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Biomedical subjects

J S Ng

Publications and source records attributed to J S Ng.

At least 19 recordsLinked to original sources
PubMed2001

Observation of plasma focusing of a 28.5 GeV positron beam.

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0+/-0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations.

Journal Article↗
PubMed2001

Uterine papillary serous carcinoma presenting as distant lymph node metastasis.

BACKGROUND: Uterine papillary serous carcinomas are highly aggressive malignancies that often present with high-stage disease. We report two cases that presented initially as distant metastatic disease. One case was found incidentally at the time of axillary dissection for breast cancer and the second case in the workup of a neck mass. CASES: Clinicopathologic review of the patient material including review of routine H&E pathology and immunohistochemical studies of the patients tumors was performed. Both cases showed high-grade papillary carcinomas with psammoma bodies metastatic to lymph nodes in the axilla or neck. Sampling of the endometrium in these patients confirmed primary uterine papillary serous carcinoma. Patients were treated with adjuvant chemotherapy. CONCLUSIONS: Metastatic uterine papillary serous carcinoma presenting initially in distant sites is an unusual manisfestation of this highly aggressive tumor. This tumor should be considered in the differential diagnosis when patients present with metastatic high-grade papillary serous carcinomas and the primary site is unknown.

Aged↗
PubMed2001

A prospective study on ocular hypertensive and antiinflammatory response to different dosages of fluorometholone in children.

OBJECTIVE: To investigate the ocular hypertensive and antiinflammatory response to different dosages of fluorometholone (FML). DESIGN: Prospective clinical trial with randomization of fellow eyes to different postoperative treatment. PARTICIPANTS: Thirty-one consecutive children undergoing bilateral symmetrical strabismus operation. INTERVENTION: Among 31 children who received bilateral squint operations, one eye was randomized to receive topical FML six times daily (group 1), whereas the other eye received topical FML three times daily (group 2), both for 4 weeks. Intraocular pressure (IOP) and antiinflammatory response were measured serially in the postoperative period for 8 weeks. MAIN OUTCOME MEASURES: Intraocular pressure was measured on the day before surgery and on postoperative days 1, 3, 6, 13, 20, 27, 41, and 55. The antiinflammatory response was also assessed subjectively and objectively at days 6, 13, 20, and 27 after the operations. Peak IOP, net increase in IOP, and antiinflammatory responses in the two study groups were analyzed. RESULTS: Thirty-one children, age 3 to 9 years, (mean +/- standard deviation [SD], 5.52 +/- 1.81) participated in the study. Intraocular pressure increased significantly in both groups compared with the preoperative values (P < 0.001). The peak IOP ranged from 12.00 to 31.00 mmHg and 12.30 to 25.00 mmHg in groups 1 and 2, respectively. The mean peak IOP (19.00 +/- 5.06 mmHg vs. 17.13 +/- 3.32 mmHg) was significantly higher in group 1 (P < 0.001). The net increase in IOP was similar (mean +/- SD, 4.37 +/- 4.79 vs. 2.57 +/- 3.32 mmHg; P = 0.005). Ranges of the net IOP increase were -1.00 to 16.00 mmHg and -2.50 to 10.30 mmHg in groups 1 and 2, respectively. Children in group 1 reached the peak IOP earlier than those in group 2 (median, 6 vs. 13 days; P = 0.033). However, there was no significant difference in antiinflammatory response between the two groups. CONCLUSIONS: Ocular hypertension occurs in a dose-dependent manner in children treated with FML. Children in group 1 had a quicker onset and more severe ocular hypertensive response than those in group 2. It would be desirable to monitor the IOP regularly when FML is used with a high frequency and for a long duration in children.

Administration, Topical↗
PubMed2001

Cystoid macular edema after pediatric intraocular lens implantation: fluorescein angioscopy results and literature review.

PURPOSE: To evaluate the occurrence of cystoid macular edema (CME) after lens extraction, anterior vitrectomy, and intraocular lens implantation (IOL) in children using angioscopy after administration of oral fluorescein. SETTING: Centers in Tamil Nadu, India, and Hong Kong, China. METHODS: This study comprised 18 children (28 eyes) who had cataract extraction, posterior capsulorhexis, anterior vitrectomy, and in-the-bag IOL implantation. The presence of CME was evaluated 1 week and 4 to 6 weeks after surgery using fluorescein angioscopy. RESULTS: Anterior chamber fibrin occurred in 4 eyes (14.3%). Fluorescein angioscopy was performed 1 week after surgery in all eyes and after 1 month in 25 eyes (89.3%). No eye demonstrated the presence of CME on fluorescein angioscopy. CONCLUSIONS: Cystoid macular edema did not occur in the early period after pediatric cataract surgery using current surgical techniques. Longer follow-up is required to ascertain the incidence of CME in the late postoperative period.

