|Year : 1987 | Volume
| Issue : 3 | Page : 138-140
A survey on heredity of open angle glaucoma
Harsha Bhattacharjee, HK Chowdhury
Deptt of Ophthalmology, Silchar Medical College, Gauhathi, Assam, India
Deptt of Ophthalmology, Silchar Medical College, Gauhathi, Assam
Source of Support: None, Conflict of Interest: None
This study was undertaken to find out the incidence of Open Angle Glaucoma (OAG) in the sibs and children of glaucoma patients and to determine the hereditary nature. An attempt was made to estimate the magnitude of risk of developing this disease in family of the affected patients. It was found from this study that out of 65 cases of adult family members with open angle glaucoma. 26.6% cases had positive hereditary history. Among 263 children and sibling of patients with known glaucoma 79 members had this disease and 14 new cases were detected. This findings demonstrate the need for adequate screening of the sibling and children of known cases of open angle glaucoma as they comprised high risk population. The risk was 10 times higher than that of general population.
|How to cite this article:|
Bhattacharjee H, Chowdhury H K. A survey on heredity of open angle glaucoma. Indian J Ophthalmol 1987;35:138-40
| Introduction|| |
It is long been known that there is a tendency for Open Angle Glaucoma (OAG) to occur more frequently among the sibs and children of glaucoma patients Different studies suggest that clinical OAG may be as much as fifteen times more common in such subjects in comparison to unselected population ,5],, Prevalence of glaucoma in the unselectea population was estimated to be 2.5% in the age range over 40 , and 50% of the glaucoma patients were unknown
| Materials and Methods|| |
The survey was carried out amongst family members of sixty five cases of open angle glaucoma, registered in the glaucoma clinic of the deptt of Ophthalmology, Silchar Medical College, Assam The duration of study was July, 1983 to July, 1986.
All the family members who were thirty years of age or more were investigated, utilizing measurement of intra-ocular pressure (with Schiotz's Tonometer) in the morning and the evening, determination of PO/C value; water provocative tonometry and direct ophthalmoscopy. Selected cases were subjected to field charting and gonioscopy. Selected cases were subjected to field charting and gonioscopy for ultimate diagnosis
| Results and Observations|| |
263 adult members (age range 30.years or more) constituted the sixty five families, out of them 212 members allowed full investigations, 44 members refused measurement of facility of aquous out flow and water provocative Tonometry. Seven members were not available for any investigation.
Positive heredity was detected in seven families and 21 familial cases were found out of total 79 cases of frank OAG out of 256 investigated family members (APPENDIX - I)
Water provocative tonometry was found to be positive in 45 out of 79 frank cases of open angle glaucoma, and 10 out of 62 family members whose screening IOP was more than 21 mm of Hg. and in rest 71 members it was negative.
It appears that PO/C is more than 100 in 7 individuals whose screening 10T was more than 21 mm of Hg. But no abnormality could be detected in their field of vision and on gonioscopic examination.
| Discussion|| |
OAG is a genetically determined disorder one factor in its genesis being a hereditary tendency of higher IOP. The knowledge of genetic mechanisms involved is yet insufficient The literature has been confused by irregular sampling and failure to distinguish clearly between hereditary and chronic forms of glaucoma determined on the basis of gonioscopically visible abnormalities in the angle of the anterior chamber. Also the correlation between out flow facility and the future trend in ocular pressure has not been demonstrated. All these are negative facts for placing any figure on the increased risk in individual with possitive family history of OAG
Although not conclusively proven yet it is agreed by most authorities that glaucoma if detected early, can be treated and visual loss prevented or atleast slowed. The frequency of OAG in the relative of index patients is greater. On this background family study in OAG demands special consideration for an methodical approach for prevention of this blinding entity.
In this study as screening tool, tonometry, optic nerve head examination, water provocative tonometry, PO/ C determination were undertaken and field of vision and gonioscopy were done in selected cases, Water provocative tonometry and PO/C determination was not found adequate for screening as 44 individuals refused to under go such investigations
14 new cases had been detected in 263 children and Siblings of patients with known Glaucoma and they were not aware of the condition earlier. The same incidence in Perkins  study was 11 out of 190 family members Positive heredity could be detected in 26.6% cases of OAG and it was either recessive (52.4%) or dominant (47.5%). The incidence of heredity that were detected by different workers varied from 13.5 to 23% ,, But the fact that there might be one affected, in the family but this did not rule out heredity because of the following possibilities It might be passed as a recessive inheritance; mutation of the gene and genetic nature of glaucoma might not be independent of environmental or associated factors
Average Screening intra-ocular tension was, OD = 18.05 mm of Hg. and 05 = 17.8 mm of Hg. 24.2% relatives has intra- ocular tension more than 21 mm of Hg. (either morning or in the evening) and 10 members (16.1%) of them showed positive water provocative tonometry and in seven O/C value were more than 100, but without any field defects or gonioscopic abnormality. These findings are similar to that of Parkins  and Rankes et al ; [Table - 2][Table - 3]. In the unselected population 8.58% has intra ocular tension more than 21 mm of Hg. So this 24.2% relatives those who showing positive water provocative tonometry and PO/C values more than 100 were highly suspected for developing glaucoma. The incidence of OAG was found 79 out of 256 members in the age range over 30 years (30%), but in the unselected population the same incidence was 2-5%.
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[Table - 1], [Table - 2], [Table - 3], [Table - 4]