Welcome back to Interventional Mindset. In this episode, internationally renowned expert in refractive, cornea, and cataract surgery, Eric Donnenfeld, MD, sits down with William F. Wiley, MD, a pioneer in refractive cataract surgery who practices at Cleveland Eye Clinic.
The pair discuss the history of phakic intraocular lenses (IOLs), walk through how to implant phakic IOLs, and provide pearls for sizing implantable collamer lenses (ICLs).
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What is a phakic IOL?
Phakic IOLs are implantable lenses that are surgically inserted behind the iris and in front of the natural lens or in front of the iris; however, unlike in refractive lens exchange (RLE) and cataract surgery, the patient’s natural lens remains inside the eye, allowing natural accommodation.1
Implantable phakic IOLs can be categorized into anterior chamber IOLs (ACIOLs), which are further subdivided into angle-supported ACIOLs and iris-claw ACIOLs, and then posterior chamber sulcus-supported IOLs (PCIOLs). They are generally used for patients with higher degrees of myopic refractive error or when corneal refractive surgery is contraindicated.
Phakic IOLs are unique because they are an additive technology, noted Dr. Donnenfeld, whereas laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and cataract surgery would be considered subtractive procedures because they remove tissue from the eye.
Developments in phakic IOL technology
The only Food and Drug Administration (FDA)-approved phakic IOLs in the United States are the iris-claw ACIOL Verisyse (Ophtec) and the PCIOL Visian ICL (STAAR Surgical).1 Of note, these lenses are only available in the United States for the treatment of myopia and have toric versions available. Both the Visian and Verisyse are approved only for the correction of myopia with or without astigmatism up to 2.5D.
In 2018, a toric version of the Visian ICL was approved by the FDA, and in March 2022 the Evolution (EVO/EVO+) version of the spherical and toric Visian ICL was approved.1 Notably, the EVO ICL has a 360-micron diameter central port that aids the physiologic flow of aqueous humor—eliminating the need for peripheral iridotomies before the lens is implanted.
As the natural lens remains in the eye for accommodation, implanting phakic IOLs is relatively non-invasive, remarked Dr. Wiley. This allows for unique perks, such as the IOL being removable and the cornea not being altered, meaning there are fewer concerns of post-operative dry eye and patients have more options in the future for refractive surgery procedures.
Overview of the history of phakic IOLs
While phakic IOLs have existed for many years, they hadn’t gained much traction until recently due to major innovations in the technology (i.e., the EVO/EVO+ ICL). Dr. Donnenfeld recounted that he first performed phakic IOL implantation 20 years ago with a lens invented by Jan Worst, MD, a famous cataract surgeon from the Netherlands.
This technology was brought to the United States and was initially called the Worst IOL; eventually, this lens was rebranded (for obvious reasons) as the Artisan aphakia lens (Ophtec BV). Dr. Donnenfeld remarked that this lens required a 6-millimeter incision and sutures, and there were issues with it clipping onto the iris. Additional complications were reported with this lens, such as lens decentering, suture erosion, and endothelial cell loss.2
STAAR Surgical first released a posterior chamber phakic IOL in 1993, which was made with a novel biocompatible material called collamer.3 Collamer is comprised of a blend of polymer and collagen that makes the lens lighter, hydrophilic, and allows for better exchange of gas and nutrients. This patented material consists of 60% poly(2-hydroxymethyl methacrylate) called Poly-HEMA or pHEMA for short, water (36%), benzophenone (3.8%), and 0.2% porcine collagen.3
In 2005 when the Visian ICL was first made commercially available to the United States, surgeons largely only implanted it in patients with very high prescriptions who were traditionally not a candidate for any other refractive surgery, explained Dr. Wiley. This lens tended to perform well for high myopes with more extreme refractive errors (-10 to -18D) but generally wasn’t recommended for patients with lower refractive errors.
However, since the release of the EVO ICL, Dr. Wiley and his colleagues have begun incorporating it more into treatments for patients with medium refractive error—meaning that currently, most of his patients are candidates for the ICL.
