Case Study: How Impression-Based Scleral Fitting Helped a Complex Bleb Patient Reach 20/25
Peeq Pro Clinical Review
Case Report · Scleral Lens Fitting
Impression-Based Scleral Lens Fitting Around a Filtering Bleb
FAAO, FIAOMC, IACMM, Diplomate ABO
Abstract
Fitting a scleral lens over a cornea with keratoconus and a history of corneal graft is already a non-trivial exercise in accommodating irregular post-graft topography.
Add a filtering bleb — a thin-walled, fluid-filled conjunctival elevation from glaucoma surgery that cannot tolerate mechanical loading — and the fitting problem changes from a comfort and optical challenge into a safety-critical one.
This report describes the impression-based design and outcome of a scleral lens fit in a patient with keratoconus, a history of penetrating keratoplasty (PK), and a superior filtering bleb, presenting with uncorrected visual acuity of 20/500.
Final corrected visual acuity was 20/25, achieved with zero mechanical impingement on the bleb.
Background
Filtering blebs are a known relative contraindication to standard scleral lens fitting. Diagnostic-lens-based fitting approaches rely on iterative adjustment from a stock trial set and estimate landing-zone elevation rather than measuring it directly.
In a bleb-bearing eye, that estimation carries real consequence: a landing zone that straddles or compresses the bleb risks trauma, leak, or outright bleb failure — a complication that threatens the patient's glaucoma control, not just their contact lens comfort.
This risk profile makes precise, patient-specific measurement of the ocular surface a clinical necessity rather than a refinement.
Case Presentation
The patient presented with uncorrected visual acuity of 20/500 in the affected eye.
Relevant history included keratoconus and a prior penetrating keratoplasty (PK), producing irregular post-graft corneal topography. The patient's glaucoma was managed surgically, with a superior filtering bleb present and requiring protection from any mechanical loading during lens wear.
Clinical Challenge
Two anatomic constraints had to be satisfied simultaneously.
First, the irregular post-graft corneal topography required adequate, well-distributed vault to avoid corneal touch.
Second, and more critically, the scleral landing zone had to entirely avoid the bleb.
A standard scleral fitting approach — designed and iterated from a stock diagnostic lens set — risks landing directly on or partially compressing the bleb, since the true elevation and extent of the bleb cannot be measured with certainty through trial-lens iteration alone.
Design Rationale
An impression of the ocular surface was taken directly on the eye, capturing the bleb's exact elevation and footprint rather than estimating it.
The lens was then manufactured from that impression, allowing the landing zone geometry to be planned around the bleb with precision instead of approximation.
Non-Negotiable Design Principles
Landing zone diameter must extend beyond the apex of the bleb. The haptic could not land on or straddle the bleb at any point.
Zero impingement on the bleb at any point along the haptic. Any compression risked bleb trauma, leak, or failure — an outcome with implications far beyond lens comfort.
Vault planned from measured elevation, not estimation. Because the impression captured the bleb's true topography, the vault height over the bleb was a calculated design parameter rather than a trial-and-error adjustment.
Outcome
The completed lens fully vaulted the bleb with no mechanical contact.
Final visual acuity was 20/25, corrected — an improvement from an uncorrected baseline of 20/500.
Discussion
This case illustrates a fitting scenario where the margin for error is defined by patient safety, not simply by comfort or optical performance.
A bleb-bearing eye does not tolerate the “close enough” landing zone that a stock diagnostic lens and iterative adjustment might eventually produce in a lower-stakes fit.
Impression-based design converts an estimation problem into a measurement problem: the clinician is designing the lens around the eye's actual, captured geometry, rather than converging toward it through successive trial lenses — each of which carries some risk of bleb contact before the ideal fit is found.
The visual outcome is dramatic, but the more clinically significant result is what didn't happen: the bleb was never compromised during fitting.
In a patient managing both a keratoconic, post-graft cornea and surgically controlled glaucoma, avoiding that risk while still restoring functional vision is the actual clinical win.
Conclusion
Impression-based scleral lens design allowed successful, safe visual rehabilitation in a patient whose anatomy — irregular post-graft cornea plus a surgical bleb — placed real limits on what a standard scleral fitting approach could responsibly attempt.
For patients where the sclera itself carries a structure that cannot be touched, measuring before designing is not a refinement of technique.
It's the technique that makes the fit possible at all.
Why This Work Matters in My Practice
Cases like this are exactly why I've built specialty contact lens fitting — orthokeratology, scleral lenses, and prosthetic design — into the core of what my practice offers, rather than treating it as a referral-out service.
Patients with this kind of anatomic complexity have usually already been told no somewhere else, sometimes more than once.
Having the clinical training and the impression-based technology to say yes instead has changed what my practice is able to do for the most difficult cases in our region — and it's some of the most meaningful work I do as a clinician.
It's also, frankly, good practice-building: this is the kind of case that becomes a referral source in itself once colleagues know it's something you can actually solve. Specialty expertise becomes even more powerful when you intentionally build relationships with the providers and communities who already encounter these patients.
Read: How to Build a Referral Engine Around the Patients You Actually Want →
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