April 23, 2021
What are they?
Phakic intraocular lenses (IOLs) are small and thin lenses made of biocompatible material that are implanted inside the eye to correct refractive errors (myopia, hyperopia and/or astigmatism), reducing or eliminating the dependence on glasses or contact lenses. The term phakic refers to the fact that the IOL is implanted without removing the natural lens of the eye - crystalline lens-, which allows to maintain the ability to accommodate.
The great advantage of phakic IOLs over laser techniques on the cornea is that the anatomy of the eye is not permanently changed, and these lenses can be explanted at any time. The lenses do not require any periodic maintenance or replacement, remaining in the eye predictably until the time when cataract surgery is required.
Phakic IOL implantation surgery can be a safe and effective alternative to laser surgery when the latter is contraindicated, either because the refractive errors (number of diopters) are highor becausethere are corneal or pupillary incompatibilities. A careful preoperative evaluation should be performed to determine whether the necessary safety conditions for IOL implantation exist, including evaluation of the corneal endothelium and measurement of the anterior chamber depth.
Preparation & Technique
Phakic IOL implantation surgery is performed in an outpatient setting, under topical anesthesia (drops), sedation or general anesthesia, according to the preferences of the patient and/or surgeon, and factors such as the type of IOL to implant, the need for suture (stitches) or whether it is a unilateral or bilateral surgery. It is a quick (about 20 minutes per eye) but very delicate surgical procedure, which requires a microscope in order to ensure the implantation of the IOL in a precise manner and with minimal trauma to the ocular structures. The surgery consists of introducing an IOL inside the eye through a small opening made at the base of the cornea. The most recent IOLs, made of a very flexible material, enter the eye folded and unfold inside, which allows them to enter through increasingly smaller and self-sealing openings, which do not require sutures to close. Depending on the type of IOL used, it can be placed in front (anterior chamber) or behind (posterior chamber) the iris, but always in front of the lens.
Recovery
The patient can return home after waiting some time after surgery and, depending on the surgeon's preference, can leave with the eye covered with a dressing and/or an eye protection, in order to avoid any trauma to the operated eye. There may be some discomfort/light pain, foreign body sensation and photosensitivity in the first postoperative days, but the prescribed medication associated to relative rest (avoiding intense physical activity and lifting weights) and the use of glasses with UV protection will allow a significant and fast relief of these symptoms.
Most patients experience a very significant improvement in their vision immediately after surgery, which evolves favourably over the first week, but full recovery will only occur about 1 to 2 months later in the case of flexible lenses without sutures, or about 6 months in the case of rigid lenses that require progressive removal of stitches. In either case, the best corrected vision that can be achieved after IOL implantation is almost always equal or superior to that obtained with spectacles or contact lenses before surgery, and with great visual quality.
In some cases, the refractive error may not be completely corrected solely with the implantation of phakic IOLs and the use of glasses or contact lenses may be necessary after surgery. If possible, laser surgery can be performed at a second surgical time in order to eliminate any small residual refractive error.
Complications
The greatest risk associated with phakic IOL implantation surgery derives from the fact that the eye is opened to allow for the insertion of the IOL and consists of intraocular infection (endophthalmitis), an extremely rare situation. Other possible complications include adverse reactions of the ocular structures to the implant, such as the development of cataracts, loss of corneal endothelial cells and/or iris inflammation. In these cases it may be necessary to permanently explant the IOLs or to replace them with IOLs made of a different material. There is also the possibility of phakic IOLs moving out of their correct position after implantation and needing to be repositioned. It is important to note that with the progressive improvement of lens quality and with the correct selection of patients, these complications are less and less frequent.
After total recovery from the surgery, it will be necessary for the ophthalmologist to observe the patient annually, in order to evaluate the stability of the IOL and the evolution of the number and shape of the corneal endothelial cells over time.
By Dr Ramiro Salgado,Dr Miguel Gomes, Dr Nuno F. Alves, Dr Teresa Pacheco, Dr Tiago Ferreira
