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Biomedical subjects

A T Leung

Publications and source records attributed to A T Leung.

At least 19 recordsLinked to original sources
PubMed2001

Effect of preoperative keratometry on refractive outcomes after laser in situ keratomileusis.

PURPOSE: To evaluate the effect of preoperative keratometry on the refractive outcome after laser in situ keratomileusis (LASIK) for myopia. SETTING: University Eye Clinic, Prince of Wales Hospital, Hong Kong, China. METHODS: In this retrospective study, the records of patients who had LASIK for myopia greater than -6.0 diopters (D) using the Chiron Automated Corneal Shaper and the Schwind Keratome-F excimer laser were reviewed. RESULTS: Laser in situ keratomileusis was performed in 167 eyes of 103 patients (mean age 34.7 years +/- 7.5 [SD]). Preoperative myopic spherical equivalent (SE) refraction was -9.0 +/- 2.0 D (range -6.0 to -13.9 D). Three months after surgery, SE refraction was -0.04 +/- 1.1 D (range +2.3 to -3.3 D); uncorrected visual acuity > or = 20/40 was present in 91.8% of 110 eyes in which emmetropia was the postoperative goal. Mean preoperative keratometry was 43.9 +/- 1.5 D (range 40.3 to 48.1 D). When eyes were stratified by the degree of preoperative myopia in 1.0 D steps, a trend toward greater undercorrection was noted in eyes with preoperative keratometry < 43.5 D than in those with steeper keratometry (> 44.5 D) in all myopia groups except the -7.0 to -7.9 D group. This difference was statistically significant in eyes with a preoperative SE of -10.0 to -10.9 D and -11.0 to -11.9 D. CONCLUSIONS: Preoperative keratometry appeared to influence the refractive outcome after myopic LASIK. Eyes with flatter corneas tended to have greater undercorrection than eyes with similar myopia and steeper corneas. Validation of these findings in larger data sets using the methodology described may improve the predictability of current LASIK nomograms, particularly in eyes with high myopia.

Adolescent↗
PubMed2000

Traumatic partial unfolding of laser in situ keratomileusis flap with severe epithelial ingrowth.

We report an unusual flap-related complication that occurred 11 months after uneventful laser in situ keratomileusis (LASIK) performed in the eye of a 50-year-old woman. She developed partial infolding of the LASIK flap in her left eye after blunt trauma. The initial diagnosis was partial flap loss and 4 weeks later, infolding of the flap was diagnosed after severe epithelial ingrowth. Surgical repositioning of the flap resulted in a best corrected visual acuity of 20/20. Clinical features that assist in the diagnosis of this unusual complication and guidelines for its management are described.

Cornea↗
PubMed2000

In situ tumbling of the AcrySof intraocular lens.

The small incision through which foldable acrylic intraocular lenses (IOLs) are implanted does not allow easy explantation of the lens in the event of intraoperative complications. Reversal of the IOL optic during insertion, although rare, can predispose to postoperative complications such as pupillary capture of the IOL, capsule bag distension syndrome, and refractive problems. Explanting the IOL can damage it, the cataract wound, or both. We describe a technique of in situ tumbling of the AcrySof IOL to correct reversed-optic implantation that preserves the integrity of the IOL and anterior segment structures.

Acrylic Resins↗
PubMed2000

Latanoprost versus timolol gel to prevent ocular hypertension after phacoemulsification and intraocular lens implantation.

PURPOSE: To evaluate the efficacy of latanoprost and timolol gel in preventing ocular hypertension in the early period after phacoemulsification and posterior chamber intraocular lens (PC IOL) implantation. SETTING: Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Hong Kong, China. METHODS: This prospective randomized double-masked clinical trial comprised patients with uncomplicated cataract having phacoemulsification with PC IOL implantation. They were randomly assigned to 1 of 3 groups: postoperative application of timolol 0.5% gel-forming solution (Timoptol-XE(R)) (Group 1), latanoprost 0.005% (Group 2), and control (Group 3). Intraocular pressure (IOP) was measured 2, 4, and 24 hours postoperatively. The anterior chamber was examined for the levels of cells and flare using slitlamp biomicroscopy. RESULTS: Group 1 had a significantly greater reduction in mean IOP 2, 4, and 24 hours after phacoemulsification and PC IOL implantation than Group 3 (P <.05). There were no significant differences between Groups 2 and 3 at any interval (P. 05). No excessive postoperative anterior chamber inflammation was observed in any group. CONCLUSIONS: A single dose of latanoprost given after phacoemulsification and PC IOL implantation did not produce a significant IOP-lowering effect when compared with a control group in the first 24 hours postoperatively. A single dose of timolol gel produced a significant postoperative IOP decrease as soon as 2 hours and up to 24 hours after surgery. Timolol gel and latanoprost are safe, but timolol is more effective than latanoprost in preventing postoperative ocular hypertension.

Adrenergic beta-Antagonists↗
PubMed2000

Scleral fixation of a capsular tension ring for severe ectopia lentis.

A 4-year-old boy with bilateral idiopathic and progressive ectopia lentis had phacoaspiration of the lens and capsular tension ring (CTR) insertion in his left eye. Postoperatively, lens capsule centration remained poor. Single-point scleral fixation of the CTR was performed and centration of the lens capsule achieved. In-the-capsule intraocular lens (IOL) implantation was tried, but excessive IOL manipulation sliced open the capsule at the equator. Anterior vitrectomy and scleral IOL fixation were required. A similar approach was adopted in the right eye with meticulous attention given to gentle maneuvers. The operation was uneventful, with good IOL centration. Three and 11 months after surgery in the right and left eye, respectively, best corrected visual acuity was 20/50 in both eyes. Scleral fixation of the CTR, accompanied by gentle IOL manipulation, is an option to improve IOL centration in patients with severe zonular deficiency.

