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P T Chew

Publications and source records attributed to P T Chew.

At least 19 recordsLinked to original sources
PubMed2001

Acute primary angle-closure: long-term intraocular pressure outcome in Asian eyes.

PURPOSE: To report the long-term outcome of intraocular pressure after laser peripheral iridotomy in Asian eyes with acute primary angle-closure. METHODS: Retrospective study of 111 eyes of 96 consecutive patients with acute primary angle-closure, presenting at the National University Hospital, Singapore, from 1990 to 1994. The presenting features of the affected eye and the treatment instituted were recorded. The subsequent long-term intraocular pressure outcome was analyzed. An increase in intraocular pressure on follow-up was defined as increase in intraocular pressure greater than 21 mm Hg and requiring treatment by medication or surgery. RESULTS: The mean follow-up period was 50.3 months (range, 9 to 107 months). The mean presenting intraocular pressure was 52.8 mm Hg (range, 28 to 80 mm Hg). One hundred ten eyes were treated with laser peripheral iridotomy, with resolution of the acute episode and intraocular pressure less than 21 mm Hg in all eyes after laser peripheral iridotomy. Of these, only 46 eyes (41.8%) were successfully treated with laser peripheral iridotomy alone in the long term. Sixty-four eyes (58.1%) developed an increase in intraocular pressure (requiring treatment) on follow-up, of which 49 eyes developed an increase in intraocular pressure within the first 6 months after acute primary angle-closure. Thirty-six eyes (32.7%) eventually underwent trabeculectomy because of uncontrolled intraocular pressure despite laser and medical therapy. CONCLUSIONS: In this study of Asian eyes, a high proportion (58.1%) of eyes with acute primary angle-closure developed an increase in intraocular pressure on long-term follow-up after resolution of the acute attack, despite the presence of a patent laser peripheral iridotomy. These results suggest a racial difference in the outcome of laser peripheral iridotomy after acute primary angle-closure in Asians, compared with Caucasians. Because a majority of eyes that develop an increase in intraocular pressure do so within the first 6 months of presentation, close monitoring of intraocular pressure is advised in the follow-up of patients with acute primary angle-closure.

Acute Disease↗
PubMed2001

A randomized double-masked crossover study comparing latanoprost 0.005% with unoprostone 0.12% in patients with primary open-angle glaucoma and ocular hypertension.

PURPOSE: To compare the intraocular pressure)-lowering effect and side effects of latanoprost 0.005% once daily with unoprostone 0.12% twice daily. METHODS: Sixty patients with primary open-angle glaucoma or ocular hypertension were randomized to receive either latanoprost once daily in the evening and placebo once daily in the morning, or unoprostone twice daily in the morning and evening. The study was double masked and followed a crossover design with two treatment periods of 1 month separated by a 3-week washout period. The intraocular pressure was measured at 9 AM and 5 PM on the baseline and day 28 visits, and at 9 AM on day 2 and day 14 visits of each treatment period. The 9 AM measurement was taken 2 hours and 13 hours after the last drop of unoprostone and latanoprost, and the 5 PM measurement was at 10 and 21 hours, respectively. The mean of the measurements was calculated. Safety parameters were also recorded. RESULTS: Fifty-six patients completed both treatment periods and had intraocular pressure data available for evaluation. After 1 month of treatment, latanoprost significantly reduced intraocular pressure (mean +/- SEM) by 6.1 +/- 0.5 mm Hg (P <.001) and unoprostone by 4.2 +/- 0.4 mm Hg (P <.001) adjusted from an overall baseline of 22.3 +/- 0.5 mm Hg and 23.2 +/- 0.4 mm Hg, respectively. The difference of 1.9 mm Hg between treatments was statistically significant in favor of latanoprost [P =.003, analysis of covariance (ANCOVA)]. Unadjusted analysis of responders using the percentage decrease in intraocular pressure showed that the proportion of responders in the latanoprost-treated group was greater than in the unoprostone-treated group. Adverse ocular symptoms and findings were mild in both treatment groups. Eye redness and ocular irritation were the most frequently reported events. CONCLUSIONS: Latanoprost once daily was significantly more effective in reducing intraocular pressure compared with unoprostone twice daily after 1 month of treatment in patients with primary open-angle glaucoma and ocular hypertension. Both drugs were well tolerated with few ocular adverse events.

