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Biomedical subjects

A K Kwok

Publications and source records attributed to A K Kwok.

At least 19 recordsLinked to original sources
PubMed2001

RP1 in Chinese: Eight novel variants and evidence that truncation of the extreme C-terminal does not cause retinitis pigmentosa.

Heterozygous truncating mutations in the RP1 gene cause approximately 7% of autosomal dominant retinitis pigmentosa (RP) cases. To examine the role of RP1 mutations in RP, we screened 101 unrelated Chinese RP patients (unselected for mode of inheritance) and 190 elderly normal control subjects for sequence changes in the coding exons for the 2156 amino acid RP1 protein. One patient had a mutation, thus RP1 mutations cause about 0.0% to 5.4% (95% confidence interval) of all RP among Chinese. The mutation was R677X, the most common found in Americans. Five other known sequence changes were found. In addition, nine novel sequence alterations were identified: 746G>A (R249H), 1437G>T (M479I), 2116G>C (G706R), 3024G>A (Q1008Q), 3188G>A (Q1063R), 5797C>T (R1933X), 6423A>G (I2141M), and the variants 6542C>T and 6676T>A, both in the 3' untranslated region. One control subject and three members of a non-RP family were heterozygous for R1933X, which is therefore likely to be a non-disease-causing variant. The most C-terminal truncation previously reported was due to Tyr1053 (1-bp del) and occurred in RP patients. Thus the presence of a normal level of at least part of RP1 between amino acids 1052 and 1933 appears necessary to prevent RP. Hum Mutat 17:436, 2001.

3' Untranslated Regions↗
PubMed2001

Surgical technique for transcleral-fixation of a dislocated posterior chamber intraocular lens.

PURPOSE: To report a cornea-pars plana through-and-through technique for the repositioning and transcleral suture fixation of a dislocated posterior chamber intraocular lens. DESIGN: Interventional case series. METHODS: For transscleral suture fixation of a dislocated posterior chamber intraocular lens, one needle of a double-arm 10-0 Prolene needle is passed through the paracentesis site then underneath the intraocular lens haptic, and through the intended scleral outlet on the opposite side. The other needle of the Prolene suture is also passed through the same paracentesis, above the same haptic, and through the intended scleral outlet on the opposite side. The haptic is now well supported, and the knot is tied. A similar procedure is performed for the second haptic if necessary. RESULTS: Three eyes (three patients) were operated on using this technique with good visual and anatomic outcome. CONCLUSION: The described technique is simple, safe, allows early visual rehabilitation, and can be accomplished without an assistant.

Female↗
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

Indocyanine green staining and removal of internal limiting membrane in macular hole surgery: histology and outcome.

PURPOSE: To report the surgical technique, outcome, and histologic findings involving indocyanine green staining and removal of internal limiting membrane in primary macular hole surgery. METHODS: Prospectively, consecutive patients with idiopathic macular hole or myopic macular hole with retinal detachment were recruited. After pars plana vitrectomy and epiretinal membrane removal, the internal limiting membrane was stained and removed. The specimens were stained using hematoxylin and eosin and periodic acid-Schiff. Immunohistochemical staining was also performed for glial fibrillary acidic protein, vimentin, type I and type IV collagen, and actin. RESULTS: Among 10 patients (10 eyes) in the study, nine eyes had stage 3 or 4 macular hole. Four of them had chronic macular hole. The tenth patient had retinal detachment resulting from a myopic macular hole. Postoperatively, all cases had closure of macular hole without an elevated edge and the retina was attached. Seven patients had improvement of 2 or more Snellen lines, whereas visual acuity remained the same for the other three patients. In six eyes in which complete histologic examinations were feasible, internal limiting membrane was confirmed and two eyes also had a small amount of epiretinal membrane. Myofibrocytes in internal limiting membrane, either scattered or as a single layer, were found in three cases. CONCLUSIONS: Removal of indocyanine green--stained internal limiting membrane around idiopathic macular hole or myopic macular hole with retinal detachment is confirmed with histology and may contribute to macular hole closure and retinal reattachment.

Actins↗
PubMed2001

Molecular diagnostics for retinitis pigmentosa.

BACKGROUND: At least 1 million people worldwide have retinitis pigmentosa (RP), making it relatively common among the inherited forms of blindness. Mutations in many genes may cause RP. The most common known mutation, Pro347Leu in rhodopsin, is found in no more than about 1% of unrelated patients, implying the impracticality of a diagnostic test which would screen only for a few, common mutation sites. CONCLUSIONS: Ongoing discovery and study of RP genes makes it feasible to consider a molecular diagnostic test which would screen coding regions of all known RP genes by a mutation detection method such as conformation-sensitive gel electrophoresis followed by sequencing. The parallel development of RP genetic knowledge and treatments such as gene therapy will make such tests both possible and necessary.

China↗
PubMed2001

Efficacy of lignocaine gel for outpatient laser treatment in inflamed eyes.

PURPOSE: To evaluate the efficacy and safety of topical 2% lignocaine gel in providing analgesia during outpatient transpupillary or trans-scleral laser treatment of inflamed eyes. METHODS: A prospective study was carried out of consecutive eligible eyes undergoing laser treatment using 2% lignocaine gel as a topical anaesthetic and a coupling medium. At the conclusion of each procedure, patients were asked to grade a pain score (0 = no discomfort, 1 = mild discomfort, 2 = mild pain, 3 = moderate pain, 4 = severe pain). RESULTS: Twenty eyes in 19 patients received laser treatment. No pain was reported in 95% of cases treated (no discomfort in 75%, mild discomfort in 20%) and only mild pain in 5% (one patient). No adverse reactions were encountered in any of the patients. There were no complications associated with the procedures. CONCLUSIONS: Lignocaine 2% gel is safe and effective for outpatient transpupillary and trans-scleral laser treatment in inflamed eyes, providing adequate analgesia and serving as a coupling medium at the same time.

Administration, Topical↗
PubMed2001

Rhodopsin mutations in Chinese patients with retinitis pigmentosa.

AIM: To determine the pattern of rhodopsin mutations in Chinese retinitis pigmentosa (RP) patients. METHODS: The rhodopsin gene was examined in 101 RP patients and 190 controls from Hong Kong. RESULTS: Three coding changes were identified: Pro347Leu, Ala299Ser, and 5211delC. Each protein sequence alteration was found in one patient. Ala299Ser also existed in two controls. CONCLUSION: The C-terminal nonsense mutation may cause mis-sorting of rhodopsin protein. The finding of controls with Ala299Ser suggests this is only the third missense alteration reported that does not cause RP. The expected frequency of rhodopsin mutations in RP is <7% (2/101=2.0%, 95% confidence interval: 0.2%-7.0%).

Adult↗
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↗