Year : 2013 | Volume : 1 | Issue : 1 | Page : 12 - 16  

Original Articles
Correlation between Heidelberg Retinal Tomography (HRT II) Parameters and Visual Field Indices in Primary Open Angle Glaucoma Patients

Renu Shukla Dubey1, B.K. Nayak2, Nisheeta Agarwal3

1 Sr Resident, Malla Reddy Insititute of Medical Sciences, Hyderabad, 2HOD and 3 Consultant Ophthalmologist, P.D.Hinduja National Hospital, Mumbai.



Background: Glaucoma is a common cause of visual impairment and blindness. The Heidelberg Retinal Tomogram (HRT) evaluates the structural details of the optic disc and has been widely investigated as a research tool in imaging of the ONH. The correlation between the perimetry and HRT data in Caucasian eyes has been reported previously. Objective: To correlate the HRT parameters and visual field indices in Indian eyes including established glaucoma and glaucoma suspect patients. Methods: Eighty-three eyes of 50 patients having primary open angle glaucoma underwent automated Humphrey perimetry (30-2) and confocal scanning laser ophthalmoscopy (HRT II). The global visual field indices and the HRT II parameters were correlated. Results: The average MD of the study group was –3.70 ± 3.99dB (range 1.11 to –19.54). The correlations between global parameters by HRT and global visual field indices were found to be significant for rim area, rim volume, height variation contour, mean RNFL thickness and found RNFL cross sectional area. The strongest correlation was between rim area and PSD (r = 0.32, p = 0.0029). Conclusion: There was a good correlation between global visual field indices and HRT II parameters with highest correlation coefficient of 0.32. Since we had several parameters correlating well, we can say that in early glaucomatous damage HRT II is as sensitive as perimetry and HRT II could be a useful tool in evaluation and diagnosis of glaucoma.

 KEYWORDS: Glaucoma, Heidelberg Retinal Tomography, visual field indices

Corresponding Author: Dr. Renu Shukla Dubey, 7-1-215/C/1/B, Dudey Nivas, Balkampet, Hyderabad-500016. Email id :



Glaucoma is a common cause of visual impairment and blindness. Primary open angle glaucoma (POAG) is a chronic progressive optic neuropathy with characteristic optic nerve head (ONH) findings and visual field loss with various risk factors including raised intraocular pressure (IOP).

It has been widely accepted that changes in the ONH may precede the detectable field loss in early glaucoma. [1-6] Controlling the IOP at an early stage in glaucoma has been shown to slow down/stop progression of the disease. [7, 8]

Standard automated perimetry (SAP), which tests the functional aspect of the optic nerve fibres, has good diagnostic precision for glaucoma [9, 10] but is not specific for glaucoma. The Heidelberg Retinal Tomogram (HRT) evaluates the structural details of the optic disc and has been widely investigated as a research tool in imaging of the ONH. [11, 12] Several studies have demonstrated that the HRT may be used to differentiate between normal and glaucomatous eyes. [13-17] The correlation between the perimetry and HRT data in Caucasian eyes has been reported previously. [18-25]

We investigated the correlation between HRT parameters and visual field indices in Indian eyes.


Material and Methods

Eighty-three eyes of 50 consecutive patients with POAG, established glaucoma as well as glaucoma suspect who attended the outpatient department at P.D.Hinduja Hospital were included in the study. All patients underwent a complete ophthalmological examination including abbreviated medical history, full ocular history, vision, slitlamp biomicroscopy, applanation tonometry, gonioscopy, and dilated fundus examination. Automated achromatic perimetry (Humphrey perimetry 30-2 full threshold) and confocal scanning laser tomography of the optic disc using HRT II. (Software version, Heidelberg Engineering, Heidelberg, Germany) were also performed. The sample size was worked out to be 75 using a error of 0.05 (5%) and b error of 0.2 (80% power).

The inclusion criteria were, age ³ 40 years, refractive error, spherical £ ±5.0 dioptre (D), cylinder £ ±3.0 D, IOP ³ 21 mmHg (measured on two or more occasions) AND/OR disc changes suggestive of glaucoma (CDR ³ 0.5/difference in CDR³0.2 of both eyes, open angles on gonioscopy, ≥ 2 reliable visual fields and good quality HRT images. The exclusion criteria were optic nerve / retinal disease that cause visual field defects, history of ocular trauma and intraocular surgery.

