Designing Ocular Assessment Endpoints: A Protocol Consultation Guide for Sponsors

Many of the ocular endpoint problems 20/20 Onsite is called in to fix start in the protocol, long before the first participant sits down for an eye exam. A vague best-corrected visual acuity (BCVA) procedure, a missing optical coherence tomography (OCT) scan specification, or a visit window that ignores dilation can surface months later as deviations, rescans, or an amendment. Designing ocular assessment endpoints with ophthalmic input at the protocol stage prevents many of those problems before they start. Here is how sponsors can define approvable endpoints, match assessments to them, and use protocol consultation to keep amendments off the timeline.

Why Ocular Endpoints Break Down After the Protocol Is Signed

A common failure point is a protocol that names the assessment but not the conditions that make it repeatable. BCVA scores shift with chart distance, lighting, and refraction method. OCT measurements shift with device model and scan protocol. When those details are left to each site, the same endpoint gets measured several different ways.

Fixing that after enrollment starts is slow and costly. A 2024 Tufts Center for the Study of Drug Development (CSDD) analysis found that 76% of Phase 1 to 4 protocols now have at least one amendment, up from 57%, with an average of 3.3 amendments per protocol. The same study found that moving from the need to amend to final oversight approval takes an average of 260 days, and sites operate on different protocol versions for an average of 215 days.

For a trial with ophthalmic endpoints, 215 days of mixed versions can mean mixed assessment methods inside one dataset. Tufts classified most amendments as unavoidable, with regulatory agency requests among the top reasons. Protocols cannot prevent every change, but they can make sure the ophthalmic plan is specific enough to hold steady and flexible enough to absorb one.

If your protocol is still in draft, this is the lowest-cost point to fix it. Request a Protocol Review with 20/20 Onsite's clinical team.

What Makes an Ocular Assessment Endpoint Approvable?

An approvable ocular endpoint measures a clinically meaningful change in visual function, or a structural marker with evidence that it predicts one. FDA and National Eye Institute (NEI) discussions treat visual function as the anchor, with anatomical measures in a supporting role unless they are validated. Settle this hierarchy before choosing a single assessment.

Three reference points shape most designs:

• Best corrected visual acuity: A report from the NEI/FDA Ophthalmic Clinical Trial Design and Endpoints Symposium states that a 3-line (15-letter) change represents clinical significance. Smaller changes can be acceptable when the treatment's risk is correspondingly small.
• Optical coherence tomography: The same report cautions that OCT changes do not always track visual function. Sponsors using retinal thickness as an endpoint in age-related macular degeneration (AMD) trials must show an associated change in visual function.
• Intraocular pressure (IOP): According to the NEI/FDA glaucoma symposium report, FDA separates an IOP-lowering indication from a glaucoma indication. Visual field progression can serve as a primary endpoint when a between-group difference is shown.

Surrogate endpoints open another regulatory path. FDA's accelerated approval program allows drugs for serious conditions with unmet need to be approved based on a surrogate endpoint, a marker thought to predict clinical benefit. For gene therapy and inherited retinal disease programs, decide early which exploratory endpoints you will collect with the same rigor as the primary endpoint.

How Do You Match Ophthalmic Assessments to Endpoints by Therapeutic Area?

Start with the endpoint, then choose the fewest assessments that measure it reliably and keep patients safe. The right mix depends on the therapeutic area and on whether the eye is the target organ or a safety concern.

Non-ophthalmic programs deserve the same rigor. When a drug class carries a known or suspected ocular risk, baseline exams must be captured exactly the way follow-ups will be, or a real safety signal becomes hard to separate from measurement noise. Slit lamp examination, for example, is a standard way to document anterior segment inflammation such as iritis. Our review of GLP-1 clinical trial eye safety shows how this plays out in practice.

How Protocol Consultation Prevents Amendments

Protocol consultation brings ophthalmic specialists into the draft to test each assessment against the endpoint, the visit schedule, and site capacity. 20/20 Onsite's Protocol Review aligns ocular assessments with study endpoints, validates compliance, and reduces risk across multi-center studies. Here is what that looked like when sponsors brought 20/20 Onsite in.

• Removing redundant assessments: During a Phase 1 study for Syneos Health, 20/20 Onsite's consultative review recommended eliminating redundant vision assessments through a protocol amendment to cut cost and complexity. A Mobile Vision Clinic placed at the research facility then eliminated 85.5 hours of participant travel.
• Called in mid-enrollment: When FDA required ophthalmic assessments midway through four trials, the sponsor called 20/20 Onsite, and all 65 sites were fully operational within 8 weeks, with certified ETDRS visual acuity testing, OCT, and ultra-widefield fundus imaging.
• Protocol-aligned pre-screening: For an ophthalmic gene therapy sponsor, 28 of 34 initial participants (82%) were pre-screened and qualified through Mobile Vision Clinic assessments. The trial went on to earn FDA Fast Track designation.

"A protocol tells a site what to measure. It rarely tells them how to measure it the same way at month 12 as at baseline, and that gap is where most of our protocol review time goes." Dr. David Gibson, OD, Chief Clinical Officer, 20/20 Onsite.

A Protocol Consultation Checklist for Ocular Endpoints

Work through these steps before the protocol is final. Each one closes a gap that commonly becomes a deviation or an amendment.

Leaner, better-sequenced visits also improve the patient experience, which supports retention. 20/20 Onsite reports 91% patient retention against a 70% industry standard.

Bring Ophthalmic Expertise In Before the Protocol Is Final

Endpoint quality is decided at the protocol stage, not at the first visit. 20/20 Onsite delivers BCVA, IOP, OCT, visual fields, slit lamp biomicroscopy, and fundus photography at the point of need, with a 98% data submission accuracy rate. Its Protocol Review aligns those assessments with your endpoints before a single site is activated.

Request a Protocol Review to have our clinical team assess your draft.

Frequently Asked Questions