Axial myopia is associated with elongation of the posterior ocular segment. The authors measured posterior fundus landmarks and assessed their associations with axial length.
Using fundus photographs, the authors measured the vertical distance between the temporal superior and temporal inferior arterial arcade (VDA) and the angle kappa between the temporal arterial arcades among other morphometric variables.
The study included 456 eyes with a mean age of 61.2 ± 14.2 years (range: 13–88 years) and mean axial length of 29.4 ± 2.1 mm (range: 23.2–35.3 mm). Mean angle kappa was 91.3 ± 17.2° (range: 39–161°), and mean VDA was 7.93 ± 1.71 mm (range: 2.72–12.85 mm). In multivariate regression analysis, wider angle kappa was associated (regression coefficient r: 0.47) with shorter axial length (P = 0.002; beta: −0.17; B: −1.37; 95% confidence interval [CI]:−2.23 to −0.51), longer VDA (P < 0.001; beta: 0.27; B: 2.70; 95% CI: 1.85–3.54), shorter disk–foveola distance (P < 0.001; beta: −0.22; B: −4.76; 95% CI: −7.05 to −2.46), shorter vertical optic disk diameter (P = 0.002; beta: −0.14; B: −6.83; 95% CI: −11.1 to −2.56), lower number of any chorioretinal lesions (P = 0.007; beta: −0.13; B: −2.11; 95% CI: −3.63 to −0.58), and longer maximal vertical chorioretinal lesion diameter (P = 0.05; beta: 0.09; B: 0.92; 95% CI: −0.02 to 1.86). A longer VDA was associated (r: 0.31) with longer axial length (P < 0.001; beta: 0.22; B: 0.18; 95% CI: 0.10–0.25), wider angle kappa (P < 0.001; beta: 0.28; B: 0.03; 95% CI: 0.02–0.04) and higher number of chorioretinal lesions (P = 0.03; beta: 0.10; B: 0.16; 95% CI: 0.02–0.31). If eyes with chorioretinal lesions were excluded, the association between longer VDA and longer axial length was no longer statistically significant (P > 0.10).
Axial elongation was correlated with decreasing angle kappa, caused by an elongation of the disk–foveola distance because of an enlargement of the gamma zone, whereas VDA remained constant. By contrast, horizontal length of macular Bruch membrane and vertical length of macular Bruch membrane were independent of axial elongation. Axial elongation did not lead to lengthening of Bruch membrane in the macular region in eyes without macular chorioretinal lesions.
In myopic axial elongation, the angle kappa between the temporal vascular arcade decreases because the disk–foveola distance increases with longer axial length because of an enlargement of Bruch membrane–free parapapillary gamma zone, although the vertical distance between the temporal superior and temporal inferior vascular arcade and the length of Bruch membrane remain unchanged.
*Department of Ophthalmology, Medical Faculty Mannheim, Ruprecht-Karls-University of Heidelberg, Mannheim, Germany; and
†Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, Tokyo, Japan.
Reprint requests: Kyoko Ohno-Matsui, MD, PhD, Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 1138510, Japan; e-mail: email@example.com
Partly supported by grants from the Japanese Society for Promotion of Science (number; 15H04993, 15K15629).
J. B. Jonas—Consultant for Mundipharma Co. (Cambridge, United Kingdom), Alimera Co. (Alpharetta, GA), Boehringer Ingelheim Co. (Ingelheim, Germany), Sanofi Co. (Paris, France), and Allergan Co. (Dublin, Ireland); Patent holder with Biocompatibles UK Ltd. (Franham, Surrey, United Kingdom) (Title: Treatment of eye diseases using encapsulated cells encoding and secreting neuroprotective factor and/or anti-angiogenic factor; Patent number: 20120263794), and patent application with University of Heidelberg (Heidelberg, Germany) (Title: Agents for use in the therapeutic or prophylactic treatment of myopia or hyperopia; Europäische Patentanmeldung 15 000 771.4). The remaining authors have any financial/conflicting interests to disclose.