Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 
  • Users Online: 3639
  • Home
  • Print this page
  • Email this page

   Table of Contents      
ORIGINAL ARTICLE
Year : 2003  |  Volume : 51  |  Issue : 1  |  Page : 25-33

The normal optic nerve head on heidelberg retina tomograph II.


Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, Ansari Nagar, New Delhi, India

Correspondence Address:
Harish C Agarwal
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, Ansari Nagar, New Delhi
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


PMID: 12701859

Rights and PermissionsRights and Permissions
  Abstract 

Purpose: To study the characteristics of the optic nerve head using a scanning laser ophthalmoscope, the Heidelberg Retina Tomograph II (HRT II), in a normal population and to determine the specificity of HRT II diagnostic indices in the study population.
Methods: The optic nerve heads from 275 consecutive, randomly selected normal subjects were imaged on HRT II. Stereometric parameters were studied with respect to baseline variables such as age, gender, refractive error and disc size. The stereometric parameters and the results of Moorfields regression analysis (MRA) and discriminant function analysis were recorded.
Results: The average disc size in the population under study was 2.34 + 0.47 mm[2]. Age and gender had no significant effect on stereometric parameters. Myopic discs were larger than hypermetropic discs. MRA had a specificity varying between 85.5% and 98.2% depending upon the criteria used to define an abnormal disc. The specificity of MRA decreased with increasing disc size. The RB (R Bathija) and FSM (F S Mikelberg) discriminant functions had specificities of 96.4% and 87.3% respectively.
Conclusions: Estimation of stereometric parameters of a normal disc can be used to indicate an abnormal one. Moorfields regression analysis and discriminant functions have a high specificity in our normal population; however, caution must be exercised in interpreting the results for a disc area larger than 3 mm 2.

Keywords: Optic disc, scanning laser tomography, Heidelberg Retina Tomograph II


How to cite this article:
Agarwal HC, Gulati V, Sihota R. The normal optic nerve head on heidelberg retina tomograph II. Indian J Ophthalmol 2003;51:25-33

How to cite this URL:
Agarwal HC, Gulati V, Sihota R. The normal optic nerve head on heidelberg retina tomograph II. Indian J Ophthalmol [serial online] 2003 [cited 2020 Apr 5];51:25-33. Available from: http://www.ijo.in/text.asp?2003/51/1/25/14741



Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view


Click here to view
Distinguishing a normal from a glaucomatous optic nerve head is essential for making a diagnosis of glaucoma. Several characteristics of a glaucomatous optic nerve head have been described in the literature, [1],[2],[3],[4],[5] but the distinction between normal and glaucomatous still remains a matter of subjective clinical judgment. The scanning laser ophthalmoscopy is a recent advance that helps in an objective diagnosis of glaucomatous optic neuropathy.[6],[7],[8] The attendant software has several inbuilt diagnostic indices like discriminant functions[9], [10] and regression analysis[11] to aid the clinician in the diagnosis of glaucoma. These functions provide a diagnostic label based on a statistical comparison with a normative database. The HRT II also provides stereometric measurements of the optic nerve head. However, at present there is no inbuilt database of normal values for each of these parameters. A description of normal values of various parameters is essential for evaluating the utility of these parameters in the diagnosis of glaucoma. The measurements of the optic nerve head vary with the technique used for the purpose.[12],[13] Even the equations used for diagnostic functions may differ with the population used as a database. It would therefore be preferable to use equations and functions derived from a normative population as close as possible to the population for which the instrument is to be used. To the best of our knowledge there is no reported data on the scanning laser ophthalmoscopic optic nerve head characteristics of Indian eyes. To address this gap, we report a description of the normal optic nerve head based on HRT II measurements.


  Materials and Methods Top


The subjects were healthy volunteers, non-blood related patient attendants and patients reporting for eye evaluation with complaints like refractive errors, presbyopia, etc., without a diagnosis of glaucoma. Informed consent was obtained from all volunteers. All subjects underwent anterior segment slitlamp examination, Goldmann applanation tonometry, and stereoscopic fundus examination by a 90D lens and slitlamp to exclude any posterior segment pathology. Patients with a history of ocular trauma, intraocular surgery, posterior segment pathology, or a family history of glaucoma were excluded from the study.

