Consistency between visual acuity scores obtained at different test distances: theory vs observations in multiple...

Area of Science:

• Ophthalmology
• Clinical Research
• Vision Science

Background:

• Visual acuity (VA) is a key metric in assessing vision, particularly for patients with or at risk of choroidal neovascularization (CNV).
• Standardized testing distances are crucial for reliable VA measurements.
• Inconsistencies in VA scores can impact clinical decisions and trial outcomes.

Purpose of the Study:

• To evaluate the consistency of visual acuity (VA) scores obtained at two different testing distances.
• To identify potential discrepancies in VA measurements in patients with or at risk for choroidal neovascularization (CNV).

Main Methods:

• Analysis of best-corrected VA scores from four distinct randomized clinical trials involving patients with or at risk for CNV.
• Comparison of VA scores measured at two different distances within the same eyes during the same examinations.
• Exploration of the relationship between VA scores and testing distance.

Main Results:

• VA scores measured at closer distances (<2 meters) were systematically lower than those at farther distances across all four data sets.
• Discrepancies ranged from 3.1 to 8.2 letters, depending on the specific study and distances used.
• Factors such as reduced visual angle, macular lesion characteristics, and patient accommodation did not fully explain the observed differences.

Conclusions:

• A consistent finding of lower VA scores at closer testing distances (<2m) was observed in all studies.
• This phenomenon appears to be real and common, as it was also noted in studies with healthy young subjects.
• The results highlight a potential challenge in VA testing that warrants further investigation and consideration in clinical practice and research.