Retinal Nerve Fibre Layer and Macular Thicknesses in Adults with Hyperopic Anisometropic Amblyopia

Evaluation of Macular Pigment Optical Density in Eyes with Hyperopic Anisometropic Amblyopia Using Fundus Reflectometry

Objectives

This study aimed to evaluate the macular pigment optical density (MPOD) scores in eyes with hyperopic anisometropic amblyopia and compare those with their fellow and control eyes using one-wavelength fundus reflectometry.

Methods

This cross-sectional study enrolled 33 patients diagnosed with hyperopic anisometropic amblyopia aged 12-40 years. The control group consisted of 36 hyperopic and 42 emmetropic children, age-matched to the patients. Central macular thickness (CMT), MPOD, axial length (AL), best-corrected visual acuity, and refraction errors were measured between the study group and the control group.

Results

Eyes with the diagnosis of hyperopic anisometropic amblyopia had significantly higher mean and maximum (max) MPOD scores compared with their fellow eyes as well as hyperopic and emmetropic eyes (p<0.001 for all). The mean AL in eyes with hyperopic anisometropic amblyopia was statistically shorter than that in hyperopic and emmetropic controls (p=0.027, p<0.001, respectively). The mean CMT was found to be thicker in eyes with hyperopic anisometropic amblyopia when compared to their fellow eyes, as well as hyperopic and emmetropic controls, eventhough there was no significant difference was found among the four groups (p=0.052). The mean MPOD levels were significantly correlated with the difference in CMT (r=-0.21, p=0.032), and logMAR visual acuity scores (r=-0.44, p<0.001) in the hyperopic anisometropic amblyopia group.

Conclusion

The present study indicates that the MPOD is reduced in eyes with hyperopic anisometropic amblyopia. This reduction may be due to less visual stimulus-induced deterioration of foveal development and microarchitecture in anisometropic amblyopic eyes.

Microvascular assessment of macula, choroid, and optic disk in children with unilateral amblyopia using OCT angiography

PURPOSE

To investigate the microvascular changes of macula, choroid, and optic disk in children with unilateral amblyopia.

METHODS

This prospective cross-sectional study involved 39 unilateral amblyopic children and 39 age- and sex-matched heathy participants who served as control. Vessel densities of the superficial and deep capillary plexuses (SCP and DCP), foveal avascular zone (FAZ) area, macular thickness, optic disk vessel density, retinal nerve fiber layer (RNFL) thickness, choriocapillaris vessel density, and subfoveal choroidal thickness were evaluated by OCT angiography (OCTA). Meanwhile, the correlations of microvascular perfusion and structural changes of macula, choroid, and optic disk were analyzed.

RESULTS

The vessel density of SCP and DCP in the whole macula in the amblyopic group was significantly lower than that in the control group after adjusting for age, axial length, and spherical equivalents (all P < 0.05). FAZ area, macular thickness, RNFL thickness, and the optic disk vessel density were not statistically different between the amblyopic group and the control group (all P > 0.05). Subfoveal choroidal thickness of amblyopic eyes was significantly higher than that of control eyes(P = 0.032). Choriocapillaris flow void (FV) in the amblyopic group was greater than that in the control group (P = 0.013). Significant differences were observed between the fellow eyes and the control eyes in choriocapillaris FV and subfoveal choroidal thickness (P = 0.011 and P = 0.042, respectively). Foveal SCP and DCP vessel density in all studied eyes were positively correlated with the whole macular thickness, respectively (r = 0.556 and r = 0.627, respectively, both P < 0.001). Whole SCP and DCP vessel density in the amblyopic eyes were negatively correlated with choriocapillaris FV (r = -0.723, P < 0.001; r = -0.512, P = 0.001, respectively).

CONCLUSION

Children with amblyopic eyes have attenuated macular and choriocapillaris perfusion. There is a need for future studies that will investigate the pathophysiology of amblyopia in children by OCTA.

How do the amblyopic and fellow eyes differ in adults?

OBJECTIVE

To investigate the differences between the amblyopic eye and the fellow eye in adults with anisometropic amblyopia.

MATERIALS AND METHODS

Measurements of the central macular thickness [CMT], subfoveal choroidal thickness [SFCT], and retinal nerve fiber layer [RNFL] in patients with anisometropic amblyopia were obtained using optical coherence tomography [OCT]. Axial length [AL], anterior chamber depth [ACD], and central corneal thickness [CCT] were measured with optical biometry. All 12 parameters were compared between the amblyopic eye [Group 1] and the fellow eye [Group 2].

