European Glaucoma Society research priorities for glaucoma care

BACKGROUND/AIMS

The goal of health research is to improve patients care and outcomes. Thus, it is essential that research addresses questions that are important to patients and clinicians. The aim of this study was to develop a list of priorities for glaucoma research involving stakeholders from different countries in Europe.

METHODS

We used a three-phase method, including a two-round electronic Delphi survey and a workshop. The clinician and patient electronic surveys were conducted in parallel and independently. For phase I, the survey was distributed to patients from 27 European countries in 6 different languages, and to European Glaucoma Society members, ophthalmologists with expertise in glaucoma care, asking to name up to five research priorities. During phase II, participants were asked to rank the questions identified in phase I using a Likert scale. Phase III was a 1 day workshop with patients and clinicians. The purpose was to make decisions about the 10 most important research priorities using the top 20 priorities identified by patients and clinicians.

RESULTS

In phase I, 308 patients and 150 clinicians were involved. In phase II, the highest-ranking priority for both patients and clinicians was 'treatments to restore vision'. In phase III, eight patients and four clinicians were involved. The top three priorities were 'treatments to stop sight loss', 'treatments to restore vision' and 'improved detection of worsening glaucoma'.

CONCLUSION

We have developed a list of priorities for glaucoma research involving clinicians and patients from different European countries that will help guide research efforts and investment.

Outcomes of newly referred patients with suspected angle closure: do we need to redefine the clinical pathways?

BACKGROUND/OBJECTIVES

To investigate outcomes of referrals for suspected angle closure and explore whether anterior segment optical coherence tomography (AS-OCT) can be used to tighten triaging criteria in a glaucoma virtual clinic.

SUBJECTS/METHODS

Retrospectively collected data. The first audit (04/2018-03/2019) identified referrals for suspected angle closure without other glaucoma-related findings (primary angle closure suspect (PACS) referrals). All patients underwent gonioscopy. The second audit (04-08/2019) identified patients with suspected angle closure in a virtual clinic. Management outcomes were assessed, using gonioscopy as reference standard. The outcomes of the second audit were re-audited after changing the triaging criterion from angle width <10° to iridotrabecular contact (ITC) in ≥1 quadrants on AS-OCT.

RESULTS

Out of 1754 glaucoma referrals (first audit), 24.6% (431/1754) were PACS referrals. Of these, only 10.7% (42/393) had an occludable angle on gonioscopy, with 97.6% (41/42) being PACS. Of these, 78% (32/41) underwent laser peripheral iridotomy. Out of 137 referrals in the virtual clinic (second audit), 66.4% (91/137) were triaged to the face-to-face clinic. Of these, 31.9% (29/91) were discharged. AS-OCT had positive and negative predictive value of 74.3% (95% confidence intervals (CI) 57.8-86.0) and 82.1% (95% CI 70.0-90.2%), respectively, in detecting ITC in ≥1 quadrants. In the re-audit 45.9% (45/98) of those with suspected angle closure were triaged for gonioscopy, with 24.4% (11/45) of them being discharged.

CONCLUSION

PACS referrals represent a substantial burden to hospital-based services and their accuracy is low. ITC in ≥1 quadrants on AS-OCT can be useful in triaging those who need further evaluation with gonioscopy.

Twelve-Year Incidence of Open-angle Glaucoma: The Thessaloniki Eye Study

OBJECTIVE

The objective of this study was to determine the 12-year incidence of open-angle glaucoma (OAG), with further classification into primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG), in an elderly White population.

DESIGN

A longitudinal, population-based study in urban Northern Greece.

PARTICIPANT

Surviving cohort of the 2554 Thessaloniki Eye Study subjects 60 years and above who had the baseline examination.

METHODS

The surviving cohort was re-examined 12 years after baseline, using the same methodology and the same standard operating procedures as in the baseline examination. The definitions of glaucoma and pseudoexfoliation were consistent throughout the study. The 12-year incidences of OAG, POAG, and PEXG with corresponding 95% confidence intervals (CIs) were calculated for the whole study population, consisting of clinic-visit and home-visit participants. The population at risk was defined as those who did not meet the study criteria for the diagnosis of glaucoma in either eye at baseline.

MAIN OUTCOME MEASURES

Twelve-year incidence of OAG, with further classification into POAG and PEXG.