The patients were diagnosed as “established glaucoma” who had the abnormal visual fields according to the ‘Anderson’s criteria’ [26]

The patients were diagnosed as “glaucoma suspects” [27] who had normal visual field but either had a IOP³21 or CDR³0.5/difference in CDR³0.2 of both eyes.

Humphrey field analyzer:

Achromatic automated perimetry was performed using 30-2 Full threshold strategy. A glaucomatous field loss was defined as, (i) A cluster of 3 or more non-edge points with p<5% on pattern deviation plot with one point having p<1% AND (ii) Glaucoma hemifield test (GHT) outside normal limits. The reliability parameters for visual fields were fixation losses <20%, false positive and false negative responses <25%. Patients showing ≥ 2 reliable visual fields were included in the study.

Confocal scanning laser ophthalmoscope:

The HRT uses a diode laser (wavelength 670nm) to scan the retinal surface in three dimensions. A topographic image is usually taken as a series of 32 confocal images at 32 consecutive focal planes, each consisting of 256 x 256 pixels.    

Laser scanning tomography was performed with HRT on the same day as perimetry. Images were obtained by one of the two trained technicians. Before each measurement, the subject’s corneal curvature radius was entered into the software. The patient’s face was then gently placed onto the head-and-chin rest of the HRT, and imaging was performed at the 1.5-cm imaging head–eye distance recommended in the instruction manual, as the subject viewed a distant fixation target. Three 10° field images were obtained for each eye through (3mm diameter pupil.

The mean topography of the three images was generated and the contour line was drawn to outline the disc margin along the inner edge of the peripapillary scleral ring of Elschnig. Mean images with a mean SD of the height measurements >50 µm were excluded from analysis.

The HRT software automatically calculates several stereometric parameters: cup area, disc area, cup disc area ratio, cup volume, rim volume, cup shape measure, maximum cup depth, height contour, mean RNFL height, RNFL cross sectional area globally and in the six segments of optic disc.

HRT classifies a given eye as Normal, Borderline or Abnormal based on a discriminant function elaborated by Mikelberg et al. [28]

Data analysis:

The visual field indices and HRT parameters were entered in the excel sheet. Pearson’s correlation coefficient was used to assess the correlation between mean deviation (MD), pattern standard deviation (PSD) and each of HRT parameters. A statistically significant association was taken when the p value was £ 0.05.


Table 1: Age demography


No. of patients











The study enrolled eighty-three eyes of 50 patients with established glaucoma and glaucoma suspects. The age of the patients ranged from 40-73 years, mean 53.18+9.34 years. The age demography is shown in table 1. The male: female ratio was 32:18.


Table 2: Distribution based on MD values


No. of eyes

> - 6 (mild)


-6 to -12 (moderate)


< -12 (severe)



Glaucoma suspect eyes = 53, glaucoma eyes = 30. Mean IOP was 20.43± 4.68 mmHg. Based on MD values, 65 eyes had mild damage (MD > 6 db), 15 eyes had moderate damage (MD 6 to –12) and 3 eyes had severe damage (MD < -12) as shown in table 2.

The mean global visual field indices and global topographical parameters by HRT are shown in Table 3. The average MD of the study group was –3.70 ± 3.99dB (range 1.11 to –19.54).

The correlations between global parameters by HRT and global visual field indices were performed and found to be significant for rim area, rim volume, height variation contour, mean RNFL thickness and found RNFL cross sectional area as shown in table 4.

Rim area (figure 1), rim volume (figure 2) and RNFL cross sectional area (figure 3) were correlated to both MD and PSD.

Height variation contour and mean RNFL thickness were correlated to MD.


Table 3 : shows the mean HRT and visual field parameters.










Cup area



Rim area









Disc area



Cup volume



Rim volume



mean cup depth



max cup depth



ht variation contour



Cup shape measure



mean RNFL



RNFL csa



*MD-mean deviation, PSD-pattern standard deviation, CDR-cup disc ratio

RDR-rim disc ratio, RNFL-retinal nerve fibre layer, csa-cross sectional area.


The strongest correlation was between rim area and PSD (r = 0.32, p = 0.0029) also shown in figure 4.




The Humphrey perimetry is presently the gold standard in the diagnosis of glaucoma but as reported earlier clinically detectable glaucomatous changes in the optic disc may precede the onset of white on white visual field defects. [1-6] Presence of even an early field defect on standard automated perimetry is considered moderate glaucoma. [29]

The introduction of HRT is helpful for evaluating and monitoring the optic disc quantitatively. The HRT provides us with quantitative optic nerve head parameters that have been shown to be highly reproducible. [12, 30] A number of previous studies have examined the correlation between the HRT parameters and visual field indices. [18-25] They included cup area, CDR, rim area, rim volume, cup shape measure, RNFL thickness, and RNFL cross section area. The correlations were better for MD than PSD/CPSD.


