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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 112  |  Issue : 1  |  Page : 34-38

Early detection of glaucoma suspect by pattern electroretinogram


Department of Ophthalmology, Faculty of Medicine, Ain Sham University, Cairo, Egypt

Date of Submission23-Dec-2018
Date of Acceptance15-Jan-2019
Date of Web Publication26-Apr-2019

Correspondence Address:
Reham F Abdelrazek El-Shinawy
Ain Shams University, 4th District, Area No. 3, 5th Settlement, New Cairo, Cairo, 11835
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_74_18

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  Abstract 

Aim This study was intended to estimate the significance of pattern electroretinogram (PERG) in evaluation of the retinal ganglion cell function in patients with glaucoma.
Patients and methods An observational case–control study was done on 40 eyes of individuals whose age ranged between 30 and 65 years of age. They were divided into two equal groups. Control group had normal visual field and optical coherence tomography optic nerve, intraocular pressure (IOP) less than 21 mmHg, visual acuity more than 0.3, and cup disc ratio (C/D) less than 0.5. The case group was divided into two equal subgroups: group A had IOP more than 21 mmHg and C/D less than 0.5, and group B had IOP less than 21 mmHg and C/D more than 0.5. We excluded all cases with ocular or systemic diseases with negative effect on retinal function such as retinal detachment, retinitis pigmentosa, rheumatoid arthritis on hydroxychloroquine, diabetic patients on insulin or oral hypoglycemic, or cases with abnormal optic disc appearance such as optic disc drusen, coloboma, or tilted disc. All cases underwent full ophthalmological examination, including best-corrected visual acuity, complete anterior segment examination with slit-lamp biomicroscopy, and posterior segment examination using volk 90 D lens, along with IOP measurement using Goldmann applanation tonometer. Visual field assessment was done using Heidelberg Edge Perimeter, optical coherence tomography optic nerve using Heidelberg engineering, and glaucoma screening with ERG using glaucoma screening program.
Results There was a highly statistically significant difference between the groups regarding C/D and IOP. Regarding the PERG and different visual fields parameters, there was a highly statistically significant difference between the groups. There was a statistically significant negative correlation between PERG and both IOP and VF parameters in all different groups. No statistically significant correlation was found between PERG and C/D in all different groups.
Conclusion PERG has a prognostic value in recognition of retinal ganglion cell dysfunction, as an early indication for glaucoma development.

Keywords: glaucoma suspect, optical coherence tomography, pattern electroretinogram, visual field


How to cite this article:
Hassan HA, Abdelrazek El-Shinawy RF, Salman AR, Elsbaay ME. Early detection of glaucoma suspect by pattern electroretinogram. J Egypt Ophthalmol Soc 2019;112:34-8

How to cite this URL:
Hassan HA, Abdelrazek El-Shinawy RF, Salman AR, Elsbaay ME. Early detection of glaucoma suspect by pattern electroretinogram. J Egypt Ophthalmol Soc [serial online] 2019 [cited 2019 Jul 19];112:34-8. Available from: http://www.jeos.eg.net/text.asp?2019/112/1/34/257219


  Introduction Top


Glaucoma is the most commonly known optic neuropathy, which is described by continuous loss of the retinal ganglion cells (RGCs) and distinctive damage of the retinal nerve fiber layer (RNFL) [1].

Unfortunately, RNFL defect is difficult to be identified clinically, making early detection of glaucoma still controversial [2].

A ‘glaucoma suspect’ is a term reserved for the individual who has not yet well-established glaucoma but has characteristics making him/her in danger of developing it later on [3].

As clinical examination of both optical nerve head (ONH) and RNFL is vulnerable to the changeability, attention was directed to confident methods such as optical coherence tomography (OCT) optic nerve and certain visual field techniques to support early glaucoma determination [1].

Pattern electroretinogram (PERG) has an effective value as an electrophysiological test in judging the human RGC function for recognizing and distinguishing the glaucomatous eyes before visual field progression, as visual field is the subjective test that depends on patients’ changeability [4].

The purpose of this study was to evaluate the role of PERG in early detection of RGC dysfunction in patients with suspicion of glaucoma.


  Patients and methods Top


This is an observational case–control study that involved 40 eyes of 20 patients with age ranged between 30 and 65 years old.

They were divided into two equal groups:
  1. Control group, which included 20 eyes with normal visual field, normal OCT optic nerve, intraocular pressure (IOP) less than 21 mmHg, visual acuity more than 0.3, and cup disc ratio (C/D) less than 0.5.
  2. Case group, which included 20 eyes divided into two subgroups: group A included 10 eyes with IOP more than 21 mmHg and C/D less than 0.5, and group B included 10 eyes with IOP less than 21 mmHg and C/D more than 0.5.


