Biomedical subjects

S K Seah

Publications and source records attributed to S K Seah.

At least 19 recordsLinked to original sources

PubMed2002

Biometric gonioscopy and the effects of age, race, and sex on the anterior chamber angle.

AIM: To utilise a novel method for making measurements in the anterior chamber in order to compare the anterior chamber angles of people of European, African, and east Asian descent aged 40 years and over. METHODS: A cross sectional study on 15 people of each sex from each decade from the 40s to the 70s, from each of three racial groups-black, white, and Chinese Singaporeans. Biometric gonioscopy (BG) utilises a slit lamp mounted reticule to make measurements from the apparent iris insertion to Schwalbe's line through a Goldmann one mirror goniolens. The main outcome measures were BG measurements of the anterior chamber angle as detailed above. RESULTS: There was no significant difference in angle measurement between black, white, and Chinese races in this study. However, at younger ages people of Chinese race appeared to have deeper angles than white or black people, whereas the angles of older Chinese were significantly narrower (p = 0.004 for the difference in slope of BG by age between Chinese and both black and white people). CONCLUSION: The failure to detect a difference in angle measurements between these groups was surprising, given the much higher prevalence of angle closure among Chinese. It appears that the overall apparent similarity of BG means between Chinese and Western populations may mask very different trends with age. The apparently more rapid decline in angle width measurements with age among Chinese may be due to the higher prevalence of cataract or "creeping angle closure." However, longitudinal inferences from cross sectional data are problematic, and this may represent a cohort phenomenon caused by the increasing prevalence of myopia in the younger Singaporean population.

Adult↗

PubMed2001

The prevalence and risk factors for pterygium in an adult Chinese population in Singapore: the Tanjong Pagar survey.

PURPOSE: To determine the prevalence and risk factors for pterygium in the Chinese population of Singapore. METHODS: A population-based survey was conducted in Singapore, an island located 1 degree north of the equator with a stable tropical climate. A disproportionate, stratified, clustered, random sampling procedure was used to select the names of 2000 Chinese people aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district of Singapore. Selected subjects underwent a comprehensive interview and ocular examination. Pterygium was diagnosed and graded clinically as grade 1 (transparent), 2 (intermediate), and 3 (opaque). Risks factors associated with pterygium and grade 3 pterygium were evaluated with logistic regression models. RESULTS: From a total of 1717 eligible subjects, 1232 (71.8%) were examined. There were 120 people with either unilateral (n = 70) or bilateral (n = 50) pterygium, equivalent to an overall prevalence of 6.9% (95% confidence interval [CI], 5.2, 8.8) in the Chinese population aged 40 and older. The prevalence increased linearly with age (chi-square test of trend P <.001) and was higher among men than women (age-adjusted odds ratio [OR], 4.2; 95% CI, 2.5, 6.9). Men aged 70 and above had the highest overall prevalence of 25.4% (95% CI, 18.2, 19.4), but pterygium was not seen in women aged 40 to -49 years. In multivariate analysis, ptergyium was independently associated with increasing age (OR, 7.8; 95% CI, 3.2, 18.8 for persons 70 to 81 years, compared with 40 to 49 years), male sex (OR, 5.1; 95% CI, 2.9, 9.3) and certain occupations; factory workers, production workers and machine operators (OR, 3.1; 95% CI, 1.5, 6.3), as well as laborers and agricultural workers (OR, 3.3; 95% CI, 1.6, 7.0) had higher risks, compared with professionals and office workers. Grade 3 pterygium (n = 36) was also independently associated with male sex (OR, 11.6; 95% CI, 3.5, 38.6) and similar occupations but was not related to age. CONCLUSIONS: The prevalence of pterygium in Singapore is 7% among Chinese aged 40 years and older. Independent associations with increasing age, male sex, and occupations linked to outdoor work and other exposures suggest a multifactorial cause of this condition.

Adult↗

PubMed2001

Automated static perimetry: the influence of myopia and its method of correction.

