The purpose of this study is to assess retinal blood flow and vascular reactivity in patients with newly diagnosed primary open angle glaucoma pre- and post-primary Selective Laser Trabeculoplasty(SLT). Canon Laser Blood Flowmeter will be used for the assessment of retinal blood flow.

We previously found that vascular reactivity improved after short term treatment with dorzolamide drops. It is not clear whether this improvement was a direct effect of the medication or secondary effect of the decrease in IOP. We would like to see the change of vascular reactivity before and after SLT, which will decrease the intraocular pressure without pharmacologic effect.

Inclusion Criteria:

1. Age 40-75 years (Male or Female)
2. Best corrected visual acuity of at least 20/40
3. No previous treatment for glaucoma
4. Ametropia less than ±6.0 DS and ±2.5 DC)
5. Non-smoker
6. No cardiovascular/respiratory disorders

Exclusion Criteria:

1. Past history of diabetes and cerebrovascular accident
2. Vascular occlusive disease affecting the ocular circulation such as: diabetic retinopathy, retinal vein occlusion and retinal artery occlusion
3. Previous intraocular surgery
4. Ocular media opacities limiting the use of the imaging tests

patient with untreated primary open angle glaucoma