Carbonic anhydrase inhibition increases retinal oxygen tension and dilates retinal vessels.
BACKGROUND
Carbonic anhydrase inhibitors (CAIs) increase blood flow in the brain and probably also in the optic nerve and retina. Additionally they elevate the oxygen tension in the optic nerve in the pig. We propose that they also raise the oxygen tension in the retina. We studied the oxygen tension in the pig retina and optic nerve before and after dorzolamide injection. Also the retinal vessel diameters during carbonic anhydrase inhibition were studied.


METHODS
A polarographic oxygen electrode was placed transvitreally immediately over the retina or the optic disc in anaesthetised pigs. The oxygen tension was recorded continually and 500 mg dorzolamide was injected intravenously. Retinal vessel diameters were analysed from monochromatic fundus photographs taken before and after injection of dorzolamide.


RESULTS
Baseline retinal oxygen tension (RPO2) was 3.34+/-0.50 kPa (mean +/- SD, n=6) and baseline optic nerve oxygen tension (ONPO2) was 3.63+/-1.00 kPa. RPO2 was increased by 0.36+/-0.11 kPa (n=6, P=0.025) and ONPO2 by 0.73+/-0.34 kPa (n=6, P=0.003) 30 min after dorzolamide administration. The retinal arterioles was significantly dilated by 13+/-7% (n=5, P=0.016) and the retinal venules by 12+/-8% (n=5, P=0.030) 30 min after injection of dorzolamide.


CONCLUSIONS
Retinal and optic nerve oxygen tension increased with systemic administration of dorzolamide. The retinal vessels dilated, probably causing increased blood flow inducing the observed increase in RPO2. The increased oxygenation of retina by CAI may offer therapeutic possibilities in ischaemic diseases of the retina and optic nerve.
Pedersen
Daniella Bach
DB
Department of Ophthalmology, 2061, Rigshospitalet, Blegdamsvej 9, 2100 , Copenhagen Ø, Denmark. daniella@dadlnet.dk
Koch Jensen
Peter
P
la Cour
Morten
M
Kiilgaard
Jens Folke
JF
Eysteinsson
Thor
T
Bang
Kurt
K
Wiencke
Anne Kathrine
AK
Stefánsson
Einar
E
D000818:Animals; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage*; D002256:Carbonic Anhydrases / Q000502:physiology*; D007275:Injections, Intravenous; D017736:Ion-Selective Electrodes; D009900:Optic Nerve / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D011048:Polarography; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D012171:Retinal Vessels / Q000502:physiology*; D013449:Sulfonamides / Q000008:administration & dosage*; D013552:Swine; D013876:Thiophenes / Q000008:administration & dosage*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D002257:Carbonic Anhydrase Inhibitors; D013449:Sulfonamides; D013876:Thiophenes; C062765:dorzolamide; D002256:Carbonic Anhydrases; D010100:Oxygen
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