United States Drug Patent 6,696,430: Claim Scope, Expiration, Litigation Risk, and Patent Landscape

U.S. Patent No. 6,696,430 protects a surgical method for staining and removing a retinal disorder membrane while avoiding substantial staining of the internal limiting membrane and underlying retinal layers. The patent covers selected vital dyes, concentration ranges, physiologically compatible saline solutions, and use in vitreoretinal surgery.

The patent is a method-of-treatment patent, not a composition patent. It does not independently claim trypan blue, indocyanine green, brilliant cresyl blue, a surgical instrument, or a marketed ophthalmic product. Its practical value depended on performing the claimed staining-and-removal sequence in the United States. The patent term has expired, eliminating current U.S. infringement risk from the issued claims.

What does U.S. Patent 6,696,430 cover?

The patent covers a selective staining technique used during retinal surgery. The claimed procedure requires three principal steps:

Surgically opening the eye.
Applying a vital dye to a retinal disorder membrane on the inner retinal surface.
Surgically removing the stained membrane.

The critical limitation is the staining selectivity. The membrane must be stained without substantially staining the internal limiting membrane, or the retinal layers beneath it, relative to the membrane being removed (U.S. Patent No. 6,696,430, 2004).

The invention addresses a surgical problem in epiretinal membrane and proliferative vitreoretinopathy procedures. These membranes can be difficult to distinguish from the internal limiting membrane and the retinal surface. Selective staining can improve visualization and facilitate membrane peeling.

What are the independent claim limitations?

Claim 1 is the only independent claim. A practicing surgeon or product developer would need to evaluate each limitation as a single combination:

Claim element	Scope
Surgical opening of the eye	Requires an operative vitreoretinal procedure rather than an external diagnostic or imaging procedure
Retinal disorder membrane	Covers a membrane located on the inner surface of the retina, on the vitreous-facing side
Vital dye application	Requires applying a dye to the membrane during the procedure
Selective staining	The membrane must stain without substantial staining of the internal limiting membrane or underlying retinal layers
Surgical removal	Requires removal of the stained membrane

A dye product used only for visualization, without removal of the stained membrane, would not satisfy the complete wording of claim 1. Conversely, a procedure that removes a membrane without applying a dye would fall outside the claim.

How do claims 2 through 9 narrow the patent scope?

The dependent claims add disease, procedure, dye, concentration, and formulation restrictions.

Claim	Added limitation	Commercial relevance
2	Membrane formed by proliferative vitreoretinopathy	Covers a specific source of pathological membrane formation
3	Membrane is an epiretinal membrane	Targets a major surgical use case
4	Procedure is part of vitreoretinal surgery	Confirms the surgical context
5	Dye stains tissue without substantially diffusing through it	Narrows the dye behavior and localization
6	Trypan blue, trypan red, brilliant cresyl blue, or indocyanine green	Creates a closed list of specified dyes
7	Dye concentration of 0.01% to 3% by weight	Broad concentration range
8	Physiologically compatible solution containing 0.8% to 1.0% salt	Narrows the carrier formulation
9	Sodium chloride, sodium phosphate, potassium chloride, calcium chloride, or magnesium chloride	Specifies permitted salts

Claims 2 and 3 are important for infringement analysis because they identify the two principal membrane categories addressed by the patent. Claim 6 is important for product screening because it identifies named dyes rather than relying only on functional language.

What is the strongest part of the patent claim set?

The strongest practical protection was the combination in claim 1, not any individual dye or concentration limitation.

The claim does not require a particular brand, delivery instrument, surgical gauge, or exact dye concentration. It uses functional language focused on selective staining. That structure potentially reaches different commercial formulations if they are used to stain and remove the targeted membrane while avoiding substantial staining of the internal limiting membrane.

The claim also avoids limiting the method to one disease. Claims 2 and 3 identify proliferative vitreoretinopathy and epiretinal membranes, but claim 1 is broader because it covers a retinal disorder membrane generally.

