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Biomedical subjects

Wai-Man Chan

Publications and source records attributed to Wai-Man Chan.

At least 55 records · Page 3Linked to original sources
PubMed2005

Comparison of macular and peripapillary measurements for the detection of glaucoma: an optical coherence tomography study.

OBJECTIVE: To evaluate macular nerve fiber layer (NFL) thickness in glaucomatous damage by optical coherence tomography (OCT) and to compare its discriminating power for glaucoma and glaucoma suspects with that of total macular thickness and peripapillary NFL thickness. DESIGN: Cross-sectional, case-control, comparative study. PARTICIPANTS: A total of 133 eyes from 133 subjects including 46 normal eyes, 48 glaucoma-suspect eyes, and 39 glaucoma eyes were enrolled. METHODS: Macular NFL thickness, total macular thickness, and peripapillary NFL thickness were measured by Stratus OCT in each diagnostic group. MAIN OUTCOME MEASURES: The patterns and measurements of macular NFL, total macular, and peripapillary NFL thickness in total mean, 4 quadrants, and 12 clock hours. The discriminating power of each parameter for detection of glaucoma suspects and glaucoma was evaluated by areas under the receiver operating characteristic curve (AROC). Correspondence with visual field function was studied by linear regression analysis. RESULTS: The macular NFL profile exhibited a double-hump pattern with peaks over superonasal and inferonasal sectors. A significant difference in macular NFL thickness between normal and glaucoma-suspect groups was found at the 6-o'clock position, whereas a difference was found in all except the temporal clock hours between normal and glaucoma subjects. No significant difference in AROCs for detection of glaucoma suspects or glaucoma was found when macular NFL thickness and total macular thickness measurements were compared. However, mean macular NFL thickness demonstrated a stronger correlation with visual function than mean macular thickness (r = 0.39/R2 = 0.15 vs. r = 0.23/R2 = 0.05, P =0.042). Among all the findings, inferior peripapillary NFL thickness had the best performance in discriminating glaucoma (AROC, 0.91) and glaucoma suspects (AROC, 0.67). It also had the strongest correlation with visual function (r = 0.60/R2 = 0.36, P<0.001). CONCLUSIONS: Macular NFL thickness was significantly reduced in glaucoma. It had a similar discriminating power for glaucoma detection but a stronger correlation with visual function than total macular thickness. Peripapillary NFL thickness, however, outperformed both total macular and macular NFL thickness in terms of glaucoma detection and visual function correlation. Peripapillary NFL thickness, as a total measurement of both macular and peripheral NFL, is still the best surrogate marker in glaucoma assessment.

Case-Control Studies↗
PubMed2005

Visualization of anterior chamber angle dynamics using optical coherence tomography.

PURPOSE: To describe the technology of optical coherence tomography (OCT) in imaging the anterior chamber angles and its impact on understanding the pathophysiology of angle-closure glaucoma (ACG). DESIGN: Observational case series. PARTICIPANTS: Three subjects with, respectively, impending angle-closure attack, plateau iris syndrome, and phacomorphic glaucoma were recruited. METHODS: The anterior chamber angle in each patient was imaged with a commercially available OCT unit. The angle configurations were assessed and compared before and after laser peripheral iridotomy (LPI) and argon laser peripheral iridoplasty (ALPI). MAIN OUTCOME MEASURES: Visualization of the changes in the anterior chamber angle configurations and normalization of the intraocular pressure (IOP). RESULTS: A patient with impending angle-closure attack precipitated by a topical mydriatic agent was treated with LPI. Optical coherence tomography imaging of the anterior chamber angles was performed before and after the laser procedure. Conversion of anterior iris bowing and angle crowding to iris straightening and angle opening after LPI was demonstrated. Intraocular pressure became normalized with the change in angle configuration. The second patient presented with symptoms of intermittent angle-closure attacks and was initially diagnosed with primary ACG. Despite successful LPI, the angles remained occludable, and the IOP continued to be elevated. Optical coherence tomography was used to review the anterior chamber angle configuration and demonstrated a typical pattern compatible with the diagnosis of plateau iris syndrome. Subsequent ALPI converted the plateau configuration to open angle, with normalization of IOP and disappearance of symptoms. The third patient presented with an acute angle-closure attack and was diagnosed with phacomorphic glaucoma. Argon laser peripheral iridoplasty was performed successfully to open the angle, as evident by the OCT images, and the IOP was brought under control, together with relief of symptoms. CONCLUSIONS: The commercially available OCT unit can be practically employed for anterior chamber angle imaging. The different patterns of angle configurations are correlated with the underlying pathophysiology in different forms of ACG.

Aged↗
PubMed2005

Prevalence and characteristics of peripheral retinal degeneration in Chinese adults with high myopia: a cross-sectional prevalence survey.

PURPOSE: The purpose of this study was to study the prevalence of peripheral retinal findings in adult Chinese patients with high myopia (refraction < or = -6.00 D) and to investigate the correlation between the retinal lesions and the severity of myopia or axial length. METHODS: A cross-sectional prevalence survey screening was conducted in high ethnic Chinese myopes with refractions equal to or less than -6.00 D. The examinations included cycloplegic refraction, A and B scan ultrasonography, and retinal examinations by indirect ophthalmoscopy with scleral indentation and Goldmann three-mirror contact lens examination. RESULTS: Two hundred thirteen eyes in 213 patients with a mean refraction of -10.10 +/- 4.23 D (range = -6.00 to -27.00 D) were examined. The mean axial length was 26.69 +/- 1.68 mm (range = 25.18-33.62 mm) and the mean age was 33.5 +/- 10.6 years (range = 18-73 years). The most common peripheral retinal finding was pigmentary degeneration (51.2%), followed by lattice degeneration in 12.2% and retinal holes in 7.5% of eyes. A positive correlation was noted between axial length and the lesions of pigmentary degeneration and pavingstone degeneration. The prevalence of retinal holes was 6.4% and 30.0% in eyes with axial length of < 30 mm and > or = 30 mm, respectively (chi-squared test, p = 0.006). CONCLUSION: A high prevalence of peripheral retinal degenerations was found in adult Chinese high myopes. The presence of retinal holes was positively correlated with very high myopia of an axial length of > or = 30 mm.

