ICL Sizing Without UBM: How OCT and AI Are Changing EVO ICL Surgery

Accurate ICL sizing is the single most important variable in a successful EVO ICL (Implantable Collamer Lens) procedure. Choose a lens that is too long and the ICL vault runs high, crowding the angle; too short and the vault runs low, risking cataract. For decades, surgeons chasing a more precise size have reached for UBM (ultrasound biomicroscopy) to image the sulcus. But UBM is a contact ultrasound exam — and both the evidence and the patient experience now point somewhere better: OCT and AI.

The problem with UBM

UBM produces high-resolution images of the ciliary sulcus, but it comes with real trade-offs that matter in a busy refractive practice:

• It's a contact exam. A water-bath or probe touches the anesthetized eye — uncomfortable for patients and slower for the practice.
• It's operator-dependent. Sulcus-to-sulcus measurements vary with probe angle and technician skill, adding noise to the very number you're trying to nail.
• It doesn't reliably beat the alternatives. Sulcus dimensions correlate imperfectly with the final vault, so extra imaging doesn't guarantee a better size.

The result is a step that adds cost, chair time, and patient discomfort without a proportional gain in accuracy — friction that keeps many practices from scaling their ICL volume.

Why OCT + AI is the better path

Anterior-segment OCT is non-contact: a quick, comfortable scan captures the eye's individual dimensions with no probe on the cornea. Pair that image data with modern machine learning and you can predict postoperative ICL vault directly — learning the patterns that actually drive vault instead of relying on a single linear white-to-white nomogram.

This is exactly the thesis behind ICL Fit: an AI agent that turns a non-contact scan into a vault prediction your surgeon can act on before EVO ICL surgery. The approach is documented in the founding team's peer-reviewed, PubMed-indexed research in the Journal of Cataract & Refractive Surgery and Clinical Ophthalmology:

• VAULT (2024) — a novel image-based AI model showing that machine learning can predict ICL postoperative vault more accurately than conventional white-to-white nomograms.
• VAULT-OCT (2025) — extends the model to anterior-segment OCT, using deep learning to predict vault from the scan itself.
• Dynamic Changes in ICL Vault — shows vault is not fixed: it shifts as the pupil dilates and constricts under different lighting.

Best-fit-per-eye, not a target vault number

A common misconception is that ICL sizing means hitting one "ideal" vault in microns. It doesn't. Vault varies from eye to eye and even changes with lighting in the same eye. The goal is the best-fit lens size for the individual eye — the size most likely to land in a safe, comfortable range across real-world conditions. AI models trained on real outcomes are built to answer exactly that question, which is why image-based, OCT-driven sizing is displacing both UBM and one-size-fits-all nomograms.

A better patient experience

The clinical case for OCT + AI is also a patient-experience case. A non-contact scan means no ultrasound probe on the eye, less chair time, and a smoother, more modern visit — the kind of experience that drives referrals and lets a practice grow its EVO ICL program. Better accuracy and a better experience are not a trade-off here; they come from the same shift in technology.

Where technique meets sizing

Great sizing is necessary but not sufficient — surgical technique closes the loop. The ICL Workshop is a free, 18-video training series on EVO ICL surgery from the Parkhurst NuVision team, covering ICL power selection, loading and insertion, toric ICL rotation, preventing IOP spikes, and challenging cases. It pairs naturally with an OCT-based sizing workflow: size the eye accurately, then execute confidently.

The ICL Workshop is part of Refractive Foundations, the educational initiative of the World Council of Refractive Surgery Fellowships (WCRSF) — a broader curriculum for ophthalmology residents and refractive surgery fellows. Together, ICL Fit (sizing), the ICL Workshop (technique), and Refractive Foundations (education) form a complete, evidence-based pathway to a confident, high-volume EVO ICL practice — no UBM required.