To date two different instruments are commercially available to measure retinal oxygen saturation and retinal vessel diameters: Dynamic Vessel Analyzer (DVA) and Oxymap. Retinal oxygen saturation analysis is based on spectroscopic evaluation of retinal fundus images. Up to now no data comparing both instruments for the measurement of retinal oxygen saturation and vessel diameter are available in the literature.

Study objectives: To compare retinal oxygenation and retinal vessel diameters in healthy subjects and patients with diabetic retinopathy or retinal vein occlusion between 2 commercially available systems (DVA, Oxymap T1)

Study design: Open pilot study

Study population:

30 healthy volunteers, age 18-80 years 30 type 2 diabetic patients with mild or moderate non-proliferative diabetic retinopathy, age 18-80 years 30 patients with retinal vein occlusion, age 18-80 years

Topically administered medication:

Tropicamide (Mydriaticum "Agepha"®, Agepha, Vienna, Austria), dose: 1-2 drops per study day for dilation of the pupil Oxybuprocainhydrochloride combined with sodium fluorescein (Thilorbin®, Alcon Pharma GmbH, Freiburg, Germany), dose: 1 drop in one eye for measurements of intraocular pressure Nonylacidvanillylamide combined with Nicotinic-acid--ß-butoxyethylester (Finalgon®, Boehringer Ingelheim RCV GmbH & Co KG, Vienna, Austria): topical on the earlobe

Methods:

Dynamic vessel analyzer Oxymap T1 Blood pressure and pulse rate measurement Applanation tonometry Oxygen and carbon dioxide partial pressure measurement in arterialized blood from earlobe

Main outcome variables:

Difference of oxygen saturation of retinal vessels between DVA and Oxymap T1

The motive for this investigation is to compare data between 2 commercially available instruments for the measurement of retinal oxygen saturation and retinal vessel diameter in healthy subjects as well as in patients with ocular disease associated with altered retinal oxygenation. Comparative data from both systems are currently not available. Data from this study will allow the comparison of studies performed with different systems. All oxygen measurement procedures are non-invasive and painless. Hence, the risk/benefit ratio appears to be acceptable.

Inclusion criteria healthy volunteers

• normal ophthalmic findings, ametropia < 3 dpt
• men and women aged between 18 and 80 years

Exclusion Criteria:

Any of the following will exclude a subject from the study:

• participation in a clinical trial in the 3 weeks preceding the study
• symptoms of a clinically relevant illness in the 3 weeks before the first study day
• pregnancy