OBJECTIVE: To determine how the magnitude of myopia and its method of correction influence visual field testing. DESIGN: Prospective observational case series, including comparison of spectacles and contact lenses. PARTICIPANTS: One hundred forty-six ophthalmologically normal males 19 to 24 years of age with myopia (spherical equivalent from -0.50 to -14.0 diopters). METHODS: Participants performed automated static threshold perimetry. Refractive errors were corrected using trial lenses and soft contact lenses. Subjects were tested with both methods of correction, the order of which was randomized. MAIN OUTCOME MEASURES: Threshold sensitivity and global indexes. RESULTS: Only one subject (0.7%) had a significant reproducible visual field defect on both methods of correction. Six subjects (4.1%) had a focal visual field defect on one method of correction but not the other. For myopia greater than -4.0 diopters, the mean defect decreased significantly as axial length and degree of myopia increased (P: < 0.01). Similar results were obtained with either method of correction. CONCLUSIONS: Threshold sensitivity is reduced in moderate and high myopia, regardless of the method of correction. The surprisingly low prevalence of visual field defects in this myopic population disputes the widely held view that myopia is associated commonly with visual field abnormalities. If field defects are found in myopes on automated perimetry, it is advisable to repeat the test with another method of optical correction to check that such defects are genuine and not related to the method of refractive correction.

Adult↗

PubMed2001

Variations in ocular biometry in an adult Chinese population in Singapore: the Tanjong Pagar Survey.

PURPOSE: To describe the variation in ocular biometry in adult Chinese individuals in Singapore. METHODS: This study was a population-based, cross-sectional survey of adult Chinese persons aged 40 to 81 years residing in Tanjong Pagar district, Singapore. Axial ocular dimensions, including axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) were measured using an A-scan ultrasound device. Corneal curvature (CC) and noncycloplegic refraction were measured with an autorefractor, with refraction further refined subjectively. Lens nuclear opacity (NO) was graded clinically using the modified Lens Opacity Classification System III (LOCS III) score. RESULTS: A total of 1717 subjects were eligible for the survey, of whom 1232 (71.8%) participated. Biometric and refraction data were available for 1004 (58.5%) phakic subjects. The AL, ACD, LT, VCD, CC, and LOCS III scores were 23.23 +/- 1.17 mm, 2.90 +/- 0.44 mm, 4.75 +/- 0.47 mm, 15.58 +/- 1.11 mm, 7.65 +/- 0.27 mm, and 3.2 +/- 0.9 (mean +/- SD), respectively. On average, people aged 40 to 49 years, when compared with those 70 to 81 years, had longer ALs (mean difference, +0.58 mm), deeper ACDs (+0.52 mm), longer VCDs (+0.72 mm), but thinner lenses (-0.70 mm) and less severe NO (-1.7 LOCS III score). CCs did not vary significantly with age. After controlling for age, women had shorter ALs and VCDs, shallower ACDs, but thicker lenses and steeper CCs than men. The variation in noncycloplegic refraction with age was nonlinear. Among people aged 40 to 59 years, a higher prevalence of hyperopia was seen in older compared with younger persons (on average, a difference of +1.3 D for every 10-year difference in age, P: < 0.001), explained principally by shorter AL (and VCD) in older persons. Among those 60 to 81 years, this pattern was not obvious (a difference of -0.03 D for every 10-year difference in age, P: = 0.12), as NO became an additional determinant of refraction, with greater degrees of NO in older person's driving refraction in the "minus" direction. CONCLUSIONS: Ocular dimensions vary with age and gender in adult Chinese persons in Singapore. The variation in noncycloplegic refraction in people 40 years and older may be explained by differences in axial lengths (principally vitreous chamber depths) between older and younger persons and, from 60 years onwards, differences in lens nuclear opacification as well.

Adult↗

PubMed2001

The relationship between ocular dimensions and refraction with adult stature: the Tanjong Pagar Survey.

PURPOSE: To describe the association of ocular dimensions and refraction with adult stature. METHODS: This was a population-based cross-sectional survey of adult Chinese aged 40 to 81 years residing in the Tanjong Pagar district in SINGAPORE: As part of the examination, ocular dimensions, including axial length, anterior chamber depth, lens thickness, and vitreous chamber depth, were measured using an A-mode ultrasound device. Corneal radius and refraction were determined with an autorefractor, with refraction further refined subjectively. Height (in meters) and weight (in kilograms) were measured using a standardized protocol, and body mass index (BMI) was calculated as weight divided by the square of the height (kilograms per square meter). RESULTS: Data on ocular biometry, refraction, height, and weight were available on 951 (55.4%) participants with phakic eyes. After controlling for age, sex, education, occupation, housing type, income, and weight, it was found that taller persons were more likely to have longer axial lengths (+0.23 mm longer axial length, for every 0.10 m difference in height), deeper anterior chambers (+0.07 mm), thinner lenses (-0.09 mm), longer vitreous chambers (+0.26 mm), and flatter corneas (+0.09 mm longer corneal radius), although refractions were similar. In contrast, heavier persons tended to have more hyperopic refractions (+0.22 D for every 10 kg difference in weight, +0.56 D for every 10 kg/m(2) difference in BMI) but similar ocular dimensions. CONCLUSIONS: Adult height is independently related to ocular dimensions, but does not appear to influence refraction. Thus, although taller persons are more likely to have longer globes, they also tend to have deeper anterior chambers, thinner lenses, and flatter corneas. Conversely, weight is independently related to refraction, although the exact biometric component responsible for this association is not apparent.

