The relationship between magnification and visual acuity in biphakic eyes

Objective To compare spectacle magnification and visual acuity in highly myopic phakic eyes corrected by anterior chamber intraocular lenses (IOLs) and eyes corrected with spectacles.Methods A comparative study was conducted on the change in best corrected visual acuity before and after anterior chamber intraocular lenses were inserted in 44 eyes (26 patients) with high myopia from -9.875 to -24.75 D. Spectacle magnification (SM) in the myopic phakic eyes corrected with both IOLs and spectacle lenses was calculated. The actual results were compared to theoretical predictions. Results The BCVA of pre-operation and post-operation is 4.742±0.2435 and 4.911±0.1956 respectively. There was significant difference between the results (t=11.234,P=0.000). The result of spectacle magnification shows that phakic intraocular lens can magnify retinal image 15%～45% than spectacle in range from -10～-30 D myopia. There was positive correlations between magnification change and post-operative BCVA improvement (r=0.504,P=0.000).Conclusion Spectacle magnification is an important reason for improving BCVA in extreme high myopia. The phakic anterior chamber intraocular lens can improve BCVA by 1 or more lines.