Central corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system.

OBJECTIVE: To compare the reliability of central corneal thickness measurements (CCT) obtained with partial coherence interferometry (PCI), ultrasound pachymetry, and the Orbscan system. DESIGN: Cross-sectional study. PARTICIPANTS: Twenty healthy subjects with CCT measurements in both eyes. METHODS: The CCT measurements were obtained with PCI, ultrasound pachymetry, and the Orbscan system. In each eye, 2 investigators performed 5 repeated measurements with each pachymetric device. Intraclass correlation coefficients (kappa) were calculated and mean CCT measurements were compared. MAIN OUTCOME MEASURES: The CCT measurements obtained with ultrasound pachymetry, the Orbscan system (Orbtek Inc., Salt Lake City, UT), and PCI. RESULTS: Mean CCT values measured with ultrasound pachymetry were significantly thicker than those measured with PCI (21.5 microm; P<0.001) or the Orbscan system (19.8 microm; P<0.001). The correlation coefficients for the intraobserver variability were 0.999 for PCI measurements, 0.983 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. The correlation coefficients for the interobserver variability were 0.998 for PCI measurements, 0.980 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. There was a slightly better consistency between ultrasound pachymetry and PCI (kappa = 0.96) than between the Orbscan system and PCI (kappa = 0.92) and between ultrasound pachymetry and the Orbscan system (kappa = 0.89). CONCLUSIONS: Partial coherence interferometry was the method with the least intraobserver or interobserver variability. Mean CCT as measured with ultrasound pachymetry was approximately 20 microm thicker than with the Orbscan system and PCI. However, corneal thickness measurements with ultrasound pachymetry and PCI were slightly more consistent than those of the Orbscan system and PCI. This slightly better consistency, however, may be important, especially in corneal refractive surgery.

Effect of accommodation and pupil size on the movement of a posterior chamber lens in the phakic eye.

PURPOSE: Although a posterior chamber phakic intraocular lens provides effective refractive correction of high myopia and hyperopia, mechanical contact between the implantable contact lens (ICL) and the crystalline lens and inadequate aqueous circulation in the prelenticular space could cause subcapsular opacification. To assess whether and to what extent such mechanical contact occurs, changes in the distance between the STAAR Collamer ICL and the crystalline lens under various conditions were investigated. DESIGN: Open pilot study. PARTICIPANTS: Thirteen eyes of 11 myopic and 2 hyperopic patients with a mean age of 38 years (range, 19-53 years) were examined at least 6 months after ICL implantation. METHODS: A noninvasive, high-resolution biometry technique, partial coherence interferometry, was used to measure distance changes between the ICL and the crystalline lens during subjective accommodation, after instillation of pilocarpine, and under changing light conditions. MAIN OUTCOME MEASURES: Mean distance changes from the posterior corneal surface to the ICL, from the posterior corneal surface to the anterior surface of the crystalline lens, and the distance between the ICL and the crystalline lens. RESULTS: In the nonaccommodated state, the mean distance between the ICL and the crystalline lens was 457 microm (range, 123-924 microm). During subjective accommodation, a significant (P<0.01) decrease and, after topical application of pilocarpine, a nonsignificant (P=0.35) decrease of anterior chamber depth was accompanied by a nonsignificant (P = 0.71) reduction of the ICL-crystalline lens distance. Under photopic conditions, a significant mean reduction (P<0.01) of the ICL-crystalline lens distance of -28 microm (range, -16 to -188 microm) was observed. CONCLUSIONS: Partial coherence interferometry biometry enabled noninvasive high-precision investigation of ICL dynamics. No significant changes between the ICL and the crystalline lens were detected during subjective accommodation and after application of pilocarpine. However, under photopic conditions, with constriction of the pupil, the distance between the ICL and the crystalline lens was significantly reduced. This mechanism might cause inadequate aqueous circulation in the prelenticular space and might be one of the causes of subcapsular opacification in some of the eyes after ICL implantation.

Effect of optic edge design and haptic angulation on postoperative intraocular lens position change.

