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Biomedical subjects

Derek G Chan

Publications and source records attributed to Derek G Chan.

13 recordsLinked to original sources
PubMed2005

Videoreflective dacryomeniscometry in normal adults and in patients with functional or primary acquired nasolacrimal duct obstruction.

PURPOSE: Videoreflective dacryomeniscometry (VRD) for evaluation of marginal tear film has not been performed in patients with watery eye or in a controlled study. We used VRD to evaluate the height of the central marginal lower lid tear film in normal adults and compared it with two watery-eye groups and a postoperative dacryocystorhinostomy (DCR) group. DESIGN: Case-controlled interventional case series. METHODS: We evaluated with VRD 20 subjects with normal lacrimal drainage function, 21 patients with primary acquired nasolacrimal duct obstruction (PANDO), 28 patients with functional nasolacrimal duct obstruction (FNLDO), and a postoperative group of 14 patients derived from the previous two pathologic groups. Comparison between the four groups was performed to determine statistically significant differences between tear film height. RESULTS: PANDO and FNLDO groups were shown to have significantly greater median tear meniscus heights ([TMH] PANDO: 620 microm, interquartile range [IQR] 453 microm; FNLDO: 731 microm, IQR 529 microm) than normal subjects (296 microm, IQR 214 microm; P < .001) and postoperative PANDO patients (265 microm, IQR 159 microm). There was no significant difference in TMH between PANDO and FNLDO groups preoperatively (P = .275). There was a reduction in median TMH postoperatively of 355 microm (P = .008) in PANDO and 360 microm (P = .068) in FNLDO. CONCLUSIONS: PANDO and FNLDO patients have similar preoperative TMH. In both these groups, TMH is significantly greater than in normal control subjects. Lacrimal drainage surgery substantially reduces TMH as measured using VRD in PANDO.

Aged↗
PubMed2005

Intraoperative management of iris prolapse using iris hooks.

Iris prolapse has become an unusual and generally benign event in routine cataract surgery using endocapsular phacoemulsification techniques. We operated on the second eye of a patient with hyperopia whose first eye surgery in our care had been uneventful. In the second eye, as soon as the phaco incision was made and hydrodissection begun through the primary incision, the iris repeatedly prolapsed through the incision. This was managed definitively by applying iris hooks, 1 at each side of the primary incision, to the pupillary border so the prolapsing iris was held peripherally in the anterior chamber and under modest tension.

Aged↗
PubMed2003

Contact versus immersion biometry of axial length before cataract surgery.

PURPOSE: To compare the repeatability and agreement of contact and immersion ultrasound (US) biometry of axial length. SETTING: Prince of Wales Hospital, Sydney, Australia. METHODS: This prospective stratified randomized study comprised 36 patients with a preoperative refractive error less than 4.00 diopters (D) sphere or 2.00 D cylinder who were recruited before cataract surgery. Each of 3 operators measured both eyes of 12 patients by contact and immersion US techniques. A repeat measurement by both techniques was performed by the same operator in 6 cases and by a different operator in the other 6. Repeat and operator effects were examined. RESULTS: The mean and standard deviation of the measurement sets were compared, and the differences between repeat measures were calculated. Axial length measurement was longer with the contact method than with immersion by 0.03 mm (P =.04). The repeatability of the 2 techniques was similar. CONCLUSIONS: When the measurement set was repeated, the precision of contact US biometry was comparable to that of immersion, with no clinically significant difference in mean axial length measurements.

Adult↗