A randomised crossover study comparing bimatoprost and latanoprost in subjects with primary angle closure glaucoma.

BACKGROUND/AIMS: To compare the intraocular pressure (IOP) lowering efficacy and side effects of latanoprost 0.005% and bimatoprost 0.03% in subjects with chronic primary angle closure glaucoma (PACG). METHODS: This was an observer-masked randomised crossover study of 60 PACG subjects who received either latanoprost or bimatoprost for 6 weeks, after which they were crossed over to the other medication for another 6 weeks. The IOP-reducing effect of the medications was assessed by the reduction in IOP after 6 weeks of treatment compared with baseline. RESULTS: Fifty-four subjects (80 eyes) completed the study. Latanoprost reduced IOP (mean (SD)) by 8.4 (3.8) mm Hg and bimatoprost by 8.9 (3.9) mm Hg from a baseline of 25.2 (3.6) mm Hg and 25.2 (3.6) mm Hg respectively (p = 0.23). Adverse events were mild in both groups; however there were twice as many reports of an adverse event in the bimatoprost group (81%) compared with the latanoprost group (40%, p<0.01). Ocular irritation was the most frequently reported adverse event in both groups; 22 subjects (37.9%) treated with bimatoprost experienced ocular hyperaemia as compared with 13 subjects (22.4%) treated with latanoprost (p = 0.11). CONCLUSIONS: Bimatoprost once daily was similarly effective in reducing IOP compared with latanoprost once daily in subjects with chronic PACG. Both drugs were well tolerated with mild ocular adverse events.

Visual acuity after acute primary angle closure and considerations for primary lens extraction.

BACKGROUND/AIM: Primary lens extraction has been advocated for acute primary angle closure (APAC), but it is not known if this is warranted in all cases. The aim of this study was to investigate the visual acuity (VA) of APAC eyes shortly after resolution of the acute episode in order to assess the appropriateness of performing such surgery in this condition. METHODS: This was a prospective observational case series. As part of a randomised controlled trial comparing phacoemulsification and laser iridotomy, 135 consecutive APAC subjects over a 2 year period underwent subjective refraction and measurement of Snellen VA once the acute episode had resolved with reduction of intraocular pressure (IOP) and improved corneal clarity. RESULTS: Subjects were predominantly Chinese (95.6%) and female (79.3%), with a mean age of 63.6 (SD 9.6) years. When assessed 1.7 (2.7) days after presentation, the majority of APAC cases (50.4%) had good VA (6/12 or better), with more than a quarter of cases having VA of 6/7.5 or better. Poor VA was associated with duration of symptoms (p = 0.04, OR = 4.1, 95% CI 1.1 to 15.7) and time taken to resolution of APAC (p = 0.04, OR = 2.2, 95% CI 1.02 to 4.6), but not with sex (p = 0.31), age (p = 0.26), duration from presentation to measurement of visual acuity (p = 0.53), or presenting IOP (p = 0.73). CONCLUSION: Within days after APAC, more than half of APAC affected eyes had good VA (6/12 or better). The role of lens extraction in the management of APAC warrants further debate, especially for eyes with good VA.

Interocular asymmetry of visual field defects in primary open angle glaucoma and primary angle-closure glaucoma.

