Axial length-related cut-off value for increase in glaucomatous and non-glaucomatous optic neuropathy prevalence

PURPOSE: To assess the cut-off value for an axial length-related increase in the prevalence of glaucomatous/glaucoma-like (GON/GLON) and non-glaucomatous (NGON) optic neuropathy. METHODS: The project included the population-based Beijing Eye Study (n=3088; age: 40+ years), Ural Eye and Medical Study (n=5199 participants; age: 40+ years), Ural Very Old Study (n=428; age: 85+ years), Ural Children Eye Study (n=4185; school grade: 1+) and Central India Eye and Medical Study (CIEMS; n=4199; age: 30+ years). Using fundus photographs (all studies) and optical coherent tomographic images (all studies except for CIEMS), we assessed the prevalence of GON/GLON and NGON, defined by optic nerve head appearance and absence of neurological perimetric defects. RESULTS: The total study population included 34 864 eyes (17 099 individuals; age: 46.1±23.0 years; range: 6 to 100 years) (axial length: 23.19±1.05 mm; range: 18.22-34.20 mm). Prevalence of GON/GLON and NGON were 438/17 099 (2.6%; 95% CI 2.0 to 3.0) and NGON 57/17 099 (0.3%; 95% CI 0.0 to 0.4) respectively. Higher GON/GLON prevalence was correlated with longer axial length (OR: 1.45; 95% CI 1.35 to 1.56; p<0.001) after adjusting for age and intraocular pressure. The increase in GON/GLON prevalence started at an axial length of 27.0 mm and 26.5 mm for a younger subgroup aged ≤52 years and an older subgroup aged >52 years respectively. Higher NGON prevalence was associated with longer axial length (OR: 4.35; 95% CI 3.58 to 5.29; p<0.001) after adjusting for age. The increase in NGON prevalence started to rise at an axial length of 27.0 mm and 26.5 mm for the younger subgroup and older subgroup, respectively. CONCLUSIONS: Prevalence of GON/GLON and NGON started to increase at an axial length of 27.0 mm and 26.5 mm for individuals aged ≤52 years or >52 years, respectively. These cut-off values may be helpful for the differentiation of moderate myopia versus high myopia.