United States Patent 6,367,480: Scope, Claims, Expiration, and Trypan Blue Cataract-Surgery Patent Landscape

U.S. Patent No. 6,367,480 covers a surgical method for staining the anterior lens capsule with trypan blue before capsulorhexis. Its core limitations are the use of trypan blue in an ocularly compatible vehicle, delivery into the anterior chamber, interaction with a viscoelastic, staining of the anterior capsule, and subsequent cataract-surgery steps in the narrower claims.

The patent is no longer an enforceable U.S. patent. Its term expired approximately between 2019 and 2020, depending on the effective filing date and any patent-term adjustment. It does not create current exclusivity for trypan blue ophthalmic products, and it is not an Orange Book-listed drug patent that would ordinarily support a Paragraph IV certification.

What does U.S. Patent 6,367,480 protect?

The patent protects a method of visualizing the anterior lens capsule during cataract surgery by using trypan blue in the anterior chamber before capsulorhexis. The claimed technology addresses the difficulty of seeing the capsule, particularly in mature, white, or otherwise opaque cataracts.

The principal technical concept is:

Fill or partially fill the anterior chamber with a viscoelastic.
Introduce a trypan blue solution beneath or into the viscoelastic.
Allow sufficient time for the dye to stain the anterior lens capsule.
Remove excess dye and viscoelastic.
Reintroduce viscoelastic.
Perform capsulorhexis, remove the lens, and implant an intraocular lens.

The patent does not claim trypan blue as a chemical compound. It claims a surgical use of the compound.

Patent identification

Field	Information
U.S. patent	6,367,480
Patent type	Utility patent
Technical field	Ophthalmic surgery and cataract treatment
Claimed agent	Trypan blue
Claimed anatomy	Anterior lens capsule and anterior chamber
Claimed procedure	Capsulorhexis, lens removal, and intraocular-lens replacement
Issue date	April 9, 2002
Current status	Expired by 2026
Orange Book relevance	No direct Orange Book exclusivity identified
Primary commercial relevance	Historical protection for trypan-blue-assisted capsulorhexis

Source: U.S. Patent No. 6,367,480.

How broad is independent claim 1?

Claim 1 is the broadest visualization claim:

“A method for the visualization of an anterior lens capsule of a living human subject” using trypan blue in an ocularly compatible vehicle, followed by addition of a viscoelastic.

The claim contains several material limitations.

Living human subject

The claim is limited to a living human subject. It does not cover laboratory staining, cadaveric-eye procedures, animal procedures, or general nonclinical visualization unless the conduct also falls within another claim.

Anterior lens capsule

The target is specifically the anterior lens capsule. Staining the cornea, conjunctiva, posterior capsule, or other ocular tissue would not satisfy this limitation by itself.

Trypan blue solution

The claim requires trypan blue in solution. It does not specify a particular concentration, pH, buffer, solvent, formulation brand, container, or manufacturing process.

A product containing trypan blue could therefore fall within the claim when used in the claimed surgical sequence, even if the product uses a different excipient system from the historical formulation.

Ocularly compatible vehicle

The vehicle must be suitable for intraocular use. This limitation excludes ordinary laboratory trypan blue preparations that are not intended or suitable for introduction into the anterior chamber.

The term is functional and likely focuses on compatibility with the eye rather than a specific named ingredient. A saline, balanced salt, or comparable ophthalmic carrier could satisfy the limitation if it is used in an intraocularly acceptable formulation.

Addition of a viscoelastic

Claim 1 requires the trypan blue solution to be followed by addition of a viscoelastic. The sequence matters. A procedure using trypan blue without a viscoelastic would not meet the literal wording of claim 1, although it could raise separate issues under another claim or under an infringement-equivalence analysis.

The claim does not require:

A particular viscoelastic polymer
A specified viscosity
A particular volume
A specified exposure time
Capsulorhexis
Lens removal
Intraocular-lens implantation

Those limitations appear in the narrower claims.

What additional limitations appear in claims 2 and 4?

Claims 2 and 4 are more detailed procedural claims. They are materially narrower than claim 1 because they require a defined sequence and a concentration range.

Claim 2

Claim 2 requires:

Filling the anterior chamber with viscoelastic
Introducing trypan blue beneath the viscoelastic
Using approximately 0.05% to 3% w/w trypan blue
Waiting long enough to stain the anterior capsule
Removing excess trypan blue and viscoelastic
Reintroducing viscoelastic
Performing capsulorhexis
Removing the lens
Replacing it with an intraocular lens

The concentration range is broad. It spans a 60-fold range from 0.05% to 3% by weight. Commercial ophthalmic trypan blue products commonly use concentrations near 0.06%, placing those products within the literal numerical range when the claimed surgical sequence is performed.

The phrase “for a time sufficient to stain” is outcome-based. It does not establish a fixed number of seconds or minutes. The relevant question is whether the procedure allows staining adequate to visualize the capsule.

