Your symptom is suggestive of TIA( transient ischaemia attack) /Amaurosis
It is due to temporary loss of blood flow in the retinal blood vessels due to the embolus( from Carotid artery)blocking it. This is very common in Carotid artery disease
)with a high risk if you are a Diabetic or Hypertensive or Having high Cholesterol
The first thing you have to do is
-to get an ophthalmologist opinion to confirm the diagnosis and
- a Cardiologist opinion who will require Other investigations (ECG , ECHO and blood investigations along with a MRA to find out the blockage) and to start you on treatment accordingly.
Do not panic. This is a diagnosis based on your description of your symptoms provided. A direct retinal examination is required to confirm this.
So consult at the earliest to avoid recurrent episodes which may permanently bother your vision.
Take care and let us know after your direct examination.