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| ARTICLES |
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| Year : 1983 | Volume
: 31
| Issue : 6 | Page : 729-730 |
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Filteration surgery in myopic eyes
SK Narang, KN Soni
M & J Institute of Ophthalmology, Civil Hospital, Ahmedabad, India
Correspondence Address:
S K Narang
M & J Institute of Ophthalmology, Civil Hospital, Ahmedabad
India
 Source of Support: None, Conflict of Interest: None  | Check |
PMID: 6676253 
How to cite this article:
Narang S K, Soni K N. Filteration surgery in myopic eyes. Indian J Ophthalmol 1983;31:729-30 |
According to general opinion (Cori, Cala, Kraupa and others) the majority of patients suffering from glaucoma and an anomaly of refraction are hypermetropic. They have found emmetropia in 23%, hypermetropia in 62% and myopia in only 15% cases in 1459 cases of glaucema of open angle type. Hurby explained this on the basis of general pattern of refraction in the population. In our study of 743 cases of open anle glaucoma the incidence of myopia was 16.3% [Table - 1] whatever may be the association between these two conditions, we do get cases in which surgery becomes necessary in these cases because some of high myopic eyes are prone to Retinal Detachment and they can not be kept on miotics through out life especially the stronger miotics. Myopic eyes may be associated with other abnormalities like macular holes, ectopia lentis and squints. These must be considered before taking the patient for filteration surgery.
Filteration surgery in myopic eyes is some what different from the emmetropic eyes. In myopes of high degree, the sclera is thinner than in emmetropes and hypermetropes. The thickness in high myopes has been found to be .5mm (average) where as in emmetropes it is found to be .75mm (average) at the place near the limbus where the glaucoma surgery is being done. This must be kept in mind especially in doing S.S.S. where a lamellar direction of the sclera is done. In our hands in 3 cases of high myopic eyes we had to abond on the S.S.S. surgery because of failure to get a good lamellar flap and had to resort to some other type of surgery. Where as no such occassion arose in emmetropic or hypermetropic eyes. So it is advisable that if in reflecting the conjunctive we find that choroid is shinning, it is suggestive of thin sclera and we should not proceed with S.S.S. but do some other filtering surgery like Scheie's or irideucleisis.
In Scheies operation in high myopic eyes, we should not over cauterize the lips, as less heat cautery is required in such cases, otherwise there are chances of overfilteration. No alteration was needed in iridencleisis. [Table - 2]
As far as complication of surgery are concerned higher incidence of hyphema is reported in myopic eyes than in others. In our cases we have found incidence to be 10% in myopic eyes and 4% in the other eyes. But in all cases the blood cleared in 3-4 days (average) No explanation can be given for this difference.
Incidence of choroidal detachment after filteration operation was higher myopic eyes than nonmyopic eyes. The commonest cause of choroidal detachment is the serous exudation into the suprachoroidal space withh fall of I.O.T. High myopia yes are having vascular degeneration and choroidal vessels my burst into the suprachoroidal space when there is lowering of the I.O.T. It may be tempting to make a sclerotomy opening to drain the blood but such surgical interference should be avoided unless the intraocular tension is raised. There is a risk of inducing unless the intraocular tension is raised. There is a risk of inducing further bleeding in these myopic eyes. Most of these absorb by itself within 7-10 days. In our study in the incidence of choroidal detachment was 18% in myopic eyes in comparision to 8% in nonmyopic eyes. No patient needed surgical interfearence and it settled down in 7-10 days. [Table - 3] This difference was move marked in scheies.
Incidance of choroidal explusive hacmorrhage is reported to be more common in myopic eyes when it is associated with chronic simple glaucoma. Rarely there is any warning. As soon as incision is made, the intraocular structures move forward dislocating the lens and pushing it forwards. A good anesthesia is most important in such cases and so in high myopic eyes, we must release the aqueus gradually when opening the A.C. Luckily we have not met this complication in the cases.
Ultimate success rate in high myopic eyes have been almost the same as in emmetropic eyes. The tension and vision were considered as the parameters of successful operation. The success rate had been 96% in myopic eyes and 93% in nonmyopic eyes. The difference is insignificant.
However one should be careful to follow these cases by applanation tonometry as filteration operations decrease the ocular rigidily and ony schiotz readings may be deceptive.
[Table - 1], [Table - 2], [Table - 3], [Table - 4]
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