Abstract
Purpose: :
To investigate disorders of eye movements in open angle glaucoma.
Methods: :
Comparative study of saccades, pursuit and a saccade-pursuit sequence on a moving target in 3 groups: 4 patients with open angle glaucoma and a mild visual field defect (mean MD: -5dB, mean age: 51years); 4 patients with open angle glaucoma and an almost normal visual field (mean MD: -0.5dB, mean age: 57 years); and 4 age-matched control subjects (mean age: 54 years). Eye movements were recorded monocularly (right eye for all subjects) at 240hz using an ISCAN ETL-400 system (Burlington, MA, USA).
Results: :
For the saccade task, the mean saccade latency was longer in glaucomatous patients (247 and 259 ms) than in the control group (236ms) (F(2,798)=18, p<10-3). Mean saccade gain was lower in glaucomatous patients with visual field defect (81%) than in patients with almost normal visual field (86%) and in controls (89%) (F(2,798)=13 ; p<10-3). During pursuit, maximum eye speed was faster in both groups of patients (31 et 28°/s) than in controls (21°/s) (F(2,2455)=68, p<10-3). The mean pursuit and gain was similar in the 3 groups (105% for controls, 107% for normal visual field patients, 110% for patients with visual field defect) but speed variability of pursuit was larger in the 2 groups of glaucomatous (10 and 9°/s) than in controls (3°/s) (F(2, 2455)=18, p<10-3). During the saccade-pursuit task the latency of the maximum’s speed of the saccade was longer in the 2 groups of patients (305 and 350ms) than in controls (283ms) (F(2, 1910)=103, p<10-3). Saccade gain was smaller in glaucomatous patients (73 and 75%) than in controls (82%) (F(2, 1910)=23, p<10-3). Speed variability of pursuit following the saccade was larger in glaucomatous patients (7 and 8°/s) than in controls (3°/s) (F(2, 1910)=54, p<10-3).
Conclusions: :
The larger variability and inaccuracy of eyes movements in glaucomatous patients suggest an alteration of eye movement control in this condition. These patients had lower performances in the saccade-pursuit task, which required analysis of the target speed in the peripheral visual field. Glaucoma also affects high order visuo-motor functions, even if visual fields are preserved; suggesting that eye movements may be affected early in the disease
Keywords: eye movements: saccades and pursuits • optic nerve • ocular motor control