Mitchell P. Weikert

Contribution of posterior corneal astigmatism to total corneal astigmatism.

PURPOSE: To determine the contribution of posterior corneal astigmatism to total corneal astigmatism and the error in estimating total corneal astigmatism from anterior corneal measurements only using a dual‐Scheimpflug analyzer. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. DESIGN: Case series. METHODS: Total corneal astigmatism was calculated using ray tracing, corneal astigmatism from simulated keratometry, anterior corneal astigmatism, and posterior corneal astigmatism, and the changes with age were analyzed. Vector analysis was used to assess the error produced by estimating total corneal astigmatism from anterior corneal measurements only. RESULTS: The study analyzed 715 corneas of 435 consecutive patients. The mean magnitude of posterior corneal astigmatism was −0.30 diopter (D). The steep corneal meridian was aligned vertically (60 to 120 degrees) in 51.9% of eyes for the anterior surface and in 86.6% for the posterior surface. With increasing age, the steep anterior corneal meridian tended to change from vertical to horizontal, while the steep posterior corneal meridian did not change. The magnitudes of anterior and posterior corneal astigmatism were correlated when the steeper anterior meridian was aligned vertically but not when it was aligned horizontally. Anterior corneal measurements underestimated total corneal astigmatism by 0.22 @ 180 and exceeded 0.50 D in 5% of eyes. CONCLUSIONS: Ignoring posterior corneal astigmatism may yield incorrect estimation of total corneal astigmatism. Selecting toric intraocular lenses based on anterior corneal measurements could lead to overcorrection in eyes that have with‐the‐rule astigmatism and undercorrection in eyes that have against‐the‐rule astigmatism. Financial Disclosure: The authors received research support from Ziemer Group. In addition, Dr. Koch has a financial interest with Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Calhoun Vision, Inc., NuLens, and Optimedica Corp.

Correcting astigmatism with toric intraocular lenses: Effect of posterior corneal astigmatism

Purpose To evaluate the impact of posterior corneal astigmatism on outcomes with toric intraocular lenses (IOLs). Setting Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Design Case series. Methods Corneal astigmatism was measured using 5 devices before and 3 weeks after cataract surgery. Toric IOL alignment was recorded at surgery and at the slitlamp 3 weeks postoperatively. The actual corneal astigmatism was calculated based on refractive astigmatism 3 weeks postoperatively and the effective toric power calculated with the Holladay 2 formula. The prediction error was calculated as the difference between the astigmatism measured by each device and the actual corneal astigmatism. Vector analysis was used in all calculations. Results With the IOLMaster, Lenstar, Atlas, manual keratometer, and Galilei (combined Placido–dual Scheimpflug analyzer), the mean prediction errors (D) were, respectively, 0.59 @ 89.7, 0.48 @ 91.2, 0.51 @ 78.7, 0.62 @ 97.2, and 0.57 @ 93.9 for with‐the‐rule (WTR) astigmatism (60 to 120 degrees), and 0.17 @ 86.2, 0.23 @ 77.7, 0.23 @ 91.4, 0.41 @ 58.4, and 0.12 @ 7.3 for against‐the‐rule (ATR) astigmatism (0 to 30 degrees and 150 to 180 degrees). In the WTR eyes, there were significant WTR prediction errors (0.5 to 0.6 diopters [D]) by all devices. In ATR eyes, WTR prediction errors were 0.2 to 0.3 D by all devices except the Placido–dual Scheimpflug analyzer (all P<.05 with Bonferroni correction). Conclusions Corneal astigmatism was overestimated in WTR by all devices and underestimated in ATR by all except the Placido–dual Scheimpflug analyzer. A new toric IOL nomogram is proposed. Financial Disclosure Drs. Koch, Weikert, and Wang received research support from Ziemer USA, Inc. Dr. Koch has a financial interest with Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Optimedica Corp., and Ziemer USA, Inc. No other author has a financial or proprietary interest in any material or method mentioned.