Adult↗
PubMed2001

Indocyanine green anterior segment angiography for studying conjunctival vascular changes after trabeculectomy.

BACKGROUND: The aim of the study was to evaluate the use of indocyanine green (ICG) for angiography of the anterior segment to characterize conjunctival and episcleral vasculature changes after trabeculectomy. METHODS: This was a prospective evaluation of anterior segment ICG angiography in 10 eyes of 10 patients undergoing trabeculectomy for the first time. Trabeculectomy was performed with intraoperative sponge application of 5-fluorouracil (5 cases) or mitomycin C (5 cases). Anterior segment ICG angiography was performed prior to surgery, then at 2 weeks and 2 months after surgery. RESULTS: With ICG, the anterior segment vessels were well delineated, including deep episcleral veins, which have not been clearly shown in previous angiographic techniques. Late phases of the angiogram could also be studied. The vascular alterations after trabeculectomy noted included oss of vascularity over the bleb area and vascular anastomoses along the perimeter of the avascular bleb. CONCLUSIONS: Angiography using ICG has potential as an investigative tool to study the conjunctival and episcleral vasculature changes after trabeculectomy.

Adult↗
PubMed2001

Vascular patterns in pterygium and conjunctival autografting: a pilot study using indocyanine green anterior segment angiography.

AIMS: To characterise the vasculature of pterygium using indocyanine green (ICG) anterior segment angiography and to demonstrate the pattern of revascularisation following conjunctival autografting. METHODS: ICG anterior segment angiography was performed on nine patients with pterygium. Angiography was repeated at 1-2 weeks and 2 months following conjunctival autografting in these patients. RESULTS: Angiography showed a single feeder vessel originating from the anterior conjunctival circulation in six cases (66.7%). This vessel branched to form the radial vessels of the pterygium. Following conjunctival autografting, reperfusion of the vessels in the conjunctival autograft was demonstrable as early as 1 week postoperatively from the episcleral bed. At 2 months postoperatively, the graft appeared well perfused with mild leakage demonstrable at the edges of the graft. CONCLUSIONS: A single feeder vessel from the anterior conjunctival circulation branches to form the radial vessels in pterygium. Reperfusion of conjunctival autografts occurs as early as 1 week postoperatively from the episcleral bed.

Anterior Eye Segment↗
PubMed2000

Comparison of the intraocular pressure-lowering effect of latanoprost and timolol in patients with chronic angle closure glaucoma: a preliminary study.

OBJECTIVE: To compare the intraocular pressure (IOP)-reducing effect and side effects of 0.005% latanoprost once daily to 0.5% timolol twice daily in patients with primary chronic angle closure glaucoma (CACG). DESIGN: Randomized, double-masked two-center clinical trial. PARTICIPANTS: Thirty-two Asian patients with CACG, defined as glaucomatous optic neuropathy with a compatible visual field defect and at least 6 clock hours of synechial angle closure on gonioscopy were recruited. All patients had previous peripheral iridotomy (PI) with IOP >21 mmHg after PI and were thereafter controlled (IOP <22 mmHg) with one or two pressure-reducing drugs. INTERVENTION: After a washout period, the patients were randomized to a 2-week treatment period with either placebo in the morning and 0.005% latanoprost in the evening or 0.5% timolol twice daily. MAIN OUTCOME MEASURES: The short-term IOP reduction of latanoprost and timolol in patients with CACG. IOP was measured at baseline, and after 2, 7, and 14 days of treatment. In addition, the short-term ocular and systemic adverse events of the two drugs were evaluated. RESULTS: Thirty patients completed the study. Two patients in the timolol group were withdrawn because of inadequate IOP control. Compared with baseline, the IOP after 2 weeks of treatment was statistically significantly reduced by 8.8 +/- 1.1 mmHg (mean +/- SEM, P < 0.001) in the latanoprost group, and by 5.7 +/- 0.9 mmHg (P < 0.001) in the timolol group. The difference in IOP reduction between the two treatment groups was 3.1 +/- 1.5 mm Hg in favor of latanoprost (P = 0.04). The main ocular adverse events reported in both treatment groups were conjunctival hyperemia and discomfort. CONCLUSIONS: In this preliminary study, a significantly greater IOP reduction was achieved with 0.005% latanoprost once daily compared with 0.5% timolol twice daily in patients with CACG. The results suggest that latanoprost may be a therapeutic choice for the medical treatment of primary CACG.