In cases where the results from this examination were within normal limits (i.e. IOP < 21 mm Hg, and no anterior or posterior segment pathology), refraction (Retinomax 2 auto refractor, Nikon Corp., Japan) and automated visual field examination (Humphrey visual field analyser, Model 745, Humphrey Instruments; full threshold program 30-2) were done. An abnormal visual field was defined as one with any of the following criteria.[14] pattern deviation plot showing a cluster of 3 or more non-edge points at an expected location that have sensitivities occurring in fewer than 5% of the normal population (p<5%), with one of these points with a sensitivity in fewer than 1% of the population (p<1%); corrected pattern standard deviation (CPSD) with p<5%; and glaucoma hemifield test outside normal limits. An unreliable visual field was defined as one with any flagged reliability indices (false negatives>33%; false positives>20% or fixation losses>20% outside normal limit). Cases with abnormal or unreliable visual fields were tested repeatedly, till two successive reliable and normal visual fields were obtained. Cases with abnormal or consistently unreliable visual fields were excluded from the study.

Subjects with intraocular pressure (IOP) less than 21 mm Hg, normal visual fields and no risk factors[15] for glaucoma underwent scanning laser ophthalmoscopy on Heidelberg Retina Tomograph II (Heidelberg Engineering, GmBH, Germany). As in previous studies, the optic nerve head appearance was not a part of the inclusion criteria.[9],[10],[11]

The optic nerve head of every eye was imaged using (software version 1.6.0). All images were captured by a single experienced observer (VG) at an imaging head eye distance of 10 mm, with the patient fixating at the internal fixation target of the instrument that automatically centers the optic nerve head image on the screen. The pupil size of all subjects was at least 3 mm. The observer was provided with the subject's refractive error. A rough setting of the examined eye's refraction (spherical equivalent) was done with subsequent fine-tuning to obtain a clear image with the lowest achievable camera sensitivity. Image acquisition was done using a foot pedal to avoid any inadvertent shift in the position of the camera relative to the patient's eye. In the HRT II, the size of the field of view is fixed at 15 degrees, at a resolution of 10 µm per pixel. The correct settings of the focal plane, scan depth, and sensitivity, are done automatically during image acquisition. Upon pressing the image acquisition button, the camera performs an automatic pre-scan of 4 to 6 mm depth. From the images obtained in this pre-scan, the software computes and automatically sets the correct location of the focal plane, the required scan depth for that eye, and the proper sensitivity to obtain images with correct brightness. The system automatically acquires 3 three-dimensional images with the pre-determined acquisition parameters. Sixteen images per mm scan depth are acquired and digitisation is done in frames of 384 x 384 pixels. Three acquired image series were saved on the hard disk and the three topography images, as well as the mean topography image, were computed. In case of a problem with the image acquisition process (namely, scan depth too high, overexposed series, empty series, blink or loss of fixation and wrong focus), the image was not saved on the hard drive. The image acquisition process took approximately five seconds.

Topography was computed using the software. At the same time, the contour line was plotted on the image with the agreement (100%) of two experienced observers (HCA, RS) based on stereoscopic examination of the disc. The stereometric parameters and the results of Moorfields regression analysis (MRA) and discriminant functions were recorded.

Each image is marked with sensitivity and a value of SD in microns which indicates the standard deviation of the measurements in the computed topography out of the three image series, this is henceforth referred to as TSD (topography standard deviation) to prevent confusion with the other calculated standard deviations. The sensitivity and TSD values were recorded for each of the images saved. With regard to the quality of image acquired on HRT II, a TSD up to 40 microns is deemed acceptable.

After an image was recorded on the HRT II, any suspicious looking optic nerve heads (any sector borderline or worse on MRA) were further evaluated including gonioscopy, diurnal variation of IOP and shortwave automated perimetry. None of the 40 cases evaluated in this manner were found to have glaucoma, in the opinion of two glaucoma experts (HCA, RS) (agreement 40/40 for a forced choice between glaucoma and normal). As though both eyes were imaged on HRT II for all cases, the eye with a better image quality as determined by the TSD of the image was included for analysis.