The protocol of this study was approved by the Medical and Ethical Committee of Ain Shams University, and informed consent was obtained after giving detailed information about the purpose of this study.

In our study, we excluded all cases with ocular or systemic diseases that may have a negative effect on the retinal function such as retinal detachment, proliferative diabetic retinopathy, and retinitis pigmentosa; patients with rheumatoid arthritis on hydroxychloroquine; diabetic patients on insulin or oral hypoglycemic drugs; or cases with abnormal optic disc appearance such as optic disc drusen, coloboma, pit, or tilted disc.

All the patients underwent complete ophthalmological examination including best-corrected visual acuity, complete anterior segment examination using slit-lamp biomicroscopy, and posterior segment examination using Volk lens +90 D, as well as IOP measurement using Goldmann applanation tonometer.

Visual field assessment was done using Heidelberg Edge Perimeter, which provides 2-in-1 perimetry and enables us to detect visual field loss at early stage of disease using Standard Automated Perimetry (SAP) software, version 3.0. The Heidelberg Edge Perimeter also offers a 30-s screening strategy.

OCT optic nerve using Heidelberg engineering: OCT scanning was done using the OCT spectralis HRA, Software version 6.0.9, which had the following specifications: spectralis OCT has an acquisition rate of 40 000 A-scans per second (high speed resolution), a scan time of 1.2 s, with scan focus of 0.18 D. It uses a dual-beam SD-OCT and a confocal scanning laser ophthalmoscope that uses a scanning laser diode with a wavelength of 870 nm and an infrared reference image simultaneously to provide images of ocular structures. The instrument incorporates a real-time eye tracking system that couples confocal scanning laser ophthalmoscope and SD-OCT scanners to adjust for eye motion.

Glaucoma screening with PERG using glaucoma screening program allows testing of both eyes at the same time. Two-step measurements were as follows: step 1: check size 16° of arc, and step 2: check size of 0.8° of arc; the 0.8°/16° was taken.

Statistical analysis

Recorded data were analyzed using the statistical package for social sciences, version 20.0 (SPSS Inc., Chicago, Illinois, USA). Quantitative data were expressed as mean±SD. Qualitative data were expressed as frequency and percentage. A one-way analysis of variance when comparing between more than two means. Least significant difference post-hoc test was used for multiple comparisons between different variables. χ2 test of significance was used to compare proportions between two qualitative parameters. Pearson’s correlation coefficient (r) test was used to assess the degree of association between two sets of variables.

The confidence interval was set to 95%, and the margin of error accepted was set to 5%. So, the P value was considered significant as follows:
  1. P value less than 0.05 was considered significant.
  2. P value less than 0.001 was considered as highly significant.
  3. P value more than 0.05 was considered insignificant.



  Results Top


This case–control study included 40 eyes of 20 patients divided equally into control group with normal visual field, OCT optic nerve, IOP less than 21 mmHg, visual acuity more than 0.3, and C/D less than 0.5, and the case group divided subsequently into group A, which included 10 eyes with IOP more than 21 mmHg and C/D less than 0.5, and group B, which included 10 eyes with IOP less than 21 mmHg and C/D more than 0.5.

The mean age for control group was 40.10±7.67 years. Group A had mean age of 46.40±12.18 years, and for group B was 40.20±6.10 years, with no statistically significant difference between the groups.

The mean C/D for control group was 0.38±0.06 SD, for group A was 0.33±0.05 SD, and for group B was 0.64±0.05 SD.

The mean IOP for control group was 12.60±1.82 SD, for group A was 26.90±2.08 SD, and for group B was 13.00±2.67 SD.

Regarding the comparison between the groups according to PERG ([Table 1]), there was a highly statistically significant difference between the different groups.
Table 1 Comparison between groups according to pattern electroretinogram

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Regarding the comparison between the groups according to different visual fields parameters ([Table 2]), there was a highly statistically significant difference between the different groups.
Table 2 Comparison between groups according to visual field parameters

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There was a statistically significant negative correlation between PERG and IOP in all different groups ([Table 3], [Figure 1]).
Table 3 Correlation between pattern electroretinogram and intraocular pressure in each group

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Figure 1 Scatter plot between PERG and IOP. IOP, intraocular pressure; PERG, pattern electroretinogram.

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There was no statistically significant correlation between PERG and C/D in all different groups ([Table 4]).
Table 4 Correlation between pattern electroretinogram and cup disc ratio in each group

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There was a statistically significant negative correlation between PERG and VF parameters in all different groups ([Table 5]).
Table 5 Correlation between pattern electroretinogram with visual field in each group

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  Discussion Top


‘Glaucoma suspect’ is a term that is referred to an individual who has either high IOP (over 21 mmHg) or an abnormal optic disc, RNFL, or visual field findings but not yet developed glaucoma and has the possibility of developing it later, making constant follow-up fundamental for the early detection [3].

