Evaluation of an adaptation to the Oxford Cognitive Screen for reduced visual acuity: a cohort study.

Abstract

Background: The Oxford Cognitive Screen (OCS) was specifically designed for acute stroke survivors and to be inclusive of aphasia, neglect, motor impairments. However, reduced visual acuity (VA), including lack of access to required reading glasses, can impact completion rates and performance. The aim of the study was to evaluate contrast enhanced OCS-tasks for completion rates and equivalence to the original version.

Methods: Adult stroke survivors were asked to complete two versions (standard and adapted) of two tasks (broken hearts cancellation and trails) in a randomized order, to determine relative completion rates and equivalency. A bedside vision assessment, completed by an orthoptist was collected, including near and distance VA with required refractive correction if available. Two groups were created based on near VA; normal near VA (≥0.2LogMAR) and reduced near VA (<0.2LogMAR).

Results: Five hundred participants were recruited, 56.8% male, mean age 70.62 years. Mean near VA was 0.278 (SD0.277) LogMAR. The broken hearts and trails tasks were completed by 2.2% (p=0.041) and 0.4% (p=0.791) more participants respectively with the adapted version. Participants completing both versions with good near VA were used to analyze equivalence. All the lower and upper bounds of the two one-sided test of equivalence fell within the range of 0.5SD for all scores, indicating that the means are equivalent. Analysis of impairment detection revealed fair to good agreement.

Conclusion: The adapted version is suitable for stroke survivors with reduced near VA to complete the assessment. In the presence of good VA, the tasks were deemed to be equivalent.