INTEROBSERVER VARIATION IN CLINICAL OPTIC DISC BIOMETRY

This study investigated the inter-observer reproducibility of measurem ents of the optic nerve head as carried out with a clinical optic disc biometer. This instrument employs a modification of indirect ophthalm oscopy to enable measurement of fundus structures. Measurements were m ade independently by two observers on 84 eyes of 47 patients. The medi an inter-observer differences for each measurement were as follows: ma ximum disc diameter, 0.085 mm; minimum disc diameter, 0.080 mm; maximu m cup diameter, 0.098 mm; minimum cup diameter, 0.078 mm; disc area, 0 .225 mm2; neuroretinal rim area, 0.215 mm2. Utilising the above measur ements, the instrument automatically calculates a 'rim index' to take account of variations in disc size. It then interprets the disc as nor mal, suspicious or glaucomatous. The optic disc biometer produced seri ously conflicting interpretations in 8 discs, 7 of which had been judg ed by both observers to have indistinct boundaries of the disc or cup.