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Biomedical subjects

D S Lam

Publications and source records attributed to D S Lam.

At least 73 records · Page 4Linked to original sources
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

Congenital hypertrophy of the retinal pigment epithelium and APC mutations in two Chinese families with familial adenomatous polyposis.

PURPOSE: Congenital hypertrophy of the retinal pigment epithelium (CHRPE) exists almost exclusively among familial adenomatous polyposis (FAP) patients with adenomatous polyposis coli (APC) mutations between codon 413 in exon 9 and codon 1387 in exon 15. We investigated the locality of APC mutations in relationship to the occurrence of CHRPE in two Chinese families with FAP. METHODS: Genomic DNA of available members of two unrelated Chinese FAP families was investigated for sequence alteration in the APC gene by polymerase chain reaction and direct sequencing. All subjects were examined by binocular indirect ophthalmoscopy (BIO) for CHRPE. RESULTS: A mutation in exon 6, Arg216Stop, was identified in one patient with FAP and CHRPE. An Arg283Stop mutation in exon 8 was found in 5 members in another family; 4 of them had FAP and all had small hypopigmented white lesions, probably a new type of CHRPE. CONCLUSIONS: We found two mutations, Arg216Stop and Arg283Stop, upstream of codon 413 in FAP patients presenting with CHRPE. Arg283Stop has not previously been reported in such patients. A large-scale study on CHRPE and APC mutations in Chinese FAP patients is required to affirm their inter-relationships and the significance of the hypopigmented white lesions.

Adenomatous Polyposis Coli↗
PubMed2000

In vitro contractile responses of detrusor to carbachol and neurokinin A, in children with recurrent urinary tract infection or day wetting.

OBJECTIVE: To investigate whether a history of recurrent urinary tract infection (UTI) and/or the presence of day-wetting/urge symptoms might influence the contractile responses to the cholinergic agonist carbachol or to the sensory neuropeptide neurokinin A (NKA) in the urinary bladder in children. PATIENTS AND METHODS: Small detrusor strips were taken from the margin of the cystotomy incision of the bladder dome during surgery to correct vesico-ureteric reflux (VUR) in 62 children (aged 4 months to 12 years) or for unrelated bladder conditions in five controls (aged 3 months to 13 years). Concentration-response curves to carbachol and NKA were constructed using organ-bath techniques, and results compared for age, sex, weight of the detrusor strip, UTI history or day-wetting syndrome. RESULTS: The contractile responses to NKA were no different for any of the features investigated. The contractile response to carbachol and NKA in detrusor from control and VUR patients was not significantly different. The children with a history of UTI were significantly older than those without. The contractility in response to carbachol was greater in older girls (aged 4-12 years) than younger girls (< 4 years) and than in all boys (< 4 years and 4-12 years; ANOVA P = 0.013). The mean (SEM) maximum contractile response to carbachol in the group of 20 young children (4-30 months) with previous UTI was 3.0 (0.3) g, whereas the maximum response in the age-matched group of 11 without UTI was 1.8 (0.3) g (P = 0.046). There were no significant differences in maximum responses between those with day-wetting and those without (aged > 4 years), although there was a significant difference in pD2 value, at 6.19 (0.13) and 5.58 (0.14), respectively (P = 0.018). CONCLUSION: Carbachol produced a larger contractile response in detrusor from children with a history of UTI than from those without, indicating possible alterations in muscarinic receptor characteristics. An increased sensitivity to muscarinic stimulation in day-wetting children was also suggested, whereas NKA is unlikely to be involved in any of these pathophysiological conditions.

Adolescent↗
PubMed2000

Angiotensin II in child urinary bladder: functional and autoradiographic studies.

OBJECTIVES: To investigate the receptors for angiotensin II (AII, reported to be a potent contractile agent in human urinary bladder), using functional and autoradiographic techniques in child and adult bladder specimens. Materials and methods Bladder specimens were obtained from 61 children (aged 4 months to 12 years) undergoing ureteric reimplantation for vesico-ureteric reflux, and from 10 adults undergoing cystectomy. After overnight storage, the mucosa was removed and isometric contractions obtained from detrusor muscle strips in the presence of phosphoramidon (10 micromol/L). Only one concentration of AII was added to each preparation because of tachyphylaxis. The response to KCl (124 mmol/L) was 43% of that to carbachol (100 micromol/L). Sections of child bladder were radio-labelled with the ligand [125I]Sar1,Ile8-AII and binding sites visualized using emulsion autoradio- graphy. RESULTS: The potency of AII was similar in child and adult detrusor strips, with mean (SEM) pD2 values of 6.9 (1.0) (n = 25) and 6.7 (0.2) (n = 9) respectively, and the maximum responses (to 10 micromol/L AII) rather low (39% and 49%, respectively, P > 0.05), compared with carbachol (100 micromol/L). There were no age- or gender-related differences. Responses to AII in strips from children under 3 years old were antagonized by the AT1 receptor antagonist losartan (1 micromol/L) but not by the AT2 receptor antagonist PD 123319 (1 micromol/L), indicating interaction with the AT1 receptor. Sections of child bladder radiolabelled with [125I]Sar1,Ile8-AII showed moderate specific binding over detrusor muscle and arterioles, with denser specific binding over subepithelial blood vessels. Specific binding was inhibited by co-incubation with losartan (10 micromol/L) but not with PD 123319 (10 micromol/L). CONCLUSION: AII was a weak contractile agent of detrusor strips, with no significant differences in potency between child and adult bladder samples. These data show the presence of functional AT1 but not AT2 receptors in child detrusor smooth muscle.

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↗