Videokeratographic anomalies in familial keratoconus.

OBJECTIVE

To analyze videokeratography of relatives of established familial keratoconus (FK) patients to detect low-expressivity keratoconus and improve the diagnosis criteria of forme fruste keratoconus.

DESIGN

Multicenter case-control study.

PARTICIPANTS

Twenty-three families with 55 clinical keratoconus patients, 89 first-degree relatives, 43 other relatives, and a control group of 130 subjects.

METHODS

Videokeratography was performed on both eyes of patients after clinical examination, and corneal maps were analyzed. Statistical comparisons were conducted between first-degree and other relatives and a control population.

MAIN OUTCOME MEASURES: Qualitative (using a 0.5-diopter [D] increment scale) and quantitative analyses of videokeratographs.

RESULTS

Two corneal patterns were overrepresented in the relatives of FK patients: the J and inverted-J form patterns. Results of the quantitative analysis of these suspect patterns showed that the inferior - superior values (reflecting the inferior - superior dioptric asymmetry) were close to 0.8 D and the Srax (relative skewing of the steepest radial axes) was superior to 21 degrees.

CONCLUSION

Our study using topography in clearly established genetic keratoconus families allowed us to detect suspect topographical patterns and brings new data to the difficult task of diagnosing forme fruste keratoconus.