Cataract
Surgical treatment
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| Dr McKellar operating on a patient with cataract. |
The only treatment for cataract is surgery.
Overview
This section deals with the more technical aspects of cataract surgery. More information on what it is like to go through the process of cataract surgery can be found in Having cataract surgery
The decision to operate
Many issues must be considered before the decision to operate is made. These include:
- The visual problems experienced
- Determining that cataract is present
- An assessment of whether other eye disease is present and how this will impact on the expected outcome
- A review of the risks of surgery
Preparation for surgery
Preparing for surgery involves two important processes:
- Measurements of the eye, known as biometry
- Completion of all paperwork including hospital admission forms and consent documents
Biometry
Measurement of the eye is a critical part of cataract surgery. The curvature of the cornea and length of the eye are determined with instruments known as a keratometer and A-scan ultrasound respectively. The data is then entered in formulae that calculate the power of the intraocular lens required for each individual patient.
Admission forms and consent documents
There are certain legal requirements that must be completed prior to surgery. These include the hospital medical questionnaire and the consent for surgery.
The surgical process
Cataract surgery involves five main steps:
- Dilating the pupil
- Anaesthetising the eye
- Removing the cataract
- Implanting the new intraocular lens
- Recovery
Pupil dilation
Cataracts lie behind the pupil and so it must be dilated prior to surgery.
Eye anaesthesia
Anaesthesia for eye surgery has changed significantly over the last decade. It is very rare for people to require general anaesthesia. Most patients now have one of two types of anaesthesia:
- Topical anaesthesia
- Sub-tenons local anaesthesia
Topical anaesthesia
Dr McKellar prefers to use topical anaesthesia using special eyedrops to 'numb' the eye. This avoids needles and results in more rapid and comfortable recovery.
Sub-tenons anesthesia
Patients who are very sensitive to light or touch around their eye may require sub-tenons anaesthesia, in which a soft canula (or tube) distributes anaesthetic around the eye through a tiny opening in the conjunctiva.
Removing the cataract
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| The concept of cataract removal. Courtesy Alcon. |
Cataract surgery involves removal of the cloudy natural lens of the eye and the placement of a new clear artificial intraocular lens inside the eye to restore vision.
The easiest way to understand cataract surgery is to compare it to the process of removing the contents of an egg from an eggshell. The diagram to the right shows the cloudy lens exiting the eye.
The analogy of shelling out an egg is helpful but now no longer entirely accurate. Most cataracts are removed by small incision surgery in which the lens is broken up inside the eye and then aspirated through a tiny opening.
There are two ways to break up the lens:
- Phacoemulsification, the standard technique
- AquaLase®, a new water-jet technology, pioneered in New Zealand by Dr McKellar
Phacoemulsification
The reality of cataract surgery. Small incision phacoemulsification or AquaLase®. Courtesy Alcon.
Phacoemulsification is an ultrasound technology in which a vibrating hollow tube breaks up the cataract.
Phacoemulsification is the most common method used to remove cataracts and is the most effective method of removing hard cataracts. Dr McKellar uses this technique in about 90% of all patients.
AquaLase®
AquaLase® is an alternative technology to phacoemulsification. It uses pulses of water to fragment and wash away the lens.
Dr McKellar uses AquaLase® to remove cataract in approximately 10% of patients; predominantly in younger patients and those with early cataract. It is a very gentle way to remove softer cataracts.
Intraocular lens implantation
Following removal of the natural lens a new 'plastic' lens is inserted into the eye to restore vision. The power of this intraocular lens is calculated for each patient before surgery.
Acrysof® intraocular lenses
Dr McKellar primarily uses the Acrysof® intraocular lens, the most commonly used lens world-wide. All Acrysof® lenses have a yellow tint to reduce ultraviolet damage to the eye.
Depending on a patient's eye and the desired outcome one of three types of lens will be implanted:
- Acrysof® IQ lens
- Acrysof® TT lens
- Acrysof® Restor® lens
Acrysof® IQ lenses
This is a monofocal, or single focus, lens used to correct the vision of patients with minimal astigmatism.
When a monofocal lens is implanted most patients will be able to drive without glasses. Spectacles will be required for near vision.
Monofocal lenses are the least expensive IOLs.
Acrysof® TT lenses
Patients with significant astigmatism benefit from the implantation of a toric lens such as the Acrysof® TT lens.
When a toric IOL is implanted most patients will be able to drive without glasses. Spectacles will be required for near vision.
Toric lenses are more expensive than a single focus lens.
Acrysof® Restor® lenses
Detail of the Acrysof® Restor® IOL. Circular zones focus light for both distant and near objects. Note: IOLs are transparent, colour has been added to aid visualiation. Courtesy Alcon.
Patients usually require reading glasses after successful cataract surgery.
The Restor® lens is a multifocal IOL that provides good vision at both distance and near. This is achieved by circular zones on the front of the lens which bring light to two separate focal points.
Most patients no longer require distance or reading glasses after surgery.
The Restor® lens is not suitable for all patients and is more expensive than a monofocal lens.
Success rates
In general the chances of successful surgery are approximately 98%. Other eye disease and complications can limit the outcome.
Risks of cataract surgery
Modern cataract surgery is very safe with approximately 98% of all patients having successful outcomes and no complications. Nevertheless no surgical procedure is risk free. The most serious risks of surgery include:
- Infection
- Bleeding
- Retinal swelling
- Retinal detachment
Most complications can be successfully treated but in rare cases vision loss and even blindness can occur. In very rare cases inflammation can damage the unoperated eye.
Further information
Dr McKellar gives all of his patients a brochure produced by The Royal Australian and New Zealand College of Ophthalmologists which further outlines the process, benefits and risks of surgery. Even this brochure does not contain all the information you may need before deciding to have cataract surgery. Please ask Dr McKellar if you have any other questions.