neuropathy., Conclusions: Confocal microscopy appears to allow early detection of beginning neuropathy, because decreases in nerve fiber bundle counts precede impairment of corneal sensitivity. Apparently, the cornea becomes thicker in a relatively early stage of diabetes but does not further change with the degree of neuropathy. A reduction in neurotrophic stimuli in severe neuropathy may induce a thin epithelium that may lead to recurrent erosions.

Purpose: To compare the relative advantages and disadvantages of four different representations of corneal power--identified as instantaneous, axial, position, and refractive--based on curvature, slope, coordinate position, and focal properties, respectively., Method: The four types of corneal power were evaluated by examining their interrelationship for 12 hypothetical corneal shapes chosen to represent the general characteristics of regular, irregular, and surgically altered corneas., Results: There is only a limited association between refractive power and the other three powers, which are based on shape properties. For corneal shapes represented by ellipsoids of low eccentricity (e), refractive power increased as a function of the distance from the reference axis, whereas axial and instantaneous powers were either constant (for e = 0) or decreased, with instantaneous power having the largest decrease. Refractive power decreased for elliptical corneal shapes with eccentricities greater than the reciprocal of the index of refraction, although always decreasing less than the axial or instantaneous power. For various corneal shapes formed by segments of circles (or a polynomial) with large differences in instantaneous power, the refractive power was more closely associated with axial than instantaneous or position powers., Conclusions: The Purkinje image measurements from videokeratograpy are most closely related to the slope-based axial power because it is slope that determines the direction of reflected rays forming the corneal image. Because of this direct connection, axial power is less sensitive to noise than is refractive, instantaneous, or position power. Present videokeratographs that report axial power provide an approximation of refractive power, but if an exact refractive power is needed it can be calculated easily. Instantaneous power provides the most sensitive measure of local curvature changes, such as those occurring in keratoconus or refractive surgery. There are unique practical applications for each of the four powers.

Corneal edema was produced by atmospheric-induced anoxia and the visual effect was assesed by conventional acuity tests and compared with contrast sensitivity measurements. For the degree of edema which this technique produced, contrast sensitivity was depressed for only high spatial frequencies and could be considered in terms of equivalent defocus. This was not the case ofr a greater degree of edema which was simulated by a diffuser with a particle size that mimics the diffraction effects from an edematous cornea. Equivalent blur was not applicable, since low spatial frequencies were also affected and the letter and contrast sensitivity tests gave radically different results. In the light of these findings, the validity of the present letter acuity evaluation of visual function for patients in which intraocular scattering is involved is questioned.

The amount of initial corneal swelling and the time course of corneal deswelling were measured after overnight wear of several types of hard and hydrogel lenses. Deswelling occurred in the right eye with the lens still on the cornea. In the left eye the lens was removed at eye opening and left off the cornea during deswelling. For lenses of equal nominal oxygen transmissibility, hard lenses initially induced greater corneal swelling than hydrogel lenses after overnight wear. The rate of deswelling during the first 15 min after hard lens wear was significantly greater than a comparable time period after hydrogel lens wear both with the lenses on and off the eye during deswelling. After the initial 15 min of eye opening, no significant difference in the deswelling rates with hard or hydrogel lenses could be shown under either deswelling condition.

One eye of each of eight subjects was exposed to gases containing oxygen concentrations of 1.0%, 2.5%, 4.9%, 7.5%, 10.1%, and 21.4% (oxygen partial pressures ranging from 8 to 158 mmHg) for 8 hr. The precorneal oxygen concentration required to avoid corneal edema for the group as a whole was 10.1% (an oxygen tension of 74 mmHg). There was considerable individual variation both in the corneal swelling response with each of the various oxygen concentrations and in the atmospheric oxygen concentration required to avoid edema: one subject required 7.5%, four subjects required 10.1%, and three subjects required 21.4% oxygen concentration. The results of this study suggest that the cornea requires higher levels of atmospheric oxygen than previously considered necessary for normal function.

