Genetic association study of exfoliation syndrome identifies a protective rare variant at LOXL1 and five new susceptibility loci

Exfoliation syndrome (XFS) is the most common known risk factor for secondary glaucoma and a major cause of blindness worldwide. Variants in two genes, LOXL1 and CACNA1A, have previously been associated with XFS. To further elucidate the genetic basis of XFS, we collected a global sample of XFS cases to refine the association at LOXL1, which previously showed inconsistent results across populations, and to identify new variants associated with XFS. We identified a rare protective allele at LOXL1 (p.Phe407, odds ratio (OR) = 25, P = 2.9 × 10^-14) through deep resequencing of XFS cases and controls from nine countries. A genome-wide association study (GWAS) of XFS cases and controls from 24 countries followed by replication in 18 countries identified seven genome-wide significant loci (P < 5 × 10^-8). We identified association signals at 13q12 (POMP), 11q23.3 (TMEM136), 6p21 (AGPAT1), 3p24 (RBMS3) and 5q23 (near SEMA6A). These findings provide biological insights into the pathology of XFS and highlight a potential role for naturally occurring rare LOXL1 variants in disease biology.

Investigation of the variability of anterior chamber scan protocol with Cirrus high definition optical coherence tomography

IMPORTANCE

The evaluation of anterior chamber scan of Cirrus optical coherence tomography for routine clinical use.

BACKGROUND

To assess the variability of anterior chamber angle measurements.

DESIGN

This was a cross-sectional study.

PARTICIPANTS

Forty subjects aged 40-80 years were included.

METHODS

One randomly selected eye from 40 subjects was imaged with Cirrus optical coherence tomography (Carl Zeiss Meditec, Dublin, CA) by two different operators (expert vs. non-expert) with a 15-min interval for inter-observer and intra-observer variability of image acquisition. For image grading, the angle opening distance (AOD750) and the trabecular iris space area (TISA750) of nasal and temporal quadrants were measured with a customized algorithm (ImageJ, NIH, Bethesda, MD) by two different graders in a masked and random fashion. Bland Altman analysis and intraclass correlation coefficient (ICC) were calculated.

MAIN OUTCOME MEASURES

ICC and limit of agreements (LOA).

RESULTS

There were 15 (37.5%) eyes with closed angles. For inter-observer variability, the mean difference (95% LOA) of AOD750 for image acquisition and grading were -0.0039 mm (-0.0486, 0.0408) and 0.0011 mm (-0.0228, 0.025), respectively. The mean difference (95% LOA) of AOD750 for intra-observer variability for image acquisition and grading were 0.0013 mm (-0.0362, 0.0389) and -0.0013 mm (-0.0482, 0.0457), respectively. The ICCs were all ≥0.9. There was no significant difference in measurement variability between open and closed angles (P > 0.05).

CONCLUSIONS AND RELEVANCE

Anterior chamber scan had low inter-observer and intra-observer variability in quantitative evaluation that was not affected by the angle status or the experience of an operator.

Aqueous outflow facility after phacoemulsification with or without goniosynechialysis in primary angle closure: a randomised controlled study

BACKGROUND

Goniosynechialysis (GSL) to remove peripheral anterior synechiae (PAS) alongside standard cataract surgery has potential theoretical advantages, Published randomised trials, however, have not shown conclusive functional benefits and aqueous outflow changes following GSL are unknown. This study aimed to compare electronic Shiøtz tonographic aqueous outflow facility (TOF) following phacoemulsification with or without GSL in patients with primary angle closure (PAC) and PAC glaucoma. Secondary outcomes were changes in intraocular pressure (IOP) and use of glaucoma medications.

METHODS

Prospective randomised pilot study of 26 patients on glaucoma medication, with ≥90° PAS and significant lens opacity. Patients were randomised 1:1 to receive phacoemulsification with intraocular lens (IOL) implantation only (phaco) or phacoemulsification with IOL plus GSL (phaco-GSL).

RESULTS

Fourteen patients were randomised to phaco-GSL and 12 to phaco alone. TOF increased with phaco-GSL from 0.099±0.07 μL/min/mm Hg to 0.194±0.07, μL/min/mm Hg, p=0.0006, while the phaco group showed no significant change. IOP reduced in both groups, but reduced significantly more following phaco-GSL (46.0%) compared with phaco alone (27.6%, p=0.04). Medication use and extent of PAS only reduced with phaco-GSL, from 0.923±0.86 to 0.384±0.18 medications, p=0.0279, and from 249.2±83.4 to 110.8±53.9° PAS, 6 months postoperatively. No serious adverse events occurred in either group.

CONCLUSIONS

Eyes randomised to both surgical groups had similar and good outcomes at 6 months in this pilot study. However, only eyes undergoing GSL combined with standard phacoemulsification had significantly increased TOF, reduced glaucoma medication dependence and PAS postoperatively. GSL should therefore be considered in such patients.

TRIAL REGISTRATION NUMBER

NCT00719290, Results.