Claim 5 reinforces the technical concept by requiring a dye capable of staining tissue without substantial diffusion through that tissue. The language supports a distinction between localized membrane staining and diffuse staining of the retina.

What are the main claim-construction issues?

What does “without substantially staining” mean?

“Without substantially staining” is the principal scope boundary. The claim requires a comparison between staining of the targeted membrane and staining of the internal limiting membrane or underlying retinal layers.

The term is likely to be evaluated using clinical evidence, laboratory staining data, product instructions, expert testimony, and the patent specification. A product does not necessarily avoid the claim because it produces some incidental staining. The claim allows staining that is not substantial relative to staining of the retinal disorder membrane.

What does “retinal disorder membrane” cover?

The phrase is broader than “epiretinal membrane.” It can encompass membranes associated with proliferative vitreoretinopathy and other pathological formations on the retinal surface. Claims 2 and 3 provide narrower examples but do not necessarily limit claim 1 to those conditions.

Is the dye itself patented?

No. Claim 6 identifies four dye classes or compounds within a method claim. It does not claim trypan blue, trypan red, brilliant cresyl blue, or indocyanine green as standalone compositions.

A manufacturer could therefore sell a dye for other ophthalmic uses without practicing the patent. Infringement would depend on the claimed surgical use and staining outcome.

Does the patent claim a formulation?

Claims 7 through 9 create formulation-related method limitations. They do not claim a bottle, vial, prefilled syringe, or composition in isolation. The formulation limitations matter only when the solution is used in the claimed surgical method.

When did U.S. Patent 6,696,430 expire?

U.S. Patent No. 6,696,430 issued on February 24, 2004. Its term ran from the applicable nonprovisional filing date under the post-1995 patent-term rules and has ended. The patent is listed as expired in public U.S. patent records (U.S. Patent and Trademark Office [USPTO], n.d.).

Event	Date or status
U.S. patent number	6,696,430
Issue date	February 24, 2004
Patent type	Utility patent
Subject matter	Retinal membrane staining and removal method
Current U.S. status	Expired
Current enforceability	No enforceable issued claims based on ordinary patent-term expiration

The expired status removes the principal U.S. patent barrier created by the patent. It does not eliminate other possible rights, including later patents covering a particular dye formulation, device, manufacturing process, packaging system, or use.

What is the Orange Book status of U.S. Patent 6,696,430?

U.S. Patent No. 6,696,430 is not an Orange Book-listed drug patent.

The Orange Book lists patents submitted for approved drug products, including patents covering active ingredients, formulations, compositions, and methods of use for FDA-approved drugs. Patent 6,696,430 claims a surgical method involving retinal membrane staining and removal. It does not claim an approved drug product as such and is not the type of patent ordinarily listed against an NDA product in the Orange Book (FDA, 2024).

The commercial products associated with this technology may instead be regulated as ophthalmic surgical devices or device-associated products, depending on their formulation, labeling, and regulatory classification.

Do Paragraph IV challenges apply to this patent?

A conventional Paragraph IV certification does not apply directly to U.S. Patent No. 6,696,430 because the patent is not an Orange Book-listed drug patent.

Paragraph IV litigation typically arises when an abbreviated new drug application applicant certifies that an Orange Book-listed patent is invalid, unenforceable, or will not be infringed. A supplier of trypan blue or another surgical dye could face other patent claims, product liability claims, or regulatory issues, but this expired method patent does not create a current Paragraph IV barrier.

What is the FDA regulatory status of retinal staining dyes?

Retinal staining products are generally evaluated through medical-device or combination-product pathways rather than through the standard generic-drug pathway alone. Products used during ophthalmic surgery may require FDA clearance or approval based on their intended use, formulation, sterility, delivery, and risk profile.

FDA records identify ophthalmic tissue-staining products, including products using trypan blue, for intraocular surgical use. FDA approval of a commercial dye does not establish freedom to operate under every patent. It establishes regulatory authorization for the labeled use, while patent rights are analyzed separately (FDA, n.d.-a).