Comparison of Corneal Powers Obtained from 4 Different Devices

PURPOSE To assess the repeatability and comparability of anterior corneal power values obtained from the Galilei Dual Scheimpflug Analyzer (Ziemer, Port, Switzerland), Humphrey Atlas corneal topographer (Carl Zeiss, Jena, Germany), IOLMaster (Carl Zeiss), and a manual keratometer (Bausch & Lomb Inc, Rochester, New York, USA). DESIGN Prospective, comparative study. METHODS Prospectively, 20 subjects were enrolled. Three sets of corneal power measurements were obtained by a single observer using the Galilei, Atlas topographer, IOLMaster, and manual keratometer. Repeatability of the 3 measurements from each device was evaluated by means of coefficient of variation, standard deviation (SD), and intraclass correlation coefficient. An analysis of variance was used to compare the differences in corneal powers among devices. The Bland and Altman method also was performed to assess agreement in measurements between devices. Vector analysis was used to compare the astigmatism values obtained from different devices. RESULTS For each device, the coefficient of variation of repeated measurements was lower than 0.22%. The SD of 3 repeated measurements ranged from 0.042 to 0.096 diopters (D). The intraclass correlation coefficients were higher than 0.99 in all devices. Mean central corneal powers were 43.80 D, 43.88 D, 43.92 D, and 43.76 D for the Galilei, Atlas, IOLMaster, and manual keratometer, respectively. SDs of the differences between devices ranged from 0.07 D for Galilei and IOLMaster to 0.14 D for Galilei and Atlas. For astigmatism, the mean astigmatism values for the Galilei, Atlas, IOLMaster, and manual keratometer were 0.54 D at 84 degrees, 0.51 D at 88 degrees, 0.62 D at 88 degrees, and 0.52 D at 87 degrees, respectively. CONCLUSIONS The corneal power measurements from these 4 devices were highly reproducible, comparable, and correlated.

Correction of Astigmatism During Cataract Surgery: Toric Intraocular Lens Compared to Peripheral Corneal Relaxing Incisions

PURPOSE To compare the efficacy of astigmatic correction achieved at the time of cataract surgery using toric intraocular lens (IOL) implantation versus peripheral corneal relaxing incisions. METHODS A retrospective review assessed the outcomes of phacoemulsification cataract surgery performed between January 2006 and January 2008 by a single surgeon. Patients receiving a toric IOL (toric IOL group) or peripheral corneal relaxing incisions (relaxing incisions group) were included in the study. Main outcome variables included postoperative uncorrected distance visual acuity (UDVA) and manifest refractive cylinder. Each treatment modality was stratified by amount of preoperative keratometric astigmatism into three groups (low, moderate, and high astigmatism) for comparative analysis. RESULTS A total of 192 eyes were included in the study; 77 received a toric IOL and 115 received peripheral corneal relaxing incisions. Preoperative data were not significantly different between the two groups except regarding keratometric astigmatism, which was higher in the toric IOL group (P<.05). Average postoperative astigmatism was 0.42 diopters (D) and 0.46 D in the toric and relaxing incisions groups, respectively. In subgroup analysis, no statistical significance separated the two treatment options in terms of amount of surgically induced astigmatism or residual astigmatism. Eyes with astigmatism ≥2.26 D were more likely to achieve 20/40 UDVA from a toric IOL. CONCLUSIONS Toric IOL implantation and peripheral corneal relaxing incisions yielded similar results regarding surgical correction of astigmatism at the time of phacoemulsification cataract surgery. Both treatment modalities achieved comparable results with mild-to-moderate astigmatism. Higher degrees of astigmatism favor use of a toric IOL.

Update on bimanual microincisional cataract surgery.

Purpose of review The purpose of this article is to highlight the major issues associated with bimanual microincisional cataract surgery and to review the recent literature addressing this subject. Recent findings Bimanual microincisional cataract surgery has been performed successfully using all of the major phacoemulsification platforms. Technological advances in ultrasound power management and fluidics have improved the safety profile and efficiency of this technique. New intraocular-lens designs and surgical maneuvers permit intraocular-lens insertion through corneal incisions measuring 2 mm or less. Clinical results achieved with bimanual microincisional cataract surgery and new microincision lenses are comparable to those obtained with conventional coaxial phacoemulsification and established intraocular lenses. Summary Bimanual microincisional cataract surgery is a promising surgical technique that continues to grow as phacoemulsification technology and intraocular-lens designs evolve.

