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Biomedical subjects

Wai-Man Chan

Publications and source records attributed to Wai-Man Chan.

At least 73 records · Page 4Linked to original sources
PubMed2004

Mutations in a human ROBO gene disrupt hindbrain axon pathway crossing and morphogenesis.

The mechanisms controlling axon guidance are of fundamental importance in understanding brain development. Growing corticospinal and somatosensory axons cross the midline in the medulla to reach their targets and thus form the basis of contralateral motor control and sensory input. The motor and sensory projections appeared uncrossed in patients with horizontal gaze palsy with progressive scoliosis (HGPPS). In patients affected with HGPPS, we identified mutations in the ROBO3 gene, which shares homology with roundabout genes important in axon guidance in developing Drosophila, zebrafish, and mouse. Like its murine homolog Rig1/Robo3, but unlike other Robo proteins, ROBO3 is required for hindbrain axon midline crossing.

Adult↗
PubMed2004

Hemorrhagic complication in an unsuspected macular choroidal melanoma.

PURPOSE: To report a rare presentation of a hemorrhagic complication in a patient with unsuspected macular choroidal melanoma. DESIGN: Interventional case report. METHODS: A 32-year-old Chinese woman presented with disturbance of her left central vision. A hemorrhagic mass at the macula was noticed that was evacuated by submacular surgery. RESULTS: The mass expanded rapidly into a mushroom configuration after surgery. Fine-needle aspiration confirmed the diagnosis of malignant choroidal melanoma, and enucleation followed. Histology demonstrated moderately large epithelioid tumor cells with prominent nucleoli. The sclera was intact, and the optic nerve was not involved. The patient has been followed for 5 years without signs of local recurrence or metastasis. CONCLUSION: We should be alert for atypical presentations of choroidal melanoma. Unnecessary or inadvertent surgical intervention may induce tumor growth and subsequent local spread or metastasis.

Adult↗
PubMed2004

Ocular screening in severe acute respiratory syndrome.

PURPOSE: To investigate the ocular manifestations of patients with severe acute respiratory syndrome (SARS) and to monitor the possible ocular complications arising from the treatment regimen with high-dose systemic corticosteroid drugs. DESIGN: Prospective, observational cohort case series. METHODS: Ninety eyes from 45 patients with the diagnosis of SARS during an epidemic outbreak in Hong Kong were analyzed. Relevant medical and ophthalmic histories were taken. Ophthalmic examinations, including best-corrected visual acuity, intraocular pressure, slit-lamp, and indirect ophthalmoscopy examination, were performed at baseline and at 2-month and 3-month follow-up. SETTING: Faculty practice in university hospital. RESULTS: Only two patients had mild elevated intraocular pressure at baseline and at subsequent follow-up. There was no loss of visual acuity, cataract progression, or increased cup-disk ratio. Fundus examinations were unremarkable in all patients. CONCLUSIONS: Our study did not demonstrate any ocular manifestations in patients with SARS. The treatment regimen of high-dose corticosteroid also did not show any significant ocular complications. Routine ocular screening of patients with SARS for diagnosis or for complications might not be indicated.

Adult↗
PubMed2004

Transient reduction in retinal function revealed by multifocal electroretinogram after photodynamic therapy.

PURPOSE: To evaluate the early changes in retinal function after photodynamic therapy (PDT) by multifocal electroretinogram (mfERG). DESIGN: Prospective interventional case series. METHODS: Seventeen eyes from 17 patients scheduled for standard PDT with verteporfin were prospectively recruited. Patients' diagnoses included choroidal neovascularization (CNV) secondary to age-related macular degeneration, idiopathic CNV, myopic CNV, polypoidal choroidal vasculopathy, and central serous chorioretinopathy. Serial mfERG recordings were performed before PDT, and at 4 days, 2 weeks, and 1 month after PDT. The first-order kernel N1 and P1 mfERG response from the central 0 to 7 degrees and peripheral 7 to 25 degrees were grouped and analyzed. The mean response amplitudes and peak latencies of the mfERG recordings were compared longitudinally. RESULTS: There were statistically significant reductions in the mean N1 response amplitude for the central group at 4 days (P =.007) and 2 weeks after PDT (P =.024), in the mean P1 response amplitude for both the central (P =.006) and peripheral (P =.013) groups at 4 days, and for the central group at 2 weeks after PDT (P =.017). There were also statistically significant increases in the mean P1 response latencies at 4 days (P =.004) and at 2 weeks (P =.018) after PDT for the central group and at 4 days after PDT (P =.026) for the peripheral group. At 1 month after PDT, no significant differences in the N1 and P1 mean response amplitudes and peak latencies were observed compared with pre-PDT mfERG. CONCLUSIONS: Transient impairments in retinal function for as long as 2 weeks after PDT were noticed by reduction in response amplitudes and a delay in peak latencies of mfERG. These findings may explain the common adverse event of subjective visual disturbance early after PDT with normal findings in visual acuity and ophthalmoscopy.

