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Purpose: Establishing the reliability of a new method to check the mean retinal and choroidal reflectivity and using it to find retinal and choroid changes in amblyopia., Methods: Design: Retrospective case-control. Population: 28 subjects of which 10 were healthy controls (20 eyes): 8 with refractive errors, 1 with strabismus, and 1 with both. 18 patients with unilateral amblyopia included: 7 anisometropic, 6 isoametropic, 1 strabismic, and 4 combined. Mean participants' age: 13.77 years ± 10.28. Observation procedures: SD-OCT and ImageJ. Main outcome measure: mean reflectivity of retinal and choroid layers. Amblyopic, fellow, and healthy eyes were compared., Results: The method of measuring reflectivity is good to excellent reliability for all regions of interest except the fourth. The mean reflectivity of the choriocapillaris and Sattler's layer in amblyopic eyes were significantly lower than in healthy eyes (p = 0.003 and p = 0.008 respectively). The RNFL reflectivity was lower than that of fellow eyes (p = 0.025). Post-hoc pairwise comparisons showed statistically significant differences between amblyopic and healthy eyes for choriocapillaris (p = 0.018) and Sattler's (p = 0.035), and between amblyopic and fellow eyes for RNFL (p = 0.039)., Conclusion: A decrease in reflectivity of the choriocapillaris and Sattler's in amblyopic compared to healthy eyes, and a decrease in reflectivity of the RNFL in the amblyopic compared to fellow eyes, indicate that the pathophysiology is partly peripheral and might be bilateral., Competing Interests: The authors have declared that no competing interests exist.

. To investigate the effect of anisometropic and strabismic amblyopia on the nerve fiber layer thickness. This cross-sectional study was done on 54 amblyopic subjects, equally in both strabismic and anisometropic groups. The thickness otonerve fiber layer measured in superior, inferior, nasal, temporal quadrants and as a whole in both eyes of both groups. The means of thickness were compared in amblyopic and sound eyes. In strabismus group, the average nerve fiber layer thickness of the sound eye , in superior, inferior, nasal and temporal quadrants and as a whole were 113.23±14, 117.37±25, 68.96±6, 69.55±14 and 93.40±8 microns respectively. In amblyopic eyes of the same group, these measurements were 103.11±18, 67.74±11, and 69.59±16 and 89.59±12 microns in superior, inferior, nasal, temporal quadrants and as whole respectively. In anisometropic groups, the sound eye measurements were as 130.96±22, 129.07±29, 80.62±12, and 83.88±20 and 107.7±13 microns in superior, inferior, nasal and temporal quadrants and as a whole orderly. In amblyopic eyes of this group the mean thicknesses were 115.63±29, 133.15±25, 78.8±15, 80.2±16 and 109.17±21 microns in superior, inferior, nasal, temporal quadrants and as a whole respectively. Statistically, there were no significant differences between amblyopic and sound eyes (P>0.5). Our study did not support any significant change in a nerve fiber layer thickness of amblyopic patients; however, decreased thickness in superior and nasal quadrants of strabismic amblyopia and except inferior quadrant and as a whole. These measurements may be a clue for management and prognosis of amblyopia in old age.

Purpose: In order to better understand whether white matter structural deficits are present in strabismic amblyopia, we performed a survey of the tissue properties of 28 major white matter tracts using diffusion and quantitative magnetic resonance imaging approaches., Methods: We used diffusion-based tensor modeling and a new quantitative T1 protocol to measure fractional anisotropy (FA), mean diffusivity (MD), and myelin-sensitive T1 values. We surveyed tracts in the occipital lobe, including the vertical occipital fasciculus (VOF)-a newly rediscovered tract that bridges dorsal and ventral areas of the occipital lobe, as well as tracts across the rest of the brain., Results: Adults with long-standing strabismic amblyopia show tract-specific elevations in MD. We rank-ordered the tracts on the basis of their MD effect-size. The four most affected tracts were the anterior frontal corpus callosum (ACC), the right VOF, the left inferior longitudinal fasciculus (ILF) and the left optic radiation., Conclusions: The results suggest that most white matter tissue properties are relatively robust to the early visual insult caused by strabismus. However, strabismic amblyopia does affect MD, not only in occipital tracts, such as the VOF and optic radiation, but also in long range association tracts connecting visual cortex to the frontal and temporal lobes (ILF) and connecting the two hemispheres (ACC).

