Accurate Intraocular Lens Position Determination in Pseudophakic Eyes

Resumo

OBJECTIVES 

This work seeks to validate postoperative Anterior Chamber Depth (ACD_post) mesurement devices based in optical low-coherence reflectometry (Lenstar LS 900, (Haag-Streit AG, Köniz, Switzerland) and optical coherence tomography (Visante OCT, Carl Zeiss Meditec Inc., Dublin, California, USA).

MATERIAL AND METHODS 

A pseudophakic eye phantom was built to check the calibration of both devices. A clinical study involving 40 pseudophakic eyes was conducted and 3 months after surgery ACDpost was measured with both devices and compared.

RESULTS

Zeiss Visante calibrations had a R.M.S error smaller than the device’s 18 μm resolution in all the measurement sets. No span shift nor zero shift errors were found. Lenstar calibrations had a larger R.M.S error in the order of the device’s 20 μm resolution. In the clinical study, Lenstar failed to measure ACD_post 11% of the times. Additionally Lenstar measured an average IOL thickness of 0.74μm with σ = 0.08mm and a 16% failure rate. Bland-Altman (BA) analysis was performed and a mean difference of 74μm between the measurements was found. The dioptric shift induced by the difference between measurements was calculated in a worst case scenario and a 0.18D difference was found. This is clinically insignificant and the measurements can be considered to be interchangeable.

CONCLUSIONS

Both devices performed accurate measurements of ACD_post. Results from the clinical trial proved the interchangeability of the measurements in vivo. This will certainly contribute to the improvement of ACD_post estimation methodologies and ultimately contribute to the improvement of IOL power calculation methodologies.