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Cord R H Huchzermeyer, Sarah Haubner, Robert Laemmer, Christian Y Mardin, Jan J Kremers; Temporal Contrast Sensitivities are Locally Reduced around 4Hz for L-cone- and around 10Hz for M-cone isolating stimuli in Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3941.
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© ARVO (1962-2015); The Authors (2016-present)
Temporal contrast sensitivity (TCS) is generally reduced in glaucoma patients. Evidence that some retinogeniculate pathways may be more susceptible to glaucomatous damage than others is ambiguous. L- and M-cones feed into the parvocellular and into the magnocellular system; therefore, we hypothesized that TCS to L- and M-cone isolating stimuli may show characteristic changes in glaucoma patients that may be used for improved diagnosis and enhance our understanding of the retinal pathways affected by glaucoma.
Nineteen patients with advanced glaucoma – characterized by cupping of the optic disc and typical visual field defects involving the central visual field – were examined and compared with data from 10 normal subjects.Stimuli for psychophysical measurements were created using an 8-channel LED stimulator with a 2° diameter central circular field and a 13° outer diameter annular surround field (each with four primaries). Sine-wave modulated stimuli were presented in the white surround field (mean luminance 2.7 log phot Td) while subjects fixated the darker steady central field.Isolating stimuli were created for the L- and M-cones using the triple silent substitution paradigm based on the 10° cone fundamentals and the 10° scotopic luminous efficiency. TCS was measured at 1, 4, 10, and 20 Hz. Thresholds were determined using a randomly-interleaved double staircase algorithm. Sensitivity was defined as 1/(contrast at threshold).
The TCSs of glaucoma patients were generally diminished compared to normal. Their TCS curves showed a notch at 4 Hz for the L-cone- and at 10 Hz for the M-cone isolating stimuli where the sensitivities were below the instrument’s gamut for the majority of patients (57.9% for L-cones and 52.6% for M-cones). Similar local minima were not observed in normal subjects.
Psychophysical stimuli based on the silent substitution paradigm may be useful in the study of the mechanisms of glaucomatous optic atrophy. TCS curves of glaucoma patients displayed characteristic alterations with local minima that are possibly caused by destructive interference between the parvo- and the magnocellular pathways.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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