To probe the mechanism of visual suppression, we have raised macaques with strabismus by disinserting the medial rectus muscle in each eye at 1 mo of age. Typically, this operation produces a comitant, alternating exotropia with normal acuity in each eye. Here we describe an unusual occurrence: the development of severe amblyopia in one eye of a monkey after induction of exotropia. Shortly after surgery, the animal demonstrated a strong fixation preference for the left eye, with apparent suppression of the right eye. Later, behavioral testing showed inability to track or to saccade to targets with the right eye. With the left eye occluded, the animal demonstrated no visually guided behavior. Optokinetic nystagmus was absent in the right eye. Metabolic activity in striate cortex was assessed by processing the tissue for cytochrome oxidase (CO). Amblyopia caused loss of CO in one eye's rows of patches, presumably those serving the blind eye. Layers 4A and 4B showed columns of reduced CO, in register with pale rows of patches in layer 2/3. Layers 4C, 5, and 6 also showed columns of CO activity, but remarkably, comparison with more superficial layers showed a reversal in contrast. In other words, pale CO staining in layers 2/3, 4A, and 4B was aligned with dark CO staining in layers 4C, 5, and 6. No experimental intervention or deprivation paradigm has been reported previously to produce opposite effects on metabolic activity in layers 2/3, 4A, and 4B vs. layers 4C, 5, and 6 within a given eye's columns., (Copyright © 2015 the American Physiological Society.)

Objective: To offer a clue for the etiology of amblyopia by systematically comparing the macular thickness measured by optical coherence tomography (OCT) between the amblyopic eye and the fellow normal eye in patients with unilateral amblyopia., Methods: Databases including Wanfang, PubMed and others were searched, and data were extracted after quality assessment, then the Meta analysis was performed by the RevMan 5.02 software., Results: Four studies using the time-domain OCT (TD-OCT) were enrolled in the analysis and all those were anisometropic amblyopic patients. The only one study showed that the foveal minimum thickness is thicker in the amblyopic eyes than the fellow ones (P = 0.045). The meta analysis indicated the amblyopic eyes were 6.82 µm (P < 0.05, 95% CI: 2.81-10.83) thicker in the fovea (1 mm diameter region ). Five trials using the spectral-domain OCT (SD-OCT) were included in the analysis. It showed no significant difference in the foveal minimum thickness between amblyopic and fellow eyes. Also, no significant difference were detected in either anisometropic or strabismic subgroup (P = 0.50). Amblyopic eyes were 7.38 µm thicker in the fovea (1 mm diameter region) (P < 0.05, 95% CI: 3.13 -11.63) and significant difference in the anisometropic subgroup while no significant difference in the strabismic subgroup were detected., Conclusions: The macular fovea is thicker in the amblyopic eyes than the fellow ones by the use of OCT, so it is effective to measure the macular thickness of amblyopia in searching evidence for the etiology of amblyopia.

Purpose: To study macular morphology in amblyopic eyes using high-definition spectral domain optical coherence tomography (SD-OCT) and to compare the findings with fellow eyes., Methods: This was a prospective institutional study of patients ≥6 years of age with unilateral amblyopia. Enhanced high-definition single line macular scans of amblyopic eyes were obtained using SD-OCT and compared with fellow eyes. Scans were evaluated qualitatively for structural differences. Central foveal thickness was measured and areas of the different retinal layers were computed within 500 µm from the foveal centre nasally and temporally., Results: Forty-five patients with unilateral amblyopia were included: 25 with strabismic and 20 with anisometropic amblyopia with a mean age of 24.8 years. Qualitatively, the bulge in the inner segment/outer segment junction of the central fovea was noted to be attenuated or absent in 60% of amblyopic eyes compared with 29% of normal eyes, p=0.02. Also, amblyopic eyes demonstrated a shallow foveal pit compared with normal fellow eyes. Mean foveal thickness was significantly increased in amblyopic (228.56 µm) versus fellow eyes (221.72 µm), p=0.03. Upon exploring different retinal layers, the temporal inner nuclear layer area was increased (p=0.04) while the outer nuclear layer area was decreased (p=0.04) in amblyopic eyes compared with fellow eyes., Conclusions: Using enhanced high-definition SD-OCT, amblyopic eyes demonstrated qualitative and quantitative differences in macular features, possibly representing signs of immaturity compared with normal fellow eyes.

