When does the patient experience blurry vision?

The patient experiencing blurry vision when reading for long periods can be attributed to a condition known as asthenopia or eye strain. This occurs because prolonged focus on near tasks, such as reading, requires significant effort from the eye's ciliary muscles to maintain focus. Over time, this can lead to fatigue of the eye muscles, resulting in blurred vision. Additionally, factors like lighting conditions, the distance of the reading material, and existing refractive errors (such as myopia or hyperopia) can exacerbate this blurriness while reading.

In contrast, blurry vision after exercising may be related to other physiological factors, such as temporary changes in blood flow or oxygen levels, but it is not as commonly associated directly with eye strain as reading is. Similarly, while using electronic devices can also contribute to eye strain, the nature of sustained focus and potentially improper ergonomics while reading makes it a more classical case for causing blurry vision. Outdoor activities typically involve varied distances and different lighting conditions, which generally don't contribute to blurry vision in the same way that prolonged near tasks do.