Adrenergic beta-Antagonists↗
PubMed2000

Accuracy of clinical estimates of intraocular pressure in Chinese eyes.

PURPOSE: To investigate the validity of clinical estimates of intraocular pressure (IOP) in Chinese people. DESIGN: Prospective, cross-sectional, hospital-based in vivo study. PARTICIPANTS: Twenty-three ethnic Chinese adults (aged 35-82 years) undergoing routine phacoemulsification surgery were examined. TESTING: "True" IOP was measured with a solid-state hemodynamic monitor through a cannula in the anterior chamber. IOP was set successively to 10, 20, and 30 mmHg in each subject, using a reservoir of balanced salt solution. Intraocular pressure was simultaneously estimated by use of a hand-held applanation tonometer (Perkin's) and a Tono-Pen. The association between ocular biometric variables and measurement error was examined. MAIN OUTCOME MEASURES: The median of three readings at each IOP level was taken as the IOP estimate of each instrument. Measurement error was calculated as the mean difference (tonometer minus direct measurement). RESULTS: The error for the hand-held applanation tonometer was -1.6, -4.3 and -5.7 at 10, 20, and 30 mmHg, respectively. For the Tono-Pen the measurement error was +0.4, -2.0, and -4.1 at 10, 20, and 30 mmHg, respectively. We could identify no association between measurement error and corneal thickness or curvature, anterior chamber depth, or axial length. CONCLUSIONS: The applanation tonometer and Tono-Pen underestimate the true IOP in Chinese eyes. Error increases as true IOP increases. These tonometers do not give an accurate estimate of IOP in East Asians.

Adult↗
PubMed2000

Acute primary angle closure in an Asian population: long-term outcome of the fellow eye after prophylactic laser peripheral iridotomy.

PURPOSE: To study the long-term outcome of fellow eyes of Asian patients with acute primary angle closure (APAC) who underwent prophylactic laser peripheral iridotomy (LPI). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Ninety-six consecutive patients with APAC at presentation to one Singapore hospital from January 1990 through December 1994. METHODS: The presenting features of the fellow eye were recorded, and the subsequent long-term intraocular pressure (IOP) outcome after LPI was analyzed. All fellow eyes were initially treated with pilocarpine 2% eyedrops four times daily before LPI, which was performed within 1 week of presentation. For any eye, a rise in IOP during follow-up was defined as a rise in IOP requiring treatment by medication or surgery. MAIN OUTCOME MEASURES: Incidence of acute angle closure and IOP. RESULTS: The mean follow-up period was 50.8 months (range, 9-99 months). Of the 96 patients, 15 patients had bilateral APAC, and APAC developed in one fellow eye before LPI could be performed. The remaining 80 fellow eyes were studied. No cases of APAC developed after prophylactic LPI. Seventy-one fellow eyes (88.8%) were successfully treated with LPI alone without the need for additional glaucoma treatment in the long term. Seven eyes (8.8%) had IOPs of 21 mmHg or less on presentation, but a rise in IOP developed on follow-up despite the presence of a patent LPI. Two fellow eyes (2.5%) had signs of preexisting chronic angle closure glaucoma at presentation and required further glaucoma treatment even after LPI. There were no significant complications from the procedure in any of the fellow eyes studied. CONCLUSIONS: In this Asian population with APAC, prophylactic LPI is safe and effective in preventing acute angle closure in fellow eyes. In addition, prophylactic LPI prevents long-term rise in IOP in 88.8% of fellow eyes (with approximately 4 years of follow-up). However, because a small proportion of fellow eyes did experience a rise in IOP within the first year, despite the presence of a patent LPI, close monitoring is still advised in the follow-up of fellow eyes of patients with APAC.

