Your eyes are unique and different from everyone else’s. To get the best results from cataract surgery it should be customised for you.
This article explains how I achieve the maximum quality of vision and freedom from glasses for my patients using the most advanced diagnostic techniques and lens implants.
During cataract surgery the natural lens of the eye, now cloudy with cataract, is removed. The natural lens is one of the two focusing elements of the eye, the other being the cornea. Replacing the cloudy natural lens with a transparent lens implant provides a perfect opportunity to improve the optical performance of the eye. Imperfections existing before the development of cataract may be treated using customised lens implants whose characteristics match those of the eye. Such imperfections include short sight, long sight, astigmatism and presbyopia (reading glasses dependence). These imperfections increase dependence on distance and reading glasses and reduce quality of vision, for example causing glare when driving at night.
A standard IOL does not correct astigmatism (left). A customized (toric) IOL corrects astigmatism and the patient sees clearly without glasses (right)
This patient has received a standard IOL and cannot read the soup can or recipe book without glasses
A customised (multifocal) IOL has been used. Close objects are seen without glasses
This patient has received a standard IOL and has glare and haloes from headlights at night
A customized (aspheric) IOL provides glare-free driving
Lens implants (also called intraocular lenses or ‘IOLs’) are a prosthesis, in this case a transparent plastic lens usually about 6mm in diameter. They are inserted during cataract surgery to replace the focusing power of the natural lens of the eye that has been removed.
The first ever lens implant was made by Rayner in the UK in 1949. It was designed by Sir Harold Ridley FRS FRCS a Consultant Ophthalmologist at St. Thomas’ Hospital London who also performed the surgery. Since then tens of millions of lens implants have been implanted internationally.
Rayner multifocal IOL (left); Rayner monofocal toric (center); Rayner multifocal toric IOL (right)
Lens implant technology is one of the greatest advances made by modern medicine, freeing cataract patients from the ’pebble-dash’ glasses worn previously that offered very poor optical performance and were unsightly.
Thousands of lens implant types are now available and standards have improved greatly over the years. Nevertheless lens implant quality varies greatly, from basic to extremely sophisticated. The most highly customised are made-to-order specifically for individual patients.
The Teleon MPlus multifocal is designed for complete spectacle independence and minimum glare during night driving. The astigmatism-correcting (toric) version is made-to-order, manufacture taking 4 weeks
The Alcon Acrysof family of yellow IOLs. Toric aspheric (left); monofocal aspheric (middle); ReStor multifocal aspheric (right)
Magnified view of a multifocal IOL showing the complex surface that corrects presbyopia
The most sophisticated lens implants combine characteristics to correct all optical imperfections if necessary.
|Lens Implant Characteristic||Optical Imperfection Corrected|
|Power – spherical||Short and long sight|
|Power – cylindrical||Astigmatism|
|Power – asphericity||Wavefront abnormality|
I am committed to maximising the quality of your vision and minimising your need for glasses postoperatively.
This is achieved by –
Step 1) Pre-operative measurements
In-depth analysis of your eyes is performed, many of the tests requiring ultra-sophisticated equipment. Your glasses prescription is determined by an optometrist (optician). Axial length is the front-to-back length of your eyes, measured with the IOL Master, a sophisticated laser.
The curvature of the cornea is assessed with a keratometer. Extremely accurate measurements of cornea curvature, the cornea’s wavefront abnormalities and the diameter of the pupil are made with the Galilei topographer, a high-tech ‘Scheimpflug’ camera system.
The total wavefront abnormalities of the eye, not only those arising from the cornea, are analysed by the iTrace aberrometer a unique device that uses ray tracing technology to reveal ‘high order aberrations’, minute imperfections in focusing as unique to every eye as a fingerprint.
Step 2) Pre-operative consultation
After the measurements, I will examine your eyes and ascertain your visual requirements, for example the extent to which you wish to be less dependent on glasses. There will then be plenty of time to discuss which lens implant is best for you.
Examples of lens implants customised for my patients’ eyes:
Step 3) Surgery
Some lens implants, for example astigmatism-correcting, require highly accurate alignment within the eye if they are to work properly. I use a method of registering the shape of the cornea before the operation begins to achieve this.
Step 4) Post-operative consultation
I will examine you and repeat many of the measurements made prior to surgery, to determine the accuracy of the outcome. I will also ask what you think of your new eyesight!
You may be interested to learn that the standard approach is restricted to a simplified method of performing keratometry. During surgery a standard lens, not designed to fully optimise vision, is implanted. This will not provide a solution customised for your needs.