Capsulorhexis↗
PubMed2001

Ocular complications of paediatric patients with nephrotic syndrome.

PURPOSE: To investigate ocular complications arising from nephrotic syndrome and/or its treatments in children. METHODS: A cross-sectional study was conducted in a teaching hospital. A total of 31 paediatric patients with nephrotic syndrome were studied. Comprehensive ophthalmic assessments on best-corrected visual acuity, intraocular pressure, slit-lamp and fundus examination were taken. Information regarding histological diagnosis of nephrotic syndrome and its treatment regimen in each patient was reviewed and analysed. RESULTS: Bilateral posterior subcapsular cataracts were detected in three of 29 patients (10.3%) who received steroid therapy. Two had normal vision while one had visual acuity reduced to 6/15 in both eyes. The age of onset of the nephrotic syndrome in these three patients was 2 years, which was significantly younger than those without cataract (5.4 +/- 3.2 years, P < 0.001). Three patients (9.7%) had isolated asymptomatic fundal findings of tortuous and dilated retinal vessels. Hypertensive retinopathy was found in one patient (3.2%). No steroid-induced glaucoma, uveitis, ocular infection, or other eye complications related to the use of steroids or other immunosuppressive agents were noted. CONCLUSIONS: Children who have nephrotic syndrome often require prolonged, intermittent high dose of systemic corticosteroid therapy. Paediatricians should be aware of the potential risk of developing steroid-related complications, especially posterior subcapsular cataract. It appears to have a higher risk when steroid therapy is used in very young patients. Early detection would help to prevent amblyopia development, particularly in the group of immature eyes.

Adolescent↗
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↗
PubMed2000

Scleral fixation of a capsular tension ring for severe ectopia lentis.

A 4-year-old boy with bilateral idiopathic and progressive ectopia lentis had phacoaspiration of the lens and capsular tension ring (CTR) insertion in his left eye. Postoperatively, lens capsule centration remained poor. Single-point scleral fixation of the CTR was performed and centration of the lens capsule achieved. In-the-capsule intraocular lens (IOL) implantation was tried, but excessive IOL manipulation sliced open the capsule at the equator. Anterior vitrectomy and scleral IOL fixation were required. A similar approach was adopted in the right eye with meticulous attention given to gentle maneuvers. The operation was uneventful, with good IOL centration. Three and 11 months after surgery in the right and left eye, respectively, best corrected visual acuity was 20/50 in both eyes. Scleral fixation of the CTR, accompanied by gentle IOL manipulation, is an option to improve IOL centration in patients with severe zonular deficiency.

Child, Preschool↗
PubMed1999

Isolated pedunculated congenital corneal dermoid.

PURPOSE: To investigate a case of isolated pedunculated congenital corneal dermoid. METHODS: Case report. RESULTS: In a 14-day-old infant, the pedunculated portion of the dermoid was removed and confirmed by histopathologic examination. No surgical complication or recurrence was encountered, and the patient is waiting for a rotational autokeratoplasty. CONCLUSIONS: Prompt treatment of such an unusual tumor is important to allow for visual rehabilitation and development.

Corneal Diseases↗
PubMed1999

Ocular complications of pediatric bone marrow transplantation.

OBJECTIVE: To investigate the ocular complications in pediatric bone marrow transplantation (BMT) patients. DESIGN: Cross-sectional study. PARTICIPANTS: A total of 29 pediatric BMT patients were studied. TESTING: Comprehensive ophthalmic check-up, including best-corrected visual acuity, intraocular pressure (IOP), Schirmer's test, tear breakup time, and slit-lamp and fundus examinations, was performed. MAIN OUTCOME MEASURES: Tear film instability and its related complications, IOP, cataract, and fundus lesions were measured. RESULTS: The mean age of patients was 9.1 years (range, 1.5-15 years). The mean post-BMT duration was 20.2 months (range, 3-54 months). Fifteen patients (51.7%) had tear abnormalities. Subconjunctival fibrosis was detected in two patients (6.9%). Dry and scaly skin of the eyelids was seen in one patient (3.4%). Lens opacities were found in 2 (33.3%) of 6 irradiated patients and 2 (8.7%) of 23 nonirradiated patients. Two patients (6.9%) had fundus changes, one with unilateral epiretinal membrane and the other with bilateral multiple discrete chorioretinal hypopigmented lesions in the middle to peripheral part of the retina. The overall complication rates for the anterior and posterior segments were 75.8% and 6.9%, respectively. CONCLUSION: Ocular manifestations of BMT in children are not uncommon. The most common anterior segment problem is tear dysfunction. Posterior segment complications are less common but do exist. High rate of cataract formation is reported, and this probably is the most important long-term "amblyogenic" problem in these immature eyes. Awareness and management of these problems with routine eye examination and early intervention are recommended.