Acute Disease↗
PubMed2000

Long-term clinical course of primary angle-closure glaucoma in an Asian population.

PURPOSE: To study the long-term clinical course of patients with primary angle-closure glaucoma (PACG). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Sixty-five consecutive patients who were diagnosed with PACG at one Singapore hospital from January 1990 through December 1994. METHODS: Primary angle-closure glaucoma was defined as the presence of glaucomatous optic neuropathy and compatible visual field loss associated with a closed angle in the same eye. All study eyes underwent laser peripheral iridotomy (LPI). There were two groups of patients studied. Group A consisted of those with a past documented history of an episode of acute angle closure (that had resolved after LPI). Group B consisted of those with no previous acute episode. The presenting features, management, and subsequent long-term intraocular pressure (IOP) outcome were analyzed. MAIN OUTCOME MEASURES: Intraocular pressure and the need for further glaucoma treatment. RESULTS: The follow-up period was 63 +/- 29 months (mean +/- standard deviation). The mean presenting IOP was 40 +/- 16 mmHg, and the presenting vertical cup-to-disc ratio was 0.6 +/- 0.2. Of the 83 eyes, only five eyes (6%) did not require any treatment after LPI in the long term. In group A (35 eyes), all eyes required further treatment with antiglaucoma medications. Twenty-two eyes (62. 9%) eventually underwent filtering surgery at a mean of 7.3 months after the commencement of treatment. In group B (48 eyes), 43 eyes (89.6%) underwent further medical therapy, of which 22 eyes (45.8%) eventually underwent filtering surgery at a mean of 18.4 months after the commencement of treatment. CONCLUSIONS: Despite the presence of a patent LPI, most eyes with established PACG require further treatment to control IOP. Medical therapy fails in most cases, necessitating filtering surgery. Patients risk experiencing further glaucomatous visual damage if this trend is not detected.

Adult↗
PubMed2000

Corneal transmissibility of diode versus argon lasers and their photothermal effects on the cornea and iris.

PURPOSE: Diode laser (810 nm) may possess theoretical advantages over the argon blue-green laser (488 nm) for iridotomy/iridoplasty in an eye with oedematous cornea, such as the acute angle-closure glaucoma (AACG) patient, because of better diode laser tissue penetration in opaque media. We assessed the transmissibility of diode and argon lasers through corneas of varying clarity and evaluated the histopathological features of cornea and iris burns produced by these lasers. METHODS: The transmission of diode and argon lasers through human donor corneal buttons of three grades of clarity--clear, intermediate, and hazy--were compared. Corneal buttons of these varying levels of clarity were also treated with argon and diode lasers, with the beams deliberately focused onto the mid-stroma to assess their photothermal effects. Exposed pigmented irides from whole human eyes were treated directly with argon and diode lasers. The lasers were delivered via slit-lamp systems and the energy settings used were 1000 mW for argon and 980 mW for diode; spot sizes for both lasers were 100 microm, with exposure durations of 0.1 s. Light microscopy studies of these tissues were performed. RESULTS: Transmissibility of diode laser in clear, intermediate, and hazy corneas were 89, 87 and 85% respectively and was significantly superior to argon laser (78, 73 and 70% respectively; P < 0.001, paired Student's t-test). Diode laser did not produce morphological changes in all three grades of corneas whereas argon-laser-treated hazy corneas showed photothermal damage. Both lasers produced deep iris burns, with the diode laser tending to produce deeper burns. CONCLUSION: Our findings suggest that diode laser may be the ideal laser for iridotomy/iridoplasty in the AACG patient with hazy cornea.

