Graham D. Barrett

Pterygium excision with conjunctival autografting: an effective and safe technique.

The optimum mode of treatment for symptomatic pterygia would combine efficacy (a low recurrence rate) with safety (freedom from sight threatening complications), and would not affect visual acuity adversely. The efficacy of pterygium excision with conjunctival autografting in a sun exposed population in which pterygia are prevalent has previously been questioned. A cross sectional review of 93 eyes of 85 patients was carried out by slit-lamp examination a minimum of 6 months (range 6-76 months) after pterygium excision and free conjunctival autografting. Case notes were reviewed to obtain details of complications and visual acuity changes related to surgery. Of six recurrences (6.5%) four of these were asymptomatic with minor recurrences. Two patterns of recurrence were identified: cross graft recurrence (three cases) and outflanking (three cases). Complications (wound dehiscence, three cases; Tenons granuloma one case; conjunctival cyst, one case) were all corrected by minor surgical revision without sequelae. Unaided acuities were unchanged or improved 3 months after surgery in 86 cases, with a minor diminution (1 Snellen line) in seven cases. This study demonstrates a low recurrence rate for a safe technique in an area in which ongoing ultraviolet light exposure levels are high and pterygia are prevalent.

Patient satisfaction and visual function after pseudophakic monovision

PURPOSE: To evaluate the visual outcomes and patient satisfaction with modified pseudophakic monovision. SETTING: Tertiary teaching hospital. METHODS: This prospective study comprised patients with emmetropia after first‐eye cataract surgery who were offered monovision for the second‐eye surgery with a moderate myopic target refraction (−1.00 to −1.50 diopters [D]). Visual acuity, contrast sensitivity, stereopsis, patient satisfaction, and degree of spectacle independence were measured preoperatively and 3 to 4 months postoperatively. RESULTS: The study evaluated 52 eyes of 26 patients with a mean anisometropia between the near eye and the distance eye of 1.16 D. Uncorrected distance visual acuity was at least 20/30 in 96% of patients, with 92% achieving N8 (J4) or better uncorrected near acuity. Good stereopsis and contrast sensitivity were maintained. Patients were generally satisfied with the surgery. One fourth of patients were completely independent of spectacles; 1 patient was totally dependent on spectacles. No patient required intraocular lens (IOL) exchange or other refractive corrective procedures. CONCLUSION: Monovision with modest refractive targets achieved good visual function and patient satisfaction without the inherent risk for troublesome visual symptoms associated with multifocal IOLs.

High-order aberrations in pseudophakia with different intraocular lenses

Purpose: To compare high‐order aberrations in patients who had cataract surgery and implantation of different types of intraocular lenses (IOLs). Setting: Sir Charles Gairdner Hospital and Lions Eye Institute, University of Western Australia, Perth, Australia. Methods: Fifty eyes of 48 patients were included in this study. The optical aberrations were measured with the Hartmann‐Shack wavefront sensor (Zyoptix, Bausch & Lomb) before and after surgery using a 5.0 mm wavefront aperture diameter for all comparisons. The eyes were divided into 4 groups according to the type of IOL (material and curvature). A fifth group of 10 eyes of 6 elderly patients with normal crystalline lenses had the same examination. Results: There was no statistical difference in high‐order aberrations between the 2 acrylic IOL groups with different curvatures (P>.05) or between the silicone and poly(methyl methacrylate) (PMMA) IOL groups (P>.05). However, the measured high‐order aberrations were significantly higher (3rd through 5th order) in the 2 acrylic IOL groups than in the PMMA and silicone IOL groups (P<.05). Conclusions: An increase in IOL high‐order aberrations contributed to the decline in retinal image quality. An IOL modifies the entire aberration pattern of the eye. There was a statistically significant increase in aberrations in patients with an acrylic IOL compared to those with a silicone or PMMA IOL. The exact mechanism is uncertain. Further study is required to optimize IOL design.

