Clinical determination of the corrected retinal image size in spectacle-corrected aphakes

For individual spectacle-corrected aphakic patients, a method of estimating the size of the corrected retinal image corresponding to distant objects smaller than Snellen 6/360 (20/1200) is developed. Our results indicate that an estimate of the corrected retinal image size corresponding to a distant Snellen 6/12 (20/40) object in an individual spectacle-corrected aphake can be obtained to within plus or minus 1.0 micron of error using a multivariate regression model based on the measurement of six patient factors: axial length, anterior corneal power, spectacle lens back vertex power, lens thickness, lens back curve, and lens vertex distance. Clinical application of these results are discussed along with comparisons to other results based on traditional spectacle magnification formulas. The size of the corrected retinal image corresponding to a Snellen 6/12 (20/40) object was found to vary between 60 and 84 micron in patients corrected with CR-39 optical plastic and for patients corrected with high-index optical glass, it was between 56 and 78 microns.