Authors: Michael T. Kryshtalskyj, Amrit S. Rai, Georges Durr, Dominik W. Podbielski, Iqbal I. K. Ahmed.

Author Disclosure Block: M.T. Kryshtalskyj: None. A.S. Rai: None. G. Durr: None. D.W. Podbielski: Honorarium; Novartis, Allergan. Consultant; Glaukos, Alcon. I.I.K. Ahmed: Speakers Honoraria; Alcon, Allergan, Carl Zeiss Meditec, Johnson & Johnson Vision. Consultant/Consulting Fees; Acucela, Aerie Pharmaceuticals, Alcon, Allergan, ArcScan, Bausch and Lomb, Beaver Visitec, Camras Vision, Carl Zeiss Meditec, Centervue, Ellex, ElutiMed, Equinox, ForSight Labs, Genentech, Glaukos, Gore, Iantech, InjectSense, Iridex, iStar, Ivantis, Johnson & Johnson Vision, KeLoTec, LayerBio, Leica Microsystems, MicroOptx, New World Medical, Omega ophthalmics, PolyActiva, Sanoculis, Santen, Science Based Health, Sight Sciences, Stroma, TrueVision, Vizzario. Research grant/support; Aerie Pharmaceuticals, Alcon, Allergan, Camras Vision, Glaukos, Ivantis, Johnson & Johnson Vision, New World Medical, Santen.

Abstract Body:
Purpose: To report a two-and-a-half-year extended validation study of the Iris GAP questionnaire. Previously, we reported the development and preliminary validation of the first patient-reported outcome measure to assess symptoms and iris appearance in patients with iris defects (Iris GAP).

Study Design: Prospective observational study.

Methods: A total of 256 patients were prospectively enrolled and divided into 4 iris defect subgroups: no defect (control, n=73), minor defect (n=80), major defect (n=74), and surgically repaired (n=22). Minor defects included iridotomies and transillumination defects, while major defects included iridodialysis, corectopia, polycoria and aniridia. Age, sex, ethnicity, and lens status were collected. Patients completed the Iris GAP questionnaire, and the glare and driving subscales of the Refractive Status and Vision Profile (RSVP) questionnaire for comparison. Test-retest reliability was studied by having the patient complete the questions two weeks later. Iris Gap is a 12item questionnaire with subscales for symptoms and iris appearance. It uses a 4-point Likert scale from 0-3, with higher scores representing greater symptomatology. Cronbach α and intraclass correlation coefficients (ICC) were calculated to assess internal consistency. One-way ANOVA was conducted to compare scores between groups.

Results: Iris GAP scores ranged from 0-32 with a 97% completion rate. Iris GAP had high test-retest reliability (Cronbach =0.866, ICC=0.953, p<0.0005), demonstrated across symptom subscales (Cronbach =0.852, ICC=0.948, p<0.0005) and appearance subscales (Cronbach =0.833, ICC=0.908, p<0.005). Median time between test and retest was 14 days (95% CI 7.2-20.8 days). Iris GAP demonstrated high discriminant validity between subgroups (one-way ANOVA p<0.0005) indicating that it accurately differentiates between subgroups. In pairwise comparisons, the major defect group had statistically significantly higher scores than any of the other groups (p<0.005 for each). The control and repaired groups had the lowest scores, while the minor defect group had intermediate scores. Nine patients underwent iris repair between tests and had a mean difference of 8.2 ± 6.2 points between their pre-operative and post-operative scores (p=0.004). Iris GAP scores positively correlated with RSVP scores (R =0.73).

Conclusions: In patients with iris defects, Iris GAP can reliably evaluate symptomatology and patient-reported iris appearance. It has strong internal consistency, test-retest reliability, and discriminant and concurrent validity with the RSVP questionnaire.