In both ocular hypertension treatment (OHT) study [5] and European glaucoma prevention study [6], high IOP and high pattern standard deviation are considered as risks for glaucoma development.

Although the visual field testing has been thoroughly used in diagnosis, staging, and follow-up of the disease, real loss of RGCs may become established before significant glaucomatous visual field changes become completely obvious [2].

Former studies have identified that for statistically significant abnormalities on SAP, 25–35% of RGCs are essential to be lost [7].

The PERG reflects the electrical activity of RGCs and has been widely used in identifying loss of their capacity in several retinal diseases such as glaucoma [8].

Earlier studies have recognized advanced reduction in PERG amplitude before significant loss on SAP in patients with either well-established glaucoma or those with OHT [9].This pilot study was directed to estimate the value of PERG in detection of RGCs integrity in both of normal individuals and glaucoma-suspect ones, comparing it with their visual field changes.

Our results showed highly statistically significant difference in PERG (P<0.001) and different visual field parameters (P<0.001) between the different groups.

There was a statistically significant negative correlation between PERG and IOP (P0.004) and between PERG and VF parameters (P=0.004 and 0.041) in all different groups, whereas there was no statistically significant correlation between PERG and C/D (P=0.576) in all different groups.

Our results are in agreement with former studies that evaluated the role of PERG in early diagnosis and follow-up of either OHT patients or glaucoma-suspected patients [9],[10],[11].

In this study, we used glaucoma screening program using PERG ratio, which remains the most valuable PERG parameter in detecting the RGC dysfunction [11], exhibiting that a proportion below 1.0 may turn into a mark for starting treatment as a prophylaxis for prevention of further worsening of RGCs function.

This study had several restrictions including its relatively small sample size with no follow-up time; consequently, further studies with larger sample size and longer follow-up time may be suggested to improve the diagnostic accuracy of the study.


  Conclusion Top


PERG is anticipated to be a valuable objective test in judging the function of the RGC layer in glaucoma-suspect patients particularly when other subjective tests such as visual field become inconvenient.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Dervisevic E, Pavljasevic S, Dervisevic A, Kasumovic SS. Challenges in early glaucoma detection. Med Arch 2016; 70:203–207.  Back to cited text no. 1
    
2.
Zaky AG, Yassin AT, ElSayid SH. Short wave-automated perimetry (SWAP) versus optical coherence tomography in early detection of glaucoma. Clin Ophthalmol 2016; 10:1819–1824.  Back to cited text no. 2
    
3.
American Academy of Ophthalmology. Primary open-angle glaucoma suspect, preferred practice pattern. San Francisco, CA: American Academy of Ophthalmology; 2015.  Back to cited text no. 3
    
4.
Bayer AU, Erb C. Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects. Ophthalmology 2002; 109:1009–1017.  Back to cited text no. 4
    
5.
Kass MA, Heuer DK, Higginbotham EJ, Johnson CA, Keltner JL, Miller JP et al. The Ocular Hypertension Treatment Study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol 2002; 120:701-713; discussion 829-830.  Back to cited text no. 5
    
6.
Miglior S, Zeyen T, Pfeiffer N, Cunha-Vaz J, Torri V, Adamsons I. Results of the European Glaucoma Prevention Study. Ophthalmology 2005; 112:366–375.  Back to cited text no. 6
    
7.
Medeiros FA, Lisboa R, Weinreb RN, Liebmann JM, Girkin C, Zangwill LM. Retinal ganglion cell count estimates associated with early development of visual field defects in glaucoma. Ophthalmology 2013; 120:736–744.  Back to cited text no. 7
    
8.
Porciatti V, Ventura LM. Physiologic significance of steady-state pattern electroretinogram losses in glaucoma: clues from simulation of abnormalities in normal subjects. J Glaucoma 2009; 18:535–542.  Back to cited text no. 8
    
9.
Wilsey LJ, Fortune B. Electroretinography in glaucoma diagnosis. Curr Opin Ophthalmol 2016; 27:118–124.  Back to cited text no. 9
    
10.
Bach M, Hoffmann MB. Update on the pattern electroretinogram in glaucoma. Optom Vis Sci 2008; 85:386–395.  Back to cited text no. 10
    
11.
Ventura LM, Golubev I, Feuer WJ, Porciatti V. Pattern electroretinogram progression in glaucoma suspects. J Glaucoma 2013; 22:219–225.  Back to cited text no. 11
    


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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