The Accommodating IOL – the Crystalens HD and Crystalens AO
The Bausch & Lomb Crystalens was the first truly effective accommodating IOL to become available in the world. It is the first and only accommodating IOL to be approved by the United State’s FDA.
Accommodation is the name of the normal, natural change in the focus of the eye from a distance to a near focus that works well for most people until the age when presbyopia sets in at about 40-47 years of age. Presbyopia occurs due to the natural loss of the flexibility of the human lens that happens to all of us with ageing.
The Crystalens relies on the normal, natural mechanism of accommodation of the eye. When you want to look at something close to you the brain sends signals to the ciliary muscle inside the eye causing it to contract. This happens regardless of your age and the ciliary muscle maintains its strength throughout life. The contraction of the ciliary muscle increases the pressure on the jelly-like vitreous of the eye and the vitreous pushes the Crystalens forwards in the eye. The Crystalens is unique in that it has hinges in the supporting part of the lens (haptics) that allow this forwards movement. As the IOL moves forwards it results in the focus of the eye changing onto closer objects.
Unlike the bifocal like effect of a multifocal IOL the Crystalens aims to restore the normal ability to continuously change the focus of the eye. The success of the Crystalens HD and Crystalens AO will depend on how well the lens moves forwards in your eye. In many cases it may not work straight away and the accommodation of the Crystalens is known to improve with time. Some patients require a YAG laser treatment to the capsule of the natural lens at about 3-4 months after surgery before the Crystalens works properly.
Advantages of the Crystalens over the Alcon ReSTOR IOL:
- Fewer problems with halos and ghost images particularly for night driving.
- Quality of distance vision is slightly better as the Crystalens is just like a monofocal IOL for distance vision. The Crystalens delivers 100% of the available light at all distances whereas the multifocal splits the light to focus at two different places at the same time.
- Better unaided intermediate distance vision.
- Gives a continuous range of focus instead of two focal distances.
Disadvantages of the Crystalens compared to the Alcon ReSTOR
- A lower percentage of eyes read the very smallest reading test type – about 50% versus 80%. You may still need glasses to read fine print such as a telephone book.
- There is a complication called the Z-syndrome. This is displacement of the position of the Crystalens in the eye caused by contraction of the capsular bag of the natural lens. The result is that the focus (refraction) of the eye is not perfectly focused for distance any more. It can often be solved by using a YAG laser to make an opening in the capsule of the natural lens. The newer models of Crystalens such as the HD and AO are less likely to suffer from the Z-syndrome than the older models.
- The Crystalens is more expensive. There is an additional surcharge for this lens which includes 6-12 months of follow up, any laser refractive surgery that may be required as well as YAG laser capsulotomy. Basically a cost up front that means I will give you the best result that I can give you without further charge.
Problems common to both multifocal and accommodating IOLs
Post-operative distance refractive error. Although we take all care and use the newest equipment, the latest IOL constants and use all modern IOL formulae to calculate the correct optical power of IOL for your eye there is still a possibility of a focussing error. No eye surgeon can guarantee a perfect refractive outcome (perfect distance focus) with all cataract and IOL implant procedures. Even the world’s most experts at IOL calculations will have 10-20% that have a distance spectacle correction that affects their vision. With the Crystalens I include the cost of excimer laser surgery to correct this should it happen. This is usually done at 3-6 months after cataract surgery.
Rarely, patients are not satisfied with their vision after their chosen intraocular lens implantation. If this occurs, we can help with this using the following options: 1) glasses or contact lenses may need to be prescribed 2) a laser procedure may need to be performed 3) the implant can be removed and replaced it with a different category of implant (this procedure usually takes about 10-20 minutes to complete and can be performed through the initial incision if deemed necessary).
I hope this outlines the option of Crystalens which has helped many patients achieve maximum spectacle independence using modern intraocular surgery and lens technology. Feel free to ask us any further questions or email me at DrCremers@visionaryeyedoctors.com.