APR 26, 2013
This prospective study found that corneal central-to-peripheral thickness ratio (CPTR) may be an alternative and objective metric of disease severity in Fuchs' dystrophy that works better than clinical grading.
The authors assessed inter-observer agreement between two corneal specialists grading Fuchs' dystrophy based on the confluence and area of guttae and the presence or absence of edema. They also compared the CPTR between corneas with varying clinical grades of Fuchs' dystrophy (86 subjects) and that of normal corneas (142 subjects), and examined the relationship between CPTR and clinical grade.
Interobserver agreement for clinical grading of Fuchs' dystrophy was moderate. In normal corneas, central corneal thickness (CCT) was not correlated with age, peripheral corneal thickness at 4 mm from the center (PCT4) decreased with age, and CPTR increased with age.
CCT and PCT4 were higher in Fuchs' dystrophy than in normal corneas. Furthermore, the CPTR was higher in advanced Fuchs' dystrophy than in mild and moderate Fuchs' dystrophy, which in turn was higher than in normal corneas. Finally, CPTR was highly correlated with clinical grade of Fuchs' dystrophy, was repeatable (median coefficient of variation, 1.3 %), and provided excellent discrimination between Fuchs' dystrophy and normal corneas (area under the receiver operator characteristic curve, 0.93).
The authors conclude that CPTR was excellent at distinguishing between normal corneas and corneas with Fuchs' dystrophy, unlike CCT measured by ultrasound, and could be an objective measure of disease severity in research studies. However, prospective long-term studies are needed to demonstrate the usefulness of the CPTR as a metric for monitoring disease progression and predicting when corneas with Fuchs' dystrophy may require keratoplasty. Additional studies also are required to determine if CPTR is a useful metric for assessing causes of corneal edema other than Fuchs' dystrophy.