What is Presbyopia and what causes it?
A large number of the human population between 40 and 50 years old, with normal eyes, looses their ability to focus at a close range and this is termed Presbyopia. This long-sightedness may worsen over time but will eventually stabilise at around 60 years of age.
In a youthful eye, the lens is supple and elastic and when a person focusses at a close range the siliary muscles on the outside contract, causing the lens to become rounder. With the aging process the lens becomes less flexible, thus when the siliary muscles contract, the lens does not become as round and therefore focussing at close range is harder.
Presbyopia can be treated with reading glasses, contact lenses, monovision (one eye sees close and the other one far), multifocal laser treatment and clear lens exhange with a multifocal IntraOcular Lens (IOL) implant.
Presbiopic Clear Lens extraction with multifocal IOL implant
During this procedure the old lens is replaced with a plastic multifocal IOL that will last a lifetime. The procedure is exactly the same as a standard lens replacement during a cataract operation, when a cataract lens is replaced with an intraocular lens.
How does the IOL work?
The multifocal IOL works on the basis of light distribution. It is designed in such a way that the light required for both far and near vision is constantly available and correctly refracted. When a patient looks at a specific distance, all images are available, however, the brain chooses the best image for that specific distance in order to ensure good vision.
Approximately 55% of light are used for distance vision and 35% for near vision, with only 10% of the light lost. The effectiveness of the human eye in various lighting degrees makes this 10% loss almost no problem, exept when reading in low light.
Advantages of a multifocal IOL implant
• Almost immediate results can be observed with both near and far vision.
• For most patients spectacles may become obsolete.
• Good vision will be sustainable provided that a patient’s eyes stay in good health
• The implanted multifocal IOL’s differ from multifocal glasses in that focussing at a specific distance does not require the patient to look up or down at a specific angle.
Disadvantages of a multifocal IOL implant
• The operation is not covered by the medical aid, as it is seen as cosmetic surgery.
• Some patients experience an adjustment period to get used to the Multifocal IOL.
• Most patients experience haloes around lights in the dark, which can make driving at night difficult. However, haloes subside over time and after a year most patients don’t find them problematic anymore.
• Good light is nesassary for reading.
Why aren’t multifocal IOL’s used for all patients?
• The cost for these lenses are very high.
• Eyes with certain pathologies such as Macular degeneration does not qualify for multifocal IOL’s.
• Patient selection is important and someone with a perfectionistic or choosy character find it difficult to adjust to the various above mentioned disadvantages of this IOL.
Options for the Presbyopic patient:
• Get reading glasses, it is the quickest, safest and cheapest option.
• Monovision can be achieved with contact lenses. In addition, multifocal contact lenses are also available. However, the use of these may proof to be difficult for patients over 45 that has never used contact lenses before.
• Laser treatment resulting in monovision. This treatment results in a loss of depth perception and is not recommened for active sport people.
• Laser treatment resulting in a multifocal cornea. This process has the potential to work very well, however patient selection is very important.
• Prelex – as discussed above.