| Sumario: | Purpose: To compare the visual acuity of pre- and post-cataract surgery patients using a Snellen and Dyop acuity chart as to differences in resolution versus recognition acuity. Methods: Fifty-nine patients (105 eyes) with senile cataracts, aged 40 years or older and with no other ocular pathologies, were evaluated as to visual acuity for pre- and post-cataract surgery using the Snellen and Dyop acuity charts. Results: Pre-surgery cataracts were nuclear in 50 eyes; nuclear and posterior subcapsular in 24 eyes; nuclear and cortical in 23 eyes; nuclear, cortical, and posterior subcapsular in 4 eyes; and nuclear, anterior, and posterior subcortical in 2 eyes. The average spherical equivalents from pre-cataract surgery refractive assessments for the patients were -0.61±2.81D and -0.63±3.22D for right and left eyes, respectively. The mean VA measured prior to cataract surgery was significantly overestimated with Snellen (OD: 0.64±0.15, OS: 0.69±0.23 decimal units) versus Dyop (OD: 0.53±0.25, OS: 0.55±0.24 decimal units) for both eyes (OD: p=0.01, OS: p=0.01). The mean VA measured following cataract surgery was also significantly overestimated with Snellen (OD: 0.88±0.22, OS: 0.85±0.20 decimal units) versus Dyop (OD: 0.72±0.22, OS: 0.72±0.23 decimal units) for both eyes (OD: p=0.00, OS: p=0.01). The Bland Altman plots of difference in the means for assessment of visual acuity with the two charts against the average means for assessment of visual acuity with the two charts for both eyes showed no agreements for the two pre- and post-cataract surgery. Conclusions: Visual acuity measurements pre- and post-cataract surgery were different with a Snellen and a Dyop acuity chart in that the Dyop test was a more precise indicator of acuity resolution. These two charts cannot be used interchangeably. The apparent strength of the Dyop acuity assessment is that it primarily uses resolution acuity, thus preventing overestimation of visual acuity, which is inherent in the recognition acuity of the Snellen test.
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