Clinical Studies on Dark Adaptation: with Particular Reference to Carotid Artery Disease

Detta är en avhandling från Department of Ophthalmology, Malmö University Hospital, S-205 02 Malmö, Sweden

Författare: Ulf Havelius; Lunds Universitet.; Lund University.; [2000]

Nyckelord: MEDICIN; MEDICINE; photoreceptors polycythemia phlebotomy ocular blood flow headache dilation lag dark adaptometry dark adaptation color Doppler imaging carotid artery stenosis carotid artery disease carotid endarterectomy pupil pupillometry retinal blood flow Ophtalmology Oftalmologi;

Sammanfattning: Purpose: To study dark adaptation in patients with symptomatic carotid artery disease or polycythemia before and after treatment. This necessitated determinations of pupillary changes as such may influence the findings. To determine whether changes in the retinal blood flow in light and darkness occur in healthy humans. Methods: Repeated automatic dark adaptometry was recorded monocularly in 21 consecutive patients scheduled for first-time carotid endarterectomy and in 10 patients with polycythemia. All patients were studied before and after treatment. Analogue investigations were performed in 31 healthy control subjects. The systolic and diastolic blood flow velocities were measured by color Doppler in the ophthalmic and the central retinal arteries in 12 healthy individuals in light and darkness. The pupillary diameter was measured under defined conditions of darkness in all patients and control subjects. Photographic pupillometry was used in 21 patients with carotid artery disease before and after endarterectomy. Results: Dark adaptation was markedly impaired in both categories of patients compared to the control subjects. After carotid endarterectomy in the carotid patients and normalization of the red cell count, hematocrit and hemoglobin in the polycythemic patients, dark adaptation was markedly improved. There was no significant change in dark vision in the control subjects. The results could not be explained by any change in the pupillary diameter. In healthy individuals the systolic and diastolic flow velocities in the central retinal artery were markedly increased in darkness. Conclusions: These findings indicate a sustained but reversible neuronal hypofunction secondary to compromised macro- and microcirculation. Furthermore, the results indicate that darkness is associated with increased blood flow velocity in the central retinal artery, probably reflecting increased metabolic demands by the photoreceptors.

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