Focussing Errors

Myopia (short- or near-sightedness) is a very common focussing error in which the eye is too long for its own focusing power. Without glasses or contact lens correction, very near objects appear sharply in focus while objects appear progressively more blurred at greater distances.

Hypermetropia/Hyperopia (long- or far-sightedness) is a focussing error where the eye is too short for its own focusing power. Without glasses or contact lenses, objects appear blurred at both near and distance. Young patients with low degrees of hypermetropia may see distant objects more clearly than near, hence the name.

Astigmatism is a focussing error where the eye does not focus evenly and may be associated with long-sightedness, short-sightedness or both. The cornea is more curved in one meridian than in the other, thus the eye resembles the oval shape of a rugby ball rather than the more even, spherical shape of a football.

Presbyopia is an age related (40+) reduction in the capacity of the eye to focus on near objects. Reading, bifocal or varifocal glasses are needed to read and carry out other tasks requiring near vision. However, at this age, those who have mild myopia (short-sightedness) might be able to read close print simply by taking off their glasses. This will obviously render their distance vision uncorrected and therefore blurred.