Nerve Fiber Layer Thickness

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We read with great interest the recent article by Huynh et al. as part of the Sydney Childhood Eye Study, which was performed on the macular and peripapillary retinal nerve fiber layer (RNFL) thickness in children. The authors described several considerable findings including amblyopic children who were not significantly different from nonamblyopic children in regard to ethnicity.1Huynh S.C. Samarawickrama C. Wang X.Y. et al.Macular and nerve fiber layer thickness in amblyopia: the Sydney Childhood Eye Study.Ophthalmology. 2009; 116: 1604-1609Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar In another recent study that was part of Sydney Childhood Eye Study, the authors concluded that children of East Asian ethnicity, when compared with those of European Caucasian ethnicity, had a significantly thicker RNFL thickness and a substantially larger cup-to-disc ratio.2Samarawickrama C. Wang J.J. Huynh S.C. et al.Ethnic differences in optic nerve head and retinal nerve fibre layer thickness parameters in children.Br J Ophthalmol. 2010; 94: 871-876Crossref PubMed Scopus (50) Google Scholar Currently, very limited data exist on the morphology of the RNFL thickness and optic nerve head (ONH) parameters in Asian populations. Knowledge of these normal structures in different races would provide an important reference value and may assist in the identification of glaucoma. Based on the current evidence from Australia, comparison performed between Caucasian, East Asian, and Middle Eastern, and further classifications did not perform to other ethnicity subgroups.1Huynh S.C. Samarawickrama C. Wang X.Y. et al.Macular and nerve fiber layer thickness in amblyopia: the Sydney Childhood Eye Study.Ophthalmology. 2009; 116: 1604-1609Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar However, according to Sydney Myopia Study, the term East Asian covers people originating from China, Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, Singapore, Indonesia, Philippines, Japan, and Korea, which is a very wide range in terms of ethnicity categorization. Studies showed that RNFL thickness in the measured Thai population was about 10% thicker than that in the original normative database.3Manassakorn A. Chaidaroon W. Ausayakhun S. et al.Normative database of retinal nerve fiber layer and macular retinal thickness in a Thai population.Jpn J Ophthalmol. 2008; 52: 450-456Crossref PubMed Scopus (44) Google Scholar Another study showed that the optic disc area of Thai subjects is larger than Caucasians and Hispanics. When comparing these data within Asian population, Thai subjects also had a larger optic disc area than the Japanese.4Ruangvaravate N. Neungton C. Normative data of optic nerve head in Thai population by laser scanning tomography: Siriraj study.J Med Assoc Thai. 2008; 91: 859-863PubMed Google Scholar In another study, RNFL thickness assessment of Korean healthy eyes using the Stratus OCT (Carl Zeiss Meditec, Dublin, CA) resulted in different false-positive rates in different peripapillary sectors. These data suggest that RNFL thickness profiles may vary based on ethnicity, and for the Asian region in particular, these findings recommend the need for a database especially for the Asian population.5Kim T.W. Kim T.W. Park K.H. Kim D.M. An unexpectedly low Stratus optical coherence tomography false-positive rate in the non-nasal quadrants of Asian eyes: indirect evidence of differing retinal nerve fibre layer thickness profiles according to ethnicity.Br J Ophthalmol. 2008; 92: 735-739Crossref PubMed Scopus (16) Google Scholar It is clear that different study designs, either hospital-based or population-based, and diversity in measurement methods, may play a role in the discrepancy of these data within the Asian population. However, there is a clear need for more systematic epidemiologic surveys mapping of a database and a reference value within East Asian countries regarding RNFL thickness and ONH parameters in healthy individuals. These data are essential in the evaluation and management of glaucomatous patients. Macular and Nerve Fiber Layer Thickness in Amblyopia: The Sydney Childhood Eye StudyOphthalmologyVol. 116Issue 9PreviewTo examine macular and peripapillary retinal nerve fiber layer (RNFL) thickness in amblyopia. Full-Text PDF