A common variant near TGFBR3 is associated with primary open angle glaucoma

Primary open angle glaucoma (POAG), a major cause of blindness worldwide, is a complex disease with a significant genetic contribution. We performed Exome Array (Illumina) analysis on 3504 POAG cases and 9746 controls with replication of the most significant findings in 9173 POAG cases and 26 780 controls across 18 collections of Asian, African and European descent. Apart from confirming strong evidence of association at CDKN2B-AS1 (rs2157719 [G], odds ratio [OR] = 0.71, P = 2.81 × 10(-33)), we observed one SNP showing significant association to POAG (CDC7-TGFBR3 rs1192415, ORG-allele = 1.13, Pmeta = 1.60 × 10(-8)). This particular SNP has previously been shown to be strongly associated with optic disc area and vertical cup-to-disc ratio, which are regarded as glaucoma-related quantitative traits. Our study now extends this by directly implicating it in POAG disease pathogenesis.

A common variant mapping to CACNA1A is associated with susceptibility to exfoliation syndrome

Exfoliation syndrome (XFS) is the most common recognizable cause of open-angle glaucoma worldwide. To better understand the etiology of XFS, we conducted a genome-wide association study (GWAS) of 1,484 cases and 1,188 controls from Japan and followed up the most significant findings in a further 6,901 cases and 20,727 controls from 17 countries across 6 continents. We discovered a genome-wide significant association between a new locus (CACNA1A rs4926244) and increased susceptibility to XFS (odds ratio (OR) = 1.16, P = 3.36 × 10(-11)). Although we also confirmed overwhelming association at the LOXL1 locus, the key SNP marker (LOXL1 rs4886776) demonstrated allelic reversal depending on the ancestry group (Japanese: OR(A allele) = 9.87, P = 2.13 × 10(-217); non-Japanese: OR(A allele) = 0.49, P = 2.35 × 10(-31)). Our findings represent the first genetic locus outside of LOXL1 surpassing genome-wide significance for XFS and provide insight into the biology and pathogenesis of the disease.

Lamina cribrosa visibility using optical coherence tomography: comparison of devices and effects of image enhancement techniques

PURPOSE

To compare the visibility of the lamina cribrosa (LC) in optic disc images acquired from 60 glaucoma and 60 control subjects using three optical coherence tomography (OCT) devices, with and without enhanced depth imaging (EDI) and adaptive compensation (AC).

METHODS

A horizontal B-scan was acquired through the center of the disc using two spectral-domain (Spectralis and Cirrus; with and without EDI) and a swept-source (DRI) OCT. Adaptive compensation was applied post acquisition to improve image quality. To assess LC visibility, four masked observers graded the 1200 images in a randomized sequence. The anterior LC was graded from 0 to 4, the LC insertions from 0 to 2, and the posterior LC either 0 or 1. The effect of EDI, AC, glaucoma severity, and other clinical/demographic factors on LC visibility was assessed using generalized estimating equations.

RESULTS

The anterior LC was the most detectable feature, followed by the LC insertions. Adaptive compensation improved anterior LC visibility independent of EDI. Cirrus+EDI+AC generated the greatest anterior LC visibility grades (2.79/4). For LC insertions visibility, DRI+AC was the best method (1.10/2). Visibility of the posterior LC was consistently poor. Neither glaucoma severity nor clinical/demographic factors consistently affected LC visibility.

CONCLUSIONS

Adaptive compensation is superior to EDI in improving LC visibility. Visibility of the posterior LC remains poor suggesting impracticality in using LC thickness as a glaucoma biomarker.

The management of patients with cataracts and medically uncontrolled glaucoma

Trabeculectomy surgery has been shown to lower intraocular pressure and is the most commonly performed glaucoma procedure worldwide. However, giving a patient a 'bleb for life' is not without consequences and the failure of trabeculectomy to control IOP in the long term is well documented. In some instances, such as in patients with exfoliative glaucoma or primary angle closure glaucoma, cataract surgery alone can often lower IOP to acceptable levels. Cataract surgery in these instances can sometimes be combined with procedures such as goniosynechialysis or endoscopic cyclophotocoagulation which may provide additional IOP lowering. Such surgery has the distinct advantage of avoiding conjunctival incisions, so that subsequent trabeculectomy, if required, is more likely to be successful. In any case, it is preferable to perform trabeculectomy in a pseudophakic eye for several reasons. If trabeculectomy is performed in a phakic eye, patients should be warned that subsequent cataract is likely and if cataract surgery is performed it is preferable to wait at least a year or more after the trabeculectomy to reduce the risk of bleb failure. Combined phacotrabeculectomy should be reserved for end-stage glaucoma in most cases, in order to reduce the risk of 'wipe-out'.

Longitudinal changes in anterior chamber depth and axial length in Asian subjects after trabeculectomy surgery

BACKGROUND/AIMS

To investigate longitudinal changes in anterior chamber depth (ACD) and axial length (AXL) over 5 years after trabeculectomy surgery in Asian patients with primary glaucoma, and to identify factors associated with these changes.

