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THE VARIATION AND COVARIATION OF CUP AND DISC DIAMETERS
Author(s) -
BENGTSSON BO
Publication year - 1976
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.1976.tb01801.x
Subject(s) - magnification , fundus (uterus) , optic disc , variation (astronomy) , optics , anatomy , refraction , optic cup (embryology) , population , optic nerve , materials science , mathematics , ophthalmology , biology , physics , glaucoma , medicine , astrophysics , biochemistry , environmental health , gene , eye development , phenotype
The variation and covariation of cup and disc diameters were studied in a material derived from a population survey and consisting of 2,334 fundus photographs from as many eyes in 1,322 subjects. A simple device was used to facilitate focusing of the camera. The colour slides were projected on to a screen at a fixed distance and measured on ruled paper. The effect of refraction on the magnification in the eye‐camera system was compensated by the use of a simple correcting factor. Some apparently quite normal discs, nevertheless, had an area more than four times larger than that of other equally normal ones. The sizes of discs and cups co‐varied, however, to a surprisingly great extent (r = 0.8) and changes in disc diameter were in general parallelled by similar changes in cup diameter. The amount of tissue in the optic nerve head therefore varied somewhat less than the disc size. Cup diameters were widely dispersed, unevenly distributed and heavily dependent on disc size. The “average rim breadths”, on the other hand, were much less dispersed, normally distributed and independent of the disc diameter. By taking the covariation of cup and disc diameters into account the detection of any enlargement or diminution of the optic cup ought to be facilitated.