Adult↗

PubMed2000

The prevalence of glaucoma in Chinese residents of Singapore: a cross-sectional population survey of the Tanjong Pagar district.

BACKGROUND: Data on prevalence of glaucoma in East Asia are scarce. OBJECTIVE: To determine the prevalence and clinical characteristics of glaucoma in adult Chinese Singaporeans. METHODS: A group of 2000 Chinese people, aged 40 to 79 years, were selected from the electoral register of Tanjong Pagar district in Singapore using a disproportionate, stratified, clustered, random-sampling procedure. Glaucoma was diagnosed in people with an excavated optic neuropathy and a reproducible visual field defect or on the basis of severe structural disc abnormality alone, if reliable field results could not be obtained. The diagnosis was also made in blind subjects with raised intraocular pressure or previous glaucoma surgery. RESULTS: Of 1717 eligible subjects, 1232 were examined, with a response rate of 71.8%. There were 45 cases of glaucoma: 27 were men and 18 were women. The main diagnoses were primary open-angle glaucoma (n = 22 [49%]), primary angle-closure glaucoma (n = 14 [31%]), and secondary glaucoma (n = 7 [16%]). It was not possible to determine the mechanism in 2 (4%). CONCLUSIONS: The age-standardized prevalence of glaucoma was 3.2% (95% confidence interval, 2.3-4.1) in the population 40 years and older. Glaucoma was the leading cause of blindness. Primary angle-closure glaucoma and secondary glaucoma were the most visually destructive forms of the disease. Our findings suggest current projections of glaucoma prevalence among ethnic Chinese are a substantial underestimate. Arch Ophthalmol. 2000;118:1105-1111

Adult↗

PubMed2000

Trabeculectomy for acute primary angle closure.

OBJECTIVE: To analyze the results of trabeculectomy performed for all cases of acute primary angle closure (APAC). DESIGN: Retrospective, noncomparative case series PARTICIPANTS: Fifty-six consecutive patients who underwent trabeculectomy for APAC at two Singapore centers from 1993 through 1995. METHODS: The conventional treatment for APAC is to lower intraocular pressure (IOP) medically, after which laser peripheral iridotomy (PI) is performed. However, in Asian eyes, the acute attack is often refractory to standard treatment. Trabeculectomy is occasionally performed on eyes that do not respond to medical therapy, as well as eyes with APAC that respond to medical therapy but are assessed as having underlying chronic angle-closure glaucoma. In such cases, laser PI is not performed before trabeculectomy. MAIN OUTCOME MEASURES: The surgical outcome was assessed in terms of final IOP and the incidence of complications. Success was defined as final IOP less than 21 mmHg without medication, and qualified success was defined as final IOP less than 21 mmHg with medication. Patients whose IOP was more than 21 mmHg, required further glaucoma surgery, lost light perception, or whose eye became phthisical were classified as failures. RESULTS: The mean follow up was 22 months (range, 6-42 months). In group A, the medical failure group (n = 32), success in IOP control was obtained in 18 patients (56.2%), qualified success was achieved in 3 patients (9.4%), and failure resulted in 11 patients (34.4%). Ten patients (31.3%) encountered early postoperative complications such as shallow anterior chamber. In group B, the medical success group (n = 24), success in IOP control was achieved in 21 patients (87.5%), qualified success was achieved in 3 patients (12.5%), and there were no cases of failure. The incidence of postoperative complications was low (4 eyes [16.7%]). In terms of IOP outcome, trabeculectomy outcome was significantly worse in group A (P<0.001, Fisher's exact test). CONCLUSIONS: Because there is a high risk of surgical failure and complications, trabeculectomy may not be the procedure of choice in medically unresponsive cases of APAC.