PURPOSE: To assess the effect of optic edge design and optic-haptic angulation of open-loop intraocular lenses (IOLs) on postoperative axial movement and the final position of the optic by measuring the anterior chamber depth (ACD) during the first postoperative year using partial coherence interferometry (PCI). SETTING: Department of Ophthalmology, Vienna General Hospital, Institute of Medical Physics, University of Vienna, Vienna, Austria. METHODS: In study 1, a 3-piece silicone IOL with nonangulated modified C-loop haptics (MicroSil, Dr. Schmidt) was implanted in 78 eyes of 39 patients; patients were randomized to receive a round-edged optic IOL in 1 eye and a sharp-edged optic IOL in the other eye. The ACD was measured by PCI 1 day, 1 week, 3 months, and 1 year after surgery. In study 2, a foldable, 3-piece acrylic IOL with modified 10-degree angulated J-loop haptics (AcrySof MA60BM, Alcon) was implanted in 32 eyes of 32 patients. The ACD was measured by PCI 1 day, 1 week, and 3 months after surgery. RESULTS: In eyes with a nonangulated silicone IOL, there was a significant postoperative change in ACD with both sharp-edged and round-edged designs (P<.01). There was forward movement of both IOL designs in the first week, with no significant difference between the 2 models. From 1 week to 3 months, there was backward movement of IOLs of both designs, with the sharp-edged IOL moving a significantly greater amount (P<.001). From 3 months to 1 year, IOLs with both optic edge designs moved slightly backward. Sixty-six percent of angulated IOLs showed continuous but variable forward movement and 34%, backward movement. CONCLUSIONS: Optic edge design influenced postoperative axial optic movement and thus had an impact on the development of postoperative refraction (refractive shift, deviation from target refraction). The influence of optic-haptic angulation proved to be significantly greater and more variable than edge design.

Early objective assessment of intraocular inflammation after phacoemulsification cataract surgery.

PURPOSE: To evaluate the time course of blood-aqueous barrier (BAB) disturbance in the early period after small-incision cataract surgery. SETTING: Department of Ophthalmology, Vienna University, Vienna, Austria. METHODS: In a prospective study, 15 eyes of 15 patients with age-related cataract had small-incision cataract surgery by phacoemulsification with intraocular lens implantation. Care was taken to minimize trauma to the uvea during surgery. Postoperative inflammation was assessed by measuring aqueous flare and cell count with a laser flare-cell meter. Postoperative measurements were performed hourly for the first 6 hours, every 2 hours until 12 hours, every 4 hours until 40 hours, and every 8 hours until 56 hours. RESULTS: The time course of aqueous flare and cell count differed significantly among patients. The peak inflammatory response in most cases was 1 hour after surgery, with the response decreasing thereafter. The pattern of the time course was classified into subgroups defined by the presence and size of an initial spike immediately after surgery and the intensity of the subsequent inflammatory reaction. A slight increase in flare and cells was seen in the morning hours of the first postoperative day. CONCLUSIONS: Acute BAB disturbance within the first 48 hours after small-incision cataract surgery showed high interpatient variability. However, many differences were not detectable 1 day after surgery.

Influence of operator experience on the performance of ultrasound biometry compared to optical biometry before cataract surgery.

PURPOSE: To compare measurements performed with the IOLMaster (Carl Zeiss, Meditec AG) with those obtained by applanation ultrasound (US) and manual keratometry and to evaluate the effect of operator experience on US biometry. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: The axial length (696 eyes) and anterior chamber depth (ACD) (462 eyes) were measured in 377 patients with cataract using the IOLMaster and applanation US. To assess the effect of operator experience on the biometric results, the operators were divided into 2 groups: experienced and less experienced in performing US biometry. The difference in measurements between the methods and the variability of the difference were compared between the 2 groups. RESULTS: Applanation US measured axial length and ACD shorter than the IOLMaster; the mean numerical difference was 0.13 mm and 0.19 mm, respectively (P<.01). For axial length, the absolute difference was smaller with experienced operators than with less experienced operators (0.15 mm versus 0.22 mm) (P<.01). For ACD, experienced operators obtained a smaller difference between measurement techniques (0.21 mm versus 0.29 mm; P<.05). CONCLUSIONS: Experienced US operators had less difference and lower variability in the difference between applanation US and IOLMaster readings for axial length and ACD measurements. The noncontact optical method, which is essentially operator independent, gave significantly more reliable biometry before cataract surgery, especially in the case of less experienced operators.