Purpose: To elucidate the different neuromechanisms of subjects with strabismic and anisometropic amblyopia compared with normal vision subjects using blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) and pattern-reversal visual evoked potential (PR-VEP)., Methods: Fifty-three subjects, age range seven to 12 years, diagnosed with strabismic amblyopia (17 cases), anisometropic amblyopia (20 cases), and normal vision (16 cases), were examined using the BOLD-fMRI and PR-VEP of UTAS-E3000 techniques. Cortical activation by binocular viewing of reversal checkerboard patterns was examined in terms of the calcarine region of interest (ROI)-based and spatial frequency-dependent analysis. The correlation of cortical activation in fMRI and the P(100) amplitude in VEP were analyzed using the SPSS 12.0 software package., Results: In the BOLD-fMRI procedure, reduced areas and decreased activation levels were found in Brodmann area (BA) 17 and other extrastriate areas in subjects with amblyopia compared with the normal vision group. In general, the reduced areas mainly resided in the striate visual cortex in subjects with anisometropic amblyopia. In subjects with strabismic amblyopia, a more significant cortical impairment was found in bilateral BA 18 and BA 19 than that in subjects with anisometropic amblyopia. The activation by high-spatial-frequency stimuli was reduced in bilateral BA 18 and 19 as well as BA 17 in subjects with anisometropic amblyopia, whereas the activation was mainly reduced in BA 18 and BA 19 in subjects with strabismic amblyopia. These findings were further confirmed by the ROI-based analysis of BA 17. During spatial frequency-dependent VEP detection, subjects with anisometropic amblyopia had reduced sensitivity for high spatial frequency compared to subjects with strabismic amblyopia. The cortical activation in fMRI with the calcarine ROI-based analysis of BA 17 was significantly correlated with the P(100) amplitude in VEP recording., Conclusions: This study suggested that different types of amblyopia had different cortical responses and combinations of spatial frequency-dependent BOLD-fMRI with PR-VEP could differentiate among various kinds of amblyopia according to the different cortical responses. This study can supply new methods for amblyopia neurology study.

Background/aims: To study peripapillary retinal nerve fibre layer (RNFL) and macular thickness in amblyopia using high-definition spectral-domain optical coherence tomography (SD-OCT) and to compare the results with available literature using the time-domain modality., Methods: This was a prospective institutional study of patients ≥ 6 years of age with unilateral amblyopia (strabismic or anisometropic) and non-amblyopic anisometropia. RNFL and macular thicknesses were measured using SD-OCT and compared between fellow eyes., Results: The mean age was 20 (± 12) years; 45 patients had amblyopia: 14 strabismic and 31 anisometropic. 20 patients had non-amblyopic anisometropia. The mean macular thickness was significantly increased in the amblyopic (273.8 μm) vs fellow eyes (257.9 μm), p=0.001. This difference remained significant in the anisometropic group (p=0.002) but not the strabismic group. The mean RNFL thickness was similar in amblyopic (95.4 μm) and fellow eyes (94.0 μm). Similar results were obtained regardless of the level of visual acuity, age or refractive error. In the control group of non-amblyopic anisometropia, the interocular difference did not reach statistical significance., Conclusions: Central macular thickness was significantly increased in anisometropic amblyopia using SD-OCT. Anisometropia alone did not produce such a difference, which points to a possible correlation between amblyopia and the development of the retinal layers.

