The change in retinal landscape associated with axial length and spherical equivalent refractive error

Purpose. To determine the effect of axial length and spherical equivalent refractive error (S.E.R.E.) on foveal thickness and topography measurements obtained with the commercially available Retinal Thickness AnalyzerRTM (RTA).;Methods. Twenty eyes of 14 adult healthy subjects (7 male, 13 female; mean age = 46.6 years; range = 25--65 years of age) were examined in regard to foveal thickness, topography and axial length. Each potential subject underwent a complete ophthalmologic examination including subjective refraction, frequency doubling visual fields, central corneal thickness, retinal thickness, retinal topography and axial length determination. Axial length and central corneal thickness was measured using standard A-scan ultrasonic methodology. Retinal thickness and topography measures were determined using RTA software version. 4.5. Data analysis included non-parametric regression, Kendalls rank correlation and studentized-t examination of the residuals (Sigma Stat version 3.1, Stats Direct 2.5.7) This cross-sectional study was approved by the IRB of Nova Southeastern University and conducted in accordance with the guidelines provided by the Declaration of Helsinki.;Results. Axial length was correlated with corrected minimum foveal thickness (CMFT) (Kendall's tau b = 0.364, two sided on corrected continuity z, p = 0.027) and foveal diameter (FD) (Kendall's tau = 0.474, two sided on corrected continuity z, p = 0.004). Axial length and S.E.R.E were correlated (Kendall's tau b = -0.706, two sided on corrected continuity z, p < 0.0001). S.E.R.E was correlated with CMFT (Kendall's tau b = -0.370, two sided on corrected continuity z, p = 0.027) and FD (Kendall's tau b = -0.374, two sided on corrected continuity z, p = 0.025).;Conclusions. The analysis reveals that as axial myopia increases the foveola thickens and the foveal rim moves peripherally. This study lends support to previous works that have examined this question and additionally found that the foveal diameter increases with axial length. Future studies using spectral domain optical coherence tomography to examine the interaction of this axial length/S.E.R.E. effect on the posterior pole will be valuable in more accurately defining early macular disease. Studies that determine biometric parameters of the fovea should consider the using topographic landmarks instead of fixed diameter measures to improve accuracy.