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Biomedical subjects

D S Lam

Publications and source records attributed to D S Lam.

At least 163 records · Page 9Linked to original sources
PubMed1998

Incidence and predictive value of congenital hypertrophy of retinal pigment epithelium in Chinese familial adenomatous polyposis patients.

OBJECTIVE: To investigate the incidence and predictive value of congenital hypertrophy of retinal pigment epithelium (CHRPE) in the Chinese familial adenomatous polyposis (FAP) patients. METHODS: Eleven FAP patients and 28 at risk relatives from 7 families were examined for CHRPE lesions. RESULTS: CHRPE was present in all 11 FAP patients. Nine CHRPE lesions were found in 9 of the 28 at risk relatives. There were great intra and inter-familial variations of the CHRPE lesions. Two at risk relatives were diagnosed to have FAP only after our screening and subsequent proctosigmoidoscopy. Nine at risk relatives were put under high surveillance because of the presence of CHRPE. CONCLUSION: The incidence of CHRPE in the FAP patients in our study is 100%. Eye examination for CHRPE for FAP patients and their at risk relatives is of very high value. A central FAP registry is thus recommended.

Adenomatous Polyposis Coli↗
PubMed1998

Mycobacterium chelonei keratitis: report of a case and review of the literature.

BACKGROUND: Mycobacterium (M) chelonei keratitis is a rare opportunistic eye infection that can cause significant morbidity when not being treated properly. The first case was documented by Gangadharam et al in 1978 and since then, a total of 49 cases were reported in the literature. One alarming fact is that more than 50% of cases were found in the Chinese population and mostly reported in recent years. The key to successful management of M. chelonei keratitis is early diagnosis by high index of suspicion. In order to alert ophthalmologists of this condition, we report a typical case of M. chelonei keratitis and review the literature of all the reported cases with special reference to its risk factors, treatments and outcome. METHODS: The cases reported in the literature and a case of our own were reviewed and analyzed. RESULTS: Our case was a 42-year-old gentleman who developed M. chelonei keratitis following pterygium surgery. He had typical clinical features of irregular infiltrates with radiating projections, indistinct fluffy lesion margins, satellite lesions and associated epithelial defect. Penetrating keratoplasty was performed after failed medical treatments. He recovered fully with a best corrected visual acuity (BCVA) of 20/30 at 24 months after the corneal transplant. A total of 49 cases were reported in the literature. The major risk factor was corneal injury, including surgical trauma. Corneal foreign bodies (24 cases, 48%) were found to be highly correlated, especially metallic foreign bodies (16 cases, 32%). Diagnosis was usually delayed for weeks or months and medical treatment alone often failed. Amikacin is usually the treatment of choice but its efficacy is just sub-optimal. Multi-resistance to the commonly used board spectrum antibiotics is not uncommon. The drug sensitivity test against atypical mycobacterium is technically difficult to perform and in vitro results are well known to be poorly related to clinical response. Combined extirpative keratectomy and topical antibiotics had been tried and was shown to be effective. Penetrating keratoplasty appeared to be a good definitive treatment for drug-resistance and advanced cases. CONCLUSION: M. chelonei keratitis is a rare opportunistic infection. The major risk factor is eye injury, with foreign bodies or surgical trauma. Diagnosis is often missed and delayed as a result of its scarcity and variable presentations. High index of clinical suspicion with early diagnosis and prompt combined medical and surgical intervention seem to be the best measure to decrease ocular morbidity. Good alertness and knowledge of this condition would help our patients in the Far East as the literature review has shown a recent trend of increase in frequency and more than 50% of the reported cases come from the Chinese patients.

Adult↗
PubMed1997

Ocular-hypertensive response to topical steroids in children.

