Welcome to HCM.
What you have experienced is termed as flashes and floaters
in eye along with blackouts. Since you are hypertensive and with your age in mind,I would suggest you to visit an ophthalmologist , to have a dilated retinal examination done.
Aging itself or your systemic problem (HTN) could have caused some changes in either the jelly within the eye ( vitreous) or the retinal vessels.
So get a through examination done and get a cardio work up (ECG, Carotid doppler) done to rule out and small blocks in the blood vessels.
Take care and keep us updated.