This study provides evidence for an N-acetylmannosamine (manNac) receptor mediating in vivo bacterial adherence of P. aeruginosa to the scarified corneal epithelial surface. Bacteria, whether exposed to the inhibiting sugar or not, did not adhere immediately after inoculation, but required time in contact with the scarified corneal surface to adhere and adherence increased with time. Organisms were observed primarily adherent to the surface of epithelial cells lining the wound and were less frequently seen on areas of denuded stroma. Saturation of binding sites on the bacterial surface by manNac inhibited attachment of the organisms to newly exposed surface membrane receptors. In vivo protection studies showed excellent correlation with quantitative analysis of scanning electron micrographs, in that the number of adherent organisms at the corneal surface at 60 min following scarification and bacterial inoculation was decreased significantly by prior treatment of the bacteria with manNac when compared with PBS or the other monosaccharides. These data were confirmed by quantitative bacterial culture of excised corneas which had been similarly infected in vivo with PBS or manNac treated organisms.

Two pathogenic mechanisms of Pseudomonas aeruginosa corneal infections are discussed, one involving bacterial exoenzymes, the other involving polymorphonuclear leukocyte (PMN)-derived lysosomal enzymes. The objective of the present study was (1) to show the relative importance of the two mechanisms and (2) to evaluate the effect of active immunization against P. aeruginosa exoenzymes on ocular damage. Rabbits were immunized against P. aeruginosa alkaline protease (AP) or elastase (Ela) and challenged with the respective enzymes. Corneal damage was studied by light photography (LP). In another group, rabbits were immunized against AP, Ela and exotoxin A (ExoA) and challenged with P. aeruginosa strains PA01 or PA103. Corneal damage was studied with LP, light microscopy, and electron microscopy. Immunized animals were totally protected against intracorneal inoculation of P. aeruginosa proteases. Twelve hr and 24 hr after challenge with whole bacteria, immunized rabbits revealed less corneal damage than non-immunized animals. However, after 48 hr corneal damage (ie severe corneal ulceration) was comparable in both groups. The study suggests that corneal damage involving lysosomal enzymes from stimulated PMN is more important after bacterial infection than direct damage by P. aeruginosa exoenzymes.

The effect of the contact lens--cornea bearing relationship on tear pumping and corneal swelling (edema) which accompanies hydrogel lens wear was determined by monitoring corneal thickness and tear replenishment rates when the base curve (back surface curvature) was varied from 7.8 to 9.0 mm. The lens movement is dependent on the bearing relationship; however, the degree of corneal swelling and the replenishment rate of tears under the lens are independent of the bearing relationship. These results indicate that the corneal edema which accompanies gel lens wear cannot be reduced by altering the lens-cornea bearing relationship.

Insulin-depleted, normal rabbit corneal epithelium was incubated in vitro in tissue culture medium containing high concentrations of glucose (35 mM). These short-term incubations showed that the epithelium took up glucose equally whether or not insulin had been added to the medium, indicating that corneal epithelium is an insulin-insensitive tissue. Sorbitol accumulation showed that the normal corneal epithelium has a sorbitol pathway which can be activated in the presence of high intracellular glucose. The low level of sorbitol accumulation in these normal epithelia is probably not osmotically significant.

Effects of different energy levels (1.2, 2.0, 2.8, 4.0 mj) of a mode-locked Nd:YAG laser beam focused directly on the corneal endothelium were evaluated in rabbit, cat, and owl monkey. The endothelial lesion observed by specular microscopy at 10 min; 8, 16, and 24 hr; 3, 5, 7, and 21 days measured up to 0.8 mM in diameter. It showed focal destruction of Descemet's membrane and a larger area of endothelial denudation corresponding probably to the shock wave generated by the plasma. The size of the defect correlated with the amount of energy delivered. Even though healing was characterized by a phase of rapid endothelial migration during the first 24 hr, only about one-half of the defect was covered after 1 week in all animals. This lesion persisted with minimal endothelial proliferation for 3 weeks in the rabbit and for 3 months in the cat. The monkey was followed for only 1 week. Our findings indicate that the laser-tissue interaction is different from mechanical or thermal modes of injury and interferes with the specific endothelial functions in repair.

Contraction of corneal wounds has been the topic of recent speculation, particularly in reference to regression of corneal flattening following radial keratotomy. In an animal model of corneal wound fibroplasia, we offer the first demonstration of in vitro contractility by avascular corneal wound tissue. Three millimeter diameter full-thickness corneal trephine wounds were made in 17 New Zealand white rabbit eyes. The animals were killed and specimens were extracted 3-4 wk postinjury. Contractile responses of corneal wounds were measured on a microdynagauge force transducer. When exposed to serotonin, epinephrine or norepinephrine corneal wounds showed contractions reaching maximum force of 20-100 mg with a peak response obtained within 5-10 min and persisting several hours. Normal corneas did not respond to any agent. All normal iris muscle specimens contracted to acetylcholine exhibiting peak responses of 30-60 mg of force within 5 sec decaying over the following 10-20 min. This is different from corneal wounds which fail to respond to acetylcholine (P less than 0.005). These data suggest that avascular corneal wounds possess contractile properties.

The affinity of various corneal boundary surfaces, such as mucus-coated epithelium, demucinized epithelium, denuded basement membrane, and keratectomized cornea, to water and hydrophobic liquids was determined by contact angle goniometry on enucleated rabbit eyes. The mucus-coated surface and the bare stromal surface without the basement membrane were found to be more hydrophilic than the surfaces of the epithelium and the basement membrane. If at least one of the surfaces forming a joint boundary is hydrophilic, then conditions become favorable for the accumulation of water at the interface, forming a weak boundary layer that is detrimental to adhesion, due to its low shear resistance. Thus, even in a normal eye, mucus does not adhere strongly to the epithelium; when the basement membrane is damaged or absent, the epithelium does not adhere well to the stroma. External dehydrating factors such as hyperosmotic conditions favor adhesion, whereas edematic conditions have an adhesive (adhesion-decreasing) effect. Experimental ophthalmic solutions containing macromolecules at hyperosmotic concentrations may demonstrate a therapeutic effect when applied to eyes with recurrent epithelial erosion or other epithelial trauma.

Corneal touch threshold was monitored while corneal edema was experimentally induced by exposing the cornea to either an oxygen-free environment or hypotonic saline. No change in sensitivity occurred during these conditions. Contact lens wearers who were fully adapted to their lenses and did not develop corneal edema during wear showed an increase of 96% in corneal touch threshold. Refitting these subjects with an experimental contact lens which caused a 6% increase in corneal thickness did not further alter the corneal sensitivity. The decrease in corneal sensitivity accompanying contact lens wear is independent of corneal edema and is likely a result of sensory adaptation to a mechanical stimulant.

The endothelial pump and evaporation components of corneal recovery were studied in the in vivo human cornea by inducing corneal swelling with the use of hypoxia and monitoring the subsequent decrease in corneal thickness. Corneal recovery follows a nonlinear time course with the rate of recovery decreasing as the cornea thins. Following 60 micron of induced edema, recovery with the eyes open required an average of 2.5 hr to reach baseline corneal thickness, while recovery with the eyes closed took an average of 4.0 hr to reach the normal physiologic corneal swelling (17 micron). Our analysis indicates that for open eye recovery from 60 micron of swelling, the endothelial pump provides 20%, while the osmotic thinning caused by tear evaporation contributes 80% of recovery. During recovery, the rate of water evaporation from the anterior corneal surface remained relatively steady at 2.5 microliter/cm2 X hr. Comparison of measured vs calculated recovery rates during recovery with the eyes closed suggests that the endothelial pump functions at one speed and that the "pump-leak" theory of corneal hydration control is applicable for the human cornea.