Effect of a fixed dorzolamide-timolol combination on intraocular pressure after small-incision cataract surgery with Viscoat.

PURPOSE: To evaluate the effect of a fixed dorzolamide-timolol combination (Cosopt) on intraocular pressure (IOP) after small-incision cataract surgery with sodium chondroitin sulfate 4%-sodium hyaluronate 3% (Viscoat). SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: This prospective randomized study comprised 76 eyes of 38 patients scheduled for small-incision cataract surgery in both eyes. Patients were randomized to receive 1 drop of the fixed dorzolamide-timolol combination in 1 eye or no treatment (control) immediately after cataract surgery. The fellow eye received the other assigned treatment. Cataract surgery was performed with Viscoat in an identical fashion in both eyes. The IOP was measured preoperatively and 6 hours, 20 to 24 hours, and 1 week postoperatively. RESULTS: Six hours after surgery, the mean increase in IOP was significantly lower in the dorzolamide-timolol group than in the control group (4.3 mm Hg +/- 5.6 [SD] versus 8.4 +/- 6.1 mm Hg; P =.003). Two eyes in the dorzolamide-timolol group and 9 in the control group had IOP spikes of 30 mm Hg or higher (P =.022). Twenty to 24 hours after surgery, the mean IOP change was -2.6 +/- 3.3 mm Hg in the dorzolamide-timolol group and 1.5 +/- 3.2 mm Hg in the control group (P<.001). CONCLUSIONS: The fixed dorzolamide-timolol combination was effective in reducing IOP 6 hours and 20 to 24 hours after cataract surgery. However, it did not prevent Viscoat-induced IOP spikes of 30 mm Hg or higher.

After-cataract in adults with primary posterior capsulorhexis: comparison of hydrogel and silicone intraocular lenses with round edges after 2 years.

PURPOSE: To evaluate the potential of primary posterior continuous curvilinear capsulorhexis (PCCC) to prevent after-cataract 2 years after surgery and perform a bilateral comparison of 2 intraocular lens (IOL) materials, silicone and hydrogel. SETTING: Department of Ophthalmology, University of Vienna, Medical School, Vienna, Austria. METHODS: In this randomized patient- and examiner-masked study, 37 patients (74 eyes) with age-related cataract had bilateral small-incision cataract surgery with PCCC. Randomly, 1 eye received a hydrogel IOL and the contralateral eye, a silicone IOL. Both IOLs had open-loop haptics and a round-edged optic. Standardized digital retroillumination photographs were taken 1 day and 1, 6, 12, and 24 months after surgery to evaluate development of after-cataract on the anterior and posterior capsules by subjective grading. Opacification of the PCCC area was also objectively evaluated using new software. RESULTS: Twenty-nine patients (58 eyes) completed the 2-year follow-up. Partial closure with ongrowth at the edge of the PCCC was found in 55% in the hydrogel group and 28% in the silicone group. Total closure of the PCCC was observed in 3 eyes, 2 in the hydrogel group and 1 in the silicone group. CONCLUSION: Ongrowth onto the PCCC area was dependent on IOL material. Because of less ongrowth and more fibrotic after-cataract with silicone IOLs, the efficacy of the PCCC was higher in this group.

Short-term effect of dorzolamide hydrochloride on central corneal thickness in humans with cornea guttata.

