A normal eye functions by letting light in through the cornea and the lens, which then falls on the retina at the back of the eye. The cornea accounts for most of the focusing power of the eye by refracting light into the eye. The lens, by varying its shape and further refracting the light, is responsible for fine tuning the focusing range such as focusing on near or far subjects. A highly nearsighted or myopic eye may be to extreme that a patient may not be a candidate for LASIK. Clear lens extraction, also known as ReLEx surgery may be performed.
What happens in myopia?
When an eye becomes highly myopic, the focusing elements cannot focus light from distant subjects onto the retina but instead focus it on the space in front of it. Due to this the light diverges on the retina, which appears as blurred vision. The condition can be corrected surgically through a procedure called clear lens extraction which involves removing the lens and inserting another lens of appropriate power for better focus.
Myopia is a degenerative condition and there is no cure for it, in that the progressing of the condition cannot be prevented with current knowledge. There are other complications that are associated with the progress of the condition such as cataracts and glaucoma that mainly occur in the elderly, as well as the degeneration and detachment of the retina and the vitreous humour. In many cases of cataract associated with high myopia, carrying out clear lens extraction will yield better results in the long term than removing the cataract by laser.
Before carrying out clear lens extraction, the dimensions of the eye need to be measured to determine the optimal power for the lens being implanted. This is done by ultrasonic biometry, the results of which give the ophthalmologist a good assessment of the power of the lens with which the eye can work best.
The lens implanted during clear lens extraction can be either monofocal – which have a fixed focus, or multifocal – which can focus on multiple ranges of vision. For people with astigmatism, toric lenses are available apart from other surgical alternatives after clear lens extraction.
About clear lens extraction
Clear lens extractionis carried out under anesthetic – general or local. If a portion of the eye is sliced to remove the lens and insert the replacement, the eye may evolve an irregular shape during the healing process and this may hamper vision. To avoid this, a small incision is made into the eye through which a needle is inserted. An ultrasonic transducer is inserted through the hole in the needle into the incision, and the lens is then shattered and turned into an emulsion through the emission of ultrasonic pulses.
The emulsified lens is then extracted through the needle and the replacement lens which is composed of a deformable polymer is inserted through the same hole. It then expands into the membrane of the lens in the gap left behind by the previous lens and is attached behind the pupil by haptic plates. Clear lens extraction offers good results in many cases and only some result in complications, usually due to pre-existing conditions.