Comparison of Corneal Thickness Measurements with Optical Low Coherence Reflectometry, Orbscan System and Ultrasound Pachymeter

PURPOSE: To investigate the accuracy and reproducibility of Optical Low Coherence Reflectometry (OLCR) corneal thickness measurements compared with the Orbscan system and ultrasound pachymeter (IOPac, Mentor). METHODS: Two examiners measured corneal thicknesses of 78 normal eyes and in 36 eyes that had undergone LASIK, and five sequential measurements of corneal thickness with OLCR, Orbscan system, Mentor, and IOPac were performed. Remeasurements of corneal thickness in 24 normal eyes were performed after two days to investigate intra-examiner reproducibility. RESULTS: The average corneal thickness measured in normal subjects was 536.3+/-23.8 micrometer in OLCR, 542.4+/-25.3 micrometer in the Orbscan system, 535.4+/-23.7 micrometer in Mentor, and 534.2+/-24.1 micrometer in IOPac. The average corneal thickness measured in patients who had undergone LASIK was 487.3+/-30.8 micrometer in OLCR, 492.5+/-36.5 micrometer in the Orbscan system, 487.5+/-30.8 micrometer in Mentor, and 485.3+/-30.8 micrometer in IOPac. There was no statistically significant difference between the four pachymeters. The inter-examiner and intra-examiner reproducibilities were shown to be highly reliable. CONCLUSIONS: The OLCR showed similar measurments of corneal thickness with the Orbscan system and ultrasound pachymeter, and showed no difference in reproducibility with different examiners.

The Results of Primary Vitrectomy for Rhegmatogenous Retinal Detachment

PURPOSE: To report the anatomic and visual results of vitrectomy without scleral buckling in rhegmatogenous retinal detachment. METHODS: Primary vitrectomy without scleral buckling for the treatment rhegmatogenous retinal detachment was done in 41 eyes (41 patients) and followed up for a mean period of 21.5 months(range 6~65 months). Indications of primary vitrectomy were uncertain preoperative breaks, the presence of large breaks, the presence of breaks near equator, multiple breaks, proliferative vitreoretinopathy not related to breaks and presence of inferior vitreous hemorrhage. RESULTS: The anatomic success rate after a single operation was 90.2%. Visual acuity was improved or stable in 37 eyes (90.2%). Progression of lens opacity (35.7%) and formation of epiretinal membrane (12.2%) constituted the major complications after primary vitrectomy. CONCLUSIONS: Primary vitrectomy without scleral buckling can be a safe, effective method to repair primary rhegmatogenous retinal detachments in selective cases.

Effect of the Aspheric RGP Lens on Corneal Topography and Endothelial Cell in Keratoconus

PURPOSE: To analyze the effects of the aspheric rigid gas permeable (RGP) lens on the corneal topography and endothelial cells in eyes with keratoconus. METHODS: Sixty five eyes of 35 keratoconic patients who had follow-up of more than 6 months were included in the study. Thirty eyes of 16 patients wore aspheric RGP lens, and the remaining control eyes did not wear any lens. After aspheric RGP lens fitting, visual acuity and manifest refractive error were evaluated, Slit lamp examination and corneal topography were also done. Mean cell area and density of corneal endothelial cell were measured by specular microscopy at first visit and 6 months after lens fitting. RESULTS: After lens fitting, the percentage of best corrected visual acuity of better than 20/25 was 93.3% (28 eyes). The change of astigmatism, the Steepest Simulated keratometry reading, Surface asymmetry index, Surface regularity index, and apical corneal power were significantly increased in the keratoconic cornea in aspheric lens fitting group compared to the control group (p0.05). CONCLUSIONS: Short-term wearing of aspheric RGP lens in keratoconic patients showed no effect on corneal endothelial cells. However, it increased the irregularity and steepening of the keratoconic cornea. It may indicate that mid-peripheral corneal-to-lens relationship may be inappropriate when keratoconus is fitted with aspheric lens.

Results of Triple Surgery: Cataract Extraction, Intraocular Lens Implantation and Vitrectomy for Retinal Detachment

PURPOSE: To report the anatomic and visual results of triple surgery in patients with cataract and rhegmatogenous retinal detachment. METHODS: This retrospective study examined 11 cases of phakic detachment. All 11 eyes had both rhegmatogenous retinal detachment and cataract. For these, a triple procedure involving pars plana vitrectomy, cataract surgery and posterior chamber intraocular lens (PCL) insertion was performed. Intraocular lens (IOL) power calculation was performed in the diseased or both eyes. RESULTS: A clear intraoperative view of the fundus was obtained in all cases. The retina was reattached by triple surgery in 9 eyes. In one failed case, there had been extensive detachment with preoperative proliferative vitreoretinopathy grade C type 1. In the other case, retinal detachment recurred due to a new break. The two failed eyes obtained anatomic success by reoperation. Preoperative visual acuity (hand movement/10cm to 0.2) was improved (finger count/20cm to 0.8). There were 2 visual imbalances of -8.0 diopter and -10.0 diopter due to miscalculation of IOL power. CONCLUSIONS: In selective cases, combined triple surgery spares the patient repeat surgery and can offer a more rapid visual rehabilitation by clearly identifying the breaks and avoiding delays in detachment repair. To avoid miscalculation, IOL power must be calculated in both eyes, especially in cases of macular detachment.