Modeling the Effect of Forward Scatter and Aberrations on Visual Acuity after Endothelial Keratoplasty

• Published in: Investigative ophthalmology & visual science Vol. 53; no. 9; p. 5545
• Main Authors: McLaren, Jay W., Patel, Sanjay V.
• Format: Journal Article
• Language: English
• Published: United States 15.08.2012
• Subjects: Adult; Contrast Sensitivity - physiology; Descemet Stripping Endothelial Keratoplasty; Humans; Middle Aged; Refraction, Ocular - physiology; Scattering, Radiation; Vision, Ocular - physiology; Visual Acuity - physiology; Young Adult
• ISSN: 1552-5783; 1552-5783
• DOI: 10.1167/iovs.12-10011

To evaluate the effects on visual acuity of forward scatter and aberrations typical of those after Descemet stripping endothelial keratoplasty (DSEK). Twenty normal eyes of 20 subjects (ages 22-57 years) were examined with best spectacle correction. Under photopic conditions, high-contrast visual acuities (HCVAs) were measured by using ETDRS charts. Visual acuity was also measured by using aberrated charts that simulated the typical high-order aberrations at 12 months after DSEK. Forward scatter was induced by viewing the eye charts through a 1-mm-thick layer of scattering solution (Amco Clear, at a concentration of 4000 nephelometric turbidity units) and was measured with a straylight meter. Forward scatter increased from 1.19 ± 0.11 log straylight parameter (log[s]; mean ± SD) without induced scatter to 1.57 ± 0.06 log(s) with induced scatter (P < 0.001). Induced scatter reduced HCVA on the nonaberrated chart by 2.7 Snellen letters, from 20/19 (Snellen equivalent) to 20/21 (P < 0.001) and by 2.1 letters on the aberrated chart, from 20/25 to 20/28 (P = 0.005). Addition of aberrations reduced HCVA by more than twice the number of Snellen letters than did induced scatter, by 6.4 letters with low scatter (P < 0.001), and by 5.8 letters with high scatter (P < 0.001). Under typical clinical testing conditions, increased forward scatter has minimal effect on visual acuity. High-order aberrations are a more likely cause of degraded visual acuity than is forward scatter in eyes with clear corneas after DSEK.