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Purpose: To evaluate the agreement of central corneal thickness (CCT) measurement between Scheimpflug imaging and ultrasound (U/S) pachymetry in keratoconic eyes, and investigate factors that affect the agreement., Methods: This post hoc analysis within a prospective, observational non-randomised study preformed at the Kensington Eye Institute, Toronto, Ontario, Canada, included crosslinking candidates with progressive keratoconus (KC). Main outcome measures were the agreement of CCT measurement between Scheimpflug imaging (Pentacam Oculus, Wetzlar, Germany) and U/S pachymetry (PachPen 24-5100, Accutome Inc., Malvern, Pennsylvania, USA), and factors that affect the agreement., Results: A total of 794 keratoconic eyes of 456 subjects with a mean age of 27.6±8.0 years (69.7% males and 49.6% right eyes) were included. Agreement between devices was moderate (intraclass correlation coefficient: 74.9%, Bland-Altman limits of agreement: -48.5 μm to +62.5 μm). In a multivariable analysis, cone decentration (p<0.001, coefficient +10.13 [+6.73 to +13.53 95% CIs]) and Kmax (p<0.001, coefficient +0.68 [+0.46 to +0.90 95% CIs]) were significantly associated (both clinically and statistically) with the level of agreement between the devices; the discrepancy in CCT between the devices increased on average by 10.13 μm for every mm of cone decentration, and by 6.8 μm for every 10D of Kmax. Age, corneal astigmatism and spherical equivalent were statistically but not clinically significant factors affecting agreement., Conclusion: The agreement of CCT measurement between Scheimpflug imaging and U/S pachymetry in KC was moderate. To ensure the safety of crosslinking in keratoconic corneas, Scheimpflug and U/S CCT measurements should not be used interchangeably, especially in steep corneas and corneas with decentred cones., Competing Interests: Competing interests: MM is a paid consultant for Eye Yon Medical and Lapidot Medical. CC has received support from Alcon Laboratories Inc, Allergan, Bausch & Lomb, Santen, Shire, Tearlab, Labtician Thea, and Johnson & Johnson. AS has been a paid consultant for Abbott Medical Optics, AbbVie, Alcon Laboratories Inc, Allergan, Bausch & Lomb, Santen Inc, Shire, Acqueous, and Labtician Thea. DR has received support from Alcon Laboratories Inc and Johnson & Johnson. TR has been a paid consultant for Alcon Laboratories Inc, Johnson & Johnson, and AbbVie., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Significance: Cytokine and protease analysis revealed relative changes in the post-lens tear film of scleral lenses with low and high limbal clearances. Results from this study indicate that midperipheral lens fit is an important fitting feature that can impact the inflammatory response of a keratoconic eye., Purpose: The purpose of this study was to investigate changes in levels of inflammatory mediators in the post-lens tear film of keratoconic scleral lens wearers with varying limbal clearance designs., Methods: Twenty-two keratoconic eyes were fitted with two sets of scleral lenses that were consistent in lens diameter and central sagittal depth but varied in limbal clearance by approximately 50 μm. Lenses were worn in a randomly assigned order for a 2-week period each. At each follow-up visit, immediately after lens removal, tear samples were collected with a microcapillary tube (10 μL, 0.5 mm in diameter) from the bowl of the inverted scleral lens. Tear cytokine and protease analysis was performed using a multiplex electrochemiluminescent array (Meso Scale Discovery, Rockville, MD) instrument. Levels of interleukins 1, 6, and 8; tumor necrosis factor α; and matrix metalloproteinases 1 and 9 were compared and analyzed., Results: Levels of interleukin 1β, tumor necrosis factor α, and matrix metalloproteinase 1 increased with high limbal clearance (P = .01, .006, and .02, respectively). No change in interleukins 6 and 8 levels was found (P > .05). A decrease in matrix metalloproteinase 9 was noted in post-lens tear film of scleral lenses with high limbal clearance (P = .10)., Discussion: Relative changes in the cytokine and protease levels were found when comparing low and high limbal clearance, indicating that the midperipheral lens fit is an important feature that can impact the inflammatory response of the keratoconic eye., Competing Interests: Conflict of Interest Disclosure: None of the authors have reported a financial conflict of interest., (Copyright © 2021 American Academy of Optometry.)

