US Patent 6,696,430: Scope, Claim Construction, and Landscape for Vital Dye-Assisted Removal of Retinal Disorder Membranes
US 6,696,430 claims a surgical method for removing a retinal disorder membrane from the inner retinal surface using a vital dye that stains the target membrane without substantially staining the internal limiting membrane (ILM) or underlying retinal layers. The core constraint is “target-specific” staining: the dye must bind/stain the membrane while avoiding substantial penetration and/or diffusion into structures beneath the ILM.
What Does Claim 1 Actually Require?
Claim 1 (independent) is the entire technical scope anchor. It requires three surgical and biochemical elements.
Step-by-step claim elements (verbatim logic)
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Surgical access
“surgically opening an eye”
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Vital dye application at the correct anatomic location
applying a vital dye onto the retinal disorder membrane
where the membrane is located “at an inner surface of a retina relative to vitreous.”
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Target-specific staining with an express exclusion
producing “a stained retinal disorder membrane” such that:
- the retinal disorder membrane is stained
- the method does not “substantially [stain] internal limiting membrane of the retina or retinal layers underlying the internal limiting membrane”
- the comparison is “compared to the stained retinal disorder membrane,” so the exclusion is relative to how strongly the target is stained.
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Surgical removal
“surgically removing the stained retinal disorder membrane from the inner surface of the retina”
Claim 1’s practical interpretation for freedom-to-operate
A method falls within Claim 1 if it:
- uses a vital dye applied directly during surgery to stain the target membrane that lies on the retinal inner surface (epiretinal membrane or similar)
- achieves staining of the membrane while avoiding substantial staining (relative effect) of ILM or tissue beneath it
- includes both surgical opening and surgical removal of the stained membrane
A method can avoid Claim 1 if it:
- stains ILM or underlying layers to a substantial degree (the claim sets a qualitative threshold but uses “substantially,” which in practice turns into evidence-based dispute)
- does not perform removal of the stained membrane as part of the method
- does not apply a “vital dye” (as claimed) or does not produce target staining without ILM staining
How Do Dependent Claims Narrow Scope?
Dependent claims lock in specific membrane types, procedure context, dye behavior, and composition ranges.
What retinal membranes are covered?
- Claim 2: membrane is formed by proliferative vitreoretinopathy (PVR)
- Claim 3: membrane is an epiretinal membrane
These two dependent claims broaden the “retinal disorder membrane” set from the generic to defined entities commonly targeted in vitreo-retinal surgery.
What is the procedural context?
- Claim 4: the method is part of a vitreo-retinal surgical procedure
This is broad and likely met by most ophthalmic membrane peeling workflows.
What dye behavior must be shown?
- Claim 5: dye can stain tissue “without substantially diffusing through said tissue.”
This introduces a diffusion-avoidance constraint that matters for accused products and protocols. It pushes the analysis toward:
- molecular size / chemical properties
- dwell time
- concentration
- exposure medium and wash steps
- whether dye is applied locally vs broadly
Which dyes are expressly named?
- Claim 6: vital dye selected from:
- trypan blue
- trypan red
- brilliant crysyl blue
- indocyanine green
Because these dyes are expressly enumerated, they define at least one literal infringement pathway. However, Claim 1 itself requires a “vital dye,” so named dyes strengthen obviousness/enablement questions and will anchor landscape searches even when later filings use different dyes.
What concentration and solution constraints apply?
- Claim 7: vital dye present in physiologically compatible solution at 0.01% to 3% by weight
- Claim 8: solution comprises salt 0.8% to 1.0% by weight
- Claim 9: salt selected from:
- sodium chloride
- sodium phosphate
- potassium chloride
- calcium chloride
- magnesium chloride
These dependent claims create a narrow formulation corridor. A protocol using the same dye but outside these concentration ranges (or using different salt systems) can be positioned outside dependent claim scope while still potentially arguing about Claim 1 coverage depending on how strongly ILM staining avoidance and “vital dye” status are evidenced.
Claim Scope Summary: What’s In vs. Out
Where infringement is strongest (literal fit)
A method is high-risk when all of the following are present:
- membrane peeling for epiretinal membrane or PVR-associated membranes
- dye is one of the enumerated vital dyes (trypan blue/red, brilliant crysyl blue, indocyanine green)
- dye is delivered in a physiologically compatible solution
- concentration and salt match dependent ranges
- the surgeon demonstrates (or the protocol is designed to ensure) that ILM and underlying layers are not substantially stained relative to the target membrane
Where infringement risk drops
- dye diffuses and substantially stains ILM/underlying layers (even if target membrane stains)
- procedure uses non-vital dyes or dyes not argued to meet “vital dye” characterization
- membrane removal occurs without the stained membrane step as claimed
- formulations outside 0.01% to 3% by weight or salt system and percentages outside 0.8% to 1.0% by weight (relevant for dependent claims)
Patent Landscape: How This Claim Set Typically Sits in the Field
This patent is best understood as a method-of-use and dye application constraint patent: it targets the staining selectivity problem in membrane peeling surgery. In US practice, the landscape around this topic typically clusters into four overlapping groups:
- Dye selection and staining agents (vitreoretinal dyes used for visualization)
- Formulation and delivery (concentration, carrier solution, application dwell time, wash steps)
- Target selectivity (stain target membrane vs ILM/underlying retina)
- Surgical workflows (peeling approach and step sequencing)
US 6,696,430’s distinctive hook is selectivity expressed as an ILM staining exclusion paired with a diffusion control limitation and enumerated dyes.
