Frequency of Normal-Tension Glaucoma in Suspected Cases of Primary Open Angle Glaucoma

Abstract

Purpose: To study the frequency of normal-tension glaucoma (NTG) in suspected cases of primary open angle glaucoma (POAG).

Materials and Methods: A descriptive cross-sectional study was done of 150 patients who attended the glaucoma clinic during one year from January 2005 to January 2006. A detailed history was obtained and a thorough ophthalmic examination was performed, including gonioscopy, ophthalmoscopy, applanation tonometery and automated perimetery.

Results: Out of 150 patients of POAG 33 patients (22%) were found to have NTG with mean age 56 ±9.21 years. Mean age of POAG group was 52.5% (±8.7). Of the 33 cases of normal-tension glaucoma 22 patients (66.6%) were male and 11 cases (33.4%) were female, while in POAG 82(70%) were male and 35 (30%) were female. Family history of glaucoma was positive in 42% of NTG cases and 32% of POAG. 82% of NTG and 79.4% of HTPOAG population were ametropic, with mean cup-to-disc ratio 0.5 ±0.24 and mean IOP was 15.13 ± 3.60 mmHg in NTG and 28 mmHg (±6.5), 0.46 (±0.22) in POAG. Maximum IOP in NTG group was 21 mmHg and minimum IOP was observed as 08 mmHg, while these values observed as 50 mmHg and 10 mmHg respectively in POAG. Decreased vision was main complaint of NTG patients, headache was observed in maximum number of POAG patients.

Conclusion: NTG remains a difficult diagnosis for ophthalmologist who favors the argument that raised IOP is essential for the diagnosis of POAG. NTG changes the definition of glaucoma and our concept of IOP as a sole etiological factor is now out dated. The overall frequency of NTG in the current study was 22% among suspected cases of POAG.