Purpose: To identify the long term clinical course of amblyopia and strabismus that developed secondary to a monocular corneal opacity following suspected epidemic keratoconjunctivitis (EKC) in infancy., Methods: This was a retrospective study analyzing the medical records of seven patients, treated in our clinic, who were followed for more than five years., Results: Four patients in our clinic underwent a corneal ulcer treatment following suspected EKC. Each developed a monocular corneal opacity. Three patients with a chief complaint of corneal opacity were transferred to our clinic from other clinics. These patients had documented histories of treatment for EKC in infancy. All patients were treated with early occlusion therapy, but amblyopia persisted in four patients. Furthermore, all patients had strabismus and showed a significant reduction of stereoscopic vision., Conclusions: Although infants with EKC are not always cooperative, slit lamp examination should be performed as early as possible, and appropriate medical treatment should be performed, thus reducing the development of corneal opacity. Careful follow up should be regularly performed, and the occurrence of amblyopia or strabismus should be verified at an early stage using visual acuity or ocular alignment examination. Ophthalmologic treatments, including active occlusion therapy, should also be pursued.

Purpose: To determine whether retinal nerve fiber layer thickness (RNFLT), macular thickness, foveal volume, macular sensitivity, and fixation in patients with amblyopia differ between the amblyopic eye and the fellow eye., Methods: Optical coherence tomography (OCT) and microperimetry (MP-1) were used to evaluate patients with unilateral amblyopia. Patients were divided into 2 groups, those with strabismic amblyopia and those with refractive amblyopia. OCT maps were used to calculate foveal volume, macular thickness, and RNFLT; MP-1 was used to determine macular sensitivity and fixation., Results: A total of 30 patients were included (13 males; mean age 19.7 years [range, 10-38 years]), 15 in each group. Mean best-corrected visual acuity was 20/35 (range, 20/50 to 20/32) in the amblyopic eye and 20/21 (range, 20/20 to 20/25) in the fellow eye. In both groups, mean foveal volume and RNFLT did not differ significantly between eyes. Only macular thickness in the strabismic group differed significantly between the amblyopic and fellow eyes (P = 0.03). Macular sensitivity was significantly greater in the fellow eye in both groups (strabismic group, P = 0.002; refractive group, P = 0.013), whereas fixation did not change significantly between the amblyopic and fellow eye. RNFLT and macular sensitivity was found to be significantly correlated (strabismic group, r = 0.84, P = 0.002; refractive group, r = 0.66, P = 0.02)., Conclusions: Our data suggest that although RNFLT does not vary between eyes, macular sensitivity is reduced in patients with amblyopia., (Copyright © 2011 American Association for Pediatric Ophthalmology and Strabismus. Published by Mosby, Inc. All rights reserved.)

Objective: To study the neural mechanism of visual cortical deficits between anisometropic and strabismic amblyopia comparatively by BOLD-fMRI retinotopic mapping., Methods: Ten anisometropic amblyopes, 10 strabismic amblyopes and 9 normal subjects underwent fMRI with retinotopic mapping and luminous spots stimuli (spatial frequency: 6 cpd, contrast: 0.5). 1.5T MRI system was used to obtain functional images of visual cortex. Responses in primary and secondary visual cortex were compared among the dominant (normal subject group), anisometropic and strabismic amblyopic eyes by one-way ANOVA, successively analyzed by paired-samples t test between amblyopic eyes and fellow fixing eyes (anisometropic and strabismic amblyopia group respectively). Their fMRI deficits of amblyopes were analyzed regressively in two amblyopia groups respectively., Results: The result of one-way ANOVA showed significantly a lower activation (average T value) in V1, V2, V3, Vp and V7 visual areas (P < 0.05, P values 0.018, 0.007, 0.002, 0.000, 0.025 respectively) between anisometropic amblyopia and normal group. This was in accordance with the result of paired-samples t test between amblyopic eyes and fellow fixing eyes in anisometropic amblyopia group (P < 0.05, P values 0.035, 0.007, 0.020, 0.009, 0.023 respectively). Statistical difference was found in V1, V2 and Vp areas between strabismic amblyopia and normal group (P < 0.05, P values 0.010, 0.007 & 0.003 respectively). The paired-samples t test in strabismic amblyopia group showed statistical difference only in V2, Vp areas (P < 0.05, P values 0.026 and 0. 009 respectively. ). So the two results were discordant. Between the two amblyopic groups, there was no statistical difference (P > 0.05) except in V7 area (P < 0.05, P value = 0.048). There was no causal relation between the primary visual cortical deficits and the secondary cortex in amblyopia (P > 0.05)., Conclusion: Anisometropic amblyopia and strabismic amblyopia both have functional deficits in the primary and secondary visual cortex. The neural mechanism of secondary visual cortical deficits may be more complex than decreased cortex activation induced by the deficit of primary cortex. In the primary cortex, strabismic amblyopia and anisometropic amblyopia have neuronal deficits and/or abnormal interaction. In addition, strabismic amblyopia may also have suppressive influences of the fixing eyes upon the amblyopic eyes. Anisometropic amblyopia has the neural undersampling at a high spatial frequency in the secondary visual cortex as compared to amblyopic amblyopia.