Purpose: The purpose of this study was to characterize the central epithelial thickness (CET) of penetrating keratoplasty corneal specimens obtained from patients with keratoconus (KC) and correlate the histological patterns with their clinical history., Methods: Ex vivo histological imaging was performed to measure CET and total corneal thickness (TCT) in 56 patients with KC. Microscopic slides from penetrating keratoplasty corneal specimens, stained with hematoxylin and eosin were evaluated using bright field microscopy. CET and TCT were measured, and morphological features were studied. Clinical history regarding duration of KC prior to surgery and length of and tolerance to contact lens wear were compared and analyzed., Results: The microscopic slides of all patients available for follow up (n=48) were analyzed and CET and TCT were measured. The histological evaluation revealed 3 distinctive epithelial patterns. Pattern 1 with central hypertrophic and hydropic changes (n=19) measured 70.89±25.88μm in CET and 308.63±100.74μm in TCT; Pattern 2 (n=14) had not changed, similar to normal epithelium CET and TCT measuring 36.5±7.02μm and 260.14±87.93μm respectively. Pattern 3 (n=15) demonstrated thinner central epithelium characterized by atrophy and focal hydropic changes measuring 19.93±4.60μm and 268.00±79.39μm in CET and TCT respectively (all p<0.0001). The presence of Pattern 2 characterized by similar to normal CET was correlated with the duration of the condition (R=0.600, p=0.030). There was a significant difference in the length of CL wear comparing those with patterns 1 and 2 versus 3 (least no. of CL years) (p=0.05 and p=0.33 respectivelly)., Conclusions: Patients with advanced disease have various central corneal epithelial changes detected with histology. Although each central epithelial pattern type was distinctive comparing the 3 patterns, there was no correlation with years of CL wear but only with the duration of the condition., (Copyright © 2020 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Significance: This study evaluates how limbal clearance (LC) may impact the clinical performance of scleral lenses based on subjective response on comfort and ocular responses. Limbal zone designs in scleral lenses might affect the integrity of the limbal epithelial tissue as a result of a combined hypoxic and compression-related etiology., Purpose: This study aimed to investigate the clinical performance and ocular and subjective responses to the wear of scleral lenses having varying LC., Methods: Lenses with varying LC with a difference of 50 μm were fitted on and compared among keratoconic participants. The lenses were worn during a 2-week period. Visual analog scales concerning subjective comfort were completed. Ocular surface findings including hyperemia, limbal staining, and corneal swelling were compared., Results: Participants reported greater comfort achieved with high LC. No difference in limbal and bulbar hyperemia was found (P > .05). Corneal response to scleral lens wear with both low and high LCs seems to result in similar perilimbal staining and negative corneal staining. An increase in corneal pachymetric values was noted at the central and peripheral cornea, with no difference between low- and high-LC lenses (all, P < .05). Quadrant-specific analysis indicated that all meridians at both 6 and 8 mm were increased for the low-LC lenses (all, P < .05) and only the temporal region for the high-LC lenses (P = .02)., Conclusions: Limbal clearance may play an important role in subjective performance in scleral lenses but does not impact the degree of hyperemia in either the limbal or bulbar region. Although low LC might result in more compression-related changes to ocular surface, high LC is associated with greater comfort and greater edematous changes. Limbal zone designs in scleral lenses might affect the integrity of the limbal epithelial tissue as a result of a combined hypoxic and compression-related etiology.

