By Dr Smita Agarwal (MBBS; FRANZCO)
This CPD course is now available on Specsavers MyCPD Portal.
Cataract is one of the leading causes of preventable blindness in the world. As the number of surgical procedures are increasing every year, patient demands are also becoming more challenging.
Intraocular lenses (IOL) have come a long way since Sir Harold Ridley first implanted an inert acrylic plastic splinter from shattered aircraft canopies in the eyes of pilots during World War II. Although a true visionary, Dr Ridley’s ideas were ridiculed and strongly opposed by the medical fraternity and the idea of lens implantation was abandoned. The first IOL, made from polymethylmethaacrylate (PMMA) was manufactured by Rayner (New York, USA). PMMA lenses were the only lenses available until 1990. These are rigid lenses hence needed a larger incision for implantation. They are the least expensive IOL currently available and still in use in some parts of the world.
The first FDA-approved foldable IOLs were the Allergan (Allergan, Inc; California, USA) silicone lens in 1990. The material was very biocompatible and enjoyed a superb track record of safety and performance. Then in 1995, Alcon (Texas,USA) introduced the first hydrophobic acrylic material lens, AcrySofâ. Later on, acrylic lenses were introduced in hydrophilic/hydrogel material. The biomaterial used for IOLs should ensure excellent long-term uveal biocompatibility, determined by the residual lens epithelial cells within the capsular bag. Different IOL materials have different adhesive properties, where hydrophobic acrylic materials present the highest level of adhesiveness2. While cataract surgeons may have personal preferences, no clear superiority of one foldable material over the other has been demonstrated.
The square edge of the optic is designed to reduce posterior capsular opacification. The size of the IOL and haptic design are also important factors to take in to account for postoperative IOL stability. The toric IOLs with a larger overall diameter have excellent early rotational stability 3 while loop haptics ensure better stability and centration than plate haptics.4
There has been extensive ongoing research to continuously improve the visual performance of intraocular lenses along with decreasing the associated adverse effects. Approximately six million intraocular lenses are implanted annually.
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