Herpes simplex virus type 1 (HSV-1) ocular shedding and recurrent corneal epithelial lesions were assessed following ocular iontophoresis of 0.01% timolol at 0.8 mAmp for 8 min for 3 consecutive days in 17 rabbits latently infected with HSV-1 strain McKrae. The collection of ocular tear film for the detection of HSV-1 ocular shedding and the slit lamp biomicroscopic evaluation for HSV-1 epithelial lesions began on day 4 after the first iontophoresis and continued for 7 consecutive days. The tear film was collected on a Dacron swab with care being taken to avoid swabbing the corneal epithelium. The observed HSV-1 lesions were characterized as deep punctate lesions, dendritic lesions and geographic epithelial defects. The ratio of total days of eyes exhibiting HSV-1 epithelial lesions to the total number of observation days was 113/235 (48%). There were 46 punctate lesions, 27 dendritic lesions and 40 geographic epithelial defects. The ratio of positive swabs to total swabs was 77/235 (33%). Of the 113 positive lesion days, 65 (58%) were associated with a positive swab. Of the 77 positive swabs, 65 (84%) were associated with an epithelial lesion. Of the 122 negative lesion days, 110 (90%) were associated with a negative swab. Of the 158 negative swabs, 110 (70%) were associated with no epithelial lesions. By chi-square analysis, there was a significant association between HSV-1 swabs and HSV-1 lesions (P less than 0.001). These results demonstrate that ocular iontophoresis of timolol induces both HSV-1 ocular shedding and recurrent HSV-1 corneal epithelial lesions in rabbits latently infected with HSV-1 strain McKraw.

In order to determine which layers of the corneal stroma bear the stress of the intraocular pressure, 6.0-mm nonpenetrating trephine incisions were made centrally in one eye of each of 16 adult albino rabbits. After epithelial healing, the central corneal thickness was measured over 3 hr at 50 mmHg intraocular pressure in both eyes of the anesthetized rabbits. The animals were then killed and the uniformity and depth of trephine cut determined histologically. The mean differences in swelling rates between the cut and the opposite uncut eyes for trephine incisions of different depths were as follows: 1 +/- 2 micron/hr for 8-20% depth, 5 +/- 2 micron/hr for 21-40% depth, and 14 +/- 3 micron/hr for 41-60% depth (P less than 0.01 for all groups). These results indicate that the intraocular tension is probably distributed across all the corneal stromal lamellae rather than being borne primarily by the anterior or posterior layers.

Endothelial function may be affected by the endothelial cell loss and increased variability in cell shape and size (polymegathism) that accompany normal aging. Endothelial function can be evaluated by monitoring corneal hydration recovery following hypoxic stress. The authors compared corneal recovery and endothelial morphology between a group of younger (mean = 26.7 yr) and older (means = 65.7 yr) subjects with normal corneas. Edema (60 microns) was induced with hydrogel lenses worn with the eyes closed. Following lens removal, the decrease in corneal thickness was monitored for 4 hr with one eye open while the contralateral eye remained closed. For both age groups, corneal recovery followed a non-linear time course. The open eye required 2.5 hr and 3.0 hr to return to baseline for the younger and older age groups, respectively. Recovery during eye closure took 3.5 hr to reach the normal closed eye level for the younger subjects and was not complete at 4 hr for the older subjects. Recovery rates were significantly slower for the older vs younger subjects during the first 2 hr of closed eye recovery, 10.5 vs 15.0 microns/hr, and for the initial 1 hr of open eye recovery, 26.5 vs 35.6 microns/hr. For both age groups combined, the rate of recovery was negatively correlated with the coefficient of variation in cell area, r = -0.62 and -0.69 (P less than 0.01), for both closed and open eye recovery, respectively. When each morphological characteristic was isolated, the only significant correlation found was between the coefficient of variation in cell area and the rate of recovery during eye closure, r = -0.66 (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The ocular characteristics and responses were examined in patients who had undergone extracapsular cataract extraction (ECCE), intracapsular cataract extraction (ICCE) and penetrating keratoplasty (PKP) in one eye only. In each of the three groups, corneal sensitivity (the inverse of corneal touch threshold), oxygen uptake rate, and endothelial cell density were lower in the operated eye than in the normal healthy fellow eye. For the subjects as a whole, the differences in ocular characteristics between the two eyes were proportional to the angular size of the corneal incision, with ECCE patients (33 degrees incision) showing the least differences and PKP patients (360 degrees incision) showing the greatest differences. Five patients from the ICCE group were subjected to an osmotic stress test. There was no statistically significant difference in the corneal swelling response between the operated eye (5.1%) and the unoperated eye (4.7%), indicating that surgically induced scar tissue does not restrict the swelling properties of the cornea. When subjected to a hypoxic stress test, all three groups manifested less corneal edema in the operated eye (ECCE -0.7%, ICCE -4.0%, and PKP -3.3%). The reduction in hypoxic corneal swelling could not be attributed to removal of the crystalline lens since a similar reduction was seen in the PKP group who had phakic eyes. The corneal swelling response correlated inversely with the corneal touch threshold and directly with epithelial oxygen uptake, but did not correlate with endothelial cell density.(ABSTRACT TRUNCATED AT 250 WORDS)

