Macular and retinal nerve fiber thickness in recovered and persistent amblyopia

The evaluation of the macular and optic nerve head microvasculature in amblyopic and non-amblyopic patients with constant exotropia in comparison to healthy controls

OBJECTIVE

To evaluate the retinal microvascular changes in strabismic amblyopia and compare them to the strabismic cases without amblyopia and controls.

DESIGN

Cross-sectional study.

PARTICIPANTS

Three groups of patients, including 25 amblyopic cases with exotropia (XT), 25 constant XT cases without amblyopia, and 25 healthy subjects as controls, are included in the study. Both eyes of the included participants are evaluated.

METHODS

All the patients underwent a thorough ophthalmic examination, BCVA assessment, and macular and optic nerve head OCTA with the AngioVue™ Imaging System.

MAIN OUTCOME MEASURES

The vascular density (VD) of various layers (Deep and superficial capillary plexus (DCP and SCP) in different regions of the macula, optic nerve head, and FAZ area were evaluated as the target variables.

RESULTS

42 females and 33 males with a mean age of 32.2 (95%CI:29.8-34.6) entered our study. The median exotropia in both groups was 35 PD. The parafoveal DCP VD was significantly lower in both eyes of amblyopic cases than in controls (53.56 and 52.31 vs. 56.13%, p:0.021, <0.001). The parafoveal SCP VD was only lower in the dominant eye of the amblyopic cases than in the controls (50.53 vs. 53.54%, p:0.002). The foveal and peripapillary VD showed no significant difference between the groups. The FAZ area was significantly larger in amblyopic eyes than the fellow eyes (0.250 vs. 0.194 mm2, p:0.025) and correlated with worse BCVA (Correlation Coefficient: 0.358, p: 0.011).

CONCLUSIONS

The amblyopia could be accompanied by a lower parafoveal DCP VD and a larger FAZ area in strabismic amblyopia.

OCT-Angiography Findings in Children with Anisometropic Amblyopia

PURPOSE

The purpose of this prospective study is to show findings of OCT angiography in children with anisometropic amblyopia with a statistically significant difference, regardless of the type of refractive disorder, between the amblyopic and the fellow eye. This research aimed to establish whether there is a difference in vascular density [VD] and size of the foveal avascular zone [FAZ] in the superficial capillary plexus [SCP].

METHODS

All children between 9 and 18 years of age who were treated at the Outpatient Clinic for Orthoptics and Pleoptics of the Department of Ophthalmology, University Medical Centre Maribor from January 2020 to December 2022 due to unilateral anisometric amblyopia were enrolled in our study. Fourteen children met the criteria. Cirrus 5000 high-resolution OCT with AngioPlex OCT angiography was used to analyze the size of the FAZ and VD in the SCP and TCS. The paired t-test or Wilcox signed-rank test [p < 0.05] was used for statistical analysis of each parameter between the amblyopic and fellow eye.

RESULTS

Mean child age was 13 years ± 2.9 and ranged from 9 to 18 years. Most of the children [85.7%] were boys. The VD of the SCP did not show statistically significant differences between the visually impaired and control eyes [p = 0.328]. The comparison of the FAZ area between the two eyes was also not statistically significant [p < 0.808]. There was also no statistically significant difference in central macular thickness [TCS] [p < 0.291].

CONCLUSIONS

Our research results show no statistically significant differences in the VD and the FAZ of the SCP, and in the TCS between the amblyopic and fellow eye in children with unilateral anisometropic amblyopia. Our research did not confirm the results of certain previous studies in which a lower density of the capillary network was present in the visually impaired eye. Further studies with more children are necessary to confirm our results.

Macular superficial vascular density on optical coherence tomography angiography in children with unilateral anisometropic and bilateral hyperopic amblyopia

We analyzed whether macular superficial vascular density (SVD) and foveal vascular zone (FAZ) on optical coherence tomography angiography (OCTA) can distinguish between bilateral ametropic and anisometropic amblyopia. We included 42, 33, and 50 eyes in the bilateral ametropic amblyopia, anisometropic amblyopia, and normal control groups, respectively. Using macular swept-source optical coherence tomography angiography, we measured and analyzed the superficial FAZ areas and five sectoral macular SVDs after magnification correction. The anisometropic amblyopic eye group showed significantly increased foveal SVDs (p < 0.001) and significantly decreased superficial FAZ areas (p < 0.001), compared with the remaining groups. Additionally, the bilateral ametropic amblyopia group had significantly decreased nasal SVDs. SVDs and superficial FAZ areas differed among hyperopic amblyopia subtypes. These findings may reflect vascular distribution differences and macular changes in hyperopic amblyopia subtypes compared with normal eyes.

