We read with great interest the article by Myers and associates, providing normative values of spectral-domain optical coherence tomography (SD OCT) macular thickness measurements in a large adult cohort without retinal disease, and examining relationships with age, sex, and other ocular and systemic covariates. The authors found that when adjusting for age, men had thicker retinas than women in the Early Treatment of Diabetic Retinopathy Study (ETDRS) center macula subfield (men vs women: 289.5 vs 273.8 μm, P < .001) and inner ring (337.1 vs 332.5 μm, P < .001) but not in the outer ring (290.7 vs 288.9 μm, P = .08). These results were confirmed in multivariate analyses, where male sex was independently associated with a thicker retina in the center subfield and in the inner circle of the retina. These findings are consistent with several previous studies using SD OCT in adult populations from different ethnicities: American and also Japanese, Korean, Pakistani, and Chinese (studies summarized by Gupta and associates, Table 6).
In their paper, Myers and associates advanced the hypothesis, raised by several authors, that the finding of foveal thinning in women compared to men could be attributed to hormonal changes at menopause and this may help to explain why women are at higher risk for developing macular holes than men. However, our findings in a large multicenter cohort of children (283 children with a mean age of 9.5 years) do not provide support for this hypothesis. We found similar differences at earlier ages and, in fact, a multivariate-adjusted linear regression model confirmed a significant association between sex and central macula thickness in children. Boys had a significantly thicker central macula than girls by 10.39 μm (β = 10.39, 95% confidence interval: 5.96-14.83; P < .001). Although in our paper we did not publish any subsequent analyses, the results were also significantly higher for boys in average inner ring sectors (β = 6.16 μm; P = .001) but not in average outer macula ring sectors (β = 1.04 μm; P = .52). Only the temporal quadrant of the outer ring was significantly higher in boys (β = 4.48 μm; P = .02). In their study with 2068 12-year-old children, Huynh and associates found similar results using time-domain OCT. In a more recent study with 107 Turkish children, boys had also a significantly thicker central macula and inner macula ring than girls. Furthermore, the intersex quantitative difference of 10 μm in mean foveal thickness and of 6 μm in average inner ring sectors in our study were similar to those reported in other studies with children. Although in the studies with adults these intersex differences were a bit higher, they remained in a similar order of magnitude (between 10 and 15.7 μm in mean foveal thickness and between 4.6 and 9.11 μm in average inner ring sectors ).
Our hypothesis is that, as these intersex differences are present from childhood, it is likely that they could be genetically induced instead of being hormonally caused.