TABLE 4: Correlation of HRT parameters and visual field indices







Cup area

- 0.0714


Rim area




- 0.1410




- 0.1783  

Disc area


- 0.1262  

Cup volume

- 0.0776


Rim volume



Mean cup


- 0.0494


Max cup




Ht variation



- 0.1904

Cup shape


- 0.1807




- 0.1813

RNFL csa



 *p< 0.05 , CDR – cup disc ratio, RDR- rim disc ratio, RNFL- retinal nerve fibre layer, csa- cross sectional area


In our study involving Indian eyes, there was statistically significant correlation between several structural ONH parameters and the visual field indices. The strongest correlation was found between rim area and PSD. Similar results have been reported by Iester et al. who showed the rim area to be an important predictor of MD and CPSD. [19] More correlations were found between MD and HRT parameters as shown in table 5.

Tole et al. [22] found all the significant correlations disappeared when analysis was confined to the glaucoma patients with MDs of < -10 dB. They supposed that it could be due to the statistical effect of reducing the numbers from 106 eyes to 61 eyes. However, relations between topographic parameters and MD were found with smaller sample size (47) in other studies. [19]

Our study included only glaucoma (established and suspects) patients. As mentioned before, the correlations were better for combined groups because of the larger range of values. Thus even though there were several parameters correlating significantly, we found lower correlation coefficient as compared to other studies (maximum r = 0.3233).

The visual field defects in our study were less severe as compared to other studies. Mean MD in our study was –3.70


Table 5 : Comparision of HRT and visual field parameters in various studies




Average MD



HRT --   Visual field



Iester et al.36


- 4.0

Rim area       MD                                                                                            


CSM           MD






Brigatti et al.37


- 4.8

CSM           MD




Eid et al.35


- 7.5

RNFLT       MD

CDAR           MD



Teesalu et al.38


- 3.5

CSM             MD

RNFLT         MD



Tsai et al.40


- 3

Rim area       MD


Lan et al.42


- 5.77

Rim area       MD


Our study


- 3.7

Rim area       MD




 * MD- mean deviation, CPSD- corrected pattern standard deviation, CSM-   cup shape measure, RNFLT- retinal nerve fibre layer thickness, CDAR- cup disc area ratio, PSD- pattern standard devation


(± 3.99) dB. Only three eyes (2.5%) had MD worse than - 12dB. In previous studies mean MD ranged from - 6 to - 10 Db [18, 19, 22]   with a higher percentage of glaucoma patients with MD worse than - 20 dB (11.5%, [18] 7.5% [22].

In our study we had 65 eyes with mild glaucomatous damage (MD > -6 dB), which means maximum patients had early glaucomatous changes and we found statistically significant correlations between HRT II and visual fields (strongest correlation between PSD and rim area). This suggests that this parameter (rim area) may be studied in detail to diagnose preperimetric glaucoma.

From the scatter plots, we noticed that advanced glaucoma patients had a large influence on the relation between topographic parameters and visual field indices. Since our study had only three advanced glaucoma patients, there were not many high associations. Teesalu et al. [21, 24] had supported this finding. Their scatter plots also showed that the advanced glaucoma patients played an important role in establishing an association.

Few factors can affect the correlation between structural damage and functional damage. Statistically speaking, the sample size and the characteristics of subjects affect the final result. Larger sample sizes and a larger range of values contribute to a better correlation. Thus different studies may get different results because of different sample sizes and different inclusion criteria.

There are few factors which cause a large individual variation in the relations between topographic and visual field indices. First reason being a large variation of these parameters within the normal population. The other is individual difference in the amount of RNFL damage necessary for visual field loss to occur. Bartz- Schmidt et al [31] showed that the amount of rim area loss for certain degree of visual field loss differs for every individual. Therefore, it would be better to evaluate the correlation between optic disc changes and visual field changes by longitudinal study, instead of a cross sectional

data. Thus longitudinal studies that establish the value of HRT in detecting progression, and the expected stronger correlation between the structural changes and functional changes may establish the role of HRT in early diagnosis of glaucoma.