Anisometropic amblyopia: A review of functional and structural changes and treatment

Amblyopia is the decreased best-corrected visual acuity (BCVA) in one or both eyes caused by the abnormal processing of visual input during development. One common cause of amblyopia is anisometropia, which has attracted widespread attention. Many structural changes occur in the primary and extrastriate visual areas of the cerebral cortex, as well as in the eyes, in patients with anisometropic amblyopia. Understanding these mechanisms has provided a favorable theoretical basis for treating anisometropic amblyopia. This article reviews the functional and anatomical changes and progress toward the treatment of anisometropic amblyopia.

[Role of optical coherence tomography in unilateral amblyopia]

PURPOSE

To compare the macular and papillary parameters on optical coherence tomography (OCT) between the amblyopic eye and the healthy eye in subjects with unilateral strabismic or anisometropic amblyopia.

PATIENTS AND METHODS

This is a cross-sectional and comparative study carried out over two years, from April 1, 2019, to March 31, 2021. We included patients aged over 5years, followed for unilateral amblyopia, free of any neurological and/or ocular pathology. The evaluation of the macular and papillary parameters in the amblyopic and healthy eyes was performed with Swept-Source Optical Coherence Tomography (OCT-SS). The parameters were compared according to age group and type of amblyopia.

RESULTS

We collected 50 patients, 29 children, and 21 adults, with a mean age of 19.8years. Amblyopia was secondary to anisometropia in 40 patients and strabismus in 10 patients. Analysis of macular tomographic parameters found no significant difference between amblyopic eyes and healthy eyes for mean macular thickness (P=0.86), central macular thickness (P=0.86), or mean macular volume (P=0.54). The mean retinal peripapillary fiber thickness (RNFL) was 107.48μm in the amblyopic eye and 103.8μm in the healthy eye, with a statistically significant difference (P<0.001). This significant thickening of the RNFL in amblyopic eyes was present in adults (P<0.001), children (P<0.001), anisometropic (P<0.001), and strabismic amblyopia (P=0.024). Analysis of the other optic nerve head parameters revealed no significant difference between amblyopic eyes and healthy eyes in terms of optic disc surface area (P=0.89), neuro-retinal annulus surface area (P=0.47), vertical (P=0.98) or horizontal (P=0.74) cup to disc ratio.

CONCLUSION

Amblyopia is accompanied by thickening of the peripapillary retinal fibers without macular repercussions. However, larger prospective studies are needed to confirm these results.

OCT-Angiography Findings in Patients with Amblyopia: Comparison between Healthy Controls, Treatment-Responsive, and Treatment-Unresponsive Amblyopic Patients

There is no consensus on whether amblyopia affects the retinal vascular plexus and morphology. Previous studies focused on the differences between amblyopic patients and normal controls without evaluating amblyopic eyes after patching. To evaluate differences in the superficial vascular density of amblyopic eyes, normal eyes, and amblyopic eyes reaching normal BCVA after patch therapy, OCTA was used. All patients underwent a comprehensive ophthalmological examination, including visual acuity, refraction, ocular motility tests, and anterior and posterior segment examination. OCTA was performed by an expert physician using the Zeiss Cirrus 5000-HD-OCT Angioplex (Carl Zeiss, Meditec, Inc., Dublin, OH, USA). OCTA scans were performed using a 3 × 3 mm² and 6 × 6 mm² fovea-centered image setting. The mean outer macular vessel density in the previously amblyopic group was 19.15 ± 0.51%. This was statistically significantly higher than in both the amblyopic group (18.70 ± 1.14%) and the normal controls (18.18 ± 1.40%) (p = 0.014). The previously amblyopic group also significantly differed from both normal controls and amblyopic eyes with regards to the inner (p = 0.011), outer (p = 0.006), and full (p = 0.003) macular perfusion. Finally, linear regression analysis revealed that BCVA was linearly correlated to outer perfusion in amblyopic (p = 0.003) and ex amblyopic eyes (p < 0.001). Considering the cross-sectional nature of our study, from our results, we can only hypothesize a possible correlation between light stimulation and retinal vasculature development. However, further longitudinal studies are needed to support this hypothesis.