  Results Top


Three hundred consecutive volunteers were enrolled in the study. Thirteen subjects had consistently unreliable or abnormal visual fields and were thus excluded. A total of 574 eyes of 287 subjects were imaged on HRT II. The eye with a better image quality was used for further analysis. Twelve cases had a TSD higher than 40 microns in either eye and were excluded from further analysis. Thus, a total of 275 eyes were used in the final analysis. The mean age of the subjects was 42.06 + 12.38 years (range 4-75 years). The mean TSD of the images was 15.37 + 6.26 microns (range 7-40 microns). Ninety-one volunteers were emmetropic; 72 subjects had hypermetropia less than or equal to 3D; and 9 subjects had hypermetropia more than 3D. Eighty subjects had myopia less than or equal to 3D and 23 subjects had myopia more than 3D. The range of refractive error in the study population was -10D to +6D. The sample population comprised 103 females and 172 males.

[Table - 1] lists the mean values of the HRT II stereometric parameters in the 275 normal eyes used for final analysis. The average disc area in the sample population was 2.34 + 0.47 mm 2. The disc area had a normal distribution in the sample population [Figure - 1]. The average horizontal cup-disc ratio (0.48 + 0.19) was higher than the average vertical cup-disc ratio (0.36 + 0.22).

The software on HRT II incorporates Moorfields regression analysis (MRA), which is a comparison of the subject's rim area to a predicted rim area for a given disc area, based on a regression line derived from normals.[11] If the actual neuroretinal rim area is at least equal to the lower 95% confidence interval limit, the corresponding sector is classified as "within normal limits" (WNL) and is identified by a green check mark. If the actual neuroretinal rim area is between the lower 95% and 99.9% confidence interval limit, then the corresponding sector is classified as "borderline" (BL) and is identified by a yellow exclamation mark. If the actual neuroretinal rim area is less than the lower 99.9% confidence interval limit, then the corresponding sector is classified as "outside normal limits" (ONL) and is marked by a red cross. [Table - 2]a is a compilation of MRA results for the sample population in each of the predefined sectors. [Table - 2]b lists the number of optic nerve head sectors that were either borderline or outside normal limits on MRA. Of the sample population 98.2% eyes had a MRA result that was not outside normal limits (either WNL or BL) and 85.5% population had a MRA result that was within normal limits.

Cases with any sector BL or ONL were considered false positives and cases with a WNL result of MRA were considered true negatives. The false positives were compared to the true negatives for differences in age, refraction and disc size. The average disc size of false positive cases (2.68 + 0.46 mm 2) was significantly higher (p<0.01) than that the true negatives (2.28 + 0.44 mm 2) [Table - 3]. Also, the false positive rate was seen to progressively increase with increasing disc size, amounting to 14.5% for the entire population [Figure - 2].

The HRT II software also provides two discriminant functions as part of the diagnostic battery for glaucoma.[9],[10] Positive values of the discriminant function are considered normal and negative values are considered abnormal. The false positive rate for FSM discriminant function, (i.e., normals with a negative value of the discriminant function) was 12.7% (35 of 275). The false positive rate for RB (R Bathija et al[9]) discriminant function was 3.6% (10 of 275). For disc sizes below 2.25 mm 2, the false positive rate was below 5% for any criteria used to define an abnormal optic nerve head [Figure - 2]. The false positive rate for (FSM) (FS Mikelberg et al[10]) discriminant function also increased with increasing disc size. The effect of increasing disc size was least for RB discriminant function. All other criteria had a consistent rise in false positive rates with increasing disc size. For smaller discs "global borderline" MRA result had a higher specificity than the RB discriminant function, whereas for larger discs RB discriminant function had a higher specificity than "global borderline" MRA result. The specificity of the two methods is identical at a disc area cutoff of 2.75 mm 2 (96.8%).

The stereometric parameters were compared between myopes and hypermetropes [Table - 4]. Myopes had a larger disc size as compared to hypermetropes. The myopes also had a larger rim and cup area, though the difference in cup/disc area ratio between myopes and hypermetropes did not reach statistical significance. The horizontal and vertical cup-disc area ratios also showed a similar pattern with the average values in myopes exceeding those of hypermetropes by 0.08.

Stereometric parameters of males and females were compared [Table - 5]. The difference in the means was not significant for most parameters. The effect of age on stereometric parameters was studied using Pearson's coefficient of correlation [Table - 6]. Except for average variability and FSM discriminant function, none of the parameters were significantly correlated with age.


  Discussion Top


Damage to the optic nerve head is central to the glaucomatous process. Several investigational modalities like scanning laser ophthalmoscopy target changes in the optic nerve head. A description of the optic nerve head parameters may be specific to the population under study and the method of optic nerve head examination. To the best of our knowledge this is the first report of scanning laser ophthalmoscopic measurements in Indian eyes, (Medline search).

