The eyes are in different states when looking far or near - What is eye adjustment?

The human eye is a very sophisticated device. When we switch from "looking far" to "looking near", the eye's "adjustment" mechanism will automatically get involved. To understand the eye's adjustment mechanism, you need to have a certain understanding of the basic structure of the eyeball. I recommend you to read another article by Dr. Jingcai, "Small Eyeball, Big Knowledge".

The so-called "accommodation" is a natural neural reflex when the eyes look at something close. It includes:

Lens accommodation. When looking at something close, the ciliary muscle becomes tense, causing the lens to rebound due to its own elasticity and become more "convex";

Adjustment of pupils. When looking at something close, the pupils will shrink accordingly;

Eye convergence. When looking at something close, the two eyes converge toward the nose. This phenomenon is also called the "convergence reflex" of the eyes.

To put it simply, when looking far away, the eyes do not "use effort" or "struggle", but the opposite is true when looking at close objects. The adjustment mechanism is activated and the eyes need to "use effort".

What is the relationship between accommodation and myopia? Among the mechanisms of myopia, the "accommodation lag theory" is one of them. This theory believes that when you look at close objects for a long time, the ciliary muscles will contract and spasm, and when you look at distant objects, the accommodation cannot be relaxed in time, the lens is still in a thickened state, and the focus is formed in front of the retina, resulting in pseudomyopia, which will form true myopia over time.

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About Dr. Jingcai: The creators of Dr. Jingcai's popular science content all have a professional background in ophthalmology, a master's degree or above, and are former ophthalmologists. For some popular science content with a higher degree of professionalism, we will also invite working ophthalmologists and optometry experts to review and check it, striving to be responsible for the accuracy of the content and avoid misleading readers.