SOME IMPORTANT REFERENCES OF RECENT YEARS TO GET YOUR STUDIES STARTED

1.) http://bjo.bmjjournals.com/cgi/content/full/87/2/189 

Optic disc morphology in south India: the Vellore Eye Study

J B Jonas1, R Thomas2, R George2, E Berenshtein1 and J Muliyil3

1 Department of Ophthalmology, Faculty of Clinical Medicine Mannheim, University of Heidelberg, 68167 Mannheim, Germany
2 Department of Ophthalmology, Schell Eye Hospital, Christian Medical College, Arni Road, Vellore 632001, Tamil Nadu, India
3 Community Health Department, Christian Medical College, Arni Road, Vellore 632001, Tamil Nadu, India

Correspondence to:
Dr J Jonas, Universitäts-Augenklinik, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany;
Jost.Jonas@augen.ma.uni-heidelberg.de

Accepted for publication 19 July 2002


ABSTRACT
Aim: To evaluate the morphology of the optic nerve head in an unselected population group in south India.

Methods: The study included 70 subjects forming a population based sample, selected in a random manner. Mean age was 47.5 (SD 8.7) years, mean refractive error measured -0.07 (1.11) dioptres (range -4.50 to +2.50 dioptres). Optic disc slides were morphometrically analysed.

Results: Mean optic disc area measured 2.58 (0.65) mm2. It was statistically independent of age and refractive error. Optic disc shape was slightly vertically oval. Mean neuroretinal rim area was 1.60 (0.37) mm2. It was significantly and positively correlated with optic disc size and optic cup size. It was independent of age, sex, refractive error, and axial length. In all subjects included in the study, the rim was smallest in the temporal horizontal optic disc sector. Mean horizontal cup/disc diameter ratio (0.66 (0.07)) was significantly (p<0.001) higher than the mean vertical cup/disc diameter ratio (0.56 (0.08)). Both ratios were highly significantly (p <0.001) and positively correlated with optic disc size. Thezone of parapapillary atrophy (0.84 (0.29) mm2), and ß zone (0.13 (0.38) mm2), respectively, occurred in 69 (98.6%) subjects and in eight (11.4%) subjects, respectively. They were significantly larger in the temporal horizontal sector. The zone was significantly (p<0.001) larger and occurred significantly more often than ß zone. Retinal arterioles and venules were wider, and in spatial correlation, the visibility of the retinal nerve fibre layer was significantly better, in the temporal inferior disc arcade and the temporal superior arcade than in the nasal superior arcade and the nasal inferior vessel arcade. Except for the absolute size measurements these optic nerve head parameters did not differ markedly (p >0.05) from the values found in white people.

Conclusions: South Indians and white people do not show marked differences in the morphology of the optic nerve head as measured by morphometric optic disc parameters, with the possible exception of the absolute optic disc dimensions.

2.)  http://bjo.bmjjournals.com/cgi/content/full/82/10/1118

Vertical cup/disc ratio in relation to optic disc size: its value in the assessment of the glaucoma suspect

David F Garway-Heath, Simon T Ruben, Ananth Viswanathan, Roger A Hitchings

Glaucoma Unit, Moorfields Eye Hospital, City Road, London EC1V 2PD

Correspondence to: Mr D F Garway-Heath.

Accepted for publication 24 March 1998


ABSTRACT

AIMS The vertical cup/disc ratio (CDR) has long been used in the assessment of the glaucoma suspect, though the wide range of CDR values in the normal population limits its use. Cup size is related physiologically to disc size and pathologically to glaucomatous damage. Disc size can be measured at the slit lamp as the vertical disc diameter (DD). The ability of the CDR, in relation to DD, to identify glaucomatous optic discs was investigated.
METHODS 88 normal, 53 early glaucoma, and 59 ocular hypertensive subjects underwent stereoscopic optic disc photography and clinical biometry. Photographs were analysed in a masked fashion by computer assisted planimetry. The relation between vertical cup diameter and DD was explored by linear regression, and expressed in terms of CDR. The upper limit of normal was defined by the 95% prediction intervals of this regression (method 1) and by the upper 97.5 percentile for CDR (method 2). The sensitivity and specificity of CDR to identify an optic disc as glaucomatous was tested with these disc size dependent and disc size independent cut offs in small, medium, and large discs.
RESULTS The CDR was related to DD by the equation CDR = ( 1.31 + (1.194 × DD))/DD. The sensitivity in small, medium, and large discs was 80%, 60%, and 38% respectively for method 1 and 33%, 67%, and 63% respectively for method 2. Specificity was 98.9% (method 1) and 97.7% (method 2).
CONCLUSIONS The CDR, relative to disc size, is useful clinically, especially to assist in identifying small glaucomatous discs.
(Br J Ophthalmol 1998;82:1118-1124)

