What optic disc parameters are most accurately assessed using the direct ophthalmoscope?

Purpose It has been suggested that over-reliance on the cup-to-disc ratio i s a major factor in the misinterpretation of the optic disc. In spite of th is optometrist assessment of the optic disc tends to be restricted to measu rement of the cup-to-disc ratio and cup depth only. Would interpretation of the disc improve if optometrists were to evaluate other parameters? The ai m of this study was to evaluate the accuracy of optometrist assessment of n ine parameters of the optic nerve head using direct ophthalmoscopy. Methods Eight optometrists evaluated nine parameters of the optic nerve hea d (vertical disc diameter, vertical cup-to-disc ratio, neuroretinal rim con figuration, cup shape, neuroretinal rim colour, vessel path, presence/absen ce of haemorrhage, extent and location of peripapillary atrophy and classif ication of health status of the disc) in 50 eyes of 50 patients using direc t ophthalmoscopy. Intensive training in optic nerve head assessment was giv en prior to assessing the patients. Criteria for evaluation were discussed. The 'gold standard' reference was the classification of the parameters by a consultant ophthalmologist with a special interest in glaucoma. Results Interobserver agreement for vertical cup-to-disc ratio was almost p erfect (mean weighted kappa 0.84). Agreement for neuroretinal rim configura tion, cup shape, haemorrhage and final classification of the disc was good (mean kappa 0.62-0.67). There was moderate agreement for vessel configurati on (mean kappa 0.53). For assessment of peripapillary atrophy, disc size an d neuroretinal rim colour, agreement was fair (mean kappa 0.22-0.34). Conclusions Accuracy of assessment was greatest for vertical cup-to-disc ra tio, neuroretinal rim configuration and cup shape. Improved agreement has b een demonstrated for the final classification of the disc compared with pre vious reports. The combination of training and assessment of additional dis c parameters appears to improve interpretation of the optic nerve head by o ptometrists.