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Biomedical subjects

Barry Y M Yeung

Publications and source records attributed to Barry Y M Yeung.

5 recordsLinked to original sources
PubMed2006

Comparison between central corneal thickness measurements by ultrasound pachymetry and optical coherence tomography.

PURPOSE: Measurement of central corneal thickness (CCT) plays an important role in both diagnostic and therapeutic assessment of ocular diseases. Although ultrasound pachymetry (U-PACH) is regarded as the golden standard for measurement of CCT, optical coherence tomography (OCT) may offer advantages as it can locate the central cornea with precision with no corneal touch. Nevertheless, the agreement of OCT with U-PACH has not yet been gauged by Bland-Altman analysis. This study compares CCT measurement by OCT with that by U-PACH. METHODS: Healthy subjects without ocular abnormality (except refractive errors less than or equal to -6.0 D), contact lens wear or ocular surgery were recruited. CCT was measured in one eye of normal subjects using OCT and U-PACH. Results were compared using correlation and Bland-Altman plots. RESULTS: Fifty subjects were recruited. Mean +/- SD CCT measured by OCT was 565 +/- 33 microm. This was highly correlated (Pearson's coefficient = 0.934) with the mean thickness measured by U-PACH (543 +/- 33 microm). The coefficients of variation were good and comparable at 7.9% for U-PACH and 3.5% for OCT. Compared with U-PACH, OCT consistently overestimated the CCT by a mean of 23 microm as shown on Bland-Altman plot. CONCLUSION: CCT measured by OCT and U-PACH is highly correlated. With appropriate adjustment factor, OCT agrees well with U-PACH and is a reliable alternative for CCT measurement.

Adult↗
PubMed2005

Prevalence and mechanism of appositional angle closure in acute primary angle closure after iridotomy.

PURPOSE: A prospective observational case series to assess the prevalence of appositional angle closure in darkness among iridotomized Chinese eyes after acute primary angle closure (APAC) with the use of both clinical methods and ultrasound biomicroscopy. METHODS: Sixteen Chinese patients who had history of APAC and subsequent successful treatment with laser peripheral iridotomy were examined. Fourteen additional control subjects were studied. Gonioscopy and ultrasound biomicroscopic examination were performed in the dark. Gonioscopic appearance of the angle was assessed, and quantitative measurements of the angle from the ultrasound biomicroscopic images were taken. RESULTS: Of the APAC eyes 55.6% had appositionally closed angle clinically and in 38.9% only Schwalbe's line was visible on gonioscopy. Ultrasound biomicroscopy confirmed structurally different anterior segments between eyes with APAC and the control eyes. In particular, the trabecular-ciliary-process distances were markedly different between the two groups. CONCLUSION: This study documented a high prevalence of appositional closure in iridotomized eyes after APAC in Chinese patients. The anteriorly positioned ciliary body, as documented in these cases by ultrasound biomicroscopy, is the likely mechanism of the angle crowding in this patient population.

Acute Disease↗
PubMed2004

Descemet membrane detachment caused by hydrogen peroxide injury.

OBJECTIVE: To describe a patient who developed a Descemet membrane detachment after hydrogen peroxide injury with successful reattachment by intracameral injection of sulfur hexafluoride gas. METHODS: Case report. RESULTS: The right eye of a 40-year-old man was exposed to 35% hydrogen peroxide. This resulted in a central corneal epithelial defect, corneal edema, a localized detachment of Descemet membrane, and a gas bubble between the posterior corneal stroma and Descemet membrane. The Descemet membrane detachment persisted after reabsorption of the gas bubble. Successful reattachment of Descemet membrane was achieved with injection of 0.15 mL of 20% sulfur hexafluoride gas into the anterior chamber. CONCLUSION: Hydrogen peroxide ocular injury may cause Descemet membrane detachment, and successful reattachment may be achieved with intracameral injection of 20% sulfur hexafluoride gas.

Adult↗
PubMed2003

Fornix-based trabeculectomy using the 'anchoring' corneal suture technique.

AIM: To assess the safety and efficacy of fornix-based tra-beculectomy with the 'anchoring' corneal suture technique in Chinese patients. METHODS: A retrospective non-comparative case series of 66 eyes of 63 Chinese patients who underwent fornix-based trabeculectomy combined with intraoperative mitomycin C (MMC) 0.4 mg/mL for 2-5 min were studied. Conjunctival wound closure of all eyes was with the anchoring corneal suture technique using a 9-0 nylon suture to prevent leakage at the corneolimbal interface. The success rate, with or without anti-glaucoma medication, the complication rate and the longevity of the drainage blebs were analyzed. RESULTS: At a mean follow-up period of 447.36 +/- 337.98 days, the mean intraocular pressure decreased from 26.83 +/- 7.90 mmHg to 17.74 +/- 8.74 mmHg (P < 0.001). The mean glaucoma medication decreased from 2.95 +/- 0.98 preoperatively to 1.23 +/- 1.41 postoperatively (P < 0.001). Thirty-one eyes (47.0%) required no anti-glaucoma medication postoperatively. Twenty eyes (30.3%) had qualified success postoperatively. Eight eyes (12.1%) had early wound leakage that resolved with conservative treatment. Three eyes (4.5%) required surgical repair. One eye (1.5%) had hypotonous maculopathy. No other major complications were encountered. CONCLUSION: Fornix-based trabeculectomy with adjunctive mitomycin C employing the anchoring corneal suture technique appears to be both safe and effective in Chinese patients.

Adult↗