Effects of meridian and refraction on RPR and RPEL patterns are consistent with effects on retinal shape. Patterns derived from one of these predict the others: more positive (hyperopic) RPR predicts more negative RPEL and steeper retinas, more negative RPEL predicts more positive relative peripheral refraction and steeper retinas, and steeper retinas derived from peripheral eye lengths predict more positive RPR.

Abstract:We investigated changes in eye dimensions and retinal shape with degree of myopia, gender and race. There were 58 young adult emmetropes and myopes (range -1.25D to −8.25D), with 30 East-Asians (21 female/9 male), 23 Caucasians (16/7) and 5 SouthAsians (1/4). Three-dimensional magnetic resonance imaging was undertaken with a 3.0 Tesla whole-body clinical MRI system using a 4.0 cm receive-only surface coil positioned over the eye. Automated methods determined eye length, width and height, and curve fitting procedures determined asymmetric and symmetric ellipsoid shapes to 75%, 55% and 35% of the retina. With myopia increase, eye dimensions increased in all directions such that increase in length was considerably greater than increases in width and height. Emmetropic retinas were oblate (steepening away from the vertex) but oblateness decreased with the increase in myopia, so that retinas were approximately spherical at 7 to 8D myopia. Asymmetry of eyes about the best fit visual axis was generally small, with small differences between the vertex radii of curvature and between asphericities in the axial and sagittal planes. Females had smaller eyes than males, with overall dimensions being about 0.5mm less for the former. Race appeared not to have a systematic effect.

Lowered amplitude of accommodation exists in individuals with type 1 diabetes when compared with age-matched controls. The loss correlated strongly with duration of diabetes. The results suggest that individuals with diabetes will experience presbyopia earlier in life than people without diabetes, mainly due to changes in the lens.

This is a comprehensive study of a large range of biometric and optical parameters in people with type 1 diabetes. The parameters of 74 people with type 1 diabetes and an age matched control group were assessed. Most of the people with diabetes had low levels of neuropathy, retinopathy and nephropathy. Marginal or no significant differences were found between groups for corneal shape, corneal thickness, pupil size, and pupil decentrations. Relative to the control group, the diabetes group demonstrated smaller anterior chamber depths, more curved lenses, greater lens thickness and lower lens equivalent refractive index. While the optics of diabetic eyes make them appear as older eyes than those of people of the same age without diabetes, the differences did not increase significantly with age. Age-related changes in the optics of the eyes of people with diabetes need not be accelerated if the diabetes is well controlled. U. K. 102(3), 359-363 (1982). 32. J. Cavallerano, "A review of non-retinal ocular complications of diabetes mellitus," J. Am. Optom. Assoc. 61(7), 533-543 (1990). 33. S. Moss, R. Klein, and B. Klein, "Accommodative ability in younger-onset diabetes," Arch. Ophthalmol. 105(4), 508-512 (1987). 34. M. Spafford and J. Lovasik, "Clinical evaluation of ocular and visual functions in insulin-dependent juvenile diabetics," Am. J. Optom. Physiol. Opt. 63(7), 505-519 (1986). 35. S. Yamamoto, E. Adachi-Usami, and N. Kuroda, "Accommodation power determined with transient pattern visual evoked cortical potentials in diabetes," Doc. Ophthalmol. 72(1), 31-37 (1989

East Asians had steeper retinas than Caucasians. The horizontal meridian had steeper retinas than the vertical meridian. Myopes had steeper retinas than emmetropes. Racial differences in retinal shape in both emmetropes and myopes, combined with the high prevalence of myopia in East Asia, suggest that retinal shape may play a role in myopia development.

Abstract:To validate a simple partial coherence interferometry (PCI) based retinal shape method, estimates of retinal shape were determined in 60 young adults using off-axis PCI, with three stages of modeling using variants of the Le Grand model eye, and magnetic resonance imaging (MRI). Stage 1 and 2 involved a basic model eye without and with surface ray deviation, respectively and Stage 3 used model with individual ocular biometry and ray deviation at surfaces. Considering the theoretical uncertainty of MRI (12-14%), the results of the study indicate good agreement between MRI and all three stages of PCI modeling with <4% and <7% differences in retinal shapes along horizontal and vertical meridians, respectively. Stage 2 and Stage 3 gave slightly different retinal co-ordinates than Stage 1 and we recommend the intermediate Stage 2 as providing a simple and valid method of determining retinal shape from PCI data.

Hyperopes and emmetropes had greater relative peripheral myopia than myopes. There was asymmetry in RPRE along the vertical meridian for hyperopes which was not present in the emmetropes, suggesting there may be asymmetries in peripheral eye length along the vertical meridian for the former. Higher-order aberrations were affected by field eccentricity, but refractive error affected only the spherical aberration coefficient, which was more positive for hyperopes than for other groups.

Smaller lens diameters occurred in the diabetes groups than in the age-matched control groups. Differences in refractive index distribution between persons with and without diabetes are too small to have important effects on instruments measuring axial thickness.