JOIN USOur eye is like a camera; it can focus on different distances with such ease that we don’t even notice it zooming in or zooming out. The focusing ability is made possible by the action of the lens inside our eye. If this lens is not flexible enough or if the focusing is ‘stuck’ in one position, it can cause eye fatigue. The typical symptom experienced when this happens is that of blurred vision, especially after reading or working on computers, or doing any near-vision task (for instance, sewing) for a prolonged duration.
Problems galore
Similarly, our two eyes can ‘run’ between different distances in physical space. The two eyes converge when we look at objects up close and can diverge when we look at objects at very far distances. This running between the distances is also done by our eye muscles with ease. If there is a muscle weakness, it can also cause eye fatigue. The typical symptom experienced due to this problem is seeing double, or skipping lines while reading.
Besides the focusing (accommodation disorders) and muscle problems (vergence disorders), eye fatigue can also be caused due to other reasons such as improper or infrequent blinking, not wearing optimal spectacle correction for refractive errors, poor lighting conditions, improper reading posture, etc. Eye fatigue can also result in headaches and sleepiness, besides eye strain, burning sensation and/or red eyes.
To diagnose the exact cause of eye fatigue, a detailed orthoptics evaluation is important. This test investigates to see the maximum ability for focusing, converging, and the flexibility of these mechanisms. Whether these values are age-appropriate is also assessed.
Sometimes constant near-work can induce myopia (near-sightedness) by straining the muscles of the focusing lens. Relaxing the ‘over-focused’ lens removes this myopia. The condition therefore is called ‘pseudomyopia’. Unfortunately, in some cases, when patients go for eye testing, a minus spectacles gets prescribed for the ‘over-focused’ condition of the eye. This further aggravates the eye strain.
So anyone having a need to frequently (less than three to six months) change their spectacles, or having eye strain that is not getting solved with spectacles, will also require a detailed binocular vision examination.
Good reading or near-work habits does help to prevent eye strain to some extent. This would mean having good lighting, reading in a good posture, not stooping over the reading material, and not holding the reading material too close to the eye.
(The author is an associate research optometrist, Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Hyderabad.)