Combined small incision phacoemulsification and trabeculectomy

ABSTRACT A method of combined cataract extraction and trabeculectomy is described in which phacoemulsification is performed through a 3.5 mm incision with insertion of a foldable hydrogel lens. This procedure is suitable for most cases in which glaucoma and cataract are coincident. In an initial series of ten patients followed for nine months, all those without additional pathology achieved a corrected visual acuity of 20/40 or better. The maximum induced astigmatism was 0.5 diopters (D), with no change or a reduction in astigmatism in seven patients (70%). Astigmatic shift between week 1 and three months was minimal (average = 0.075 D), with little change thereafter. Intraocular pressures were controlled (≤21 mm Hg) without adjunctive medication in all but one of the patients at nine months. This combined procedure preserves the principal advantages of small incision phacoemulsification: low induced astigmatism, early refractive stabilization, and rapid visual rehabilitation. In addition, reducing the extent of tissue dissection may reduce the stimulus to wound healing and early filtration failure.

Intraocular lens power calculation for eyes with an axial length greater than 26.0 mm: Comparison of formulas and methods

Purpose To evaluate and compare the accuracy of formulas and methods for calculating the intraocular lens (IOL) power for eyes with an axial length (AL) greater than 26.0 mm. Setting Ein‐Tal Eye Center, Tel‐Aviv, Israel. Design Retrospective case series. Methods The postoperative refraction results in myopic eyes with an AL over 26.0 mm were compared with the predicted refractions calculated using standard formulas (Holladay 1, SRK/T, Hoffer Q, and Haigis) with optical IOL constants, User Group for Laser Interference Biometry constants, and an AL‐adjustment method and using new‐generation formulas (Barrett Universal II, Holladay 2, and Olsen). Results In 76 (71.7%) of 106 eyes, the IOL was 6.0 diopters (D) or more (Group A) and in 30 eyes (28.3%) was less than 6.0 D (Group B). In Group A, the SRK/T, Hoffer Q, Haigis, Barrett Universal II, Holladay 2, and Olsen methods met the benchmark criteria of having a prediction error of ±0.5 D in at least 71.0% of eyes and ±1.0 D in 93.0% of eyes. In Group B, only the Barrett Universal II formula and the Holladay 1 and Haigis formulas using the AL‐adjusted method met those criteria. Conclusion When selecting IOLs for high and extreme myopia, choosing appropriate formulas and methods can yield accurate refractive results that meet benchmark criteria. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Prediction of refractive outcomes with toric intraocular lens implantation

Purpose To evaluate and compare the accuracy of different methods to measure and predict postoperative astigmatism with toric intraocular lens (IOL) implantation. Setting Ein‐Tal Ophthalmology Center, Tel‐Aviv, Israel. Design Retrospective case series. Methods Postoperative corneal astigmatism was measured with 3 devices (IOLMaster 500; optical low‐coherence reflectometry [OLCR]–based Lenstar LS 900; Atlas topographer) and compared with the manifest astigmatic refractive outcome in patients with toric IOLs. The error in the predicted residual astigmatism was calculated by vector analysis according to the measurement and calculation method used to predict the required toric IOL cylinder power. Results The centroid errors in predicted residual astigmatism were against the rule with the Alcon and Holladay toric calculators (0.53 to 0.56 diopter [D]), were lower with the Baylor nomogram (0.21 to 0.26 D), and were lowest for the Barrett toric calculator (0.01 to 0.16 D) (P <.001). The Barrett toric calculator had the lowest median absolute error in predicted residual astigmatism (0.35 to 0.54 D, all devices) compared with the Alcon and Holladay toric calculators with or without the Baylor nomogram (P <.021). The Barrett toric calculator and the OLCR device achieved the most accurate results; 75.0% and 97.1% of eyes were within ±0.50 D and ±0.75 D of the predicted residual astigmatism, respectively. Conclusion Prediction of astigmatic outcomes with toric IOLs can be improved with appropriate measuring devices and methods to establish the required toric IOL power. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