Adult↗
PubMed2005

Longitudinal findings of acute macular neuroretinopathy with multifocal electroretinogram and optical coherence tomography.

A 34-year-old woman, with preceding flu-like febrile illness, developed acute macular neuroretinopathy in her left eye with typical reddish brown macular lesions and a dense paracentral scotoma. Her condition was evaluated with multifocal electroretinogram and optical coherence tomography in her acute and recovery phases. The findings assist ophthalmologists striving for better understanding and diagnosis of acute macular neuroretinopathy.

Acute Disease↗
PubMed2005

Extensive submacular haemorrhage in polypoidal choroidal vasculopathy managed by sequential gas displacement and photodynamic therapy: a pilot study of one-year follow up.

BACKGROUND: Polypoidal choroidal vasculopathy (PCV) with peculiar vascular lesions presents frequently as recurrent submacular haemorrhage. The best treatment is still not certain. It is the authors' objective to evaluate the 1-year safety and efficacy of photodynamic therapy (PDT) using verteporfin for persistent macular PCV after pneumatic displacement of the massive submacular haemorrhage with intravitreal perfluoropropane (C(3)F(8)). METHODS: A prospective, non-comparative, interventional case series on patients with extensive and thick submacular haemorrhage secondary to PCV, which was displaced pneumatically with intravitreal pure 0.4 ml C(3)F(8). Fluorescein angiography and indocyanine green angiography were repeated 1-2 weeks later to delineate any persistent active leaking polypoidal lesions, which were then treated with PDT. Retreatment might be considered in each follow up at every 3 months. RESULTS: Six eyes of six patients with the mean age of 53.6 years had been recruited and completed 1-year follow up. The mean baseline Snellen equivalent best-corrected visual acuity (BCVA) was 6/92 and the mean final BCVA at 1 year was 6/17. The mean improvement in logMAR BCVA after the sequential treatments was seven lines (range +3 to +19 lines) (Wilcoxon signed-ranks test, P = 0.03). All patients had at least moderate visual gains. No patient suffered serious complications from PDT. CONCLUSIONS: This first report on combined treatment with intravitreal gas injection and sequential PDT on PCV seems to be a well-tolerated option. Further comparative studies with larger sample size and longer follow up are warranted.

Choroid↗
PubMed2005

Bilateral exudative retinal detachments as the presenting features of idiopathic orbital inflammation.

Idiopathic orbital inflammation, also known as orbital pseudotumour, is a term describing a spectrum of idiopathic, non-neoplastic, non-infectious, space-occupying orbital lesion without identifiable local or systemic cause. This disease occurs mainly in young adults and typically presents with acute proptosis, chemosis and limited extraocular movement. Herein an unusual case of idiopathic orbital inflammation presenting with bilateral exudative retinal detachment in a 9-year-old girl is described. It demonstrates that prompt diagnosis and corticosteroid treatment can yield good clinical response and significant visual recovery.

Child↗
PubMed2005

Analysis of retinal nerve fiber layer and optic nerve head in glaucoma with different reference plane offsets, using optical coherence tomography.

PURPOSE: To evaluate the performance of retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) parameters analyzed with different offsets of reference plane in detecting early glaucomatous changes and in correlation with visual function using optical coherence tomography (OCT). METHODS: This was a cross-sectional study consisting of 41 normal subjects and 30 with early and 40 with advanced glaucoma. RNFL thickness and ONH parameters were measured with reference planes positioned at 95, 150, and 205 microm above the level of retinal pigment epithelium (RPE). Discriminating power for early glaucoma detection and correlation with visual field MD for each parameter at different levels of reference plane were compared by using the analyses of area under the receiver operating characteristic curves (AUCs) and linear regression, respectively. RESULTS: All ONH measurements were significantly different between normal and glaucoma groups, irrespective of the level of reference plane. In normal eyes, changing the reference plane position resulted in significant differences in ONH measurements. Among all the parameters examined, integrated rim volume and RNFL thickness measured at 150 microm above the RPE showed the largest AUC (0.966) for early glaucoma detection, and the strongest correlation with visual function (r = 0.793), respectively. CONCLUSIONS: OCT analysis of the ONH and RNFL is useful for early glaucoma detection. Among the three reference planes examined in this study, measurements analyzed at 150 microm above the RPE demonstrated the best performance for glaucoma detection and correlation with visual function. Compared with ONH measurements, RNFL thickness may be a better indicator, reflecting retinal ganglion cell function and monitoring disease progression.

Cross-Sectional Studies↗
PubMed2005

[Recent progress in molecular genetics and gene therapy for retinitis pigmentosa].

Retinitis pigmentosa (RP) is a common genetic eye disease affecting about 1 in 3500 people worldwide with pan-ethnic occurrence. So far there is no effective treatment for RP. This paper gives an overview on recent advances in molecular genetics of RP with emphasis on the important gene mutations for diagnosis and prognosis, and a review on gene therapy of RP.

Genetic Therapy↗