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Patent landscape, scope, and claims: |
US 4,443,432: What Is Claimed in the Patent and Where It Sits in the Ocular Irrigation Landscape
US Patent 4,443,432 claims a two-part, prepackaged, sterilized irrigating solution for corneal stability during ocular surgery. The method is built around (1) maintaining bicarbonate/carbonate alkalinity in one component, (2) placing calcium/magnesium and glutathione-containing chemistry in a second acidic component, (3) ensuring compatibility after mixing while maintaining sterility, and (4) hitting narrow post-mix ranges for ionic strength, pH, osmolality, and glutathione oxidation state before use.
What Does Claim 1 Actually Require? (Independent Claim Breakdown)
Claim 1 is a tightly coupled sequence with compositional, manufacturing, sterility, and timing limits.
A. Two prepackaged, sterilized solutions
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Basic solution
- Contains bicarbonate ions
- Has sufficient sodium/potassium/chloride provisioning via ion selection (claim terms require sodium, potassium, chloride to be provided “in one of said solutions”; other dependent claims allocate them)
- Is stabilized as a basic solution (claim requires “stable basic solution containing bicarbonate ions”)
- Sterilized
- Prepackaged
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Acidic solution
- Contains calcium ions
- Contains magnesium ions
- Contains dextrose
- Contains glutathione (oxidized glutathione or equivalent amount of reduced glutathione)
- Is stable acidic solution
- Sterilized
- Prepackaged
B. Ionic “distribution” requirement after mixing
Claim 1 does not force whether sodium, potassium, chloride come from the basic vs acidic solution. It only requires they are provided in one of the solutions.
C. Sterility-preserving mixing and combined composition
- The prepackaged sterile solutions are mixed “in a manner which maintains their sterility.”
- The mixed combined solution must contain these ranges:
| Component |
Post-mix concentration requirement (claim 1) |
| Sodium ions (Na⁺) |
130 to 180 mM/L |
| Potassium ions (K⁺) |
3 to 10 mM/L |
| Calcium ions (Ca²⁺) |
1 to 5 mM/L |
| Magnesium ions (Mg²⁺) |
0.5 to 4 mM/L |
| Bicarbonate ions (HCO₃⁻) |
10 to 50 mM/L |
| Dextrose |
2 to 50 mM/L |
| Oxidized glutathione (or equivalent reduced) |
0.03 to 0.5 mM/L |
- The combined solution must satisfy physicochemical targets:
| Parameter |
Post-mix requirement (claim 1) |
| pH |
6.8 to 8.0 |
| Osmolality |
250 to 350 mOsm/kg |
D. Use timing constraint
- “Within about 24 hours of mixing said prepackaged solutions,” the eye is irrigated with the combined solution.
What Do Dependent Claims Add? (Scope Refinements)
The dependent claims lock down solution details: phosphate loading, ion assignment, specified salts, pH constraints per component, mixing ratio, and specific preparation order to control bicarbonate introduction pH.
Dependent claim map
| Claim |
Additional limitation(s) |
| 2 |
Phosphate ions in basic solution so combined phosphate is 1 to 5 mM/L |
| 3 |
Sodium ions provided in basic solution |
| 4 |
Potassium ions provided in basic solution |
| 5 |
Exemplary salt formulation: basic solution has NaCl, KCl, dibasic sodium phosphate, sodium bicarbonate; acidic solution has CaCl₂, MgCl₂, dextrose, oxidized glutathione |
| 6 |
Combined pH 7.2 to 7.8 |
| 7 |
Acidic solution pH below 5 |
| 8 |
Preparation order: phosphate dissolved before bicarbonate so bicarbonate is introduced at pH above 8 |
| 9 |
Volume ratio basic:acidic 10:1 to 40:1 |
| 10 |
Combined osmolality 290 to 320 mOsm/kg |
| 11 |
Combined pH 7.2 to 7.8 (duplicate of scope seen in claim 6) |
| 12 |
Sodium in basic solution (duplicate of claim 3) |
| 13 |
Potassium in basic solution (duplicate of claim 4) |
| 14 |
Combined pH 7.2 to 7.8 (duplicate of claim 6) |
| 15 |
Acidic solution pH below 5 (duplicate of claim 7) |
| 16 |
Preparation order phosphate before bicarbonate (duplicate of claim 8) |
| 17 |
Basic:acidic volume ratio 10:1 to 40:1 (duplicate of claim 9) |
Net effect on claim scope
- Claim 1 is broad across how Na⁺/K⁺/Cl⁻ are sourced, as long as the post-mix targets are met.
