Selection of the posterior chamber phakic intraocular lens length

Abstract

To evaluate the efficacy, safety and clinical value of calculating the posterior chamber phakic intraocular lens (ICL) length according to the corneal horizontal diameter. This was a retrospective study. A Staar Visian implantable contact lens (ICL) was implanted in 32 patients (64 eyes) with high myopia in the Department of Ophthalmology, the First Affiliated Hospital, College of Medicine, Zhejiang University between November 15, 2005 and January 15, 2011. The lens length was calculated according to the corneal horizontal diameter measured by Orbscan II. Patients were followed up postoperatively at 1 day, 1 week, 1, 3, 6 and 12 months and every 6 months thereafter. The evaluations included visual acuity, manifest refraction, applanation tonometry, endothelial cell count, slit-lamp microscopy to detect cataract, and UBM to assess the degree of ICL tilt and distances between the corneal endothelium, the ICL, and the crystalline lens. All of the preoperative and 12-month follow-up observations were analyzed using SPSS 16.0 software. No anterior subcapsular cataracts were found in any of the eyes after surgery. Pigmentary dispersion was observed on the anterior and posterior surface of the ICL, but the difference was not statistically significant (χ(2) = 2.24, P = 0.13). The intraocular pressure changed from (15.67 ± 3.23) mm Hg (1 mm Hg = 0.133 kPa) to (15.78 ± 3.23) mm Hg, but the difference was not significant (t = 0.24, P = 0.38). The corneal endothelium-lens (central section) distance measured by UBM postoperatively was (2.97 ± 0.25) mm and the corneal endothelium-ICL (central section) distance was (2.24 ± 0.27) mm; the difference between them was statistically significant (t = 15.77, P < 0.01). The degree of ICL tilt measured by UBM was 1.20° ± 1.05 °. The percentage of eyes with a trabecular-iris angle (TIA) greater than 30°, between 21° and 30°, between 11°and 20°, and smaller than 10° were 29.1%, 50.0%, 11.6%, and 9.3%, respectively. The angle opening distance at 500 micron (AOD500) measured by UBM postoperatively was (0.32 ± 0.15) mm. The contact distance between the iris and the ICL measured by UBM postoperatively was (0.85 ± 0.46) mm and the ICL-lens central distance was (0.47 ± 0.25) mm. The Pearson's correlation coefficients between the ICL-lens central distance and the corneal horizontal diameter, sulcus diameter, anterior chamber depth(ACD) and ICL length were 0.11, 0.16, 0.04 and 0.19, respectively; none were statistically significant. The ICL-lens peripheral distance measured by UBM postoperatively was (0.25 ± 0.20) mm. Selecting the length of the ICL according to the corneal horizontal diameter is appropriate, and assures the safety, effectiveness and predictability of ICL implantation.