Abstract
Abstract: :
Purpose: High resolution imaging of retinal disease to resolutions below 10 microns in the horizontal plane and below 50 microns in depth (or below 15 microns by OCT) requires compensation for errors induced by imperfect human optics. Such adaptive optical correction requires understanding of the ocular wavefront aberrations in individuals with retinal disease. Methods: 28 eyes of 25 patients with retinal disease and 23 eyes of 18 patients without retinal disease were studied. Two morphological classifications were assigned as follows: Macular elevation lesions included epiretinal membrane, macular edema, choroidal neovascularization and subretinal hemorrhage. Macular depression lesions included eyes with Macular hole, scar and geographic atrophy. Using a ray-tracing wavefront sensor (Visual Function Analyzer, Tracey Technologies, Houston, TX), each eye was scanned 2-3 times at both small (<4mm, 3mm as default) and large (>=4mm, 5mm as default) pupil apertures and each of 25 Zernike coefficients (2nd to 6th order) were acquired. MANOVA analysis was carried out on these coefficients and several indexes generated from those coefficients. Results: Throughout the study, total RMS (Root Mean Square of 25 Zernike coefficients) ranged between 0.294 to 11.085µm (2.729±2.376, Mean±SD) at large scan area, 0.172 to 5.801 (0.950±1.055) at small scan area. In the macular elevation group total RMS was mildly elevated at 58% greater than controls, this was borderline significant. This was due to S3 (RMS of 3rd order Zernike coefficients), S5, S6 and S3+S5 (Coma-like aberration), on average 65% greater than normals, and the differences in these factors were statistically significant after controlling for age, phakic status, scan size and conventional refraction (p=0.0486, 0.0074, 0.0444, 0.0148 individually, MANOVA). Conclusion: Higher order wavefront aberrations, particularly coma are detected in eyes with irregular macular elevations. Our study suggests that such aberrations may be artifacts resulting from irregular or multiple reflecting retinal surfaces. The abnormal surface causes distortions of the point image that is projected onto the retina to determine higher order aberrations. In order to use adaptive optics to improve the visualization of small retinal structures, modifications in the examination protocol of most wavefront sensors will be needed to avoid artifacts if the macula is irregular.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • macula/fovea • retina