METHODS

In this prospective cohort study, phakic subjects with primary glaucoma who underwent trabeculectomy had ACD and AXL measured over 5 years. The effect of intraocular pressure (IOP) on ACD and AXL was determined. Subjects were divided into two groups (high or low fluctuation of ACD/AXL) and factors were compared to determine if there were factors associated with greater fluctuation.

RESULTS

122 subjects were analysed. The majority of subjects were male (75.4%) and Chinese (77%). ACD and AXL were shallower/shorter compared with baseline at all postoperative visits, with a mean decrease of 0.11 mm (95% CI 0.07 to 0.15 mm, p<0.01) and 0.16 mm (95%CI 0.11 to 0.20 mm, p<0.01), respectively. Patients with primary open angle glaucoma (POAG) had higher odds of fluctuations in longitudinal measurements of ACD (OR=8.74, p<0.01) and AXL (OR=5.60, p<0.01) compared with patients with primary angle closure glaucoma. For every 1 mm Hg decrease in IOP, ACD and AXL decreased by 0.02 mm (p<0.01) and 0.01 mm (p=0.03), respectively, for POAG patients with emmetropia or mild myopia.

CONCLUSIONS

Trabeculectomy resulted in a decrease in both ACD and AXL, and these changes were persistent over a period of 5 years.

Comparative human aqueous dynamics study between black and white subjects with glaucoma

PURPOSE

To compare the baseline aqueous humor dynamics in white Caucasians and patients of African origin with previously untreated primary open-angle glaucoma (POAG) or ocular hypertension (OHT).

METHODS

Ninety-one participants were enrolled in this prospective, observational controlled study: 34 black subjects with POAG or OHT, 32 white Caucasian participants with POAG or OHT, and 12 black and 13 white healthy volunteers as the controls. All aqueous humor parameters were taken between 9 AM and 12 noon on the same day. Intraocular pressure (IOP) was measured by pneumatonometer; morning aqueous humor flow rate was measured by fluorophotometry and trabecular outflow facility by electronic Schiøtz tonography. Uveoscleral outflow was calculated by using Goldmann's equation with assumed episcleral venous pressure of 8, 9, 10, and 11 mm Hg. Differences among groups were analyzed with parametric and nonparametric tests and the relationship between aqueous dynamics parameters were evaluated with linear regression analyses.

RESULTS

The POAG/OHT groups had similar IOP (white, 24.6 ± 3.0 mm Hg; black, 24.3 ± 4.0 mm Hg; comparison by Holm's sequential Bonferroni method (HBonf): P(HBonf) = 0.51), outflow facility (white, 0.13 ± 0.09 μL/min/mm Hg; black, 0.13 ± 0.07 μL/min/mm Hg; P(HBonf) = 0.87), aqueous flow (white, 2.36 ± 0.63 μL/min; black, 2.35 ± 0.53 μL/min; P(HBonf) = 0.95), and uveoscleral outflow (white, 0.42 ± 1.59 μL/min; black, 0.58 ± 1.17 μL/min; P(HBonf) = 1.78). POAG/OHT groups had significantly higher IOP and lower outflow facility than their healthy counterparts (P < 0.01). Black participants had significant thinner corneas (540 ± 37 μm vs. 564 ± 36 μm) than those of white participants (P = 0.002).

CONCLUSIONS

The aqueous humor dynamics of black African and white Caucasian patients with POAG or OHT have no significant differences. However, the significantly thinner corneas of the black patients may be masking potential differences in outflow facility and IOP measurements between the racial groups.

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.

Peripapillary atrophy after acute primary angle closure

AIM

To determine the changes in peripapillary atrophy after episodes of acute primary angle closure (APAC).

METHODS

Prospective observational study of 40 eyes in 38 patients of predominantly Chinese ethnicity. The mean (SD) intraocular pressure at the time of presentation was 51.7 (12) mm Hg (median, 55 mm Hg) and the mean duration of the symptoms was 37.7 (69.4) hours. A laser iridotomy was undertaken 3.2 (8.4) days after the APAC episode, leading to normalisation of intraocular pressure in all cases. Colour optic disc photographs taken at 2 and 16 weeks after APAC were examined morphometrically. Peripapillary atrophy was divided into alpha and beta zones.

RESULTS

Comparing measurements at baseline with week 16, the minimum width of the alpha zone (0.013 (0.056) v 0.016 (0.001) arbitrary units; p = 0.23), the maximum width of the alpha zone (1.11 (1.31) v 1.31 (0.79) arbitrary units; p = 0.22), the minimum width of the beta zone (0.030 (0.122) v 0.033 (0.166) arbitrary units; p = 0.93), and the maximum width of the beta zone (0.62 (0.94) v 0.73 (0.98) arbitrary units; p = 0.42) did not vary significantly. The mean cup to disc ratio increased from 0.56 (0.05) to 0.62 (0.07) (p<0.0001) at the end of follow up.

CONCLUSIONS

The alpha and beta zones of peripapillary atrophy did not enlarge markedly in patients after APAC, despite an enlargement of the optic cup during a follow up of four months.