The main purpose of this study is to learn more about how Rocklatan eye drops affects blood flow in the eye. The secondary purpose is to see if our study devices can detect changes in blood flow before and after instillation of Rocklatan.

Inclusion Criteria:

1. Patients with both eyes with open angle glaucoma.
2. Abnormal VF (glaucomatous pattern with PSD abnormal at p<0.05 or GHT outside normal limits) on most recent two clinic visits on chart review
3. Glaucomatous disc abnormality on chart review and confirmed on baseline disc photograph
4. Overall average NFL thickness > 55 μm measured by Heidelberg Spectralis OCT -Glaucoma Module Premium Edition (chart review), consistent with early glaucoma
5. NFLP-CD deficit (below 5 percentile of normal) in any of the 8 sectors on the initial baseline visit
6. The difference in baseline NFLP-CD between the left and right eye should be less than 5% (% of area).
7. IOP >= 17 mm Hg on the most recent two clinic visits (chart review) after monotherapy with latanoprost in both eyes.

Exclusion Criteria:

1. Best corrected visual acuity worse than 20/30 on chart review of most recent clinic visit
2. Age < 21 years at baseline
3. Eye disease that could affect VF, NFL thickness, or NFLP (e.g., visually significant cataract, AMD, diabetic retinopathy, and optic neuropathy) at any study visit
4. OCT and OCTA scans not meeting quality criteria at baseline
5. Inability to cooperate with study procedures
6. Inability to commit to the study visits

The investigator will assign one eye to use the study drug, while the other eye (control) will remain on the clinically prescribed medication. The identity of the eye drop will be masked to both participants and study personnel who perform testing procedures or data analysis. The university research pharmacy will provide label masked bottles for each eye.