Child, Preschool↗
PubMed2000

Pathogenesis and management of laser in situ keratomileusis flap buttonhole.

PURPOSE: To describe the clinical features and outcomes in patients who had a flap buttonhole during laser in situ keratomileusis (LASIK) and propose an etiopathogenic mechanism for this complication. SETTING: University Eye Center, Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. METHODS: Retrospective review of case records of 6 patients (6 eyes) who had a flap buttonhole during LASIK. RESULTS: The mean patient age was 38.2 years +/- 4.1 (SD) and the mean preoperative spherical equivalent (SE) refraction, -8.13 +/- 4.04 diopters (D). Mean keratometry was 44.20 +/- 1.30 D. Retreatment was performed after a mean interval of 9.2 +/- 3.2 months. Final postoperative SE refraction was -0.44 +/- 0.58 D after a mean follow-up of 59.0 +/- 5.3 weeks. No patient experienced loss of best spectacle-corrected visual acuity. CONCLUSIONS: Retreatment of eyes that have a flap buttonhole during LASIK is associated with good visual outcomes. Flap buttonholes can produce alterations in refraction, so retreatment is best performed after the refractive error has stabilized. Microkeratome malfunction may be responsible for the occurrence of a flap buttonhole during LASIK in eyes that do not have significant corneal steepening.

Adult↗
PubMed2000

Peribulbar anaesthesia with 1% ropivacaine and hyaluronidase 300 IU ml-1: comparison with 0.5% bupivacaine/2% lidocaine and hyaluronidase 50 IU ml-1.

The low toxicity of ropivacaine makes it attractive for peribulbar anaesthesia. However, its motor-sparing properties are undesirable when akinesia is important. Hyaluronidase (300 IU ml-1) promotes the onset and quality of peribulbar blockade when used with other agents. We investigated the onset and quality of ocular akinesia in 80 patients randomized to receive 1% ropivacaine plus hyaluronidase 300 IU ml-1 (group 1), or bupivacaine 0.5%/Lidocaine 2% plus 50 IU ml-1 hyaluronidase (group 2). Ocular akinesia was scored from 0 (no movement) to 8 (full movement) every 2 min for 20 min. The groups showed no difference in the rate of onset or degree of akinesia achieved (analysis of variance with repeated measures; P = 0.34). Sixty per cent of patients in group 1 and 55% in group 2 achieved akinesia scores of < or = 4 by 6 min (chi 2 test; P = 0.5). We conclude that both peribulbar solutions produce equivalent onset and quality of ocular akinesia.

Aged↗
PubMed2000

Efficacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucoma.

AIMS: To evaluate the efficacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucomas. METHODS: This retrospective study reviewed the final intraocular pressure, visual outcome, and incidence of complications in all patients with the Ahmed glaucoma valve implant performed at the Prince of Wales Hospital, Hong Kong, between June 1996 and November 1998. RESULTS: A total of 65 eyes from 60 patients were treated with the Ahmed glaucoma implant. At a mean follow up (SD, median) of 21.8 (9.2, 28. 0) months (range 6-37 months), the mean intraocular pressure was reduced from 37.0 (SD 12.1) mm Hg before the implant surgery to 16.1 (12.4) mm Hg at the last follow up after surgery. The success rate of intraocular pressure control of <22 mm Hg was achieved in 73.8% of operated eyes. Transient postoperative hypotony with shallow anterior chamber occurred in 10.8% of cases. The most common postoperative complication was the formation of encapsulated bleb (24.6%). CONCLUSIONS: The Ahmed glaucoma valve implant appears to be effective and relatively safe for treating complicated glaucomas in Chinese eyes. The success rate is comparable with those reported in non-Asian eyes. Formation of postoperative encapsulated bleb is, however, more commonly encountered.

Adolescent↗
PubMed2000

The association between cigarette smoking and ocular diseases.

OBJECTIVE: To review the effect of smoking on common ocular disorders. DATA SOURCES: Medline literature search, 1966 to 1999. STUDY SELECTION: The following key words were used: smoking; Graves' disease, age-related macular degeneration; glaucoma; cataract. DATA EXTRACTION: Epidemiological and experimental studies were reviewed. DATA SYNTHESIS: Cigarette smoking is an important risk factor for cardiovascular, respiratory, and malignant diseases. There is also a strong association between smoking and a number of common eye diseases, which include Graves' ophthalmopathy, age-related macular degeneration, glaucoma, and cataract. Despite the multifactorial aetiology of these ocular syndromes, smoking is an independent risk factor that has dose-response effects. It causes morphological and functional changes to the lens and retina due to its atherosclerotic and thrombotic effects on the ocular capillaries. Smoking also enhances the generation of free radicals and decreases the levels of antioxidants in the blood circulation, aqueous humour, and ocular tissue. Thus, the eyes are more at risk of having free-radical and oxidation attacks in smokers. CONCLUSION: Smoking, if continued, may perpetuate further ocular damage and lead to permanent blindness. Cessation of smoking and avoidance of passive smoking is advised to minimise the harmful effects of smoking on the eyes.

Cataract↗