10.1.2.2. Hypermetropia

Hypermetropia is also known as far-sightedness. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly.

Hypermetropia occurs when the eye's lens is unable to focus on nearby objects. The reason for this is that, in individuals with hypermetropia, the near point—the closest distance at which objects can be seen clearly—is farther away than the usual near point of 25 cm. When the person is trying to read or see something close-up, the light rays from that object converge beyond the retina, causing a blurred image.

Think of hypermetropia like a camera that can focus on faraway scenes (like landscapes) perfectly but struggles to focus on things up close (like a book). Imagine trying to take a picture of your favorite book cover while standing too far away; it will turn out fuzzy, just like how someone with hypermetropia sees nearby objects.

The near point, for the person, is farther away from the normal near point (25 cm). Such a person has to keep a reading material much beyond 25 cm from the eye for comfortable reading.

People with hypermetropia often experience difficulty when trying to read or do tasks that require seeing up close. They may need to hold a book or any reading material at a greater distance than normal to see it clearly. As a result, they might face eye strain or discomfort after reading for a prolonged period.

It's like trying to read small print on a page while sitting at the back of a room; you’ll struggle to see the words clearly unless you move closer or use glasses. For someone with hypermetropia, the words remain blurry no matter how much they squint or adjust their position.

This defect arises either because (i) the focal length of the eye lens is too long, or (ii) the eyeball has become too small.

There are two main reasons for hypermetropia: First, the focal length of the eye lens can be too long, meaning it has difficulty bending light rays enough to focus them on the retina. Second, some individuals may have a smaller eyeball, which also affects where light rays converge. In both cases, the result is that light rays from close objects focus behind the retina, leading to unclear vision.

Imagine trying to shoot a basketball into a hoop from too far away; the ball lands short of the target. In a similar way, if the eye is shaped such that it focuses nearby light too far behind the retina, the image we see is blurry, like the short shot missing the hoop.

This defect can be corrected by using a convex lens of appropriate power. Eye-glasses with converging lenses provide the additional focusing power required for forming the image on the retina.

To correct hypermetropia, optometrists prescribe convex lenses, also known as converging lenses. These lenses help to bend light rays more sharply, bringing the focus point forward onto the retina instead of behind it. This adjustment allows individuals with hypermetropia to see close objects clearly.

Think of a magnifying glass: when you look at something small through it, the glass converges the light, making the object appear larger and clearer. In a similar manner, convex lenses adjust the light entering the eye so that near objects can be seen more clearly, making everyday tasks like reading books much easier.

--