Observation on changes of anterior chamber and chamber angle structures after posterior chamber phakic intraocular lens implantation by ultrasound biomicroscopy

Abstract

To study the changes of anterior chamber and chamber angle structures after implantable contact lens (ICL) implantation in high myopia by using ultrasound biomicroscopy (UBM). A prospective series case study was conducted on 15 high myopia patients (30 eyes) treated with ICL implant. These patients were followed for one year postoperatively. Intraocular pressure (IOP) was measured by Goldmann applanation tonometer after surgery. All eyes were examined by UBM one year after the surgery. Central anterior chamber depth (ACD), trabecular-iris angle (TIA), the distance between the posterior surface of ICL and the lens and the distance between peripheral surface of ICL and the lens were measured. Nonparametric test was used to compare TIA. One-way ANOVA was used to assess the distance between peripheral surface of ICL and the lens. Repeated Measure ANOVA and Bonferroni test was performed to compare the IOP level before and after surgery. Paired t-test was used to compare ACD. Intraocular pressure changed from (13.75 +/- 2.27) mm Hg (1 mm Hg = 0.133 kPa) preoperatively to (14.27 +/- 1.70), (14.70 +/- 2.07), (14.07 +/- 2.24), (14.00 +/- 2.69) and (13.97 +/- 2.95) mm Hg at 1 week, 1, 3, 6 and 12 months after the surgery, respectively. There was a statistically significant increase of the IOP one month after the surgery, which was normalized completely at 3 months after surgery. The distances between central posterior surface of the cornea to the ICL and the lens were (2.24 +/- 0.21) and (2.97 +/- 0.11) mm, respectively. There was significant difference between these two data (t = 20.63, P < 0.01). TIA was measured in 12:00, 3:00, 6:00 and 9:00. There were no statistically differences between them. TIA was greater than 30 degree in 55.8% of cases. The distance between the central anterior surface of the ICL to the lens (central section) was (0.63 +/- 0.16) mm. No contact was found between the ICL and the crystalline lens. Posterior chamber phakic intraocular lens implantation for the surgical correction of high myopia is a safe procedure as evaluated with immediate visual and refractive results. We found that the iridocorneal angle and the anterior chamber depth are decreased after the surgery. There is no contact between the crystalline lens and ICL. The ICL contacts with the posterior iris surface.