Abstract
Purpose: :
The relationship between peripheral refraction and growth of the posterior segment of the eye is currently of particular relevance to our understanding of the aetiology of myopia. We investigate the concordance of estimated retinal shape profiles derived using peripheral axis refractive measurements with those measured independent of the eye’s optics using 3-dimensional (3D) Magnetic Resonance (MR) imaging.
Methods: :
The SRW-5000 open-view binocular IR autorefractor was used to obtain central and peripheral refractive error measurements on thirty-eight young adult subjects up to a maximum of 30° retinal eccentricity in the horizontal meridian. Subjects were grouped by central refractive error MSE (D); 17 myopes (-4.19±3.20) and 21 emmetropes (0.21±0.60); range -10.56 to +1.56D. The Zeiss IOL Master was used to obtain PCI axial length measurements and keratometry readings. OD retinal contour profiles were generated using Dunne’s method, a previously published customized computer program based on peripheral refraction and ocular biometric measurements (Dunne, 1995). Subjects also underwent 3D ocular MR scanning; from which 2D representations of the posterior segment were generated. Concordance of the resultant retinal shape profiles from each technique was examined at 10, 20, and 30 degrees eccentricity from the fovea.
Results: :
Statistically significant differences between the two sets of retinal profiles were noted at each eccentricity (p<0.001); in general, the MR method produced a flatter profile compared to Dunne’s method. Concordance between the two sets of retinal profiles diminished as a function of increasing retinal eccentricity; mean difference (MRI-Dunne’s method) at 10, 20°, and 30° respectively was (in mm±sd) 0.61±0.95; 1.24±1.17; 2.17±1.60. The disparity between the two sets of retinal profiles was also found to differ between refractive groups (p<0.05). Mean differences at 10, 20, and 30° for the myopic group respectively were; 0.86±0.95; 1.65±1.28; 2.66±1.83; and for emmetropic group were 0.41±0.92, 0.91±0.98, 1.77±1.31.
Conclusions: :
Significant differences exist between the retinal profiles generated by peripheral refraction and MR imaging methods. The mean level of discrepancy between techniques grew as a function of both greater retinal eccentricity and level of central myopic refractive error.
Keywords: myopia • imaging/image analysis: clinical • refractive error development