RESULTS

A total of 110 eyes of 55 patients [9 myopic, 46 hypermetropic] were analyzed retrospectively. The ages of the patients ranged from 17 to 55 years, with a mean of 30.8±10.7 years. 56.4% [n=31] of the patients were female, and 43.6% [n=24] were male. The mean spherical equivalent [SE] was 1.96±3.79 in Group 1 and 1.28±2.45 in Group 2. SFCT was 312.00±53.03 in Group 1 and 283.47±51.91 in Group 2. AL was 22.53±1.40 in Group 1 and 22.79±1.18 in Group 2. SE, SFCT, and AL were statistically significantly different between the two groups. There was no difference between the two groups in terms of CMT, RNFL, ACD and CCT values.

CONCLUSION

In adults with anisometric amblyopia, the SFCT of the amblyopic eye is greater than that of the fellow eye. The choroid plays an important role in the nutrition of the retinal layers, the development of ocular function and refractive error, and its development may be affected by the refractive error. Since the majority of our patients were hyperopic, the AL was found to be shorter in the amblyopic eye. CMT, RNFL, ACD and CCT values were the similar in both groups. There was no clinically significant relationship between biometric parameters and OCT parameters.

Evaluation of macular and optic nerve head parameters in amblyopic eyes: An optical coherence tomography study

PURPOSE

To evaluate morphological differences in retinal nerve fibers layers (RNFL), optic nerve head (ONH), ganglion cell complex (GCC), and macular thickness between amblyopic and normal eyes from spectral domain optical coherence tomography (SD-OCT).

METHODS

Of 234 eyes of 117 children, four groups emerged: group A (162 eyes of 81 non-amblyopic subjects); group B (32 fellow eyes of 32 subjects with monolateral amblyopia); group C (32 amblyopic eyes of 32 subjects affected by monolateral amblyopia); group D (8 amblyopic eyes of 4 subjects with bilateral amblyopia). Patients underwent SD-OCT for ONH parameters, RNFL, GCC and macular thickness, retina map, and ONH scan quality index (SQI). Two-sided p values <0.05 were taken as statistically significant. (Analysis: STATA v.13).

RESULTS

Parameters with a significant difference between groups (p < 0.005) with their Standard Deviation (SD) are presented: rim area, 2.08 (0.49) mm² in group A and 1.76 (0.68) mm² in group C; disk area, 2.43 (0.45) mm² in group A and 2.02 (0.71) mm² in group C; central macular thickness, 250.99 (19.74) µm in group A and 267.16 (23.52) µm in group C; nerve fiber ONH SQI, 62.82 (13.15) in group A, 51.26 (15.55) in group C, 48.29 (14.37) in group D; retina map SQI, 63.34 (10.34) in group A and 57.34 (9.84) in group C. For other parameters no significant difference was observed (p > 0.005).

CONCLUSIONS

Amblyopia may influence optic nerve morphology, central macular thickness, and OCT scan quality. RNFL and GCC are not affected by monolateral amblyopia.

Impact of Amblyopia on the Central Nervous System

Amblyopia is a common perceptual disorder resulting from abnormal visual input during development. The clinical presentation and visual deficits associated with amblyopia are well characterized. Less is known however, about amblyopia's impact on the central nervous system (CNS). While early insights into the neuropathophysiology of amblyopia have been based on findings from animal models and postmortem human studies, recent advances in noninvasive magnetic resonance imaging (MRI) techniques have enabled the study of amblyopia's effects in vivo. We review recent retinal and neuroimaging research documenting amblyopia's structural and functional impact on the CNS. Clinical imaging provides some evidence for retinal and optic nerve abnormalities in amblyopic eyes, although the overall picture remains inconclusive. Neuroimaging studies report clearer changes in both structure and function of the visual pathways. In the optic nerves, optic tracts, and optic radiations of individuals with amblyopia, white-matter integrity is decreased. In the lateral geniculate nuclei, gray matter volume is decreased and neural activity is reduced. Reduced responses are also seen in the amblyopic primary visual cortex and extrastriate areas. Overall, amblyopia impacts structure and function at multiple sites along the visual processing hierarchy. Moreover, there is some evidence that amblyopia's impact on the CNS depends on its etiology, with different patterns of results for strabismic and anisometropic amblyopia. To clarify the impact of amblyopia on the CNS, simultaneous collection of retinal, neural, and perceptual measures should be employed. Such an approach will help (1) distinguish cause and effect of amblyopic impairments, (2) separate the impact of amblyopia from other superimposed conditions, and (3) identify the importance of amblyopic etiology to specific neural and perceptual deficits.