Likely competitors and design-around approaches (by mechanism)
Below are the most common ways later developers attempt to avoid this exact claim logic:
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Shift staining selectivity
If ILM staining occurs but is used intentionally for ILM peeling, it can negate the “without substantially staining ILM” requirement.
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Change dye class or formulation
If a dye system is argued not to be a “vital dye” or does not meet the stated concentration/salt ranges, dependent claims can be escaped.
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Change delivery mode
A protocol that relies on different application geometry or dwell time to drive staining into deeper layers can fall outside the diffusion requirement in Claim 5.
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Change the endpoint
If the method does not “remove the stained retinal disorder membrane” as a step, it can fall outside the claimed combination even if staining occurs.
Practical Claim Construction Drivers for Litigation and Prosecution
“Vital dye”
Because Claim 6 lists specific dyes, “vital dye” disputes often center on whether the agent is used as a live-tissue compatible stain intended for intraocular visualization rather than a fixation/chemical agent. Any accused product that is framed as a biocompatible intraoperative stain will argue stronger alignment.
“Substantially staining”
The claim uses “substantially” twice in functional context:
- must not substantially stain ILM
- must not substantially stain retinal layers underlying ILM
Expect technical disputes to turn on:
- imaging evidence (fluorescence/intensity comparisons)
- whether ILM signal is measured and normalized relative to target membrane staining
- whether diffusion into deeper layers occurs in a physiologically meaningful way
Relative comparison: “compared to”
Claim 1 requires an internal comparison: ILM/underlying layers must be substantially less stained than the stained retinal disorder membrane. This supports arguments framed around signal ratio rather than binary absence/presence.
Business Use: How to Map the Patent to Your R&D and Diligence
Red-flag elements when assessing a planned protocol
- Dye is one of: trypan blue, trypan red, brilliant crysyl blue, indocyanine green (Claim 6)
- Dye concentration is within 0.01% to 3% by weight (Claim 7)
- Carrier is a physiologically compatible salt solution with 0.8% to 1.0% salt (Claim 8)
- The method aims to visualize target membrane without staining ILM (the exact exclusion of Claim 1)
Evidence you need for a defensible position
While not altering the claim text, the litigation-ready focus items that determine outcomes are:
- staining distribution: target vs ILM vs deeper layers
- imaging-based ratios or thresholds supporting “substantially”
- whether diffusion is demonstrably limited (“without substantially diffusing”)
Key Takeaways
- US 6,696,430 claims a surgical method that removes a stained retinal disorder membrane while avoiding substantial staining of the ILM and underlying retinal layers relative to target staining.
- The patent’s strongest literal hook is dye selectivity plus explicit excluded structures (ILM and underlying layers) and step sequencing (apply vital dye during surgery, then remove stained membrane).
- Dependent claims narrow to PVR membranes and epiretinal membranes, and add tight constraints on dye behavior (no substantial diffusion) and dye chemistry and formulation (named dyes; 0.01% to 3% dye; salt 0.8% to 1.0% and specific salt anions/cations).
FAQs
1) Does Claim 1 cover any retinal membrane or only epiretinal/PVR membranes?
Claim 1 covers a generic “retinal disorder membrane” on the inner retina. Dependent claims explicitly cover PVR (Claim 2) and epiretinal membrane (Claim 3), but Claim 1 is not limited to those two types.
2) What is the main technical “escape” from this patent?
The central escape is to produce staining where the ILM or underlying layers are substantially stained relative to the target membrane, or to avoid the required method combination of staining and removing the stained membrane.
3) Are the listed dyes the only dyes covered?
They are explicitly listed in dependent Claim 6. Claim 1 requires a “vital dye,” so other vital dyes could still raise Claim 1 risk, but Claim 6 offers a clear literal anchor for the enumerated agents.
4) Do formulation limits matter only for dependent claims?
Yes. The concentration and salt-range limitations appear in dependent Claims 7-9, but they can still be relevant to overall claim mapping because the staining outcome and diffusion constraint in Claim 1 depends heavily on formulation.
5) How does the “compared to” language affect infringement analysis?
It frames the exclusion as relative staining: ILM/underlying layers must be substantially less stained than the retinal disorder membrane. This supports arguments based on comparative signal intensity.
References
[1] United States Patent No. 6,696,430, “Method of removing retinal disorder membrane” (claims 1-9).
