Scheimpflug imaging to determine intraocular lens power in vivo

Purpose

To assess the feasibility of determining intraocular lens (IOL) power by measurement of the central optic thickness using clinically available Scheimpflug imaging (Pentacam, Oculus).

Setting

King's College Hospital Ophthalmology Department, London, United Kingdom.

Methods

Sixty-seven eyes were assessed 1 month after uneventful phacoemulsification with in-the-bag implantation of AcrySof MA60AC IOLs (Alcon). The correlation between IOL thickness measurement and IOL power was calculated. Repeatability of central optic thickness measurement was determined from 10 successive scans of 4 patients.

Results

Within-subject standard deviation increased with the subject mean. The coefficient of variability was 1.4%. Measured lens thickness was highly correlated with lens power (R² = 0.94, P<.001). Over the measured range, 95% confidence intervals varied between ±0.83 diopters (D) and ±0.92 D.

Conclusions

Central IOL thickness measurements with the Pentacam Scheimpflug camera were highly repeatable and closely correlated with the known IOL power. The IOL power, calculated from a regression equation, is likely to be less than ±1.00 D away from the actual power. Approximate in vivo IOL power determination is feasible with clinically available Scheimpflug imaging. This could be applied clinically in cases of unexplained postoperative refractive error.