AIM: To compare the interocular asymmetry in visual field loss of patients with primary open-angle (POAG) and primary angle-closure glaucoma (PACG). METHODS: Subjects entering a prospective, randomised, controlled trial of intraoperative 5-fluorouracil in glaucoma surgery in Singapore were included. Preoperative visual field testing was performed using automated white-on-white perimetry (24-2 test pattern, threshold program, Mk II, Model 750, Zeiss-Humphrey, San Leandro, CA, USA). A minimum of two tests were required with mean deviation within 2 dB on two tests, fixation losses <20%, false positives <33%, and false negatives <33%. The second field was scored using AGIS II criteria and the 'mean asymmetry score' defined as the mean difference between eyes for both AGIS scores and global indices. RESULTS: In 230 subjects assessed (128 POAG, 102 PACG), mean interocular asymmetry of visual field loss was greater for the PACG group. The mean AGIS asymmetry scores for total (PACG=9.21+/-6.87 vs POAG=6.48+/-5.58, P=0.001), superior (PACG=4.31+/-3.39 vs POAG=3.35+/-3.13, P=0.035), and inferior (PACG=4.43+/-3.31 vs POAG=2.64+/-2.77, P<0.0001) areas and mean deviation (MD) asymmetry scores (PACG=6.89+/-13.22 vs POAG=1.66+/-16.97, P=0.012) were all significantly different. Interocular correlation of visual field loss for POAG was significant; total AGIS, r=0.27 (P=0.003), superior field AGIS, r=0.24 (P=0.008), inferior field AGIS, r=0.34 (P=0.0001), and MD, r=0.27 (P=0.003). In PACG, there was no significant correlation between eyes; total AGIS, r=-0.02 (P=0.85), superior field AGIS, r=-0.02 (P=0.82), inferior field AGIS, r=-0.17 (P=0.87), and MD, r=0.015 (P=0.89). CONCLUSION: There was a greater asymmetry of visual field loss between eyes, as measured by AGIS scores and MD, in PACG than that in POAG.

Effect of cataract extraction and intraocular lens implantation on nerve fibre layer thickness measurements by scanning laser polarimeter (GDx) in glaucoma patients.

PURPOSE: To assess the influence of visually significant cataract on the measurement of nerve fibre layer thickness by scanning laser polarimetry (GDx) in glaucoma patients undergoing phacoemulsification cataract extraction. METHOD AND SUBJECTS: All subjects with primary glaucoma participating in a prospective trial of glaucoma surgery who subsequently underwent cataract extraction were eligible. A single trained observer using the GDx nerve fibre layer analyser (LDT) performed pre- and post-operative measurements of nerve fibre layer thickness (NFLT). NFLT parameters, best-corrected LogMAR visual acuity, and automated visual fields were assessed before and after phacoemulsification cataract extraction with implantation of an acrylic intraocular lens. RESULTS: A total of 49 subjects were assessed: 22 (45%) had POAG and 29 (55%) PACG; all were Asian (36 (73%) were Chinese), with mean age 67.1 (+/-7.6 SD) and mean 'LOCS III' lens opacity grading 11.4 (+/-3.1 SD). Visual acuity significantly improved (mean LogMAR 0.5 vs 0.15, P<0.0001). Corrected pattern standard deviation (6.1 vs 6.4, P=0.2) and mean deviation (-17.7 dB vs -17.0 P=0.91) were little changed after cataract removal. Pseudo-phakic measurements of NFLT were significantly different from pre-op values. Measures of absolute thickness (including the average thickness, ellipse, ellipse average, superior and inferior averages, superior integral) were significantly greater than preoperative values (all P<0.01), whereas ratios and measures of symmetry (symmetry, superior/nasal) were unchanged (all P>0.1) and 'the number' was smaller (P=0.04). Differences in measured NFLT were most strongly correlated with posterior subcapsular cataract (average thickness, P=0.01). CONCLUSIONS: Removal of cataract resulted in greater absolute measurements of NFLT but ratio values were unchanged. Scanning laser polarimetry measurements can change significantly after cataract extraction. New baseline measurements may be required.

Randomised controlled trial comparing the effect of brimonidine and timolol on visual field loss after acute primary angle closure.

