Dt Pham

A Prospective Evaluation of a Diffractive versus a Refractive Designed Multifocal Intraocular Lens

OBJECTIVE To evaluate prospectively a diffractive (811E, Pharmacia; power add +4.0 D) versus a refractive (PA154N, Allergan; power add +3.5 D) designed multifocal lens. PARTICIPANTS Eighty patients planned for cataract surgery without additional ocular pathologies were randomized into the diffractive or refractive group, respectively. INTERVENTION A standardized no-stitch phacoemulsification with implantation of one of the two multifocal lenses was performed in each patient. MAIN OUTCOME MEASURES Distance and near-visual acuity, contrast sensitivity, low contrast visual acuity, glare visual acuity, and depth of focus were measured after surgery. RESULTS All treated patients had best-corrected visual acuities of 20/30 or better. Near-uncorrected vision was significantly better (P < 0.0001) with the diffractive lens (mean, J1) than with the refractive lens (mean, J4). Low contrast visual acuity (61 +/- 12% versus 59 +/- 9%), glare visual acuity (39 +/- 19% versus 38 +/- 14%), and contrast sensitivity (1.48 +/- 0.08 versus 1.50 +/- 0.12) were not significantly different between the groups. CONCLUSIONS Both lens designs showed satisfactory functional results with advantages for the diffractive lens design.

Monitoring corneal structures with slitlamp-adapted optical coherence tomography in laser in situ keratomileusis

Purpose: To monitor corneal structures with slitlamp‐adapted optical coherence tomography (OCT) in laser in situ keratomileusis (LASIK). Setting: Department of Ophthalmology, Vivantes Klinikum Neukölln, Berlin, Germany. Methods: In this prospective, nonrandomized, comparative clinical case series of consecutive patients who had LASIK for myopia and myopic astigmatism, the corneal structures were studied with slitlamp‐adapted OCT at a wavelength of 1310 nm. The central corneal thickness (CCT) and epithelial, flap, and residual stromal thicknesses were assessed preoperatively, immediately after surgery, on postoperative day 1, and then, on average, after 8, 35, and 160 days. Results: Twenty‐five eyes of 13 patients were included. The attempted mean spherical equivalent correction was −6.11 diopters (D) ± 2.16 (SD) with a mean calculated stromal ablation depth of 92 ± 24 μm. The CCT was 516 ± 26 μm preoperatively and 453 ± 40 μm postoperatively (P<.001). The epithelial thickness increased from 57.0 ± 7.7 μm preoperatively to 61.0 ± 7.5 μm postoperatively (P = .04). Imaging of the hyperreflective interface was possible in all patients for up to 15 months. The flap and residual stromal thickness was 211 ± 28 μm and 344 ± 48 μm, respectively, immediately after LASIK and 164 ± 21 μm (P<.001) and 284 ± 32 μm (P<.001), respectively, on postoperative day 1. There were no further significant changes during the follow‐up. The overall mean reproducibility was ±4.50 μm (coefficient of variation [CV] 0.94%) for CCT, ±4.99 μm (CV 8.57%) for epithelial thickness, ±6.25 μm (CV 3.55%) for flap thickness, and ±7.09 μm (CV 2.42%) for residual stromal thickness. Conclusion: Slitlamp‐adapted OCT can be used to longitudinally monitor the variable structures of the cornea, epithelium, flap, and residual stroma in LASIK.