Claim 4

Claim 4 is an independent cataract-treatment claim. It repeats the core procedural sequence in claim 2 but is not formally dependent on claim 1.

This distinction matters in claim construction. If claim 1 were challenged or construed narrowly, claim 4 would remain independently relevant because it recites its own complete method. Claim 4 still requires the concentration range, staining step, removal of excess solution and viscoelastic, reintroduction of viscoelastic, capsulorhexis, lens removal, and intraocular-lens replacement.

What does claim 3 protect?

Claim 3 adds a two-viscosity technique designed to reduce dye leakage.

It requires:

A less-viscous substance over the lens capsule
A more-viscous substance at the pupil margin
Use of the viscosity gradient to minimize leakage of trypan blue

This is the narrowest technical concept in the patent. A procedure using one viscoelastic, or two substances without the specified relative placement and viscosity relationship, would not literally meet claim 3.

Claim 3 may be difficult to assert against ordinary cataract surgery unless operative records, expert testimony, or product instructions establish the use of differing viscosities in the claimed arrangement.

How do the claims compare?

Claim	Type	Core limitations	Relative breadth
1	Independent visualization method	Trypan blue, ocular vehicle, anterior chamber, living human, followed by viscoelastic	Broadest
2	Dependent procedural claim	Claim 1 plus 0.05%-3% concentration, staining, removal, reintroduction, capsulorhexis, lens removal, IOL replacement	Narrower
3	Dependent viscosity claim	Differing viscosities, less viscous over capsule, more viscous at pupil margin	Narrow and technique-specific
4	Independent cataract-treatment method	Detailed staining and cataract-surgery sequence, including IOL replacement	Narrower than claim 1; independent

When did U.S. Patent 6,367,480 lose exclusivity?

The patent’s enforceable term ended approximately between 2019 and 2020. U.S. utility patents generally have a term of 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and applicable transitional rules (35 U.S.C. § 154).

Because Patent 6,367,480 issued in 2002, its issue date does not determine expiration. The controlling date is the effective filing date for the patent family, not April 9, 2002.

By 2026:

The patent cannot block a new surgical use of trypan blue in the United States.
The claims do not create a current barrier to generic or branded trypan blue ophthalmic products.
A new product does not need a license from the patent owner solely because its labeling or use resembles the claimed method.
Patent infringement liability for past conduct would depend on the applicable historical expiration date and the acts occurring during the enforceable term.

Is Patent 6,367,480 listed in the Orange Book?

The patent is a method-of-surgery patent rather than a conventional drug-composition patent. It is not the type of patent ordinarily listed in the FDA Orange Book for an approved prescription drug product.

Orange Book listings generally identify patents claiming an approved drug substance, drug product, or approved method of use for an NDA product. A surgical-use patent may be relevant to product labeling or commercial strategy without being an Orange Book-listed patent.

The practical consequences are significant:

The patent does not ordinarily generate a 30-month stay through an ANDA Paragraph IV dispute.
A generic applicant would not normally need to certify Paragraph IV against this patent.
Patent 6,367,480 would not ordinarily prevent FDA approval of a trypan blue ophthalmic product through the Hatch-Waxman patent-certification process.
Infringement, if the patent had remained active, would have focused on use of the product in surgery rather than merely making or selling trypan blue.

Are there Paragraph IV challenges or generic-entry disputes?

No conventional Paragraph IV challenge is expected for this patent. Paragraph IV certifications apply to patents listed in the Orange Book for an NDA reference product. Patent 6,367,480 claims a surgical method and is not a composition claim covering trypan blue itself.

The competitive issue is therefore regulatory and commercial rather than an Orange Book litigation issue:

A manufacturer can develop an ophthalmic trypan blue product without practicing the claimed surgical method.
A surgeon’s use of the product during cataract surgery would have been the relevant infringement event during the patent term.
After expiration, the method claims no longer create a meaningful generic-entry barrier.

What formulations are protected by the patent?

The patent does not claim a specific commercial formulation. It requires trypan blue in an ocularly compatible vehicle.

The claims do not expressly require:

A 0.06% concentration in every claim
A particular buffer
A particular osmolarity
A particular preservative system
A particular vial, syringe, or delivery cannula
A particular manufacturing process
Sterile filtration or terminal sterilization

Claims 2 and 4 include the 0.05%-3% w/w range. A formulation outside that range could avoid the literal concentration limitation of those claims, but claim 1 does not contain that numerical limitation.

A formulation analysis must separate two questions:

Whether the product itself falls within a claimed composition, which this patent generally does not claim.
Whether a physician’s use of the product meets the claimed surgical method, which was the principal historical risk.

What manufacturing and intellectual-property barriers remain?

Patent 6,367,480 does not create a current manufacturing barrier. It does not claim:

Synthesis of trypan blue
Purification of trypan blue
Sterile manufacturing
Filling or packaging equipment
A proprietary injector
A combination product
An intraocular-lens design
A new chemical entity

Current barriers are more likely to arise from regulatory compliance, sterility, ophthalmic safety, container-closure performance, labeling, quality systems, and market access.