Significance: With the increase in the use of scleral contact lenses among practitioners, questions regarding lens settling are gradually gaining attention. This is because current studies support the notion that scleral lenses settle back over time. More research is needed to understand the exact cause and the factors that underpin such phenomenon., Purpose: The present study aims to assess the effect of time on topographic corneal clearance of three scleral contact lenses of varying sagittal depths., Methods: Three scleral contact lenses were fitted to 20 subjects with previous diagnosis of keratoconus (n = 18) or pellucid marginal degeneration (n = 2). The fit was based on corneal sagittal height measured with the Visante optical coherence tomographer (OCT) at 15 mm along the horizontal meridian. To select an appropriate lens from the diagnostic lens set, values of 325 μm (lens 1), 375 μm (lens 2), and 425 μm (lens 3) were randomly added in sequence to the corneal sagittal height. Subjects wore each lens for 1 hour. Corneal clearance was measured at 10-minute intervals for 1 hour using a custom ultra-long OCT. To assess change in clearance, central point and two mid-peripheral points (+3 mm and -3 mm) along an 8-mm chord were measured by taking differences at each time point up to 1 hour. Measurements were repeated for the two other lenses., Results: Mean central corneal clearance loss for all three lenses was 33.83 ± 48.40 μm. This was 26 ± 27 μm (13 ± 14 μm, +3 mm; 34 ± 37 μm, -3 mm), lens 1; 35 ± 59 μm (38 ± 61 μm, +3 mm; 52 ± 69 μm, -3 mm), lens 2; and 41 ± 54 μm (33 ± 26 μm, +3 mm; 52 ± 48 μm, -3 mm), lens 3, respectively. There was no significant difference (P = 0.06) at central and other locations for lens 1 (location and over time). There were significant differences for both lenses 2 and 3 (P < .001, P = .01, respectively) for all three locations and over time., Conclusions: There is a likelihood of clearance loss after 1 hour of lens wear. This varies between subjects, initial lens-fit relationship, and over time.

Purpose: To assess the repeatability and reproducibility of Visante™ OCT and Oculus Pentacam HR® in measuring central (CCT) and topographic corneal thickness (TCT) along the principle meridians in keratoconus (KC) corneae., Method: Twenty participants diagnosed with KC were recruited. There were two study visits. On the first study visit, two repeated corneal thickness measurements were obtained with each instrument. Measurements were repeated at least 48hrs later in the same order. TCT were recorded in the 90, 180, 45 and 135 meridians at 1mm intervals across 8mm chord., Results: Mean CCT for Visante™ OCT was 484.97±43.14μm (range: 484.84-486.09) and Oculus Pentacam HR® was 478.86±45.31μm (range: 477.20-480.53). No significant difference in TCT between the two visits (p=0.54) and measurements (p=0.63) for Visante™ OCT. For Oculus Pentacam HR®, no significant difference was found for each visit (p=0.18) but differences existed in the measurements outside of the central region (p=0.001). Tukey post-hoc analysis shows the differences (p˂0.05) were found in the +1 and +4 (supero-temporal) locations in the 135 meridian. Significant differences were found comparing the two instruments, (p<0.05). Bland Altman plots were used to demonstrate the differences between the two instruments and indicate their limits of agreement., Conclusion: Both instruments gave repeatable measurements as no significant differences were found in most locations in all meridians. Comparing the two instruments, they were not reproducible in all locations., (Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.)

Keratoconus is a bilateral degenerative disease characterized by a non-inflammatory, progressive central corneal ectasia (typically asymmetric) and decreased vision. In its early stages it may be managed with spectacles and soft contact lenses but more commonly it is managed with rigid contact lenses. In advanced stages, when contact lenses can no longer be fit, have become intolerable, or corneal damage is severe, a penetrating keratoplasty is commonly performed. Alternative surgical techniques, such as the use of intra-stromal corneal ring segments (INTACS) have been developed to try and improve the fit of rigid contact lenses in keratoconic patients and avoid penetrating keratoplasties. This case report follows through the fitting of rigid contact lenses in an advanced keratoconic cornea after an INTACS procedure and discusses clinical findings, treatment options, and the use of mini-scleral and scleral lens designs as they relate to the challenges encountered in managing such a patient. Mini-scleral and scleral lenses are relatively easy to fit, and can be of benefit to many patients, including advanced keratoconic patients, post-INTAC patients and post-penetrating keratoplasty patients., (2011 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.)