Causes of severe decentration and subluxation of intraocular lenses

Abstract• Background: Severe decentration and subluxation of intraocular lenses (IOLs) may lead to double vision, glare and deterioration of vision to the point of functional aphakia. The purpose of the present study was to analyse causes for severe IOL dislocation. • Material and methods: Between January 1989 and January 1996, 37 patients required IOL exchange because of decentrated or subluxated posterior chamber lenses. Twenty-five of the exchanged lenses were implanted in our hospital, 12 lenses elsewhere. After explantation the lenses were examined by light and electron microscopy. • Results: In 10 eyes, asymmetric implantation of the posterior chamber lens was responsible for decentration. Three of the lenser concerned were multifocal IOLs. Asymmetric implantation led to a significantly higher rate of explantations in eyes with multifocal lenses (P<0.005). In five eyes decentration developed due to asymmetric capsular shrinkage, in four eyes due to posterior synechiae. A lens subluxation developed in three eyes as a result of rupture of the posterior capsule and in nine eyes because of zonular defects. In three cases decentrations were induced by an extensive secondary cataract. Macroscopically visible changed geometry of the haptics was found in nine lenses; eight of these had polypropylene haptics. Seven lenses showed severely altered haptics on electron-microscopic examination. In four eyes subluxated lenses had to be explanted together with the capsular bag because of severe defects of the zonula, which caused decentration in nine eyes. • Conclusions: Asymmetric implantation of posterior chamber lenses should be strictly avoided. Multifocal lenses require special attention concerning symmetric capsulorhexis and positioning of their haptics.

Continuous monitoring of corneal thickness changes during LASIK with online optical coherence pachymetry

Purpose: To assess the continuous intraoperative monitoring of central corneal thickness (CCT) changes during laser in situ keratomileusis (LASIK) using online optical coherence pachymetry (OCP). Setting: Department of Ophthalmology, Vivantes Klinikum Neukölln, Berlin, Germany Methods: In this prospective nonrandomized comparative clinical case series of consecutive patients, 32 eyes having LASIK for myopia, myopic astigmatism, or hyperopia were continuously monitored intraoperatively in real time with online OCP integrated into a clinical excimer laser. The intraoperative values were compared to the postoperative flap and residual stromal thicknesses measured with corneal optical coherence tomography (OCT) as well as the calculated myopic ablation depth. Results: Continuous monitoring with online OCP enabled intraoperative visualization of the CCT changes during LASIK. The CCT, flap thickness after the microkeratome pass, time‐resolved ablation, and residual stromal thickness were assessed. Intraoperatively, the mean flap thickness was 135 μm ± 38 (SD) and the mean residual stromal thickness, 286 ± 59 μm. The mean intraoperative flap and residual stromal thickness values were 43.7 μm and 15.4 μm lower, respectively, than the postoperative values assessed with corneal OCT (P<.001 and P = .005, respectively). The optically determined myopic ablation depth was 118 ± 37 μm, which was 28 μm higher than the nominal ablation depth. There was a significant correlation (P<.001) between the postoperative flap (r = 0.79) and residual (r = 0.88) thickness measured with corneal OCT as well as the calculated myopic ablation depth (r = 0.95). Conclusions: Intraoperative online OCP could be an important safety feature to monitor the flap and residual stromal thicknesses during LASIK. The individual ablation depth and possible dehydration effects were also monitored continuously.

Postoperative astigmatism and relative strength of tunnel incisions: a prospective clinical trial.

Purpose: To investigate the influence of incision depth and site on wound strength and postoperative astigmatism. Setting: Virchow Memorial Hospital Eye Clinic, Berlin, Germany. Methods: In this prospective, randomized study, 180 patients with a 7.0 mm tunnel incision were examined. They were divided into the following subgroups: primary incision depth of 300 and 500 [&mgr;m; limbal incision and scleral incision; temporal scleral incision and scleral incision at the 12 o’clock position; temporal limbal incision and limbal incision at the 12 o’clock position. Postoperative astigmatism was measured by keratometry and videokeratoscopy 1 day, 1 and 4 weeks, and 8 months postoperatively. Wound strength was measured with an ophthalmodynamometer on the first postoperative day and after 1 week at the site with the least mechanical stability adjacent and posterior to the primary incision. Results: The temporal incision, which was performed 1.0 mm behind the surgical limbus, led to induced astigmatism of 0.65 diopters (D) ± 0.23 (SD) after 8 months. When the incision was at the 12 o’clock position, the induced astigmatism was 0.97 ± 0.41 D. Induced astigmatism was highest following a limbal incision in the 12 o’clock position (1.33 ± 0.63 D). This effect was less pronounced with a temporal incision. Incision depth did not significantly influence induced astigmatism. An incision depth of 500 [Lm led to induced astigmatism of 0.94 ± 0.50 D; a depth of 300 R,m led to induced astigmatism of 0.78 ± 0.64 D. After 1 week, wound strength was highest with temporal scleral incisions (38.6 ± 2.1 kPa by ophthalmodynamometer) and lowest with limbal incisions in the 12 o’clock position (30.8 ± 7.7 kPa). Conclusions: Incision site significantly influenced mechanical wound strength and induced astigmatism; incision depth influenced neither. In general, incisions in the 12 o’clock position induced more astigmatism than temporal incisions.