Acute Disease↗
PubMed2000

Rates of hospital admissions for primary angle closure glaucoma among Chinese, Malays, and Indians in Singapore.

AIM: To estimate the rates of hospital admissions for primary angle closure glaucoma (PACG) in Chinese, Malays, and Indians in Singapore METHODS: A population-wide hospital discharge database in Singapore was used to identify all hospital admissions with a primary discharge diagnosis of PACG (International Classification of Disease-CM code: 365.2). The Singapore census was used for denominator data. RESULTS: Between 1993 and 1997 there were 894 hospital admissions for PACG. The mean annual rate of PACG admissions was 11.1 per 100 000 (95% confidence interval (CI), 10.4, 11.8) among people aged 30 years and over. The annual rate was highest for Chinese (age and sex adjusted rate: 12.2 per 100 000), which was twice that of Malays (6.0 per 100 000) and Indians (6.3 per 100 000). Females had two times higher rates than males in all three races (age adjusted relative risk: 2.0, 95% CI: 1.7, 2.3). CONCLUSION: Malay and Indian people had identical rates of hospital admissions for PACG, which were only half the rates compared with Chinese.

Adult↗
PubMed1999

A major review of antimetabolites in glaucoma therapy.

Antimetabolites have been used in combination with filtering surgery to improve surgical results for more than 10 years. Based on research published since the introduction of antimetabolites right up to date, we discuss the various forms of antimetabolites that have been used, including drugs and irradiation. Among the drugs used, mitomycin C and 5-fluorouracil are the most prominent. We discuss the background of these agents, the progress in the use of antimetabolites and the research done on these drugs. These agents have been used both intra-operatively and perioperatively. We discuss the indications for their use, their mode of action, the techniques of usage, their variations as well as the complications and the treatment of complications.

Antimetabolites↗
PubMed1997

Incidence of acute primary angle-closure glaucoma in Singapore. An island-wide survey.

OBJECTIVES: To determine the incidence of acute primary angle-closure glaucoma (APACG) in Singapore and to identify demographic and meteorological risk factors. DESIGN: A prospective, island-wide incidence study. SETTING: All government and private ophthalmological practices in Singapore, from March 1, 1995, to February 29, 1996. METHODS: New cases of APACG were identified by all ophthalmologists in Singapore during a 1-year period. Demographic and clinical details were recorded. RESULTS: One hundred eighty-nine people (208 eyes) were seen with APACG for the first time during the 1-year period. These new cases represent an incidence of 12.2 per 100,000 per year (95% confidence interval, 10.5-13.9) in those aged 30 years and older. Major risk factors identified were female sex (relative risk, 2.4), Chinese ethnic origin (relative risk, 2.8), and age of 60 years or older (relative risk, 9.1). Half of those affected were seen 3 days or more after the onset of symptoms. Attacks were more frequent on hotter days. There also was a relationship between the number of attacks per day and the mean number of sunspots and mean solar radio flux during the previous 30 days. CONCLUSIONS: There is a high incidence of APACG in Singapore, with elderly women being the highest risk group. Chinese Singaporeans are at higher risk than other ethnic groups (Malay and Indian). There is often a substantial delay before these patients consult a physician. The onset of APACG seems to be associated with meteorological factors.

Acute Disease↗
PubMed1997

Diode laser contact transscleral cyclophotocoagulation for refractory glaucoma in Asian patients.

