Reviewed by Augustine Bannerman and Filippos Vingopoulos, MD
A rapid test with active learning algorithms could offer physicians a new way to measure contrast sensitivity (CS) when evaluating patients before cataract surgery, according to Augustine Bannerman, an undergraduate research assistant, and Filippos Vingopoulos, MD, both of the Harvard Retinal Imaging Laboratory at the Massachusetts Eye and Ear in Boston.
“Contrast sensitivity function [CSF] Testing can be a valuable adjunct to standard cataract assessment to improve surgical decision-making, particularly in patients with subjective visual problems despite good visual acuity [VA]’ said Bannerman.
According to Bannerman, surgical decision-making prior to cataract surgery is based on subjective visual impairment and not on objective, clinically measured results of visual function.
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With this in mind, Bannerman and his colleagues took previous research on the strong correlation between CS and subjective visual impairment and vision-related daily activities, and then went a step further to circumvent the current imperfections that limit the clinically used CS tests.
Researchers enrolled 167 eyes, including 58 eyes with cataracts, 77 control eyes and 32 eyes with pseudophakia, in a study to characterize CSF in cataract patients and patients with pseudophakia using a novel CSF test with active learning algorithms.
Participants’ vision was assessed using the Manifold Contrast Vision Meter (Adaptive Sensory Technology).
Visually relevant cataract was defined as 2+ nuclear sclerosis and a VA greater than 20/50, pseudophakic patients had posterior segment intraocular lenses, and controls had no greater than 1+ nuclear sclerosis and no visual symptoms.
The primary endpoints were area under log-CSF (AULCSF), contrast acuity (CA), and CS thresholds at 1, 1.5, 3, 6, 12, and 18 cycles/degree (cpd).
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The so-called rapid CSF test uses “a Bayesian active learning algorithm that maximizes information extraction over a very large set of possible combinations of contrast and spatial frequency, ultimately producing a curve separating visible from invisible stimuli with great test-related repeatability and test times of 2 to 5 minutes per eye,” Bannerman said.
The researchers reported that the presence of cataracts was associated with a significantly decreased AULCSF (P = 0.04) and contrast threshold at 6 cpd (P = 0.01) compared to controls.
An interesting finding according to Bannerman was that even in a subset of cataract eyes with very good VA (≥ 20/25), the contrast threshold at 6 cpd was still significantly reduced (P = 0.02).
The 6-cpd spatial frequency appears to be important, he said: The lower or higher spatial frequencies were not affected by cataracts.
These contrast sensitivity deficits found with the rapid CSF test would have been missed with the traditional Pelli-Robson contrast test, he added.
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Pseudophakic eyes had no significantly different contrast results compared to controls.
The rapid CSF test discovered disproportionately significant contrast deficits at 6 cpd in the various metrics evaluated in eyes with cataracts and even those with good visual acuity, the authors noted.
“CSF testing can be a valuable adjunct to standard cataract assessment to improve surgical decision-making, particularly in patients with subjective visual problems despite good visual acuity,” they said.
A possible area of study could be to perform the rapid CSF test in pseudophakic eyes with different types of intraocular lenses, the authors said.
An ongoing study will demonstrate the improved CSF after cataract surgery and compare this to an improvement in visual acuity.
This article is an adaptation of Bannerman’s presentation at the Association for Research in Vision and Ophthalmology’s 2021 Virtual Annual Meeting. Bannerman has no financial interest in this issue.