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Biomedical subjects

V Balakrishnan

Publications and source records attributed to V Balakrishnan.

At least 37 records · Page 2Linked to original sources
PubMed1999

A review of 5 years' experience in the use of botulinium toxin A in the treatment of sixth cranial nerve palsy at the Singapore National Eye Centre.

INTRODUCTION: This retrospective study reports our experience on the use of botulinum toxin A (BTXA) in the treatment of sixth cranial nerve palsy at the Singapore National Eye Centre. BTXA is derived from clostridium botulinum; it causes temporary paralysis of the extraocular muscle (medial rectus) into which it is injected, thus preventing its contracture and allows the antagonist lateral rectus muscle to take up the slack and reduce or correct the ocular misalignment. METHODS: Nineteen patients had BTXA injection for estropia due to sixth cranial nerve palsy during the period September 1992 to August 1997. The sixth cranial nerve palsy was related to nasopharyngeal carcinoma in 76.7% of cases. Follow-up after the last injection ranged from zero (defaulted) to 21 months (mean 8, median 6 months). RESULTS: A total of 25 injections were given to 19 patients. Seven patients (36.8%) had final ocular alignment within 10 prism dioptres of orthotropia of which six achieved fusion at primary gaze position. There was no correlation between the number of injections per patient and the size of strabismus or grade of lateral rectus muscle function. The incidence of ptosis was 48%, subconjunctival haemorrhage 16% and hypertropia 16%. DISCUSSION: Our results suggest that those patients with smaller strabismus and a shorter time interval between onset of strabismus and botulinum injection tend to achieve better outcome in terms of fusion or ocular alignment within 10 prism dioptres of orthotropia. The treatment of strabismus with BTXA is an acceptable approach in selected patients. The procedure is simple, safe, cheap, effective, and avoids the risks of general anaesthesia. It can substitute for or eliminate the need for strabismus surgery in some cases of sixth nerve palsy.

Abducens Nerve↗
PubMed1998

High-pressure paint gun injury to the orbit and ocular adnexa.

High-pressure injection injury to the orbit and adnexa is a rare but potentially blinding type of trauma. Few cases of such injury have been reported in the literature. A 27-year-old Indian man accidentally injected paint material from a high-pressure nozzle gun into his left eye. Radiological investigation revealed the presence of paint material in the orbital tissues and the ethmoidal sinuses. The patient underwent two orbital surgeries to remove the paint material. He later developed signs suggestive of limbal stem cell failure and was treated with limbal stem cell autografting. He also has ophthalmoplegia with a compensatory anomalous head posture that was managed conservatively. We report the clinical course and outcome of this unfortunate patient to highlight the complexity of such an injury and the need for a multidisciplinary approach in its management.

Adult↗
PubMed1998

Systematic method for determining intravenous drug treatment strategies aiding the humoral immune response.

This paper delineates a systematic method for determining "optimal" intravenous drug delivery strategies for patients having illnesses that primarily evoke a humoral immune response and are treatable by antibiotics. The method derives from a nonlinear, distributed predator-prey model that captures the dominant antigen and antibody interaction. This model is developed from relevant physiology, past predator-prey-type modeling work, available data, and pertinent parameter identification. Embedding this predator-prey model into a larger class of uncertain systems, by a finite dimensional approximation and a transformation to a linear fractional representation, enables the application of robust control based on linear matrix inequality optimization techniques. The optimization problem is solved by minimizing an upper bound on a measure of the total drug delivered subject to patient recovery (stability to healthy equilibrium state). Specifically, the paper addresses the treatment of Haemophilus influenzae through modeling, controller development, and simulations of infected adult patients subjected to typical and proposed intravenous antibiotic treatments. Through simulations the proposed intravenous drug strategy shortens patient recovery time, lowers peak drug concentrations and decreases the total drug administered when compared to standard antibiotic strategies.

AIDS-Related Opportunistic Infections↗
PubMed1998

OphthWeb---cost-effective telemedicine for ophthalmology.

'OphthWeb' is an ophthalmic electronic medical record that can be accessed locally and globally via the Internet. OphthWeb can provide secure multimedia patient data to doctors, patients, and health care providers at any time and in any place. Patients have secured access to their own records in the convenience of their homes or during any emergency at any time or place around the world. OphthWeb provides interactive educational information and answers frequently asked questions by way of multimedia images on the Worldwide Web. A data transmission trial was conducted between the Xiamen Eye Centre in the Fujian province in southern China and Singapore. Clinical records, voice messages, and fundus and slit-lamp images were transmitted from Xiamen, and an off-line dialogue by e-mail and Internet-relay chat was conducted. The time delay from transmission to receipt was 30 minutes, which would be adequate to respond to most ophthalmic emergencies. This pilot project will promote computer literacy among doctors, and inter-institutional interaction in the health care profession. OphthWeb can provide telemedicine and electronic medical records at a low cost and great convenience.

