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SNP rs2157719 in the CDKN2B-AS1 gene may influence cup-to-disc ratio in patients with primary open angle glaucoma

Khaled K. Abu-Amero

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

Department of Ophthalmology, College of Medicine, Jacksonville, Florida, USA

E-mail : aa

Altaf A. Kondkar

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

Ahmed Mousa

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

Taif A. Azad

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

Faisal A. Almobarak

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

Tahira Sultan

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

Saleh Altuwaijri

SAAD Research & Development Center, Clinical Research Lab., SAAD Specialist Hospital, P.O. Box 30353, Al Khobar 31952, Saudi Arabia

Qassim University, Saudi Arabia

Saleh A. Al-Obeidan

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia

DOI: 10.15761/JTS.1000171

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Abstract

Background: Several studies have provided strong evidence that gene variants at the cyclin-dependent kinase inhibitor 2B antisense non-coding RNA (CDKN2B-AS1) locus of 9p21 is an important risk factor in the development of primary open angle glaucoma (POAG) making it a strong candidate for risk factor screening.

Objectives: The present study investigated the possible association of SNP rs2157719 in CDKN2B-AS1 with POAG and specific glaucoma indices used to assess disease severity in a Saudi cohort.

Materials and methods: Genotyping of SNP rs2157719 was performed in 85 unrelated POAG cases and 95 normal controls of Saudi origin using Taq-Man® real-time PCR assay and its association with the POAG and other clinical indices was evaluated.

Results: The genotype frequencies did not deviate significantly from the Hardy-Weinberg equilibrium (p>0.05). The minor ‘G’ allele frequency was observed to be 0.18 in cases and 0.21 in controls. Both the genotype and allele frequencies did not vary significantly between cases and controls. However, the homozygous mutant genotype (G/G) was found to be significantly associated with family history of glaucoma (p= 0.018), smoking (p= 0.033) and awareness of glaucoma (p= 0.039). In addition, carriers of the heterozygous (A/G) genotype had significantly higher cup/disc ratio (p= 0.028) as compared to the wild-type.

Conclusion: SNP rs2157719 in the CDKN2B-AS1 is not associated with POAG but may affect cup-to-disc ratio and therby modulate optic nerve pathology.

Key words

CDKN2B-AS1, middle-east, POAG, rs2157719

Introduction

Primary open angle glaucoma (POAG) is a genetically complex disease exhibiting well-established associations with various known mutations and single nucleotide polymorphisms (SNPs) [1]. Genetic variants at the chromosome 9p21 locus has been shown to be strongly associated with POAG [2]. The associated locus includes cyclin-dependent kinase inhibitor-2A (CDKN2A), -2B (CDKN2B) and -2B antisense RNA 1 (CDKN2B-AS1) genes. CDKN2BAS-1, is a long non-coding RNA located within the p15/CDKN2B-p16/CDKN2A-p14/ARF gene cluster transcribed in the antisense direction [3]. Although the exact biological function of this non-coding gene is largely unknown. However, it has been shown to regulate transcription of CDKN2A/2B through epigenetic mechanisms and implicated in several other diseases [4-6]. In addition, the expression of CDKN2B/AS1 is dramatically induced by transforming growth factor (TGF)-β which is known to play a critical role in POAG pathogenesis [7,8].

Several genome-wide association studies (GWASs) and candidate gene investigation among different ethnic groups have provided strong evidence that gene variants at the CDKN2B-AS1 locus of 9p21 is an important risk factor in the development of POAG [9-14] highlighting its association with disease pathogenesis and making it a strong candidate for risk factor screening. A recent population-based GWAS performed by Li et al. across 18 collections of Asian, African and European descent provided strong evidence of association of SNP rs2157719 at the CDKN2B-AS1 locus (odds ratio, OR = 0.71, P = 2.81 x 10-33) [13]. The genetic contribution of this variants at the CDKN2B-AS1 locus among Saudi POAG patients is not known. The present study investigated the possible association of SNP rs2157719 in CDKN2B-AS1 with POAG and specific glaucoma indices used to assess disease severity in a Saudi cohort.

