Is a condition that occurs when the eye, in its relaxed state, is looking at an object in the distance and the object is blurred (in varying degrees). This is due to: light rays coming from the object are brought to a focal point in front of the retina. Because the focal point forms in front of the retina the image formed on the retina will be blurred. A shortsighted person is unable to improve their distance vision by altering their accommodation, but near vision is usually good without the aid of spectacles.
Is a condition that occurs when the eye is looking at a distance object (in its relaxed state) and the light rays coming from the object are brought to a focal point behind the retina. This will produce a blurred image on the retina. A hyperope is usually able to improve their distance vision through focusing, however this will often cause eyestrain and /or headaches.
Astigmatism (the image that one is looking directly at, fail to come into focus on the retina) caused by differences in the curvature in different meridians of the refractive surfaces of the human eye, so that light rays are not sharply focused on the retina. In other words: whatever one is looking at, the image on the retinal surface of the eye is distorted due to structural differences in the curvature of the refracting (light bending through a surface) surfaces of the human eye.
The corneal (front) surface of the eye with the tears form a spherical shape, something like a nicely rounded smooth soccer ball however, with astigmatism, the curve may be different in one meridian (e.g. 90 degrees) with respect to an opposing meridian (e.g. 180 degrees), therefore, light travelling through the eye will be uneven and distorted, causing the object of regard to be uneven and distorted. This will impair focusing ability thus resulting in a blurring effect of part of the object of regard.
Astigmatism is a common condition, often in mild cases going unnoticed, although a moderate to severe degree of astigmatism will cause eyestrain, headaches added to blurred vision. The treatment will be spectacles or contact lens use.