Journal Article↗
PubMed1998

Refractive change following pterygium surgery.

PURPOSE: We conducted a prospective study of patients with primary pterygia to analyze surgically-induced astigmatic changes following pterygium surgery and their relation to pterygium morphology and size. METHODS: One hundred twenty-three eyes of 123 adult patients with primary pterygia were evaluated. Pterygium was graded according to morphology and the extent of corneal encroachment. Manifest refraction was performed preoperatively and at 1, 3, and 6 months postoperatively. Patients underwent either the bare sclera technique of pterygium excision or conjunctival grafting. Surgery was performed by one surgeon. Olsen's method of vector decomposition was used to analyze surgically-induced astigmatism. RESULTS: The mean magnitude of preoperative astigmatism was 0.99 D, with vector decomposition revealing a relative flattening of the cornea in the horizontal meridian. Astigmatism of 1.00 D or more was seen when the pterygium exceeded 3.5 mm beyond the limbus. Postoperatively, a steepening of the cornea in the horizontal meridian was demonstrated, the magnitude of which was related to pterygium size (P = 0.0001). ANOVA testing showed no significant difference (P > 0.05) when pterygia were divided according to morphology. CONCLUSIONS: This study confirms that pterygium excision induces a reversal of pterygium-related corneal flattening. A strong correlation was also found between the horizontal extent of pterygium encroachment and astigmatic change following surgery.

Adult↗
PubMed1997

Conservative management of extradural abscess complicating spinal-extradural anaesthesia for caesarean section.

We report a case of lumbar extradural abscess that presented 9 days after an elective Caesarean section performed under combined spinal-extradural anaesthesia. This was successfully treated conservatively with full recovery. The clinical course included development, and then resolution, of mild paraparesis. Conservative treatment of an extradural abscess in the obstetric population has not been described previously.

Abscess↗
PubMed1997

Retinoblastoma in Singapore: 1976 to 1995.

There were at least 56 local and 42 foreign patients seen in Singapore between 1976 and 1995 inclusively. The local incidence rate is 1 in 15789 live-births, and there appears to be no predilection for sex and race. Ninety-eight per cent presented before the age of five with the average age at diagnosis being 18 months. Bilateral cases were diagnosed earlier than unilateral cases. At least 17% are hereditary, with only 2 of these with positive family histories. Of the 41 patients studied for presenting complaints, 82.9% had leukocoria, 19.5% had strabismus and 12.2% had decreased visual acuity. The main mode of treatment was enucleation alone in unilateral disease; in bilateral cases, the main mode was enucleation of the more badly affected eye together with radiotherapy and cryotherapy of the fellow eye. Ninety per cent of all patients who underwent treatment have had enucleation done. Four patients defaulted treatment--with counselling of the parents of these patients, this number could be reduced or at least kept low. Patients with early diagnosis and treatment are more likely to survive. Eight of the 56 patients died. However, with better treatment modalities, the prognosis for both life and vision have, in recent years, improved significantly.

Age Distribution↗
PubMed1997

Photorefractive keratectomy for the treatment of compound myopic astigmatism using the ablatable mask.

Eight eyes of 8 patients with compound myopic astigmatism were treated with excimer laser photorefractive keratectomy (PRK) using a hand-held ablatable mask in conjunction with the Summit excimer laser. The attempted correction ranged from -1.25 to -400 dioptres (D) of astigmatism and 0 to -8.00 D of myopia. All eyes had attained at least 6 months of postoperative follow-up. Five of the 8 eyes achieved an unaided visual acuity of 6/12 or better. Postoperative refractions ranged from -0.50 to -3.50 D of refractive cylinder and from +0.50 to -3.75 D of spherical error. Decentration of the ablation zone was encountered in 3 eyes due to shifts in patients' fixation. Technical difficulty with the use of the hand-held ablatable mask limited the widespread application of this procedure and it has now been superseded by newer excimer laser systems which can correct astigmatism without having to employ a mask. Despite this, because of the theoretical ability of the mask to correct any form of refractive error, the concept of the mask shape transfer process will remain as a potential alternative in refractive surgery, especially for correction of hyperopia and hyperopic astigmatism.

Adult↗
PubMed1997

Spontaneous corneal perforation in premature infants.