Purpose: Arborisation of retinal vessels might be influenced by the physiological activity of the retina. It seems that the pattern of retinal vessels is an obvious object for fractal analysis. The fractal dimension of normal retinas was therefore used by us as a control value for comparison with the values collected from patients with amblyopia in one eye connected with strabismus and normal vision in the other., Methods: The 'box-counting method' was used for calculation of self-similarity dimension in 54 control patients, i.e. comparing 54 left retinas with 54 right ones. Statistical analysis was performed for these groups. This value was therefore used as a control for comparison with the values of fractal dimensions measured in patients with amblyopia connected with strabismus in one eye and normal vision in the other. The retinas of 30 patients with strabismus in one eye and of 1 patient with strabismus in both eyes were analysed., Results: The measurements performed on digitised photos of the retinas of these patients proved statistically significant differences between the control group and the fractal dimensions for the arborisation of retinal vessels in the eyes of patients with normal vision as well as differences in comparison with the retinas of functionally disabled eyes with defective vision connected with strabismus., Conclusion: The final conclusion is not obvious. It seems that normal vision has a statistically confirmed influence on the development of retinal vessels. Defective vision connected with strabismus is disturbing the process of arborisation of the retinal vessels. The retinal vessels of the patient eyes with normal vision differ from the normal pattern as defined by fractal dimensions of control eyes., ((c) 2009 S. Karger AG, Basel.)

Purpose: To compare the thickness of the retinal nerve fiber layer (RNFL) and the macular volume and of normal and amblyopic eyes between children and adults who had strabismic or anisometropic amblyopia., Patients and Methods: Patients with unilateral amblyopia were consecutively included from June 2006 to June 2007. The macular volume and the RNFL thickness were measured using OCT and compared depending on the type of amblyopia, either strabismic or anisometropic, and the age of the patients, either children (3-10 years old) or adults (18 years old or older)., Results: Fifty-six patients were included. In the child group (n=27), there was no significant difference in RNFL thickness and macular volume between amblyopic and normal eyes in both anisometropic and strabismic amblyopia. In the adult group (n=29), the RNFL was statistically thicker in amblyopic eyes only in the subgroup of anisometropic amblyopia (114+/-10.3mum in the amblyopic eyes versus 103+/-9.8mum in the normal eyes, p=0.02). No difference was found in RNFL thickness and macular volume in strabismic amblyopia. When anisometropic amblyopic eyes in children were compared to those of adults, the spherical equivalence was more positive (p=0.03) and RNFL was thicker (p=0.02) in the adult group, whereas visual acuity was not significantly different between the two groups. In strabismic amblyopia, no difference was found in spherical equivalence, RNFL thickness, and macular volume, whereas visual acuity was better in children's amblyopic eyes as compared to those of adults (p=0.05)., Conclusion: The difference in RNFL thickness is related to the difference of refraction between normal and amblyopic eyes, and between children and adults, independently of visual acuity and the mechanism of amblyopia.