The HRT gives quantitative, rapid and objective measurements of ONH that may be useful for diagnosis and follow up. [30, 32-34] The examination procedure is objective, fast and simple. There are fewer restrictions with respect to pupil size, co-operation of patient and cataract status.

HRT does not provide some important information about the optic disc like, rim pallor, disc haemorrhage, alterations of lamina cribrosa and vessels. Thus clinical evaluation considering all these factors is essential. Nevertheless, the quantitative measurements from HRT assist the clinical judgement for early diagnosis and detection of progression.

The visual field test is more time consuming and depends upon the patient’s responses. Thus it would be better if we could predict the visual function from the optic disc morphology. For evaluation and follow-up of glaucoma patients, a close comparison between optic nerve head parameters and visual field defects is required. The problem of individual variation has to be dealt with by using appropriate parameters.

In our study we found correlation between global visual field indices and HRT II parameters in Indian eyes in established glaucoma as well as glaucoma suspects. This can be studied in further detail by evaluating preperimetric glaucoma patients in a longitudinal study to establish progression structurally and functionally. With this study we conclude that HRTII can be used clinically for diagnosis of glaucoma patients.




  1. Quigley HA, Dunkelberger GR, Green WR. Retinal ganglion cell atrophy correlated with automated perimetry in human eyes with glaucoma. Am J Ophthalmol 1989;107:453-64.
  2. Pederson JE, Anderson DR. The mode of progressive disc cupping in ocular hypertension and glaucoma. Arch Ophthalmol 1980;98:490-495.
  3. Caprioli J. Correlation of visual function with optic nerve and nerve fiber layer structure in glaucoma. Surv Ophthalmol 1989;33:319-330.
  4. Zeyen TG, Caprioli J. Progression of disc and field damage in early glaucoma. Arch Ophthalmol 1993;111:62-65.
  5. Funk J. Early detection of glaucoma by longitudinal monitoriong of the optic nerve disc structure. Graefe’s Arch Clin Exp Ophthalmol 1991; 229:57.
  6. Sommer A,Katz J,Quigley HA, Miller NR, Robin AL, Richter RC et al. Clinically detectable nerve fiber atrophy precedes the onset of glaucomatous field loss. Arch Ophthalmol 1991;109:77-83
  7. Mao LK, Stewart WC, Shields MB. Correlation between intraocular pressure control and progressive glaucomatous damage in primary open-angle glaucoma. Am J Ophthalmol 1991;111:51-55.
  8. Chauhan BC, Drance SM. The relationship between intraocular pressure and visual field progression in glaucoma. Graefes Arch Clin Exp Ophthalmol 1992;230:521-526.
  9. Harper RA, Reeves BC. Glaucoma screening: the importance of combining test data. Optom Vis Sci 1999;76:537-43.
  10. Sponsel WE, Ritch R, Stamper R, Higginbotham EJ, Anderson DR, Wilson MR et al. Prevent Blindness America visual field screening study. Am J Ophthalmol 1995;120:699-708.
  11. Cioffi GA, Robin AL, Eastman RD, Perell HF, Sarfarazi FA, Kelman SE. Confocal laser scanning ophthalmoscope. Reproducibility of optic nerve head topographic measurements with the confocal laser scanning ophthalmoscope. Ophthalmology 1993;100:57-62.
  12. Rohrschneider K, Burk ROW, Kruse FE, Völcker HE. Reproducibility of the optic nerve head topography with a new laser tomographic scanning device. Ophthalmology 1994;101:1044-9.
  13. Mikelberg FS, Parfitt CM, Swindale NV, Graham SL, Drance SM, Gosine R. Ability of the Heidelberg retina tomograph to detect early glaucomatous field loss. J Glaucoma 1995;4:242-7.
  14. Zangwill LM, van Horn S, De Souza Lima M, Sample PA, Weinreb RN. Optic nerve head topography in ocular hypertensive eyes using confocal scanning laser ophthalmoscopy. Am J Ophthalmol 1996;122:520-5.
  15. Uchida H, Brigatti L, Caprioli J. Detection of structural damage from glaucoma with confocal laser image analysis. Invest Ophthalmol Vis Sci 1996;37:2393-2401.
  16. Hatch WV, Flanagan JG, Etchells EE, Williams Lyn DE, Trope GE. Laser scanning tomography of the optic nerve head in ocular hypertension and glaucoma. Br J Ophthalmol 1997;81:871-6.