Adolescent↗
PubMed1999

Use of enzyme penicillin acylase in selective amidation/amide hydrolysis to resolve ethyl 3-amino-4-pentynoate isomers.

The beta-amino acid, (S)-ethyl-3-amino-4-pentynoate, is a chiral synthon used in the synthesis of xemilofiban hydrochloride, an anti-platelet agent. A biocatalytic approach was developed to resolve (R)- and (S)-enantiomers of ethyl 3-amino-4-pentynoate in enantiomerically pure form employing the enzyme Penicillin acylase. In the acylation, phenylacetic acid was used as an acylating agent. We have shown that both the acylation and deacylation can be employed and that the activity of the enzyme Penicillin acylase can be controlled by maintaining an appropriate pH of the reaction medium.

Acylation↗
PubMed1999

Primary orbital Ewing's sarcoma: report of a case and review of the literature.

Primary orbital Ewing's sarcoma is a very rare condition. Since the first case was reported in 1950, only 7 other cases have been reported in the English literature. Herein we describe the ninth, the only bilateral and the youngest case of primary orbital Ewing's sarcoma occurring in a 2-year-old boy, who presented to us with bilateral painless proptosis. Tissue biopsy of the tumour was obtained through the nasal sinus. Immunohistological studies of the biopsy tissue confirmed the diagnosis of Ewing's sarcoma. No distant site of the tumour was found so this was considered a primary orbital tumour. Combined chemotherapy and radiotherapy without surgical resection achieved an encouraging result in that the patient has remained in remission for 30 months after completion of treatment. The successful use of combined chemotherapy and radiotherapy, without surgery, adds further support to evidence that surgical excision may be avoided in selected cases of primary orbital Ewing's sarcoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

Autogenous palmaris longus tendon as frontalis suspension material for ptosis correction in children.

PURPOSE: To determine the safety and efficacy of autogenous palmaris longus tendon as a sling material in frontalis suspension surgery for ptosis correction in children. METHODS: In a prospective study, the authors evaluated 15 frontalis sling suspension surgeries using palmaris longus tendon in 14 consecutive children with congenital ptosis. The method of harvesting the palmaris longus tendon is described in detail. RESULTS: The mean age of the patients was 4.7 years (range, 2 to 7 years). At a mean follow-up of 30 months (range, 20 to 40 months), all ptotic eyelids were successfully corrected with good final lid position. No recurrence of ptosis was encountered. In one eye, knot slippage of the sling was related to upper eyelid trauma, which was readily repaired. Otherwise, no exposure keratitis, wound infection, eyelid contour abnormality, or ptosis overcorrection occurred. There were no complications associated with the palmaris longus tendon donor site. CONCLUSION: Frontalis suspension with autogenous palmaris longus tendon appears to be an effective treatment for congenital ptosis with poor levator function in children. Its use as an alternative material to fascia lata for sling surgery in children can be considered.

Blepharoptosis↗
PubMed1998

Short-term results of scleral intraocular lens fixation in children.

PURPOSE: To study the safety and efficacy of scleral intraocular lens (IOL) fixation in children. SETTING: A university practice. METHODS: This retrospective review evaluated the results and complications in 6 consecutive eyes of 3 children who had anterior vitrectomy, with or without lensectomy, and scleral IOL fixation to correct ectopia lentis or aphakia. RESULTS: At a mean follow-up of 17.3 months (range 13 to 21 months), all eyes had a stable and well-positioned posterior chamber IOL and good visual improvement. The only complication was asymptomatic pupillary capture of the IOL in 3 eyes. Reversal of the pupillary capture was achieved by pupil dilation with the patient in a supine position. CONCLUSIONS: The preliminary results of scleral IOL fixation in children are encouraging. The procedure's application in well-selected cases can be considered. However, its long-term safety and efficacy must be further assessed through studies with larger sample sizes and a longer follow-up.

Aphakia, Postcataract↗