Year : 2019 | Volume
: 67 | Issue : 7 | Page : 1023--1024
Commentary: Analysis of macular, foveal and retinal nerve fiber layer thickness in children with unilateral anisometropic amblyopia and their changes following occlusion therapy
Department of Pediatric Ophthalmology, Strabismus, and Neuro-ophthalmology, Child Sight Institute, Nimmagada Prasad Children's Eye Care Centre, L V Prasad Eye Institute, GMRV Campus, Visakhapatnam, Andhra Pradesh, India
Dr. Virender Sachdeva
Department of Pediatric Ophthalmology, Strabismus, and Neuro-ophthalmology, Child Sight Institute, Nimmagada Prasad Children's Eye Care Centre, L V Prasad Eye Institute, GMRV Campus, Visakhapatnam, Andhra Pradesh - 530 040
|How to cite this article:|
Sachdeva V. Commentary: Analysis of macular, foveal and retinal nerve fiber layer thickness in children with unilateral anisometropic amblyopia and their changes following occlusion therapy.Indian J Ophthalmol 2019;67:1023-1024
|How to cite this URL:|
Sachdeva V. Commentary: Analysis of macular, foveal and retinal nerve fiber layer thickness in children with unilateral anisometropic amblyopia and their changes following occlusion therapy. Indian J Ophthalmol [serial online] 2019 [cited 2020 Aug 9 ];67:1023-1024
Available from: http://www.ijo.in/text.asp?2019/67/7/1023/261048
In the current issue of this Journal, authors report an interesting paper titled “analysis of macular, foveal, and retinal nerve fiber layer thickness in children with unilateral anisometropic amblyopia and their changes following occlusion therapy.”
Although the pioneering work of Hubel and Weiss showed that amblyopia related changes occur in the visual cortex, the role of retinal structural changes in amblyopia has always been contemplated. With the advent of optical coherence tomography, many researchers have tried to understand changes in the retinal nerve fibre layer (RNFL) and macular thickness following amblyopia therapy., These reports suggest conflicting results about the changes in RNFL thickness but more consistently increased macular thickness in the amblyopic eyes thickness.,, In a further leap, authors in the current study report changes in these parameters following occlusion therapy.
The current study is well-designed. The study population is uniform with unilateral anisometropic amblyopes. Inclusion and exclusion criteria are well-defined. Controls are appropriately selected. Authors report that amblyopic eyes had similar RNFL thickness, but higher macular and foveal thickness at baseline as compared to the normal eyes. The study showed a reduction in the average macular and foveal thickness of amblyopic eyes following compliant amblyopia therapy, whereas there was no significant change in the age-matched controls. However, there was no statistically significant change in the overall RNFL thickness.
Prior studies by Yan et al. and Pang et al. showed similar results, and they attributed increase in baseline central macular thickness to the 'arrest of the postnatal foveal maturation in amblyopic eyes.' They proposed that during the process of normal maturation, there is a reduction in the central macular thickness and reorganization in the Henle's layer during maturation, also called as foveal delamination. They proposed following amblyopia therapy with glasses and occlusion, improvement in the quality of the image on the fovea might accelerate this process, leading to a reduction in average macular thickness.
This explains overall change in the central macular and foveal thickness at the inception of amblyopia therapy. From this hypothesis, one would expect an increase in the overall RNFL thickness as well, however, it was not observed in the current study or prior studies. One possible explanation might be that the maturation of the foveal area is a more of a process of re-organization in the Henle's layer and it might be more sensitive to the improvement in visual acuity than changes in the RNFL. In a similar study, Yoon et al. had shown a small reduction in the foveal volume following compliant amblyopia therapy. However, their study did not have any control groups.
Although the study is well-designed, the major limitation of the study is small sample size especially for sub-group analysis by age and refractive error. The authors did perform the subgroup analysis according to age and reported more reduction in the macular thickness (MT) and foveal thickness (FT) following occlusion therapy in younger children (5–10 years) vs. older children (10–15 years). This is again expected given the more sensitive visual system in younger children.
The authors have also reported the changes in the best corrected visual acuity (BCVA), macular, foveal thickness, and RNFL thickness following occlusion therapy according to refractive errors of the patient. The authors report that the change in the macular thickness was maximum for the myopic patients, however, the maximum improvement in the BCVA occurred in hypermetropes. This is little surprising and might raise concern about the hypothesis proposed by the authors.
In general, amblyopia is denser among hypermetropes. It is possible that hypermetropes had worse BCVA at presentation itself, and therefore, these patients had more scope for improvement in BCVA than myopes.
Moreover, greater change in the average macular and foveal thickness than improvement in the BCVA in myopes suggests possibly that other factors might also influence the change in these parameters than amblyopia therapy alone. Prior studies have also shown myopes tend to have overall thinner macular and RNFL as compared to hypermetropes. Hence, overall change in macular and foveal thickness might be influenced by the age-related development processes in different refractive error subgroups. These questions might be answered by future studies with adequate sample size in each subgroup.
In spite these considerations, this work represents significant insight into the changes in the retinal thickness that take place following amblyopia therapy and should open doors for more research in this field. More studies with stringent design and adequate sample size are needed to validate the results shown by the authors. Further studies should also include children with stimulus deprivation and strabismic amblyopia as well to be able to extrapolate the results to these populations as well.
|1||Kavitha V, Heralgi MM, Harishkumar PD, Harogoppa S, Shivaswamy HM, Geetha H. Analysis of macular, foveal, and retinal nerve fiber layer thickness in children with unilateral anisometropic amblyopia and their changes following occlusion therapy. Indian J Ophthalmol 2019;67:1016-22.|
|2||Nooden GK Von. Examination of the patient – IV. In Binocular Vision and Ocular Motility. Theory and Management of Strabismus. 6th ed. St Louis: Mosby; 2002. p. 246-97.|
|3||Pang Y, Goodfellow GW, Allison C, Block S, Frantz KA. A prospective study of macular thickness in amblyopic children with unilateral high myopia. Invest Ophthalmol Vis Sci 2011;52:2444-9.|
|4||Atakan M, Culfa S, Calli U, Penbe AD, Atakan TG. Evaluation of retinal nerve fibre layer and macular thickness in amblyopia. J ClinExpOphthalmol2015;6:437.|
|5||Yen MY, Cheng CY, Wang AG. Retinal nerve fiber layer thickness in unilateral amblyopia. Invest Ophthalmol Vis Sci2004;45:2224-30.|
|6||Pang Y, Frantz KA, Block S, Goodfellow GW, Allison C. Effect of amblyopia treatment on macular thickness in eyes with myopic anisometropic amblyopia. Invest Ophthalmol Vis Sci 2015;56:2677-83.|
|7||Yoon DH, Chun BY. Comparison of the thickness and volume of the macula and fovea in patients with anisometropic amblyopia prior to and after occlusion therapy. Korean J Ophthalmol 2018;32:52-8.|
|8||Jin P, Zou H, Zhu J, Xu X, Jin J, Chang TC, et al. Choroidal and retinal thickness in children withdifferent refractive status measured by swept-source optical coherence tomography. Am J Ophthalmol 2016;168:164-76.|