Diagnostic ability of Elisar ZEST algorithm for glaucoma in chennai main hospital

Introduction:

Glaucoma affects more than 70 million people worldwide with approximately 10% being bilaterally blind,(1) making it the leading cause of irreversible blindness in the world. Glaucoma can remain asymptomatic until it is severe, where people who are affected are higher compared which the ones diagnosed with it(2,3). Population-level surveys suggest that only 10% to 50% of people with glaucoma are aware they have it. (2,3),(3–5).

Automated perimeters give the threshold estimates of each point in the visual field. It does not tell the presence or absence of glaucoma. Probability-based methods have been tried to detect the presence or absence of glaucoma. The glaucoma hemifield test (GHT) is one such test. Anderson is another criterion given by Anderson. Our study aims to find the sensitivity and specificity of each of the criteria of  Anderson criteria results of Elisar AVA’s ZEST algorithm and SITA standard algorithm with a 24-2 pattern with the clinical diagnosis as the gold standard.

Elisar AVA Field Analyzer is the Virtual Reality (VR) based perimetry device which measures up to 30 degrees of the visual field with eye-tracking. The unique Head Mounted Device (HMD) has a user interface that facilitates a real-time interaction with the patient through the patient response button (PRB). The test facilitator uses a handheld android tablet to control the HMD.

Objective of the study:

The objective of the study is to evaluate the diagnostic ability of the 24-2 Elisar ZEST algorithm for glaucoma with each criterion of Anderson criteria with clinical diagnosis as the gold standard.

Study design: Cross sectional observational study

Method:

The study will be done in 3 different phases:

1.    Pre-study work up.

2.    Stage I

3.    Stage II

1. Pre-study workup:

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·         This study is about the diagnostic ability of AVA.​

·         If the device identify a normal patient as abnormal and an abnormal patient as normal due to errors in either HFA or AVA.​

·         This could be due to​:

o   Inappropriate handling of the device​

o   Improper mounting​

o   Artifacts​

·         The issues seen from the previous study data will be fixed before starting Stage I. â€‹

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2. Stage I

·         60 consecutive subjects (20 controls and 40 glaucoma’s)​

·         A perimetry test will be performed in both HFA and AVA for each patient based on randomization.​

·         The data will be analyzed for the frequency of occurrence of the issues will be calculated. â€‹

·         If there is one of the above issues reported in at least one of the subjects, then it is corrected by training the optometrist and the whole cycle of phase will be repeated. â€‹

·         If we do not find any of the above issues we will proceed with stage II. â€‹

 3. Stage II

·         AVA 24-2 Elisar ZEST and HFA 24-2 SITA standard will be done on 142 normal eyes and 62 glaucoma eyes.​

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·         Sensitivity and specificity of 24-2 Elisar ZEST algorithm to diagnose glaucoma with the clinical diagnosis as the gold standard. â€‹

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Sample size:

Number of cases = 62

Number of controls = 142

Inclusion criteria

1.   The age should be 18 or older with an approximately equal number of male and female population in the study.​

2.   Visual acuity tested within one week of the trial should be better than 6/18 â€‹

3.   The spherical equivalent of refractive error should be â‰¤ Â± 5 D​

4.   Pseudo phakic patients 6 weeks postop can be included in the study.​

 Inclusion into the control group:

Normal subjects will be recruited who has:

1.    Intraocular pressure (IOP) in AT < 21 mmHg,

2.    Optic disc examination graded as normal.

3.    No family history of glaucoma.

 Inclusion into glaucoma group:

 1.    Glaucoma diagnosis will be based on the presence of typical glaucomatous optic disc damage (i. e. Cup: disc ratio > 0.6, localized rim loss, optic disc hemorrhage, or cup-to-disc asymmetry > 0.2), â€‹

2.    IOP in AT > 21 mmHg.​

3.    Glaucoma of any type without any secondary complications. â€‹

4.    Glaucomatous Optic Neuropathy (GON) detection by glaucoma expert.

 **Exclusion criteria:**1.    Subjects who have undergone ocular surgeries, with ocular disease, amblyopia, neurological disorders will be excluded from the study.​

2.    Subjects will be excluded with systemic or ocular disease other than glaucoma that might interfere with visual field results.​

3.    The cataract greater than moderate lens opacification will be excluded from the study as per the LOCS III grading system. â€‹

4.    Using a miotic drug will be excluded from the study (6-7)

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 Expected outcome:

The expected sensitivity and specificity of AVA’s Elisar ZEST algorithm with clinical diagnosis as the gold standard should be above 90% and 80% respectively.

 The sensitivity and specificity of the Elisar ZEST should be comparable to the sensitivity and specificity of the SITA standard. â€‹

  Duration: 4 months

Reference:

1.    Quigley HA. The number of people with glaucoma worldwide in 2010 and 2020. British Journal of Ophthalmology. 2006 Mar 1;90(3):262–7.

2.    Leite MT, Sakata LM, Medeiros FA. Managing glaucoma in developing countries. Arq Bras Oftalmol. 2011 Apr;74(2):83–4.

3.    Rotchford AP, Kirwan JF, Muller MA, Johnson GJ, Roux P. Temba glaucoma study: a population-based cross-sectional survey in urban South Africa. Ophthalmology. 2003 Feb;110(2):376–82.

4.    Hennis A, Wu S-Y, Nemesure B, Honkanen R, Leske MC. Awareness of Incident Open-angle Glaucoma in a Population Study. Ophthalmology. 2007 Oct;114(10):1816–21.

5.    Ronnie G, Baskaran M, Hemamalini A, Madan R, Augustian J, Prema R, et al. Determinants of glaucoma awareness and knowledge in urban Chennai. Indian J Ophthalmol. 2009;57(5):355.

6.       Donald L Budenz , Paul Rhee, William J Feuer, John McSoley, Chris A Johnson,          Douglas R Anderson,Sensitivity and specificity of the Swedish interactive threshold algorithm for glaucomatous visual field defects.Ophthalmology 2002 Jun;109(6):1052-8 7.    Azfar C Wadood 1, Augusto Azuara-Blanco, Peter Aspinall, Abdel Taguri, Anthony J W King,Sensitivity and specificity of frequency-doubling technology, tendency-oriented perimetry, and Humphrey Swedish interactive threshold algorithm-fast perimetry in a glaucoma practice. American Journal of Opthalmology 2002 Mar;133(3):327-32.