Definition of the farsightedness eye
Nearsightedness or hyperopia is an optical eye abnormality in which the eye cannot see a near point clearly, or the near point looks blurred. Although it is difficult to observe a near point, people with nearsightedness can see the far point. The near point is the closest distance that can be seen by the normal eye. The average normal-eye has a point near 25 cm. The far point is the farthest distance that can be seen by normal eyes. The average normal-eye person has an infinite point. Infinite is a term used to describe the length of a very distant object.
The cause of the farsightedness eye
Normal eyes can see a near point clearly because the beam of light is focused right on the retina. If the nearsightedness cannot see the near point, then the beam of light is not focused on the retina. In the average human normal eye, the beam of light can be focused precisely on the retina when the near point is 25 cm, and when focusing the near point, the curvature of the eye lens is worth a maximum. So the point close to 25 cm is the smallest distance where the radius of the curvature of the eye cannot be reduced again.
Nearsightedness eyes cannot focus near points within 25 cm of the eye. Therefore, nearsighted eyes have a focal length and radius of curvature greater than normal eyes. Refracting the light is done by cornea and lens so can be concluded that nearsighted eyes have a cornea and a lens that is less curved or flatter so that the radius of curvature and focal length of the nearsighted eyes are greater while the normal eye has a cornea and a more curved lens or less flat so that the radius of curvature and focal length are smaller.
Based on the previous explanation, it can be concluded that the cause of nearsightedness is the cornea and the lens of the eye is less curved than it should be as in a normal eye so that the focal length of the cornea-eye lens system is more significant, causing the beam of light from the near point to be focused not precisely on the retina but focused behind the retina. The beam of light of the near object is not focused on the retina so that the nerve cells in the retina cannot convert these light waves into electrical signals which are then passed on to the brain.
Another cause of someone suffering from nearsightedness is that the horizontal part of the person’s eye is too short so that the beam of light refracted by the cornea and lens falls behind the retina.
Hyperopia is the same as presbyopia. Presbyopia is an eye disorder in which the ability of the eye to accommodate is reduced so that the near point away as age increases. Presbyopia is caused by age, while genetic or hereditary factors cause hyperopia.
The solution of the farsightedness eye
Nearsightedness eyes focus the beam of light from the near point behind the retina. For nearsightedness to be normal, the beam of light must be focused on the retina. The beam of light can be focused on the retina when placed in a converging lens or convex lens or positive lens, in the front of the eye. Convex lenses help collect light beams so they can focus right on the retina.
In everyday life, nearsighted eyes can be normalized using eyeglass lenses or contact lenses. Detailed mathematical explanations and calculations on this subject can be studied in writing about eyeglass lenses and contact lenses.