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Biomedical subjects

D S Fan

Publications and source records attributed to D S Fan.

At least 19 recordsLinked to original sources
PubMed2001

Ultrasound biomicroscopy of conventional and sutureless pars plana sclerotomies: a comparative and longitudinal study.

PURPOSE: To report the rate of ultrasonically visible vitreous incarceration and longitudinal changes of incarcerated vitreous in pars plana sclerotomies after conventional suturing or sutureless technique using ultrasound biomicroscopy. METHODS: Twenty-five consecutive eyes (25 patients) undergoing primary three-port pars plana vitrectomy participated. The first 16 pars plana vitrectomies were performed with standard conventional sutured sclerotomies, and the following nine pars plana vitrectomies were performed with modified sutureless sclerotomies. Patient demographics, diagnoses, procedures, and complications were recorded. Each patient had ultrasound biomicroscopy performed 1 week before surgery, and also after surgery at 1 week, 2 weeks, 3 weeks, 4 weeks, 2 months, 3 months, and 6 months. Visible vitreous incarceration was graded as 0 to 3. RESULTS: Vitreous incarceration was seen in 41 of 48 sclerotomies (85.4%) in the conventionally sutured group, and in 23 of 27 sclerotomies (85.2%) in the sutureless group, with no significant difference in severity among sclerotomies within each group and between the two groups. There was a significant difference in the rate of vitreous incarceration between diabetic patients with proliferative retinopathy and others (P =.002). No progressive change of visible vitreous incarceration was noted in any eye during the 6-month postoperative period. No sclerotomy-related complications occurred during the study period. CONCLUSIONS: Ultrasound biomicroscopy showed no difference in the amount of visible vitreous incarceration in conventionally sutured or sutureless sclerotomies. There was no visible longitudinal change in the incarcerated vitreous during the 6 months of follow-up in uncomplicated cases.

Adult↗
PubMed2001

A prospective study on ocular hypertensive and antiinflammatory response to different dosages of fluorometholone in children.

OBJECTIVE: To investigate the ocular hypertensive and antiinflammatory response to different dosages of fluorometholone (FML). DESIGN: Prospective clinical trial with randomization of fellow eyes to different postoperative treatment. PARTICIPANTS: Thirty-one consecutive children undergoing bilateral symmetrical strabismus operation. INTERVENTION: Among 31 children who received bilateral squint operations, one eye was randomized to receive topical FML six times daily (group 1), whereas the other eye received topical FML three times daily (group 2), both for 4 weeks. Intraocular pressure (IOP) and antiinflammatory response were measured serially in the postoperative period for 8 weeks. MAIN OUTCOME MEASURES: Intraocular pressure was measured on the day before surgery and on postoperative days 1, 3, 6, 13, 20, 27, 41, and 55. The antiinflammatory response was also assessed subjectively and objectively at days 6, 13, 20, and 27 after the operations. Peak IOP, net increase in IOP, and antiinflammatory responses in the two study groups were analyzed. RESULTS: Thirty-one children, age 3 to 9 years, (mean +/- standard deviation [SD], 5.52 +/- 1.81) participated in the study. Intraocular pressure increased significantly in both groups compared with the preoperative values (P < 0.001). The peak IOP ranged from 12.00 to 31.00 mmHg and 12.30 to 25.00 mmHg in groups 1 and 2, respectively. The mean peak IOP (19.00 +/- 5.06 mmHg vs. 17.13 +/- 3.32 mmHg) was significantly higher in group 1 (P < 0.001). The net increase in IOP was similar (mean +/- SD, 4.37 +/- 4.79 vs. 2.57 +/- 3.32 mmHg; P = 0.005). Ranges of the net IOP increase were -1.00 to 16.00 mmHg and -2.50 to 10.30 mmHg in groups 1 and 2, respectively. Children in group 1 reached the peak IOP earlier than those in group 2 (median, 6 vs. 13 days; P = 0.033). However, there was no significant difference in antiinflammatory response between the two groups. CONCLUSIONS: Ocular hypertension occurs in a dose-dependent manner in children treated with FML. Children in group 1 had a quicker onset and more severe ocular hypertensive response than those in group 2. It would be desirable to monitor the IOP regularly when FML is used with a high frequency and for a long duration in children.

Administration, Topical↗
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

Triple transduction with adeno-associated virus vectors expressing tyrosine hydroxylase, aromatic-L-amino-acid decarboxylase, and GTP cyclohydrolase I for gene therapy of Parkinson's disease.

Parkinson's disease (PD), a neurological disease suited to gene therapy, is biochemically characterized by a severe decrease in the dopamine content of the striatum. One current strategy for gene therapy of PD involves local production of dopamine in the striatum achieved by inducing the expression of enzymes involved in the biosynthetic pathway for dopamine. We previously showed that the coexpression of tyrosine hydroxylase (TH) and aromatic-L-amino-acid decarboxylase (AADC), using two separate adeno-associated virus (AAV) vectors, resulted in more effective dopamine production and more remarkable behavioral recovery in 6-hydroxydopamine-lesioned parkinsonian rats, compared with the expression of TH alone. Not only levels of TH and AADC but also levels of tetrahydrobiopterin (BH4), a cofactor of TH, and GTP cyclohydrolase I (GCH), a rate-limiting enzymes for BH4 biosynthesis, are reduced in parkinsonian striatum. In the present study, we investigated whether transduction with separate AAV vectors expressing TH, AADC, and GCH was effective for gene therapy of PD. In vitro experiments showed that triple transduction with AAV-TH, AAV-AADC, and AAV-GCH resulted in greater dopamine production than double transduction with AAV-TH and AAV-AADC in 293 cells. Furthermore, triple transduction enhanced BH4 and dopamine production in denervated striatum of parkinsonian rats and improved the rotational behavior of the rats more efficiently than did double transduction. Behavioral recovery persisted for at least 12 months after stereotaxic intrastriatal injection. These results suggest that GCH, in addition to TH and AADC, is important for effective gene therapy of PD.