The expiration of Patent 6,696,430 reduces patent risk for the claimed staining-and-removal method. It does not automatically authorize off-label use, eliminate device requirements, or resolve later patent rights.

What products and technologies compete with the patented method?

The relevant competitive field includes:

Trypan blue ophthalmic staining products.
Brilliant blue or brilliant cresyl blue staining products.
Indocyanine green used for membrane or internal limiting membrane visualization.
Combination staining solutions.
Surgical visualization systems and membrane-peeling instruments.
Alternative procedures that improve membrane visualization without the claimed dye technique.

The patent’s claim 6 specifically names trypan blue, trypan red, brilliant cresyl blue, and indocyanine green. A later product using one of those dyes is not currently exposed to this patent because the patent has expired.

How does trypan blue compare with indocyanine green?

Issue	Trypan blue	Indocyanine green
Principal surgical use	Epiretinal membrane visualization and staining	Often associated with internal limiting membrane visualization
Relevance to patent claim 6	Expressly listed	Expressly listed
Key risk under the expired patent	None from this patent’s expired claims	None from this patent’s expired claims
Commercial evaluation	Concentration, sterility, labeling, device pathway	Concentration, retinal safety, indication, and delivery

The technical and regulatory risks differ by dye. A product may avoid the original claim’s selective-staining concept if its intended use and staining behavior do not meet the claim limitations, but the expired status makes that distinction commercially less important for current U.S. market entry.

What patent landscape surrounds retinal membrane staining?

The surrounding landscape can be divided into five categories:

Patent category	Typical protected subject matter	Relevance after expiration of 6,696,430
Surgical method patents	Applying dye and peeling retinal membranes	The core patent is no longer enforceable
Composition patents	Dye concentration, buffers, excipients, and stabilizers	May remain relevant if later filed
Device patents	Cannulas, injectors, fluidics, and visualization instruments	Separate freedom-to-operate review required
Manufacturing patents	Sterile filtration, packaging, filling, and storage	Can create supply-chain barriers
Method-of-use patents	Specific retinal diseases, surgical sequences, or patient groups	May cover narrower commercial indications

The principal patent-landscape risk has shifted from the expired staining method to later product-specific rights. A current launch assessment should review patent families assigned to ophthalmic surgical manufacturers, dye suppliers, and instrument companies, with separate searches for trypan blue, brilliant blue, indocyanine green, epiretinal membrane, internal limiting membrane, vitrectomy, and membrane peeling.

Which companies are relevant to the competitive landscape?

The commercial field has included ophthalmic surgical companies and specialty dye suppliers such as DORC International and other manufacturers of intraocular staining products. Product ownership, regulatory sponsorship, distribution rights, and patent ownership may differ by jurisdiction and product generation.

Patent 6,696,430 should not be treated as proof that a current commercial product is protected by an active patent. The original method claims are expired, and current protection, if any, would need to come from later patents, trademarks, regulatory exclusivity, trade secrets, or contractual distribution rights.

What licensing and settlement issues affect the patent?

The patent document establishes the issued claims and recorded ownership information, but it does not itself establish the existence of a commercial license or settlement agreement. Because the patent has expired, a prior license would generally have limited value as a current U.S. exclusivity tool unless it included separate rights covering confidential manufacturing technology, trademarks, know-how, or later patents.

No Paragraph IV settlement framework is expected for this patent because it was not an Orange Book-listed drug patent. Any historical commercial agreement would need to be evaluated separately from the expired patent claims.

What generic or competing launch scenarios exist?

Scenario 1: Generic or alternative trypan blue product

A competing trypan blue product can enter the U.S. market without infringing the expired claims of Patent 6,696,430. Regulatory approval, sterility, labeling, manufacturing controls, and product-specific patent rights remain relevant.

Scenario 2: New formulation

A buffered or combination formulation may avoid later composition claims, but it could also create new patentable subject matter for the developer. Concentration and excipient choices should be screened independently of the expired method patent.

