Myopia occurs due to:

A. Increase in the focal length of the eye lens

B. Decrease in the distance between retina and lens

C. Decrease in the focal length of the eye lens

D. Increase in the distance between retina and lens

Myopia, commonly known as nearsightedness, is a condition where distant objects appear blurry while close objects can be seen clearly. To understand what causes myopia, let's break down the options you've provided.

Understanding Myopia

Myopia occurs when the eye's shape causes light rays to focus in front of the retina instead of directly on it. This can happen for a couple of reasons, primarily related to the eye's anatomy and the way it refracts light.

Analyzing the Options

• A. Increase in the focal length of the eye lens: This option is incorrect. An increase in focal length would mean that the lens is able to focus light further away, which is not the case in myopia.
• B. Decrease in the distance between retina and lens: This option is plausible. In myopic eyes, the eyeball is often longer than normal, which decreases the distance between the lens and the retina, causing light to focus in front of the retina.
• C. Decrease in the focal length of the eye lens: This is also a possible cause. If the focal length of the lens decreases, it means the lens is bending light more sharply, which can lead to focusing in front of the retina.
• D. Increase in the distance between retina and lens: This option is incorrect for myopia. An increase in this distance would typically lead to hyperopia (farsightedness), where distant objects are seen more clearly than close ones.

Correct Answer and Explanation

The most accurate answer to the question is B. Decrease in the distance between retina and lens. This is because in myopia, the eye is often longer than average, which means the distance from the lens to the retina is shorter than it should be for proper focus on distant objects.

Visualizing the Concept

Think of the eye as a camera. If the film (retina) is too close to the lens, the image of distant objects will be out of focus, similar to how a camera would blur distant scenes if the film is positioned incorrectly. In contrast, if the film is too far away, the camera would struggle to focus on close objects, which is what happens in hyperopia.

Implications of Myopia

Myopia can be corrected with glasses or contact lenses that help to diverge light rays before they enter the eye, allowing them to focus correctly on the retina. In some cases, surgical options like LASIK are available to reshape the cornea and improve focus.

In summary, myopia is primarily caused by a decrease in the distance between the retina and the lens, leading to improper focus of light rays. Understanding this condition helps in managing it effectively, whether through corrective lenses or other treatments.