Timed instrumental activities of daily living tasks in adults with irreversible vision impairment: validation to visual function and self-report

Background: Instrumental activities of daily living (IADL) are typically self-reported ability to perform complex tasks vital for independent living. There is a need for a complementary objective, performance-based approach especially in tracking outcomes in visual rehabilitation for patients with irreversible vision impairment ("low vision"). Our goals are: (1) To describe the validity of timed performance of instrumental activities of daily living (timed IADL or TIADL) tasks in individuals with irreversible vision impairment, by examining its association with visual function (visual acuity, contrast sensitivity, visual field), (2) To explore the correlation between TIADL and self-reported IADL.

Methods: Twenty TIADL tasks were administered to 88 patients (median age 63.3 years, IQR 37.4-78.0) recruited from the UAB Department of Ophthalmology, Callahan Eye Hospital Clinics. An average Z-score incorporating time and accuracy of task completion was constructed. Minor accuracy errors were penalized 1 standard deviation from their calculated Z-score and major accuracy errors were assigned maximum allotted time. Linear regression was used to analyze the association between TIADL score and measured visual acuity (Early Treatment Diabetic Retinopathy Study, ETDRS chart), contrast sensitivity (Pelli-Robson), and binocular visual field (Esterman) with an unadjusted model and an adjusted model accounting for age, comorbidities, and depression scale (Center for Epidemiological Studies Depression, CES-D). Pearson correlation was used to estimate the correlation between TIADL and IADL.

Results: Increased time to task completion was associated with decreased visual function. Each decreased line of ETDRS read was associated with an increase of 0.002 (95% CI 0.001, 0.002) Z-score (P < 0.01). A decreased ability to discern each Pelli-Robson letter was associated with an increase of 0.26 (95% CI 0.19, 0.33) Z-score (P < 0.01). For each less Esterman target identified, there was an increase of 0.01 (95% CI 0.003, 0.02) Z-score. Self-reported IADL and TIADL were correlated for reading tasks such as newspapers, nutrients on food can, and microwave timer (P < 0.05).

Conclusions: Longer time to perform TIADL is associated with decreased visual acuity, contrast sensitivity, and binocular visual field. TIADL and self-reported IADL are significantly correlated for reading tasks providing an accurate, complementary outcome measure in clinical practice and research.