Purpose: To determine whether retinal nerve fiber layer thickness (RNFLT), macular thickness (MT), and foveal volume (FV) in patients with unilateral amblyopia differ between the amblyopic and the sound eye., Methods: A Humphrey-Zeiss Stratus (OCT3) with software 4.0.3.1 was used to evaluate 40 patients (17 male, 23 female; mean age, 15.2 years; range, 5-56 years) with unilateral amblyopia. Patients were divided into 2 groups: 20 strabismic and 20 anisometropic. Maps of macular thickness and RNFL thickness (3.46) created by the use of optical coherence tomography were applied to calculate FV and MT and RNFLT., Results: Mean best-corrected visual acuity was +0.3 LogMAR (range, +0.2 to +1.0) in the amblyopic eye. Mean RNFL thickness was not significantly different between eyes in either group. In strabismic amblyopia, mean MT and FV were 5% lower in the sound eye than in the amblyopic eye (MT, 267 microm vs 253 microm, p = 0.005; FV, 2.57 mm(3) vs 2.43 mm(3), p = 0.001). In anisometropic amblyopia, there was no significant difference between eyes in either MT or FV., Conclusions: In patients with strabismic amblyopia, the MT and FV were slightly but significantly lower in the sound eye than in the amblyopic eye. The clinical importance of this difference is not known. No such difference was observed in patients with anisometropic amblyopia.

Amblyopia is a developmental visual disorder associated with loss of monocular acuity and sensitivity as well as profound alterations in binocular integration. Abnormal connections in visual cortex are known to underlie this loss, but the extent to which these abnormalities are regionally or retinotopically specific has not been fully determined. This functional magnetic resonance imaging (fMRI) study compared the retinotopic maps in visual cortex produced by each individual eye in 19 adults (7 esotropic strabismics, 6 anisometropes and 6 controls). In our standard viewing condition, the non-tested eye viewed a dichoptic homogeneous mid-level grey stimulus, thereby permitting some degree of binocular interaction. Regions-of-interest analysis was performed for extrafoveal V1, extrafoveal V2 and the foveal representation at the occipital pole. In general, the blood oxygenation level-dependent (BOLD) signal was reduced for the amblyopic eye. At the occipital pole, population receptive fields were shifted to represent more parafoveal locations for the amblyopic eye, compared with the fellow eye, in some subjects. Interestingly, occluding the fellow eye caused an expanded foveal representation for the amblyopic eye in one early-onset strabismic subject with binocular suppression, indicating real-time cortical remapping. In addition, a few subjects actually showed increased activity in parietal and temporal cortex when viewing with the amblyopic eye. We conclude that, even in a heterogeneous population, abnormal early visual experience commonly leads to regionally specific cortical adaptations.

In the last 5 years, we witnessed the progress in the basic and clinical research of strabismus and amblyopia in China, which should be attributed to the effective leadership of the Chinese Ophthalmological Society and the efforts of all members of the professional team. We are glad to see the work of our researchers and clinical scientists in the studies on the molecular and neuronal mechanisms of amblyopia, visual developmental plasticity and functional brain imaging of amblyopia, in the studies on the extraocular muscle's pulley and in the studies on the diagnoses and therapies of strabismus and amblyopia, and furthermore, in epidemiological studies of strabismus and amblyopia. We expect more fruits and creative findings in this field in China in the next decade.

Amblyopia, sometimes called "lazy eye," is a relatively common developmental visual disorder well characterized behaviorally; however, the neural substrates associated with amblyopia in humans remain unclear. We hypothesized that abnormalities in the cerebral cortex of subjects with amblyopia exist, possibly as a result of experience-dependent neuronal plasticity. Anatomic magnetic resonance imaging (MRI) and psychophysical vision testing was carried out on 74 subjects divided into two age ranges, 7-12 years and 18-35 years, and three diagnoses, strabismic amblyopia, anisometropic amblyopia, and normal vision. We report a behavioral impairment in contrast sensitivity for subjects with amblyopia, consistent with previous reports. When the high-resolution MRI brain images were analyzed quantitatively with optimized voxel-based morphometry, results indicated that adults and children with amblyopia have decreased gray matter volume in visual cortical regions, including the calcarine sulcus, known to contain primary visual cortex. This finding was confirmed with a separate region-of-interest analysis. For the children with amblyopia, additional gray matter reductions in parietal-occipital areas and ventral temporal cortex were detected, consistent with recent reports that amblyopia can result in spatial location and object processing deficits. These data are the first to provide possible neuroanatomic bases for the loss of binocularity and visual sensitivity in children and adults with amblyopia.

