Elongated sinusoidal stimulus demonstrates a good structure-function agreement across 4 testing locations to identify glaucomatous damage to the macula according to research published in Optometry and Vision Science. 

Researchers sought to refine previous findings on alternative approaches to perimetric testing for macular damage in early glaucoma by evaluating the clinical potential of a custom sinusoidal stimulus as the next generation of perimetry. 

The cohort included 30 patients with glaucoma and 37 age-matched control participants from an ongoing glaucoma study. Participants were selected based on the presence of glaucomatous damage within the macula that was seen on structural measurements, but not on perimetric defect. All participants underwent a comprehensive eye examination and had a best corrected visual acuity (BCVA) of 20/20. 


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Small blob stimulus was used to measure perimetric sensitivities in 68 standard 10-2 locations, and sinusoidal stimulus was used to test 20 patients at 4 perimetric eccentricities. 

Investigators found that perimetric defects were consistent with the structural defects observed on en face nerve fiber bundle images. Among the 37 control participants, the -0.4 log unit criterion was the only one used to identify perimetric defects. For elongated sinusoidal stimulus, 18 of 20 patients had at least 1 location with perimetric sensitivity below the 2.5th percentile. For 20 patients, 82%, 65%, 47%, and 24% of patients had numbers with sensitives below the 2.5th percentile at locations 1 through 4, respectively. 

When the 2.5th percentile was used to define perimetric defect via blob stimulus and elongated sinusoidal stimulus, 17 and 18 patients were found to have perimetric defect. 

After averaging sensitivities for the 4 perimetric locations tested with blob stimuli, investigators found similar results; 5 patients with glaucoma were not identified as having sensitivity below the fifth percentile for controls. 

Study limitations include the relatively small sample size and the use of laboratory equipment with specific features for visual field testing. This protocol can be used in the future as a framework for other studies that apply similar testing protocols. 

“The elongated sinusoidal stimulus…was presented at only 4 perimetric locations, as compared with 58 locations for the small blob stimulus,” the study says. “This is a tremendous reduction in the number of perimetric locations while maintaining a good structure-function agreement.” 

“This demonstrates a potential for this new stimulus in the next generation of clinical perimetry.” 

Reference

Alluwimi MS, Swanson WH, King BJ. A novel stimulus to improve perimetric sampling within the macula in patients with glaucoma. Optom Vis Sci. 2021;98(4):374-383. doi:10.1097/OPX.0000000000001677