OBJECTIVE: The purpose of the study is to investigate the rate and degree of ocular-hypertensive response to topical steroids in Chinese children. DESIGN: The study design was an institutional, randomized, clinical trial. PARTICIPANTS: A total of 19 consecutive patients were studied. INTERVENTION: Topical steroids were administered to Chinese children younger than 10 years of age who underwent bilateral strabismus surgery. One eye was randomized to receive topical 0.1% dexamethasone (DMS), whereas the fellow eye received 0.1% fluorometholone (FML) six times per day for up to 4 weeks. Intraocular pressure (IOP) was measured on the day before operation and at postoperative days 1, 3, 6, 10, 13, and 27, then every 2 weeks thereafter until the IOP fell to preoperative levels. Topical steroids would be stopped if IOP was 30.00 mmHg or greater. MAIN OUTCOME MEASURES: Peak IOP and maximal change of IOP from baseline were measured and categorized into low, intermediate, and high levels. Time to peak IOP also was studied. RESULTS: A total of 16 patients were included. The peak IOP for DMS-treated eyes was 30.66 +/- 8.35 mmHg (range, 13.00-48.00 mmHg), whereas that in FML-treated eyes was significantly lower at 20.66 +/- 6.03 mmHg (range, 11.30-36.30 mmHg) (P = 0.001). The maximal change in IOP ranged from -2.60 to +31.00 mmHg in DMS-treated eyes (mean, 15.48 +/- 8.71 mmHg), almost double that of FML-treated eyes (range, +1.00 to +17.00 mmHg; mean, 5.83 +/- 4.96 mmHg) (P = 0.001). When the ocular-hypertensive responses of both DMS and FML groups were categorized into three levels of severity, significant differences were found between the two treatment groups (P = 0.001). In the DMS group, nine patients (56.25%) were high responders and six patients (37.5%) were intermediate responders. In the FML group, only one patient (6.25%) was a high responder. CONCLUSIONS: The ocular-hypertensive response to topical DMS in children occurs more frequently, more severely, and more rapidly than that reported in adults. A total of 56% of the studied children, all younger than 10 years of age, were high responders to topical DMS. Of these, 89% attained their peak IOP within 8 days. Its use in children should best be avoided if possible. It would be desirable to monitor the IOP when it is being used. Conversely, FML produced a much less ocular-hypertensive effect and therefore poses an acceptable risk of clinically significant pressure elevation.

Administration, Topical↗
PubMed1997

Neovascular glaucoma developing after uncomplicated cataract surgery for heavily irradiated eyes.

PURPOSE: The purpose of the study was to evaluate the effect of cataract surgery and postoperative panretinal photocoagulation (PRP) on the development of neovascular glaucoma (NVG) in heavily irradiated eyes. PATIENTS AND METHODS: The authors performed a retrospective study on the incidence of NVG in 90 eyes that had received megavoltage external beam irradiation at a retinal dose of 56 to 80 Gy and that had at least 48 months of follow-up. These eyes were categorized into different groups depending on whether cataract surgery or PRP was performed. Rates and proportions of NVG occurring in these groups were compared and analyzed with one-tailed Fisher's exact test. RESULTS: The incidence of NVG was significantly higher in patients who underwent cataract surgery without postoperative PRP (P < 0.01). Neovascular glaucoma did not develop in any patient who underwent cataract surgery and PRP. CONCLUSIONS: Cataract surgery may accelerate the development of NVG in heavily irradiated eyes. Photoablation of ischemic retina is recommended before cataract surgery or soon thereafter if cataract density precludes laser treatment.

Adult↗
PubMed1997

Cystic schwannoma of the orbit.

Cystic schwannoma of the orbit is unreported in the world literature. A 54-year-old Caucasian man presented to our clinic with a 5 year history of progressive right-sided proptosis and diplopia. A large paramedian cystic mass displacing the right globe downwards and laterally was demonstrated. From the clinical and radiological features, the presumptive diagnosis of right frontal sinus mucocoele was made. However, the excisional biopsy of the lesion revealed the rare diagnosis of cystic schwannoma, arising from a branch of the first division of the trigeminal nerve. Post-operatively, the patient had a smooth recovery with visual acuity of 20/20 in each eye; full binocular single vision was also re-established. The differential diagnoses of cystic orbital mass, and the radiological and histological findings of the lesion, are described and discussed.

Cysts↗
PubMed1997

Early correction of severe unilateral infant ptosis with the Mersilene mesh sling.

Ten consecutive cases of severe unilateral congenital ptosis were surgically corrected before 1 year of age (range 3-11 months) in an attempt to achieve early functional and cosmetic improvement. In all cases, a frontalis suspension using Mersilene mesh was performed. With a mean follow-up of 40.3 months (range 33-54 months), all patients achieved normal or near normal eyelid position and all had their chin-up head posture resolved. One patient developed a mild exposure keratitis that was treated successfully with topical antibiotics and lubricants. Our findings suggest that the Mersilene mesh sling has good potential for ptosis management in infants who are too young for fascial harvesting. However, a larger series with a longer follow-up period is required before the eventual safety and efficacy of the Mersilene mesh sling can be properly ascertained.

Age Factors↗
PubMed1997

Short-term results of using Lamellar Corneo-scleral patch graft for the Ahmed glaucoma valve implant surgery.