PURPOSE: To evaluate the effectiveness and safety of diode laser contact transscleral cyclophotocoagulation in Asian patients with refractory glaucoma by lower energy settings with an innovative probe featuring a glass ball tip that focused the laser beam onto the ciliary body. METHODS: This prospective clinical study included consecutive Asian patients with dark irides and confirmed for glaucoma. Only one eye of each patient was treated. Diode laser contact transscleral cyclophotocoagulation treatment was performed with the center of the probe placed 1.5 mm behind the limbus. About 30 pulses of 810-mm laser radiation (power, 1.8 to 2.0 W; duration, 0.3 to 0.5 second) were applied around the eye. Patients were examined at fixed postoperative intervals. Intraocular pressure levels and postoperative complications were recorded. The relation between patient and disease characteristics, total laser energy delivered, and intraocular pressure effects were analyzed. RESULTS: Thirty-three patients were studied, with a mean follow-up period of 9.4 months. An average 56% of patients showed a 30% or greater drop in intraocular pressure. About 38% of patients achieved sustained intraocular pressure lowering to below 22 mm Hg at 18 months. Complications were few and included transient hypotony and iritis. CONCLUSIONS: In Asian patients with refractory glaucoma or painful glaucomatous eyes with poor visual acuity (defined for this study as worse than 20/200), low-energy-setting diode laser contact transscleral cyclophotocoagulation by means of the glass ball probe is relatively effective and safe.

Adult↗
PubMed1997

Clinical course and outcome of primary acute angle-closure glaucoma in Singapore.

PURPOSE: Data is lacking with regard to the factors which may predict the outcome of an acute glaucoma eye to treatment and its long-term prognosis. This study was carried out to identify such factors, in particular among Singaporeans. METHODS: Fifty-seven eyes were included in this retrospective analysis and factors analysed included age and sex; the duration of onset of symptoms to the time they presented to hospital; state of pupil and presenting intraocular pressure (IOP); whether attack is terminated by medical treatment alone or a second procedure (eg laser, trabeculectomy) was required; final outcome with respect to the development of chronic angle closure glaucoma and state of pupil at last follow-up. RESULTS: Patients with 24 to 72 hours' delay in presentation had a relative risk of 2.78 (CI = 1.03-7.46) in developing chronic glaucoma. Those who required the addition of a laser procedure to control the initial presenting IOP while those who proceeded to a trabeculectomy had relative risks of 3.63 (CI = 1.49-8.89) and 4.83 (CI = 1.18-19.7) respectively in developing chronic glaucoma when compared to patients who did not require any secondary treatment. CONCLUSION: Delay in presentation, and unresponsiveness to medical treatment in termination of the acute attack in an acute angle closure glaucoma patient carry a significant risk of chronic glaucoma.

Acute Disease↗
PubMed1996

Trabeculectomy--success rates in a Singapore hospital.

Previously published papers on the success of trabeculectomy as a treatment for glaucoma show success rates between 67% and 84%. The success rate of trabeculectomy in Afro-Carribean patients was observed to be lower than in Caucasian patients. It has been commonly believed that the success rate of trabeculectomy in Oriental/Asian eyes would lie somewhere between these. We reviewed the records of 51 consecutive trabeculectomies performed in the National University Hospital, Singapore and found that our success rate was lower-43.1% overall and 48.7% for primary glaucomas.

Adult↗
PubMed1995

Argon laser iridoplasty in chronic angle closure glaucoma.

This study evaluated the effect of argon laser iridoplasty (ALI) on 11 eyes with primary chronic angle closure glaucoma (CACG). All eyes had an intraocular pressure greater than 20 mmHg despite maximum medical therapy and were followed up for six months after ALI. Iridoplasty successfully opened at least half of the angle in all eyes, maximally reducing the intraocular pressure (IOP) in all eyes in the first week (paired t test p < 0.002). At three months, the IOP in 7 eyes were medically controlled while 4 eyes required trabeculectomy. The results at six months showed no further changes. Iridoplasty may be useful for lowering IOP in CACG and avoiding the need for surgery for up to six months in 64% of the eyes studied.

Chronic Disease↗
PubMed1994

Vascular changes over trabeculectomy blebs.

Low-dose anterior segment fluorescein angiography was performed on 10 eyes before and after trabeculectomy with a limbal-based conjunctival flap. Post-trabeculectomy angiography shows that all successful trabeculectomies have an area of decreased capillary vascular perfusion over the bleb site not coincidental with the area of the bleb and that there is delayed filling of vessels running over the bleb.

Capillaries↗