Thicknesses of Macular Inner Retinal Layers in Children with Anisometropic Amblyopia

Objective

To investigate the thicknesses of macular inner retinal layers in children with anisometropic amblyopia using spectral domain optical coherence tomography (SD-OCT).

Methods

Thirty-seven children with anisometropic amblyopia and fifty-seven children with normal vision were recruited in the study. Both eyes of children with anisometropic amblyopia and the right eyes of normal controls underwent scanning with the Spectralis OCT. The segmentation of retinal layers was performed automatically to measure individual inner retinal layers in the five sectors of the macular. An independent sample t-test was applied to compare the mean layer thicknesses of anisometropic eyes and fellow eyes with those of control eyes.

Results

There was no significant difference in the total macular thickness between amblyopic and control eyes. However, in the peripheral macular area, three of the four quadrants of both the ganglion cell layer (GCL) and the inner plexiform layer (IPL) thicknesses were significantly reduced in amblyopic eyes compared to control eyes. Moreover, two of the four quadrants of the GCL thickness and three of the four quadrants of the IPL thickness in the peripheral macular area were significantly reduced in fellow eyes than in control eyes.

Conclusion

The SD-OCT data revealed differences in the thicknesses of some macular inner retinal layers in both eyes of children with anisometropic amblyopia compared with those with emmetropia, indicating that structural changes might exist in the retina of children with amblyopia.

Evaluation of Bruch's membrane opening-minimum rim width and retinal nerve fiber layer thickness in adults with anisometropic amblyopia

PURPOSE

To investigate the relationship between Bruch's membrane opening-minimum rim width (BMO-MRW) and retinal nerve fiber layer thickness (RNFLT) in adult patients anisometropic amblyopia using spectral domain optical coherence tomography (SD-OCT).

MATERIALS AND METHODS

In this cross-sectional, observational study, 43 anisometropic eyes with corresponding fellow eyes. BMO-MRW (shortest distance from BMO to the internal limiting membrane) and peripapillary RNFLT were obtained with Spectral Domain Optic Coherence Topography (SD-OCT). Global and six sectors values according to the legacy distribution of the SD-OCT (nasal [N], nasal superior [NS], temporal superior [TS], temporal [T], temporal inferior [TI], and nasal inferior [NI]) for both RNFLT and BMO-MRW were evaluated.

RESULTS

Mean RNFLT and BMO-MRW measurements comparison showed no significance between anisometropia and fellow eyes. In correlation analyses ; although all sectors showed significant positive correlations; the global, TS and NI BMO-MRW sectors were significantly correlated with their corresponding RNFLT within both anisometropia and fellow eyes. In subgroup caparison analyses RNFLT and BMO-MRW showed no differences between amblyopia and fellow eyes. On subgroups correlation analyses, there were not a consistent correlation sectors between RNFLT and BMO-MRW.

CONCLUSIONS

In the analysis of the BMO-MRW and RNFLT measurements obtained by SD-OCT in adult anisometropic amblyopia patients, both parameters were evaluated not significant on showing structural changes. In correlation analysis within amblyopic and fellow eye groups, while there was positive correlation on all sectors, statistically significant relationships were detected in global, NI, TS sectors for both BMO-MRW and RNFLT measurements.

Analysis of Choroidal Vascularity in Children with Unilateral Hyperopic Amblyopia

This institutional case control study was carried out to compare choroidal vascularity (CV) in amblyopic eyes, fellow eyes, and control eyes in children with unilateral hyperopic amblyopia. Sixty-four eyes of 32 childeren with unilateral anisometropic hyperopic amblyopia and 38 eyes of 19 healthy children (controls), aged 3 to 16 years. Subfoveal choroidal thickness (CT) and CV were measured using spectral domain optical coherence tomography. The mean subfoveal CT of amblyopic eyes (338.9 ± 60.0 μm) was greater than that of fellow eyes (315.3 ± 63.3 μm, P = 0.043) and control eyes (313.0 ± 42.1 μm, P = 0.025). The mean CV of amblyopic eyes (0.715 ± 0.020) was greater than that of control eyes (0.700 ± 0.020, P < 0.001). While a positive correlation between CT and CV was found in normal eyes (r = 0.470, P = 0.004), a strong negative correlation existed in amblyopic eyes (r = −0.684, P < 0.001). In conclusion, although mean CV was higher in amblyopic eyes, the negative correlation between CT and CV may suggests insufficient blood supply to the outer retina and choroid in the affected eyes of patients with unilateral anisometropic hyperopic amblyopia.

