Astigmatism analysis and reporting of surgically induced astigmatism and prediction error.

PURPOSE: To provide a method for determining the vector that, when added to the preoperative astigmatism, results in no prediction error (PE) and to specify statistical methods for evaluating astigmatism and determining the 95% confidence convex polygon. SETTING: Baylor College of Medicine, Houston, Texas, and University of Southern California, Los Angeles, California. DESIGN: Retrospective consecutive case series. METHODS: An analysis of 3 clinical trials involving toric intraocular lenses was performed. 3 formulas were evaluated (generic vergence formula with zero surgically induced astigmatism, the Barrett toric formula, and the Holladay toric formula). Scalar and vector analyses were performed on each dataset with each formula and the results compared. Since the PE was not a Gaussian distribution, a 95% convex polygon was used to determine the spread of the data. RESULTS: The mean values for the vector absolute astigmatism PEs were not different for the 3 formulas and 3 datasets. The Barrett and Holladay toric calculators were statistically superior to the zero formula for 3 intervals (0.75, 1.0, and 1.25) in the high astigmatism dataset. CONCLUSIONS: Residual astigmatism and vector absolute astigmatism PE mean values and SDs are useful but require extremely large datasets to demonstrate a statistical difference, whereas examining percentages in 0.25 diopters (D) steps from 0.25 to 2.0 D reveals differences with far fewer cases using the McNemar test for a P value. Double-angle plots are especially useful to visualize astigmatic vector PEs, and a 95% confidence convex polygon should be used when distributions are not Gaussian.

The optics of the human eye at 8.6 µm resolution.

Ocular optics is normally estimated based on up to 2,600 measurement points within the pupil of the eye, which implies a lateral resolution of approximately 175 µm for a 9 mm pupil diameter. This is because information below this resolution is not thought to be relevant or even possible to obtain with current measurement systems. In this work, we characterize the in vivo ocular optics of the human eye with a lateral resolution of 8.6 µm, which implies roughly 1 million measurement points for a pupil diameter of 9 mm. The results suggest that the normal human eye presents a series of hitherto unknown optical patterns with amplitudes between 200 and 300 nm and is made up of a series of in-phase peaks and valleys. If the results are analysed at only high lateral frequencies, the human eye is also found to contain a whole range of new information. This discovery could have a great impact on the way we understand some fundamental mechanisms of human vision and could be of outstanding utility in certain fields of ophthalmology.

Effect of Cyclosporine 0.09% Treatment on Accuracy of Preoperative Biometry and Higher Order Aberrations in Dry Eye Patients Undergoing Cataract Surgery.

PURPOSE: To determine the effect of topical cyclosporine 0.09% on ocular surface regularity and the predictive accuracy of preoperative corneal power measurements in patients undergoing cataract surgery. SETTING: Private practice. DESIGN: Open-label, multicenter, prospective study. METHODS: Seventy-five patients (75 eyes) who presented for cataract surgery evaluation with signs of dry eye disease were prescribed topical cyclosporine 0.09% for 28 days BID. Corneal curvature measurements, slit lamp exam, and Standardized Patient Evaluation of Eye Dryness (SPEED) questionnaire were evaluated at the initial and follow-up visits. Cataract surgery occurred 1 to 3 weeks after the second biometry visit. Refraction and corrected distance visual acuity measurements were performed 1-month post-surgery. The primary outcome was the difference in absolute prediction error of 1-month spherical equivalent refractive outcome before and after cyclosporine treatment. Secondary outcomes included the effect of topical cyclosporine 0.09% on ocular surface irregularity. RESULTS: Sixty-four patients completed the study. The absolute prediction error of 1-month spherical equivalent refractive outcome was 0.39 ± 0.30 D vs 0.33 ± 0.25 D (P < 0.03) before and after treatment, respectively. The proportion of eyes that achieved the target refraction was greater based on measurements after topical cyclosporine 0.09% than would have occurred using pre-treatment measurements. CONCLUSION: Cataract surgery patients with dry eye who are prescribed topical cyclosporine 0.09% BID for 28 days pre-surgery showed a statistically significant improvement in the prediction error of the spherical equivalent outcome of surgery. Other measures of dry eye severity showed significant improvements after treatment.

Review and recommendations for univariate statistical analysis of spherical equivalent prediction error for IOL power calculations.

PURPOSE: To provide a reference for study design comparing intraocular lens (IOL) power calculation formulas, to show that the standard deviation (SD) of the prediction error (PE) is the single most accurate measure of outcomes, and to provide the most recent statistical methods to determine P values for type 1 errors. SETTING: Baylor College of Medicine, Houston, Texas, and University of Southern California, Los Angeles, California, USA. DESIGN: Retrospective consecutive case series. METHODS: Two datasets comprised of 5200 and 13 301 single eyes were used. The SDs of the PEs for 11 IOL power calculation formulas were calculated for each dataset. The probability density functions of signed and absolute PE were determined. RESULTS: None of the probability distributions for any formula in either dataset was normal (Gaussian). All the original signed PE distributions were not normal, but symmetric and leptokurtotic (heavy tailed) and had higher peaks than a normal distribution. The absolute distributions were asymmetric and skewed to the right. The heteroscedastic method was much better at controlling the probability of a type I error than older methods. CONCLUSIONS: (1) The criteria for patient and data inclusion were outlined; (2) the appropriate sample size was recommended; (3) the requirement that the formulas be optimized to bring the mean error to zero was reinforced; (4) why the SD is the single best parameter to characterize the performance of an IOL power calculation formula was demonstrated; and (5) and using the heteroscedastic statistical method was the preferred method of analysis was shown.