A new hydrogel intraocular lens design

Abstract A new hydrogel intraocular lens was designed to improve fixation and support. The lens, IOGEL model 2000S, has a 6.00 mm optic that merges via a crescentic flange into a terminal loop for an overall diameter of 12.00 mm. The haptics are more flexible than existing loops and the design of the lens is based on a concept of minimum loop rigidity; that is, a haptic that is rigid enough to support the weight of a lens in aqueous within the capsular bag is considered adequate for modem cataract surgery. I evaluated the lens design’s safety and efficacy. Excluding patients with pre‐existing macular degeneration, the corrected acuity of all patients at last follow‐up was 20/40 or better in 100%, 20/30 or better in 95%, 20/25 to 20/20 or better in 85%, and 20/15 or better in 15%. The new haptic can accommodate compression of the capsular bag and allows early, reliable fixation. The centration of the lens was excellent early in the postoperative period and later after capsular fibrosis developed.

Laser-induced damage to transparent polymers: chemical effect of short-pulsed (Q-switched) Nd:YAG laser radiation on ophthalmic acrylic biomaterials. I. A review.

The use of short-pulsed lasers in ophthalmic surgery inspired and called for research on the damage inflicted by the laser radiation upon the acrylic polymers from which artificial intraocular lenses are made. The possible release of toxic monomers by laser-induced depolymerization is of great concern but past investigations of this phenomenon have been very limited. The present knowledge of various types of laser-induced damage to transparent polymers is reviewed with particular emphasis on the acrylic materials and intraocular lenses.

Intraocular lens calculation formulas for new intraocular lens implants

ABSTRACT Several different formulas are available for preoperative calculation of the required implant power for a desired postoperative refraction. However, the application of both theoretical and statistically derived regression formulas to the new generation of soft intraocular lens implants poses several difficulties. In this paper the calculation of an A constant for a specific intraocular hydrogel lens implant, as well as the derivation of a universal theoretical formula, is described. The theoretical formula can be applied to other implant styles with various optical configurations and composed of different biomaterials. The SRK and theoretical formulas have been applied retrospectively to a series of patients receiving an intraocular hydrogel lens implant. A comparison shows that both perform satisfactorily in predicting the desired postoperative refraction.

New regression formula for toric intraocular lens calculations.

Purpose To evaluate and compare the accuracy of 2 toric intraocular lens (IOL) calculators with or without a new regression formula. Setting Ein‐Tal Eye Center, Tel‐Aviv, Israel, and the Lions Eye Institute, Nedlands, Western Australia, Australia. Design Retrospective case series. Methods A new regression formula (Abulafia‐Koch) was developed to calculate the estimated total corneal astigmatism based on standard keratometry measurements. The error in the predicted residual astigmatism was calculated by the Alcon and Holladay toric IOL calculators with and without adjustments by the Abulafia‐Koch formula. These results were compared with those of the Barrett toric calculator. Results Data from 78 eyes were evaluated to validate the Abulafia‐Koch formula. The centroid errors in predicted residual astigmatism were against‐the‐rule with the Alcon (0.55 diopter [D]) and Holladay (0.54 D) toric calculators and decreased to 0.05 D (P < .001 [x‐axis], P = .776 [y‐axis]) and 0.04 D (P < .001 [x‐axis], P = .726 [y‐axis]) with adjustments by the Abulafia‐Koch formula. The Alcon and the Holladay toric calculators had a higher proportion of eyes within ±0.50 D of the predicted residual astigmatism with the Abulafia‐Koch formula (76.9% and 78.2%, respectively) than without it (both 30.8%). There were no significant differences between the results of the Abulafia‐Koch‐modified Alcon and the Holladay toric calculators and those of the Barrett toric calculator. Conclusion Adjustment of commercial toric IOL calculators by the Abulafia‐Koch formula significantly improved the prediction of postoperative astigmatic outcome. Financial Disclosure Dr. Abulafia received a speaker’s fee from Haag‐Streit AG. Dr. Barrett has licensed the Barrett Toric Calculator to Haag‐Streit AG. Dr. Koch is a consultant to Alcon Laboratories, Inc., Abbott Medical Optics, Inc., and Revision Optics, Inc. Dr. Hill is a paid consultant to Haag‐Streit AG and Alcon Laboratories, Inc. None of the other authors has a financial or proprietary interest in any material or method mentioned.