Do not look into the sky without special sun glasses! That kind of advice was given by doctors when the moon blocked the sunlight travelling to Earth in a partial eclipse five years ago. The reason, of course: Intense sunlight damages the eyes. However, light has its good sides as well - the right dosage of radiation can be useful. And patients with cataract may take profit from a new technique using UV light being applied in Germany in two university hospitals: A special lens implanted in patients’ eyes can be adjusted with UV light. The name of the product: light adjustable lens (LAL).
Patients with cataract have long been treated with artificial lenses. In Germany, such surgical procedures are realised about 600,000 times per year and thus are routine for physicians. “Since April 2008 we have implanted the new lens into 23 patients. The treatment has been completed in 12 patients so far”, Dr Fritz Hengerer explains, assistant medical director of the minors’ association hospital Bochum-Langendreer at the Ruhr-University of Bochum, Germany. All patients are very satisfied according to Hengerer.
Light influences the refractive power
The light adjustable lens is constructed just like the standard lenses. The new feature about LAL is that it contains photosensitive molecules which are not bound together. These molecules move around when they are irradiated with UV light. Depending upon the light's intensity the lens contracts or contracts – near-sightedness or long-sightedness can be adjusted for. The process can be repeated several times until the favoured state of vision is achieved. At the end of the procedure that takes place after surgery a “log in” needs to be accomplished: The lens will be irradiated with a certain light intensity and the refractive power will be fixed permanently. According to the scientists, this procedure can also help with astigmastism.
“During a standard surgery with a standard lens the patient's refractive power is to be determined. However, despite modern diagnostics 30 per cent of the patients still need glasses afterwards“, explains Professor Chris Lohmann, director of the ophtahlmology clinic and outpatients department of Munich Technical University. “You can never predict how the lens will behave inside the eye“, annotates his colleague Hengerer in Bochum. “If the capsular bag shrinks the implant can slide forward or sideways. This again can affect the refractive power,” he adds.
At the University of Barcelona, Spain, the lens has been tested since 2006. “450 patients were tested in all. There are no negative results“, Lohmann says. Since the new lens is implanted like a standard lens the operation risk is the same. One thing differs between the two procedures though: “The patient has to wear sun-glasses until the wounds have healed completely in order to prevent visual acuity from changing.“
LAL not suitable for any patient
LAL can only be used with specific patients though. The pupil must be able to widen. “If a patient takes medicine which influences the width of the pupils the new lens cannot be implanted“, Hengerer points out. The same is true for a change of the eyeground as is the case with macular degeneration. „If a patient has available an eyesight of ten per cent only due to macular degeneration and a cataract at the same time the new lens is of no use“, says the ophthalmologist. In this case the eyesight depends on the macular degeneration and not on the cataract.
LAL only compensates near- or the farsightedness. Plus: If the eye is corrected in terms of nearsightedness the patient might need glasses for seeing things far away anyhow. However, according to experts this may change in the near future because the potential of the lens is going to be explored further.
The custom-made lenses have their price, though. A complete therapy of one eye costs around 3,200 Euros. Health insurances do not pay for it. "In December 2007 the lens received the CE-identification for the European and the FDA-identification for the American market“, explains Hengerer. Although the LAL was developed in the USA, it has only been introduced in Europe so far. “But the USA will follow within a short time“, so he thinks.