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Authors: Min-Woo Lee, Ju-Mi Kim, Yong-Il Shin, Young-Joon Jo, Jung Yeul Kim
Journal: Ophthalmology (2019)

We thank Wright et al for their interest and comments regarding our article, which evaluated longitudinal changes in peripapillary retinal nerve fiber layer (pRNFL) thickness in patients with high myopia by comparing their eyes with the eyes of normal individuals.1Lee M.-W. Kim J.-m. Shin Y.-I. et al.Longitudinal changes in peripapillary retinal nerve fiber layer thickness in high myopia: a prospective, observational study.Ophthalmology. 2019; 126: 522-528Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar We hypothesized the mechanism of the decrease in pRNFL thickness as the globe elongation that leads to mechanical stretching and thinning of the retina as the previous study, and Wright et al recommended to identify if there was progressive axial elongation in the subjects who were enrolled in the study.2Leung C.K.-S. Mohamed S. Leung K.S. et al.Retinal nerve fiber layer measurements in myopia: an optical coherence tomography study.Invest Ophthalmol Vis Sci. 2006; 47: 5171-5176Crossref PubMed Scopus (249) Google Scholar Recently, we reported the longitudinal changes in the axial length in patients with high myopia without any other ophthalmic disease.3Lee M.-W. Lee S.-E. Lim H.-B. et al.Longitudinal changes in axial length in high myopia: a 4-year prospective study.Br J Ophthalmol. 2019 Aug 13; ([Epub ahead of print])Google Scholar Although the subjects did not overlap completely because of the different starting point and study period between 2 studies, the inclusion criteria of 2 studies were almost same. We identified that myopic eyes showed a consistent increase in axial length over 4 years, in which the rate of change was 0.047 mm/y, and eyes with a longer baseline axial length showed a greater increase in axial length than eyes with a shorter axial length. Age was also one of the significant factors which might be associated with changes of axial length in high myopia subjects, although it did not show a significant result in multivariate analyses. These findings would be helpful to explain the mechanism of the reduction in pRNFL thickness in high myopia, which might be related to mechanical stretching. We did not exclude patients with mild peripapillary chorioretinal atrophy, which may not influence the measurements of pRNFL thickness owing to its small size, and the atrophy did not show any changes until the last follow-up. Additionally, glaucomatous changes such as an enlarged cup or increased cup/disc ratio were not found during the study period. Thus, these factors may be less relevant to the reduction of pRNFL thickness. We enrolled the high myopia group based on axial length rather than SE because SE could be affected by the cataract or refractive surgeries. So subjects with an axial length of ≥26.00 mm were classified into the high myopia group regardless of the SE. We defined the control group with SE to show that there was no high myopia in terms of both axial length and SE in the control group. Actually, the longest axial length in the control group was 25.88 mm, so there was no overlapping patients in the 2 groups. The patients were enrolled with unilateral rhegmatogenous retinal detachment, epiretinal membrane, macular hole, or intraocular lens dislocation as well as patients without any ophthalmic disease in both eyes. One eye was selected randomly in subjects without any disease in both eyes, except for a few cases; 1 in the 40- to 49-year age subgroup of the high myopia group, 1 in the 40- to 49-year age subgroup of the control group, and 2 in 30- to 39-year age subgroup of the control group. Although there might be some bias because patients enrolled both eyes, the number was not critical to the results of our report. Re: Lee et al.: Longitudinal changes in peripapillary retinal nerve fiber layer thickness in high myopia: a prospective, observational study (Ophthalmology. 2019;126:522-528)OphthalmologyVol. 127Issue 1PreviewWe were interested to read this study, with its finding that “highly myopic eyes had a significantly greater decrease in [the peripapillary retinal nerve fiber layer] pRNFL over 2 years than normal eyes.”1 We have found the pRNFL to be cross-sectionally associated with myopia (and intraocular pressure, age, and smoking, among others)2 as well as optic disc area.3 The possible reasons for the greater thinning are of interest, particularly with the increasing prevalence of high myopia in the world. Full-Text PDF