Joe G. Devereux

YAG laser iridotomy treatment for primary angle closure in east Asian eyes

AIM To assess the efficacy of Nd:YAG laser iridotomy as initial treatment for primary angle closure in a community setting in rural Mongolia. METHODS Subjects with occludable drainage angles in two glaucoma prevalence surveys in Mongolia (carried out in 1995 and 1997) were treated with YAG laser iridotomy at the time of diagnosis. These patients were re-examined in 1998. Patency of iridotomy, intraocular pressure (IOP), visual acuity, and gonioscopic findings were recorded. Iridotomy was classified unsuccessful in eyes where further surgical intervention was required or in which there was a loss of visual acuity to <3/60 from glaucomatous optic neuropathy. RESULTS 164 eyes of 98 subjects were examined. Patent peripheral iridotomies were found in 98.1% (157/160) of eyes that had not undergone surgery. Median angle width increased by two Shaffer grades following iridotomy. Iridotomy alone failed in 3% eyes with narrow drainage angles and either peripheral anterior synechiae or raised IOP, but normal optic discs and visual fields. However, in eyes with established glaucomatous optic neuropathy at diagnosis iridotomy failed in 47%. None of the eyes with occludable angles that were normal in all other respects, and underwent iridotomy, developed glaucomatous optic neuropathy or symptomatic angle closure within the follow up period. CONCLUSIONS Nd: YAG laser iridotomy is effective in widening the drainage angle and reducing elevated IOP in east Asian people with primary angle closure. This suggests that pupil block is a significant mechanism causing closure of the angle in this population. Once glaucomatous optic neuropathy associated with synechial angle closure has occurred, iridotomy alone is less effective at controlling IOP.

Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber depth in Asians: modified grading scheme

AIM To evaluate the performance of limbal chamber depth estimation as a means of detecting occludable drainage angles and primary angle closure, with or without glaucoma, in an east Asian population, and determine whether an augmented grading scheme would enhance test performance. METHOD A two phase, cross sectional, community based study was conducted on rural and urban areas of Hövsgöl and Ömnögobi provinces, Mongolia. 1800 subjects aged 40 to 93 years were selected and 1717 (95%) of these were examined. Depth of the anterior chamber at the temporal limbus was graded as a percentage fraction of peripheral corneal thickness. An “occludable” angle was one in which the trabecular meshwork was seen in less than 90° of the angle circumference by gonioscopy. Primary angle closure (PAC) was diagnosed in subjects with an occludable angle and either raised pressure or peripheral anterior synechiae. PAC with glaucoma (PACG) was diagnosed in cases with an occludable angle combined with glaucomatous optic neuropathy and consistent visual morbidity. RESULTS Occludable angles were identified in 140 subjects, 28 of these had PACG. The 15% grade (equivalent to the traditional “grade 1”) yielded sensitivity and specificity of 84% and 86% respectively for the detection of occludable angles. The 5% grade gave sensitivity of 91% and specificity of 93% for the detection of PACG. The interobserver agreement for this augmented grading scheme was good (weighted kappa 0.76). CONCLUSIONS The traditional limbal chamber depth grading scheme offers good performance for detecting occludable drainage angles in this population. The augmented scheme gives enhanced performance in detection of established PACG. The augmented scheme has potential for good interobserver agreement.

A prospective ultrasound biomicroscopy evaluation of changes in anterior segment morphology after laser iridotomy in asian eyes

PURPOSE To prospectively quantify changes in anterior segment morphology after laser iridotomy using gonioscopy and ultrasound biomicroscopy (UBM). DESIGN Prospective comparative observational case series. PARTICIPANTS Fifty-five fellow eyes of patients presenting with acute primary angle closure (APAC). METHODS The fellow eyes of patients presenting with APAC were examined with UBM, A-scan ultrasonography, and optical pachymetry at presentation and 2 weeks after sequential argon/neodymium yttrium-aluminum-garnet laser peripheral iridotomy (LPI). UBM images were analyzed using UBM Pro 2000 software. Baseline measurements were made both under standard lighting conditions and in darkness to look for changes in anterior segment findings. MAIN OUTCOME MEASURES The degree of angle opening was measured using the angle-opening distance (AOD) at 250 and 500 microm from the scleral spur (AOD250 and AOD500, respectively) and angle recess area (ARA). RESULTS Fifty-five Asian patients were examined; AOD250, AOD500, and ARA all significantly increased after sequential laser iridotomy (P < 0.002). Gonioscopic grading of the angle opening significantly increased in all 4 quadrants (P < 0.001). The Van Herick grade of limbal anterior chamber depth increased (P < 0.001), whereas the number of eyes classified as occludable decreased (73%-33%, P < 0.001). Anterior chamber depth did not change significantly (2.41 mm +/- 0.28 mm vs. 2.42 mm +/- 0.30 mm, P = 0.43) as measured with optical pachymetry. Increased illumination increased the angle-opening measures, but induced a different alteration in peripheral iris morphology. Illumination-induced changes were greater after iridotomy than before laser treatment. CONCLUSIONS In Asian eyes at high risk of developing APAC, sequential LPI produced a significant widening of the anterior chamber angle without deepening the anterior chamber centrally. LPI produces changes in iris morphology that are different from those caused by an increase in illumination, indicating that different mechanisms account for angle opening under these 2 conditions.

