Determination of absolute size of fundus objects.
BACKGROUND
Creating multiple beam interference fringes on the retina using the "retina fringe projector" (RFP) provides us with a scale which can be used to determine the absolute size of objects at the fundus.


METHODS
The procedure is tested on an model eye, the optical parameters of which are varied in order to simulate different refraction conditions. The RFP was used to determine the size of a known object at the model fundus; the result was then checked against the real value of the object. In a second series of measurements, the RFP fringes were included in fundus photos of 52 patients with varying levels of ametropia, taken at the University Eye Clinic in Jena using the FF450 fundus camera (manufacturer: Carl Zeiss Meditec AG) for diagnostic purposes. The distance between the fringes was determined using both the RFP and the Littmann method.


RESULTS
The differences to the real value of the fundus size of a known object deviated on average by 1 to 2%, and always remained under 3% in the model eye. A very good correlation between RFP and Littmann methods results could be found in the clinical part of the study. The resulting deviations are below 2.5%.


CONCLUSIONS
Integration of a RFP in a fundus camera permits measurement of absolute values of the retina, regardless of the type of observation or documentation. Knowing the real size of fundus objects holds a potential in many clinical classification scales of fundus objects such as drusen or vessels, or in optimizing photodynamic therapy spot size measurement.
Dawczynski
Jens
J
Department of Ophthalmology, University Hospital Jena, Bachstr. 18, 07749 Bachstraße 18, 07740, Jena, Germany. jens.dawczynski@med.uni-jena.de
Gebhardt
Michael
M
Mohr
Thomas
T
Koschmieder
Ingo
I
Rassow
Bernhard
B
Schubert
Anne-Kathrin
AK
Strobel
Jürgen
J
D001699:Biometry / Q000295:instrumentation; D005654:Fundus Oculi; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D010781:Photography / Q000295:instrumentation*; D012858:Size Perception
J Physiol. 1965 Dec;181(3):576-93
5880378
Klin Monbl Augenheilkd. 1982 Apr;180(4):286-9
7087358
Invest Ophthalmol Vis Sci. 1989 Nov;30(11):2314-9
2807789
Br J Ophthalmol. 1998 Jun;82(6):643-9
9797665
Klin Monbl Augenheilkd. 1988 Jan;192(1):66-7
3352190
Ophthalmic Physiol Opt. 1988;8(1):53-9
3047630
Ophthalmic Physiol Opt. 1992 Oct;12(4):485-90
1293539
Graefes Arch Clin Exp Ophthalmol. 1992;230(1):24-8
1547963
Br J Ophthalmol. 1988 Mar;72(3):228-30
3355810
Graefes Arch Clin Exp Ophthalmol. 1994 Jun;232(6):361-7
8082844
Acta Ophthalmol Scand Suppl. 1995;(216):1-12
8963827
Albrecht Von Graefes Arch Klin Exp Ophthalmol. 1973 Apr 7;187(1):61-6
4541249
Invest Ophthalmol Vis Sci. 1983 Feb;24(2):169-74
6826321
Adv Ophthalmol. 1977;34:116-42
868684