Imaging Amblyopia: Insights from Optical Coherence Tomography (OCT)

Amblyopia refers to visual impairment resulting from perturbations in visual experience during visual development, typically secondary to strabismus, uncorrected refractive error, and/or deprivation. Amblyopia has traditionally been considered a cortical disease, but the depth of our understanding of this complex neurodevelopmental condition is limited by our ability to appreciate structural pathophysiology in the visual pathway. Recent advances in Optical Coherence Tomography (OCT) have facilitated numerous studies of the structural changes in the retina and optic nerve, thereby expanding our appreciation for the pathogenesis of this condition. In this review, we summarize findings from studies evaluating retinal, retinal nerve fiber layer, and choroidal thickness changes in patients with amblyopia. Focusing on the largest and most recent studies, we discuss common limitations and confounding variables in these studies. We summarize recent advances in ocular imaging technology and reconcile the findings of early histological reports with those of structural OCT in amblyopia.

CAN Optical Coherence Tomography redefine amblyopia?

Introduction: For many years, amblyopia was regarded as a disorder of the visual system in which an organic cause could not be identified. Optical Coherence Tomography opens new horizons in understanding the etiopathology of amblyopia and seems to highlight morphologic anomalies in the retina of the amblyopic eye.

Purpose: The objective of this paper is to analyze the macular thickness, optic nerve changes, and choroidal thickness found in patients diagnosed with amblyopia based on trials reported in the literature.

Material and methods: This study analyzes 30 clinical trials regarding amblyopia evaluation with Optical Coherence Tomography. The research articles analyzed were published between 2006 - 2016 and were identified on PubMed database.

Results: 19 research studies focused on macular and nerve optic changes, 7 on choroidal changes and 6 on retinal changes after occlusion. The results were discussed according to the type of amblyopia, alteration of macular thickness, optic nerve changes, ganglion cell layer changes, and alteration of choroidal thickness.

Conclusions: The results are of great variability, and it seems that macula and choroid involvement is more frequently suggested compared with optic nerve involvement.

Abbreviations: OCT = Optical Coherence Tomography, RNFL = Retinal Nerve Fiber Layer, GCC = Ganglion Cell Complex, ACD = Anterior Chamber Depth, BCVA = Best Corrected Visual Acuity

Changes in macular parameters in different types of amblyopia: optical coherence tomography study

PURPOSE

The purposes of this study were to investigate the changes in macular parameters (thickness, volume) and peripapillary retinal nerve fiber layer (RNFL) thickness (RNFLT) in different cases of amblyopia versus the normal fellow eyes using optical coherence tomography (OCT) and to estimate the relationship of OCT changes with various defined patients' parameters.

DESIGN

This is a prospective, observational, cross-sectional case series.

METHODS

The method involved measuring the peripapillary RNFLT, macular thickness, and macular volume via spectral domain (OCT) in different types of amblyopia and comparing with the other fellow eyes. This study was conducted at the Mansoura Ophthalmic Center.

RESULTS

A total of 64 patients with different types of amblyopia were included. The mean central macular thickness (CMT) was 196.2±50.03 µm in the amblyopic eyes versus 167±12.76 µm in the fellow eyes (P=0.000), the mean average macular thickness was 265.80±12.77 µm in the amblyopic eyes versus 259.10±3.09 µm in the fellow eyes (P=0.000), the mean macular volume was 7.59±0.32 mm³ in the amblyopic eyes versus 7.34±0.071 mm³ in the fellow eyes (P=0.002), and the mean global RNFLT was 97.00±11.60 µm in the amblyopic eyes versus 78.50±13.05 µm in the fellow eyes (P=0.029). There was a discrepancy between the different amblyopic types. Age and the axial length were the only independent variables that statistically significantly correlated with the CMT.

CONCLUSION

The unilateral amblyopic eyes were prone to have a higher CMT and thicker global RNFL compared to those of the sound fellow eyes. Retinal variations between different types of the amblyopia differ from one type to another. The age could be considered as a predictor of the disease worsening and treatment prognosis. Further studies are required to emphasize these results.