The mean disc area in our sample population (2.34 + 0.47mm[2]) is comparable to those reported previously. However, some earlier studies had significant differences in stereometric parameters as compared to our study. A summary of some of the previous reports on the optic nerve head size in normal individuals is provided in [Table - 7].[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26] The disc size measured in our study was significantly smaller than in previous reports using planimetry for the purpose.[16], [20], [26] The difference could be because of a different population or a different method of examination used for the purpose of the study.[12], [13]

The MRA[11] fared well in terms of specificity in our normative database. A specificity ranging between 85.5% and 98.2% could be obtained depending on the criterion used for an abnormal disc. Another interesting observation was the fact that specificity decreased with increasing disc size. Out of the 40 eyes with disc size greater than 3 mm, 2 ten had at least one borderline sector on MRA. This false positive rate was almost double that among those with disc size below 3 mm 2. The pattern was seen irrespective of the criterion used for an abnormal MRA result. Among the three criteria used (one sector BL, two sectors BL and global BL), the lowest rates of false positive were seen when an abnormal optic nerve head was defined as one with global MRA results as borderline. The clinical application of the above is that an outside normal limits MRA is more significant in a smaller disc than in a larger disc. RB discriminant function, which was least affected by increasing disc size, may be more useful than the MRA for individuals with larger discs.

As seen from the scatter plot between disc area and rim area, the scatter of data increases with increasing disc size [Figure - 3]. It is possible that this may result in a certain percentage of cases falling outside the statistical normal range and appear as false positives.

In a comparison with hypermetropes, myopes had larger discs and consequently larger rims and cups. A myopic cup was deeper with higher cup- disc ratios. In addition, the myopic age group was significantly younger (P = 0.00) than the hypermetropic group. This could be a chance occurrence though the statistical probability of the same was low.

Similar to some of the previous studies,[23],[27],[28],[29],[30] we observed no correlation of age with most of the stereometric parameters. Most importantly, we did not observe a correlation of rim area with age. This is in seeming contradiction to the equation used by the MRA where age is among factors used to predict the rim area. It is possible that the effect of age, which is expected to manifest as decreasing rim area, may in turn be a consequence of a hypermetropic shift with age. A hypermetropic shift with age will also result in smaller rim areas as recorded on HRT II. This indicates that a correction for refractive error over and above the one used by the instrument may result in better definition of the parameters in question.

The Moorfields' regression analysis equation was:

Rim area = 1.021 + 0.443 (disc area) - 0.006 (age).

The corresponding equation for our sample population calculated using linear regression analysis was:

Rim area = 0.836 + 0.374 (disc area)

[standard error = 0.081]

Unlike the Moorfields study a significant correlation between age and rim area was not found (r = 0.015; p = 0.801). However, a significant correlation was seen to occur between refractive error and disc area (-0.190; p = 0.002) that persisted even after adjusting for age (r = -0.208; p = 0.000). If we were to include a correction for refractive error, the linear regression analysis equation would be:

Rim area = 0.860 + 0.361(disc area) - 0.015 (focus) [standard error = 0.082]

There was no significant difference for most parameters between males and females. This substantiates a previous study by Varma et al.[23] To summarise, the normal values of HRT II stereometric parameters have been reported for the Indian population. The Moorfields regression was applicable to the normal population with a high degree of specificity. The specificity was lower for larger discs, which may be associated with a myopic refractive error. Further studies in the Indian population using larger sample sizes may help substantiate our results.

 
  References Top

1.
Caprioli J. Clinical evaluation of the optic nerve in glaucoma. Trans Am Ophthalmol Soc 1994;92:589-641.  Back to cited text no. 1
[PUBMED]  [FULLTEXT]  
2.
Spaeth GL. Development of glaucomatous changes of the optic nerve. In: Verma R, Spaeth GL, editors. The Optic Nerve in Glaucoma . Philadelphia, JB Lippincott, 1993. pp 193-207.  Back to cited text no. 2
    