RESULTS

Of 1468 eligible subjects in the surviving cohort, 1092 were examined (participation rate 74%). Mean age at baseline was 68.9±4.6 years. Mean follow-up time was 11.6±1.6 years. The 12-year incidence of OAG was 4.4% (95% CI: 3.3-5.8); 0.37% per year. In the overall population the incidence of POAG and PEXG was 2.1% (95% CI: 1.3-3.2) and 2.3% (95% CI: 1.5-3.4), respectively. The corresponding incidence proportions were 2.9 (95% CI: 1.8-4.3) in those without PEX and 8.9 (95% CI: 5.8-12.9) in those with PEX at baseline and/or incidence. The latter was strongly associated with higher odds for incident glaucoma (odds ratio=3.34, 95% CI: 1.83-6.08, P<0.001). Of all incident OAG cases, 11.1% (95% CI: 4.4-24) had baseline intraocular pressure >21 mm Hg.

CONCLUSIONS

The incidence of OAG was similar or higher compared with other White populations. The incidence of glaucoma in those with PEX was higher compared with the incidence of glaucoma in those without PEX.

Association of Rare CYP39A1 Variants With Exfoliation Syndrome Involving the Anterior Chamber of the Eye

IMPORTANCE

Exfoliation syndrome is a systemic disorder characterized by progressive accumulation of abnormal fibrillar protein aggregates manifesting clinically in the anterior chamber of the eye. This disorder is the most commonly known cause of glaucoma and a major cause of irreversible blindness.

OBJECTIVE

To determine if exfoliation syndrome is associated with rare, protein-changing variants predicted to impair protein function.

DESIGN, SETTING, AND PARTICIPANTS

A 2-stage, case-control, whole-exome sequencing association study with a discovery cohort and 2 independently ascertained validation cohorts. Study participants from 14 countries were enrolled between February 1999 and December 2019. The date of last clinical follow-up was December 2019. Affected individuals had exfoliation material on anterior segment structures of at least 1 eye as visualized by slit lamp examination. Unaffected individuals had no signs of exfoliation syndrome.

EXPOSURES

Rare, coding-sequence genetic variants predicted to be damaging by bioinformatic algorithms trained to recognize alterations that impair protein function.

MAIN OUTCOMES AND MEASURES

The primary outcome was the presence of exfoliation syndrome. Exome-wide significance for detected variants was defined as P < 2.5 × 10-6. The secondary outcomes included biochemical enzymatic assays and gene expression analyses.

RESULTS

The discovery cohort included 4028 participants with exfoliation syndrome (median age, 78 years [interquartile range, 73-83 years]; 2377 [59.0%] women) and 5638 participants without exfoliation syndrome (median age, 72 years [interquartile range, 65-78 years]; 3159 [56.0%] women). In the discovery cohort, persons with exfoliation syndrome, compared with those without exfoliation syndrome, were significantly more likely to carry damaging CYP39A1 variants (1.3% vs 0.30%, respectively; odds ratio, 3.55 [95% CI, 2.07-6.10]; P = 6.1 × 10-7). This outcome was validated in 2 independent cohorts. The first validation cohort included 2337 individuals with exfoliation syndrome (median age, 74 years; 1132 women; n = 1934 with demographic data) and 2813 individuals without exfoliation syndrome (median age, 72 years; 1287 women; n = 2421 with demographic data). The second validation cohort included 1663 individuals with exfoliation syndrome (median age, 75 years; 587 women; n = 1064 with demographic data) and 3962 individuals without exfoliation syndrome (median age, 74 years; 951 women; n = 1555 with demographic data). Of the individuals from both validation cohorts, 5.2% with exfoliation syndrome carried CYP39A1 damaging alleles vs 3.1% without exfoliation syndrome (odds ratio, 1.82 [95% CI, 1.47-2.26]; P < .001). Biochemical assays classified 34 of 42 damaging CYP39A1 alleles as functionally deficient (median reduction in enzymatic activity compared with wild-type CYP39A1, 94.4% [interquartile range, 78.7%-98.2%] for the 34 deficient variants). CYP39A1 transcript expression was 47% lower (95% CI, 30%-64% lower; P < .001) in ciliary body tissues from individuals with exfoliation syndrome compared with individuals without exfoliation syndrome.

CONCLUSIONS AND RELEVANCE

In this whole-exome sequencing case-control study, presence of exfoliation syndrome was significantly associated with carriage of functionally deficient CYP39A1 sequence variants. Further research is needed to understand the clinical implications of these findings.

Factors associated with non-active retinal capillary density as measured with Confocal Scanning Laser Doppler Flowmetry in an elderly population: the Thessaloniki Eye Study (TES)

PURPOSE

To identify factors associated with retinal capillary density as measured with Confocal Scanning Laser Doppler Flowmetry (Heidelberg retina flowmeter (HRF)) in the Thessaloniki Eye Study (TES).

