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ORIGINAL ARTICLE
Year : 2017  |  Volume : 30  |  Issue : 2  |  Page : 475-479

Opticalcoherence tomography versus perimetry in follow-up of glaucoma


1 Department of Ophthalmology, Faculty of Medicine Menoogia University, Shebin Elkom, Egypt
2 Department of Ophthalmology, Almahalla Ophthalmology Hospital, Almahalla, Egypt

Date of Submission15-Mar-2016
Date of Acceptance26-Jun-2016
Date of Web Publication25-Sep-2017

Correspondence Address:
Ahmed H Taha
5 Ahmed Mokhtar Street Aborady, Almahalla Alkupra, 31951
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.215430

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  Abstract 

Objective
The objective of this study was to evaluate the ability of optical coherence tomography(OCT) to detect glaucoma in its early stages and follow-up progression of the disease compared with visual field(VF) examination aiming for better control of the disease and decreasing the incidence of morbidity(blindness) resulting from this disease.
Background
Primary open angle glaucoma is the leading cause of irreversible world blindness. VF deficits are thought to be the functional expression of ganglion cell losses. OCT provides high-resolution images that allow in-vivo measurements of the retinal nerve fiber layer in cross-section.
Patients and methods
Twenty eyes diagnosed with primary open angle glaucoma were included in the study. All patients were subjected to complete ocular examination, VF examination by standard automated perimetry(SAP), and OCT assessment of the retinal nerve fiber layer in the primary visit. Follow-up periods were 3 and 6months by SAP and OCT assessment of the retinal nerve fiber.
Results
The follow-up period was 6months. SAP was nearly similar to OCT in detecting progression: eight(40%) eyes compared with 10(50%) eyes by OCT. OCT was better because of its ability to detect early any progression before functional affection, but the difference between them is not significant.
Conclusion
OCT was able to detect more progression compared with VF. In addition, it detected progression earlier compared with VF. OCT proved the ability to detect any structural changes before corresponding functional defects can be detected.

Keywords: glaucoma, open angle, optical coherence tomography, visual field


How to cite this article:
Nassar MK, Wagdy FM, Taha AH. Opticalcoherence tomography versus perimetry in follow-up of glaucoma. Menoufia Med J 2017;30:475-9

How to cite this URL:
Nassar MK, Wagdy FM, Taha AH. Opticalcoherence tomography versus perimetry in follow-up of glaucoma. Menoufia Med J [serial online] 2017 [cited 2019 Aug 19];30:475-9. Available from: http://www.mmj.eg.net/text.asp?2017/30/2/475/215430


  Introduction Top


Glaucoma is a chronic disease of the optic nerve characterized by the loss of retinal ganglion cells, and by specific patterns of progressively decreasing retinal sensitivity[1].

Over the years, the approach to following glaucoma progression has grown from administering serial visual field(VF) tests to detecting structural and functional changes with new modalities[2].

VF deficits are thought to be the functional expression of ganglion cell losses. The retinal sensitivity detected by standard automated perimetry(SAP) is measured using a logarithmic decibel scale[3]. Optical coherence tomography(OCT), first described in 1991 by Huang etal.[4], is a high-resolution method measuring the difference in the temporal delay of back-scattered light from the retinal nerve fiber layer(RNFL) and a reference mirror.

The third-generation instrument is able to quantify the thickness of the RNFL at a resolution of∼8–10 μm[5].

OCT is an imagingtechniquethat allows in-vivo measurements of the RNFL in cross-section. It provides quantitative RNFL thickness data; ideally, pairing of two such devices should show a good correlation between functional and structural examinations to permit a better interpretation of clinical findings and a more accurate staging of structural or visual impairment[6].


  Patients and Methods Top


This study is a prospective, comparative, randomized clinical trial. Twenty eyes diagnosed with primary open angle glaucoma(POAG) were included.

Those patients were recruited from the ophthalmic outpatient clinics in Menufya University Hospitals during the period from October 2013 to March 2015.

