CAN Optical Coherence Tomography redefine amblyopia?

Impact of transcranial Direct Current Stimulation on stereoscopic vision and retinal structure in adult amblyopic rodents

Purpose

The impact of visual deprivation on retinal structure is widely debated. Experimental models, like monocular deprivation through lid suture, provide insights into the consequences of lacking visual experience during development. This deprivation delays primary visual cortex (CV1) maturation due to improper neural connection consolidation, which remains plastic beyond the critical period. However, few studies have used Optical Coherence Tomography (OCT) to investigate structural alterations in the retina of animal models following monocular deprivation. Instead, some studies have focused on the ganglion cell layer using post-mortem histological techniques in amblyopia models induced by monocular deprivation.

Methods

In this study, we used Cliff test to assess stereoscopic vision and spectral domain optical coherence tomography (SD-OCT) to evaluate retinal changes in an in vivo model of visual deprivation treated with Transcranial Direct Current Stimulation (tDCS).

Results

The depth perception test initially revealed differences between individuals with amblyopia and the control group. However, after 8 tDCS sessions, amblyopic subjects matched the control group's performance, which remained stable Additionally, significant changes were observed in retinal structures post-tDCS treatment. Specifically, the thickness of the Nerve Fiber Layer + Ganglion Cell Layer + Inner Plexiform Layer (NFL+GCL+IPL) increased significantly in amblyopic eyes (p<0.001). Moreover, significant retinal thickening, including the Nerve Fiber Layer + Ganglion Cell Layer + Inner Plexiform Layer (NFL+GCL+IPL) and the entire retina, was observed post-tDCS treatment (p<0.05), highlighting the critical role of tDCS in ameliorating amblyopia. Additionally, treated animals exhibited reduced thickness in the Inner Nuclear Layer (INL) and Outer Nuclear Layer (ONL).

Conclusion

tDCS treatment effectively restores amblyopic individuals' stereoscopic vision, aligning their performance with controls, while impacting retinal structure, highlighting its potential in ameliorating amblyopia's visual deficits.

Optical coherence tomography predictors of the outcomes of occlusion therapy in anisometropic amblyopia

AIM

(1) To compare optical coherence tomography (OCT) parameters between amblyopic eyes and fellow eyes in patients presenting with anisometropic amblyopia. (2) To find OCT factors predicting the outcomes of occlusion therapy.

MATERIALS AND METHODS

This prospective study was conducted in a tertiary eye care center for a period of 20 months. Fifty-four children diagnosed with anisometropic amblyopic were included in the study. After complete ophthalmic and OCT examination, patients were advised to undergo occlusion therapy with large spectacle patch. Patients were reviewed after 6 months to record improvement in visual acuity and analyze their OCT parameters. Statistical tests used were paired "t" test and independent "t" test.

RESULTS

The mean age of 54 study patients was 9.24 ± 2.82 years. For comparison of OCT parameters, they were classified as myopic (22 patients), hypermetropic (24 patients), and astigmatic (8 patients) groups. In the anisomyopic amblyopia group, the mean inner macular thickness was significantly increased in fellow eyes (304.09 ± 11.06 μm) compared to amblyopic eyes (297.59 ± 14.16 μm). In the anisohyperopic amblyopia group, the outer macular thickness significantly increased in amblyopic eyes (286.43 ± 18.63 μm) when compared to fellow eyes (272.62 ± 14.90 μm). In the follow-up visit, 28 patients showed improvement and 6 patients did not show improvement in final best-corrected visual acuity, and the OCT parameters in amblyopic eyes of these two groups did not differ significantly.

CONCLUSION

Abnormal experience in early life does not affect the maturation process of retinal layers as evident by OCT parameters, and these parameters cannot predict the outcomes of occlusion therapy.

Morphological changes in amblyopic eyes in choriocapillaris and Sattler's layer in comparison to healthy eyes, and in retinal nerve fiber layer in comparison to fellow eyes through quantification of mean reflectivity: A pilot study

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.

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.

Analysis of Macular Vessel Density and Foveal Avascular Zone in Adults with Amblyopia

Purpose: To quantify and compare the foveal avascular zone (FAZ) and the whole, parafoveal and foveal vessel density of superficial (SCP) and deep capillary plexus (DCP) in amblyopic eyes of adults and age-matched controls.Methods: This cross-sectional study involved 52 eyes from 34 subjects aged 18 to 45 years. Optical coherence tomography angiography (OCTA) was performed to all participants and SCP, DCP and FAZ were evaluated. SPSS (Statistical Package for the Social Sciences) 23 was used for data analysis.Results: Eighteen of 34 subjects (52,9%) were amblyopic and 16 (47,1%) of them controlled. Mean subject age was 31.2 years in the amblyopia group and 28.3 years in the control group. The mean FAZ measurements were 0.28 ± 0.08 in amblyopic eyes, 0.29 ± 0.08 in fellow eyes and 0.3 ± 0.11 in control eyes. The whole, foveal and parafoveal vessel density of SCP in both 3x3-mm and 6x6-mm scans were not statistically different in amblyopic eyes, fellow eyes and control eyes. In 6x6-mm scans, the whole, and parafoveal vessel density of DCP were significantly lower in amblyopic eyes than controls. There was no statistically significant difference in 3x3-mm scans about DCP.Conclusion: OCTA revealed lower vessel density in DCP of amblyopic eyes than fellow eyes and controls in adults.

Assessment of macular vascular plexus density using optical coherence tomography angiography in cases of strabismic amblyopia

Purpose:

To evaluate the superficial retinal vascular plexus density using optical coherence tomography angiography (OCTA) in cases of strabismic amblyopia.

Methods:

Ten eyes of 10 patients with purely strabismic amblyopia underwent detailed ocular evaluation followed by the assessment of the superficial retinal plexus vascular density using OCTA (Topcon DRI OCT Triton, Swept Source OCT, Topcon, Japan). Ten contralateral normal eyes of the same patients were considered as control. All these 20 eyes underwent a 4.5 × 4.5 mm cube scan OCTA centered at the fovea. Using the Topcon propriety software all 20 eyes were assessed for the capillary plexus density of the superficial retinal vascular plexus along the superior, inferior, nasal, and temporal quadrants centered at the fovea. The numerical values were statistically assessed using a paired t-test with respect to each quadrant between the normal and the pathological eyes.

Results:

The average age of patients was 16 years and eight patients were males. The mean superficial retinal vascular plexus density along the superior, inferior, nasal, and temporal quadrants in normal and pathological eyes were 49.25 ± 30.34 and 48.93 ± 2.85, 47.22 ± 4.11 and 47.37 ± 4.8, 45.54 ± 1.55 and 43.81 ± 4.21, and 46.26 ± 4.63 and 46.38 ± 5.40, respectively. Similarly, the capillary densities along the central were 17.84 ± 3.49 and 17.24 ± 2.44 in normal and pathological eyes. The differences among all these four quadrants and central area were not statistically significant (P-values > 0.05 for all four quadrants and central area) as compared with the normal eyes.

Conclusion:

The superficial retinal vascular plexus density of a 4.5 × 4.5 mm cube centered at the fovea of eyes of cases of strabismic amblyopia is similar to that of normal eyes.