RESPONSE OF RETINAL VESSEL DIAMETERS TO LIGHT
M. F. Tobis, G. E. Lang, W. Vilser, Th. Riemer, G. K. Lang
The Retinal-Vessel-Analyzer (RVA from Zeiss/Jena) is a new ophthalmologic device, which can measure small changes of retinal diameters. Light increases the ocular metabolic activity. The aim of this study was to examine whether the illumination field of RVA provokes detectable effects on retinal vessel diameters.
Methods: Examinations with the RVA were made on major arteries and veins of 12 normal subjects (6 women, 6 men, age: 49.33 ± 18.02 years). In a standardized way retinal vessel diameter over vessel segments of 1 to 2 mm length were analyzed near the papilla in all 4 retinal quadrants. The illumination field of the RVA was used as stimulus. After one minute baseline measurements illumination was interrupted for 3 minutes. This dark-phase was followed by another illumination period of 3 minutes and retinal vessel diameters were measured again. Statistical analysis was performed with the paired t-test.
Results: After the dark-phase the temporal veins showed a dilatation of 0.8% (p < 0.0001) in the first minute. At the end of the measurements these vessels were still dilated (+0.7%, p < 0.0001). The nasal veins showed no significant dilatation (p > 0.05) in the first phase whereas they were constricted at the end of the illumination period (-2.54%, p<0,0001). The temporal arterial diameter increased during the whole illumination phase, 2.1% after one minute (p < 0.0001) and 2.78% at the end (p < 0.0001). In contrast, the nasal arteries showed no significant change (p > 0.05) in the first minute, whereas at the end of the measurement these arteries where constricted (-1.66%, p < 0.0001).
Conclusions: The illumination field of the RVA itself influences the retinal vessel diameters. The changes depend on the type of the vessels (arteries/veins) and their location (temporaVnasal).The light reaction of retinal vessels must be taken into consideration, when vessel diameters are studied.
University Eye Hospital and Department of Ophthalmology, University of Ulm, Germany