Corneal Topography
The cornea is the front surface of the eye. Ideally, the cornea should be symmetrically shaped for optimal vision (i.e. the shape of a basket ball). Certain corneal conditions exist where this is not so, such as astigmatism, keratoconus and pellucid marginal degeneration. The assessment of these conditions can be accurately carried out with corneal topography. A corneal topographer is an instrument which uses a precision calibrated camera to map the shape of the front of the eye. A corneal topographer is also a must for Ortho-K, as the shape of the cornea must be assessed accurately. Corneal topography is also useful for screening candidates who are likely to be successful for LASIK eye surgery.
Astigmatism
Astigmatism causes blur at both distance and near. It is (usually) caused by a cornea which is not symmetrically shaped, and can be likened to the surface shape of a football. This causes light rays to be bent differently depending on the direction they are entering the eye, and hence causing blur. Less frequently, astigmatism may be due to irregularities in other components - such as the lens of the eye. Astigmatism can be corrected by spectacles, contact lenses or Ortho-K.
Keratoconus
Keratoconus is a progressive, non-inflammatory thinning and protrusion of the central cornea usually manifesting itself in youth or adolescence, although the age of onset can be anywhere between 7 and 50. It is nearly always bilateral, although it is often asymmetrical. Considerable visual impairment can result due to the development of a high degree of irregularity associated with this front surface ("window") of the eye. Due to this marked distortion and irregularity the improvement in vision obtained with spectacles may be minimal. There is usually a marked improvement in vision if rigid contact lenses (or similar) are fitted and they are often the only adequate means of correction for patients suffering this condition. Keratoconus does not cause blindness, although sometimes corneal grafts are required if the cornea becomes opaque.
Read more about astigmatism and keratoconus, and correction options available.
Pellucid Marginal Degeneration
This is similar to keratoconus, except the corneal thinning occurs much closer to the border between the cornea and the white of the eye.
Astigmatism
Astigmatism causes blur at both distance and near. It is (usually) caused by a cornea which is not symmetrically shaped, and can be likened to the surface shape of a football. This causes light rays to be bent differently depending on the direction they are entering the eye, and hence causing blur. Less frequently, astigmatism may be due to irregularities in other components - such as the lens of the eye. Astigmatism can be corrected by spectacles, contact lenses or Ortho-K.
Keratoconus
Keratoconus is a progressive, non-inflammatory thinning and protrusion of the central cornea usually manifesting itself in youth or adolescence, although the age of onset can be anywhere between 7 and 50. It is nearly always bilateral, although it is often asymmetrical. Considerable visual impairment can result due to the development of a high degree of irregularity associated with this front surface ("window") of the eye. Due to this marked distortion and irregularity the improvement in vision obtained with spectacles may be minimal. There is usually a marked improvement in vision if rigid contact lenses (or similar) are fitted and they are often the only adequate means of correction for patients suffering this condition. Keratoconus does not cause blindness, although sometimes corneal grafts are required if the cornea becomes opaque.
Read more about astigmatism and keratoconus, and correction options available.
Pellucid Marginal Degeneration
This is similar to keratoconus, except the corneal thinning occurs much closer to the border between the cornea and the white of the eye.
