REFRACTIVE LENS REPLACEMENT
Behind the coloured ring (or iris) of the eye resides a crystalline lens that is responsible for focusing the incoming light accurately on the retina, in order to permit sharp vision. The situation is not always that ideal, and some need the help of spectacles or contact lenses to permit sharp vision.
People that are nearsighted need spectacles to see in the distance. Farsighted individuals become more dependent on spectacles, especially so for reading, the older they get. Astigmatism on the other hand is caused by the shape of the cornea representing the shape of a rugby ball, where ideally it should be round like a soccer ball. Presbyopia is an age related change that occurs to all of us. The crystalline lens becomes hard and unable to focus on objects at close range.
All four these spectacle errors can be corrected with the implantation of an artificial intra-ocular lens (IOL) during a lens replacement procedure. The crystalline lens is not removed. A small opening is made in the front of the lens through which the hard content is removed and replaced with a new intra-ocular lens. The IOL is placed inside the empty bag left behind, and grows into position within a few weeks.
The intra-ocular lens that is to be implanted is very specific for every eye, and the strength needs to be calculated accurately in order to guarantee success and spectacle independence. Dr. Hartog analyses the results of all his lens replacement surgeries. After thousands of procedures he can optimise the results enabling more accurate predictive results. The results of the treatment of astigmatism is also analysed, whether it be with special toric lenses, or small incisions made with a diamond blade.
GOOD CANDIDATES FOR REFRACTIVE LENS REPLACEMENT
In our forties we start to have difficulty with any near tasks, including reading, and get more and more dependent on spectacles. This happens due to age related changes that occur in the natural lens. The lens in our eyes are responsible for the accurate focusing of light at different distances. This active process is called accommodation. With age our lens hardens and loses its accommodative power, and this is a progressive change that gets worse the older we get.
A refractive lens exchange procedure or lens replacement surgery can accurately resolve this failure and restore vision at all distances, permanently. The procedure is very successful, but the timing is also very important. Initially as the lens hardens, only near vision is affected. The fact that the patient can still see well in the distance without the need for spectacles, means that his natural lens still has a function, and this might not be the optimal time to replace the natural lens with a multifocal lens. The hardening of the lens gets progressively worse though, a process called presbyopia, and soon the patient will also need glasses for driving and watching TV. At this stage the natural lens failed altogether, and replacing it with a multifocal lens can provide spectacle independence.
Patients that had a previous refractive eye surgery, can be ideal candidates for a refractive lens replacement surgery. Previous refractive procedures include LASIK (laser in situ keratomileuses), PRK (photorefractive keratectomy) or RK (radial keratotomy). These patients had good vision without the need for spectacles for many years after the refractive procedure, but with age find that they become completely dependent on spectacles again. It is important to note though that the previous treatment poses unique challenges to both the doctor and patient. Despite this, these patients are often ideal candidates for a refractive lens replacement surgery.
Since the previous laser treatment changed the shape of the cornea, the measurements taken to calculate the ideal lens to be implanted in the eye, is more difficult than usual. The accuracy drops from more than 90% to approximately 75%. The worst case scenario is that the patient might have a small spectacle error after the lens replacement procedure, but this can be accurately treated with a laser surgery if needed, without the risk of any surprises. The healing and visual recovery is also slower in patients that had previous corneal surgery. For this reason Dr. Hartog will wait one month after the first eyes’ lens replacement procedure to confirm the result, before performing the procedure on the second eye.
WHAT TO EXPECT DURING THE EXAMINATION FOR CATARACTS
Dr. Hartog will perform a full examination in order to exclude any coexisting eye conditions that can also negatively affect vision, or have an influence on the planned treatment. Measurements of the eye to calculate the strength of the appropriate lens to be implanted are essential. These measurements will be performed first, before any other examinations are done, in order to assure that the measurements are accurate.
Dr. Hartog will be able to address all the patients questions and give appropriate guidance. Recording and analysing the results of all his lens replacement surgeries, as well as the success of all the types of lenses used, ensures that Dr. Hartog can provide accurate guidance.
WHAT WILL HAPPEN ON THE DAY OF THE PROCEDURE
Dr. Hartog performs his surgery at a specialist eye hospital, the Cape Eye Hospital. The staff are uniquely equipped to assist patients receiving specialist eye treatment, and exceptionally helpful in addressing any concerns. Let's be honest, a hospital and especially a theatre, can be a very intimidating environment, and it helps to have competent staff to assist patients and help keep them comfortable.
The patient can have his breakfast and take his usual medication on the day of the procedure.
Measurements will be performed with the Zeiss IOL master machine. The equipment provides additional information of each eye, that is used during the planning of the procedure. The unique features of each eye is used for digital marking and providing information that is transferred to the operating theatre to guide the surgical plan. The steps of the surgical procedure are guided with an overlay in the microscope. This assists the surgeon in more accurate execution of some steps in the procedure. Very importantly, it assists in the precise positioning of the new intra-ocular lens, especially toric lenses that needs to be inserted in a specific rotation.
For preparation, the staff will insert topical drops into the eye to be treated. The anaesthetist will provide conscious sedation as well as local medication to provide complete anaesthesia of the eye. The patient is positioned in a chair that reclines to become a bed. The patient is awake during the procedure, but the eye is completely anaesthetised and therefore the procedure is completely painless. The patient can communicate freely with Dr. Hartog while the natural lens is replaced with the artificial lens, and therefore any concern or discomfort can be addressed to make sure the patient is comfortable during the procedure that lasts approximately 10 minutes. The eye is covered with a protective shield after the procedure, and the patient receives his medication instructions from the pharmacist. After some refreshments the patient can go home. The procedure itself is painless, and after the procedure the patient also should not experience any pain or discomfort. It might be a bit scratchy as the feeling returns due to dryness though.
HOW IS THE CATARACT SURGERY PERFORMED?
The procedure is performed with a thin blunt needle through a small 2,2 mm opening at the edge of the color of the eye. This opening closes much like a valve, without the need for suturing. The procedure is called a phaco-emulsification. The tip of the needle vibrates very fast to break up the hard cataract into small pieces that can be aspirated through the needle.
The cataract is not removed, a small round opening measuring 5 mm in diameter is made in the front of the lens. Through this opening the hard content is removed by phaco-emulsification, but the capsule is left behind. This capsule acts much like an envelope, with the front open, through which the new intra-ocular lens is implanted. The lens fits accurately inside this capsule without the need for suturing.
THE POST-OPERATIVE CARE
Dr. Hartog sees his patients the day after the procedure in his rooms to remove the eye pad and provide instructions and guidance. The patients’ vision will be a bit hazy for a few days, but clears up very quickly. The use of the topical drops are very important to promote healing.
At the follow-up visit a few days later Dr. Hartog will confirm the improvement in vision and the patients satisfaction, before planning the procedure on the second eye. The lenses grow into their final position within a month and never needs replacing or removal. The vision also stays stable in future, since the lens in plastic and does not change over time. All this means that the result of the procedure is permanent.