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The description fits
with 'vasovagal syncope'. This means in simpler terms an episode of giddiness, followed by loss of balance and sometimes fall. There is sudden reduced blood supply to brain due to low blood pressure and hence transient loss of eye sight.
However, it would be advisable to see a physician as certain medical problems like rhythm disturbances need to be ruled out.
Occasionally, low blood sugar/heavy physical exertion/ very hot and moist weather can also lead to this.
I hope your physician will check you over and will be better able to guide you further in this matter.
Dr Tejas Shah