OBJECTIVE: To investigate the short-term effect of dorzolamide hydrochloride, a topical carbonic anhydrase inhibitor, on central corneal thickness in patients with cornea guttata. DESIGN AND METHODS: In this randomized, placebo-controlled, double-masked, 3-drug crossover study, 20 patients with cornea guttata (mean endothelial cell count, 1321 cells/mm2) and 8 healthy control subjects (mean endothelial cell count, 2483 cells/mm2) were included. Study medications included 2% dorzolamide hydrochloride (Trusopt 2% eye drops; Merck & Co Inc, Whitehouse Station, NJ), 0.9% saline solution (saline placebo), and a solution identical to the carrier substance of dorzolamide in Trusopt (carrier placebo). The study drugs were applied 4 times per day for 1 day only. Central corneal thickness measurements were performed using partial coherence interferometry on every study day at baseline and after 24 hours of study medication treatment. MAIN OUTCOME MEASURES: Change in central corneal thickness. RESULTS: The mean thickening in central corneal thickness within 24 hours in eyes with cornea guttata treated with dorzolamide, saline placebo, and carrier placebo was 12.0 micro m (95% confidence interval [CI], 7.0-17.1 microm), 0.6 micro m (95% CI, -1.0 to 2.2 microm), and 1.3 micro m (95% CI, -0.1 to 2.6 microm), respectively. CONCLUSION: Application of dorzolamide for 1 day results in a slight but statistically significant thickening of central corneal thickness in patients with cornea guttata.

Intraocular lens movement caused by ciliary muscle contraction.

PURPOSE: To investigate intraocular lens (IOL) movement, measured as a change in anterior chamber depth (ACD) caused by pilocarpine-induced ciliary muscle contraction. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: In this prospective study, the ACD was measured using high-precision, high-resolution, dual-beam partial coherence interferometry in 62 pseudophakic eyes of 55 patients under pilocarpine- and cyclopentolate-induced ciliary muscle contraction and relaxation. The following were studied: 2 models of a ring-haptic IOL (designed to accommodate), a plate-haptic IOL, and 3 types of 3-piece IOLs. Measurements were performed 3 months after surgery. RESULTS: The ring-haptic IOLs and plate-haptic IOL showed a forward movement (ring haptic 43A, -116 microm; ring haptic 43E, -222 microm; plate haptic -162 microm). The 3-piece IOLs showed no change in ACD except in 1 IOL type in which there was backward movement (156 microm). CONCLUSIONS: Pilocarpine-induced ciliary muscle contraction caused forward movement of ring- and plate-haptic IOLs that resulted in an estimated accommodative amplitude of less than 0.50 diopter in most cases. The accommodating ring-haptic IOLs did not perform better than the conventional plate-haptic IOL.

Corneal endothelial cell protection with a dispersive viscoelastic material and an irrigating solution during phacoemulsification: low-cost versus expensive combination.

PURPOSE: To evaluate the protective effect on corneal endothelial cells of a low-cost and an expensive combination of a dispersive viscoelastic material and an irrigating solution during phacoemulsification. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: This prospective randomized examiner- and patient-masked study comprised 90 eyes of 45 consecutive patients with age-related cataract in both eyes. For each patient, the first eye was randomly assigned to receive hydroxypropyl methylcellulose 2% (Ocucoat) and Ringer's solution (low-cost combination) or sodium chondroitin sulfate 4%-sodium hyaluronate 3% (Viscoat) and an enriched balanced salt solution (BSS Plus) (expensive combination) during phacoemulsification. The contralateral eye received the other treatment. Endothelial cell function was evaluated by measuring corneal thickness (CT) using partial coherence interferometry, morphology assessment, and endothelial cell counts. RESULTS: The acute postoperative increase in CT was +9.8 microm in the low-cost group and +10.9 microm in the expensive group; the difference between groups was not significant. After 1 month, the CT still differed significantly from baseline in the low-cost group. Three months after surgery, the CT had returned to baseline values in both groups. There was no significant between-group difference in endothelial cell counts or morphology. CONCLUSIONS: During phacoemulsification in a nonselected patient population, there was no difference in acute postoperative corneal edema and endothelial cell morphology after 3 months between a Viscoat and BSS Plus combination and an Ocucoat and Ringer's solution combination. Eyes receiving the expensive combination had marginally faster recovery of corneal swelling by 3 months. However, the cost of Viscoat and 500 mL BSS Plus is 5 times that of Ocucoat and Ringer's solution.

Comparison of anterior chamber depth measurement methods in phakic and pseudophakic eyes.