Material and methods

Study population

This case-control cross-sectional study was conducted between October 2015 and February 2016 at King Abdulaziz University Hospital, King Saud University, Riyadh, Saudi Arabia. The study adhered to the tenets of the Declaration of Helsinki for research involving humans and was approved by the Ethical Committee of College of Medicine, King Saud University (approval number # 08-657). All the participants signed an informed consent. POAG cases (n = 85) satisfied the following clinical criteria: (1) appearance of the disc or retinal nerve fibre layer showing, e.g. thinning or notching of disc rim, progressive changes, nerve fibre layer defect, (2) presence of characteristic abnormalities in the visual field (e.g. arcuate scotoma, nasal step, paracentral scotoma, generalized depression) in the absence of other causes or explanation, (4) ≥40 years of age at the time of recruitment, and (4) open anterior chamber angles bilaterally on gonioscopy. Secondary glaucoma, e.g. pigmentary dispersion syndrome, pseudoexfoliation, uveitis, history of steroid use, ocular trauma or non-participation were excluded. Inclusion criteria for ethnically matched healthy control subjects (n = 95) included: age ≥40 years, normal IOP (<21 mmHg), open angles and normal optic disc on examination.

DNA extraction

DNA was extracted from peripheral blood (7 mL) collected in EDTA tubes using the illustra blood genomicPrep Mini Spin kit (GE Healthcare, Buckinghamshire, UK). DNA was quantified using a NanoDrop ND-2000c spectrophotometer (Thermo Scientific, Wilmington, DE, USA) and stored at –20°C in aliquots until further use.

Genotyping

Genotyping of intronic polymorphism, rs2157719 (A>G), of the CDKN2B-AS1 gene (NC_000009.12) was performed using the TaqMan® SNP Genotyping assay ID: C_2618013_10 (Applied Biosystems Inc., Foster City, CA, USA) on ABI 7500 real-time PCR system (Applied Biosystems). Each PCR reaction was performed in a 96-well plate in a total volume of 25 µL consisting of 1X TaqMan® Genotyping Master Mix (Applied Biosystems), 1X SNP Genotyping Assay Mix, 20 ng DNA, and two no template (negative) controls under cycling conditions recommended by the manufacturer [15]. Genotypes of CDKN2B-AS1 rs2157719 SNP were identified using the automated 2-color allele discrimination software on ABI 7500 on a two-dimensional graph.

Statistical analysis

 Data management, coding and storage were done using Microsoft Excel 2010® software (Microsoft Corporation; Redmond, WA, USA). The continuous variables were presented as mean (± Standard Deviation, SD) and analyzed by Student’s t-test. Categorical variables were presented as frequencies and percentages. Hardy-Weinberg Equilibrium (HWE) deviation was tested by Pearson’s Chi2 test. Odds ratio was calculated and Chi2 test was used to detect any association between different characteristics and the genetic profiles (Fisher Exact test where applicable). Yates’ correction was applied for frequency less than 5. Mann-Whitney-U test was used to compare means across differnet allele groups to investigate association between genotypes and clinical variables. The confidence interval level was set to 95% and a p value below 0.05 was considered statistically significant. Data were analyzed using SPSS® version 20.0 (IBM Inc., Chicago, Illinois, USA) and StatsDirect® statistical software, version 2.7.2 (StatsDirect Ltd., Cheshire, UK).

Results

Demographic and clinical characteristics

The POAG cases showed a mean age (±SD) of 60.9 (12.7) years as compared to 56.4 (15.8) in controls which was not significant (P = 0.068). Both the groups were found to be similar in terms of gender distribution (P = 0.321) with a pre-dominance of male subjects. As expected, family history of glaucoma (P = 0.014), and awareness to having glaucoma (p < 0.0001) were found to be statistically significantly different. However, smoking and presence of other systemic diseases such as diabetes, hypertension and hypercholesterolemia did not increase the risk of POAG (Table 1).

