The emphasis in cataract surgery has moved from a technique primarily concerned with the safe removal of the cataractous lens to a procedure refined to yield the best possible postoperative refractive result, enabling the patient to dispense with glasses not only for distance vision but even for reading and for intermediate vision. Today attention is directed both to eliminating pre-existing myopia and hyperopia and to treating astigmatism. Lens power calculations have been perfected and refined, and new means of correcting postoperative refractive surprises caused by lens power miscalculations are available.
Multi(tri)focal intraocular lenses allow us to take up the challenge of correcting presbyopia.
The key to obtaining excellent refractive results after cataract surgery is biometry, i.e. accurate measuring of the length of the eye and the curvatures of the cornea, which are incorporated in modern lens power calculation formulae to yield accurate and consistent results. Classical echography (applanation biometry), using a probe in direct contact with the cornea, still gives good results but may induce postoperative refractive surprises if the probe flattens the cornea too much. New methods, such as immersion biometry or non-contact partial coherence optical interferometry (Zeiss IOL Master) provide extremely accurate measurements, are more convenient for the patient and take up less technician time.
The smaller astigmatically neutral incisions we now routinely make enable us to act more accurately during cataract surgery with pre-existing astigmatism. (read more about it).
The next step forward in refractive cataract surgery is the treatment of presbyopia during lens removal. Now that modern cataract surgery has made it possible to obtain for most patients a good distance vision without glasses, the next challenge is to provide them with good reading ability without glasses, thus simulating accommodation (i.e. the ability of the normal crystalline lens to adjust for distance and near vision). This would greatly enhance the quality of life for most patients. A certain independence from reading glasses can be partially created
with monofocal implants where the dominant eye is adjusted for distance vision and where a slight myopia is created in the other eye. This allows the patient - after a period of adjustment - to function without reading glasses in a lot of circumstances. This situation is called Monovision. Depth perception can be slightly altered although only a very slight number of patients experience trouble in driving. In certain cases this monovision can be simulated before surgery by a contactlens test to sort out whether the patient can adapt to the difference between both eyes. This technique is nowadays less applied due to the recent progress of multifocal implant lenses. The surface of these implants has been modified (by diffractive or refractive circles) in order to allow distance and near vision. The accommodation process is simulated (this is the crystalline lens power to adapt for near and distance vision). Dr. Vryghem was the first surgeon in Belgium to place multifocal implants in 1997 (AMO Array). The quality of the first lenses was not optimal: patients complained about halo’s at night and an insufficient near vision. Since 2010 the quality of multifocal implants has improved dramatically especially with the appearance of trifocal implants. Trifocal implants have 3 different focal points and are developed in order to allow a good distance vision, a good near vision (40 cm) and even a good intermediate vision (60-70 cm). The intermediate distance is used for PC work. These implants are an adequate solution for the younger presbyopic patients who work often on PC. These trifocal implants are of Belgian origin. Their design was developed by PhysIOL, a company located in Liège, who has a patent on the implants. Only in a very little number of cases complaints about halo’s round light sources are registered. This progress explains why refractive lens surgery (Refractive Lens Exchange) with trifocal implants is currently the preferred technique to correct presbyopia.
Current advances in surgical technique, biometry and lens power calculation have allowed us to move one step closer to the ideal of achieving emmetropia in all our cataract patients.
In turn, these refinements in postoperative refractive results have increased our ability to use multi(tri)focal lenses and offer this technology to our patients as a means of addressing presbyopia and reducing dependence on spectacles.
Intraocular lens surgery is becoming a common form of refractive surgery not only for our cataract population but also for older people who would prefer to dispense with their spectacles.
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