METHODS

Participants of the TES (age ≥60 years, cross-sectional population-based study) were assessed for active capillary density in the superior and inferior peripapillary retina using the HRF. Pixel-by-pixel analysis was performed to quantify the percentage of zero flow pixels (ZFPs; surrogate for % retinal area with non-active capillaries). Multivariable regression analyses were performed to assess the association of non-active vascular density with ophthalmic and systemic variables. Glaucoma, late age-related macular degeneration and diabetic retinopathy subjects were excluded.

RESULTS

1189 subjects were included in the analysis. Older age (per year) was associated with higher percentage of ZFP in both the superior (slope estimate (SE)=0.0020) and the inferior (SE=0.0019) peripapillary retina (p<0.0001). History of migraine was associated with lower percentage of ZFP (SE=-0.0166) compared with no history of migraine in the superior peripapillary retina only (p<0.05). Higher intraocular pressure ((IOP) per mm Hg) and height (per cm) were associated with higher percentage of ZFP in the inferior peripapillary retina only (SE=0.0012, p<0.05 and SE=0.0005, p<0.05, respectively). The group consuming vegetables one to three times per week compared with the group consuming vegetables at least once a day had higher percentage of ZFP only in the inferior peripapillary retina (SE=0.0080, p<0.05).

CONCLUSION

At a population level, our study revealed associations of older age, higher IOP and taller height with lower active retinal capillary density and of migraine with higher capillary density. Looking further into these associations may provide insight into disease mechanisms.

Factors Associated With Retinal Vessel Diameters in an Elderly Population: the Thessaloniki Eye Study

Purpose

To identify the factors associated with retinal vessel diameters in the population of the Thessaloniki Eye Study.

Methods

Cross-sectional population-based study (age ≥ 60 years). Subjects with glaucoma, late age-related macular degeneration, and diabetic retinopathy were excluded from the analyses. Retinal vessel diameters were measured using the IVAN software, and measurements were summarized to central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriole to venule ratio (AVR).

Results

The analysis included 1614 subjects. The hypertensive group showed lower values of CRAE (P = 0.033) and AVR (P = 0.0351) compared to the normal blood pressure (BP) group. On the contrary, the group having normal BP under antihypertensive treatment did not have different values compared to the normal BP group. Diastolic BP (per mm Hg) was negatively associated with CRAE (P < 0.0001) and AVR (P < 0.0001), while systolic BP (per mm Hg) was positively associated with CRAE (P = 0.001) and AVR (P = 0.0096). Other factors significantly associated included age, sex, alcohol, smoking, cardiovascular disease history, ophthalmic medication, weight, and IOP; differences were observed in a stratified analysis based on BP medication use.

Conclusions

Our study confirms previous reports about the association of age and BP with vessel diameters. The negative correlation between BP and CRAE seems to be guided by the effect of diastolic BP as higher systolic BP is independently associated with higher values of CRAE. The association of BP status with retinal vessel diameters is determined by diastolic BP status in our population. Multiple other factors are also independently associated with retinal vessel diameters.

Twelve-Year Incidence and Baseline Risk Factors for Pseudoexfoliation: The Thessaloniki Eye Study (An American Ophthalmological Society Thesis)

PURPOSE

To determine the 12-year incidence of pseudoexfoliation (PEX), baseline risk factors for incident PEX and risk factors for incident pseudoexfoliative glaucoma (PEXG) among those with PEX in an elderly white population.

METHODS

Longitudinal, population-based study in Thessaloniki, the major urban center in Northern Greece. The baseline cohort included 2554 participants ≥60 years old. The surviving cohort was re-examined 12 years later using the same methodology. PEX was defined as typical fibrillar material at the pupil margin and/or on the lens capsule. Glaucoma was defined as both structural and functional damage, irrespective of intraocular pressure (IOP).

RESULTS

Of 1468 eligible subjects in the surviving cohort, 1092 (74%) participated in the follow-up study. The mean age ± standard deviation (SD) at baseline was 68.9 ± 4.6 years. The mean follow-up time was 11.6 ± 1.6 years. The 12-year incidence of PEX was 19.6% (95% confidence interval (CI), 17.1-22.2), with women more likely to be affected than men (Fisher's exact test, P = .0197). Higher axial length was associated with lower odds of incident PEX (odds ratio [OR], 0.72 per mm; 95% CI, 0.57-0.92). PEX at baseline was not associated with an increased likelihood of major vascular disease (P = .9038). Higher baseline IOP (OR, 1.26 per mm Hg; 95% CI, 1.07-1.48) and history of heart attack at baseline (OR, 13.49; 95% CI, 2.85-63.87) were associated with a greater likelihood of developing PEXG among those with PEX. A history of alcohol consumption at baseline was protective of individuals developing PEXG if they had PEX at baseline.