Rethinking the optimal methods for vector analysis of astigmatism.

PURPOSE: To evaluate the accuracy and usefulness of certain methods of analyzing astigmatic vectors. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas. DESIGN: Case samples. METHODS: Using 2 sample cases for analysis of corneal surgically induced astigmatism and an actual toric intraocular lens (IOL) case, univariate analyses from the ASSORT program were compared to double-angle plots of preoperative and postoperative astigmatism and prediction errors. RESULTS: Certain univariate figures for analyzing the 2 sample cases were misleading. For the toric IOL case, some of the key outcome vectors were inaccurate. CONCLUSIONS: ASSORT's univariate analysis of astigmatic vectors can be unpredictably erroneous and misleading. Recommended vector analyses should include double-angle plots with centroids and confidence ellipses of preoperative and postoperative astigmatism and the prediction errors, along with means and standard deviations of these vector magnitudes.

The Effect of Lifitegrast on Refractive Accuracy and Symptoms in Dry Eye Patients Undergoing Cataract Surgery.

PURPOSE: To determine the effect of lifitegrast ophthalmic solution 5% on improving the tear film, biometry/keratometry, and refractive accuracy for dry eye patients scheduled for cataract surgery. PATIENTS AND METHODS: Multicenter, prospective, open-label study of 100 eyes of 100 patients undergoing cataract surgery who had a confirmed diagnosis of dry eye. Patients underwent biometry at baseline and again after a 28-day course of lifitegrast 5% BID. Primary outcome was an improvement in the accuracy of preoperative anterior corneal power measurements at predicting postoperative spherical equivalent (SE) pre- and post-lifitegrast treatment. Secondary outcomes included changes in dry eye symptoms and corneal staining. RESULTS: The accuracy of the biometry readings for the achieved refractive SE: within 0.25 D in 47% and 50% of eyes before and after the initial lifitegrast treatment, respectively; within 0.5 D in 71% and 79% of eyes before and after the initial lifitegrast treatment; and within 0.75 D in 81% and 91% of eyes before and after the initial lifitegrast treatment (p < 0.04). CONCLUSION: Lifitegrast 5% significantly improved preoperative corneal surface measurement accuracy in patients with confirmed dry eye who were scheduled for cataract surgery.

Comparison of visual performance and satisfaction with a bilateral emmetropic vs a bilateral mild myopic target using a spherical monofocal intraocular lens.

PURPOSE: To compare the binocular visual outcomes and satisfaction of patients with emmetropia or mild myopia (-0.50 diopters [D]) implanted with a bilateral spherical monofocal IOL. SETTING: Ophthalmology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. DESIGN: Prospective nonrandomized study. METHODS: This study comprised 2 groups of 30 patients each. Group 1 included patients implanted with bilateral monofocal IOLs with near emmetropic target (plano to -0.25 D). Group 2 included patients with a postoperative bilateral target of -0.50 D. Both groups underwent uncorrected and corrected distance defocus curves postoperatively and subjective questionnaires were used to investigate patient satisfaction postoperatively. RESULTS: The defocus curve showed a significant difference between Group 1 and Group 2 binocular vision (all P values <.01 except at -3.00 D where P value = .32) with Group 1 seeing significantly better than Group 2 at +1.00, +0.50, and 0 but significantly worse in all other points of the defocus. In addition, patients of Group 2 at 0 D of defocus curve (infinite) had a visual acuity close to 0 logarithm of the minimum angle of resolution (logMAR) (0.03 ± 0.04). The main outcome of Group 2 defocus curves was that, at defocus point 0 D, even if the mean refraction was -0.67 0.15 × 160, mean uncorrected logMAR visual acuity was 0.0 ± 0.06. CONCLUSIONS: Bilateral monofocal IOLs implanted with mild myopic target provided better intermediate visual acuity compared with emmetropia at a minimal cost in terms of uncorrected distance visual acuity.

Improving toric intraocular lens calculations using total surgically induced astigmatism for a 2.5 mm temporal incision.

PURPOSE: To determine in cataract surgery the total surgically induced astigmatism (SIA) that accounts for all factors that contribute to the difference between preoperative keratometric and postoperative refractive astigmatism other than any toricity of an intraocular lens (IOL). SETTING: Twenty surgical sites in the United States. DESIGN: Retrospective case series. METHODS: An analysis was performed of 4 clinical trials involving toric IOLs and nontoric IOLs in standard cataract surgery. Data included preoperative keratometry and manifest refraction measurements at multiple postoperative visits. For each eye with a nontoric IOL, the total SIA vector was calculated as the vector difference between postoperative refractive and preoperative keratometric astigmatism. The relationship between the total SIA vector and meridian of preoperative keratometric astigmatism was determined and used to develop a new calculation algorithm for toric IOL implantation. The algorithm was tested retrospectively to identify optimum candidate eyes for various cylinder power toric IOLs as well as to compare results with the Barrett toric calculator. RESULTS: The total SIA vector was a significant contributor to surgically associated astigmatic changes in eyes receiving nontoric IOLs. The total SIA vector was dependent on the preoperative steep meridian in a consistent fashion, allowing development of a new calculation algorithm for toric IOL correction. Retrospectively applying this algorithm to toric IOL cases led to significantly improved differences between toric and nontoric control populations. CONCLUSIONS: Total SIA analysis is a new approach for toric IOL surgery. Because it considers all factors that may influence outcomes, the total SIA is a useful inclusion in toric IOL surgical planning.