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ORIGINAL ARTICLE
Year : 1982  |  Volume : 30  |  Issue : 3  |  Page : 133-134

Disc-cup asymmetry in normal and chronic simple glaucoma


State Institute of Ophthalmology, M. D. Eye Hospital, Allahabad, India

Correspondence Address:
B D Sharma
Lecturer in Ophthalmology M.D. Eye Hospital, Allahabad. U.P.
India
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Source of Support: None, Conflict of Interest: None


PMID: 7174055

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How to cite this article:
Sharma B D, Chaturvedi R P. Disc-cup asymmetry in normal and chronic simple glaucoma. Indian J Ophthalmol 1982;30:133-4

How to cite this URL:
Sharma B D, Chaturvedi R P. Disc-cup asymmetry in normal and chronic simple glaucoma. Indian J Ophthalmol [serial online] 1982 [cited 2020 Feb 24];30:133-4. Available from: http://www.ijo.in/text.asp?1982/30/3/133/28191

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Glaucoma, one of the leading cause of irreversible blindness, requires its early detec­tion, as to prevent the persons to become blind. On the other hand, cupping of the optic disc is the single most reliable sign in diagnosing a case of chronic simple glaucoma. A cupped disc is associated with an ischa­emia of the optic nerve head leading to ischaemic optic neuropathy, which is responsi­ble for the field loss and diminution of vision.

Early cupping of the disc is more likely to be noted if the observer is aware of the situations that put the disc at particular risk liable to be damaged by glaucoma and one of those factors is the asymmetry of the disc cup in two eyes.

Although the normal physiological cupp­ing may vary widely in different individual; but cupping is almost always symmetrically similar in the two eyes of the same person But it has been noticed by many workers[1],[2] that the disc asymmetry to some extent is present in few normal and few glaucomatous cases. Therefore the role of asymmetry of the disc cups in two eyes becomes an essentia part of glaucoma screening. The purpose of this study is to have a closure attention over disc cup asymmetry in different persons wits a view to find out the relationship between cups asymmetry and chronic simple glaucoma.


  Materials and methods Top


The 105 cases in whom the asymmetry of disc cups in the two eyes was found on fundus examination were selected for the work.

For the establishment of asymmetry, the disc cups in the two eyes of the some indivi­dual were noted and compared to derive the index of cupping asymmetry (ICA)[1] which is the ratio of the index cupping with greater cupped disc to the index cupping with lesser cupped disc i.e.



The significant amount of asymmetry is called when this ICA value is found to be 1.5 or more.

The cases with significant amount of disc cup asymmetry were first examined thoroughly by external and oblique illumination to exclude any other ocular pathology and were subjected for glaucoma screening and for this they were investigated for Recording of intraocular ten­sion. Charting of visual fields and Visualization of angle by 3 mirror goldman's contact lens.

A group of individuals found out to be glaucomatous having an intraocular tension more than 24 mm of Hg by Schiotz, and wide open angle with field loss in few cases. Rest of the persons having the intraocular tension within normal limits were specially undergone following investigations i.e. provocative test in the form of water drinking test, facility of aqueous out flow and diurnal variation of intraocular tension.

The cases showing any of the above test positive were also included in the glaucoma­tous group.


  Observations Top


The total 105 cases with disc cup asymme­try were undertaken for study. Out of the 15 cases (14 3°,/) were found to be glaucomatous on first visit. 72 cases (68.5%) were proved to be glaucomatous on subsequent visits, thus making the glaucomatous group of 87 cases (82.8%) while 18 cases (17.2%) were found to be non-glaucomatous. The degree of asymmetry of the two disc cups was very less in non-glaucomatous cases, where as it was quite remarkable in glauco­matous persons. The pattern of emerging retinal blood vessels from the floor of cup was also extremely variable in all the cases. In few cases it was also observed that the asym­metry of disc cups was present with significant amount of cupping and overhanging edges even then they were found to be non-glauco­matous.


  Discussion Top


In our study we have noted a close relation ship between disc cup asymmetry and chronic simple glaucoma. In normal individuals the disc cups in the two eyes are almost symmetri­cal but 17.2% cases with significant asymmetry of the disc cups did not show any feature of glaucoma at any stage while remaining 82.8% of cases with significant disc cup asymmetry were proved to be glaucomatous. The presence of asymmetry in few normal persons can be correlated with the presence of anisometropia, and/or low perfusion pressure and/or systemic hypotension and/or some other vascular diseases.

Earlier workers have noted that 3% of normal people show asymmetrical disc cupp­ing[3]. It has been reported that cup disc ratio of one eye of an individual varies with 0.2 or more from that of the fellow eye in about 8% of cases[4]. Drance & coworkers[2] have examined extreme cases of asymmetry and have empha­sized the presence of dissimilar intra-ocular tension, perfusion pressure and occlusive vascular diseases as an important factor. Fishman[1] had found that only 5.6% of normal individual showed asymmetry of optic disc cupping, whereas in 36% of patients with chronic simple glaucoma the cups in the two eyes were different.


  Summary Top


Our findings that 82.8% of cases with disc cups asymmetry were found to be suffering from chronic simple glaucoma and 17.2% were proved to be non-glaucomatous denotes a higher incidence of chronic simple glaucoma in persons having disc cups asymmetry.

 
  References Top

1.
Fishman, R.S., 1970 Arch. Ophthalmol. F4:590.  Back to cited text no. 1
    
2.
Drance, M., Wheeler, C and Pattullo M. 1968, Amer. J. Ophthalraol 65:891.  Back to cited text no. 2
    
3.
Snydacker, D., 1964, Amer J. Ophthalmol. 58:958.  Back to cited text no. 3
    
4.
Armaly, M.F. and Saydegh R.E. 1969, Arch opthalmol. 82:191.  Back to cited text no. 4
    



 
 
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