Bright Sight

Oliver Backhouse, Consultant Eye Surgeon www.cataract.org.uk

Astigmatism

Managing Astigmatism Toric Lenses

Astigmatism is when the eye has two different planes of focus. This produces a blurred image on the retina and so the sharpness of visual acuity is reduced and images appear ghosted. Sometimes people will say that the front of the eye (cornea) is rugby ball rather than football shaped as so one can understand how light can be bent to differing amounts. Astigmatism is common being present in approximately every 1 in 3 people. The degree it affects vision varies according to how much astigmatism there is.

Glasses can correct the effect of the unequal focus planes but often glasses and contact lenses are inconvenient in our modern lifestyles. With advancing technology it is now possible to successfully correct astigmatism on a permanent basis. Not all astigmatism is detrimental as a small positive axis at 90 degrees can improve overall vision.

distorted landscape

Before

sharp landscape

After

Limbal relaxing incisions are controlled cuts into the cornea to relax it in the desired axis so making the cornea more football shaped and hence give sharper visual acuity. They have been used for many years but can be quite varied in their effect and so are occasionally unreliable. Laser surgery can also correct some astigmatism but recent attention has moved to implantable lenses inside the eye these are called Toric Lenses.

Toric lenses have 2 different planes of focus and so need to be placed in the eye at a precise axis to neutralize the astigmatism from the cornea. Should there be a coexisting cataract as well or high refractive error (short or long sighted) in patients over 40, then a Toric lens such as the Lentis Toric can replace your own lens and both correct the distance refractive error and the astigmatism but near vision glasses will be needed after. The revolutionary individual custom made multifocal Comfort Toric lens can now give both unaided distance and near vision while correcting the astigmatism as well. Due to the enormous success of modern lens surgery, this type of operation can be done as a day case procedure under no needle eye drop anaesthesia. As with other surgery the success of the operation depends on the expectations, lifestyle and anatomy of the eye.