The Effect of Corneal Light Scatter on Vision After Penetrating Keratoplasty

PURPOSE: To determine the effect of corneal light scatter on vision after penetrating keratoplasty (PK). DESIGN: Cross-sectional study. METHODS: SETTING: Cornea service at Mayo Clinic, Rochester, Minnesota. STUDY POPULATION. Sixty-one eyes with clear grafts at 14.6 +/- 10.5 years after PK; 12 eyes with late endothelial failure (LEF) at 19.7 +/- 6.4 years after PK; 41 normal eyes. OBSERVATION PROCEDURES: PK. MAIN OUTCOME MEASURES: Backscatter from different depths of the cornea was measured by a custom scatterometer; intraocular forward light scatter was measured with a stray light meter; high-contrast visual acuity (HCVA) was measured by Early Treatment Diabetic Retinopathy Study (ETDRS) or Snellen chart; mesopic and photopic low-contrast visual acuity (LCVA) were measured with a 10% contrast chart. RESULTS: Backscatter from the anterior, middle (stroma), and posterior thirds of the cornea was higher in clear grafts compared with normal (P < .001), and higher in grafts with LEF compared with clear grafts (P < .001). Corneal stromal backscatter from clear grafts correlated with time after keratoplasty (r = 0.21; P = .006; n = 61). Forward light scatter was higher in eyes with clear grafts compared with normal (P <= .006), and higher in eyes with LEF compared with clear grafts (P :5.01). Corneal stromal backscatter from clear grafts correlated with HCVA (r = 0.34; P = .02; n = 52), mesopic LCVA (r = 0.36; P = .01; n = 28), and photopic LCVA (r = 0.57; P < .001; n = 28). Forward scatter in eyes with clear grafts correlated with photopic LCVA (r = 0.38; P = .04; n = 26). CONCLUSIONS: Light scattered from the cornea increases with time after PK and is associated with decreased high- and low-contrast vision. (Am J Ophthalmol 2008; 146:913-919. (C) 2008 by Elsevier Inc. All rights reserved.)