On baseline visit, all patients were subjected to complete ophthalmological examination, VF testing by SAP (Oculus Inc., Walldorf, Germany), and OCT assessment of the RNFL (Carl Zeiss Meditec Inc., HRT, Heidelberg Engineering, GmbH, Heidelberg, Germany). Consents were taken from all patients, and the research was approved by the institutional review board.

A reliable VF test was defined as one with fewer than 30% fixation losses, false positive or false negative responses, or a reliability factor more than 0.7.

VF was defined as abnormal according to the Anderson's criteria (glaucoma hemifield test outside the normal limits and more than or equal three adjacent points that have a probability<5%, one of which must have a probability<1%).

RNFL thickness values were either reported, as averages over each quadrant; temporal(316–45°), superior (46–135°), nasal(136–225°), inferior(226–315°), individually over each sector, as averages over the entire cylindrical section(360° scan) or as a graph with displaying minimum and maximum RNFL thickness.

Normative database compared with the patient's age and sex group displayed each quadrant and each sector in four different colors with normal percentile distribution as follows–white: above-average thickness of the RNFL(95–100% of the normal population), green: within normal average(5–95% of the normal population), yellow: borderline thickness of the RNFL(1–5% of the normal population), red: reduced thickness of the RNFL(<1% of the normal population).

Follow-up periods were 3 and 6months by SAP, and OCT assessment of the RNFL was done using the same methods as the baseline.

VFs were assessed using the same method as the baseline. VFs were compared with the previous readings, and progression was defined according to The Collaborative Initial Glaucoma Treatment Study(CIGTS) as follows.

The overall VF defect score is generated from the pattern deviation probability plot values. Any of the test locations on this plot(excluding the two blind-spot locations) for which the probability value is less than or equal 0.5 and which is accompanied by at least two adjacent abnormal points is considered defective and is scored. The score for each location is weighted by the depth of its defect and the depths of the defects of the two most defective neighboring locations(for which P≤0.5).

Each point in the VF is tested separately and given a score. Points with normal threshold sensitivities are given a score of 0. Apoint with reduction in the threshold sensitivity of probability less than 5% but is not surrounded by two or more adjacent points of reduced sensitivity is also given a score of 0.

A point with probability less than 5% surrounded by two or more points of probabilities less than 5% is given a score of 1. Apoint with probability less than 2% with surrounding points of reduced threshold sensitivity of probability at least less than 2% is given a score of 2. Apoint with probability less than 1% with two or more surrounding points of probabilities at least less than 1% is given a score of 3. Similarly, a point with probability less than 0.5% with surrounding points of probabilities less than 0.5% is given a score of 4. Finally, scores of all points are added and divided by 10.4.

RNFL thickness was compared with the previous at every quadrant and sector individually. Progression was defined as a significant reduction in the thickness of the RNFL with or without change in the color of the normal percentile distribution according to the normative database. Achange in RNFL thickness within 7μm between sessions, measured by stratus OCT, was considered as acceptable in terms of test–retest variability, most of which can be attributed to the∼5 μm variability within each session. We considered progression as a reduction in thickness of 8μm or more[7]. Statistical presentation and analysis of the present study was conducted using the mean, SD, χ2, and Student's t-test with a level of significance at 95% by SPSS(SPSS Inc., Chicago, Illinois, USA; version18 software)[8].


  Results Top


This study included 20 eyes of 15patients. Four(26.6%) of them were female and 11(73.4%) were male. Their ages ranged from 45 to 72years, five(33.3%) of them were diabetic, and four(26.6%) were hypertensive. Totally, 60% of our patients had a family history of glaucoma(9/15), with the father being glaucomatous in more than half of them(5/9). All of these patients were diagnosed with POAG; 45%(9/20) of patients had POAG in the right eye, whereas the remaining 55%(11/20) had POAG in the left eye.

The average duration of POAG diagnosis was 24.7+13.52months(mean±SD), ranging between 12 and 48months. All patients were on medical treatment; five(5/20) patients were on combined carbonic anhydrase inhibitor and β-blocker, five(5/20) were on β-blockers, seven(7/20) were on prostaglandins analogs, and three(3/20) were on α-agonists. Seventeen(85%) of those were compliant on treatment and three were not. Among those 20 eyes, two(10%) had prior cataract surgery and two(10%) had prior laser-assisted in situ keratomileusis (LASIK).

