A Comparative Study of Hardy-Rand-Rittler and Ishihara Colour Plates for the Diagnosis of Nonglaucomatous Optic Neuropathy

Objective: To determine the ability of the Hardy-Rand-Rittler (HRR) and Ishihara colour plates to detect acquired colour vision defects in patients with nonglaucomatous optic neuropathy (NGON).

Design: Prospective study.

Setting: Neuro-Ophthalmology Unit of the Wilmer Eye Institute, Baltimore.

Patients: A total of 178 consecutive patients (349 eyes) referred to the Neuro-Ophthalmology Unit and the General Eye Service of the Wilmer Eye Institute and examined by two of the authors were enrolled from July 1992 to June 1993.

Outcome Measures: Results of testing with HRR and Ishihara plates.

Results: Among the 202 eyes that were found to have no ocular disease on neuro-ophthalmologic testing, the HRR plates gave a normal result in 168 (83.2%), compared with 196 (97.0%) with the Ishihara plates (p < 0.0001). The HRR plates detected an acquired colour vision deficit in 48 (87.3%) of the 55 eyes with NGON, compared with 38 (69.1%) for Ishihara plates (p = 0.001). The values for the eyes with NGON with a visual acuity of 20/25 or better were 76.5% (13/17) and 35.3% (6/17) respectively (p = 0.008) and with a visual acuity less than 20/25, 92.1% (35/38) and 84.2% (32/38) respectively.

Conclusions: For patients with unilateral or bilateral NGON, HRR plates are more likely than Ishihara plates to detect a colour vision defect, particularly when the visual acuity is 20/25 or better. However, neither test is sensitive enough to be used as the sole criterion for the diagnosis of NGON. The results of comparison of colour perception of the two eyes may be more useful than absolute colour vision responses, particularly in patients with unilateral disease.