Adult↗
PubMed2004

Photodynamic therapy with verteporfin for symptomatic polypoidal choroidal vasculopathy: one-year results of a prospective case series.

OBJECTIVE: To determine the efficacy of photodynamic therapy (PDT) with verteporfin as a treatment for symptomatic polypoidal choroidal vasculopathy (PCV). DESIGN: Prospective consecutive, 2-centered, noncomparative interventional case series. PARTICIPANTS: Twenty-one Asian patients with 22 eyes presenting with serosanguinous maculopathy due to PCV and an initial best-corrected visual acuity (BCVA) of 20/40 or worse were recruited prospectively. All patients had angiographic leakage seen on fluorescein angiograms (FAs) and features of PCV seen with indocyanine green (ICG) angiography. METHODS: Intravenous infusion of verteporfin at a dose of 6 mg/m(2) of body surface area over 10 minutes was administered. Five minutes after the completion of infusion, a 689-nm laser was applied for 83 seconds, with a light dose of 50 J/cm(2). The laser spot size was chosen to cover the polyps and the surrounding abnormally dilated choroidal vessels shown on ICG angiography plus an extra 1000-microm margin. Photodynamic therapy retreatment was performed if leakage from the polyps was found on both repeat FAs and ICG angiography at regular 3-month follow-up intervals. MAIN OUTCOME MEASURES: The proportion of eyes with stable or improved vision at a 1-year follow-up. Secondary outcome measures included change in mean BCVA and the changes in clinical and angiographic features in FAs and ICG angiography. The total number of PDT sessions and any complications were also recorded. RESULTS: Stable or improved vision was achieved in 21 (95%) of the 22 eyes at the 1-year follow-up. Ten (45%) eyes had a moderate gain in vision (improved by > or =3 lines), whereas 1 (5%) eye suffered a moderate visual loss (decrease by > or =3 lines). The mean BCVA improved from a logarithm of the minimum angle of resolution(logMAR) of 0.73 to 0.60, an equivalent of 1.3 lines of improvement. The change in logMAR BCVA at 12 months was statistically significant (Wilcoxon signed-ranks test, P = 0.009). Complete absence of leakage in FAs and total regression of the polyps in ICG angiography were observed in 20 (91%) and 21 (95%) eyes, respectively. Severe loss of vision due to massive subretinal hemorrhage occurred in 1 eye; otherwise, there were no other serious treatment-related adverse events. CONCLUSIONS: The 1-year results of PDT in treating PCV of the macular type with serosanguinous presentations are encouraging. Further studies with longer follow-up and randomized controlled trials are warranted to assess the long-term safety and efficacy of PDT relative to observation or other treatment modalities.

Aged↗
PubMed2004

Stage of change for general health promotion action and health-related lifestyle practices in Chinese adults.

BACKGROUND: We propose general health promotion action (GHPA) to represent the general intention and actual practices aimed to promote health. The transtheoretical model (TTM) has not been applied to GHPA. The objectives of this study were to determine whether TTM can be applied to Chinese adults by measuring the subjects' stage of change for GHPA, and to study whether stage for GHPA is associated with health-related lifestyle practices. METHODS: Randomly selected Hong Kong Chinese subjects (3233) aged 18-64 were interviewed in telephone survey. RESULTS: Thirty-nine percent had not taken any health promotion actions and had no intention to do so (precontemplation). Twelve percent had taken action but had no intention to continue (at-risk for relapse). Three percent had not taken any actions and intended to do so in the next 6 months, but not in the next 1 month (contemplation). Eleven percent had not taken any actions but intended to do so in the next 1 month (preparation). Fifteen percent had been taking action for less than 6 months and intended to continue (action). Twenty-one percent had been taking action for at least 6 months and intended to continue (maintenance). Precontemplators were less likely than maintainers to be never smokers (OR = 0.62; 95% CI = 0.49-0.80), exercisers (0.097; 0.077-0.12), to eat fruit twice a day (0.53; 0.41-0.69) and remove fat when eating (0.72; 0.54-0.95), with increasing trends in the odds of reporting these practices from precontemplation to maintenance. CONCLUSIONS: Our findings have provided preliminary findings on the applicability of TTM on GHPA in Chinese adults with evidences of concurrent criterion validity.