The Singapore 5-Fluorouracil Trabeculectomy Study: Effects on Intraocular Pressure Control and Disease Progression at 3 Years

PURPOSE To report 3-year results of a randomized, controlled trial comparing the use of a single application of 5-fluorouracil (5-FU) with placebo in trabeculectomy surgery. DESIGN Prospective, randomized, double-blinded treatment trial. PARTICIPANTS Two hundred forty-three Asian patients with primary open-angle or primary angle-closure glaucoma undergoing primary trabeculectomy. METHODS One eye of each patient was randomized to receive either intraoperative 5-FU or normal saline (placebo) during trabeculectomy. MAIN OUTCOME MEASURES Primary outcome measure was the level of intraocular pressure (IOP). Secondary outcomes were progression of visual field loss, rates of adverse events, and interventions after surgery. RESULTS Of the 288 eligible patients, 243 were enrolled and 228 completed 3 years follow-up; 120 patients received 5-FU and 123 received placebo. Trial failure, according to predefined IOP criteria, was lower in the 5-FU group compared with the placebo group, although the difference was only significant with a failure criterion of IOP >17 mmHg (P = 0.0154). There was no significant difference in progression of optic disc and/or visual field loss over 36 months between 5-FU and placebo (relative risk [RR], 0.67; 95% confidence interval [CI], 0.34-1.31; P = 0.239). Uveitis occurred more often in the 5-FU-treated group (14/115 [12%] vs 5/120 [4%]; P = 0.032). CONCLUSIONS This is the first masked, prospective, randomized trial reporting the effect of adjunctive 5-FU in trabeculectomy surgery in an East Asian population. The trial shows that an increased success rate can be achieved for several years after a single intraoperative treatment with 5-FU. We conclude that 5-FU is relatively safe and can be routinely used in low-risk East Asian patients. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any materials discussed in this article.

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; r2 = 0.19), (POAG: r = 0.21, p = 0.13; r2 = 0.04) and AGIS score (PACG: r = 0.41, p = 0.003; r2 = 0.17), (POAG: r = 0.23, p = 0.19; r2 = 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.

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

AbstractAim 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 vsPOAG=6.48±5.58, P=0.001), superior (PACG=4.31±3.39 vsPOAG=3.35±3.13, P=0.035), and inferior (PACG=4.43±3.31 vsPOAG=2.64±2.77, P<0.0001) areas and mean deviation (MD) asymmetry scores (PACG=6.89±13.22 vsPOAG=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.

Optic disc hemorrhage in Asian glaucoma patients

PurposeTo assess the prevalence of optic disc hemorrhage in Asian patients with established glaucoma using a recently described, highly sensitive detection method. Materials and MethodsPatients entering a trial of glaucoma filtering surgery in Southeast Asia (The Singapore 5FU Study) were assessed for the presence or absence of optic disc hemorrhage using stereo flicker chronoscopy of stereophotograph pairs. ResultsA total of 167 patients (117 males and 50 females) were assessed, of whom 128 were Chinese. Primary open-angle glaucoma was diagnosed in 90 patients, primary angle-closure glaucoma in 69 patients, and pseudoexfoliative or pigment dispersion glaucoma in 7 patients. Five eyes of 5 patients had disc hemorrhage at enrollment (5/167), a rate of 2.99%. Four patients with disc hemorrhage had primary open-angle glaucoma and 1 had primary angle-closure glaucoma. There were no significant differences in global visual field indices, AGIS scores, or intraocular pressures between eyes with and without disc hemorrhage. All disc hemorrhages were seen in eyes prior to trabeculectomy. ConclusionsThe prevalence of disc hemorrhage in the current study was comparable to that seen in primary open-angle glaucoma in clinic-based studies of white patients, but far less than that reported in normal-tension glaucoma studies. Hemorrhages were more common in primary open-angle glaucoma than primary angle-closure glaucoma.

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

AbstractPurpose 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 vs0.15, P<0.0001). Corrected pattern standard deviation (6.1 vs6.4, 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.