Effect of amblyopia treatment on macular microvasculature in children with anisometropic amblyopia using optical coherence tomographic angiography

To measure the retinal microvascular density in patients with anisometropic amblyopia using optical coherence tomographic angiography (OCTA) and to evaluate the effects of successful amblyopia treatment on microvasculature in retina. 59 children (5–12 years old) including 22 newly diagnosed unilateral anisometropic amblyopia, 16 recovered unilateral anisometropic amblyopia, and 21 control children were imaged with OCTA using 6 × 6-mm macular scan pattern. Vessel densities of the superficial capillary plexus (SCP), the deep capillary plexus (DCP), and the overall macular thickness were acquired and compared among the three groups. After adjustment for axial length, the amblyopia group showed lower macular vessel density in the SCP (P = 0.005) and in the DCP (P = 0.004) compared with that of the control group. However, for the recovered amblyopia group, no difference of vessel density was found when compared with the control group in both the SCP (P = 0.548) and the DCP (P = 0.124). No difference of the mean macular thickness was found among three groups (P ≥ 0.15). Children with anisometropic amblyopia have reduced macular vessel density in OCTA, while no difference of macular vessel density was found between the recovered amblyopic and control eyes. Macular thickness showed no difference in anisometropic amblyopia and remained unchanged after amblyopic treatment.

Macular capillary system and ganglion cell-layer complex of the amblyopic eye with optical cohorence tomography angiography and optical cohorence tomography

PURPOSE

To investigate the macular capillary system and ganglion cell-layer complex of the amblyopic eye with OCTA and OCT in comparison with fellow non-amblyopic eyes and a healthy control group and to examine their relationship with the severity of amblyopia.

METHODS

This prospective, cross-sectional comparative study enrolled 25 amblyopic patients and 25 healthy controls. All patients and controls underwent OCTA and OCT imagining. Macular vessel densities of the Superficial Capillary Plexus (SCP) and Deep Capillary Plexus (DCP) and retinal thickness were measured by OCTA and ganglion cell layer (GCL) by OCT.

RESULTS

SCP density at the fovea and parafovea was significantly lower in amblyopic eyes than in fellow eyes and control group. DCP density at the fovea was significantly lower in amblyopic eyes than fellow eyes and control group. Mean GCL thickness on OCT was 0.73 ± 0.07 μm in amblyopic eyes, 0.75 ± 0.06 μm in fellow eyes and 0.77 ± 0.06 μm in the control group. GCL volume was significantly lower in amblyopic eyes than the fellow eyes. The SCP and DCP and GCL thickness were not affected by the severity of amblyopia.

CONCLUSION

Macular vessel densities of the SCP and DCP of eyes with amblyopia is lower compared to the fellow non-amblyopic eyes and the control group. The thickness of GCL was lower in amblyopic eyes than fellow eyes while the severity of amblyopia did not have any impact on these structures. Microvascular retinal structures may have been affected in the course of amblyopia development.

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.

Lamina cribrosa thickness in children with hyperopic anisometropic amblyopia

AIM

To determine lamina cribrosa thickness (LCT) in the optic nerve head region of the eyes in children with hyperopic anisometropic amblyopia and to compare this thickness with that of fellow eyes, hyperopic non-amblyopia, and age-matched controls.

METHODS

Thirty-two patients (12.0±1.8y, mean± standard deviation) with hyperopic anisometropic amblyopia, 31 subjects with age- and refractive error-matched hyperopic non-amblyopia (10.7±2.2y), and 32 age-matched controls (11.2±2.0y) were included in this prospective, cross-sectional study. LCT was measured using an enhanced depth-imaging program of a spectral domain optical coherence tomographic instrument in all participants, and the correlation between LCT and axial length was calculated.

RESULTS

The mean LCT was 180.9±29.4 µm in amblyopic eyes, 247.7±19.0 µm in fellow eyes, 251.6±27.3 µm in hyperopic non-amblyopic eyes, and 240.2±15.8 µm in control eyes. Lamina cribrosa in amblyopic eyes was significantly thinner than fellow, hyperopic non-amblyopic, and control eyes (P<0.05). There was no significant correlation in LCT and axial length between amblyopic (P=0.16) and control (P=0.31) group.

CONCLUSION

Lamina cribrosa of eyes with hyperopic anisometropic amblyopia is significantly thinner than that of fellow eyes, hyperopic non-amblyopia, and age-matched controls. The LCT profile in amblyopic eyes is different from that observed in fellow, hyperopic non-amblyopic, and control eyes.

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.