Aphakic intraocular lens (Aphakic IOL) is a type of lens secondarily implanted in aphakic eyes (whose natural lens was extracted) or eyes that lack capsular support. Aphakic patients have typically undergone cataract surgery years before or experienced intraocular lens complications like dislocation of the IOL. Aphakic IOL differs from a phakic IOL, which is implanted into a patient's eye with an intact natural crystalline lens.
Aphakia without capsular support is treated with an IOL that is clipped on the iris. The iris-claw IOL technique was first described in 1972 by Jan Worst when he implanted it into the anterior chamber and clipped the lens to the anterior surface of the iris. The technique has proven to be effective and safe and comes with a certain edge over the iris-sutured and scleral haptic-fixated IOLs. The iris-claw technique is faster to perform and avoids direct angle compromise. However, this technique may lead to loss of endothelial cells, especially in a narrow anterior chamber. Surgeons now implant the lens in retropupillary fixation and clip it to the iris' posterior surface to avoid endothelial cell loss.
Patients who cannot undergo the traditional lens implantation like children can benefit from the Artisan aphakia lens because it is fixed to the iris. The children would have had to wear intolerable hard contact lenses or glasses that are cosmetically unappealing. Artisan aphakia lenses are typically implanted in children aged between eight and eighteen, although younger children as young as two years old can have the implants. The lens is designed to be adapted to the child’s growth process as s/he ages. The Artisan iris-claw technique does not involve any sutures, and surgeons can implant them in phakic as well as aphakic eyes.
Aphakic IOLs are made from different materials such as polymethylmethacrylate (PMMA) and available in different refractive powers.
Patients with the following conditions should not have aphakic lens implantation:
- Eyes affected by trauma
- Previous retinal detachment
- Abnormalities involving the iris, pupil, or cornea
- Previous anterior or posterior segment inflammation
- Complications like glaucoma and retinal abnormalities arising postoperatively
Aphakic intraocular lens comes in certain designs which may include:
- Iris-clipped IOLs
- Iris-sutured IOLs
- Scleral-haptic fixated IOLs
- Open-loop anterior chamber IOLs (AC-IOL)
- Angle-supported IOLs or iris-fixated anterior IOLs
- Tran-sclerally sutured IOLs or posterior chamber IOLs
Before the Procedure
The aphakic IOL will be prepared ahead of the procedure. For instance, decentration is measured on slit-lamp photographs using specific software.
The patient will undergo a complete ophthalmic examination which may include:
- Slit-lamp photography
- Slit-lamp biomicroscopy
- Best-corrected visual acuity (BCVA)
- Wavefront analysis of ocular and internal higher-order aberration
Different techniques are used to implant the various types of aphakic IOLs. Aphakic IOL implantation is done under local or general anesthesia. For instance, in the procedure involving an Artisan IOL, the surgeon:
- Makes a scleral tunnel incision posterior to the limbus
- Performs paracentesis (2) to remove the vitreous from the anterior chamber
- Injects acetylcholine to constrict the pupil
- Uses a viscosurgical instrument to fill the anterior chamber
- Inserts an aphakic IOL into the anterior chamber. S/he rotates the IOL using a hook until the IOL has taken an appropriate position. The surgeon aims to centre the IOL over the pupil perfectly
- Performs peripheral iridotomy and removes viscoelastic material
- Closes the incision using three uninterrupted nylon sutures
Risks & Complications
Different aphakic IOLs come with various risks and complications. Generally, the procedure has reported low intraoperative and postoperative complications rates.
The anterior chamber IOL (ACIOL) presents a challenge because angle measurements are not the same for every patient. This variation in angle-to-angle dimensions can result in glaucoma (new-onset or worsening), corneal decompensation, and chronic inflammation. Besides, the surgeon needs to make a large incision to implant the ACIOL. Further, angle supported IOLs have recorded high incidences of endothelial cell loss.
It is technically challenging to insert scleral-sutured IOLs. The risks include endophthalmitis, intraocular hemorrhage, IOL tilt, and suture breakage resulting from the use of scleral needle passes. Trans-sclerally sutured posterior chamber IOLs have been associated with longer surgical time. They also have more complications, intraoperatively and postoperatively. Postoperative complications include decentration, lens tilt, retinal detachment, suture erosion, and vitreous hemorrhage.
Iris fixation is also technically challenging because the incision is made through the limbus. It can result in the haptic slipping through the suture knot and suture breakage. Iris clip designs are also associated with dislocation, cystoid macular edema, and iritis.
Aftercare & Recovery
The patient is prescribed antibiotics to prevent infection, steroids to help with inflammation, and anti-inflammatory medications to address any pain or inflammation. Patients are followed up for up to five years, depending on the type of lens.
Studies have shown that aphakic IOLs are an effective and safe procedure for implantation in eyes lacking capsular support.