PURPOSE: To compare anterior chamber depth (ACD) measurements in phakic and pseudophakic eyes using a slit-beam photographic technique (IOLMaster, Carl Zeiss Meditec AG) with those obtained with the laboratory prototype version of partial coherence interferometry (PCI) and with conventional applanation ultrasound in phakic eyes. SETTING: Department of Ophthalmology, Vienna General Hospital, Vienna University, Vienna, Austria. METHODS: Thirty-three ACDs of 28 patients with age-related cataract were measured preoperatively with a slit-beam photographic technique (IOLMaster) and the prototype version of PCI. In 24 eyes, the ACD was also assessed with applanation ultrasound. In addition, 34 ACDs of 18 pseudophakic patients in a different study population were examined postoperatively with the IOLMaster and PCI. RESULTS: The median ACD in the phakic eyes was 3.06 mm (range 1.93 to 3.90 mm) with the IOLMaster, 3.09 mm with PCI (range 1.49 to 4.06 mm), and 2.87 mm (range 2.18 to 3.33 mm) with applanation ultrasound. The precision was 0.005 mm for PCI and 0.015 mm for IOLMaster measurement. The median difference between the IOLMaster and PCI ACD biometry was 0.01 mm +/- 0.14 (SD) (range -0.44 to 0.17 mm) (P =.71). In pseudophakic eyes, the 2 methods showed a median difference of -0.22 mm (range -0.45 to 1.99 mm) (P >.1) and did not correlate (r = 0.21; P >.2). CONCLUSIONS: In phakic eyes, the difference between IOLMaster and PCI measurements was small and not statistically significant. In pseudophakic eyes, the difference was larger and the methods did not correlate.

Levels of adhesion molecules do not decrease after 3 months of statin therapy in moderate hypercholesterolaemia.

Studies in animals and humans indicate a pivotal role for adhesion molecules (AMs) in the pathogenesis of atherosclerosis. Whereas an association between hypercholesterolaemia and AM expression has been suggested, it is unclear whether lowering cholesterol decreases AM expression and release. We compared the effects of a 3-month treatment with standard doses of three different statins (atorvastatin, simvastatin and pravastatin) on plasma levels of circulating AM (cAM) in 75 hypercholesterolaemic patients in a randomized clinical trial. Plasma levels of circulating (c)E-selectin, circulating intercellular adhesion molecule-1 (cICAM-1) and circulating vascular cell adhesion molecule-1 (cVCAM-1) were measured before and after 3 months of therapy. None of the statins lowered plasma cAM levels and pooled analyses of all patients showed a 1.7% [95% confidence interval (CI), -1.4-4.9%] increase in cE-selectin, a 2.1% (95% CI, -0.2-4.4%) increase in cICAM-1, and a 2.7% (95% CI, -0.6-6.1%) increase in cVCAM-1 levels. cAM levels did not decrease, even in patients with a >50% decrease ( n =19) in low-density lipoprotein cholesterol levels. This study provides strong evidence that 3 months of therapy with three different statins does not decrease cAM levels, despite normalization of cholesterol levels, and a minor decrease in C-reactive protein levels in patients with moderate hypercholesterolaemia.

Comparison of ultrasound pachymetry and partial coherence interferometry in the measurement of central corneal thickness.

