New Algorithm to Enhance Safety of Angle-Supported Phakic IOL Position
To analyze preoperative and postoperative anatomical parameters of the anterior chamber of the eye in high myopic patients corrected with angle-supported phakic intraocular lens (PIOL) using anterior segment optical coherence tomography (AS-OCT).
We studied seventeen highly myopic patients (31 eyes, mean age 25.8±4.6 years) corrected with angle-supported PIOL Cachet (Alcon). Mean spherical equivalent was -12.38±3.64D. AS-OCT (Visante OCT, Carl Zeiss Meditec AG) was performed pre- and postoperatively in all eyes. Preoperatively we measured horizontal and vertical anterior chamber diameters (Angle-to-Angle, ATA) and anterior chamber depth (from corneal epithelium and endothelium). Also in 3 to 12 months postoperatively we assessed the following parameters: PIOL – corneal endothelium (central), PIOL – natural lens (central) and PIOL edge – corneal endothelium (temporal and nasal).
Mean preoperative horizontal and vertical anterior chamber diameters were 12.07±0.38 mmand 12.46±0.44 mmrespectively (P<0.001). Mean anterior chamber depth values from corneal epithelium and corneal endothelium were 3.88±0.31 mmи 3.36±0.33 mmrespectively. Mean distance PIOL – corneal endothelium was 2.19±0.19 mm, PIOL – natural lens – 0.92±0.15 mm, temporal and nasal PIOL edge – corneal endothelium 1.55±0.18 mmand 1.53±0.18 mmrespectively. In 10 out of 31 eyes (6 patients) we found that both nasal and temporal PIOL edge – corneal endothelium parameters were dangerous – less than1.5 mm. Using the stepwise discriminant analysis we created classification formula (reliable with P<0,005) and simplified algorithm to predict the risk of dangerous Cachet position in the anterior chamber of the eye. Sensitivity and specificity of this formula were 100% and 95% respectively.
Current study showed that existing patient selection criteria for Cachet PIOL do not provide its safe position in some cases. New prediction formula and algorithm allow identifying patients at risk to enhance the efficiency and safety of this high myopia correction method.