CONCLUSION

This is one of the very few longitudinal population-based studies that has specifically assessed the incidence of PEX. The association with axial length was previously found only in a cross-sectional study. The associations with heart attack and alcohol consumption are new findings. In individuals with baseline PEX, higher IOP at baseline, history of heart attack at baseline, and no alcohol consumption were associated with a greater likelihood of developing glaucomatous damage approximately 12 years later. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Overdiagnosis of open-angle glaucoma in the general population: the Thessaloniki Eye Study

PURPOSE

To assess the overdiagnosis of open-angle glaucoma (OAG) and to investigate associated factors.

METHODS

This was a cross-sectional, population-based study of an urban Caucasian population in northern Greece. Randomly selected subjects ≥60 years (n = 2554) participated in the Thessaloniki Eye Study. The definition of OAG required the presence of structural and functional damage, irrespective of intraocular pressure (IOP). Non-OAG subjects were classified as overdiagnosed with OAG if they had reported at least one of the following (self-reported glaucoma): (i) prior diagnosis of glaucoma, (ii) prior laser for glaucoma, (iii) prior glaucoma surgery. Factors associated with the overdiagnosis of OAG were investigated using a logistic regression model.

RESULTS

Of 57 (2.2%) subjects with self-reported glaucoma, 34 (60%) were overdiagnosed with OAG, corresponding to a prevalence of 1.3% (34/2554). In a logistic regression model among non-OAG subjects, worse visual acuity (VA) (20/200 or worse versus 20/25 or better; odds ratio (OR) = 4.30, 95% Confidence Intervals (CI), 1.13-16.35), family history of glaucoma (OR = 8.69, 95% CI, 2.83-26.67) and history of cataract surgery (OR = 11.50, 95% CI, 3.85-34.36) were statistically significantly associated with the overdiagnosis of OAG. Age, sex, higher IOP, higher vertical cup-to-disc ratio and pseudoexfoliation were not statistically significant.

CONCLUSION

The overdiagnosis of OAG was substantial in this elderly, Caucasian population. The overdiagnosis of glaucoma has not been previously addressed in population-based studies and needs to be further explored.

The Decreasing Prevalence of Nonrefractive Visual Impairment in Older Europeans: A Meta-analysis of Published and Unpublished Data

TOPIC

To estimate the prevalence of nonrefractive visual impairment and blindness in European persons 55 years of age and older.

CLINICAL RELEVANCE

Few visual impairment and blindness prevalence estimates are available for the European population. In addition, many of the data collected in European population-based studies currently are unpublished and have not been included in previous estimates.

METHODS

Fourteen European population-based studies participating in the European Eye Epidemiology Consortium (n = 70 723) were included. Each study provided nonrefractive visual impairment and blindness prevalence estimates stratified by age (10-year strata) and gender. Nonrefractive visual impairment and blindness were defined as best-corrected visual acuity worse than 20/60 and 20/400 in the better eye, respectively. Using random effects meta-analysis, prevalence rates were estimated according to age, gender, geographical area, and period (1991-2006 and 2007-2012). Because no data were available for Central and Eastern Europe, population projections for numbers of affected people were estimated using Eurostat population estimates for European high-income countries in 2000 and 2010.

RESULTS

The age-standardized prevalence of nonrefractive visual impairment in people 55 years of age or older decreased from 2.22% (95% confidence interval [CI], 1.34-3.10) from 1991 through 2006 to 0.92% (95% CI, 0.42-1.42) from 2007 through 2012. It strongly increased with age in both periods (up to 15.69% and 4.39% in participants 85 years of age or older from 1991 through 2006 and from 2007 through 2012, respectively). Age-standardized prevalence of visual impairment tended to be higher in women than men from 1991 through 2006 (2.67% vs. 1.88%), but not from 2007 through 2012 (0.87% vs. 0.88%). No differences were observed between northern, western, and southern regions of Europe. The projected numbers of affected older inhabitants in European high-income countries decreased from 2.5 million affected individuals in 2000 to 1.2 million in 2010. Of those, 584 000 were blind in 2000, in comparison with 170 000 who were blind in 2010.

CONCLUSIONS

Despite the increase in the European older population, our study indicated that the number of visually impaired people has decreased in European high-income countries in the last 20 years. This may be the result of major improvements in eye care and prevention, the decreasing prevalence of eye diseases, or both.

