Hidden visual loss in optic neuropathy is revealed using Gabor patch contrast perimetry

Area of Science:

• Ophthalmology
• Neuroscience
• Visual Science

Background:

• Glaucomatous optic neuropathy and multiple sclerosis can affect visual sensitivity.
• Early detection of visual field defects is crucial for managing these conditions.
• Standard visual field testing may not capture all functional losses.

Purpose of the Study:

• To evaluate visual sensitivity in the central visual field using a novel method called contrast perimetry (CP).
• To compare the diagnostic yield of CP with the Humphrey 30-2 visual field test.
• To investigate the nature of visual sensitivity loss in glaucoma suspects and patients.

Main Methods:

• Contrast sensitivity was measured using Gabor stimuli (sinusoidal gratings within a Gaussian aperture) at 1 cycle/degree.
• Stimulus size was varied to assess contrast sensitivity as a function of spatial scale.
• Visual fields were assessed in normal subjects, glaucoma patients, glaucoma suspects, and multiple sclerosis patients without active optic neuritis.

Main Results:

• Normal contrast sensitivity follows an S-shaped curve with stimulus size.
• Patients exhibited two main patterns of loss: those affecting small stimuli predominantly, and those affecting both small and large stimuli.
• Contrast perimetry identified more abnormal visual field quadrants than the Humphrey 30-2 test, even with liberal criteria.

Conclusions:

• Contrast perimetry provides diagnostically useful information on paracentral visual sensitivity.
• Selective losses in primary open-angle glaucoma and some glaucoma suspects may involve spatially broad-band retinal mechanisms, likely involving ganglion cells.
• CP may be a valuable tool for early detection and monitoring of visual field defects in various neurological and ophthalmological conditions.