Patient selection for phakic IOLs3,4,5
- Visian ICL
- For adults aged 21 to 45 years
- Approved to correct myopia ranging from -3.0D to -15.0D with ≤2.5D of astigmatism at the spectacle plane
- Approved to reduce myopia ranging from greater than -15.0D to -20.0D with ≤2.5D of astigmatism at the spectacle plane
- Internal anterior chamber depth (ACD) of 3mm or greater
- Stable refractive history within 0.5D for 1 year is required prior to implantation
- Visian Toric ICL
- For adults aged 21 to 45 years
- For the correction of myopic astigmatism with spherical equivalent ranging from -3.0D to ≤-15.0D (in the spectacle plane) with cylinder (spectacle plane) of 1.0D to 4.0D
- For the reduction of myopic astigmatism with spherical equivalent ranging from greater than -15.0D to -20.0D (in the spectacle plane) with cylinder (spectacle plane) 1.0D to 4.0D
- ACD of 3.0mm or greater when measured from the corneal endothelium to the anterior surface of the crystalline lens
- Stable refractive history within 0.5D for 1 year is required prior to implantation
- EVO/EVO+ Visian ICL
- For patients 21 to 60 years old
- Indicated for the correction/reduction of myopia in patients ranging from -0.5D to -20.0D at the spectacle plane
- ACD ≥3.0mm, as measured from the corneal endothelium to the anterior lens capsule
- Verisyse Phakic IOL
- For the reduction of myopia in adults with myopia ranging from -5.0D to -20.0D with ≤2.5D of astigmatism at the spectacle plane
- ACD of at least 3.2mm
- Patients with documented stability of refraction for the prior 6 months, as shown by spherical equivalent of less than or equal to 0.5D
Contraindications for phakic IOLs
Candidates who require careful consideration or may be contraindicated for implantation of phakic IOLs include those with:1
- Active anterior segment disease
- Recurrent or chronic uveitis
- Cataracts
- Previous ocular surgery
- Glaucoma or intraocular pressure (IOP) >21mmHg
- Preexisting macular pathology
- Retinal disease
- Anomalous irises or pupil
- Systemic diseases classically associated with poor post-operative healing
Contraindications for ICLs include patients with an ACD from endothelium <3mm, anterior chamber angle less than grade II (trabecular meshwork [TM]) determined by gonioscopic examination, pregnant or nursing, or patients who do not meet appropriate endothelial cell density as determined by an age-dependent minimum.3
Surgical considerations for phakic IOLs
Dr. Wiley remarked that at his practice the surgical protocol for RLE or cataract surgery is very similar to the process for implanting phakic IOLs. He also uses similar anesthesia, either sublingual (MKO Melt) or intravenous sedation (i.e., midazolam, fentanyl, or ketamine).
Additionally, the procedure utilizes similar instrumentation, such as small-incision blades, ophthalmic viscoelastic devices (OVDs), and positioning tools. Ultimately, implanting phakic IOLs works in the wheelhouse of traditional anterior segment lens surgeons and requires functionally the same skill set, remarked Dr. Wiley.
Pre-operative sizing for phakic IOLs
A further consideration for implanting phakic IOLs is accurately performing preoperative sizing. Of note, the ICLs designed by STAAR Surgical have a plate-haptic design that is available in four sizes (12.1mm, 12.6mm, 13.2mm, and 13.7mm in length) and is 7.5 to 8.0mm wide.3
Dr. Wiley explained that since, in his experience, most patients tend to fit in the two middle lens sizes, to measure the appropriate size of the lens diameter, he first uses handheld digital calipers to help narrow down the options. He then double-checks the measurement with biometry white-to-white (WTW) and Pentacam topography WTW.
It is also possible to incorporate ultrasound biomicroscopy, very high-frequency ultrasound (VHFUS), and optical coherence tomography (OCT) into the procedure to guide the surgery and precisely size the lens.6
Intraoperative pearls for implanting phakic IOLs
Dr. Donnenfeld prefers to implant phakic IOLs under topical anesthesia, maximum pupil dilation with intraoperative lidocaine and epinephrine, and with a 3-mm incision. He implants the lens utilizing viscoelastic to maintain a formed anterior chamber and then slips the lens under the iris.
There are four plates in the periphery, he noted, and you want to make sure that the hole in the peripheral footplate is round to the right. Once the lens is put in place, the viscoelastic is completely removed, Miochol-E (acetylcholine chloride intraocular solution, Bausch + Lomb) or Miostat (carbachol intraocular solution, Alcon) is injected to bring the pupil down, and then the patient is sent home.
Dr. Donnenfeld explained that in the past he implanted the ICL one eye at a time. Now, however, he almost universally performs the implantation on both eyes on the same day. Dr. Wiley added that he too almost exclusively performs the surgery on both eyes on the same day. On rare occasions when he is concerned about the size of the lens, he waits to implant it in the second eye to ensure that the first lens is properly sized.
When performing bilateral phakic IOL implantation, after implanting the first lens, Dr. Wiley uses the slit lamp to check the vault and ensure it is correct before placing the lens in the second eye. Similarly, after implanting the IOL in the first eye, Dr. Donnenfeld has the patient wait in a recovery room for 1 to 1.5 hours and then brings them into a clean room with a new set of instruments to start the second eye—much like a bilateral simultaneous cataract surgery.
Conclusion
Dr. Donnenfeld remarked that in the past, refractive surgery has largely been reserved for corneal specialists or doctors trained in refractive surgery.
However, he believes that implanting a phakic IOL, specifically the EVO ICL, is well within the surgical capabilities of every cataract surgeon.
Patients achieve a high level of quality vision as the cornea contour is not affected. Consequently, comprehensive ophthalmologists have an opportunity to incorporate and adopt phakic IOL technology into their surgical workflow for appropriate refractive patients.