PURPOSE: To compare central corneal thickness (CCT) measurements obtained with 3 ultrasound pachymeters and with partial coherence interferometry (PCI) and evaluate the effect of repeated contact by a pachymetry probe on corneal thickness. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: Central corneal thickness was measured in 20 eyes of 20 healthy volunteers with 3 different ultrasound pachymeters (DGH 500, DGH Technology Inc.; SP 2000, Tomey Inc.; Paxis, Biovision Inc.) and with PCI. In each eye, 5 measurements with PCI were followed by 5 measurements with each ultrasound pachymetry device and another 5 measurements with PCI. RESULTS: The mean CCT measured with the DGH 500, SP 2000, and Paxis was 541.0 microm, 539.2 microm, and 545.1 microm, respectively. Although the differences among the 3 ultrasound pachymetry devices were within 6.0 microm, they were statistically significant (P<.05). The PCI measurements were significantly smaller (P <.05) than the ultrasound measurements: 518.8 microm before and 517.5 microm after repeated contact with the ultrasound pachymetry probe (P <.05). The mean precision (standard deviation) was 0.77 microm for PCI and between 2.40 microm and 3.58 microm for ultrasound pachymetry measurements. The correlation coefficients for the intraobserver variability were 0.999 for PCI and between 0.987 and 0.995 for ultrasound pachymetry measurements. CONCLUSIONS: Partial coherence interferometry was the more precise method of measuring CCT and had better intraobserver variability. Repeated contact by a pachymetry probe reduced corneal thickness by 1.3 microm. However, the reason for the smaller measurements with PCI than with ultrasound pachymetry remains unclear.

Effect of an acrylic intraocular lens with a sharp posterior optic edge on posterior capsule opacification.

PURPOSE: To compare the posterior capsule opacification (PCO) inhibiting effect of the sharp posterior optic edge design of the Sensar OptiEdge AR40e intraocular lens (IOL) (Allergan Surgical) with that of the round-edged design of the Sensar AR40 IOL. Setting Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: This prospective randomized patient- and examiner-masked study comprised 106 eyes of 53 patients with bilateral age-related cataract. Each patient had cataract surgery in both eyes and received an AR40 IOL in 1 eye and an AR40e IOL in the other eye. Postoperative examinations were at 1 week, 2 and 6 months, and 1 year. Digital slitlamp and digital retroillumination images of each eye were taken. The amount of PCO was assessed subjectively at the slitlamp and objectively using automated image-analysis software. RESULTS: The AR40e group had significantly less regeneratory and fibrotic PCO 1 year after surgery. The mean automated image-analysis software PCO score (scale 0 to 10) was 2.19 in the AR40 group and 1.10 in the AR40e group (P <.001). The AR40e group had less peripheral fibrotic PCO. There was no significant difference in patient-reported edge glare between the 2 IOL groups. CONCLUSIONS: The sharp-edged design of the Sensar OptiEdge AR40e IOL led to significantly less PCO than the round-edged AR40 IOL 1 year postoperatively.

Refractive outcome of cataract surgery using partial coherence interferometry and ultrasound biometry: clinical feasibility study of a commercial prototype II.

PURPOSE: To evaluate the refractive outcome of cataract patients 3 months postoperatively using optical biometry obtained with a prototype version (axial length measurement, ALM, Carl Zeiss Jena) of the commercial partial coherence interferometry (PCI) instrument (IOLMaster, Carl Zeiss Jena). SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. METHODS: Forty-five patients with age-related cataract in both eyes were scheduled for bilateral cataract surgery. Axial length was measured preoperatively with a prototype (ALM) of the commercial PCI instrument as well as with immersion ultrasound (IUS). Immersion US was performed by a single experienced investigator. In each patient, the first eye was randomly assigned to receive an intraocular lens (IOL) using the Holladay IOL power formula based on ALM or IUS biometry. The other biometric technique was used in the contralateral eye. Subjective refractive outcome was assessed 3 months postoperatively. RESULTS: Refractive outcomes with the 2 techniques did not differ significantly (P = .28). The mean numerical error (MNE) (the difference between the refractive outcome 3 months postoperatively and the predicted spherical equivalent) was 0.13 diopter (D) and 0.03 D for the ALM and IUS, respectively. The mean absolute error (MAE) (the absolute value of MNE) was 0.48 D (range 0.00 to 1.58 D) and 0.46 D (range 0.01 to 1.92 D) with the ALM and IUS, respectively. By recalculating the surgeon factor retrospectively to correct the Holladay formula to obtain a postoperative MNE of zero, a theoretical MAE of 0.46 D was obtained with both biometry techniques. CONCLUSIONS: Refractive outcome in cataract patients using PCI biometry was as good as that achieved with optimized IUS. However, the difference in axial length measured by the ALM compared to that measured by IUS must be considered when using the IOL A-constants supplied by the manufacturers.