AIM: To compare the effect of brimonidine and timolol in reducing visual field loss in patients with acute primary angle closure (APAC). METHODS: In addition to standard acute medical treatment, patients presenting with APAC were randomised to either brimonidine 0.2% or timolol 0.5% upon diagnosis, then twice daily for 4 weeks. After laser peripheral iridotomy (LPI), subjects underwent three baseline perimetry tests during the first week, and then at weeks 4, 8, 12, and 16. Pointwise linear regression analysis was applied to the field series of each of these subjects starting with the third test (total of five tests per subject). Progression was defined as a significant regression slope (p<0.05) showing 1 dB per year or more of sensitivity loss at the same test location in the series. Patients were also compared for prevalence of abnormal fields at 16 weeks, which was defined as an abnormal glaucoma hemifield test result and/or corrected pattern standard deviation outside the 95% confidence limits. RESULTS: 59 subjects (31 in the brimonidine group; 28 in the timolol group) completed the study. There were 47 females (79.7%), the majority of subjects (94.9%) were Chinese and the mean age was 59.2 (SD 7.2) years. There were no significant differences between the two groups with respect to demographic features, presenting intraocular pressure (IOP), duration of symptoms, time from presentation to LPI, or mean IOP at each study visit. Over the 16 week study period, despite adequate statistical power, no difference was found between groups in terms of the number of patients with progressing locations, the mean number of progressing locations per subject, or the mean slope of the progressing locations. Nine (29%) subjects in the brimonidine group and 10 (35.7%) in the timolol group were found to have significant visual field defects at 16 weeks (p = 0.58). 15 out of these 19 subjects (78.9%) already had these visual field defects in the first week. CONCLUSIONS: In the first 16 weeks after APAC, there was no difference in the prevalence of visual field defects or rate of visual field progression between brimonidine and timolol treated groups.

Intraocular pressure and visual field loss in primary angle closure and primary open angle glaucomas.

AIM: To compare the correlation between visual field loss and the pretreatment intraocular pressure (IOP) in primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG). METHODS: In a cross sectional observational study of 74 patients (43 PACG, 31 POAG), pretreatment IOP was measured at presentation, before treatment was initiated. The severity of visual field loss was assessed by AGIS score, mean deviation (MD), pattern standard deviation (PSD), and corrected pattern standard deviation (CPSD). Glaucomatous optic neuropathy was assessed from simultaneous stereo disc photographs. RESULTS: There was a stronger correlation between pretreatment IOP and the extent of visual field loss in PACG subjects than in those with POAG for both MD (PACG: Pearson correlation coefficient (r) = 0.43, p = 0.002; r(2) = 0.19), (POAG: r = 0.21, p = 0.13; r(2) = 0.04) and AGIS score (PACG: r = 0.41, p = 0.003; r(2) = 0.17), (POAG: r = 0.23, p = 0.19; r(2) = 0.05 respectively). No such associations were seen for pattern standard deviation (PSD) or corrected pattern standard deviation (CPSD) in either group (p> 0.29). Both horizontal and vertical cup-disc ratio were well correlated with severity of field loss but not with presenting IOP for either diagnosis. CONCLUSIONS: This is consistent with the hypothesis of a greater IOP dependence for optic nerve damage in PACG than POAG and, conversely, a greater importance of other, less pressure dependent mechanisms in POAG compared to PACG.

Combined phacoemulsification, intraocular lens implantation and trabeculectomy for chronic angle closure glaucoma.

PURPOSE: To investigate the results of combined phacoemulsification, intraocular lens implantation and trabeculectomy in Asian patients with chronic angle closure glaucoma (CACG). METHODS: This was a retrospective non-comparative case series of 55 consecutive patients (57 eyes) who underwent phacoemulsification, posterior chamber intraocular lens implantation and trabeculectomy for CACG at the Singapore National Eye Centre between 1997-1998. The surgical outcome was assessed in terms of intraocular pressure (IOP), the incidence of complications and the visual acuity at last follow-up. Success was defined as final IOP < or = 21 mmHg without medication and qualified success as final IOP < or = 21 mmHg with medication. Patients with final IOP > 21 mmHg who required further glaucoma surgery, lost light perception or became pthisical, were classified as failures. The eyes were further categorized into two groups according to whether single-site or separate-site surgery was performed. The outcome was also compared among eyes in which per-operative antimetabolites were applied to the trabeculectomy site and those without antimetabolites. RESULTS: The mean follow up was 22.0 +/- 5.6 months (mean +/- SD). Success was achieved in 46 (81%) eyes, qualified success in 10 (17%) eyes, and failure in 1 (2%) eye. In terms of IOP outcome, the success rate was similar in the two surgical groups (single-site or separate-site). There was no significant difference in IOP outcome among eyes in which per-operative antimetabolites were used and eyes with no per-operative antimetabolites use. Forty-one eyes (72%) had 6/12 or better vision. There were no cases of intraoperative complications and the incidence of postoperative complications was low. CONCLUSIONS: Combined phacoemulsification, intraocular lens implantation and trabeculectomy is associated with good intraocular pressure control and visual outcome in patients with CACG.