Influence of cataract surgery on corneal endothelial cell density estimation.

Purpose: To assess the effect of cataract surgery on semiautomated human corneal endothelial cell density (ECD) estimation using noncontact specular microscopy. Methods: In this prospective clinical study, 62 consecutive patients undergoing cataract surgery were studied. To evaluate possible variations of accuracy and agreement under clinical circumstances, the corneal ECD was determined before and after cataract surgery. The parameter ECD (cells/mm2) in the central and paracentral cornea was consecutively determined with 2 algorithms available in a noncontact specular microscope [fixed-frame method (FFM) and automatic center method (ACM)]. The postoperative evaluation was performed at 1 day, after 4 weeks, and after 6 months. The accuracy, the relative error, and the 95% limits of agreement (LoA) were determined for both counting methods. Results: The overall group-averaged accuracy was −19.4 cells/mm2 (0.86%) centrally and −17.3 cells/mm2 (0.76%) paracentrally. The LoA (95% CI) were within 234 cells/mm2 (10.4%) and 250 cells/mm2 (10.9%), respectively. After cataract surgery, a slight decrease in accuracy was noted in the central (2.09%) and paracentral areas (1.76%). The relative error increased from 3.66% to 6.02% centrally and from 4.96% to 6.55% paracentrally. The LoA (95% CI) increased from ±194 cells/mm2 to ±304 cells/mm2 centrally and from ±275 cells/mm2 to ±322 cells/mm2 paracentrally. In the later postoperative period, endothelial stabilization improved the accuracy and agreement in ECD estimation. Conclusions: The estimation of ECD after cataract surgery employing current algorithms was achieved with a clinically acceptable level of accuracy and agreement. However, the analysis of images in the early postoperative period as well as paracentral corneal areas revealed larger variabilities. This revealed that the FFM and ACM counting methods cannot be used interchangeably under all circumstances. The ACM seemed preferable when only low-quality images were available and permitted determination of additional qualitative endothelial cell parameters.

Continuous measurement of corneal dehydration with online optical coherence pachymetry.

Purpose: Online optical coherence pachymetry (online OCP) allows continuous central corneal thickness measurements over time. In this study, the effect of dehydration on corneal tissue was investigated with online OCP. Methods: Twelve eyes of 11 patients were examined with online OCP, and the central corneal thickness was registered over 5 minutes after insertion of an eyelid speculum. Results: Online OCP measurements revealed no decrease in reproducibility after 5 minutes of dehydration. The initial mean central corneal thickness was 538 ± 48 μm. After 5 minutes the central corneal thickness decreased to 483 ± 43 μm (P = 0.001). This corresponded to a mean corneal thinning of 55 ± 4 μm (10.2%) at a rate of 0.19 μm/s. Conclusions: Online OCP was suitable for continuous measurements of corneal changes caused by dehydration. These dehydration effects should be particularly considered in refractive corneal surgery.

