Myopia, Hyperopia and Astigmatism
It is a very common condition in which the cornea has an asymmetric curvature, causing blurred and distorted vision. The cause of astigmatism is unknown. It is usually present from birth and is often associated with myopia or hyperopia. Patients with astigmatism have difficulty identifying small details, both from close up and from a distance. A minimum value of astigmatism is considered normal and does not require any correction.
Hyperopia is a visual condition in which the visual image is focused behind the retina, due to a too small eyeball or a too weak ocular dioptric power. It is often present from birth, even if children are able to compensate for the deficit exploiting increased accommodation. Symptoms involved by uncorrected hyperopia include headache while reading, blurred vision when looking into the distance and sometimes eye pain.
A myopic (short-sighted or near-sighted) person sees near objects clearly, while those in the distance are perceived blurred, which is why he tends to screw up his eyes to look into the distance. In the presence of myopia, images are focused in front of the retina, in most cases because the eyeball is longer than normal.
The symptoms suffered by patients with uncorrected myopia include blurred vision when looking into the distance, eyestrain and headaches..
Presbyopia is characterized by the progressive loss of the ability of accommodating the crystalline lens, resulting in difficulty in focusing on near objects.
The process of reduction in lens elasticity typically starts around the age of 45, when the patient begins to experience a decreased ability to focus on near objects accompanied by visual fatigue and sometimes headaches.
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