Noninvasive Assessment of Tear Stability with the Tear Stability Analysis System in Tear Dysfunction Patients

PURPOSE To evaluate tear film stability in patients with tear dysfunction and an asymptomatic control group by using the novel, noninvasive Tear Stability Analysis System (TSAS). METHODS In this prospective case-control study, 45 patients with dysfunctional tear syndrome (DTS) were stratified into three groups (1, 2, and 3/4) based on clinical severity, with higher scores indicating more severe symptoms; 25 asymptomatic control subjects were evaluated. TSAS measurements were performed with the RT-7000 Auto Refractor-Keratometer (Tomey Corporation, Nagoya, Japan). Images of ring mires projected onto the cornea every second for 6 seconds were captured and analyzed. Focal changes in brightness were calculated as numerical ring breakup (RBU) values, and the elapsed time when the cumulative values (RBU sum) exceeded a threshold was defined as the ring breakup time (RBUT). RESULTS RBUTs in the DTS groups were all significantly lower than those in the control subjects, with the lowest values found in DTS 3/4. RBUT was significantly shorter in DTS 3/4 than in DTS 1 (P<0.001). The change in RBU sum over a 6-second period in the DTS groups combined or between the individual groups was statistically significant (P<0.001), as was the difference between the 1- and 6-second values. For distinguishing between asymptomatic controls and DTS, the sensitivity and specificity of a 5.0-second RBUT cutoff were 82.0% and 60.0%, respectively. CONCLUSIONS The TSAS may be a useful, noninvasive instrument for evaluating tear stability and for classifying DTS severity.

Iris-fixated Posterior Chamber Intraocular Lenses in Children

PURPOSE To report the short-term outcomes and complications of iris-fixated posterior chamber intraocular lenses (PCIOL) in the pediatric population. DESIGN Retrospective, observational case study. METHODS Twelve consecutive pediatric patients (17 eyes) underwent placement of foldable iris-sutured PCIOLs between September 1, 2004 and September 30, 2007 by two anterior segment surgeons at a single academic center. Outcome measures included change in visual acuity (VA) and complications. RESULTS In our series, there was a higher rate of dislocation of iris-sutured IOLs in patients with a history of ectopia lentis resulting from Marfan syndrome or hereditary or idiopathic causes than in patients being treated for aphakia resulting from other causes (45% vs 0%). Mean final VA improved by 0.23 logarithm of the minimum angle of resolution units from preoperative baseline. One eye of a Marfan patient sustained a retinal detachment eight months after dislocation of the PCIOL, and one patient experienced iris capture of the IOL after surgery. CONCLUSIONS Iris-fixated IOLs are reasonable alternative to transsclerally sutured IOLs to correct aphakia in pediatric patient. Dislocation of the IOLs can occur, however, and there is concern for suture degradation over time. The procedure should be considered with caution in pediatric patients.

Long-term Supplementation With n-6 and n-3 PUFAs Improves Moderate-to-Severe Keratoconjunctivitis Sicca: A Randomized Double-Blind Clinical Trial.

Purpose: Supplementation with gamma-linolenic acid (GLA) and omega-3 (n-3) polyunsaturated fatty acids (PUFAs) has been found to decrease the production of disease-relevant inflammatory mediators that are implicated in the pathogenesis of chronic dry eye. This study evaluated the effect of a supplement containing both GLA and n-3 PUFAs on signs and symptoms of moderate-to-severe keratoconjunctivitis sicca in postmenopausal patients. Methods: This multicenter, double-masked placebo-controlled clinical trial enrolled 38 patients (both eyes) with tear dysfunction who were randomized to supplemental GLA + n-3 PUFAs or placebo for 6 months. Disease parameters, including Ocular Surface Disease Index, Schirmer test, tear breakup time, conjunctival fluorescein and lissamine green staining, and topographic corneal smoothness indexes (surface asymmetry index and surface regularity index), were assessed at baseline and at 4, 12, and 24 weeks. The intensity of dendritic cell CD11c integrin and HLA-DR expression was measured in conjunctival impression cytologies. Results: The Ocular Surface Disease Index score improved with supplementation and was significantly lower than placebo (21 ± 4 vs. 34 ± 5) after 24 weeks (P = 0.05, n = 19 per group). The surface asymmetry index was significantly lower in supplement-treated subjects (0.37 ± 0.03, n = 15) than placebo (0.51 ± 0.03, n = 16) at 24 weeks (P = 0.005). Placebo treatment also significantly increased HLA-DR intensity by 36% ± 9% and CD11c by 34% ± 7% when compared with supplement treatment (n = 19 per group, P = 0.001, 24 weeks). Neither treatment had any effect on tear production, tear breakup time, or corneal or conjunctival staining. Conclusions: Supplemental GLA and n-3 PUFAs for 6 months improved ocular irritation symptoms, maintained corneal surface smoothness, and inhibited conjunctival dendritic cell maturation in patients with postmenopausal keratoconjunctivitis sicca. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00883649.