A prospective comparison of two multifocal lens models

SummaryBackground: The functional results of two different types of multifocal intraocular lenses (based on the diffractive and refractive principle, respectively) were investigated prospectively. Materials and methods: Altogether 50 patients who had a multifocal lens implanted were examined 4–6 weeks postoperatively. Visual acuity for distance and near vision, contrast sensivity, low contrast visual acuity and glare visual acuity were investigated. Results: Distance visual acuity, contrast sensitivity, low contrast visual acuity and glare visual acuity did not show significantly different results. Near visual acuity was statistically significantly better with the diffractive type of multifocal lens (because of a stronger adjustment for near vision). When the focus depth was tested by defocus curves, both lenses had better results within different areas of defocus. Conclusions: All patients in both groups showed satisfactory results. When choosing a multifocal intraocular lens, the individual needs of each patient should be taken into consideration.Fragestellung: Zwei unterschiedliche Multifokallinsenmodelle verschiedener Wirkmechanismen (diffraktives und refraktives Prinzip) wurden prospektiv hinsichtlich ihrer funktionellen Ergebnisse verglichen. Material und Methode: Bei insgesamt 50 Patienten wurden 4–6 Wochen postoperativ Fernvisus, Nahvisus, Kontrastempfindlichkeit, Kontrastsehschärfe und Blendungssehschärfe bestimmt. Ergebnisse: Beide Linsenmodelle zeigten keine signifikanten Unterschiede hinsichtlich Fernvisus, Kontrastempfindlichkeit, Kontrastsehschärfe und Blendungssehschärfe. Ein signifikant besserer Nahvisus wurde mit der diffraktiven Linse (bei stärkerem Nahzusatz des Linsenmodells) erreicht. Bei der Defokussierung zur Bestimmung der Tiefensehschärfe zeigten sich in jeweils unterschiedlichen Bereichen bessere Ergebnisse zugunsten beider Linsenmodelle. Schlußfolgerung: Beide untersuchten Linsenmodelle zeigen gute funktionelle Ergebnisse. Bei der Wahl des Modells sollten die individuellen Patientenbedürfnisse berücksichtigt werden.

Intraoperative optical coherence pachymetry during laser in situ keratomileusis--first clinical experience.

PURPOSE To investigate intraoperative optical coherence pachymetry during laser in situ keratomileusis (LASIK). METHODS In an initial clinical evaluation, three patients with myopia and myopic astigmatism were studied. Corneal thickness was assessed with optical pachymetry based on low-coherence interferometry during LASIK. RESULTS The attempted mean spherical equivalent refraction was -5.70 +/- 2.00 D with a mean calculated stromal ablation depth of 95 +/- 18 microm. Intraoperative optical coherence pachymetry was reproducible in all patients during the different stages of LASIK, demonstrating a mean flap thickness of 141 +/- 30 microm with a residual corneal stroma of 274 +/- 24 microm at the end of the laser ablation. The immediate postoperative corneal thickness revealed marked swelling. CONCLUSIONS This initial clinical evaluation proved that intraoperative optical coherence pachymetry may be an important safety feature for monitoring flap and residual stromal thickness during LASIK. It may be particularly helpful in the effort to avoid iatrogenic corneal ectasia in patients with thin corneas, higher refractive corrections, and LASIK enhancements.

Corneal optical coherence tomography before and after phototherapeutic keratectomy for recurrent epithelial erosions

Purpose: To study the representation of corneal structures with optical coherence tomography (OCT) before and after excimer laser phototherapeutic keratectomy (PTK) for recurrent epithelial erosions. Setting: Departments of Ophthalmology, Vivantes Klinikum Neukölln, Berlin, and Medizinische Universität, Lübeck, Germany. Methods: This prospective study comprised 15 eyes of 14 patients with recurrent epithelial erosions. The central corneal and epithelial thickness as well as the wound‐healing response in the anterior corneal stroma were assessed with slitlamp‐adapted OCT before and after PTK. Results: After PTK, the symptoms improved in all patients without loss of best corrected, glare, or low‐contrast visual acuity. The mean central corneal OCT thickness was 540 &mgr;m ±28 (SD) preoperatively, 492 ± 36 &mgr;m immediately after epithelial debridement and PTK, and 519 ± 25 &mgr;m after 7 weeks (P < .01). The mean central epithelial OCT thickness changed from 70 ± 13 &mgr;m preoperatively to 60 ± 7 &mgr;m after 7 weeks (P > .01). Changes in the light‐scattering properties in the anterior subepithelial stroma revealed a hyperreflective area with a mean thickness of 46 ± 13 &mgr;m after 7 weeks. Conclusions: Using noncontact corneal OCT, corneal and epithelial thickness changes and the wound‐healing response in the anterior corneal stroma could be evaluated after PTK in patients with recurrent epithelial erosions.