Separate patents may cover delivery devices, intraocular lenses, viscoelastic compositions, or manufacturing processes. Those rights must be analyzed independently. They cannot be inferred from Patent 6,367,480.

What is the biosimilar risk?

There is no biosimilar pathway issue for trypan blue. Trypan blue is a small-molecule dye, not a biologic. FDA competition would involve a drug, device, or combination-product pathway depending on the product’s classification and intended use, not a biosimilar application under the Public Health Service Act.

The relevant competitive products are ophthalmic trypan blue preparations and alternative capsule-visualization techniques, not biosimilars.

Which companies could compete with products covered by the historical method?

The historical commercial field included ophthalmic surgical suppliers offering trypan blue products for anterior-capsule staining. Examples associated with the market include DORC’s VisionBlue and other ophthalmic-surgery suppliers offering trypan blue preparations.

Commercial competition is based on:

Sterile ophthalmic formulation
Regulatory authorization
Surgeon familiarity
Distribution through cataract-surgery channels
Compatibility with viscoelastic and surgical instruments
Product concentration and presentation
Hospital purchasing contracts

The patent did not provide a durable product monopoly because it claimed the surgical method rather than the active ingredient.

How strong was the patent estate?

The patent was technically important but narrow as a portfolio asset.

Strengths

It captured the central clinical use of trypan blue for capsule visualization.
Claim 1 was comparatively broad because it lacked a concentration limitation.
Claims 2 and 4 described a commercially recognizable cataract-surgery workflow.
The claims addressed both visualization and cataract treatment.

Weaknesses

The patent did not claim trypan blue itself.
It did not claim a proprietary formulation.
It did not claim manufacturing or delivery technology.
Method-of-treatment enforcement would require proof of the surgical steps.
Claims 2 and 4 contain multiple sequential limitations.
Claim 3 requires a specialized two-viscosity arrangement.
The patent is expired.

The estate therefore had stronger historical relevance for clinical-use licensing than for long-term product exclusivity.

What generic launch scenarios exist now?

Because the patent has expired, three commercial scenarios are available:

Scenario	Patent impact
Launch of a trypan blue ophthalmic product	No current blocking effect from Patent 6,367,480
Use of trypan blue during capsulorhexis	No current infringement risk from this expired patent
Development of a competing capsule-staining technique	No current restriction from this patent

A current freedom-to-operate review would need to examine later patents covering formulations, devices, combination products, labeling, and specific ophthalmic delivery systems. Those rights are outside the four claims provided.

Key Takeaways

U.S. Patent 6,367,480 claims methods for staining the anterior lens capsule with trypan blue during cataract surgery.
Claim 1 is the broadest claim and requires trypan blue, an ocularly compatible vehicle, anterior-chamber use, a living human subject, and subsequent viscoelastic use.
Claims 2 and 4 require a detailed surgical sequence and a trypan blue concentration of approximately 0.05%-3% w/w.
Claim 3 requires a two-viscosity technique intended to reduce dye leakage.
The patent does not claim trypan blue as a chemical compound, a specific formulation, or a manufacturing process.
The patent expired approximately between 2019 and 2020 and provides no current U.S. exclusivity.
It is not a conventional Orange Book patent and would not ordinarily support a Paragraph IV challenge or 30-month stay.
Trypan blue is a small-molecule dye, so biosimilar analysis does not apply.
Current commercial barriers are more likely to involve FDA authorization, sterile manufacturing, formulation quality, delivery systems, and later patent families.

Frequently Asked Questions

Does Patent 6,367,480 cover all ophthalmic trypan blue products?

No. It primarily covers specified surgical uses, not trypan blue as a compound or every ophthalmic formulation.

Does a 0.06% trypan blue product fall within claims 2 and 4?

The concentration is within the claimed 0.05%-3% range. The other procedural limitations must also be performed for the method claim to be met.

Can a surgeon use trypan blue during capsulorhexis today without this patent blocking the procedure?

Yes. Patent 6,367,480 is expired and no longer blocks that use.

Is trypan blue subject to a biosimilar approval pathway?

No. Trypan blue is a small-molecule dye, not a biologic medicine.

Does the patent cover the intraocular lens implanted after cataract surgery?

No. The intraocular lens is a step in claims 2 and 4, but the patent does not claim the lens itself.

References

U.S. Patent No. 6,367,480. (2002). Use of trypan blue for visualization of the anterior lens capsule. United States Patent and Trademark Office.
United States Code, 35 U.S.C. § 154. Patent term.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. FDA Orange Book.
U.S. Food and Drug Administration. (n.d.). Generic drug patent certification and Paragraph IV litigation framework. FDA.

Details for Patent: 6,367,480

Summary for Patent: 6,367,480