|Year : 1983 | Volume
| Issue : 5 | Page : 594-596
Evaluation of cup disc ratio with other parameters for diagnosis of O.A.G.
NN Sood, HC Aggarwal, B Ghosh
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, Ansari Nagar, New Delhi, India
N N Sood
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, Ansari Nagar, New Delhi - 29
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sood N N, Aggarwal H C, Ghosh B. Evaluation of cup disc ratio with other parameters for diagnosis of O.A.G. Indian J Ophthalmol 1983;31:594-6
|How to cite this URL:|
Sood N N, Aggarwal H C, Ghosh B. Evaluation of cup disc ratio with other parameters for diagnosis of O.A.G. Indian J Ophthalmol [serial online] 1983 [cited 2019 Aug 21];31:594-6. Available from: http://www.ijo.in/text.asp?1983/31/5/594/36600
Early diagnosis of open angle glaucoma still poses a problem and challenge. The problem is more so in India because of the lack of modern facilities such as improved methods of tonometry, optic disc photography, improved technique of visual field charting in many places. Hence a simple and quick method for early diagnosis of this condition needs to be evolved. The purpose of this communication is to evaluate the efficacy of cup disc ratio as primary criterian in detecting open angle glaucoma.
| Materials and Methods|| |
A total of 112 cases with suspicious optic cups, but with normal intraocular pressure (scale reading more than 3.5/5.5 gm. weight by schiotz tonometer) recordings in the out patient department of Dr. R.P. Centre hospital were investigated for open angle glaucoma between (1978 to 1980). The criteria for suspicious discs were cup disc ratio more than 0.3, asymmetry between the cup of both eyes of more than 0.2, vertical enlargement of the cups, sharp wall of the optic cup or focal notching, deep cup with thinning of neuroretinal rim & displacement of vessels.
A detailed history including family history of diabetes mellitus, endocrine disorders, hypotensive episodes, pseudoexfoliation of the lens, vascular blocks, myopia etc. were also taken into consideration. All the patients were subjected to gonioscopy, diurnal variat:cn, water drinking test, applanation tonometry, outflow facility, visual field charting, estimation of blood sugar levels (Fasting & Post Prandial). A correlation of the high risk factors with these investigative procedures in the diagnosis of OAG is being highlighted.
| Results|| |
Out of the total of 112 patients screened 62 were males and 50 females. 4 patients were one eyed and hence the study comprised of 220 eyes. The cases were evenly spread between all age groups [Table - 1]. All four types of phasic variation of intraocular pressure .were recorded [Table - 2]. A difference of more than 8 mm. Hg or a recording of more than 24.4 mm. Hg schiotz was taken as positive, and based on this 26.4% of the eyes examined were found to be positive [Table - 3].
The prevalence of risk factor in proved glaucomatous eyes [Table - 4] was found to be significantly higher than in proved normal eyes.
Break up of eyes as per cup disc ratio revealed higher prevalence of proved glaucoma and risk factor in relatively smaller cups e.g. upto 0.6 as compared to larger cups [Table - 5].
| Discussion|| |
The present study reveals certain important aspects in the early diagnosis of open angle glaucoma.
A) Diurnal variation
The patients having early open angle glaucoma with suspicious cup disc ratio exhibit exaggerated diurnal fluctuation of intraocular pressure. They have most commonly monophasic variation of intraocular pressure with peak rise either in morning hours or during evening hours. A small percentage of cases have both morning and evening rise of intraocular pressure. Such cases are likely to be missed because in routine such patients attend the hospital for general eye check up or for prescription of glasses only during office hours. i.e. beyond the peak hours of diurnal fluctuation.
B) Cup Disc ratio
The assessment of cup disc ratio, though has its limitation, is still a very useful and simple method of glaucoma screening particularly when taken in conjunction with other investigations. The size of the optic cup is related to the height of I.O.P.  However, paradoxically the present study reveals lesser positive cases with larger cups and hence calls for an explanation. Since this study has included only cases with normal I.O.P. recordings in the OPD but with suspicious cups, it is obvious that most of these cases probably have non-glaucomatous enlargement of the cups.
C) Risk Factors
The prevalence of diabetes mellitus, thyroid dysfunction, pseudoexfoliation of the lens, pigment dispersion syndrome, hypotensive episode, has been found to be significantly higher in glaucomatous individuals in comparison to normals. This study shows the incidence of these high risk factors to be 20.7% in cases with positive diurnal variation as compared to 6.4% in normal eyes (negative diurnal variation). In this study out of seventeen eyes having cup disc ratio upto 0.6 and associated risk factor the diurnal was positive in 52.9% eyes and water drinking test was found to be positive in the rest 47.1 % of eyes having negative diurnal test. This clearly shows that eyes with optic cup disc ratio of more than 0.3 when associated with local or systemic high risk factors are positively more prone to develop glaucoma. Hence such eyes should be thoroughly investigated and even if the results of various glaucoma investigations are borderline positive, they should be either treated or kept under close observation.
| Summary|| |
Ophthalmoscopic evaluation of optic disc as a parameter for early detection of primary open angle glaucoma is of great importance. Casual check up of intraocular pressure in these cases during routine working hours would not be able to pick up early glaucoma cases having exaggerated monophasic or biphasic diurnal fluctuation of intraocular pressure. Abnormal cup disc ratio when associated with local and systemic high risk factors such as pseudoexfoliation of lens capsule, pigment dispersion syndrome, high myopia, glaucomatous fellow eye, family history of glaucoma, diabetes mellitus, hypotensive episode, and endocrinal disease further point towards the probability of having open angle glaucoma. Therefore such eyes should be thoroughly investigated and required to be treated or kept under close observation even when the results of glaucoma investigations are border line positive.
| References|| |
Armaly M.F., Invest. Ophth., 9, 425, 1970
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5]