Hello and thanks for your question. There are two things that may be causing this phenomenon to happen. Let me explain...
It's possible that your eyes have difficulty staying aligned together. There's a small portion of the population that has a tendency for the eyes not to stay straight and aligned together all the time. In this population, one eye can tend to drift out or in from time to time and it tends to happen most often when the person is tired or fatigued, sick, or inebriated. In your case, it's possible that the end of the day is associated with enough fatigue that you have difficulty holding your eyes straight and aligned together and so you end up with multiple, conflicting images, which resolves when you cover one eye. You may ask yourself why this wouldn't have been manifest prior to age 69, but many times a person may have just enough control over this when they are younger that it never becomes manifest until they are older and their control starts to slip. This is something that should be evident to an ophthalmologist if they are looking for it.
Second, you m ay be suffering from a dysfunctional or unhealthy tear film which can lead to poor and fluctuating vision. People who have this characteristically have more trouble towards the end of the day after they have been using their eyes all day. If this is happening more in one eye than the other, covering that eye can make this go away. The use of some artificial tears 3-4x/day for 3-4 weeks can help improve this situation.
I would recommend getting an appointment to have a complete eye examination done by an ophthalmologist (a medical doctor) and not an optometrist or optician as the medical doctor is the doctor with the most training and should be able to sort these issues out rather easily.
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My opinion is solely informative and does not constitute a formal medical opinion or recommendation. For a formal medical opinion and/or recommendation you must see an eye doctor.
thankyou for the reply as it is the first time l have used such a site l do not understand how the payment part works
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