The practical near acuity chart (PNAC) and prediction of visual ability at near.

OBJECTIVE

To improve on present reading chart designs, providing a quick and accurate method to measure the near acuity threshold, of particular importance with low vision patients.

DESIGN

The Practical Near Acuity Chart (PNAC) uses a single paragraph with 3 simple related words on each line (12 lower case letters). The line print size decreases in a logMAR progression (N80-N5).

METHODS

The time taken to measure near acuity of 53 subjects aged 9-91 years with the PNAC and Bailey-Lovie near chart was recorded and compared to their distance acuity (Bailey-Lovie chart), contrast sensitivity (Melbourne Edge Test) and ability to read extracts of newsprint.

RESULTS

There was no difference in near acuity threshold using related or un-related words. There was a high correlation (r = 0.97) between near acuity measured with the PNAC and Bailey-Lovie charts. However, the time taken to measure near acuity was significantly faster with the PNAC (32 +/- 2 s vs 76 +/- 4 s, p < 0.001). Near acuity measured with either chart was highly correlated (p < 0.001) to distance acuity (r = 0.74), contrast sensitivity (r = 0.62) and ability to read newsprint (r = 0.87). The PNAC was shown to have high test-reliable (r = 0.99).

CONCLUSIONS

The PNAC offers a quick but accurate way to measure near acuity and shows a high degree of correlation with distance acuity, contrast sensitivity and the ability to read newsprint.