Spontaneous corneal perforation in premature infants not due to birth trauma is a rare event, with only 8 cases reported in the literature. We recently encountered a case of spontaneous corneal perforation in an extremely premature infant born at 26 weeks of gestation. The mechanism leading to this event was corneal exposure resulting in corneal epithelial defect. Clinical evidence of secondary infection ensued and this led to cornea thinning, descemetocoele formation and subsequent perforation with extrusion of intraocular contents. Although other mechanisms were responsible in the previously reported cases, we feel that exposure keratopathy leading to this complication poses a potential hazard to all premature infants. An awareness among care givers of this potential complication together with avoidance of exposure keratopathy in this group of patients is paramount in preventing this visually catastrophic event.

Cornea↗
PubMed1995

Retinoblastoma with micrometastasis to CSF.

A 28 mth old male presented with a squint and leukocoria. Clinical examination and computerized tomography (CT) suggested a unilateral retinoblastoma with distal optic nerve involvement. Investigations for distant metastasis including lumbar puncture cytology were negative. The eye was enucleated and 12 mm of optic nerve was excised via a combined neurosurgical/ophthalmological approach. Histopathological examination confirmed the optic nerve to the point of excision was free of tumor. However, cytology of cerebrospinal fluid (CSF) from the Sylvian fissure, taken at the time of surgery, revealed malignant retinoblastoma cells. The patient was treated with intrathecal and intravenous chemotherapy, and cranial radiotherapy. He is alive and well 4 yrs later. This case displays the importance of CSF cytology from the Sylvian fissure, as it dramatically changed the management and prognosis for the child. The role of lumbar puncture cytology in excluding CSF micrometastasis can be unreliable. A neurosurgical approach to the optic nerve has the potential to gain access to a long length of optic nerve, should it be involved with tumor, and also allows direct CSF sampling.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Decentered ablation zones resulting from photorefractive keratectomy with an erodible mask.

Four patients underwent photorefractive keratectomy for compound myopic astigmatism using the erodible mask. All achieved improvements in unaided visual acuities despite manifesting varying levels of decentration of the ablated zones. However, one patient had significant monocular diplopia because of the severity of the decentration. The problems with the present system include the use of a NON coaxial microscope; difficulty with obtaining and maintaining proper alignment of the excimer laser beam to the erodible mask and the central corneal zone; the inability to interrupt and restart the procedure due to the ablation of the reference marks on the mask; and patient discomfort. We suggest installation of the PMMA mask at the laser aperture in order to alleviate the above difficulties. In the meantime, use of a coaxial microscope, a limbal suction device for fixation, permanent reference marks on the mask and peribulbar anaesthesia may be helpful.

Adult↗
PubMed1993

Occupation and cancers of the lung and bladder: a case-control study in Bombay.

Associations between occupation and cancers of the lung (n = 246) and bladder (n = 153) were examined in a case-control study. Controls (n = 212) comprised cases of oral (75%) and pharyngeal cancers (13%) and non-neoplastic oral diseases (12%) at the same hospital. Only males were studied. A personal interview was conducted and a lifetime occupational history and information on demographic and relevant confounding factors including tobacco use were obtained. For lung cases, comparing 'ever' employed with 'never' employed in a particular occupation, significantly elevated risks (adjusted for smoking) were found for textile workers (odds ratio [OR] = 1.99, 95% confidence interval [CI]: 1.3-3.6) and cooks (OR = 4.48, 95% CI: 1.2-16.9). High risks were also observed among ship and dockyard workers (OR = 2.87, 95% CI: 0.8-10.1) and wood workers (OR = 2.88, 95% CI: 0.9-9.6). For bladder cancers, significantly elevated risk was observed only for chemical/pharmaceutical plant workers (OR = 4.48; 95% CI: 1.2-16.5). Two other sets of risk estimates were obtained: one by comparison with a second unexposed group made up of occupations where there was little likelihood of exposure to any cancer-causing occupational agent, and the other by fitting logistic regression models to the data. All methods yielded similar risk estimates. Tobacco smoking but not tobacco chewing was a risk factor for both sites.

Case-Control Studies↗
PubMed1993

Three year results of radial keratotomy surgery at the National University Hospital, Singapore.

This paper presents the three year results of radial keratotomy (RK) surgery on 51 of the first 59 consecutive eyes at the National University Hospital in Singapore. Before surgery, uncorrected visual acuity was worse than 6/24 in all eyes with 33.3% worse than 6/60. The average pre-operative spherical equivalent (SE) was -4.56 Dioptres(D). Three years after surgery the mean SE was -0.66D, a change of 3.9D; and 72.5% of eyes were within 1D of emmetropia. 70.6% had uncorrected visual acuity of at least 6/12 with no eyes having worse than 6/60 visual acuity. Analysis based on levels of pre-operative myopia showed that the best visual and refractive results were obtained in patients with SE of -6D or less. None of the patients were troubled by complications such as glare, fluctuating vision, irritation and discomfort three years after surgery. Our results indicate that RK surgery is safe and effective through the three years and more following surgery.

Adult↗