Healing changes in clear corneal cataract incisions evaluated using Fourier-domain optical coherence tomography

PURPOSE: To evaluate the long‐term wound‐healing changes in clear corneal cataract incisions using Fourier‐domain optical coherence tomography (OCT). SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. DESIGN: Case series. METHODS: Multiple OCT images were obtained in consecutive eyes that had phacoemulsification 1 day to 180 months previously. The incision midpoint was measured with OCT. The presence of Descemet membrane detachment, posterior wound gape, and posterior wound retraction was assessed. The depth of wound retraction along the incision and the radial length of the incision were measured. The percentage of wound retraction relative to radial incision length was calculated. RESULTS: Descemet membrane detachment was present in 37.1% of eyes 1 day postoperatively and in 4.5% of eyes at 1 to 3 months (P=.005); it was absent after 3 months. Posterior wound gape appeared in 85.7% of eyes at 1 day and in 31.8% at 1 to 3 months (P<.001); it was absent after 3 months. Posterior wound retraction appeared in 33.3% of eyes at 2 to 3 weeks, in 75.0% at 1 to 3 years, and in 90.5% after 3 years (P<.001). The mean wound retraction was 120 μm ± 46 (SD) (range 24 to 225 μm), which was 7.5% ± 3.1% (range 2.0% to 13.4%) of the radial incision length. CONCLUSION: Descemet membrane detachment and posterior wound gape appeared in the early postoperative period and persisted for up to 3 months, whereas posterior wound retraction developed later and was present in more than 90% of eyes after 3 years, indicating long‐term wound remodeling. Financial Disclosure: Dr. Koch has financial interest with Alcon Laboratories, Abbott Medical Optics, Calhoun Vision, and Optimedica. No other author has a financial or proprietary interest in any material or method mentioned.

Iris-sutured intraocular lenses for ectopia lentis in children

PURPOSE: To compare outcomes and complications of pars plana lensectomy–vitrectomy (PPL–PPV) for the management of ectopia lentis in children with and without a foldable iris‐sutured intraocular lens (IOL). SETTING: Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA. METHODS: This study comprised 22 eyes of 12 consecutive pediatric patients with ectopia lentis who had PPL–PPV by the same vitreoretinal surgeon with (12 eyes; Group L) or without (10 eyes; Group A) insertion of a foldable iris‐sutured IOL between June 1998 and October 2006. Outcome measures included the proportion of eyes achieving visual acuity of 20/40 or better, mean logMAR visual acuity, and complications. RESULTS: There was no statistically significant difference between the 2 groups in the proportion of eyes achieving a visual acuity of 20/40 or better (Group A: 5/10; Group L: 10/12) (P = .17) or the mean postoperative best corrected logMAR visual acuity (Group A: 0.41 [20/52]; Group L: 0.24 [20/35]) (P = .18). Complications included IOL dislocation in 4 (33%) of 12 eyes in Group L (95% confidence interval, 11%‐65%). Eyes with dislocated IOLs had retrieval with resuturing of the IOL to the iris and had a mean visual acuity of 20/27 at the last follow‐up. No retinal detachment was observed. CONCLUSION: Pars plana lensectomy–vitrectomy with iris‐fixation of a foldable IOL for the management of ectopia lentis yielded visual outcomes as least as good as those of optically corrected aphakia with a significant risk for dislocation.