Table 1. Demographic and clinical co-morbidity in POAG patients and controls at presentation

Characteristic

Cases (n= 85)

No. (%)

Controls (n= 95)

No. (%)

P value

Age in years, mean (±SD)

60.9 (12.7)

56.4 (15.8)

0.068

Male                 

53 (62.4)

70 (73.7)

0.321

Female             

32 (37.6)

25 (26.3)

 

Family history of glaucoma

11 (12.9)

3 (3.2)

0.014

Diabetes mellitus                

49 (57.6)

43 (45.3)

0.097

Smoking                            

35 (41.2)

47 (49.5)

0.265

Hypertension                        

44 (51.8)

53 (55.8)

0.589

Coronary artery disease     

6 (7.1)

3 (3.2)

0.361

Hypercholesterolemia          

14 (16.5)

8 (8.4)

0.076

Awareness to glaucoma     

15 (17.6)

0 (0.0)

<0.001

Significant P values are indicated in bold. 

Genotype and Allele frequency distribution

 Table 2 shows the genotype and allelic frequency observed among POAG cases and normal controls. The genotype frequencies did not deviate significantly from the HWE (P > 0.05). The overall genotype distribution as tested by 2x3 Fisher Exact probability test was found to be non-significant (P = 0.468). Besides, as compared to wild-type genotype (A/A), the heterozygous (A/G), the mutant homozygous (G/G) and the AG+GG (dominant effect) genotypes did not differ significantly between cases and controls. Similarly, the allele frequencies did not vary significantly between cases and controls. The minor ‘G” allele frequency was found to be 0.18 and 0.21 among cases and controls, respectively.

Table 2. Distribution of genotype and allele frequency in cases and controls

Genotype/Allele

Cases (n= 85)

No. (%)

Control (n= 95)

No. (%)

Odds ratio

95% Confidence interval

P value*

A/A

56 (65.9)

60 (63.2)

1

-

-

A/G

27 (31.8)

29 (30.5)

0.9

0.500 – 1.983

0.988

G/G

2 (2.4)

6 (6.3)

0.4

0.342 – 2.120

0.281

A/G+G/G

29 (34.1)

35 (36.8)

0.88

0.48 – 1.63

0.88

A

139 (81.8)

149 (78.4)

1

-

-

G

31 (18.2)

41 (21.6)

1.2

0.733 – 2.07

0.429

*P value is calculated considering the normal allele (A/A) as the reference group.

Effect of Genotypes on systemic co-morbidities and specific glaucoma indices

Table 3 shows the comparison of demographic characteristics, systemic co-morbidities, and specific clinical indices among cases according to genotypes. Except for family history of glaucoma (P = 0.018), smoking (P = 0.033) and awareness of glaucoma (P = 0.039) no other clinical parameter analyzed was found to be associated only with mutant homozygous (G/G) genotypes. In addition, comparison of glaucoma specific indices such as IOP, cup/disc ratio and number of anti-glaucoma medications did not differ significantly, except that the patients carrying the heterozygous (A/G) genotype had significantly higher cup/disc ratio (P = 0.028) as compared to the wild-type (A/A) genotypes.

Table 3. Association of genotypes with demographic, systemic co-morbidities, and glaucoma specific indices among cases

Characteristic

A/A (n= 56)

No. (%)

A/G (n= 27)

No. (%)

P value*

G/G (n= 2)

No. (%)

P value*

Age in years, mean (±SD)

62.3 (11.9)

58.2 (14.0)

0.122

55.5 (16.3)

0.103

Male     

36 (64.3)

15 (55.6)

0.443

2 (100)

0.774

Female

20 (35.7)

12 (44.4)

-

0 (0)

-

Family history of glaucoma

7 (8.2)

2 (2.1)

0.747

2 (100)

0.018

Diabetes mellitus

34 (60.7)

13 (48.1)

0.279

2 (100)

0.701

Smoking

23 (41.1)

11 (40.7)

0.971

1 (50)

0.033

Hypertension

29 (51.8)

13 (48.1)

0.765

2 (100)

0.534

Coronary artery disease

3 (3.5)

2 (2.1)

0.713

1 (50)

0.304

Hypercholesterolemia

9 (16.0)

4 (14.8)

0.882

1 (50)

0.768

Awareness to glaucoma

9 (16.0)

4 (14.8)

0.882

2 (100)

0.039

Intraocular pressure in mmHg, mean (±SD)

35.4 (7.6)

34.9 (6.7)

0.884

37.5 (9.1)

0.654

Cup/disc ratio, mean (±SD)

0.7 (0.2)

0.8 (0.2)

0.028

0.6 (0.1)

0.507

Number of anti-glaucoma medications, mean (±SD)

2.9 (90.7)

2.9 (0.5)

0.641

3.0 (1.4)

0.872

*P value is calculated considering the normal allele (A/A) as the reference group. Significant P values are indicated in bold. 

