Myopia (short sight)
Myopia is the clinical term for short sight. It is a condition of the eye where the image falls in front of the retina rather than on the retina because the eye is too long. This means that objects in the distance are blurred. A concave lens is required to push the image back on to the retina thus making the vision clearer.

Hypermetropiaor Hyperopia (long sight)
Hypermetropia or long sight is the converse of myopia. Here the image falls behind the retina because the eye is too short. In this case, objects that are nearby are more blurred compared to distance objects. Convex lenses are required to move the image forward on to the retina.

Astigmatism is a condition in which there is an irregularity to the front of the eye, the cornea. A normal cornea is spherical, rather like a football. This means that when light enters the eye, the cornea refracts the light evenly. In an astigmatic eye, the cornea is more rugby ball shaped and so light is bent more unevenly on to the retina, creating a blurred image. Astigmatism is very common and generally accompanies either myopia or hypermetropia.

Presbyopia is the normal loss in the eye’s ability to focus on near objects. Typically, this takes place after 40 years of age and occurs because the natural lens in the eye becomes harder and less flexible. This means that the eye can no longer accommodate (this is the eye’s natural focusing mechanism) as efficiently. Myopia, hypermetropia, astigmatism and presbyopia can all be easily corrected.

This is the term used to describe a lazy eye and occurs because the eye hasn’t developed normally. The natural development of the eye takes place up to the age of approximately 8 years and requires a clear image to fall on the retina, to allow the normal formation of connections between the eye and brain. If the eye is left uncorrected during this critical period, the blurred image will mean poor connections will be made and result in amblyopia.

Strabismus (squint)
A strabismus, commonly referred to as a squint, is when the two eyes are not straight resulting in a misalignment of the visual axes. An inward turn is called an esotropia and an outward turn is an exotropia. Strabismus can present as an adult but is more commonly noted in children. In most of these cases, the cause is unknown and where it is present from birth, it is known as a congenital strabismus. With strabismus, because the eyes are misaligned the brain can be confused by the two different images that it receives from each eye. In children, the brain may learn to ignore the image from the weaker eye (suppression) and if left untreated, this could lead to a lazy (amblyopic) eye. Sometimes, the lazy eye can cause the strabismus. A strabismus can also present itself after traumatic brain injury, certain toxins, systemic disease or after vision loss from ocular disease or injury.