On examination, the mean best corrected visual acuity(BCVA) was 20/30+1.4 lines, ranging from 20/50 to 20/20. With regard to the logMAR visual acuity, the mean was 0.19±0.13, ranging from 0.4 to 0.

The anterior segment examination showed a LASIK flap in two(10%) cases; otherwise, the cornea was normal. As regards the lens, two(10%) eyes were pseudophakic and one(5%) had a starting posterior subcapsular cataract. All the remaining 17 eyes had a clear lens.

The mean intraocular pressure was 19.2±2.7mmHg, ranging from 16 to 24mmHg.

Gonioscopy showed an open angle in all cases. According to Shaffer system, four(20%) cases were gradeIV and the remaining 16(80%) cases were gradeIII. No trabecular hyperpigmentation, angle blood vessels, and dandruff material were present.

Fundus examination showed normal macula and retinal periphery in all cases. The mean optic disc vertical cup disc ratio was 0.55±0.11, ranging from 0.4 to 0.8, and the mean horizontal cup disc ratio was 0.565±0.122, ranging from 0.4 to 0.9. Peripapilary changes were present in 13(65%) cases; of these, 54%(7/13) were all around and 46%(6/13) were only temporal. No splinter-shaped disc hemorrhages were present in any case.

Visual field(standard automated perimetry)

The VF testing was reliable in all eyes with a mean test duration of 11:09±2:07min, ranging from 7:09 to 15:48min. The mean for fixation losses, false positive, and false negative values was 8.18±7.31%, 11.84±13.43%, and 9.88±9.41%, respectively.

Glaucoma hemifield test was abnormal in all patients.

The average of mean deviation was 9.58±5.06dB, ranging from 0.54 to 16.49. The loss of variance was 40.17±14.6, ranging from 15.34 to 67.57.

The mean CIGTS VF score at baseline was 3.26±2.27, ranging from 0.5 to 7.78.

The mean values of OCT RNFL parameters at baseline are shown in [Table1].
Table 1: Optical coherence tomography retinal nerve fiber layer parameters at baseline

Click here to view


At 3months, all VF tests obtained were reliable, with fixation losses averaging 7.46±3.4%, false positive 5.6±3.2%, and false negative 6.3±3.6%. The mean test duration was 11.05±1.44min, ranging from 8.07 to 15.23min.

The average of mean deviation was 9.79±5.01dB, ranging from 0.54 to 16.9. The loss of variance was 40.42±13.72, ranging from 15.34 to 73.13.

The mean CIGTS VF score at the 3-month visit was 3.278±2.12, ranging from 1.34 to 8. No patients showed progression by this time.

At 6months

All tests obtained were reliable, with fixation losses averaging 4.74±2.4%, false positive 4.6±3.9%, and false negative 5.3±1.7%. The mean test duration was 10.52±2.4min, ranging from 7.08 to 17.39min.

The average of mean deviation was 10.75±5.15dB, ranging from 3.2 to 17.45. The loss of variance was 49.63±15.88, ranging from 17.87 to 79.42.

The mean CIGTS VF score at the 6-month visit was 4.75±2.86, ranging from 1.34 to 11.15. The scoring for different points is shown in [Table2]. This corresponds to eight eyes showing progression.
Table 2: Collaborative Initial Glaucoma Treatment Study visual field scores at the 6-month visit

Click here to view


In the OCT assessment at the 3-month visit, four(20%) eyes showed progression. Two of those eyes showed progression at the temporal quadrant and two at the superior quadrant.

The mean values of OCT RNFL parameters at 3months are shown in [Table3].
Table 3: Optical coherence tomography retinal nerve fiber layer parameters at the 3-month visit

Click here to view


At the 6-month visit, 10(50%) eyes showed progression. Eight of those eyes showed progression at the temporal quadrant, six at the superior quadrant, six at the nasal quadrant, and four at the inferior quadrant.

The two-tailed P value for mean of average RNFL thickness is 0.009, which is statistically highly significant.