An organ culture system has been developed to study the adherence of Pseudomonas aeruginosa to unwounded corneas and to corneas healing after a 3 mm central epithelial debridement. The Pseudomonas strain was isolated from a human corneal ulcer; suspensions containing 1 X 10(8) colony-forming units/ml (CFU/ml) of bacteria were incubated with the corneas for the last 30 min of the 18 hr culture period. The distribution pattern and number of adherent bacteria on the ocular surface were determined by morphometric analysis of scanning electron micrographs. Few bacteria (25 +/- 15/mm2) adhered to the apical cells of unwounded corneas. There was a definite region-specific distribution of adherent bacteria on healing corneas. There was a definite region-specific distribution of adherent bacteria on healing corneas. Most bacteria were found on the denuded basal lamina in front of the leading edge of the migrating epithelium (360,700 +/- 49,000/mm2). Appreciable but lower numbers adhered to the apical membrane of leading-edge cells (37,700 +/- 6,100/mm2) and to the central portion of the denuded basal lamina (28,800 +/- 10,700/mm2). No bacteria were found adherent to the apical cells of the stratified epithelium behind the leading edge of the epithelium migrating to cover the wound. A similar region-specific distribution of adherent bacteria was found when corneas were inverted in the bacterial suspension and when corneas were incubated in the bacterial suspension for 15 rather than 30 min. Corneas preincubated with the lectin, succinyl-concanavalin A, showed significantly decreased bacterial adherence, indicating a possible role for mannose moieties of wound surface glycoconjugates in bacterial adherence.

The presence of a layer of abnormal material in Descemet's membrane in eight keratoplasty specimens served as a marker to determine whether Chandler's syndrome, Essential Iris Atrophy, and the Cogan-Reese syndrome are congenital or acquired conditions. In all eight cases of the ICE syndrome, a pattern of membrane deposition was observed, which typifies acquired disorders: a completely normal prenatal layer and both normal and abnormal portions of the postnatal layer. The thickness of the membrane deposited before the onset of abnormal secretion was used to estimate a time span for possible ages at which abnormal secretion began. The estimated age intervals for all diseased specimens had their lower limits in the postnatal period. Thus, these results led us to the conclusion that abnormal Descemet's membrane first appeared in postnatal life, years before clinical recognition of disease. The possibility of a viral etiology for this unilateral endotheliopathy resulting in an altered Descemet's membrane is discussed.

Visual function was assessed by classic acuity measures as well as contrast thresholds over a wide spatial frequency range for subjects with experimentally induced corneal distortion and induced corneal edema. These results were compared with similar results for patients with uniocular keratoconus, bilateral keratoconus, and allied corneal pathology. Distortion and edema were found to produce characteristically different types of contrast attenuation at threshold (amplitude) and have quite different suprathreshold abnormalities (phase) for objects within the resolution limit and therefore could form the basis of a useful functional classification of the visual degradation from corneal pathology.