Posters

Development and validation of the 'Keratoconus end-points assessment questionnaire', a disease-specific instrument for evaluating subjective emotional distress and visual function through rasch analysis

Poster Details

First Author: K.Balparda COLOMBIA

Co Author(s):    T. Herrera-Chalarca   L. Silva-Quintero   S. Torres-Soto   C. Vanegas-Ramírez           

Abstract Details

Purpose:

Keratoconus is a disease characterized by progressive distortion of the corneal anatomy, coupled with a decrease in vision. Assessing Quality of Life (QoL) in Keratoconus is important. So far, no instrument in the world has been designed to evaluate both visual function and emotional distress in this population. The purpose of the following study is to develop and validate the “Keratoconus End-Points Assessment Questionnaire” (KEPAQ) in a population of ectatic patients, the very first disease-specific scale to measure emotional latent traits in Keratoconus.

Setting:

Clínica de Oftalmología Sandiego, a private practice hospital in Colombia

Methods:

A last generation, Rasch Analysis method was used for scale validation. First, a number of focus groups were carried out in order to create a pool of potential items. Then, a series of processes (such as “Content Validity Index”) were carried out to develop a prior, 20-questions version of the KEPAQ. Then, a study including 364 Keratoconus patients was performed, followed by a careful Rasch Analysis to validate and optimize both subscales (Emotional Compromise, KEPAQ-E, and Functional Compromise, KEPAQ-F).

Results:

A total of 364 patients with a confirmed diagnosis of Keratoconus were included for the Rasch Analysis. Mean age was 29.84 ± 9.96 years. 12.6% had a history of keratoplasty, 46.0% of corneal rings, and 31.3% of cross-linking. For both subscale, misfitting items were removed until no misfitting was determined. For the final version of the KEPAQ-E subscale, person separation index and person number of strata were 2.43 and 3.57 respectively. For the final version of the KEPAQ-F subscale, person separation index and person number of strata were 3.19 and 4.59 respectively. Both sub scales showed an excellent person reliability.

Conclusions:

The KEPAQ is a robust scale, developed and validated through the latest theoretical models. It shows excellent psychometric properties which render it extremely useful for both clinical and research use. To date, the KEPAQ is the only disease-specific scale worldwide to evaluate both functional and emotional compromise in Keratoconus patients.

Financial Disclosure:

None