Visual severity scale for patients with severe motor and intellectual disabilities and cerebral visual impairment : reliability and validity.

Abstract

[Introduction] Evaluating visual function in patients with severe motor and intellectual disabilities (SMID) and cerebral visual impairment (CVI) is extremely challenging. The aim of this study was to develop a convenient non-motor visual functional scale for this population. [Method] The scale comprised eight subscales extracted mainly from normal visual development studies before three months postnatally. Fifty healthcare professionals and special-needs education teachers participated in the weighting of items. Severity of visual impairment was ranked using 32 pieces of virtual patient card, and conjoint analysis was undertaken for the obtained data. Validity of the scale was examined by comparing the score of the scale and achromatic and chromatic contrast sensitivity functions (CSFs) obtained by observation of optokinetic nystagmus (OKN) to drifting gratings in 24 patients with SMID and CVI or non-CVI (median age, 16 years 6 months; range, 3-57 years). Inter-rater reliability among 34 healthcare professionals and special-needs education teachers was confirmed using intraclass correlation coefficient (ICC) in evaluating agreement between video judgments. [Results] Total score of the scale demonstrated a moderate significant correlation with composite CSFs (r=-0.50, p<0.05). Inter-rater reliability was moderate (ICC=0.59, p<0.05). [Discussion] This scale may be a useful tool in occupational therapy for patients with SMID because it offers moderate validity and reliability and it is readily available, with no requirement for special equipment.