Purpose: To compare the retinal nerve fiber layer [RNFL] thickness of the amblyopic eye with that of the normal eye in patients with anisometropic and strabismic amblyopia., Methods: Scanning laser polarimetry was performed with the GDx Nerve Fiber Analyzer (NFA), a scanning laser ophthalmoscope that measures the thickness of the peripapillary RNFL quantitatively and objectively, in vivo, based on the birefringence of the RNFL. Eighteen anisometropic, two strabismic and four combined amblyopic (both anisometropia and strabismus) patients were enrolled in the study. There were 9 male and 15 female patients, age range 7-66 years. Using Student's t-test, 14 GDx parameters in the amblyopic eyes and sound eyes were compared., Results: The GDx parameters showed no significant differences between the two groups [p > 0.5]. The superior average and inferior average values were 79.50 microm and 80.41 microm, respectively, in the amblyopic group, and 80.75 microm and 82.75 microm, respectively, in the healthy eyes. The average thickness did not differ between amblyopic and sound eyes (65.50 microm and 66.45 microm, respectively)., Conclusion: Assessment of RNFL thickness by means of scanning laser polarimetry revealed no difference between the two eyes in patients with unilateral amblyopia.

Objective and Background: Strabismus and anisometropia early in life frequently causes monocular amblyopia. Activation of the visual cortex is compared between the two types of amblyopia to elucidate differences in the pathogenetic mechanism of the disease., Methods: Using an EPI gradient echo sequence in 1.5T MRI, calcarine activation by monocular viewing of checkerboard patterns with reversal was examined in terms of binocularity of the activation and dependence on the spatial frequency of the stimuli., Results: First, the proportion of voxels activated by both normal and amblyopic eye monocular stimulations is lower in the strabismic group than in the anisometropic group. Second, the activation by higher-spatial-frequency stimuli is reduced in the anisometropic group, but not in the strabismic group., Conclusions: These findings from the human visual cortex are consistent with the view proposed based on animal research that the loss of binocular interaction and the undersampling of high-spatial-frequency components of visual stimuli are each one of the underlying changes in strabismic and anisometropic amblyopia, respectively.

Background and Purpose: Amblyopia is characterized by histopathological changes in the visual cortex and lateral geniculate nucleus. In the retina, however, no abnormalities have yet been reported. The purpose of this study was to compare the nerve fiber layer (NFL) thickness in the amblyopic eye with that in the sound eye of patients with strabismic amblyopia. As a practical implication, we investigated the validity of comparing Nerve Fiber Analyzer (NFA) measurements obtained in amblyopic eyes to the normative database built into the NFA., Methods: NFL thickness was measured with a third generation NFA, the GDx (Laser Diagnostic Technologies, San Diego, CA). This is a scanning laser polarimeter, designed for monitoring glaucoma. The following NFL thickness parameters (all in microns) were compared: average thickness, superior maximum, inferior maximum, superior average, inferior average, nasal median and temporal median. Twenty patients with strabismic amblyopia were imaged with the NFA. Patients had no nystagmus, neurological disease or glaucoma. Nine patients had amblyopia in the right eye, and 11 patients in the left eye., Results: In general, the sound eyes yielded higher thickness measures than the amblyopic eyes. These differences, however, were small, averaging only 1.5%, p = 0.6, and therefore not "statistically significant" at the p&le 0.05 level., Conclusions: Using the standard of "Statistical Significance = p< or =0.05", when amblyopic eyes are measured with the NFA, the built-in normative database may serve as the reference data

