Blur point versus indistinguishable point in assessment of accommodation: objective and subjective findings in early presbyopes

Aim: To measure the distance from the eye and the refraction of the eye at the point at which print blurs and the point at which it becomes unreadable.

Methods: Subjective accommodation in 7 early presbyopic subjects (mean age 45 years), with no additional near correction, was tested using 6/12 reduced Snellen and 6/12 Lea symbols. The point at which blur was first noticed and the point at which the print became indistinguishable were noted in centimetres. Objective measures of refraction were taken at each of these points.

Results: Subjective and objective results for reduced Snellen and Lea symbols were similar ( p = 0.91; p = 0.81) as were the points where the print was no longer distinguishable ( p = 0.23; p = 0.72). The difference between the blur point and the indistinguishable point measured in centimetres for both the reduced Snellen text and Lea symbols were statistically significant ( p = 0.005; p = 0.0001). The objective measures for these points, however, were not statistically different ( p = 0.32 and p = 0.63, respectively).

Conclusion: A clinically significant difference exists in the distance from the eyes between the point at which text blurs and the point at which it becomes indistinguishable. No significant change occurs in accommodation when measured objectively after the blur point. It is recommended that the end point of this test is the point at which print starts to blur.