Is randomisation necessary for measuring defocus curves in pre-presbyopes?

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Defocus curves are essential for assessing visual clarity with presbyopic corrections.
• Accommodating intraocular lenses (IOLs) aim to restore the eye's natural focusing ability.
• Standardizing measurement techniques is crucial for reliable subjective amplitude of accommodation data.

Purpose of the Study:

• To determine if randomizing letter sequences and lens presentation order impacts defocus curve measurements.
• To identify optimal protocols for measuring subjective visual range in presbyopic patients.

Main Methods:

• Defocus curves were measured across a +2.00DS to -2.00DS range in 18 pre-presbyopic subjects.
• Six combinations of sequential/randomized lens progression and non-randomized/randomized letter sequences were tested.
• Visual acuity was assessed using a computerized logMAR chart at 6 meters.

Main Results:

• A statistically significant difference in defocus curves was observed (ANOVA, p<0.05).
• The combination of non-randomized letters and sequential negative-to-positive lens progression significantly altered results (p<0.01).
• Randomizing either letters or lens order, or both, did not produce statistically significant differences compared to each other (p>0.05).

Conclusions:

• The combination of non-randomized letters and sequential lens progression should be avoided when measuring defocus curves.
• Individual randomization of letters or lens order does not significantly affect subjective amplitude of accommodation measurements.
• Standardized, randomized protocols ensure reliable defocus curve data for presbyopic corrections.