|Year : 1982 | Volume
| Issue : 6 | Page : 587-592
Primary open angle glaucoma in retinal detachment
A Sinha, PK Khosla, HK Tiwari
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, India
Dr. R.P. Centre, AIIMS, New Delhi-29
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sinha A, Khosla P K, Tiwari H K. Primary open angle glaucoma in retinal detachment. Indian J Ophthalmol 1982;30:587-92
The endeavour in the present study is to find out the prevalence of open angle glaucoma in consecutive cases of retinal detachment keeping close watch on the various parameters in the detached and the fellow eye.
| Material and methods|| |
50 consecutive patients of rhegmatogenous retinal detachment were investigated for primary open angle glaucoma. The following parameters were recorded in addition to full ocular examination (1) depth of anterior chamber by Pachometer (Haag Streit Attachment I & II) (ii) Status of angle by Goldmann's gonioscope (iii) fields wherever possible (iv) cup disc ratio (v) Diurnal variation of intraocular pressure (vi) Water drinking test (vii) C value and Po/C (viii) Scleral rigidity.
Cup disc ratio was noted subjectively (ratio upto 0.4 normal, 0.5 or more -positive. Difference of 0.2 or more in cup--disc ratio in both eyes was considered significant (apart from the absolute values). A diurnal variation of intraocular pressure was done in both eyes by Schiotz tonometer ; tensions being recorded at 4 AM, 7AM, 10 AM, 4 PM, 7 PM, 10 PM (variation upto 8 mm Hg--normal over 8 mm Hg-positive). In cases where the tension was uurecordably low, it was taken as Omm Hg Schiotz for purposes of this study. A water drinking test was done (rise of upto 8 mm Hgnormal, over 8 mm Hg-positive) A `C' value using the Schiotz tonometer was done in every case (0.18 or more-normal 0.12-0.18-suspicious and less than 0.12-positive) and Po/C was calculated (100 or' less-normal, over 100positive), Schiotz and applanation readings were used to determine the scleral rigidity using the Friedenwald's nomogram.
| Observations|| |
The age and sex incidence of the patients in this study is shown in [Table - 1].
Anterior chamber depth was within normal limits and angles were open in all cases (a chamber depth of less than 1.8 mm is considered critically shallow); The peripheral and central fields were done and were considered not reliable in eyes where concomitant pathology and poor vision was present, otherwise no specific defects were seen.
[Table - 2] shows the number of normal, suspicious and positive parameters in the fellow eye and detached eye of patients in this series.
[Table - 3] shows the number of normal, suspicious and positive parameters when we take the extent of detachment into account.
[Table - 4] shows the tension at the time of admission in the detached eye, along with the extent of detachment, and'tension in the fellow eye.
[Table - 5] shows the mean, standard deviation and statistical significance between the fellow eye and detached eye when the various parameters in this study were taken into account.
When all parameters were collectively considered, 5 patients in this series were found to have primary open angle galucoma, giving a prevalence of 10%.
| Discussion|| |
The co-existence of primary open angle glaucoma and retinal detachment is known but is not a widely appreciated fact, although retinal detachment is known to be precipitated by miotics being used for Primary open angle glaucoma. Raised intraocular pressure in an eye with retinal detachment may be (i) secondary glaucoma due to consequent uveitis, essentially unilateral or (ii) a primary open angle glaucoma occurring concurrently, essentially bilateral. Hence its evidence can be seen in the normal fellow eye.
In our study, as Pachometry and Gonioscopy showed a normal anterior chamber depth and open angle it was concluded that no case of narrow angle glaucoma was seen. This can be expected as the sample is biased due to the fact that detachment is usually associated with myopia or aphakia. Visual fields were within normal limits if concomitant other pathology was not present.
We have studied diurnal variation of intraocular pressure, Aater drinking provocative test, C value and Po/C value and cup disc ratio. Difference in cup disc ratio in both eyes was taken into account, when finally diagnosing a case as glaucoma. Positive isolated parameters were not considered diagnostic but combination of all parameters in both the eyes (eyes with detachment and the fellow eye) were considered before labelling a case as glaucoma. We diagnosed 5 cases as primary open angle glaucome (prevalence of 10%). 4 were detected a new while I was already a known case but was not on pilocarpine at the time of occurrence of retinal detachment. Another showed angle recession in the detached eye (history of blunt injury) but as the fellow eyes showed positive changes of glaucoma it indicated that glaucoma was not traumatic it origin. The overall prevalence of galucoma it our population as determined by a survey conducted by the National Society for the Prevention of Blindness (India) is 0.5%. Prevalence of open angle glaucoma in retinal detachment has been reported between 5-17%.