- Claims 3, 4, 5 narrow sourcing of key ions to the basic component and require specific salt exemplars.
- Claims 6, 7, 8, 9, 10 tighten process and formulation mechanics: component pH, order-of-addition, volume ratio, and osmolality window.
- The net “center of gravity” is a bicarbonate-containing alkaline component paired with a low-pH calcium/magnesium/glutathione/dextrose component, mixed to a near-physiologic pH with controlled osmolality.
Where the Novelty Likely Lives (Claim-structure logic)
Without relying on external narrative, the patent’s internal claim logic points to the technical differentiators:
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Two-component stability
- The method explicitly requires separate stable basic vs acidic solutions, implying that bicarbonate coexistence with Ca²⁺/Mg²⁺ and glutathione is managed by separation until mixing.
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Sterility and timed usability
- “Sterility preserved during mixing” plus “within about 24 hours” after mixing is a practical constraint that aligns with prepackaged ocular irrigation workflows.
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Combined target envelopes
- Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO₃⁻, dextrose, and oxidized (or equivalent reduced) glutathione are all simultaneously bounded.
- Post-mix pH (6.8 to 8.0) and osmolality (250 to 350 mOsm/kg) are also bounded.
-
Phosphate integration
- Dependent claim 2 ties phosphate to a 1 to 5 mM/L combined concentration.
-
Glutathione oxidation state inclusion
- Claim 1 specifies oxidized glutathione (or equivalent reduced glutathione). That is not typical of many classic buffered saline approaches, and it creates a composition-specific infringement handle (even if functional equivalents are argued, the claim text anchors to glutathione chemistry).
Patent Landscape: How US 4,443,432 Sits Relative to Standard Ocular Irrigation Formulas
The landscape analysis below is framed by claim scope mechanics: competitors or later formulations typically try to design around one or more of the claim’s binding constraints. In this area, the most common “moving parts” are: buffering system (bicarbonate vs phosphate vs HEPES), presence of divalent cations, presence of antioxidants (including glutathione), osmolality control, and whether the product is one-part vs multi-part.
1) One-part balanced salt solutions (BSS)
Typical profile
- Phosphate or bicarbonate buffers
- Na⁺ and Cl⁻ dominating
- Optional K⁺
- Ca²⁺/Mg²⁺ may be absent or low depending on product
- Antioxidants are not always glutathione-based
- Single-solution sterility
How US 4,443,432 differentiates
- Claim 1 demands two stable solutions (basic + acidic) and requires the combined solution to include Ca²⁺, Mg²⁺, dextrose, and oxidized glutathione at specified ranges.
- It also requires mixing of prepackaged sterile parts under sterility-preserving conditions.
Likely design-around
- Use a single compatible solution without the claimed two-component stability structure.
- Omit glutathione or substitute antioxidants not encompassed by “oxidized glutathione or equivalent amount of reduced glutathione.”
2) Electrolyte solutions with bicarbonate buffering
Typical profile
- Bicarbonate + Na⁺ (and sometimes K⁺)
- Often lacks specified glutathione dosing and/or dextrose
- Calcium/magnesium may be controlled or excluded to manage precipitation
How US 4,443,432 differentiates
- Claim 1 locks combined targets for both bicarbonate and divalent cations plus glutathione plus dextrose.
- It also locks pH and osmolality windows, and requires component pH management (acidic component below about 5 in dependent claims).
Likely design-around
- Keep bicarbonate but change the divalent cation profile (e.g., remove Ca²⁺/Mg²⁺ or keep them outside specified ranges).
- Replace glutathione with non-glutathione antioxidants.
