Abstract
Purpose:
In corneas requiring endothelial keratoplasty for Fuchs endothelial corneal dystrophy (FECD), haze (corneal backscatter) from the anterior cornea is higher than normal and remains higher than normal after keratoplasty. In this study, we examined the changes in anterior corneal haze over a range of severity of FECD.
Methods:
In a cross-sectional study, 95 corneas of 70 patients with FECD (mean age, 67 years; range, 41-87 years) and 52 normal corneas of 28 controls (mean age, 44 years; range, 21-77 years) were examined by slit-lamp and confocal microscopy. Clinical grade of FECD was determined by slit-lamp examination based on the presence and extent of guttae, and the presence or absence of clinically evident edema (modified Krachmer grades 1-6). FECD was categorized as mild (grades 1-2), moderate (grades 3-4), or advanced (grades 5-6). Corneas of control subjects were devoid of any central guttae (grade 0). Corneal haze, measured from the reflected light intensity profile of confocal microscopy (ConfoScan 4, Nidek Technologies) images, was standardized to reflectivity from a known concentration of a turbidity standard. Anterior corneal haze was defined as the mean reflectivity in a 10-percentile range of stromal thickness centered at the anterior stromal boundary. Haze was compared between severities of FECD and normal by using generalized estimating equation (GEE) models to account for any correlation between fellow eyes of the same subject. The correlation between anterior haze and grade was illustrated by the Pearson correlation coefficient, and the significance was determined by GEE models.
Results:
Anterior corneal haze in FECD (1940 ± 700 scatter units [SU], n=95) was higher than normal controls (1185 ± 229 SU, n=52, p<0.001). Anterior corneal haze was higher in advanced (2176 ± 692 SU, n=67) than in moderate (1445 ± 260 SU, n=14, p<0.001) or mild (1302 ± 236 SU, n=14, p<0.001) FECD, and higher in moderate FECD than in controls (p=0.003). For all eyes, anterior corneal haze was correlated with grade (r=0.68, p<0.001, n=147).
Conclusions:
The increase in anterior corneal haze, which is associated with disability glare, begins early in the course of FECD and prior to the onset of clinically evident edema. Whether anterior corneal haze in early grades of FECD is related to the presence of chronic sub-clinical edema or to changes affecting the optical quality of the cornea is uncertain.
Keywords: 461 clinical (human) or epidemiologic studies: natural history •
481 cornea: endothelium •
630 optical properties