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↗

PubMed2000

Prevalence and risk factors for refractive errors in adult Chinese in Singapore.

PURPOSE: To determine the epidemiology of refractive errors in an adult Chinese population in Singapore. METHODS: A disproportionate, stratified, clustered, random-sampling procedure was used to select names of 2000 Chinese people aged 40 to 79 years from the 1996 Singapore electoral register in the Tanjong Pagar district in Singapore. These people were invited to a centralized clinic for a comprehensive eye examination, including refraction. Refraction was also performed on nonrespondents in their homes. Myopia, high myopia, and hyperopia were defined as a spherical equivalent (SE) in the right eye of less than -0.5 D, less than -5.0 D, and more than +0.5 D, respectively. Astigmatism was defined as less than -0.5 D of cylinder. Anisometropia was defined as a difference in SE of more than 1.0 D between the two eyes. Only phakic eyes were analyzed. RESULTS: From 1717 eligible people, 1232 (71.8%) were examined. Adjusted to the 1997 Singapore population, the overall prevalence of myopia, hyperopia, astigmatism, and anisometropia was 38.7% (95% confidence interval [CI]: 35.5, 42.1), 28.4% (95% CI: 25.3, 31.3), 37.8% (95% CI: 34.6, 41.1), and 15.9% (95% CI: 13.5, 18.4), respectively. The prevalence of high myopia was 9.1% (95% CI: 7.2, 11.2), with women having significantly higher rates than men. The age pattern of myopia was bimodal, with higher prevalence in the 40 to 49 and 70 to 81 age groups and lower prevalence between those age ranges. Prevalence was reversed in hyperopia, with a higher prevalence in subjects aged 50 to 69. There was a monotonic increase in prevalence with age for both astigmatism and anisometropia. Increasing educational levels, higher individual income, professional or office-related occupations, better housing, and greater severity of nuclear opacity were all significantly associated with higher rates of myopia, after adjustment for age and sex. CONCLUSIONS: The results indicate that whereas myopia is 1.5 to 2.5 times more prevalent in adult Chinese residing in Singapore than in similarly aged European-derived populations in the United States and Australia, the sociodemographic associations are similar.

Adult↗

PubMed1999

Augmentation of filtering blebs with perfluoropropane gas bubble: an experimental and pilot clinical study.

OBJECTIVE: To evaluate the use of perfluoropropane (C3F8) gas bubble in the augmentation of glaucoma-filtering blebs. DESIGN: Experimental animal study and a pilot clinical study. PARTICIPANTS: Twenty rabbits in the animal study and 20 humans in the pilot study participated. INTERVENTION: Twenty patients underwent trabeculectomy for medically uncontrolled glaucoma. Surgical techniques were similar to those used in standard limbus-based trabeculectomies. The Tenon's capsule and conjunctival wound were closed separately using continuous sutures. Before the final knots were tied, 0.1 to 0.2 ml of 15%:85%-C3F8:air mixture gas bubble was introduced into the subconjunctival space with a silicone tube attached to a 27-gauge Rycrof cannula. The sutures were immediately knotted on withdrawal of the tube. The patients were reviewed after surgery for the appearance, size, and location of the gas bubble. The bleb morphology and intraocular pressures were also monitored. MAIN OUTCOME MEASURES: The parameters measured were intraocular pressure control, Snellen visual acuity, appearance of the bleb in relation to its elevation and degree of inflammation of the subconjunctival tissue, and characteristics of the gas bubble (e.g., size, number, and position). RESULTS: The gas bubbles stayed in the conjunctival bleb for an average duration of 17 days (range, 13-27 days). In all cases, the gas bubbles helped to maintain the filtering bleb until their complete resolution. No excessive inflammation was noted in the filtering blebs. The mean preoperative intraocular pressure was 27.3 +/- 5.5 millimeters of mercury (mmHg), and the mean postoperative intraocular pressure was 14.5 +/- 2.3 mmHg, with only two patients requiring supplementary topical medication. All cases resulted in good filtering blebs with satisfactory intraocular pressures after 16 months of follow-up. CONCLUSIONS: Subconjunctival C3F8 gas bubbles, via a "spacer" effect, aid the maintenance of filtering blebs in the early postoperative period. This technique may be useful in augmenting or salvaging blebs at risk of failure.