Tolerable rates of visual field progression in a population-based sample of patients with glaucoma

AIMS

To provide population-based data on the maximum tolerable rate of progression to avoid visual impairment (maxTRoP_VI) and blindness (maxTRoP_BL) from open-angle glaucoma (OAG).

METHODS

Participants with OAG in the Thessaloniki Eye Study (cross-sectional, population-based study in a European population) were included in the analysis. Visual impairment was defined as mean deviation (MD) equal to or worse than -12dB and blindness as MD equal to or worse than -24dB. Additional thresholds for visual impairment were tested. For each participant maxTRoP_VI was defined as the rate of progression which would not lead to visual impairment during expected lifetime. MaxTRoP_BL was defined accordingly. Both parameters were calculated for each OAG subject using age, sex, MD and life expectancy data. The eye with the better MD per subject was included in the analysis.

RESULTS

Among 135 subjects with OAG, 123 had reliable visual fields and were included in the analysis. The mean age was 73±6 years and the median MD was -3.65±5.28dB. Among those, 69.1% would have a maxTRoP_VI slower than -1dB/year and 18.7% would have a maxTRoP_VI between -1 and -2dB/year. Also, 72.4% would have a maxTRoP_BL slower than -2dB/year. For all tested thresholds for visual impairment, approximately 86% of the OAG study participants would not be able to tolerate a rate of progression equal to or faster than -2dB/year.

CONCLUSIONS

The majority of patients with glaucoma in our study would have a maximum tolerable rate of progression slower than -1dB/year in their better eye. Patient-tailored strategies to monitor the visual field are important, but raise the issue of feasibility with regard to the number of visual field tests needed.

Prospective study of glaucoma referrals across Europe: are we using resources wisely?

BACKGROUND

To investigate the outcomes of glaucoma referrals across different European countries.

METHODS

250 patients newly referred to tertiary referral glaucoma specialist practices in the UK, Hungary, Slovenia, Italy and Greece were prospectively enrolled (50 consecutive patients per centre). Referral accuracy and predictive value of referral criteria for an intervention or further monitoring (positive predictive value) were analysed.

RESULTS

Same-day discharges occurred in 43% (95% CI 39% to 75%) (12/28) of optometrist-initiated referrals (UK only), 37% (95% CI 30% to 45%) (59/158) of ophthalmologist-initiated referrals (all centres) and 54% (95% CI 40% to 68%) (26/48) of self-referrals (Hungary, Italy and Greece). The percentages from all referral sources were 46% (95% CI 32% to 60%) in the UK, 56% (95% CI 44% to 70%) in Hungary, 30% (95% CI 17% to 43%) in Slovenia, 22% (95% CI 11% to 34%) in Italy and 60% (95% CI 46% to 74%) in Greece (p<0.001). Overall, the referring criterion was confirmed in 54% (95% CI 45% to 63%) (64/119) for intraocular pressure (IOP) >21 mm Hg, 56% (95% CI 43% to 69%) (33/59) for a suspicious optic disc and 61% (95% CI 45% to 77%) (22/36) for a suspicious visual field, with large between-country differences (p<0.05 for all comparisons). Of all referrals, 32% (95% CI 26% to 37%) were initiated on the basis of IOP >21 mm Hg only. By combining the IOP criterion with any other referring criterion, the positive predictive value increased from 56% (95% CI 45% to 67%) to at least 89% (95% CI 68% to 100%). In the UK, a hypothetical IOP threshold of >26 mm Hg, as a requirement for IOP-only referrals, would reduce IOP-only referrals by 44%, while not missing any definite glaucoma cases.

CONCLUSION

The accuracy of referrals was poor in the UK and the other countries. Requiring a combination of criteria and raising the IOP threshold for IOP-only referrals are needed to cut waste in clinical care.

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.

Ethnicity-Based Differences in the Association of LOXL1 Polymorphisms with Pseudoexfoliation/Pseudoexfoliative Glaucoma: A Meta-Analysis