Amblyopia is a developmental disorder of pattern vision. After surgical creation of esotropic strabismus in the first weeks of life or after wearing -10 diopter contact lenses in one eye to simulate anisometropia during the first months of life, macaques often develop amblyopia. We studied the response properties of visual cortex neurons in six amblyopic macaques; three monkeys were anisometropic, and three were strabismic. In all monkeys, cortical binocularity was reduced. In anisometropes, the amblyopic eye influenced a relatively small proportion of cortical neurons; in strabismics, the influence of the two eyes was more nearly equal. The severity of amblyopia was related to the relative strength of the input of the amblyopic eye to the cortex only for the more seriously affected amblyopes. Measurements of the spatial frequency tuning and contrast sensitivity of cortical neurons showed few differences between the eyes for the three less severe amblyopes (two strabismic and one anisometropic). In the three more severely affected animals (one strabismic and two anisometropic), the optimal spatial frequency and spatial resolution of cortical neurons driven by the amblyopic eye were substantially and significantly lower than for neurons driven by the nonamblyopic eye. There were no reliable differences in neuronal contrast sensitivity between the eyes. A sample of neurons recorded from cortex representing the peripheral visual field showed no interocular differences, suggesting that the effects of amblyopia were more pronounced in portions of the cortex subserving foveal vision. Qualitatively, abnormalities in both the eye dominance and spatial properties of visual cortex neurons were related on a case-by-case basis to the depth of amblyopia. Quantitative analysis suggests, however, that these abnormalities alone do not explain the full range of visual deficits in amblyopia. Studies of extrastriate cortical areas may uncover further abnormalities that explain these deficits.

The physiopathologic specifics of the strabismic amblyopia which certify its origin in the disorders of neuronal and disbinocular development are discussed. The changes are produced at the level of systems situated in development during the trouble. The sensorial function is last obtained on the phylogenesis and is first affected as well as the central retina which is developed after the peripheral retina. It's about one deficiency of the foveal function that determine the functional and anatomical troubles in the cortex. The functional changes and after the organic changes are the result of the autoregulation and after reorganisation of the system due the inadequate stimulation of the deviated eye and competitive impulses.

ACTIVATION of NMDA (N-methyl-D-aspartate) receptors has recently been proposed as a prerequisite for the induction of experience-dependent modification of visual cortical neurones seen during early postnatal development. A new monoclonal antibody to the NMDA receptor subunit 1 (NMDA-R1) has been used to localize and compare the distribution of the receptors in the primary visual cortex of normal cats and those raised with either amblyopia induced by monocular optical blur or monocular esotropic strabismus. Although all three groups showed densest labelling in layers II-III, a comparison of immunopositive cells at any depth below the cortical surface showed a significantly lower frequency in strabismic and anisometropic cats than in normal cats, but a greater frequency in anisometropic cats that in strabismic animals. There appears to be no direct relationship between the expression of NMDA-R1 receptors and the level of excitability, binocularity or neuronal acuity known to exist in either of these two cat models of amblyopia, thus raising further questions as to the precise nature of the role of NMDA receptors in the processes of visual cortical plasticity.

Cell shrinkage in monkey lateral geniculate nucleus (LGN) layers supplied by the amblyopic eye have been described in experimental amblyopia caused by visual deprivation, anisometropia, and strabismus. A human brain from a strabismic amblyope became available for study and the authors compared cell sizes in LGN layers receiving input from the normal and the amblyopic eye. Significant cell shrinkage was present in layers connected with the amblyopic eye, and was most evident in the ipsilateral LGN. These findings support the validity of the monkey model for the study of strabismic amblyopia by showing, for the first time, changes in the brain from a human strabismic amblyope that are similar to those previously described in monkeys.

To date most surgeons operate only on the nonamblyopic eye in patients with strabismus and amblyopia with unpredictable, initial, surgical results. We present a series of 13 patients with amblyopia and strabismus plus anomalous head positions who underwent surgery on their nonamblyopic eye. The good, initial, surgical results in 77% of these patients suggest that operating on the good eye is important to dictate the final surgical results in correcting the deviation and normalizing the head position.