Adult↗
PubMed2004

Intravitreal triamcinolone for diabetic macular oedema in Chinese patients: six-month prospective longitudinal pilot study.

AIM: To evaluate the safety and efficacy of intravitreal triamcinolone (IVTA) in Chinese patients with diabetic clinical significant macular oedema (CSMO). METHODS: Eighteen eyes of 17 consecutive patients with CSMO were prospectively recruited and treated with a 4 mg injection of IVTA. Best-corrected visual acuity (BCVA) on the ETDRS chart and central macular thickness (CMT) on optical coherence tomography were measured at baseline weeks 1, 2, 3, and months 1, 2, 3, 4, 5 and 6. Side-effects were monitored. RESULTS: All patients completed 6 months of follow up. The mean baseline BCVA and CMT were 1.20 +/- 0.31 logMAR units and 552 +/- 179 microm, respectively. Improvements in CMT and BCVA were observed as early as at 1 and 2 weeks, respectively (P < 0.05). Mean BCVA peaked at 2 months (0.97 +/- 0.38 logMAR units) while mean CMT was maximally reduced at 3 months (326 +/- 145 microm). Improvements in BCVA and CMT were less afterwards but still statistically significant at 6 months; the final mean BCVA and CMT were 0.99 +/- 0.36 logMAR units and 427 +/- 145 microm, respectively. A total of 5/18 (28%) eyes developed a transient increase in intraocular pressure. Cataract progression was noted in 2/12 (17%) of the phakic eyes. CONCLUSIONS: Intravitreal triamcinolone appeared generally safe and effective in Chinese patients with CSMO. Although the improvements in BCVA and CMT were transient, there were residual benefits at 6 months. Due to the transient nature of IVTA, re-treatment seems necessary but the optimal timing and dosage will require further investigations.

Aged↗
PubMed2004

Identification of KIF21A mutations as a rare cause of congenital fibrosis of the extraocular muscles type 3 (CFEOM3).

PURPOSE: Three congenital fibrosis of the extraocular muscles phenotypes (CFEOM1-3) have been identified. Each represents a specific form of paralytic strabismus characterized by congenital restrictive ophthalmoplegia, often with accompanying ptosis. It has been demonstrated that CFEOM1 results from mutations in KIF21A and CFEOM2 from mutations in PHOX2A. This study was conducted to determine the incidence of KIF21A and PHOX2A mutations among individuals with the third CFEOM phenotype, CFEOM3. METHODS: All pedigrees and sporadic individuals with CFEOM3 in the authors' database were identified, whether the pedigrees were linked or consistent with linkage to the FEOM1, FEOM2, and/or FEOM3 loci was determined, and the appropriate pedigrees and the sporadic individuals were screened for mutations in KIF21A and PHOX2A. RESULTS: Twelve CFEOM3 pedigrees and 10 CFEOM3 sporadic individuals were identified in the database. The structures of eight of the pedigrees permitted the generation of meaningful linkage data. KIF21A was screened in 17 probands, and mutations were identified in two CFEOM3 pedigrees. One pedigree harbored a novel mutation (2841G-->A, M947I) and one harbored the most common and recurrent of the CFEOM1 mutations identified previously (2860C-->T, R954W). None of CFEOM3 pedigrees or sporadic individuals harbored mutations in PHOX2A. CONCLUSIONS: The results demonstrate that KIF21A mutations are a rare cause of CFEOM3 and that KIF21A mutations can be nonpenetrant. Although KIF21A is the first gene to be associated with CFEOM3, the results imply that mutations in the unidentified FEOM3 gene are the more common cause of this phenotype.

DNA Mutational Analysis↗
PubMed2003

Heterozygous mutations of the kinesin KIF21A in congenital fibrosis of the extraocular muscles type 1 (CFEOM1).

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1; OMIM #135700) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. We show that individuals with CFEOM1 harbor heterozygous missense mutations in a kinesin motor protein encoded by KIF21A. We identified six different mutations in 44 of 45 probands. The primary mutational hotspots are in the stalk domain, highlighting an important new role for KIF21A and its stalk in the formation of the oculomotor axis.

Amino Acid Sequence↗