Pseudoexfoliation (PEX) is an age-related disorder of the extracellular matrix; it is strongly associated with glaucoma, the leading cause of irreversible blindness worldwide. We conducted an ethnic-based meta-analysis of the association of LOXL1 polymorphisms with PEX/pseudoexfoliative glaucoma (PEXG). Association studies were retrieved systematically from PubMed, EMBASE, and Web of Knowledge. Allelic and genotype frequencies of rs3825942, rs1048661, and rs2165241 were compared between PEX/PEXG and controls. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using a random effects model. Overall, 39 independent cohorts were included. Rs3825942 (G) was an at risk allele for PEX/PEXG in Caucasians, Japanese, Koreans, Chinese, South Asians, and Middle Easterners, but protective in Black South Africans (OR = 0.10, 95%CI:0.06-0.16). Rs1048661 (G) was an at risk allele for PEX/PEXG in Caucasians, South Asians, Middle Easterners and Black South Africans, but was protective in Japanese (OR = 0.03, 95%CI:0.02-0.06) and Koreans (OR = 0.10, 95%CI:0.05-0.22). These associations we-re confirmed for the genotypic recessive models. Rs2165241 (C) was a protective allele for PEX/PEXG in Caucasians, but was an at risk allele in Japanese (OR = 7.49, 95%CI:3.22-17.41) and Koreans (OR = 6.63, 95%CI:2.60-16.90). This was confirmed for the genotypic dominant model. Other genetic and/or environmental factors may modify the effect of LOXL1 polymorphisms in certain ethnic groups.

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.

Association of LOXL1 polymorphisms with pseudoexfoliation, glaucoma, intraocular pressure, and systemic diseases in a Greek population. The Thessaloniki eye study

PURPOSE

To investigate the association of the two single-nucleotide polymorphisms (SNPs) in the lysyl oxidase-like 1 (LOXL1) gene with pseudoexfoliation syndrome (PEX), pseudoexfoliative glaucoma (PEXG), and primary open-angle glaucoma (POAG) in a Greek population-based setting, from the Thessaloniki Eye study.

METHODS

A total of 233 subjects with successful DNA extraction, PCR amplification, and genotyping were included in the genetic analysis of G153D and R141L SNPs of LOXL1 gene and classified into four groups: controls (n = 93); subjects with PEX (n = 40); POAG (n = 66); and PEXG (n = 34). Multinomial logistic regression was used to test their association with LOXL1 SNPs with adjustment for covariates. The association of LOXL1 with IOP (in untreated subjects) and with systemic diseases was explored.

RESULTS

Both LOXL1 SNPs were present in high frequencies in controls and cases. The G153D was strongly associated with both PEX (odds ratio [OR] = 23.2, P = 0.003 for allele G) and PEXG (OR = 24.75, P = 0.003 for allele G) and was not associated with POAG (P = 0.451). In contrast, the R141L was not associated with PEX (P = 0.81), PEXG (P = 0.063), or POAG (P = 0.113). No association of the G153D with either intraocular pressure (IOP) or systemic diseases was found.

CONCLUSIONS

In the Thessaloniki Eye Study, the G153D SNP of LOXL1 gene was strongly associated with both PEX and PEXG, whereas the R141L was not associated. No association of the LOXL1 with IOP or with systemic diseases was found. These findings further support the hypothesis that the LOXL1 gene contributes to onset of PEXG through PEX. Gene variants of LOXL1 do not help to identify those with PEX at increased risk for glaucoma development.

Association of open-angle glaucoma with perfusion pressure status in the Thessaloniki Eye Study

PURPOSE

To investigate the association of open-angle glaucoma (OAG), primary open-angle glaucoma (POAG), and pseudoexfoliative glaucoma (PEXG) with ocular perfusion pressure status (ocular perfusion pressure with or without antihypertensive treatment).

DESIGN

Cross-sectional, population-based study.

METHODS

A total of 2554 randomly selected, ≥ 60-year old subjects participated in the Thessaloniki Eye Study. Only clinic-visit participants (n = 2261), who had uniformly collected data, were included in the analyses. A logistic regression model was run for OAG in all clinic-visit participants; covariates included age, sex, diastolic ocular perfusion pressure, antihypertensive treatment, intraocular pressure (IOP), IOP-lowering treatment, pseudoexfoliation, and vascular factors identified as risk factors for glaucoma in a previous analysis. Similar logistic regression models were run separately for POAG and PEXG. In addition, logistic regression models were run for OAG, POAG, and PEXG in subjects with and without antihypertensive treatment. Also, logistic regression models were run to assess the role of systolic ocular perfusion pressure in OAG, POAG, and PEXG.

RESULTS

Among clinic-visits, 1212 subjects (53.7%) were using antihypertensive treatment. An association of borderline significance was found between low diastolic ocular perfusion pressure and POAG (OR = 0.84 per 10 mm Hg, 95% CI = 0.70-1.01, P = .059). The effect of antihypertensive treatment on POAG was not statistically significant (OR = 1.20, 95% CI = 0.75-1.91, P = .45). In subgroup analyses, diastolic ocular perfusion pressure was significantly associated with POAG in subjects using antihypertensive treatment (OR = 0.78 per 10 mm Hg, 95% CI = 0.62-0.97, P = .028). No association was found between diastolic ocular perfusion pressure and PEXG, regardless of the use of antihypertensive treatment. No associations were found between systolic ocular perfusion pressure and OAG, POAG, or PEXG, regardless of the use of antihypertensive treatment.

