Phakic IOLs are a type of intraocular lens that is used to help your eye attain the proper focus. Unlike the lenses used in cataract surgery, which are sometimes called aphakic IOLs, these lenses do not replace your eye’s natural crystalline lens. Instead, they are helper lenses, sometimes described as “implantable contact lenses.”
Phakic IOLs have been approved for the treatment of myopia by the US Food and Drug Administration (FDA) since 2003. However, they have not been approved for the treatment of hyperopia. According to industry representatives, studies of phakic IOLs for treatment of hyperopia are ongoing, but will they ever be approved?
Concerns with Phakic IOLs for Hyperopia
There are two significant concerns that have delayed the approval of phakic IOLs for hyperopia. Both relate to the narrow anterior chamber of hyperopes, the part of the eye between the iris and the cornea, where some phakic IOLs are placed. First, there is concern that the IOL will abrade the endothelium, the innermost layer of the cornea, which could result in a condition similar to Fuchs’ Dystrophy. Second, there is concern that implantation of a phakic IOL in an already crowded anterior chamber could increase the risk of closed angle, or acute glaucoma.
Both of these risks are likely very rare, but because of the seriousness of the conditions, even a small risk merits significant study before approval.
Some Study Results
In the early clinical trials, phakic IOLs were being studied equally for both myopia and hyperopia. It was concluded that phakic IOLs should only be placed in the posterior chamber, behind the iris. These early studies confirmed that risks associated with phakic IOLs were small, but also showed that the results were not highly predictable.
However, a recent Italian study of 59 eyes with posterior chamber placement of phakic IOLs showed significant results. The study looked at the patients’ results at several points up to ten years after implantation. It showed that people received the phakic IOLs achieved, on average, a spherical equivalent of +0.07 diopters, essentially 20/20, though one eye did lose one line of best corrected visual acuity. Visual acuity was stable over the ten-year period. Endothelial loss was slight, and did not increase. Intraocular pressure increased by about 5.3%, and there was one incident of closed angle glaucoma.
Overall, though, this more recent study suggests that the path should be clear for approval of phakic IOLs.
The main barrier to approval of phakic IOLs for hyperopia is likely market-based. In addition to potentially increasing risks, the narrow anterior chamber of hyperopes makes implantation of the IOLs more difficult for surgeons. This makes them less popular among surgeons. With other treatment options like LASIK and PRK available, surgeons do not seem to be crowing for phakic IOLs for hyperopia treatment. With no extant market, it seems unlikely that companies will be making the big push for approval of phakic IOLs for hyperopia any time soon.
If you want to learn more about phakic IOLs or other types of refractive eye surgery, please contact a local eye doctor today.