Study of the importance of family screening of glaucoma: identifying the target

Aim: To describe the value and results of family screening of glaucoma patients in the glaucoma clinic of a tertiary center in the Garhwal Himalayan region over a period of one year. Material and Method: 300 patients underwent comprehensive ophthalmic examination and glaucoma examination including IOP measurement by Goldman applanation tonometry, binocular dilated fundoscopy with +90D Volk lens, gonioscopy using the 4 mirror Volk goniolens. Results: 300 persons detected with primary glaucoma whose families were invited to participate in the family screening initiative, there were 114 first degree relatives who attended the screening with a response rate of 32%. The relatives of probands ranged in age from 18 to 89 years with 56.8% being males. 198 were diagnosed as primary angle-closure suspects, 8 as angle-closure,238 as glaucoma suspects and 132 subjects (11.6%) had definite glaucoma. Most affected subjects were in 40-70 years. The angleclosure disease was found more in females. Conclusion: Study also found a higher prevalence of glaucoma in siblings; especially the angle-closure entity. Targeting first degree relatives of persons with primary glaucoma may offer a relatively inexpensive way of detecting glaucoma and in the identification of suspects at risk of glaucoma who may be advocated closer monitoring.


Introduction
Glaucoma is the leading cause of irreversible blindness worldwide and in India. It has been estimated that nearly 12 million Indians currently have glaucoma and this figure will increase to more than 16 million by the year 2020 [1].
Population-based studies in India suggest that more than 90% of glaucoma cases in India remain undiagnosed [2,3]. These high rates of undiagnosed glaucoma translate into significant rates of glaucoma blindness. Since visual loss from glaucoma is preventable if detected and treated early, it is imperative to have population screening. The multiple factors responsible for glaucoma, the multiple tests used to diagnose glaucoma and the low prevalence demand targeted screening of high-risk subgroups. The increased risk of glaucoma in family members of persons with glaucoma has been well recognized. Epidemiologic data from the Baltimore Eye Survey 4 confirm that a family history of glaucoma is an important risk factor. Cross-sectional studies seem to suggest close to 50% of all glaucomas to be familial and a positive family history confers a threefold increase in the risk of developing openangle glaucoma [4,5].

Aim
To describe the value and results of opportunistic family screening of glaucoma patients in the glaucoma clinic of a tertiary medical college.

Materials and Methods
Setting -This study recruited individuals of primary openangle glaucoma and primary angle-closure glaucoma diagnosed at the glaucoma services in a tertiary center in the Garhwal Himalayan region.
Duration-Study conducted over a period of one year and their families who were invited to participate in the screening program after obtaining informed consent.
Ethical consideration-The family study was approved by the Institutional Review Board and Ethics Committee of

Tropical Journal of Ophthalmology and Otolaryngology
Available online at: www.medresearch.in 64|P a g e the concerned hospitals and was conducted in accordance with the relevant declaration of Helsinki specifications.
Sampling methods-All consecutive persons with newly diagnosed primary glaucoma in the study period were explained about the glaucoma family screening initiative by a study coordinator and requested to provide the name, age, sex, nature of relationship and mailing address of their first degree relatives. Informed consent was obtained from all probands to contact their first degree relatives to invite them to participate in the screening to detect glaucoma. The patients were shown a video film and given a brochure emphasizing family screening.
The subjects underwent a comprehensive ophthalmic examination and glaucoma examination including IOP measurement by Goldman applanation tonometry, binocular dilated fundoscopy with +90D Volk lens, gonioscopy using the 4 mirror Volk goniolens. The present study included for analysis only the family members who were subject to a complete ophthalmologic evaluation by the study team to confirm or exclude glaucoma. The family members were divided as Type I (Parents/children) or Type II (siblings). Data analysis-Statistical analysis was done by statistical software STATA 11.0. Chi-square test, independent t-test and paired t-test used. A P-value of less than 0.05 consider ed statistically significant.

Results
Of the 300 persons detected with primary glaucoma whose families were invited to participate in the family screening initiative, there were 114 first degree relatives who attended the screening with a response rate of 32%. The relatives of probands ranged in age from 18 to 89 years (Mean 54.85 ± 10.2 years) with 56.8% being males. Out of 114 subjects screened; 198 were diagnosed as primary angle-closure suspects,8 as angle-closure,238 as glaucoma suspects and 132 subjects(11.6%) had definite glaucoma. Most affected subjects were in 40-70 yrs. The angle-closure disease was found more in females. Also, a better review followup of the primary patient and family members was noted (95%).

Discussion
Prior studies have indicated that primary open-angle glaucoma is more likely to affect persons with a family history of the disease and positive family history has been assumed to be associated with a significant risk of glaucoma [5,6,7]. The Rotterdam eye study had reported a 10% prevalence of glaucoma in siblings as against 1.1% in off-springs of persons with glaucoma [8]. Nguyen et al had also reported that siblings among the first degree relatives have the highest risk of glaucoma [9,10]. The present study also found a higher prevalence of glaucoma in siblings; especially the angle-closure entity. The current study found a higher prevalence of definite glaucoma in this cohort than in a general population. Very few published Indian studies are available on family screening of glaucoma.
Tropical Journal of Ophthalmology and Otolaryngology Available online at: www.medresearch.in 65|P a g e Targeting first degree relatives of persons with primary glaucoma may offer a relatively inexpensive way of detecting glaucoma and in the identification of suspects at risk of glaucoma who may be advocated closer monitoring.
Additionally, screening at-risk population benefits in terms of glaucoma awareness, better follow-up and also increase in outpatient clinic volume.
Limitations-Although the study includes 300 subjects, still more can be recruited for the study along with the duration of the study which can be increased.

Conclusion
There is a higher prevalence of definite glaucoma in this cohort than in a general population. Very few published Indian studies are available on family screening of glaucoma.

What does the study add to the existing knowledge?
Additionally, screening at-risk population benefits in terms of glaucoma awareness, better follow-up and also increase in outpatient clinic volume.