Abstract
Purpose: :
To compare corneal haze and contrast sensitivity after deep lamellar endothelial keratoplasty (DLEK) with haze and contrast sensitivity after penetrating keratoplasty (PK).
Methods: :
Patients with corneal edema from endothelial dysfunction were prospectively randomized to DLEK or PK. Before and at 6 months after surgery visual acuity was measured by automated high–contrast ETDRS, and in vivo confocal microscopy was performed. Contrast sensitivity with spectacle correction was measured by using a Functional Acuity Contrast Test. Backscattered light from the cornea was measured from digitized high magnification video images of a slit–beam. The average image brightness in the anterior, middle and posterior thirds of the image of the cornea was multiplied by the corneal thickness and expressed as scatter units (U). Corneal haze was defined as the difference in scatter from the mean of the same measurement in 20 normal control corneas. Variables were compared between groups by using a two–tailed t–test or rank sum test, and correlation among variables was studied by using the Spearman test.
Results: :
At 6 months after surgery, mean spectacle–corrected visual acuity was 20/56 in DLEK eyes and 20/44 in PK eyes. Before surgery, corneal haze was 54502 ± 27224 U in DLEK corneas and 47398 ± 29063 U in PK corneas (p=0.53). Six months after surgery, haze was greater in DLEK corneas than PK corneas in the anterior (7645 ± 5705 U vs. 4084 ± 1317 U, p=0.006), middle (5846 ± 2889 U vs. 1702 ± 1189 U, p<0.001), and posterior (5486 ± 4631 U vs. 1913 ± 1621 U, p=0.008) stromal thirds. The depth of greatest backscatter in DLEK corneas corresponded to increased reflectivity in confocal microscopy images of the superficial stroma and the donor–host interface. The log score for contrast sensitivity at 1.5 cycles/degree was 1.55 ± 0.19 for DLEK eyes and 1.13 ± 0.62 for PK eyes (p=0.08). Contrast sensitivity was not significantly different between the two groups at any other spatial frequency tested. Within each group, haze did not correlate with contrast sensitivity at 1.5 cycles/degree (p= 0.8 in each group).
Conclusions: :
Six months after transplant, corneas treated by DLEK have more haze than corneas treated by PK. The stromal depth of greatest haze in DLEK corneas corresponds to the graft–host interface and superficial stroma. However, haze does not appear to correlate with contrast sensitivity.
Keywords: transplantation • cornea: stroma and keratocytes • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials