What is eye strain?

Structure and Function of the Eye

The eye has a structure similar to that of a camera. The cornea and crystalline lens are equivalent to the lens of a camera. The cornea takes in light and refracts it, while the crystalline lens adjusts the focus by thickening or thinning due to the surrounding muscles (ciliary muscles). The retina on the inner wall of the eye acts as the film of a camera or the sensor of a digital camera, forming an image and distinguishing the color and brightness of the subject.

The difference between tired eyes and eye strain

Everyone can experience eye fatigue. Eye fatigue that is temporary and improves naturally with rest or sleep is called “tired eyes.” It is also called “eye strain” and has almost no effect on the body. On the other hand, there are cases where rest alone does not improve the condition, and thiscondition is called eye strain. Eye strain not only causes various symptoms in the eyes when the eyes are used to a degree that would normally cause no symptoms, but also affects other parts of the body. Eye symptoms include “tired eyes, blurred vision,” “painful eyes, bloodshot eyes,” “heavy, watery eyes,” “glare,” and “tears.” In addition, since vision is achieved through the collaboration of the eyes and brain, if the burden is too great, it is likely to manifest as systemic symptoms such as headaches, dizziness, nausea, stiff shoulders, lethargy, and fatigue. Both eye fatigue and eye strain are not names of diseases but names of symptoms and conditions.

Causes of eye strain

*The underlying disease must be diagnosed by a doctor.

If you are worried, see a doctor as soon as possible.

Eye strain

When people with refractive errors such as farsightedness, myopia, and astigmatism, or presbyopia, use their eyes for long periods of time, they must constantly adjust their crystalline lenses to focus. This puts strain on the ciliary muscles, which adjust the focus, and causes eye strain. For example, this can happen when you overuse your eyes by using glasses or contact lenses that are not the right prescription, or when you are in the early stages of presbyopia and work too close to your eyes. In addition, in modern society, it is essential to work using display screens such as computers and smartphones (VDTs). It is said that long periods of VDT work can easily cause eye strain, and VDT work can cause various bad symptoms in the whole body, such as the neck, shoulders, waist, and back, in addition to eye symptoms. This is called VDT syndrome. In particular, when working on a smartphone or other screen that is close to the eyes, advanced functions are required to adjust the focus and position the eyes at the same time, which puts a lot of strain on the eyes and brain, leading to various symptoms related to eye strain.

Dry eyes

Dry eye is a condition in which the amount of tears on the surface of the eye is reduced or the quality of the tears changes, resulting in a lack of moisturizing power for the surface of the eyeball. It is common among middle-aged women, and there are said to be approximately 8 to 22 million patients in Japan, with the number continuing to increase. Dry eye can cause various symptoms, such as a decrease in the function of tears, which makes them more likely to evaporate and makes the surface of the eye more susceptible to damage. Eye strain is one of these symptoms. Even if there is no damage to the surface of the eye, an unstable tear film can cause tension in the muscles around the eyes, leading to eye strain. In addition, in cases of intractable dry eye, blepharospasm should also be suspected.