Pupillary Responses to High-Irradiance Blue Light Correlate with Glaucoma Severity.

PURPOSE: To evaluate whether a chromatic pupillometry test can be used to detect impaired function of intrinsically photosensitive retinal ganglion cells (ipRGCs) in patients with primary open-angle glaucoma (POAG) and to determine if pupillary responses correlate with optic nerve damage and visual loss. DESIGN: Cross-sectional study. PARTICIPANTS: One hundred sixty-one healthy controls recruited from a community polyclinic (55 men; 151 ethnic Chinese) and 40 POAG patients recruited from a glaucoma clinic (22 men; 35 ethnic Chinese) 50 years of age or older. METHODS: Subjects underwent monocular exposure to narrowband blue light (469 nm) or red light (631 nm) using a modified Ganzfeld dome. Each light stimulus was increased gradually over 2 minutes to activate sequentially the rods, cones, and ipRGCs that mediate the pupillary light reflex. Pupil diameter was recorded using an infrared pupillography system. MAIN OUTCOME MEASURES: Pupillary responses to blue light and red light were compared between control subjects and those with POAG by constructing dose-response curves across a wide range of corneal irradiances (7-14 log photons/cm(2) per second). In patients with POAG, pupillary responses were evaluated relative to standard automated perimetry testing (Humphrey Visual Field [HVF]; Carl Zeiss Meditec, Dublin, CA) and scanning laser ophthalmoscopy parameters (Heidelberg Retinal Tomography [HRT]; Heidelberg Engineering, Heidelberg, Germany). RESULTS: The pupillary light reflex was reduced in patients with POAG only at higher irradiance levels, corresponding to the range of activation of ipRGCs. Pupillary responses to high-irradiance blue light associated more strongly with disease severity compared with responses to red light, with a significant linear correlation observed between pupil diameter and HVF mean deviation (r = -0.44; P = 0.005) as well as HRT linear cup-to-disc ratio (r = 0.61; P < 0.001) and several other optic nerve head parameters. CONCLUSIONS: In glaucomatous eyes, reduced pupillary responses to high-irradiance blue light were associated with greater visual field loss and optic disc cupping. In POAG, a short chromatic pupillometry test that evaluates the function of ipRGCs can be used to estimate the degree of damage to retinal ganglion cells that mediate image-forming vision. This approach could prove useful in detecting glaucoma.

Levels of circulating homocysteine, vitamin B6, vitamin B12, and folate in different types of open-angle glaucoma.

OBJECTIVE: To compare the levels of plasma homocysteine (Hcy), vitamin B6 (vit-B6), serum vitamin B12 (vit-B12), and folate in healthy individuals and in patients with normal tension glaucoma (NTG), pseudoexfoliative glaucoma (PXG), or primary open-angle glaucoma (POAG). STUDY DESIGN: A prospective controlled trial. PARTICIPANTS AND METHODS: Forty healthy subjects, 48 patients with NTG, 38 patients with PXG, and 34 patients with POAG were included in the study. Those who used vitamin supplements or medications affecting Hcy and vitamin levels were excluded from the study. The levels of Hcy and vit-B6 were measured by High Performance Liquid Chromatography (HPLC). The levels of serum vit-B12 and folic acid were measured by competitive chemiluminescent enzyme immunoassay (CEI). One-way analysis if variance (ANOVA), analysis of covariance (ANCOVA), and the Tukey honestly significant difference test were used for statistical analysis. RESULTS: The mean Hcy level of the PXG group was 15.46+/-9.27 micromol/L which was significantly higher (P=0.03) than that of the control group. There were no statistical differences in serum vit-B12 and folate levels among control subjects and NTG, PXG and POAG groups (P>0.05). It was found that the mean plasma vit-B6 level was significantly higher in subjects with NTG (P=0.03) and POAG (P=0.025) versus controls. Mean vit-B6 levels in NTG and POAG were 30.50+/-11.29 microg/L and 30+/-12.15 microg/L, respectively. CONCLUSIONS: The plasma level of Hcy was found to be increased only in PXG patients and the plasma levels of vit-B6 were found to increase in the NTG and POAG sample groups. Using homocysteine and vit-B6 levels as the determinants of hyperhomocysteinemia still needs further research.

Why do some people go blind from glaucoma?

Retrospective analysis of patients blinded by glaucoma has revealed a need to educate patients to the significance of premonitory symptoms, to investigate a higher incidence of blindness from open-angle glaucoma among blacks than whites, and to define the goals of therapy in relation to presenting pathology. Responding to this third need, circumstances of patients followed for 20 to 40 years with extensive documentation relating to open-angle glaucoma were analyzed. Some eyes with normal discs and fields were found to tolerate a tension of 30 mm Hg for many years without need of treatment. But, when abnormalities ranging from early glaucomatous cupping to advanced visual field defects were present on initial evaluation, progressive loss of field tended to occur at lower tensions. It appears that the worse the initial condition of the eye, the lower the tension needs to be to prevent further loss or blindness.