Color-coded percentile distribution of the RNFL thickness based on normative database showed progression in six eyes at the superior quadrant, whereas only six eyes showed progression at the temporal quadrant, two at the nasal quadrant, and two at the inferior quadrant at the 6-month visit.


  Discussion Top


Glaucoma is a progressive condition for which we have no cure; the goal of treatment is to halt or slow the disease's progression. Although some patients can be successfully maintained on the same therapy for years, many others will need more aggressive therapies as their glaucoma worsens. To ensure that the current treatment remains effective, patients must be regularly monitored for disease progression.

Because glaucoma is the second leading cause of blindness in the world, the main goal of glaucoma management is to diagnose this disease when it is asymptomatic. VF testing is essential in the diagnosis and monitoring of glaucoma. However, it is known that standard perimetry cannot detect VF defects until 40–50% of ganglion cells have been lost[9].

Measuring glaucoma progression using VFs is very difficult, even with sophisticated progression software. As many of our glaucoma patients are poor VF testers, subjective analysis of glaucoma progression in these patients is very difficult. The ability to measure RNFL thickness accurately and objectively over time could be a valuable tool in assessing the progression of glaucoma.

In our study, we tried to compare between OCT and perimetry in detecting progression in glaucoma in diagnosed POAG(comparison between OCT and SAP). Follow-up period was 6months in all patients.

Progression by OCT was considered if RNFL thickness decreased from baseline visit more than 8μm in any quadrant to eliminate the factor of test–retest variability, whereas progression by VF was considered if CIGTS score increased from baseline visit by 3 or more. Mean average RNFL thickness and the mean CIGTS score at follow-up visits were also compared with the baseline visit.

In our study, SAP was nearly similar to OCT in detecting progression: eight(40%) eyes compared with 10(50%) eyes by OCT.

OCT was better because of its ability to detect early any progression before functional affection, but the difference between them is not significant.

Ojima etal.[10], Soliman etal.[11], and Kanamori etal. [12] found that OCT has the ability to detect glaucomatous changes by measuring RNFL thickness. Particularly, the average and inferior quadrant and, furthermore, average and quadrant thickness had good correlation with the mean deviation in humphery field analyzer.

Wollstein etal. [13] suggested that OCT is more sensitive(22% progression by OCT compared with 9% progression by SAP), but they could not exclude the possibility of a higher number of OCT-related errors(false positives); in addition, they depended on mean deviation alone in detecting progression in VFs.

Leung etal. [14] revealed similar rate of progression in glaucoma patients between OCT and SAP. One hundred sixteen eyes of 64patients with glaucoma were observed within a period of 5years. Twenty-one and 22 eyes had progression according to RNFL and VF measurements, respectively, and three eyes had progression according to both measurements. However, they differ from our study in using different software(guided progression analysis) in OCT device to detect progression in glaucomatous eyes, in addition to the large number of patients included in the study and the long period of follow-up.

At the 3-month visit, no progression was observed in their VFs, and at the same time OCT showed progression in four(20%) eyes. This is very important, as it emphasizes and confirms the ability of the OCT to detect minimal anatomical damage in the process of the glaucoma disease earlier before functional damage can occur.

Sahli and Tekeli [15] found that there was positive correlation between mean deviation and RNFL thickness in temporal quadrant, 2 and 5 o'clock while there was negative correlation between pattern SD and RNFL thickness global average thickness, RNFL thickness in temporal quadrant and 2 o'clock area in POAG.

Color-coded percentile distribution of the RNFL thickness based on normative database showed low sensitivity in detecting progression in quadrants. This is attributed to the fact that progression could occur, but the remaining RNFL thickness is present within the same range of percentile distribution. On the contrary, changes in RNFL thickness falling within the range of test–retest variability could induce changes in color-coded percentile distribution giving the false impression of progression. This should be taken into consideration while detecting progression over successive OCT results, where the investigator should not rely only on the color-coded percentiles.

The most important and often the most difficult aspect of managing these patients is determining progression. Our study revealed that both OCT RNFL imaging devices and VF testing are useful methods in managing these patients. However, the ability to measure minimal RNFL thinning is an important significant advantage for OCT over VF in this group of patients.