3) Antioxidant-supplemented ocular irrigation
Typical profile
- Antioxidant addition to reduce oxidative stress during surgery
- May include glutathione or related thiols depending on product
- Buffer system varies
How US 4,443,432 differentiates
- It requires a very specific matrix: dextrose + Ca²⁺ + Mg²⁺ + buffered bicarbonate system with glutathione at specified ranges, all in a two-part preparation format with tight post-mix envelopes.
Likely design-around
- Use glutathione but not the claimed two-part “basic bicarbonate” + “acidic Ca/Mg/dextrose/glutathione” scheme.
- Match glutathione but not the combined Na⁺/K⁺/Ca²⁺/Mg²⁺/HCO₃⁻/dextrose ranges.
4) Pre-mixed vs “within 24 hours of mixing”
Typical profile
- Many commercial products are single-unit sterile and used immediately after opening.
- Some systems allow reconstitution timing windows.
How US 4,443,432 differentiates
- Claim 1 fixes a usage window: irrigation occurs “within about 24 hours of mixing.”
- If a later system provides a longer validated post-mix window or is designed as ready-to-use, it may fall outside the claim’s “within about 24 hours” requirement (depending on how “about” is construed).
Where Claim Scope Is Most Sensitive for Infringement Analysis
From a claim construction perspective, the most sensitive elements are the ones that are both quantitative and structural:
- Two-part structure
- “Preparing… stable basic solution… sterilizing… prepackaging” and similarly for acidic solution; and mixing while maintaining sterility.
- Post-mix numeric envelopes
- Na⁺ (130-180 mM/L), K⁺ (3-10 mM/L), Ca²⁺ (1-5 mM/L), Mg²⁺ (0.5-4 mM/L), HCO₃⁻ (10-50 mM/L), dextrose (2-50 mM/L), oxidized glutathione (0.03-0.5 mM/L).
- Post-mix physicochemical targets
- pH 6.8-8.0; osmolality 250-350 mOsm/kg.
- Timing
- “Within about 24 hours of mixing.”
- Dependent tightening knobs
- If sodium/potassium are moved off the basic component (claims 3-4), if phosphate is outside 1-5 mM/L (claim 2), or if component pH and preparation order are altered (claims 7-9, 8, 16, 17), coverage narrows to the independent claim only.
Key Takeaways
- US 4,443,432 claims a two-component, sterilized, prepackaged ocular irrigating system (basic bicarbonate + acidic Ca/Mg/dextrose/glutathione) with sterility-preserving mixing and a post-mix composition defined by multiple numeric ranges.
- The patent’s infringement-relevant core is the simultaneous fulfillment of: (i) structure (two stable prepackaged solutions), (ii) composition (Na⁺/K⁺/Ca²⁺/Mg²⁺/HCO₃⁻/dextrose/glutathione ranges), (iii) pH/osmolality envelopes, and (iv) “within about 24 hours” use timing.
- Dependent claims further restrict phosphate loading, ion sourcing, exemplified salts, acidic component pH (<5), order-of-addition (phosphate before bicarbonate at pH >8), basic:acidic volume ratio (10:1 to 40:1), and tighter combined pH/osmolality windows.
FAQs
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Does US 4,443,432 require sodium and potassium to come from the basic solution?
Not in claim 1. Claims 3 and 4 specify sodium and potassium in the basic solution, but claim 1 only requires Na⁺/K⁺ to be present “in one of said solutions.”
-
Is the bicarbonate buffering system mandatory?
Yes. Claim 1 requires a stable basic solution containing bicarbonate ions and defines post-mix bicarbonate concentration.
-
What makes glutathione a coverage-sensitive element?
Claim 1 requires oxidized glutathione (or equivalent reduced glutathione) within 0.03 to 0.5 mM/L in the combined solution.
-
Is there a hard requirement on time after mixing?
Claim 1 requires irrigation within about 24 hours of mixing the prepackaged solutions.
-
Which parameters are most useful for design-around strategies?
The most levered variables in the claim text are the two-part stability/sterility-preserving mixing structure, the glutathione inclusion, and the multi-parameter numeric post-mix ranges for ions plus pH and osmolality.
References
[1] United States Patent No. 4,443,432.
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