Comparison of anterior chamber depth measurements using Orbscan II and IOLMaster.

PURPOSE: To evaluate and compare anterior chamber depth (ACD) measurements using Orbscan II (Bausch & Lomb, Rochester, NY) and IOLMaster (Carl Zeiss Meditec AG, Jena, Germany). METHODS: In this prospective clinical study, the authors measured ACD of 145 phakic eyes of 30 healthy volunteers and 115 patients using Orbscan II and IOLMaster. Average patient age was 52.9+/-19.4 (range 16 to 87) years. ACD was evaluated from corneal epithelium to anterior lens surface. Additionally, axial length (AL) was measured using the Zeiss IOLMaster to calculate the regression coefficient between AL and ACD. RESULTS: Mean ACD was 3.35+/-0.43 mm (range 2.01 mm to 4.37 mm) using Orbscan II and 3.36+/-0.41 mm (range 2.09 mm to 4.24 mm) using IOLMaster. Mean total axial length was 24.04 mm +/- 2.1 mm (range 20.7 mm to 31.41 mm). The linear regression coefficient of ACD between both methods was R=0.95. ACD and AL correlated only slightly (R=0.57). The Spearman coefficients of rank correlation were 0.94 and 0.61, respectively. A p value less than 0.01 (paired Wilcoxon test) was considered statistically significant. However, a significant difference was not calculated comparing ACD measurements using both systems and the Bland-Altman-Plot showed 95% of the differences ranging between 0.25 and -0.27 mm. CONCLUSIONS: Regarding clinical application, both systems seem to be equally good and interchangeable in clinical practice in terms of ACD evaluation.

Intraocular lens power calculation using ray tracing following excimer laser surgery.

PURPOSE: To evaluate intraocular lens (IOL) power calculation using ray tracing in patients presenting with cataract after excimer laser surgery. METHODS: Ten eyes of seven consecutive patients who presented for cataract surgery following excimer laser treatment without any pre-refractive biometry data were enrolled in this prospective clinical study. Preoperatively, IOL power calculation was performed using a ray tracing software called OKULIX. Keratometry data (C-Scan) were imported and axial length (IOLMaster) was entered manually. Accuracy of IOL power calculation was investigated by subtracting attempted and achieved spherical equivalent. RESULTS: Mean spherical equivalent was -3.51+/-2.77 D (range -10.38 to -0.5 D) preoperatively and -1.01+/-1.08 D (range -2.5 to +0.75 D) postoperatively. Mean error was 0.31+/-0.84 D, mean absolute error was 0.74+/-0.46 D, and IOL calculation errors ranged from -1.39 to +1.47 D. A total of 40% of eyes were within +/-0.5 D, 70% within +/-1.0 D, and 100% within +/-1.5 D. Three eyes with corneal radii over 10 mm showed calculation errors exceeding +/-1.0 D. Mean best-corrected visual acuity increased from 20/60 to 20/30 postoperatively. CONCLUSIONS: IOL power calculation after excimer laser surgery can be difficult, especially when pre-refractive keratometry values are not available. In these cases, ray tracing combined with corneal topography measurements provides reliable and satisfactory postoperative results. However, it is advisable to be careful when calculating IOL power for eyes with corneal radii exceeding 10 mm because of slightly higher prediction errors.

[Accuracy of lens power calculation and centration of an aspheric intraocular lens]. / Genauigkeit der Linsenstärkenberechnung und Zentrierung einer asphärischen Intraokularlinse.

BACKGROUND: Aspherical intraocular lenses (IOLs) are presumed to optimize the optical characteristics of IOLs. In order to profit from these characteristics, exact calculation of the IOL power and good centration of the lens are essential. METHODS: In all, 43 eyes of 43 patients with an average age of 70.9+/-8.3 years underwent implantation of a Tecnis IOL (AMO, Ettlingen) after uneventful cataract surgery with topical anesthesia. IOL power calculation was performed using the Holladay, Haigis, and SRK II formulas. Spherical equivalent refraction and centration and position of the implanted IOLs were measured 6 months postoperatively. Centration of the IOL was analyzed using digital slit lamp photographs and an image analysis program. RESULTS: Best corrected visual acuity (BCVA) increased from 0.47+/-0.25 (LogMAR) preoperatively to 0.1+/-0.11 6 months postoperatively (spherical equivalent +0.3+/-0.6 D). The intraindividual difference between target refraction and achieved postoperative refraction was 0.64+/-0.11 D for the Holladay formula, -0.21+/-0.11 D for the Haigis formula, and 0.97+/-0.15 D for the SRK II formula. The mean decentration of the IOL from the center of the corneal limbus was 0.4+/-0.1 mm. CONCLUSIONS: For the aspherical Tecnis IOL very good postoperative functional results are reported, which are supported by an accurate calculation of the IOL power and a good centration of the IOL inside the capsular bag. In this study the Haigis formula showed the lowest difference between target refraction and achieved postoperative refraction.