Discussion

Since the initial identification of association between CDKN2B-AS1 locus with POAG in the Australian cohort [9], several other GWAS and candidate gene studies have replicated this association in the US Caucasians [10], African-Caribbean [16], Japanese [11], Asian, African and European population [12,13]. In this study, we report a lack of association between SNP rs215779 in CDKN2B-AS1 and POAG in a Saudi cohort.

SNP rs215779 (G allele) has been reported to be associated with reduced risk of POAG in the Asian, African and Caucasian population [10,13]. The ‘G’ allele has a minor allele frequency (MAF) of 0.44 in Caucasians and almost absent in African population (dbSNP database - http://www.ncbi.nlm.nih.gov/projects/SNP/snp_ref.cgi?rs=215779). The MAF observed in our Saudi POAG subjects was 0.18 which is lower than the Caucasians but higher than the Africans. Perhaps, a very low frequency of this SNP may explain, atleast in part, the high risk of POAG in these ethnic groups. Both the genotype and allele frequency of rs215779 in the CDKN2B-AS1 were not found to be a significantly associated with the risk of POAG in our Saudi cohort. However, it should be noted that consistent with the previous reports, our genotype analysis did indicate of a protective trend associated with the ‘G’ allele. However, this effect was found to be non-significant suggesting that due to small sample size the study lacks the power to detect this trend effectively.

Cup-to-disc ratio is an important clinical parameter for the diagnosis and monitoring of POAG disease process. Variants of CDKN2B-AS1 are reported to be associated with cup-to-disc ratio in the general population [17,18] and POAG [10,19]. Interestingly, the variant (G) allele of rs215779 has been reported to be associated with smaller cup/disc ratio. In contrast, the patients carrying the heterozygous (A/G) genotype showed significant association with larger cup/disc ratio (p= 0.028) as compared to the wild-type (A/A) genotypes. This effect was absent in the homozygous mutant (G/G) POAG patients. The most likely reason for this discrepancy could be the reduced number of samples present in this group suggesting that a larger sample size with high power of study is required to detect any significant relative risk of this association.

Conclusion

Our study shows that SNP rs2157719 in the CDKN2B-AS1 is not associated with POAG in Saudi cohort, but may affect cup-to-disc ratio. However, since the study is limited by the fact that it is performed in a specific ethnicity and evaluated in a relatively small number of patients this aspect would need further investigation in a much larger cohort.

Acknowledgements

The authors would like to thank the Glaucoma Research Chair at the Department of Ophthalmology, College of Medicine, King Saud University for funding this study.

Availability of data and materials

The data supporting the conclusions of this article are all presented within the article.

Authors’ contributions

A – research concept and design; B – collection and/or assembly of data; C – data analysis and interpretation; D – writing the article; E – critical revision of the article; F – final approval of article.

Competing interests

None to declare. Authors have no conflict of interests.

Ethics approval and consent to participate

The study adhered to the tenets of the Declaration of Helsinki and had received approval from the Institutional Review Board and Research Ethics Committee. Written, informed consent was obtained from all participants prior to their inclusion in this study.

