Development and Validation of the First Canadian Aboriginal Syllabics Visual Acuity Chart

 Author Block: Nishaant Bhambra ¹, Jobanpreet Dhillon², Sidrat Rahman¹, Christian El-Hadad¹.  ¹Faculty of Medicine, McGill University, ²Department of Ophthalmology, University of Ottawa.

Author Disclosure Block: N. Bhambra:   Membership on advisory boards or speakers’ bureaus; Name of for-profit or not-for-profit organization(s); Valeo Pharmaceuticals. Membership on advisory boards or speakers’ bureaus; Description of relationship(s); Advisory board.  J. Dhillon:  None.  S. Rahman:  None.  C. El-Hadad:  None.

Abstract Title: Development and Validation of the First Canadian Aboriginal Syllabics Visual Acuity Chart

Abstract Body: Purpose:  We present here the development and validation of the first visual acuity chart written using Canadian Aboriginal Syllabic (CAS) letters, for use with Inuktitut, Cree, and Ojibwe-reading patients.   Study Design:  Prospective, non-randomized, within-subjects cross-sectional study.   Methods:  Visual acuity (VA) charts were made in Latin using standard Snellen optotypes (C, D, E, F, L, O, P, T, and Z) and CAS using letters conserved across the Inuktitut, Cree, and Ojibwe (ᐱ, ᑎ, ᑭ, ᒧ, ᒋ, ᒥ, ᑯ, ᒧ, and ᔨ) alphabets. Fonts were chosen to be similar in style between both charts, with each in bolded, sans serif font. Each VA chart was developed to be used at distance of 3 meters, with 11 lines of text and acuities ranging from 20/200 to 20/10. Optotype width of the 20/20 line was calculated using the formula,  w = 2dtan(θ/2)  where  d  equals the distance used (3 m) and  θ  equal to the subtended angle of 5 arcminutes. For further confirmation, optotype width was compared to existing and validated Snellen charts. Charts were created using LaTeX to ensure proper formatting and optotype sizing. Charts were exported as PDF files and confirmed to be displayed to scale on an iPad Pro. Both charts were displayed with the iPad Pro’s brightness at its highest setting (1600 cd/m²). 20 Latin and CAS-reading participants were recruited from Ullivik, a residence in Montreal for Inuit patients from Nunavik. Each patient had their best-corrected visual acuity (BCVA) for each eye measured using the Latin and CAS charts sequentially, for a total of 40 eyes. The technician recording BCVA measurements was provided with transliterated sounds of each CAS letter. BCVA scores were then converted to logMAR scores for statistical and correlation analyses.   Results:  Median BCVA was 0.04 (Range = -0.06 to 0.54) and 0.07 logMAR (0 to 0.54) on the Latin and CAS charts respectively. Median difference between CAS and Latin charts was 0 logMAR (-0.08 to 0.1). Mean ± SD difference between charts was 0.01 ± 0.03 logMAR. Pearson r correlation between groups was 0.97. Two-tailed paired t-test between groups was p=0.26.   Conclusions:  We demonstrate here the first visual acuity chart in CAS, for use with patients who read Inuktitut, Ojibwe, or Cree. The CAS VA chart has highly similar visual acuity measurements to the Latin Snellen chart, with a high correlation between BCVA results. Differences in measurement may be due to patient fatigue, as patients were tested on the Latin chart followed by the CAS chart in each eye. Testing VA for Indigenous patients in their native alphabet may provide culturally sensitive care and more accurate measurements.