Animals↗
PubMed2000

Gene therapy of Parkinson's disease using adeno-associated virus (AAV) vectors.

Parkinson's disease (PD) is characterized by the progressive loss of the dopaminergic neurons in the substantia nigra and a severe decrease in dopamine in the striatum. A promising approach to the gene therapy of PD is intrastriatal expression of dopamine-synthesizing enzymes [tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC)]. The most appropriate gene-delivery vehicles for neurons are adeno-associated virus (AAV) vectors, which are derived from non-pathogenic virus. Therefore, TH and AADC genes were introduced into the striatum in the lesioned side using separate AAV vectors in parkinsonian rats, and the coexpression of TH and AADC resulted in better behavioral recovery compared with TH alone. Another strategy for gene therapy of PD is the protection of dopaminergic neurons in the substantia nigra using an AAV vector containing a glial cell line-derived neurotrophic factor (GDNF) gene. Combination of dopamine-supplement gene therapy and GDNF gene therapy would be a logical approach to the treatment of PD.

Animals↗
PubMed2000

Absence of trabecular meshwork-inducible stretch response (TISR)/oculomedin gene and proximal promoter mutation in primary open angle glaucoma patients.

We investigated the coding exon and promoter sequence in the trabecular meshwork-inducible stretch response (TISR)/oculomedin gene for mutations in Chinese primary open angle glaucoma (POAG) subjects. The entire TISR/oculomedin coding sequence, together with 138 bp of promoter sequence 5' to the start codon and 170 bp of the 3' untranslated region in 110 Chinese POAG patients and 108 unrelated control subjects without glaucoma, aged 50 years or above, were screened for alterations by DNA sequencing. One heterozygous sequence alteration, K28E, was identified in one control subject, and two homozygous sequence alterations, K28K and 135+36delC, were universally found in every sample. As a result, no common TISR/ oculomedin coding sequence nor any proximal promoter mutation that causes POAG was found. The effect of TISR/ oculomedin in glaucoma has yet to be established.

Adolescent↗
PubMed2000

Ocular hypertensive response to topical dexamethasone in children: a dose-dependent phenomenon.

OBJECTIVE: To investigate the ocular-hypertensive response to different dosages of topical dexamethasone eye drops in Chinese children. DESIGN: Prospective, randomized clinical trial. PARTICIPANTS: Thirty-one consecutive children undergoing bilateral strabismus surgery. INTERVENTION: Topical dexamethasone (0.1%) was administered to children undergoing bilateral strabismus surgery. They were all less than 10 years of age. One eye was randomized to receive a regimen of four times daily, and another received a twice daily regimen. Intraocular pressure (IOP) was serially measured in the postoperative period for 4 weeks or more. Topical steroids were discontinued if IOP was 30 mmHg or more. MAIN OUTCOME MEASURES: Intraocular pressure was measured on the day before the surgery, on postoperative days 1, 3, 5, 8, 12, 15, 22, 29, and 2 weeks thereafter until the IOP reached preoperative levels. Peak IOP, IOP net increase, and time to reach an IOP more than 20 mmHg in the two study groups were analyzed. RESULTS: A total of 31 patients (20 male, 11 female) were examined. The mean age was 5.8 +/- 2.0 years (range, 2-10 years). Preoperative IOP in groups treated twice daily and four times daily were similar. After topical dexamethasone treatment, both groups showed a significant rise in peak IOP compared with preoperative values (twice daily, 25.2 +/- 6.8 mmHg vs. 14.3 +/- 2.4 mmHg, P < 0.001; four times daily, 28.7 +/- 6.9 mmHg vs. 14.3 +/- 2.9 mmHg, P < 0.001). The peak IOP was significantly higher in the four times daily group (P < 0.001), as was the net increase in IOP (twice daily, 10.9 +/- 5.8 mmHg vs. four times daily, 14.5 +/- 6.4 mmHg; P < 0.001). There was no difference in time for both groups to achieve the peak IOP, but the time to exceed its upper normal value (20 mmHg) was shorter in the four times daily group (twice daily, 12.3 +/- 9.1 days vs. four times daily, 10.0 +/- 7.4 days; P < 0.05). CONCLUSIONS: In children treated with topical dexamethasone, ocular hypertension occurs in a dose-dependent manner. Children in the four times daily group had a quicker onset and more severe ocular hypertensive response than the twice daily group. Nevertheless, even the twice daily regimen produced significant IOP rise, suggesting that dexamethasone use in children should be avoided if possible, and it would be desirable to monitor the IOP twice weekly when it is administered to children.

Administration, Topical↗
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↗