References

  1. Abu-Amero K, Kondkar AA, Chalam KV (2015) An Updated Review on the Genetics of Primary Open Angle Glaucoma. Int J Mol Sci 16: 28886-28911. [Crossref]
  2. Ng SK, Casson RJ, Burdon KP, Craig JE (2014) Chromosome 9p21 primary open-angle glaucoma susceptibility locus: a review. Clin Experiment Ophthalmol 42: 25-32. [Crossref]
  3. Pasmant E, Laurendeau I, Heron D, Vidaud M, Vidaud D, et al. (2007) Characterization of a germ-line deletion, including the entire INK4/ARF locus, in a melanoma-neural system tumor family: identification of ANRIL, an antisense noncoding RNA whose expression coclusters with ARF. Cancer Res 67: 3963-3969. [Crossref]
  4. Pasmant E, Sabbagh A, Vidaud M, Bièche I (2011) ANRIL, a long, noncoding RNA, is an unexpected major hotspot in GWAS. FASEB J 25: 444-448. [Crossref]
  5. Cunnington MS, Santibanez Koref M, Mayosi BM, Burn J, Keavney B (2010) Chromosome 9p21 SNPs Associated with Multiple Disease Phenotypes Correlate with ANRIL Expression. PLoS Genet 6: e1000899. [Crossref]
  6. Jarinova O, Stewart AF, Roberts R, Wells G, Lau P, et al. (2009) Functional analysis of the chromosome 9p21.3 coronary artery disease risk locus. Arterioscler Thromb Vasc Biol 29: 1671-1677. [Crossref]
  7. Fuchshofer R, Tamm ER (2012) The role of TGF-β in the pathogenesis of primary open-angle glaucoma. Cell Tissue Res 347: 279-290. [Crossref]
  8. Hannon GJ, Beach D (1994) p15INK4B is a potential effector of TGF-beta-induced cell cycle arrest. Nature 371: 257-261. [Crossref]
  9. Burdon KP, Macgregor S, Hewitt AW, et al. (2011) Genome-wide association study identifies susceptibility loci for open angle glaucoma at TMCO1 and CDKN2B-AS1. Nat Genet 43: 574-578. [Crossref]
  10. Wiggs JL, Yaspan BL, Hauser MA, Kang JH, Allingham RR, et al. (2012) Common variants at 9p21 and 8q22 are associated with increased susceptibility to optic nerve degeneration in glaucoma. PLoS Genet 8: e1002654. [Crossref]
  11. Osman W, Low SK, Takahashi A, Kubo M, Nakamura Y (2012) A genome-wide association study in the Japanese population confirms 9p21 and 14q23 as susceptibility loci for primary open angle glaucoma. Hum Mol Genet 21: 2836-2842. [Crossref]
  12. Burdon KP, Crawford A, Casson RJ, Hewitt AW, Landers J, et al. (2012) Glaucoma risk alleles at CDKN2B-AS1 are associated with lower intraocular pressure, normal-tension glaucoma, and advanced glaucoma. Ophthalmology 119: 1539-1545. [Crossref]
  13. Li Z, Allingham RR, Nakano M, Jia L, Chen Y, et al. (2015) A common variant near TGFBR3 is associated with primary open angle glaucoma. Hum Mol Genet 24: 3880-3892. [Crossref]
  14. Kimura Y, Akagi T, Miyake M, Yamashiro K, Yoshikawa M, et al. (2016) Association between the CDKN2B-AS1 Gene and Primary Open Angle Glaucoma with High Myopia in Japanese Patients. Ophthalmic Genet 37: 242-244. [Crossref]
  15. Abu-Amero KK, Kondkar AA, Mousa A, Osman EA, Al-Obeidan SA (2014) Association of Mn-SOD mutation (c.47T > C) with various POAG clinical indices. Ophthalmic Genet 35: 85-90. [Crossref]
  16. Cao D, Jiao X, Liu X, Hennis A, Leske MC, et al. (2012) CDKN2B polymorphism is associated with primary open-angle glaucoma (POAG) in the Afro-Caribbean population of Barbados, West Indies. PLoS One 7: e39278. [Crossref]
  17. Ramdas WD, van Koolwijk LM, Ikram MK, Jansonius NM, de Jong PT, et al. (2010) A genome-wide association study of optic disc parameters. PLoS Genet 6: e1000978. [Crossref]
  18. Ramdas WD, van Koolwijk LM, Lemij HG, Pasutto F, Cree AJ, et al. (2011) Common genetic variants associated with open-angle glaucoma. Hum Mol Genet 20: 2464-2471. [Crossref]
  19. Pasquale LR, Loomis SJ, Kang JH, Yaspan BL, Abdrabou W, et al. (2013) CDKN2B-AS1 genotype-glaucoma feature correlations in primary open-angle glaucoma patients from the United States. Am J Ophthalmol 155: 342-353 e345. [Crossref]

 

Editorial Information

Editor-in-Chief

Terry Lichtor

Article Type

Case Report

Publication history

Received date: October 26, 2016
Accepted date: December 01, 2016
Published date: December 05, 2016

