Discriminative power of reading tests to differentiate visual impairment caused by cataract and age-related macular degeneration

Purpose

To determine whether preoperative reading tests can be used for differentiating visual impairments with regard to the diagnosis of cataract and age-related macular degeneration (ARMD).

Setting

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

Methods

Reading performance of patients with nuclear cataract, posterior subcapsular cataract, and ARMD were evaluated with respect to reading acuity, maximum reading speed, and critical print size; normal-sighted participants were tested as controls. A multivariate discriminant analysis of the 4 groups (100 eyes of 100 participants) was performed to evaluate how many patients could be correctly diagnosed by significant differences in the tested reading parameters. Subsequently, the nuclear cataract and posterior subcapsular cataract patients were compared with cataract patients with coexisting ARMD.

Results

Distance visual acuity was comparable in the nuclear cataract, posterior subcapsular cataract, and ARMD groups (P>.05). Reading acuity was significantly reduced in posterior subcapsular cataract and ARMD patients compared with nuclear cataract patients and controls (P<.0001). No significant difference in maximum reading speed was found between the nuclear cataract patients and the controls (P = .07), whereas the maximum reading speed of the posterior subcapsular cataract and ARMD patients was significantly reduced (P<.0001). In the discriminant analysis, it was possible to assign the correct diagnosis to 72% of the nuclear cataract patients, 76% of the posterior subcapsular cataract patients, 72% of the ARMD patients, and 92% of the controls. Comparing the reading performance of nuclear cataract and posterior subcapsular cataract patients and cataract patients with coexisting ARMD showed that reading performance was significantly impaired in the comorbid patients (nuclear cataract and ARMD, P<.001; posterior subcapsular cataract and ARMD, P<.05).

Conclusion

The high discriminant accuracy shows that this standardized reading test system is a valuable diagnostic tool for evaluating functional visual impairments when distance visual acuity alone cannot elucidate the origin of functional impairment. Considering the significant discrepancies in reading performance among patients with nuclear cataract, posterior subcapsular cataract, and ARMD, reading tests may relevantly improve the clinical evaluation of patients with visual loss, even of patients with ocular comorbidity.