Surgery for cataract is now day stay surgery which is almost exclusively performed under local anaesthesia. Although it is always concerning to be having something done to one’s eyes, modern techniques and anaesthesia have made cataract surgery very safe and comfortable. The Milford Eye Clinic has operating theatres on site in our Shakespeare Road facility, and staff who have in some cases been assisting us with eye surgery for nearly twenty years.
It is not necessary for patients to be referred to the clinic for surgery or any other issue, but for cataract surgery it is helpful for us to have information from optometrists briefly outlining your history and providing information about previous spectacle correction.
These appointments can be undertaken at any of our three branches. Your surgeon will examine the eyes to ensure that cataract surgery is the appropriate intervention and perform any other tests to check the condition of the optic nerve and the retina as indicated. Explanations and other written information about the operation is provided, and measurements of the dimensions and optical surfaces of the eyes are performed. These measurements do not involve contact with the eyes and are not uncomfortable. We will also advise you of the expected costs associated with surgery.
Please do not use any makeup on your face or eyelids on the day of surgery. You will be asked to arrive about an hour before the scheduled time for your operation. This gives time for the necessary clerical details to be dealt with and for preoperative eye drops to be instilled to dilate the pupil. You may also be given a light oral sedative. Great care is taken in all operating theatres to ensure that the right operation is done to the right person, so bear with us if we appear to be overly pedantic about this aspect.
When you come into the operating theatre area the eye to be operated on is confirmed with a small mark on the forehead and anaesthetic drops or gel are applied to numb the eye and eyelids. The anaesthetist will insert a small intravenous cannula into a vein of the hand or forearm. It is helpful to many people to be given some additional sedation intravenously, and we monitor the heart rhythm and blood pressure during surgery. The anaesthetist will discuss your requirements with you. Do not hesitate to raise any concerns with the staff.
Your surgeon may arrange for local anaesthetic to be introduced around the outer wall of the eye. To do this a small device is used to hold the eyes open and the local anaesthetic introduced via a small opening in the conjunctiva.
During the operation you will be aware of unusual almost musical sounds from the ultrasonic machine (called a “phacoemulsifier”) which is used to fragment the tissue in your cataract and remove it from the eye. People often are aware of pressure sensations around the eyelids but usually not pain. The time taken to perform surgery does vary considerably depending on the condition of the cataract and other factors in the eyes. Straightforward operations will often be completed in only 10 or 15 minutes, but more complex procedures take longer. If you were to experience discomfort during the operation additional anaesthetic and sedation can be used.
When your operation is completed you will moved into the recovery area and be offered a comfortable chair and light refreshments. It is not usually necessary to remain in recovery for long periods of time. The nurses will ensure that you are comfortable and contact your family or friends to arrange for you to be picked up from the building. It is a legal requirement that you do not drive after receiving sedation, and we recommend that you arrange transport on both the day of and the day after surgery.
Postoperative Clinic visits
We arrange post-operative visits the day after the operation and again 3 or 4 weeks after the operation. At these visits we check the pressure in the eye and at the second visit evaluate the optical outcome. You should expect to visit your optometrist after the second visit to organise adjustment of your glasses as required.
Improvements in modern cataract surgery have resulted in major improvements in visual outcomes and have also reduced the complication rates to extremely low levels. Over 95% of operations are free of complications and produce satisfactory visual outcomes. Only a tiny proportion of surgeries will be complicated by problems bad enough to require additional operations or to result in impaired vision after surgery. Sadly, in medicine adverse outcomes do occasionally occur and in extremely rare instances people can lose vision from eyes.
The devices we use to calculate the lens implants required for cataract surgery are very accurate and allow us to choose the optical outcome for your surgery. The four common scenarios targeted are;
1) Distance Vision; Both eyes adjusted to give distance vision. This provides the best distance vision but does require the use of reading glasses for near vision tasks. The majority of patients chose this option.
2) Near Vision; Both eyes focused at reading distance. Typically this option is only chosen by people who have been short-sighted previously and wish to continue to be able to read without glasses after surgery. Distance glasses will be required for driving and television distances.
3) “Mono-vision”; One eye (usually the “dominant” eye) sees distance and the other is focussed at reading distances. Generally this is only offered to people who have previous experienced it through the use of contact lenses or because of an inherent asymmetry in their vision.
4) “Blended Vision” This is a variation on mono-vision in which the non-dominant eye is left slightly short-sighted to improve the depth of focus, but not as much as in mono-vision. It is the second most commonly chosen option and allows people to perform some, but not usually all, near vision tasks without glasses. Typically one can use a computer without glasses and read newspaper sized print but generally there will be a need for prescription reading glasses for finer tasks. This option is helpful to reduce ones dependence on glasses but does tend to have some effect on the quality of the distance vision and some people will feel that their depth perception is affected – but this is usually temporary.
Toric Implants for Astigmatism
Most of us have some degree of “astigmatism”. This is the term we use when an optical surface is not of equal curvature – think of the surface of a rugby ball or a doughnut as compared to that of a sphere. Approximately 20% of people have enough astigmatism to warrant the use of a special lens called a “toric” lens. You will be advised if we believe you would benefit from the use of a toric lens. Surgery using a toric lens is not significantly different from that using a standard implant. The surgeon has to position the implant at a certain angle in the eye, as opposed to a spherical lens implant which can be placed at any angle. Unfortunately, there is additional cost when a toric lens is used as they are more expensive than standard implants. The other issue is that in approximately 2 percent of cases we find at the first postoperative visit that the lens has rotated within the eye. If this occurs a small adjustment is needed which is performed at our cost. If a toric lens is not used it is still possible to correct astigmatism with spectacles following surgery, but these lenses do improve the quality of the eyesight without glasses – often to a very significant degree.
Multifocal Lens Implants
The goal of a multifocal IOL is to provide functional vision at different focal distances and minimise dependence on glasses. These implants are designed using optical principles combining diffraction and refraction to reduce chromatic aberration and create multiple foci, providing both distance and near focus at all times. The brain will learn to automatically select the focus that is appropriate for the task at hand. Cleverly designed surfaces result in ‘apodization’ of the image which reduce the impact of the optical phenomena associated with diffraction, but patients are usually still aware of the presence of halos around light sources, particularly when driving at night.
A limited proportion of the light (about 20%) is directed to the near focus, so, although multifocal users may be able to read unaided, many will still prefer to use reading glasses. Because of the limited amount of light at the near focus multifocal IOL’s are not an appropriate option for people with macular problems like age related macular degeneration, and generally speaking previously shortsighted people are not well advised to choose these lenses.
Patients must be aware of the sacrifice they are likely to experience with night glare and loss of contrast, which can be perceived as reduced quality of vision, but properly selected patients consider these sacrifices well worth the gain in uncorrected near vision. The most successful cases will be patients who perceive uncorrected reading vision to be a necessity.
“Laser” cataract surgery
A device called a Femtosecond laser can be used to perform some steps of cataract surgery. It is costly, increasing the price of surgery by approximately 25% and has not been proven to produce superior results compared to conventional manual surgery. Meta analysis of thousands of cases has indicated increased rates of significant surgical complications when this machine is used compared to manual surgery.