3.
Quigley HA, Addicks EM, Green WR. Optic nerve damage in human glaucoma. III. Quantitative correlation of nerve fiber loss and visual field defect in glaucoma, ischemic neuropathy, papilledema, and toxic neuropathy. Arch Ophthalmol 1982;100:135-46.  Back to cited text no. 3
[PUBMED]  [FULLTEXT]  
4.
Quigley HA, Green WR. The histology of human glaucoma cupping and optic nerve damage: clinicopathologic correlation in 21 eyes. Ophthalmology 1979;86:1803-30.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  
5.
Radius RL, Maumenee AE, Green WR. Pit-like changes of the optic nerve head in open-angle glaucoma. Br J Ophthalmol 1978;62:389-93.  Back to cited text no. 5
[PUBMED]  [FULLTEXT]  
6.
Woon WH, Fitzke FW, Bird AC, Marshall J. Confocal imaging of the fundus using a scanning laser ophthalmoscope. Br J Ophthalmol 1992;76:470-74.  Back to cited text no. 6
[PUBMED]  [FULLTEXT]  
7.
Chihara E, Takahashi F, Chihara K. Assessment of optic disc topography with scanning laser ophthalmoscope. Graefes Arch Clin Exp Ophthalmol 1993;231:1-6.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.
Zangwill L, Shakiba S, Caprioli J, Weinreb RN. Agreement between clinicians and a confocal scanning laser ophthalmoscope in estimating cup/disk ratios. Am J Ophthalmol 1995;119:415-21.  Back to cited text no. 8
[PUBMED]  [FULLTEXT]  
9.
Bathija R, Zangwill L, Berry CC, Sample PA, Weinreb RN. Detection of early glaucomatous structural damage with confocal scanning laser tomography. J Glaucoma 1998;7:121-27.  Back to cited text no. 9
[PUBMED]  [FULLTEXT]  
10.
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.  Back to cited text no. 10
    
11.
Wollstein G, Garway-Heath DF, Hitchings RA. Identification of early glaucoma cases with the scanning laser ophthalmoscope. Ophthalmology 1998;105:1557-63.   Back to cited text no. 11
[PUBMED]  [FULLTEXT]  
12.
Meyer T, Howland HC. How large is the optic disc? Systematic errors in fundus cameras and topographers. Ophthalmic Physiol Opt 2001;21:139-50.  Back to cited text no. 12
[PUBMED]  [FULLTEXT]  
13.
Jonas JB, Mardin CY, Grundler AE. Comparison of measurements of neuroretinal rim area between confocal laser scanning tomography and planimetry of photographs. Br J Ophthalmol 1998;82:362-66.  Back to cited text no. 13
[PUBMED]  [FULLTEXT]  
14.
Anderson DR: Automated Static Perimetry. St. Louis: Mosby Year Book, 1992.  Back to cited text no. 14
    
