Abstract
Abstract: :
Purpose: Measurements of potential acuity are widely performed before cataract surgery to predict postoperative visual acuity. One such test, the potential acuity pinhole (PAP) has been reported to be effective without spectacle correction. We explored the impact of optical correction on PAP performance. Methods: A prospective, double–masked, crossover study of 15 healthy volunteers with no prior ocular surgery and best corrected acuity 20/25 or better. Subjects performed nine consecutive PAP tests under cycloplegia with various spherical lenses worn over best distance correction. Lenses ranged from –3 diopters (D) to +9 D in 1.5 D steps. Linear regression was performed. T–tests were employed to determine significance. Results: The best mean visual acuity during PAP was achieved with a +1.5 or +3 D lens over the distance correction (0.043 and 0.049 logMAR). A plano lens, compared to a +3 D lens, over distance correction caused a small but significant reduction in PAP (0.11 vs 0.049, p<0.01). The decline in PAP worsened exponentially with minus lenses of –1.5 D or greater or plus lenses greater than +4.5 D over distance correction. Regression analysis yields a quadratic polynomial, tightly correlated to the parabolic relationship between PAP logMAR and reading lens power (R2=0.78): The formula is PAP logMAR = 0.11 + 0.13 (logMAR BCVA) – 0.07 (D) + 0.01 (D)2, where D represents the error lens placed over distance correction. Conclusions: We used spherical lenses over distance correction to simulate the impact of uncorrected refractive error during PAP testing. Our results suggest optical correction is critical to obtaining the best performance on PAP test. Uncorrected moderate to high myopes, –6, –7.5, and –9 D, will lose 1.7, 3.8, and 6 Snellen lines on PAP testing, compared to optimal near correction. Uncorrected low hyperopes, 1.5 to 3 D, lose 2.2 to 3.8 lines of vision compared to optimal near correction. Near correcting an emmetrope would improve mean PAP nearly 1 Snellen line (p <0.01).
Keywords: cataract • refraction • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled