Three-Year FDA Prospective Multicenter Clinical Study of the EVO/EVO+ Implantable Collamer Lens
Study At a Glance
The EVO ICL is a small implantable lens placed inside your eye to correct moderate to severe nearsightedness — it’s often recommended for people who aren’t good candidates for LASIK. This was the official FDA clinical trial used to approve the lens in the United States, tracking 629 patients across 14 clinics for three full years. NVISION’s own Dr. Gregory Parkhurst was the highest-volume surgeon in the entire study.
The results were strong across the board. After three years, nearly 91% of patients hit their target prescription within half a diopter, and on average patients could see better without glasses after surgery than they could with their best glasses before. Equally important for safety-conscious patients: there were zero cases of angle closure, zero cases of natural lens damage, and eye pressure remained stable the entire time. The lens exchange rate was just 0.3%.
Study Overview
This is the definitive U.S. FDA prospective multicenter clinical trial evaluating the long-term safety and effectiveness of the EVO and EVO+ Implantable Collamer Lens (ICL) for correction of moderate to high myopia, with or without astigmatism. Conducted under FDA Investigational Device Exemption (IDE), it represents the most rigorous regulatory evaluation of phakic lens technology ever completed in the United States — and the dataset upon which FDA approval of the EVO ICL was based.
629 eyes of 327 subjects were enrolled across 14 clinical sites in the U.S., with subjects aged 21 to 45 years and myopia ranging from -3.00 D to -15.62 D. Outcomes including uncorrected and corrected visual acuity, refraction, intraocular pressure (IOP), endothelial cell density (ECD), and adverse events were tracked over three full years. 92.1% of enrolled eyes completed the final three-year visit.
NVISION physician Dr. Gregory Parkhurst served as a principal investigator and is a co-author. The study was registered on ClinicalTrials.gov (NCT04283149), conducted under HIPAA regulations, and approved by Advarra Institutional Review Board. Dr. Parkhurst was the highest-volume EVO ICL implanter in the entire FDA clinical study.
Key Findings: Visual Acuity & Refractive Outcomes
| Metric | Result |
|---|---|
| Eyes within ±0.50 D of target refraction at 3 years | 90.7% |
| Eyes within ±1.00 D of target refraction at 3 years | 99.0% |
| Mean spherical equivalent at 3 years | −0.12 D (down from −7.62 D preoperatively) |
| Efficacy index at 3 years | 1.07 (postoperative UCVA better than preoperative BCVA) |
| Safety index at 3 years | 1.25 (postoperative BCVA better than preoperative BCVA) |
| Eyes gaining 1 or more lines of corrected vision | 48.9% |
| Eyes losing 2 or more lines of corrected vision | 0.32% (2 eyes) |
An efficacy index above 1.0 means that on average, patients could see better without correction after surgery than they could with their best glasses or contacts before surgery.
Key Findings: Safety
| Safety Metric | Result |
|---|---|
| Eyes with satisfactory vault at 3 years | 99.7% |
| Cases of angle closure | 0 |
| Cases of anterior subcapsular cataract | 0 |
| Cases of pigment dispersion | 0 |
| Mean IOP: preoperative vs. 3 years | 15.9 mmHg vs. 15.5 mmHg (stable) |
| Transient IOP increase (resolved, due to retained OVD) | 19.9% at 1–6 hours post-surgery; resolved with standard treatment |
| Lens exchange rate | 0.3% (2 eyes, due to vault adjustment) |
Intraocular pressure remained essentially unchanged from baseline through all three years of follow-up. None of the serious complications historically associated with phakic lens surgery — angle closure, pigment dispersion, or natural lens damage — occurred in this study population.
Study Context & Limitations
The study’s prospective, multicenter, FDA-regulated design represents the highest standard of clinical evidence in ophthalmology. The study population was limited to patients aged 21–45 with moderate to high myopia, consistent with the FDA-approved labeling for EVO ICL. As with all regulated device trials, all 14 sites followed identical protocols under IRB and FDA oversight.
The authors note that the 19.9% transient IOP elevation rate — the most frequently observed adverse event — was fully attributable to retained surgical viscoelastic material in the immediate post-operative window and resolved with standard treatment. It did not represent a persistent safety concern.
The study’s three-year duration, 629-eye enrollment, and 92% follow-up completion rate are considered benchmarks of clinical rigor in the field.