15.
American Academy of Ophthalmology. Preferred Practice Patterns 2000.   Back to cited text no. 15
    
16.
Nguyen NX, Horn FK, Langenbucher A, Mardin CY. Conventional versus digital planimetry of optic disc photograph: a clinical comparative study. Klin Monatsbl Augenheilkd 2001;218:727-32  Back to cited text no. 16
[PUBMED]  [FULLTEXT]  
17.
Hellstrom A, Svensson E. Optic disc size and retinal vessel characteristics in healthy children. Acta Ophthalmol Scand 1998;76:260-67  Back to cited text no. 17
[PUBMED]  [FULLTEXT]  
18.
Funaki S, Shirakashi M, Abe H. Relation between size of optic disc and thickness of retinal nerve fibre layer in normal subjects. Br J Ophthalmol 1998;82:1242-45.   Back to cited text no. 18
[PUBMED]  [FULLTEXT]  
19.
Nakamura H, Maeda T, Suzuki Y, Inoue Y. Scanning laser tomography to evaluate optic discs of normal eyes. Jpn J Ophthalmol 1999;43:410-14  Back to cited text no. 19
[PUBMED]  [FULLTEXT]  
20.
Jonas JB, Papastathopoulos K. Ophthalmoscopic measurement of the optic disc. Ophthalmology 1995;102:1102-6.  Back to cited text no. 20
[PUBMED]  [FULLTEXT]  
21.
Iester M, Broadway DC, Mikelberg FS, Drance SM. A comparison of healthy, ocular hypertensive, and glaucomatous optic disc topographic parameters. J Glaucoma 1997;6:363-70.  Back to cited text no. 21
[PUBMED]  [FULLTEXT]  
22.
Saruhan A, Orgul S, Kocak I, Prunte C, Flammer J. Descriptive information of topographic parameters computed at the optic nerve head with the Heidelberg Retina Tomograph. J Glaucoma 1998;7:420-29.  Back to cited text no. 22
[PUBMED]  [FULLTEXT]  
23.
Varma R, Tielsch JM, Quigley HA, Hilton SC, Katz J, Spaeth GL, Sommer A. Race-, age-, gender- and refractive error-related differences in the normal optic disc. Arch Ophthalmol 1994;112:1068-76.  Back to cited text no. 23
[PUBMED]  [FULLTEXT]  
24.
Mansour AM. Racial variation of optic disc size. Ophthalmic Res 1991;23:67-72.  Back to cited text no. 24
[PUBMED]  [FULLTEXT]  
25.
Kashiwagi K, Tamura M, Abe K, Kogure S, Tsukahara S. The influence of age, gender, refractive error, and optic disc size on the optic disc configuration in Japanese normal eyes. Acta Ophthalmol Scand 2000;78:200-3.  Back to cited text no. 25
[PUBMED]  [FULLTEXT]  
26.
Sekhar GC, Prasad K, Dandona R, John RK, Dandona L. Planimetric optic disc parameters in normal eyes: A population based study in South India. Indian J Ophthalmol 2001;49:19-23.   Back to cited text no. 26
[PUBMED]  [FULLTEXT]  
27.
Britton RJ, Drance SM, Schulzer M, Douglas GR, Mawson DK. The area of the neuroretinal rim of the optic nerve in normal eyes. Am J Ophthalmol 1987;103:497-504.  Back to cited text no. 27
[PUBMED]  [FULLTEXT]  
28.
Funk J, Dieringer T, Grehn F. Correlation between neuroretinal rim area and age in normal subjects. Graefes Arch Clin Exp Ophthalmol 1989;227:544-48.  Back to cited text no. 28
[PUBMED]  [FULLTEXT]  
29.
Leibowitz HM, Krueger DE, Maunder LR, Milton RC, Kini MM, Kahn HA, et al. The Framingham Eye Study monograph: An ophthalmological and epidemiological study of cataract, glaucoma, diabetic retinopathy, macular degeneration, and visual acuity in a general population of 2631 adults, 1973-1975. Surv Ophthalmol 1980;24:335-610.  Back to cited text no. 29
[PUBMED]  [FULLTEXT]  
30.
Kergoat H, Kergoat MJ, Justino L, Lovasik JV. Age-related topographical changes in the normal human optic nerve head measured by scanning laser tomography. Optom Vis Sci 2001;78:431-35.  Back to cited text no. 30
[PUBMED]  [FULLTEXT]  


    Figures

  [Figure - 1], [Figure - 2], [Figure - 3]
 
 
    Tables

  [Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6], [Table - 7]