3.)   http://www.iovs.org/cgi/content/full/41/7/1764

 Ranking of Optic Disc Variables for Detection of Glaucomatous Optic Nerve Damage

Jost B. Jonas1, Antonio Bergua1, Paul Schmitz–Valckenberg2, Konstantinos I. Papastathopoulos2 and Wido M. Budde1

1 From the Department of Ophthalmology, Friedrich-Alexander University Erlangen-Nürnberg, Germany; and the 2 Department of Ophthalmology, Evangelisches Stift Hospital, Koblenz, Germany.


ABSTRACT


PURPOSE. To describe optic disc variables assessed by evaluation of clinical optic disc photographs and to compare sensitivity and specificity of these optic disc parameters in identifying patients with ocular hypertension who have nerve fiber layer defects and normal visual fields and patients with visual field defects.

METHODS. The study included 500 normal subjects, 132 patients with ocular hypertension with retinal nerve fiber layer defects and normal visual fields (preperimetric glaucoma), and 840 patients with glaucomatous visual field defects. Color stereo optic disc photographs were morphometrically evaluated.

RESULTS. Highest diagnostic power for the separation between the normal group and the preperimetric glaucoma group had the vertical cup-to-disc diameter ratio corrected for its dependence on the optic disc size, total neuroretinal rim area, rim-to-disc area ratio corrected for disc size, and cup-to-disc area ratio corrected for disc size. Diagnostic power was lower for rim area in the temporal inferior and temporal superior disc sector, cup area corrected for disc size, and horizontal cup-to-disc diameter ratio corrected for disc size. Less useful for the differentiation between the normal subjects and the preperimetric glaucoma group were size of zones alpha and beta of parapapillary chorioretinal atrophy, and ratios of neuroretinal rim width and rim area comparing various optic disc sectors with each other.

CONCLUSIONS. In subjects with ocular hypertension with retinal nerve fiber layer defects and normal conventional achromatic visual fields, the vertical cup-to-disc diameter ratio corrected for optic disc size, total neuroretinal rim area, rim-to-disc area ratio, and cup-to-disc area ratio corrected for disc size are the most valuable optic disc variables for early detection of glaucomatous optic nerve damage. Correction for optic disc size is necessary for optic disc variables directly or indirectly derived from the optic cup. Parapapillary atrophy is less important in the early detection of glaucoma.

4).  May 2003, 129th Annual Alumni Meeting, Scheie Eye Institute, University of Pennsylvania in Philadelphia: "DOREAL Optic Nerve Biometry"

Author: Peter George Gross MD PhD

Clinical/Academic Title: Eye Surgeon and Physician / Ex-Assoc. Prof. of Astronomy

Mailing Address: 958 County Line Road, Suite 106 / Conestoga Medical Building

                                 Bryn Mawr, PA 19010

Telephone: 610 525 8282; Fax: 610 525 8282; Email: Peter.George.Gross@aya.yale.edu

 Title of Abstract: DOREAL OPTICTIC NERVE BIOMETRY

 Objective: The primary goal is to achieve efficacious optic nerve biometry (ONB) in a clinical setting using only the direct ophthalmoscope, refraction and the axial length (DOREAL-ONB©), without the need to acquire new equipment. The secondary goal is to allow for tracking glaucoma patients in a database matched both to the physician and the practice population for the purpose of meaningful statistical analyses.

Methods: The author developed Windows-compatible software based on the DOREAL ONB method previously published by Gross and Drance (1995). Details of the new software were tested on a Bryn Mawr patient population. Disc diameters and neuroretinal rim areas, the widths of the rim, the orientation of the disc and the influence of astigmatism on the calculations were obtained. The doctor (observer) needs to note the in-vivo disc-to-light ratio, the cup-to-disc ratio, the SINT rim ratios and the orientation of the disc. He notes these on a work sheet to which the assistants add the refraction and the axial lengths measurements and they enter the data from this sheet into the computer software where the calculations are completed.

Results: The result is a comprehensive summary in the form of a printout that is handed back to the doctor for review and approval, and insertion into the medical record. The graphic 10:1 scale representation of the actual optic disc serves to fine-tune the doctor’s skills via direct visual feedback. Comparison of the results with the personalized and population-specific statistics makes interpretations of the calculations more meaningful.

