[Agreement of subjective and objective refraction measurements following INTRACOR femtosecond laser treatment].

BACKGROUND

The goal of this study was to determine the accuracy of autorefraction measurements in patients after INTRACOR intrastromal femtosecond laser treatment of presbyopia by comparing the agreement between the subjective and objective refraction.

PATIENTS AND METHODS

In this study the data of 19 patients with a mean age of 56.5±6.0 years following INTRACOR treatment were analyzed pre-operatively and 12 months postoperatively. Measurements of the subjective refraction and the results of the autorefractor Nidek-660A in miosis were compared. INTRACOR is a refractive intrastromal femtosecond laser treatment to correct presbyopia. During the procedure a series of five concentric rings in the central stroma are cut which cause a change in the curvature of the cornea.

RESULTS

The differences in sphere and spherical equivalent between subjective refraction and autorefraction were not significant (t-test p>0.05 and Wilcoxon test p>0.05). Comparing the cylinder of the two measurements a significant difference (t-test p<0.05) was found. Focusing on the difference of the postoperative measurements of the subjective refraction and autorefraction a correlation (within ±0.5 D) of 89% in the sphere, 100% in cylinder and 68% in the spherical equivalent was detected. With one exception the differences in sphere, cylinder and the spherical equivalent were within ±1.25 D. In several patients the performance of the autorefraction with the Nidek-660A was somewhat complicated and the measures had to be repeated frequently.

CONCLUSION

The agreement between subjective refraction and objective measurements of the Nidek-660A of patients following INTRACOR-treatment was good. However there was a significant difference in the cylinder values. Therefore thorough comparison of measurements obtained with the autorefractor and the subjective refraction is recommended.