Reproducibility of visual acuity assessment in normal and low visual acuity

Area of Science:

• Ophthalmology
• Optometry
• Clinical Measurement

Background:

• Accurate measurement of visual acuity is crucial for diagnosing and monitoring eye conditions.
• Reproducibility of visual acuity tests is essential for reliable clinical assessments and research.
• The ETDRS charts are widely used for visual acuity testing, but their performance across the full acuity spectrum requires evaluation.

Purpose of the Study:

• To evaluate the reproducibility of visual acuity measurements obtained with two versions of the ETDRS chart (ETDRS 1 and ETDRS 2).
• To specifically assess measurement consistency in both high and low visual acuity ranges.
• To compare the performance of ETDRS charts in healthy individuals and patients with various eye disorders, including amblyopia.

Main Methods:

• Visual acuity was measured using retroilluminated ETDRS 1 and ETDRS 2 charts in a pseudorandomized sequence.
• Testing distance was adjusted for lower acuities (1m or 0.4m) with near correction.
• 100 patients and 13 healthy volunteers were tested; at least 3/5 optotypes per line correct were required to pass.

Main Results:

• Mean logMAR values were -0.17/-0.14 (healthy) and 0.55/0.57 (all subjects) for ETDRS 1/ETDRS 2.
• Absolute differences between charts were small (mean +/- SD: 0.051 +/- 0.04 healthy; 0.063 +/- 0.05 all subjects).
• Differences in the low acuity range (logMAR > 1.0) did not significantly exceed those in healthy eyes (p=0.17).

Conclusions:

• Visual acuity measurements using ETDRS charts exhibit good reproducibility across a wide range of visual acuities.
• The reproducibility in the lower visual acuity range is comparable to that observed in individuals with normal vision.
• These findings support the reliability of ETDRS charts for assessing visual acuity, even in challenging low-vision cases.