BACKGROUND: Human donor sclera is commonly used in glaucoma implant surgery to cover the external portiori of the silicone tube and prevent its erosion through the overlying conjunctiva. Corneo-scleral graft is used in this study as an alternative material for its desirable properties of being transparent, higher in tensile strength, cheap and more readily available. METHODS: Eighteen consecutive cases were implanted with the Ahmed glaucoma valve implant. The limbal portion of the silicone tube was covered by a corneo-scleral graft obtained from the corneo-scleral rim left over following corneal transplant operation. The effectiveness in protecting the tube from erosion or migration, the transparency of the patch graft and complications encountered after surgery were assessed. RESULTS: At a mean follow-up of 6 months, all tubes were well protected and no complications related to the patch graft were encountered during intra and postoperative period. All corneo-scleral grafts remained transparent and healthy at the latest follow-up. CONCLUSION: Lamellar corneo-scleral tissue from residual corneal transplant material, with its many unique properties and advantages, appears to be a cheap, easily available and effective patch graft material for glaucoma implant surgery. Further explorations and studies on this material are recommended.

Adolescent↗
PubMed1996

Palmaris longus tendon as a new autogenous material for frontalis suspension surgery in adults.

We performed a prospective study using the palmaris longus tendon as the sling material to correct 8 consecutive ptotic eyelids in 7 adults. All operations were done with the patient under local anaesthesia by a single surgeon (D.S.C.L.). With a mean follow-up period of 14 months (range 2-20 months), all the ptotic eyelids were well corrected with no recurrence, intraoperative or post-operative complications. Use of the palmaris longus tendon as an alternative to fascia lata for sling surgery in adults is recommended.

Adolescent↗
PubMed1996

Ocular defects in children and adolescents with severe mental deficiency.

To assess the need for eye care in children and adolescents with severe mental deficiency, a cross-sectional study of the prevalence and causes of ocular defects amongst these individuals was conducted. Two hundred and sixty residents in a mental handicap unit were examined from January 1992 to June 1993. It was found that there was an unusually high prevalence of severe visual impairment (25%), refractive errors (24%), squint (8%) and a number of organic ocular diseases (8%). All the patients studied were non-verbal and 18% of them were deaf. Only 23 patients could walk. The results emphasize the need for establishing an efficient system to provide regular ophthalmic care for children with severe mental deficiency.

Adolescent↗
PubMed1995

Acute monoblastic leukaemia with conjunctival tumours.

We describe an unusual occurrence of bilateral conjunctival tumours in a 25-year-old woman. This was the first sign of relapse of acute monoblastic leukaemia. There was also both marrow relapse and subsequent skin infiltration. No central nervous system involvement was detected. The tumours appeared as pink raised lesions in the upper conjunctivae of both eyes. They were not associated with pain or visual impairment. Conjunctival tumour biopsy revealed a dense mononuclear cell infiltration. Complete remission (conjunctival tumours, skin infiltration and bone marrow) was attained following systemic chemotherapy in combination with intrathecal chemotherapy.

Adult↗
PubMed1995

Cell cycle kinetics in pterygium at three latitudes.

The cell cycle kinetics of 93 specimens of pterygial tissue, as well as 19 specimens of normal conjunctiva, from patients at three sites representing three different latitudes (Singapore, 1 degree; Hong Kong, 22 degrees; and Little Rock, Arkansas, 34 degrees) were evaluated by flow cytometry. The results showed no difference in cellular proliferation patterns between pterygial and conjunctival tissue at any of the sites, suggesting that pterygium is not a disorder of excess cellular proliferation. Transmission electron microscopy showed extracellular matrix to be a prominent component of pterygium. Cellular proliferation patterns of primary and recurrent pterygium were not significantly different from each other. Factors associated with increased incidence of pterygium included male sex, outdoor occupation, and advanced age.

Adult↗
PubMed1994

Adrenoreceptor-mediated effect of neuropeptide Y decreases cardiac inotropic responses.

The effect of neuropeptide Y on the number and affinity of catecholamine receptors in the ventricular myocardium was investigated. Receptor binding studies showed that incubation of cardiac membrane in the presence of neuropeptide Y (NPY, 10(-7) M) decreased the number of alpha/beta-adrenoceptor binding sites (Bmax) without affecting the affinity (KD) of these receptors. Although not able to modulate the contractility by itself, NPY was able to decrease the positive inotropic effects of phenylephrine and isoproterenol in the isolated, perfused myocardium. Ca2+/Mg(2+)-ATPase activity, measured from the sarcolemma, sarcoplasmic reticulum and myofibrils, was unaltered whereas the activity of sarcolemmal Na+/K(+)-ATPase was decreased when NPY was included in the media. On the other hand, NPY was shown to increase the phosphoinositide-phospholipase C associated with the sarcolemma. These findings support the hypothesis that NPY modulates postsynaptic adrenergic receptors in the myocardium and can affect the adrenergic-induced, inotropic response.

Animals↗