Predominant affection of the blue cone pathway in Parkinson's disease

Abstract

Luminance contrast sensitivity and colour contrast thresholds were determined in 26 Parkinson patients and 17 normal controls of comparable age. They were psychophysically tested with a colour monitor system. Stimuli consisted of Gaussian enveloped luminance modulated or colour modulated (protan and tritan axis) vertical sine wave gratings with a spatial frequency of 1 cycle/degree. The stimuli subtended 4 degrees in diameter. Thresholds were determined using a two alternative forced choice method. Three different experimental conditions were explored: the detectability of stationary gratings, of moving gratings at velocities of 0, 2.5 and 5.0 cycles/s, and the detectability of horizontal square wave displacement at a frequency of 5 Hz for gratings of specified contrast levels. Intergroup differences were evaluated using two-tailed t tests with Satterthwaite corrections. Consistent and significant differences between normals and patients were found for tritan stimuli in the static and both dynamic conditions, and for luminance contrast stimuli in the displacement condition. Protan stimuli were much less apt to detect differences between the groups. We conclude that the retinal deficit of dopamine in Parkinson's disease is reflected in diminished centre/surround inhibition and that these changes are primarily apparent when vision is tested along the tritan axis, because blue cones are sparsely distributed.

Visual hallucinosis: The major clinical determinant of distorted chromatic contour perception in Parkinson's disease

“…In our present study, especially the colours "bright-blue" and "bright-yellow" at a temporal frequency of 10/s showed a significant reduction in CFT in patients as compared to controls, while multivariate statistical analysis revealed abnormal CFT in PD with respect to all colours. The prominent reduction in CFT for the "bright-blue" and "bright-yellow" stimulus is compatible with recent reports about a predominant affection of the tritanop pathway in PD (Haug et al, 1995). The pathoanatomical basis of the general visual dysfunction in PD is unclear.…”

Assessment of Colour Vision in Epileptic Patients Exposed to Single-Drug Therapy

“…It is well established that when retinal receptor cells and their synapses are involved in any disease [7, 8, 9], the deficit in colour perception is in the blue axis.…”

The possible role of retinal dopaminergic system in visual performance

“…The predominant affection of the blue-cone pathway in PD was shown by Haug et al (1995) in a study using foveal and parafoveal (eccentricity ¼ 101 laterally in the nasal field) presentations of combinations of CS and colored stimuli. Luminance CS and color contrast thresholds were psychophysically determined in PD patients (mean age 64.579.9 yr) and normal controls of comparable age.…”

“…Some studies searched for neurochemical or morphological correlates to visual dysfunction, in vitro as well as in vivo, in animal and human studies (Bodis-Wollner and Tagliati, 1993;Masson et al, 1993;Djamgoz et al, 1997). Others presented subjects with rigorous, retinal or cortical biased stimuli and tests, differentially devoted to the testing of the activity of these regions, in order to relate specific visual dysfunctions to deficits in specific neuronal substrates, like orientated stimuli (Regan and Maxner, 1987), dynamic stimuli (Masson et al, 1993), visuo-spatial tests (Levin et al, 1987), specific color discrimination (Haug et al, 1995), perceptual speed tests (Amick et al, 2003), visual backward masking (Schechter et al, 2003), and Vernier acuity tests with different dimensions (Keri et al, 2004). Also, stimuli were presented to different areas of the retina , in order to target specific groups of cells involved in specific visual functions and deficiencies had been compared between eyes in PD (Bodis-Wollner et al, 1982).…”