  Conclusion Top


OCT was able to detect more progression compared with VF. In addition, it detected progression earlier compared with VF. OCT proved the ability to detect any structural changes before corresponding functional defects can be detected.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
SpaethGL. Development of glaucomatous changes of the optic nerve. In: VarmaR, SpaethGL, ParkerKW, editors The optic nerve in glaucoma. Philadelphia, PA: Lippincott; 1993. 63–81.  Back to cited text no. 1
    
2.
HoodDC, AndersonSC, WallM, KardonRH. Structure versus function in glaucoma: an application of a linear model. Invest Ophthalmol Vis Sci 2007; 48:3662–3668.  Back to cited text no. 2
    
3.
Garway-HeathDF, CaprioliJ, FitzkeFW, HitchingsRA. Scaling the hill of vision: the physiological relationship between light sensitivity and ganglion cell numbers. Invest Ophthalmol Vis Sci 2000; 41:1774–1782.  Back to cited text no. 3
    
4.
HuangD, SwansonEA, LinCP, SchumanJS, StinsonWG, ChangW, etal. Optical coherence tomography. Science 1991; 254:1178–1181.  Back to cited text no. 4
    
5.
HougaardJL, HeijlA, BengtssonB. Glaucoma detection by StratusOCT. JGlaucoma 2007; 16:302–306.  Back to cited text no. 5
    
6.
BowdC, ZangwillLM, MedeirosFA, TavaresIM, HoffmannEM, BourneRR, etal. Structure-function relationships using confocal scanning laser ophthalmoscopy, optical coherence tomography, and scanning laser polarimetry. Invest Ophthalmol Vis Sci 2006; 47:2889–2895.  Back to cited text no. 6
    
7.
BudenzDL, FredetteMJ, FeuerWJ, AndersonDR. Reproducibility of peripapillary retinal nerve fiber thickness measurements with stratus OCT in glaucomatous eyes. Ophthalmology 2008; 115:661–666.  Back to cited text no. 7
    
8.
GnandesikanR. Methods for statistical data analysis of multivariate observations. NewYork, NY: John Wiley and Sons; 1977. 1–82.  Back to cited text no. 8
    
9.
QuigleyH, AddicsEM. Quantitative studies of retinal nerve fiber layer defects. Arch Ophthalmol 1982; 100:808–814.  Back to cited text no. 9
    
10.
Guedes V, Schuman JS, Hertzmark E, Wollstein G, Correnti A, ManciniR, et al. Optical coherence tomography measurement of macular and nerve fiber layer thickness in normal and glaucomatous human eyes. Ophthalmology 2003; 110:177-89.  Back to cited text no. 10
    
11.
SolimanMA, Van Den BergTJ, IsmaeilAA, De JungLA, De SmetMD. Retinal nerve fiber layer analysis, Relation between optical coherence tomography and red-free photography. Am J Ophthalmol 2002; 133:187–195.  Back to cited text no. 11
    
12.
Kanamori A, Nakamura M, Escano MF, Seya R, Maeda H, Negi A. Evaluation of the glaucomatous damage on retinal nerve fiber layer thickness measured by optical coherence tomography. AM J Ophthalmol 2003; 135:513–520.  Back to cited text no. 12
    
13.
WollsteinG, SchumanJS, PriceLL, AydinA, StarkPC, HertzmarkE, etal. Optical coherence tomography longitudinal evaluation of retinal nerve fiber layer thickness in glaucoma. Arch Ophthalmol 2005;123:464–470. Erratum in: Arch Ophthalmol. 2005; 123:1206.  Back to cited text no. 13
    
14.
LeungCK, CheungCY, WeinrebRN, QiuQ, LiuS, LiH, etal. Retinal nerve fiber layer imaging with spectral-domain optical coherence tomography: a variability and diagnostic performance study. Ophthalmology 2009; 116:1257–1263.  Back to cited text no. 14
    
15.
SahliE, TekeliO. Evaluation of retinal nerve fiber layer thickness with spectral domain OCT in primary open angle glaucoma and ocular hypertension. JClin Exp Ophthalmol 2012; 3:247.  Back to cited text no. 15
    



 
 
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