Long- and Short-Term Variability of Perimetry in Glaucoma

Area of Science:

• Ophthalmology
• Visual Neuroscience
• Medical Technology

Background:

• Test-retest variability in visual field testing complicates the accurate assessment of glaucoma progression.
• This variability has short-term (algorithm-dependent) and long-term (true sensitivity fluctuations) components.

Purpose of the Study:

• To quantify algorithm-independent long-term variability in perimetry.
• To differentiate short-term and long-term variability across different levels of visual sensitivity.

Main Methods:

• Modeled short-term variability using frequency-of-seeing curves in 35 glaucoma patients.
• Simulated short-term variability for a 30-presentation algorithm.
• Calculated long-term variability from test-retest data of 137 patients tested 6 months apart.

Main Results:

• Short-term variability increased linearly with visual loss below 28 dB.
• Long-term variability also increased with damage, peaking at 2.4 dB standard deviation at 21 dB sensitivity.
• Above 30 dB, long-term variability was negligible, with observed test-retest variance lower than simulated short-term variability.

Conclusions:

• Both short-term and long-term variability increase with visual field damage.
• Long-term variability is a significant factor in glaucoma progression assessment.
• Improving perimetry algorithms alone cannot fully mitigate long-term sensitivity fluctuations.