A positive water drinking test was seen in an equal number of fellow and detached eyes (6.6). Out of the 6 patients showing a positive water drinking test in the fellow eye 5 turned out to be glaucomatous when all the parameters were taken into account, while the sixth patient with a positive C value and Po/C value could possibly be considered as only having ocular hypertension, as cup disc ratio, diurnal variation and fields were within normal limits. Of the 6 eyes with retinal detachment showing a positive water drinking test 3 were found to have glaucoma, while the remaining 3 did not turn out to be glaucomatous when all the parameters were taken into account. All the three diagnosed as glaucoma from the findings in detached eye were also diagnosed as glaucoma on the basis of findings in the fellow eye. All patients diagnosed as glaucoma had a positive water drinking test in the fellow eye so we feel that this test is diagnostic while the water drinking test in the detached eye may not be reliable.
More eyes with detachment showed a positive diurnal than the fellow eye (42% : 30%), The number of positive diurnal variations in the follow eve in our series is high-30% and although only 10% patients were found to have glaucoma, this large group of positive diurnals need to be followed up, as they may develop glaucoma later.
It was surprising to see marked diurnal variation in intraocular pressure in detached eyes, from unrecordably low to 17.3 mm Hg Schiotz, which actually brought in probably false positives. Comparing the extent of detach ment in these cases it was observed that positive diurnal variation was seen more in patients with subtotal and total detachment (54%) as compared to patients with 2 quadrant detachment (35%). This would suggest that the detachment and its extent may have a bearing on the aqueous flow dynamics, which may be very liable, the factor of scleral rigidity being constant for 24 hours. although it is significantly lower in the detached eye than in the fellow eye. From our study it is evident that aqueous secretion in eyes with retinal detachment is very liable, fluctuating from phases of extreme hyposecretion to normal secretion in a span of 24 hours. Consequently isolated intraocular tension recording in these eyes may be of little value, and the need to do a diurnal variation to have an idea of the intraocular pressure is evident.
Based on Schiotz tension taken at the time of admission, we found 38% eyes to be hypo: tensive, 58% normotensive and 4% hypertensive. Hypotension wos commonest with subtotal and total detachment and our observations indicate that the tension decreases as the extent of detachment increases. As 4 of our S patients who ultimately turned out to be glaucomatous had normal or raised tension at the time of admission, it is emphasized that all patients of retinal detachment with normal or raised tension should be fully investigated for primary open angle glaucoma.
In our series, a positively decreased `C' value was found almost twice as frequently (18% : 10%) in the fellow eye than in the detached eye while a positive Po/C value was 12 times commoner in the fellow eye (18% 12%). There was no statistically significant difference in the outflow facility of the detached eye and the fellow eye and the mean outflow facility in the fellow eye was 0.16, less than the normal value (0.18 or more). As we have not studied outflow facility in a normal population balanced for age and sex, we cannot say whether this difference is statistically significant in these patients from normals. While determining outflow facility one must also take into account the lowered scleral rigidity and the status of aqueous secretion at that time. Lowered scleral rigidity would flatten tonographic tracings. Thus, we feel that outflow facility readings may be fallacious in eyes with retinal detachment and the fellow eye should be more relied upon.
A cup disc ratio of 0.5 or more was seen in 18% fellow eyes and 8% detached eyes, while a difference of 0.2 or more in the two eyes was seen in 12% cases. Their importance was ascertained only in conjunction with other parameters. As this ratio is genetically determined, the high incidence of increased cup disc ratio in the fellow eye of detachment patients would suggest a common genetic basis for detachment and increased cup disc ratio, a predisposing factor for glaucoma.
High incidence of open angle glaucoma in a population of retinal detachment patients would suggest the possibility of a common predisposition which may be due to a yet undetermined genetic factor. The role of HLA B-7 and HLA B-12 antigens in glaucoma patients is well known. High incidence of association of myopia and glaucoma, myopia and detachment is also well known. In this context,
it would be worthwhile studying the HLA antigens in these three entities and see if a corn mon genetic factor exists.
| Summary and conclusions|| |
50 consecutive patients admitted with retinal detachment were investigated for primary open angle glaucoma. A positive water drinking test in the fellow eyes was found to be the most diagnostic test in detecting these patients. Eyes with detachment often showed a large diurnal fluctuation, suggesting that the rate of aqueous secretion in these cases is very liable and this is further contributed to by the extent of detachment. Tension was seen to decrease as the extent of detachment increased. Outflow sacilities in paired eyes of individual patients were almost the same, but 18% fellow eyes showed an outflow facility of, less than 0 12; and a cup disc ratio of more than 0.5. Scleral regidity in detached eyes is significantly lower than in the fellow eyes. Considering all parameters, a prevalence of 10% primary open angle glaucoma in patients of retinal detachment has been found. A common genetic pre, disposition to bath detachment and glaucoma is suggested.
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5]