Materials Used For Intraocular Lenses
| This section requires expansion with: reorganization, clarifications, better differentiation between the practices of different countries, and specific differences between PMMA, silicone, and silicone acrylate. |
Polymethylmethacrylate (PMMA) was the first material to be used successfully in intraocular lenses. British ophthalmologist Sir Harold Ridley observed that Royal Air Force pilots who sustained eye injuries during World War II involving PMMA windshield material did not show any rejection or foreign body reaction. Deducing that the transparent material was inert and useful for implantation in the eye, Ridley designed and implanted the first intraocular lens in a human eye.
Advances in technology have brought about the use of silicone and acrylic, both of which are soft foldable inert materials. This allows the lens to be folded and inserted into the eye through a smaller incision, which make them a better choice in people who have a history of uveitis, have diabetic retinopathy requiring vitrectomy with replacement by silicone oil or are at high risk of retinal detachment.
In the United States, a new category of intraocular lenses was opened with the approval by the Food and Drug Administration in 2003 of multifocal and accommodating lenses. These come at an additional cost to the recipient beyond what Medicare will pay and each has advantages and disadvantages.
New FDA-approved multifocal intraocular lens implants allow most post operative cataract patients the advantage of glass-free vision. These new multifocal lenses are not a covered expense under most insurance plans (In the United States, Medicare decided to stop covering them in May 2005) and can cost the patient upwards of $2800 per eye. Latest advances include IOLs with square-edge design, non-glare edge design and yellow dye added to the IOL.
The trade marked "Natural Yellow" this material is relatively new to the market and available in three hydrophilic IOL materials. Dr. Patrick H. Benz of Benz Research and Development created the first IOL material to incorporate the same UV-A blocking and violet light filtering chromophore that is in the human crystalline lens. This break through material provides the exact chromophore the human retina has already specified for light protection.
Multifocal IOLs – provide for simultaneous viewing of both distance vision and near vision. Some patients report glare and halos at night time with these lenses.
Accommodating IOLs – allow for both distance vision and midrange near vision. These IOLs are typically not as strong for closer vision as the multifocal IOLs.
To incorporate the strengths of each type of IOL, some eye surgeons recommend using a multifocal IOL in one eye to emphasize close reading vision and an accommodating IOL in the other eye for further midrange vision. This is called "mix and match." Distance vision is not compromised with this approach, while near vision is optimized.
Other IOLs include:
- Blue Light Filtering IOLs filter the UV and high-energy blue light present in natural and artificial light, both of which can cause vision problems; however too much filtering of blue light can increase depression, especially in the winter months (SAD).
- Toric IOLs (1998) correct astigmatic vision.
Read more about this topic: Intraocular Lens
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