ETDRS-style distance visual acuity charts for Indigenous Canadians: development and validation using Canadian...

To develop and validate a logMAR Early Treatment Diabetic Retinopathy Study (ETDRS)-style visual acuity chart imprinted with Canadian Aboriginal Syllabics (CAS) optotypes.

Prospective, nonrandomized, within-subject analysis.

22 Indigenous patients from the Ullivik residence (Montreal, QC) for Inuit patients who were able to interpret Latin and CAS characteristics.

Python and LaTeX scripts were created to generate PDFs of standard ETDRS charts, which could be readily modified for alphabet (CAS or Latin), font, and optotype sizing. We used CAS characters that were preserved across Cree, Ojibwe, and Inuktitut languages. A 60" television screen (4K resolution) was used to display the eye charts to scale. For each subject, the best-corrected visual acuity (BCVA) of each eye was assessed on each chart (4 measurements per patient).

The median difference between visual acuities (logMAR) acquired by the Latin and CAS charts was 0 (Q1: -0.08; Q3: 0). Band-Altman analysis revealed a bias of -0.01 (SD: 0.03), which was near zero (indicating favourable agreement), and one outlier (of 22 patients), whose deviation was attributed to random error. The visual acuity differences between eye charts were not statistically significant (p = 0.1).

We developed and validated the first CAS-imprinted ETDRS chart for measuring visual acuity. Given its use of preserved characters across Cree, Ojibwe, and Inuktitut languages, this chart has additional applicability to several Indigenous populations in Canada. Future work should develop near reading cards and other methods of optimizing culturally competent eye care for Indigenous patients.