CONCLUSIONS

Low diastolic ocular perfusion pressure may be associated with increased risk for POAG. This association was confirmed in subjects treated for systemic hypertension in subgroup analysis. This may support the hypothesis that the concept of ocular perfusion pressure status may be more relevant to glaucoma pathogenesis than ocular perfusion pressure alone.

Association of sequence variation in the CX3CR1 gene with geographic atrophy age-related macular degeneration in a Greek population

PURPOSE

To explore the association of two single nucleotide polymorphisms (SNPs) in the CX3CR1 gene with grades of age-related macular degeneration (AMD) in a population-based setting.

METHODS

The Thessaloniki Eye study is a cross-sectional population-based epidemiologic study of chronic eye diseases in Thessaloniki, Greece. A total of 371 subjects were included and classified according to their AMD status. Subjects with AMD Grades 0-1 (n = 188) were compared to those with AMD Grades 2-3 (n = 138), to those with AMD Grade 4 (geographic atrophy) (n = 20) and to those with AMD Grade 5 (neovascular AMD) (n = 25) with regard to the presence of CX3CR1 polymorphisms (V249I and T280M). Polychotomous logistic regression analysis adjusted for age, gender, and smoking was conducted and the log-additive allelic model was preferred.

RESULTS

Participants with AMD Grade 4 were approximately three times more likely to carry the VI249 and nine times more likely to carry the II249 alleles, compared to those with AMD Grades 0-1, whereas those with AMD Grades 2-3 or Grade 5 did not differ. The T280M polymorphism was not associated with either AMD Grades 2-3 or AMD Grades 4 or 5.

CONCLUSION

In this Greek population, after adjusting for known risk factors, increased risk of geographic atrophy (GA) AMD among the carriers of the V249I polymorphism in the CX3CR1 gene was found. Our study failed to reveal any association with the T280M polymorphism reported in previous studies. Additional studies in different ethnic populations using standardized methodology are needed in order to confirm this association.

Agreement among three examiners of colour Doppler imaging retrobulbar blood flow velocity measurements

PURPOSE

To assess the agreement among three masked examiners on central retinal artery (CRA) and ophthalmic artery (OA) blood flow velocity measurements performed with colour Doppler imaging (CDI) in healthy volunteers.

METHODS

The study included 30 eyes of 15 healthy volunteers. Prior to the study, all examiners underwent intensive CDI training by an expert to facilitate uniformity in performing measurements according to a specific protocol. Following the eligibility visit, three masked examiners performed CDI measurements assessing the CRA and OA in both eyes of all subjects. All CDI images were analysed by a masked grader. Intraclass correlation coefficients (ICC) were calculated for peak systolic velocity (PSV) and end diastolic velocity (EDV) in the CRA and OA among the examiners. p-values < 0.05 were considered statistically significant.

RESULTS

The study included seven men and eight women (mean age 30.9 ± 4.5 years). In right eyes, ICCs for PSV and EDV in the CRA ranged from 0.917 to 0.961 and from 0.937 to 0.980, respectively. ICCs for PSV and EDV in the OA ranged from 0.802 to 0.926 and from 0.611 to 0.891, respectively. In left eyes, all ICCs for PSV and EDV were >0.9, both in the CRA and the OA. All p-values calculated for ICCs were statistically significant.

CONCLUSION

Expert training and execution of a specific protocol for CDI of ocular blood flow velocity measurements provide highly reproducible results in healthy volunteers. This is important for long-term studies assessing ocular hemodynamics, where multiple examiners may be involved.

Risk factors for primary open-angle glaucoma and pseudoexfoliative glaucoma in the Thessaloniki eye study

PURPOSE

To investigate risk factors for primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG) in the Thessaloniki Eye Study.

DESIGN

Cross-sectional, population-based study.

METHODS

Randomly selected subjects 60 years of age and older (n=2554) participated in the Thessaloniki Eye Study. Glaucomatous damage and presence of pseudoexfoliation (PEX) were defined according to specific criteria. Open-angle glaucoma (OAG) subjects were compared with nonglaucoma subjects (controls), POAG subjects were compared with controls without PEX, and PEXG subjects were compared with controls with PEX for demographic, lifestyle, ophthalmic, and systemic factors. Factors with P < .2 in the univariate analysis were retained for multivariate analyses.

