Implantable contact lens
Current status of phakic intra-ocular lenses
The implantation of intra-ocular lenses at the time of surgery for cataracts in either elderly or young patients has been a standard eye microsurgical procedure for more than thirty years. The excellent results obtained, the long term stability and lack of complications have demonstrated that intra-ocular lenses are safe in patients who have had their natural crystalline lens removed.
These observations resulted in surgeons developing a variety of phakic intra-ocular lenses, that is, lenses inserted into the eye in patients who have a normal crystalline lens to correct extreme refractive errors; both high myopia and high hypermetropia. In 1987 the Russian Ophthalmologist, Dr. Fyodorov, who pioneered radial keratotomy for myopia started placing silicone intra-ocular lenses in the eye on the surface of the eye's natural crystalline lens. While this corrected refractive errors very well, the material was found not to be suitable in that location and so was abandoned.
In 1992 Dr. Fechner in Germany modified this lens and while initial results were extremely good, after one and a half years a small number of patients started developing some early opacification of the natural crystalline lens. These observations resulted in two conclusions:-
- That the silicone material was not suitable in this location for these patients.
- That the intraocular lens touching the natural crystalline lens was a second reason for the observation of early cataract.
 With these two
observations the Argentinian Ophthalmologist, Dr. Roberto Zaldivar
developed a phakic intraocular lens
which became termed the "Implantable Contact Lens"
by the company which had assumed the patent rights to the lens,
STAAR surgical.
The advantages to this particular lens were the following:
The material was completely different and was found to be highly bio-compatible, permeable to metabolites and the lens was designed to respect the space between the natural crystallinelens of the eye and the phakic intraocular lens which was inserted. The lens material is called a collomer and is made of porcine collagen and hema. The advantages found with this particular lens were the following:-
- The lens is able to be folded upon itself and this enables it to be inserted through an extremely small 3 mm incision which is self sealing. This also meant that it could be removed through the same incision if necessary.
- The advantages over other refractive procedures such as LASIK for the high corrections were found to be the following:-
- The quality of the optical results was far superior when the lens was placed in the eye in this location compared to flattening or steepening the cornea excessively for these extreme refractive errors. The potential complication of LASIK in these high errors being optical aberrations, haloes and a degraded optical quality were absent with the Implantable Contact Lens.
- In addition, the power calculations for the intraocular lens were found to be much more predictable than refractive techniques involving the cornea such as LASIK. Also 98% of patients in initial studies were found to have their vision improved more than one line on the vision chart and many improving more than this. (Compared with their previous best corrected spectacle vision). Thus the ICL can provide better uncorrected vision post-operatively than the patient's best corrected acuity pre-operatively. This is virtually unheard of in LASIK for high refractive errors.
- There were no complications with the surgery, no-one's vision worsened. The visual result was found to be very predictable in correcting high levels and extreme levels of myopia and hypermetropia.
Finally Dr. Zaldivar developed a technique he coined bioptics in which both the Implantable Contact Lens and LASIK were undertaken in the one eye for patients who had such large refractive errors that the implantable contact lens on its own was unable to correct them. In these patients he found that the quality of vision post-operatively was extremely high. The visual recovery was virtually immediate. There was an absence of glare and haloes at night time. The result was both stable and predictable and 80% of patients in this extreme group had a gain in their best corrected vision of more than one line with the remaining 20% having no change in their best corrected vision, but with no patients worsening.
The STAAR Implantable Contact Lens has been available since 1992 and has been modified over the years in both power and design up to its current model in Australia. Its safety and effectiveness has already been demonstrated in both Europe and South America.
The procedure is usually performed in a Day Surgery or Hospital using local anaesthetic. The lens as mentioned is inserted through a 3 mm opening in the cornea, the opening being self sealing and not requiring stitches to close. Drops are used for several weeks afterwards. Visual improvement often occurs within hours to a day. Normal activities can be returned to almost immediately and there is minimal discomfort.
Currently, the Implantable Contact Lens is awaiting approval from the Federal Government Therapeutic Goods Administration for use in specialized eye Centres such as the Australian Institute of Eye Surgery.
The surgeons at the Australian Institute of Eye Surgery believe the patients to gain most from the Implantable Contact Lens will be those with high shortsightedness beyond 10 dioptres and longsightedness beyond 5 dioptres and patients whose refractive errors currently approach the upper limit of what is considered to be suitable for LASIK.
Some patients with extreme shortsightedness or longsightedness may benefit from a combined procedure involving the Implantable Contact Lens followed by LASIK.
 Book a consultation online
 |
|