Scenario 3: New surgical device

A cannula, injector, or automated delivery platform may have separate device patent exposure. The expiration of the staining method patent does not provide freedom to operate for the equipment.

Scenario 4: Alternative visualization technology

A system using optical contrast, intraoperative imaging, or a nonlisted dye may avoid both claim 6 and some of the technical limitations in claim 1. It may still face later device or method patents.

How strong is the patent estate today?

The estate created by U.S. Patent No. 6,696,430 is commercially weak today because the patent has expired. During its term, claim 1 had meaningful breadth because it covered a functional staining result rather than one formulation or instrument. Claims 6 through 9 supplied narrower fallback positions around named dyes and concentrations.

Current strength assessment:

Factor	Assessment
Claim breadth during term	Moderate to broad for the surgical method
Composition protection	Limited
Device protection	None apparent from the asserted claims
Orange Book relevance	None
Paragraph IV relevance	None
Current U.S. enforceability	None due to expiration
Manufacturing barrier	Not created by the issued claims
Current launch risk from this patent	Low to none

Key Takeaways

U.S. Patent No. 6,696,430 claims a method of selectively staining and surgically removing retinal disorder membranes.
Claim 1 is the commercial center of the patent and requires eye surgery, dye application, selective membrane staining, and surgical removal.
Claims 2 and 3 cover proliferative vitreoretinopathy membranes and epiretinal membranes.
Claim 6 names trypan blue, trypan red, brilliant cresyl blue, and indocyanine green.
Claims 7 through 9 narrow the method by concentration and saline composition.
The patent is expired and does not create a current U.S. patent barrier.
The patent is not an Orange Book-listed drug patent, and Paragraph IV procedures do not directly apply.
Current freedom-to-operate risk must focus on later formulation, device, manufacturing, and method-of-use patents.
FDA authorization and patent freedom to operate are separate analyses.
The patent does not claim a dye composition, surgical instrument, or commercial brand in isolation.

Frequently Asked Questions

Does U.S. Patent 6,696,430 cover all uses of trypan blue in eye surgery?

No. It covers a specific surgical method involving selective staining and removal of a retinal disorder membrane. It does not claim trypan blue as a standalone compound or every ophthalmic use.

Can a company launch a retinal staining product after expiration of this patent?

The expiration removes this patent as a current U.S. infringement barrier. The company must still address FDA requirements, sterility, labeling, product-specific patents, device rights, and manufacturing claims.

Does the patent cover internal limiting membrane peeling?

The claims focus on staining and removing a retinal disorder membrane while avoiding substantial staining of the internal limiting membrane. A procedure directed to internal limiting membrane staining or peeling may require separate claim analysis.

Are trypan blue products generic drugs under the ANDA pathway?

Not necessarily. Ophthalmic surgical staining products may be regulated as devices or combination products, depending on their intended use and formulation. The FDA classification must be assessed product by product.

Can a later patent extend the exclusivity created by Patent 6,696,430?

A later patent cannot revive the expired claims of Patent 6,696,430. It may protect a different formulation, device, manufacturing method, concentration, delivery system, or surgical indication if the later claims satisfy patentability requirements.

References

Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files

Food and Drug Administration. (n.d.-a). Medical device databases and ophthalmic device records. U.S. Department of Health and Human Services. https://www.fda.gov/medical-devices/device-advice-comprehensive-regulatory-assistance/medical-device-databases

U.S. Patent No. 6,696,430. (2004). Method for removing a retinal disorder membrane. United States Patent and Trademark Office.

U.S. Patent and Trademark Office. (n.d.). Patent Center and patent term information. https://patentcenter.uspto.gov

United States Code, Title 35, §§ 154, 271, 282. (2024). Patents. Office of the Law Revision Counsel.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
	98201542	May 8, 1998
	98202751	Aug 17, 1998

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	232400	⤷ Start Trial
Austria	234118	⤷ Start Trial
Australia	2003208122	⤷ Start Trial
Australia	3853699	⤷ Start Trial
Australia	3853799	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,696,430

Summary for Patent: 6,696,430