Phakic IOL implantation offers a number of benefits for patients with myopia who are not candidates for laser vision correction.
Myopia is a recognised global epidemic expected to affect almost half of the world’s population by 2050. The currently widely used methods of myopia treatment and correction—glasses, contacts or laser vision correction—are not ideal for treating patients with thin or abnormal corneas, contact lens intolerance or anisometropia, according to Dr Gregory D. Parkhurst, the CEO of Parkhurst NuVision in San Antonio, Texas, United States. Those who are not candidates for laser vision correction may benefit most from implantation of a phakic IOL.
Dr Parkhurst and colleagues conducted a retrospective study1 of phakic IOL implantation in military personnel who received the Visian Implantable Collamer Lens (ICL; STAAR Surgical), and in whom laser vision correction was not ideal because of abnormal topography, thin predicted residual bed and/or dry eye disease. In these patients, refractive predictability within 0.5 D with the ICL was seen in 90% of eyes and 96% achieved 20/20 uncorrected vision, he reported.
The objective results are good in a population with abnormal corneas, so the obvious next question is whether this technology should be limited to individuals who are not considered candidates for laser vision correction. One study2 supported the idea that phakic IOLs provide the best quality-of-life scores compared with other refractive surgeries such as laser vision correction. In addition, Dr Parkhurst reported results that showed night vision was superior in patients with phakic IOLs compared with those who underwent wavefront-optimised LASIK even for moderate levels of myopia.3
One advantage associated with phakic IOLs is the relatively small learning curve to overcome for experienced anterior segment lens surgeons and the fact that the surgical technology is less expensive to access than laser equipment, which can cost several hundred thousand dollars to acquire. All a surgeon really needs is an operating microscope, a basic cataract set and a few special forceps to get started. In addition, the postoperative care is very similar to that associated with cataract and refractive lens surgery with the important addition of monitoring the vault of the phakic IOL, Dr Parkhurst pointed out.
As with any surgical procedure (or nonsurgical treatment of myopia), there are risks associated with phakic IOL implantation. Endophthalmitis is associated with the performance of any intraocular procedure and the rate associated with phakic IOL implantation is 0.017% (1 in 6,000 cases). Postoperative intraocular pressure (IOP) spikes that require intervention occur in 3.2% and the risk of pupillary block after implantation of the ICL is 0.7%, Dr Parkhurst noted.
Development of cataracts is another risk associated with implantation of phakic IOLs. Seven reports of 3 to 7 years of follow-up after phakic IOL implantation noted clinically relevant cataracts with incidence rates of less than 2%; one report cited a much higher risk of cataracts in patients with very high myopia and older age. In contrast, endothelial cell loss over time has not been a clinically significant problem with the ICL.
Future of ICLs
The future of phakic IOLs may include further improvements in safety resulting from better ways to size the ICL, Dr Parkhurst said, as well as minor design modifications, diagnostics and improvements in the sizing nomograms. “The sulcus distance is highly variable in eyes; accommodation plays a role as do the shape and anterior lens rise of the human crystalline lens,” he said.
Future developments in the ICL platform include the availability of presbyopia-correcting models. In addition, development of a lens with a central fenestration that was used in Europe resulted in fewer IOP spikes and no cataract development, possibly due to increased flow of aqueous over the anterior lens epithelial cells.
An important consideration for Dr Parkhurst, considering the good safety profile of the Visian ICL and the demand for refractive surgery, is use of a phakic IOL to preserve the cornea and lens for the future. When the cornea is borderline, he explained, the question that must be asked by surgeons is whether they would rather implant a phakic IOL and leave open all options for presbyopia and cataract correction, or potentially risk the integrity of the cornea with the associated risk of corneal transplantation or need for cross-linking. He often opts to implant a phakic IOL.
“As surgeons we must help our patients balance the risks, benefits and alternatives of all options to treat myopia,” Dr Parkhurst concluded. “Modern phakic IOLs offer high-quality vision, a low-risk profile and preserve the cornea and lens for the future, and can be an important tool for the comprehensive refractive surgeon.”
Gregory D. Parkhurst, MD, FACS
Dr Parkhurst is a consultant to STAAR Surgical.