  17. Wollstein G, Garway-Heath D, Hitchings R. Identification of early glaucoma cases with the scanning laser ophthalmoscope. Ophthalmology 1998 Aug;105(8):1557-63
  18. Eid TM, Spaeth GL, Katz LJ, Azuara-Blanco A, Aqusburger J, Nicholl J. Quantitative estimation of retinal nerve fiber layer height in glaucoma and the relationship with optic nerve head topography and visual field. J Glaucoma 1997;6:221–30.
  19. Iester M, Mikelberg FS, Courtright P, Drance SM. Correlation between the visual field indices and Heidelberg retina tomograph parameters. J Glaucoma 1997;6:78–82.
  20. Brigatti L, Caprioli J. Correlation of visual field with scanning confocal laser optic disc measurements in glaucoma. Arch Ophthalmol 1995;113:1191–4.
  21. Teesalu P, Vihanninjoki K, Airaksinen PJ, Tuulonen A, Läärä E. Correlation of blue-on-yellow visual fields with scanning confocal laser optic disc measurements. Invest Ophthalmol Vis Sci 1997;38:2452–9.
  22. Tole DM, Edwards MP, Davey KG, Davey KG, Menage MJ. The correlation of the visual field with scanning laser ophthalmoscope measurements in glaucoma. Eye 1998;12:686–90.
  23. Tsai CS, Zangwill L, Sample PA, Garden V, Bartsch DU, Weinreb RN. Correlation of peripapillary retinal height and visual field in glaucoma and normal subjects. J Glaucoma 1995;4:110–6.
  24. Teesalu P, Vihanninjoki K, Airaksinen PJ, Tuulonen A. Hemifield association between blue-on-yellow visual field and optic nerve head topographic measurements. Graefes Arch Clin Exp Ophthalmol 1998;236:339–45.
  25. Y-WLan, DBHenson, AJKwartz. The correlation between optic nerve head topographic measurements, peripapillary nerve fibre layer thickness, and visual field indices in glaucoma. J. Ophthalmol., Sep 2003; 87: 1135 - 1141.
  26. Anderson DR. Automated Static Perimetry. St Louis: Mosby-Year Book, 1992.
  27. American Academy of Ophthalmology. Primary Open Angle Glaucoma Suspect, Preferred Practice Pattern ; San Francisco : American Academy of Ophthalmology, 2005.
  28. Mikelberg FS, Parfitt CM, Swindale NV, Graham SL, Drance SM, Gosine R, et al. Ability of the Heidelberg retina tomograph to detect early glaucomatous field loss. J Glaucoma 1995;4:242-47.
  29. American Academy of Ophthalmology preferred practice committee glaucoma panel. Primary open angle glaucoma. San Francisco, Caliph: American Academy of Ophthalmology;1996.
  30. Janknecht P, Funk J. Optic nerve head analyser and Heidelberg retina tomograph: accuracy and reproducibility of topographic measurements in a model eye and in volunteers. Br J Ophthalmol. 1994 Oct;78(10):760-8.
  31. Bartz-Schmidt KU, Thumann G, Jonescu-Cuypers CP, Krieglstein GK. Quantitative morphologic and functional evaluation of the optic nerve head in chronic open angle glaucoma. Surv Ophthalmol 1999;44:S41-53.
  32. Weinreb RN,Lusky M. Effect of repetitive imaging on topographic measurements of the optic nerve head. Arch Ophthalmol. 1993 May;111(5):636-8.
  33. Kruse FE, Burk RO, Völcker HE, Zinser G, Harbarth U. Reproducibility of topographic measurements of the optic nerve head with laser tomographic scanning. Ophthalmology 1989 ;96:1320-4.
  34. Chauhan BC, LeBlanc RP, McCormick TA, Rogers JB. Test-retest variability of topographic measurements with confocal scanning laser tomography in patients with glaucoma and control subjects. Am J Ophthalmol 1994;118:9-15.


I would like to express my deep gratitude, towards my guide and mentor Dr.Barun Kumar Nayak, who has been a constant source of inspiration, the one who motivated me to give my best all along.

I would also like to thank Dr. Nisheeta Agarwala, Dr. Sunil Moreker, Dr.Ashwin Sainani and Dr. Preetam Samant for their help and support.


Source of support: Nil.

Conflict of interest: Not Declared








Important links

adv apply rec

Open Access Journal

MRIMS Journal of Health Sciences is an open access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher of the author. This is in accordance with the BOAI definition of open access.

Visitor Count

© 2017 Chandramma Education society . All Rights Reserved.