OPTOMETRY · SEMESTER 2
Additional Study Notes: Visual Acuity Recording and Interpretation
Visual Optics and Assessment
Additional Study Notes — newly authored explanations and examples. These sections supplement the supplied course material.
Learning objectives
Convert common acuity notations, document test conditions and distinguish a visual-acuity result from a complete eye examination.
Snellen, decimal and logMAR: original examples
For a Snellen fraction d/D, decimal acuity is d divided by D. MAR is its reciprocal, and logMAR = log10(MAR), for the corresponding angular-resolution notation.
6/6 gives decimal 1.0, MAR 1 and logMAR 0.00. 6/12 gives decimal 0.5, MAR 2 and logMAR approximately 0.30. 6/60 gives decimal 0.1, MAR 10 and logMAR 1.00. Better acuity can have a negative logMAR value. These conversions do not make different chart designs or scoring methods identical.
Recording conditions
Record the eye, chart and test distance; whether the result is unaided, with habitual correction, best corrected or through a pinhole; and any deviations from the normal testing method. Distinguish monocular from binocular measurements. Record near acuity with its chart notation and working distance.
Ensure the patient understands the task and cannot look around the occluder. Keep illumination and chart distance appropriate. Use a suitable matching or alternative chart where literacy or communication makes letter naming unsuitable. Repeat an unexpected result after checking instructions, correction, occlusion and setup.
Clinical interpretation
Improvement through a pinhole can support an optical contribution to blurred vision, but it does not by itself establish a diagnosis or exclude ocular disease. A person with good central acuity may still have a field defect, binocular problem or ocular disease. Interpret acuity with the case history and other relevant examination findings.
If the patient cannot identify the largest optotype, follow the test protocol for shorter distances and document what was actually tested. Counting fingers, hand movements and light perception are descriptive findings and should not be casually converted into a precise Snellen fraction.
Study References
- Source notes: Visual Acuity Assessment; Clinical Optometric Procedures, Chapter A3
External references checked 13 September 2026. Worked numerical examples and teaching activities are original.