RESULTS

In multivariate analysis restricted to persons who participated in clinic visits and who had at least 1 phakic eye (n=2078), intraocular pressure (odds ratio [OR], 1.21 per 1 mm Hg; P<.001), PEX (OR, 2.81; P<.001), history of coronary artery bypass or vascular surgery (OR, 1.95; P=.017), and moderate-to-high myopia (≥ -3 diopters; OR, 2.40; P=.009) were associated with higher odds for OAG. In analysis including all clinic visits (n=2261), age became significantly associated (OR, 1.05; P=.004). In multivariate analysis for POAG (n=1840), associations were found for age (OR, 1.04 per year; P=.048), IOP (OR, 1.19 per 1 mm Hg; P<.001), history of coronary artery bypass or vascular surgery (OR, 2.09; P=.01), and history of diabetes treated with insulin (OR, 3.05; P=.045). In multivariate analysis for PEXG (n=238), the latter was associated with increased IOP (OR, 1.25 per 1 mm Hg; P<.001).

CONCLUSIONS

IOP was the only factor associated with both POAG and PEXG, whereas moderate-to-high myopia showed borderline significance in both. Vascular systemic diseases and their treatment were associated only with POAG. The implications of these differences for the pathogenesis between the 2 common types of OAG should be explored further.

Increased likelihood of glaucoma at the same screening intraocular pressure in subjects with pseudoexfoliation: the Thessaloniki Eye Study

PURPOSE

To compare the clinical characteristics of primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG) identified in the Thessaloniki Eye Study and to evaluate the proportion of subjects with and without pseudoexfoliation (PEX) who have glaucoma by screening intraocular pressure (IOP).

DESIGN

Cross-sectional, population-based study.

METHODS

Randomly selected subjects > or =60 years (n = 2,554) participated in the Thessaloniki Eye Study. Subjects were classified as having POAG or PEXG according to specific criteria. POAG and PEXG cases were compared for various clinical characteristics. The proportion with glaucoma among subjects with PEX and the proportion with glaucoma among subjects without PEX were estimated by IOP levels.

RESULTS

Among the clinic-visit participants (n = 2,261), 94 subjects (4.2%) had POAG and 41 (1.8%) had PEXG. The prevalence of glaucoma among subjects with PEX was 15.2% and the prevalence of glaucoma among subjects without PEX was 4.7%. In subjects without treatment, the mean IOPs were 19.8 mm Hg and 24.3 mm Hg for POAG and PEXG, respectively. For IOP level >20 mm Hg, the proportion with glaucoma among subjects with PEX was higher than that for glaucoma among subjects without PEX (37% vs 15%; P = .004), while no statistically significant difference was found for IOP level < or =20 mm Hg (2.1% vs 2.1%; P = .999), Fisher exact test.

CONCLUSIONS

In the Thessaloniki Eye Study, for screening IOP </=20 mm Hg the proportion with glaucoma was similar in subjects with and without PEX. For IOP level >20 mm Hg, the proportion with glaucoma increased highly in subjects both with and without PEX, while it was much higher among those with PEX at the same screening IOP.

Reproducibility of pixel-by-pixel analysis of Heidelberg retinal flowmetry images: the Thessaloniki Eye Study

PURPOSE

To identify the investigator effect in the analysis results of Heidelberg retinal flowmetry (HRF) images when pixel-by-pixel analysis is performed.

METHODS

Thirty-two of 732 HRF images were randomly selected from a population-based study. Pixel-by-pixel analysis was performed by two trained masked graders in the following way: a square window of 40 x 40 pixels or two windows of 30 x 30 pixels or four windows of 20 x 20 pixels free from blood vessels at the peripapillary retina were identified. Using a 1 x 1-pixel window, the grader performed pointwise analysis according to a specific protocol. The analysis process was performed by each observer three times (A, B, C) at 1-week intervals. The percentage of pixels with < 1 arbitrary unit of flow (zero flow), the 10th, 25th, 50th, 75th and 90th percentiles and mean flow values were calculated. The difference between the results of analyses B-A and C-A for all HRF parameters was estimated using the Wilcoxon signed rank test. Mixed-effect regression models were also used after controlling for grader effect and correlation within subjects.

RESULTS

There was no statistically significant difference between the results of analyses B-A and C-A or for any parameter in the mixed-effect regression models. Intraclass correlation was 0.9665 for the percentage of zero flow pixels.

CONCLUSIONS

Pixel-by-pixel analysis of HRF images by trained graders remains a highly reproducible method. No grader effect was found. If a precise protocol is followed, the results are independent of the exact placement of the analysis windows and the pointwise analysis of the identified and mapped retinal tissue.