Prospective, non-randomised, long term clinical evaluation of a foldable hydrophilic single piece intraocular lens: results of the Centerflex FDA study.

BACKGROUND: Owing to the improvement of modern intraocular lenses (IOLs) in terms of design and material, posterior capsule opacification (PCO) usually takes 2-3 years to develop. Thus, long term clinical evaluation of new implants is important. METHODS: As part of a prospective, non-randomised FDA trial, the Rayner Centerflex, a foldable hydrophilic acrylic, single piece IOL was implanted in one eye of 83 patients (mean age 73.5 (SD 7.0) years). Over 3 years postoperatively, a standardised FDA protocol concerning IOL safety and efficacy was followed including evaluation of spherical equivalent (SE), best corrected distance visual acuity (BCDVA), endothelial cell count (ECC), flare meter values, PCO development, and anterior capsule shrinkage. RESULTS: Postoperatively, mean SE was stable ranging between -0.3D and 0.17D. After 1-2 months, all patients achieved a BCDVA of 20/40 or better. At 3-6 months postoperatively, mean ECC decreased from 2612 (SD 346) cells/mm2 to 2380 (316) cells/mm2. Mean PCO score for the entire optic increased from 0.20 (0.20) months (3-6 months postoperatively) to 0.87 (0.57) resulting in a Nd:YAG rate of 29.41% after 3 years. No anterior capsule shrinkage was found. CONCLUSION: The Centerflex showed excellent functional results, low values for endothelial cell loss and inflammatory signs, and no anterior capsule shrinkage. PCO formation was higher compared to other IOLs, which could be explained by the incomplete sharp edge at the optic-haptic junctions representing an "Achilles' heel" for cell ingrowth.

[Quantitative evaluation of acrylic and silicone intraocular lenses with a sharp optic edge design]. / Quantitative Nachstarevaluierung von Acrylat- und Silikonintraokularlinsen mit scharfem Kantendesign.

BACKGROUND: At the Department of Ophthalmology, Heidelberg, Germany, posterior capsule opacification (PCO) of a silicone and an acrylic intraocular lens (IOL) with a sharp optic edge design was evaluated. PATIENTS AND METHODS: In a prospective study either the AMO ClariFlex silicone IOL or the Sensar AR40e hydrophobic acrylic IOL were implanted in 47 patients following uneventful phacoemulsification. Mean patient age was 76.2+/-7.8 (ClariFlex) and 73.4+/-12.9 years (AR40e), respectively. The mean follow-up time was 19.7+/-5.34 in the ClariFlex and 21.9+/-1.89 months in the AR40e group. PCO development was evaluated postoperatively using the EPCO 2000 analysis software (scale 0-4). Areas of interest were the total IOL optic, the central 3-mm zone as well as the capsulorhexis. RESULTS: In both groups, all patients achieved a BCVA of 20/32 (AR40e) and 20/25 (ClariFlex), respectively. There was a very low incidence of PCO development with a mean EPCO score of 0.07+/-0.2 (ClariFlex and 0.15+/-0.2 (AR40e). Within the 3-mm zone and the capsulorhexis, there was a tendency for even lower EPCO scores in both groups. We calculated a statistically significant difference for the two lens materials for all investigated IOL areas (Wilcoxon's test, p<0.05). CONCLUSION: Both IOLs with a sharp edge design showed good functional results, a stable position in the capsular bag as well as a low incidence of PCO development. However, the silicone IOL showed statistically significantly lower PCO scores.

[New methods for the prevention of posterior capsule opacification]. / Neue Methoden der Nachstarprävention.

Even though tremendous advances have been made especially during the last 10-15 years in terms of surgical techniques and improvement of implant technology, posterior capsule opacification (PCO) still remains a serious long-term complication. New clinical and laboratory studies (especially of autopsy eyes) have improved our understanding of how IOL design and material influence PCO. Sharp edge optic designs of IOLs of various materials have been shown to significantly reduce secondary cataract. The application of pharmacological substances selectively into the capsular bag is now possible due to the development of the PerfectCapsule System for vacuum-sealed capsule irrigation. Major advances in other areas of biotechnology and immunology including gene therapeutic methods offer totally new approaches for the future in the elimination of lens epithelium cells from the capsular bag. This survey gives an update on current and future means and trends to reduce or prevent PCO formation.