Hypermetropia, or farsightedness, is primarily caused by the shape of the eye, specifically if the eyeball is too short or if the cornea or lens doesn't properly focus light. This results in light focusing behind the retina, rather than directly on it.
Here's a more detailed breakdown:
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Short Eyeball: In many cases, hypermetropia develops because the eyeball is shorter than normal. This means the distance between the lens and the retina is reduced, leading to the focal point of the image landing behind the retina.
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Corneal Curvature Issues: The cornea, the clear front surface of the eye, plays a significant role in focusing light. If the cornea is too flat, it won't bend light sufficiently to focus it correctly on the retina.
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Lens Problems: Similar to the cornea, the lens inside the eye also contributes to focusing. If the lens doesn't have enough curvature or has difficulty changing shape to focus (accommodation), it can lead to light focusing behind the retina. This is particularly common with age (presbyopia), though it can also occur independently of age.
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Weakened Eye Muscles: In some cases, especially among younger individuals, the eye muscles may not be strong enough to properly focus light on the retina, leading to hypermetropia.
In summary, hypermetropia is usually the result of the eye's physical structure preventing light from focusing correctly on the retina, whether due to a shorter eyeball, a flatter cornea, lens abnormalities, or issues with eye muscles.
