Effect of peripapillary chorioretinal atrophy on GDx parameters in patients with degenerative myopia

Purpose: To determine the effect of peripapillary chorioretinal atrophy in degenerative myopia on the retinal nerve fibre layer (RNFL) thickness measurements performed by scanning laser polarimetry. Methods: Polarimetric RNFL analysis was done in 41 degenerative myopic eyes of 25 patients with spherical refractive errors between -7.50 and -22.00 D (mean -12.50 D; SD 3.5). Analysis was also performed on 46 eyes of 24 age-matched healthy subjects with spherical refractive errors between -1.00 and +1.00 D (mean -0.25 D; SD 0.50) with GDx Nerve Fiber Analyzer (Version 1.0.12). All of the myopic patients had clinically evident peripapillary chorioretinal atrophy in their fundus examination. Results: In myopic patients most of the GDx parameters were statistically different from the control group (P < 0.05). Although average thickness, ellipse average, number, inferior maximum and inferior average were found to be higher than the healthy subjects, the modulation parameters and the ratio-based parameters were significantly decreased in degenerative myopic patients (P < 0.05). The TSNIT (temporal, superior, nasal, inferior, temporal) graph showed irregular high spikes with loss of the regular double hump pattern, especially in quadrants with large chorioretinal atrophy and visible sclera. Conclusion: Peripapillary chorioretinal atrophy increased retardation values, which might be explained by the high reflectivity of the bare sclera in these areas.