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

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.

Effects of optical correction media on contrast sensitivity.

Contrast sensitivity functions (CSFs) were obtained for 257 emmetropic subjects (514 eyes) and 35 contact lens users (64 eyes) in the Republic of Singapore Air Force using the Vistech Contrast Test System. For the emmetropes, contrast sensitivity tests were carried out with and without plano spectacles (PS). For the myopes, we compared their performances with spectacles, daily-wear soft contact lenses (CLs), and CL plus PS at Snellen visual acuities of 6/6 or better. Paired t-tests showed that there were no significant differences (P > 0.05) when CSFs of the emmetropes were measured with and without PS and when that of the CL users were measured with spectacles, CL and CL plus PS. We therefore conclude that myopic optical correction media do not retard CSF significantly based on the Vistech charts, although they may reduce image size and modify light transmission by being imperfect transparencies. The observed decrease in CSF for myopes even after myopic correction might therefore be related to other factors associated with myopia, such as retinal changes or possibly mild amblyopia.

Orbital colour Doppler imaging in carotid-cavernous sinus fistula.

BACKGROUND: Colour Doppler imaging (CDI) is a recent advance in ultrasonography that allows for colour-encoded blood flow data of a vascular structure to be displayed simultaneously on a conventional real-time gray-scale B mode image. Real time A and B mode ultrasonography have been used for diagnostic evaluation of ophthalmic disorders since the early 1960s. The haemodynamic characteristics of the ophthalmic circulation have recently been studied by the use of CDI. METHOD: We present three cases of carotid-cavernous sinus fistulas with different presentations. In each case, orbital CDI was used in evaluating the patient's condition. RESULTS: Orbital CDI was successful in confirming the diagnosis in all three cases. CDI was capable of showing the haemodynamic changes in the orbital vasculature which resulted from carotid-cavernous sinus fistula. CONCLUSION: This non-invasive technique presents as an excellent alternative to invasive vascular studies such as angiography for the diagnosis and evaluation of carotid-cavernous sinus fistulas.

Contrast sensitivity in a large adult population.

The contrast sensitivity test (using Vistech charts) was performed on a consecutive sample of 1612 eyes of 807 Republic of Singapore Air Force personnel (two diseased eyes excluded), which had no known ophthalmic disorder. This yielded a large sample norm of spatial Contrast Sensitivity Function (CSF) distribution curves, based on the local population. Although all subjects had their refractive errors fully corrected by spectacles, whenever necessary, to visual acuity of 6/6 or better, myopes had lower mean contrast sensitivity, in the higher spatial frequencies, compared to the emmetropic. Postulates were offered to explain this association, including the concept of micro-amblyopia. Pilots and aircrew performed consistently better than the ground crew, suggesting that target acquisition training may improve contrast sensitivity. Interestingly, sex was also shown to be associated with differences in contrast sensitivity: females were found to have lower spatial contrast sensitivity compared to males. Age was associated with poorer contrast sensitivity only at the lower spatial frequencies in this study sample, while race, with that of higher frequencies; Chinese having lower contrast sensitivity than other races (a heterogeneous group consisting of Malays, Indians, Eurasians and Others). The association of contrast sensitivity with race highlights the importance of using normograms based on the local population. All the above associations were statistically significant at P = 0.05, and independent of each other, based on analysis by multiple regression.(ABSTRACT TRUNCATED AT 250 WORDS)