Adult↗

PubMed1998

Glaucoma drainage implants in Asian eyes.

OBJECTIVE: Previous studies have suggested that there are racial differences in the outcome of conventional filtration surgery. This study aims to evaluate the outcome of glaucoma drainage implants in Asian eyes with complicated glaucoma and to determine whether there are racial differences in the results of such implant surgery compared to previous reports in non-Asian patients. DESIGN: The study design was a retrospective review of all patients with more than 6-months' follow-up after glaucoma implant surgery at the Singapore National Eye Centre between January 1993 and August 1996. PARTICIPANTS: A total of 83 Asian patients with uncontrolled complicated glaucoma participated. INTERVENTION: A total of 29 patients received Molteno implants and 54 received Baerveldt implants. MAIN OUTCOME MEASURES: The surgical outcome was assessed in terms of final intraocular pressure (IOP), visual acuity outcome, and incidence of complications. Success was defined as final IOP less than 22 mmHg with no medications and qualified success as an IOP less than 22 mmHg with medication. RESULTS: With mean follow-up of 13.41 months, success in IOP control was achieved in 73.5% of patients and qualified success in 12%. Visual acuity remained stable or improved in 85.5%. There were no patients who encountered intraoperative complications, and the incidence of serious postoperative complications was low. The most frequently observed short- and long-term postoperative complication was hyphema in 14 eyes (16.9%) and bullous keratopathy in 7 eyes (8.4%), respectively. CONCLUSIONS: Glaucoma drainage implants have good outcome and visual stabilization in Asian eyes with success rates for IOP control comparable to those reported in previous studies in non-Asian eyes.

Adolescent↗

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↗

PubMed1996

Comparison of argon laser iridotomy and sequential argon laser and Nd:YAG laser iridotomy in dark irides.

BACKGROUND AND OBJECTIVE: A prospective study was performed to compare argon laser iridotomy and sequential argon laser and Nd:YAG laser iridotomy in dark irides. PATIENTS AND METHODS: Twenty-four eyes of 17 patients underwent laser iridotomies; 13 underwent argon laser iridotomies and 11 underwent sequential argon laser and Nd:YAG laser iridotomies. The argon laser settings were standardized at 1.2 W, 50-mum spot size, and 0.1-second duration. The Nd:YAG laser was set at 2.5 mJ and single-pulse shots were used. RESULTS: All of the iridotomies were patent at the end of one treatment session. The mean total energy used for argon laser iridotomy was 8.28 J. For sequential iridotomy, 3.12 J was used for the argon laser stage and 7.5 mJ for the Nd:YAG laser stage. CONCLUSION: The total argon laser energy used can be reduced by 2.65 times by using the sequential laser iridotomy technique.

Aged↗

PubMed1996

Cataract surgery after trabeculectomy.

BACKGROUND AND OBJECTIVE: To determine the effect of cataract surgery on glaucomatous eyes with good intraocular pressure (IOP) control after trabeculectomy. PATIENTS AND METHODS: Twenty-two eyes with functional blebs that underwent cataract extraction were retrospectively analyzed. RESULTS: The mean (+/- SD) preoperative IOP was 11.0 +/- 4.3 mm Hg. The mean (+/- SD) postoperative IOPs at 1, 2, 6, and 9 months were 15.5 +/- 4.9, 12.6 +/- 4.7, 14.6 +/- 5.6, and 19.0 +/- 7.9 mm Hg, respectively. At each interval except for the second month, the mean IOP was statistically significantly higher than the preoperative value (P = .0003, .24, .02, and .0009, respectively). The total number of medications was also higher (3 preoperatively versus 27 postoperatively). The interval between the two surgeries had no influence on IOP control. Intraoperative complications during cataract surgery, particularly vitreous loss, were associated with poor IOP control. Phacoemulsification had less of an effect on the postoperative IOP control than did extracapsular cataract extraction. CONCLUSIONS: Eyes with previous successful trabeculectomies had higher IOPs and required more medications after subsequent cataract surgeries.

Aged↗

PubMed1994

Contact transscleral cyclophotocoagulation for end stage glaucoma.

Contact transscleral cyclophotocoagulation is a form of cyclodestructive procedure, which is effective in the lowering of intraocular pressure in eyes with refractory glaucoma by destroying the aqueous humor-producing ciliary processes. Continuous wave Nd:YAG (Neodymium: Yttrium-Aluminium-Garnet) laser is used in the cyclodestruction, the laser energy being delivered to the target tissues transsclerally via a fibre-optic probe. We used the Lasag microruptor III Nd:YAG laser to treat 16 cases of refractory glaucoma to evaluate the effectiveness of laser in pain relief and intraocular pressure control. The mean preoperative intraocular pressure of 48.3 +/- 9.3 mm Hg decreased to 30.6 +/- 17.4 mm Hg (p = 0.0001) during an average follow-up of 294.2 +/- 94.2 days (range, 181-465 days). Retreatment was required in eight of 16 eyes (50%). Four eyes (27%) had decreased vision from perception of light to no perception of light. None of the 15 patients developed phthisis bulbi or other serious complications. We conclude that transscleral cyclophotocoagulation is an effective modality of therapy for refractory and end stage glaucoma. The lower than recommended total energy we used in the treatment protocol was associated with lower incidence of complications but also lower success rate and higher retreatment rate.

Adult↗

PubMed1993

Determination of mitomycin C in human aqueous humor and serum by high-performance liquid chromatography.

Mitomycin C (MMC) is used in the treatment of disseminated adenocarcinoma of the stomach and pancreas and is used in ophthalmology as adjunctive therapy in trabeculectomy. Since only small volumes of aqueous humor are available for analysis, a sensitive method requiring limited sample preparation was developed. An internal standard, 4-aminoacetophenone, was added to aqueous humor specimens, and the solution was directly injected into the high-performance liquid chromatographic (HPLC) column. The use of a short 50-mm C18 reversed-phase column gave adequate resolution of peaks with improved sensitivity. The method was applicable for determination of MMC in serum, although solid-phase extraction for sample clean-up was required prior to injection into the HPLC column, and analytical columns of 150-250 mm were necessary for adequate resolution of peaks. The method has been validated and is linear from 6.25 to 50 ng/ml in aqueous humor and from 10 to 500 ng/ml in serum.

Acetophenones↗

PubMed1993

Mitomycin-C concentration in human aqueous humour following trabeculectomy.

The aim of the study was to determine mitomycin-C (MMC) concentrations in human aqueous humour during trabeculectomy and to correlate anterior chamber concentrations with method of application. MMC was applied intra-operatively by saturating sponges, ranging in size from 2 x 2 x 5 mm to 2 x 4 x 10 mm on dry cut, with 0.5 mg/ml MMC during trabeculectomy for 3-5 minutes. Applications to episclera were made in 18 cases and to the scleral bed after scleral flap dissection in 9 cases. Aqueous samples were collected by paracentesis with a 30 gauge needle 2-7 minutes after removal of sponge and external irrigation. Aqueous MMC concentrations were determined by high-performance liquid chromatography. Aqueous MMC concentration in 27 samples ranged from below minimum detectable concentration (less than 5 ng/ml) to 120.8 ng/ml. Mean aqueous drug levels obtained when the applications were to the scleral bed were 35.65 +/- 39.17 ng/ml (range 5-120.8 ng/ml). Applications on episclera gave mean aqueous concentrations of 4.98 +/- 9.11 ng/ml (range 0-33.3 ng/ml). The difference was statistically significant (p = 0.004). There were no correlations between sponge size, time of MMC exposure and aqueous MMC level. In conclusion, MMC is detectable in aqueous humour within minutes of external application and the aqueous concentration level is higher if the application is in the scleral bed than on the episclera. Toxicity of the drug at this concentration range for corneal endothelial cells needs further investigation via in vitro and clinical studies.

Adolescent↗

PubMed1979

Experimental Trypanosoma cruzi infection in rhesus monkeys 111. Electrocardiographic and histopathological findings.

In five rhesus monkeys surviving 'Peru strain' or 'strain 7' Trypanosoma cruzi infection for six to eight years, positive xenodiagnosis results and high indirect fluorescent antibody titres (4096 - 65536) persisted until the animals were killed. Abnormal electrocardiograph patterns in two monkeys (H and K) were possibly compatible with myocardial damage. Histopathological changes attributable to T. cruzi infection were minor in four monkeys but severe in one (R). In this animal, infected with what was judged previously to be the less virulent of the two T. cruzi stocks used ('strain 7'), there was severe myocarditis, with myofibre degeneration, and lesions of the oesophagus. Elevated serum levels of five enzymes were not detected in any of the chronically infected monkeys.

Animals↗