What could be the reason for occasional blurred vision and tiredness of eyes?

Many causes: Syncope, mild double vision due to many causes, TIA etc can cause. Your problem include cardiac etc causes for syncopr.

Tired eyes : This could be due to dry eyes. Using artificial tears, taking breaks from intense computer work or reading, may also alleviate some of the strain. A good exam with an eye doctor will help you uncover any other issues.

Dry eye: The number one cause for intermittent blurred vision, especially when associated with tired eyes is dry eye. Try some warm compresses and otc lubricating drops for a few days. If your symptoms continue, see your ophthalmologist.

Dry eyes: There can be many reasons, however the most common reason 99% of time would be dry eyes or ocular surface disease.

Time for eye exam: Tired eyes are often a sign of either dry eyes or eye strain. Both can be related to long hours spent on a repetitive near task (like being on the computer for hours) and can also be caused by a need fro prescription glasses. Occasional blurred vision can be related to dry eyes or prescription changes also. You would be well off having an eye exam to be sure.