Abstract
Purpose :
The evolution of keratoplasty from penetrating to endothelial grafts to novel future therapies will continue to alter the threshold, outcomes and safety profile of treatment of patients with Fuchs endothelial corneal dystrophy (FECD). In order to compare diverse interventions, the measurement of patient-reported visual disability in FECD is important. In this study, we validated a new patient-reported visual disability questionnaire, the Visual Function and Corneal Health Status (V-FUCHS) instrument, in FECD before or after endothelial keratoplasty (EK).
Methods :
V-FUCHS was developed based on patient interviews, expert consultations, and pretesting. The final instrument was completed by subjects with a range of severity of FECD (n=41), post-EK for FECD (n=70), and normal corneas (n=28); subjects were phakic or pseudophakic. Psychometric methods of classic test theory were applied to estimate reliability and validity, including testing V-FUCHS against Catquest-9SF, a cataract-specific visual disability questionnaire, administered to the same subjects. Ordered polytomous Rasch-based partial credit models and item response theory diagnostics were used to define the response patterns.
Results :
Median age of subjects was 70 years (range, 38–98); 61% were female. Exploratory factor analysis among FECD and post-EK subjects showed two independent factors of visual disability: 7 items related to visual acuity, and 8 items related to glare/diurnal variation. Retest reliability was substantial (ICC≥0.82, both factors). Among all subjects, the visual acuity factor was strongly correlated with mean Catquest-9SF score (r=0.72, p<0.001, n=97). The glare/diurnal variation factor increased with FECD severity (p<0.001, n=69) and was higher in FECD than normal (p<0.001), independent of age. Diagnostics revealed that both factors were well calibrated and met Rasch model expectations.
Conclusions :
V-FUCHS was valid and reliable in assessing visual disability in FECD and after EK. Glare and diurnal variation in vision were FECD-specific disabilities that correlated with disease severity. V-FUCHS may be useful in clinical practice and research for patient-reported outcomes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.