REPEATABILITY OF CRYSTALLINE LENS (CL) AND INTRAOCULAR LENS (IOL) THICKNESS AND CENTRE POSITION USING A SWEPT-SOURCE OPTICAL COHERENCE (SS-OCT) BIOMETER.

In cataract surgery, the major cause of postoperative refractive error is attributed to the position of the pseudophakic IOL. Advances in ocular biometry, which are based on the imaging of the ocular components, allow to preoperatively characterising the morphology of the CL and postoperatively measuring the IOL features and position. Acquiring this information sequentially pre and postoperatively in an intra-individual basis will potentially improve the ability to predict the IOL position, and increase the accuracy in the determination of the effective lens position. This pilot study assessed the repeatability of the CL and IOL thickness and their centre position pre and post cataract surgery.       

Ophthalmology Clinic Vista Sánchez Trancón, Badajoz, Spain

Prospective case series of 30 eyes (30 patients) undergoing cataract surgery. Ocular biometry using the SS-OCT IOL-Master 700 (Carl-Zeiss Meditec, Germany) was performed twice preoperatively and one-month postoperatively. Patients were operated through clear corneal incision, by a single surgeon and implanted with a pseudophakic IOL (Hanita AF, Hanita Lenses HQ, Israel) in the capsular bag. The measurements used for analysis were the average of the readings in the six imaging meridians (0-150 deg, 30 deg intervals). The repeatability of the CL/IOL thickness measurements and centre position was determined though test-retest, i.e. 1.96x standard deviation of differences between test and retest.          

Preoperatively the mean CL thickness was 4.45±0.43 mm and postoperatively the IOL thickness was 1.03±0.1 mm. The IOL thickness measured was highly correlated with the manufacturer reported central IOL thickness (R²=0.90). The CL centre was positioned 5.37±0.43 mm from the corneal vertex and the IOL centre at 5.19±0.28 mm. On average, the IOL was positioned 182.6 ±137.5 µm in front of the crystalline lens centre with both centres showing high correlation (R²=0.82). The thicknesses test-retest were 10.4 µm and 27.6 µm for the CL and IOL thickness respectively; and the CL/IOL centres test-retest were 20.4 µm and 31.1 µm, respectively.     

The SS-OCT biometer IOL-Master 700 allows the measurement of the CL and IOL thickness and their centre position with high repeatability, approximately 30 µm. The measured IOL thicknesses were highly correlated with the thicknesses reported by the manufacturer, indicating that the IOL-Master 700 is able of providing a fine characterization of the IOL central thickness. Anatomically, the IOL centre position was highly correlated with the CL centre position, corroborating that the position of the crystalline lens is a valuable parameter for predicting the IOL position.