This article has been cited by
1 Optic disc topography in normal Indian eyes using spectral domain optical coherence tomography
Mansoori, T., Viswanath, K., Balakrishna, N.
Indian Journal of Ophthalmology. 2011; 59(1): 23-27
[Pubmed]
2 Assessment of optic disc parameters among healthy adult Malays by Heidelberg Retinal Tomograph II
Jusoh, S., Shaharuddin, B., Wan Hitam, W.H.
Clinical and Experimental Ophthalmology. 2011; 39(1): 15-22
[Pubmed]
3 Comparison of the diagnostic ability of Moorfieldæs regression analysis and glaucoma probability score using Heidelberg retinal tomograph III in eyes with primary open angle glaucoma
Jindal, S., Dada, T., Sreenivas, V., Gupta, V., Sihota, R., Panda, A.
Indian Journal of Ophthalmology. 2010; 58(6): 487-492
[Pubmed]
4 Tilted optic disks
Witmer, M.T., Margo, C.E., Drucker, M.
Survey of Ophthalmology. 2010; 55(5): 403-428
[Pubmed]
5 Open angle glaucoma-trends in management
Sood, D., Goyal, D., Sood, N.N.
Journal International Medical Sciences Academy. 2010; 23(3): 158-163
[Pubmed]
6 Analysis of optic disc parameters in Zhuang nationality by Heidelberg retina tomograph
Yang, K., Li, L., Bai, H.-Q.
International Journal of Ophthalmology. 2010; 10(4): 739-741
[Pubmed]
7 Comparison of the Diagnostic Capability of the Heidelberg Retina Tomographs 2 and 3 for Glaucoma in the Indian Population
Rao, H.L., Babu, G.J., Sekhar, G.C.
Ophthalmology. 2010; 117(2): 275-281
[Pubmed]
8 Estimating normative limits of Heidelberg retina tomograph optic disc rim area with quantile regression
Artes, P.H., Crabb, D.P.
Investigative Ophthalmology and Visual Science. 2010; 51(1): 355-361
[Pubmed]
9 Optic nerve heads in pediatric african americans using retinal tomography
Pang, Y., Trachimowicz, R., Castells, D.D., Goodfellow, G.W., Maino, D.M.
Optometry and Vision Science. 2009; 86(12): 1346-1351
[Pubmed]
10 Normative data of optic nerve head in Thai population by laser scanning tomography: Siriraj study
Ruangvaravate, N., Neungton, C.
Journal of the Medical Association of Thailand. 2008; 91(6): 859-863
[Pubmed]
11 Diagnosis of open-angle glaucoma by Moorfields regression analysis and multivariate discriminate analysis
Liu, C., Hu, Y., Xu, C., Zhu, Z.
Chinese Ophthalmic Research. 2007; 25(10): 778-781
[Pubmed]
12 Evaluation of optical coherence tomography and heidelberg retinal tomography parameters in detecting early and moderate glaucoma
Naithani, P., Sihota, R., Sony, P., Dada, T., Gupta, V., Kondal, D., Pandey, R.M.
Investigative Ophthalmology and Visual Science. 2007; 48(7): 3138-3145
[Pubmed]
13 Linear regression modeling of rim area to discriminate between normal and glaucomatous optic nerve heads: The Bridlington eye assessment project
Hawker, M.J., Vernon, S.A., Tattersall, C.L., Dua, H.S.
Journal of Glaucoma. 2007; 16(4): 345-351
[Pubmed]
14 Sensitivity and specificity of Heidelberg retinal tomography II parameters in detecting early and moderate glaucomatous damage: Effect of disc size
Uysal, Y., Bayer, A., Erdurman, C., Kiliç, S.
Clinical and Experimental Ophthalmology. 2007; 35(2): 113-118
[Pubmed]
15 Optic Disk Size and Glaucoma
Hoffmann, E.M., Zangwill, L.M., Crowston, J.G., Weinreb, R.N.
Survey of Ophthalmology. 2007; 52(1): 32-49
[Pubmed]
16 Automated analysis of Heidelberg retina tomograph optic disc images by glaucoma probability score
Coops, A., Henson, D.B., Kwartz, A.J., Artes, P.H.
Investigative Ophthalmology and Visual Science. 2006; 47(12): 5348-5355
[Pubmed]
17 Specificity of the Heidelberg Retina Tomographæs Diagnostic Algorithms in a Normal Elderly Population. The Bridlington Eye Assessment Project
Hawker, M.J., Vernon, S.A., Ainsworth, G.
Ophthalmology. 2006; 113(5): 778-785
[Pubmed]
18 Laser scanning tomography of the optic nerve head in a normal elderly population: The Bridlington eye assessment project
Vernon, S.A., Hawker, M.J., Ainsworth, G., Hillman, J.G., MacNab, H.K., Dua, H.S.
Investigative Ophthalmology and Visual Science. 2005; 46(8): 2823-2828
[Pubmed]
19 Asymmetry in optic disc morphometry as measured by Heidelberg Retina Tomography in a normal elderly population: The Bridlington Eye Assessment Project
Hawker, M.J., Vernon, S.A., Ainsworth, G., Hillman, J.G., MacNab, H.K., Dua, H.S.
Investigative Ophthalmology and Visual Science. 2005; 46(11): 4153-4158
[Pubmed]
20 Reproducibility of optic nerve head measurements obtained by optical coherence tomography
Olmedo, M., Cadarso-Suarez, C., Gomez-Ulla, F., Val, C., Fernandez, I.
European Journal of Ophthalmology. 2005; 15(4): 486-492
[Pubmed]
21 Review of modern diagnostic methods for glaucoma suspects and glaucoma patients | [Moderne diagnostische verfahren bei glaukomverdacht und glaukom]
Vass, C.
Klinische Monatsblatter fur Augenheilkunde. 2004; 221(4): 227-246
[Pubmed]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
Abstract
Materials and Me...
Results
Discussion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed14850    
    Printed411    
    Emailed53    
    PDF Downloaded1138    
    Comments [Add]    
    Cited by others 21    

Recommend this journal