Conclusions: Use of the DOREAL-ONB software provides significant improvements in quantitative assessments of glaucoma and normal optic nerve heads. It is quick and economical for patients, doctors and third party providers. It compliments the use of laser scanner analyzers of anatomy since it allows tracking of the color component of the neuroretinal rim that contains an assessment of capillary bed perfusion at the level of the rim. It newly identifies, from among those patients previously considered normal, those that are glaucoma suspects and, therefore, in need of further detailed glaucoma workup.


5.)  May, 2004, 130th Annual Alumni Meeting, Scheie Eye Institute, University of Pennsylvania in Philadelphia: "Correlation of Direct Ophthalmoscopic Optic-Disc Measurements with the DOREAL-ONB and HRT Methods"                                     

Peter G. Gross

ABSTRACT

 Objective:  Given that glaucoma is one of the leading causes of blindness in the world, and that all doctors possess a direct ophthalmoscope, it is of great interest to see the accuracy with which the optic disc diameter and neural rim area can be evaluated just using this instrument alone.

 Methods:  Over 260 patients in a Bryn Mawr (Pennsylvania) sub-population consisting predominantly of blue-eyed Caucasians with about 5% African American and 20% Mediterranean extraction have been examined by one of us (PGG) using a direct ophthalmoscope. Ophthalmoscopic observations were entered into the ‘ALL-doctors’ version of DOREAL-ONB software designed to process ophthalmoscopic data alone. These same patients were also evaluated for axial length using an ultrasonic A-scanner and for refraction and observations entered into the ‘EYE-doctors’ version of DOREAL-ONB software designed to process the data. A subset of about 80 of these patients was also evaluated with an HRT-II laser scanner and software. Results were analyzed using Microsoft’s Excel spreadsheet software, taking advantage of the ‘Export to Excel’ option of the DOREAL-ONB software versions.

 Results:  Use of the direct ophthalmoscope alone on optic disc measurements provided us with the following correlations for:

  DOREAL Vertical Disc Diameter --------        y = 0.9551x + 0.0717      [R2 = 0.9142]

  DOREAL Horizontal Disc Diameter -----            y = 0.9962x + 0.0257      [R2 = 0.9023]

  DOREAL Neural Rim Area ----------------      y = 0.9442x + 0.1186      [R2 = 0.8784]

  HRT Disc Area -------------------------------           y = 1.1045x - 0.1821       [R2 = 0.5940]

 Conclusions:  The direct ophthalmoscope has long been a useful instrument in evaluating optic discs. The present data show that it is in fact even more useful than heretofore believed, because of the quantitative expectation values that it can provide the clinician interested in glaucoma assessment. The DOREAL-ONB, ALL-doctors version software transforms the direct ophthalmoscope into a practical optic-disc measuring device.

6.)  May 2005, 131st Annual Alumni Meeting, Scheie Eye Institute, University of Pennsylvania in Philadelphia: "Optic Disc Size: Direct Ophthalmoscope Only vs. HRT II in Non-Glaucomatous Patients"

 Author: Peter George Gross MD PhD

Co-Authors:             Vladimir Chechersky, PhD (Research Professor, Drexel U.)

                                    Daryl J. Di Rocco (Pre-Med, Villanova University)

 Title of Abstract: Optic Disc Size: Direct Ophthalmoscope Only vs. HRT II in Non-Glaucomatous Patients

 Objective: Measuring optic discs using the direct ophthalmoscope (DO) only in clinical screening.

 Methods: Cup/disc and disc/light ratios alone provide expectation values for optic disc parameters such as disc diameter, disc area (DA) and neural rim area when these ratios are entered into DOREAL-ONB software in DO-only mode. In a chart review of patients who had HRT II evaluations, 117 with normal visual fields were identified and their disc areas compared to the DO-only screening method.

 Results: The linear regression analysis resulted in y = 0.80x + 0.37, [R = 0.69] for the DA when the HRT II values are expressed as a function of the DO-only values. Optic disc areas obtained from this DO-only screening method correlate with disc areas from the HRT II photo-laser-scanner at the level of 69%.

 Conclusions: Disc/light ratios obtained during physical examination with a DO provide reliable screening values (with the use of inexpensive software) for the size (disc area and disc diameter) of the optic disc, and for its neural rim area when augmented by the cup/disc ratio. Therefore, determining the disc/light ratio, in addition to the cup/disc ratio, enables the clinician to identify significant differences from average optic disc parameters; such differences then provide, by themselves alone, a sufficient indication for further glaucoma workup, thereby enabling earlier diagnosis of glaucoma.