Cone mosaic in eyes with varied axial length using adaptive optics scanning laser ophthalmoscopy

Abnormalities in cone photoreceptor topography are closely associated with the development of various ocular diseases, including axial myopia. Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) enables high-resolution, single-cell imaging of the living human retina. This study aimed to investigate the potential relationship between cone topography and axial myopia using a commercial AOSLO system. A total of 74 participants (148 eyes; 30 men, 40.5%) with a mean age of 31.8 ± 10.4 years were included. Cone mosaics were imaged at 3° and 5° eccentricities of the fovea centralis. The relationships between cone parameters (linear cone density, cone spacing, cone dispersion, and cone regularity) and axial length were analyzed. Linear cone density significantly decreased with increasing axial length at both 3° and 5° eccentricities (all P < 0.001). Cone spacing significantly increased with greater axial length and reduced cone density. After adjusting for axial length, cone spacing was significantly associated only with linear cone density at both 3° and 5° eccentricities (all P < 0.001). Cone dispersion significantly increased with longer axial length and lower cone density. After adjusting for axial length, cone dispersion remained significantly associated with linear cone density only at the inferior 3° (β = -0.43, P = 0.014) and inferior 5° eccentricities (β=-0.4, P=0.003). Cone regularity significantly increased with higher linear cone density at certain 3° eccentricities (nasal: β=0.34, P<0.001; temporal: β=0.25, P=0.006; inferior: β = 0.2, P = 0.04) and significantly decreased with longer axial length at temporal 5° eccentricity (β = -0.57, P < 0.001). Linear cone density was significantly reduced in axial myopia. The uniformity of cone distribution was disrupted as a result of the reduction in cone density. Additionally, cone regularity was significantly diminished in axial myopia, potentially due to the direct effects of axial elongation at 5° eccentricity or reductions in cone density at 3° eccentricity.