Copyright

©2016 Abu-Amero KK. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation

Abu-Amero KK, Kondkar AA, Mousa A, Azad TA, Almobarak FA, et al. (2016) SNP rs2157719 in the CDKN2B-AS1 gene gene may influence cup-to-disc ratio in patients with primary open angle glaucoma. J Transl Sci 3: doi: 10.15761/JTS.1000171

Corresponding author

Prof. Khaled K. Abu-Amero, Ph.D, FRCPath,

Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, P.O. Box 245, Riyadh 11411, Saudi Arabia, Tel: +96612825290; Fax: +96614775724

Table 1. Demographic and clinical co-morbidity in POAG patients and controls at presentation

Characteristic

Cases (n= 85)

No. (%)

Controls (n= 95)

No. (%)

P value

Age in years, mean (±SD)

60.9 (12.7)

56.4 (15.8)

0.068

Male                 

53 (62.4)

70 (73.7)

0.321

Female             

32 (37.6)

25 (26.3)

 

Family history of glaucoma

11 (12.9)

3 (3.2)

0.014

Diabetes mellitus                

49 (57.6)

43 (45.3)

0.097

Smoking                            

35 (41.2)

47 (49.5)

0.265

Hypertension                        

44 (51.8)

53 (55.8)

0.589

Coronary artery disease     

6 (7.1)

3 (3.2)

0.361

Hypercholesterolemia          

14 (16.5)

8 (8.4)

0.076

Awareness to glaucoma     

15 (17.6)

0 (0.0)

<0.001

Significant P values are indicated in bold. 

Table 2. Distribution of genotype and allele frequency in cases and controls

Genotype/Allele

Cases (n= 85)

No. (%)

Control (n= 95)

No. (%)

Odds ratio

95% Confidence interval

P value*

A/A

56 (65.9)

60 (63.2)

1

-

-

A/G

27 (31.8)

29 (30.5)

0.9

0.500 – 1.983

0.988

G/G

2 (2.4)

6 (6.3)

0.4

0.342 – 2.120

0.281

A/G+G/G

29 (34.1)

35 (36.8)

0.88

0.48 – 1.63

0.88

A

139 (81.8)

149 (78.4)

1

-

-

G

31 (18.2)

41 (21.6)

1.2

0.733 – 2.07

0.429

*P value is calculated considering the normal allele (A/A) as the reference group.

Table 3. Association of genotypes with demographic, systemic co-morbidities, and glaucoma specific indices among cases

Characteristic

A/A (n= 56)

No. (%)

A/G (n= 27)

No. (%)

P value*

G/G (n= 2)

No. (%)

P value*

Age in years, mean (±SD)

62.3 (11.9)

58.2 (14.0)

0.122

55.5 (16.3)

0.103

Male     

36 (64.3)

15 (55.6)

0.443

2 (100)

0.774

Female

20 (35.7)

12 (44.4)

-

0 (0)

-

Family history of glaucoma

7 (8.2)

2 (2.1)

0.747

2 (100)

0.018

Diabetes mellitus

34 (60.7)

13 (48.1)

0.279

2 (100)

0.701

Smoking

23 (41.1)

11 (40.7)

0.971

1 (50)

0.033

Hypertension

29 (51.8)

13 (48.1)

0.765

2 (100)

0.534

Coronary artery disease

3 (3.5)

2 (2.1)

0.713

1 (50)

0.304

Hypercholesterolemia

9 (16.0)

4 (14.8)

0.882

1 (50)

0.768

Awareness to glaucoma

9 (16.0)

4 (14.8)

0.882

2 (100)

0.039

Intraocular pressure in mmHg, mean (±SD)

35.4 (7.6)

34.9 (6.7)

0.884

37.5 (9.1)

0.654

Cup/disc ratio, mean (±SD)

0.7 (0.2)

0.8 (0.2)

0.028

0.6 (0.1)

0.507

Number of anti-glaucoma medications, mean (±SD)

2.9 (90.7)

2.9 (0.5)

0.641

3.0 (1.4)

0.872

*P value is calculated considering the normal allele (A/A) as the reference group. Significant P values are indicated in bold.