United States Patent 7,947,295: Scope, Claims, and US Ophthalmic Viscosity Landscape

What does US 7,947,295 claim cover?

US Patent 7,947,295 covers ophthalmic (eye) aqueous compositions that use two-polymer viscosity systems with measured “synergy”. The claims are not limited to lubricating drops. They extend to drug-containing ophthalmic formulations, including anti-infectives, anti-glaucoma agents, anti-inflammatory agents, anti-angiogenic agents, immunosuppressants, growth factors, and anti-allergy agents.

The scope is driven by four technical/legal elements:

Two specific polymer pair options (only three pairings)
Concentration window for the total of the two polymers
A synergy requirement for viscosity vs. simple additive behavior
A formulation exclusion tied to one polymer family (carboxyvinyl polymer)
- If the composition contains a carboxyvinyl polymer, it must not contain sodium chloride or boric acid.

What are the independent claim limitations (Claim 1 and Claim 10)?

Claim 1 (polymer-only version)

An aqueous composition suitable for ophthalmic administration comprising:

A viscosity-enhancing amount of a combination of two polymers having a synergistic effect on viscosity
The two-polymer combination must be one of:
1. Hydroxypropyl methylcellulose (HPMC) + guar gum
2. Carboxyvinyl polymer + guar gum
3. Hyaluronic acid + guar gum
Total polymer concentration: 0.05% to 3.0% (w/w)
Synergy test: viscosity is >150% of the simple sum of viscosity from single-polymer solutions

Exclusion tied to carboxyvinyl polymer

If composition comprises carboxyvinyl polymer, then composition does not contain sodium chloride or boric acid.

Claim 10 (drug-containing version)

An aqueous ophthalmic composition comprising:

An ophthalmic drug
A viscosity-enhancing two-polymer synergistic combination, selected from the same three pairings
Total polymer concentration: 0.2% to 2.0% (w/w)
Synergy test: viscosity >150% of simple sum of two single-polymer solutions
Same carboxyvinyl exclusion (via Claim 11, depending on dependent path)

Claim 10 is the “bridge” from the polymer system into therapeutic drug formulations.

How narrow is the polymer claim construction?

The independent claims constrain both identity and pairing:

The only acceptable guar partner is guar gum (and dependent claim 5 identifies a specific guar identity: hydroxypropyl guar).
The non-guar partner is restricted to:
- HPMC (dependent claim 5 adds an example grade: ~86,000 Da),
- a carboxyvinyl polymer (dependent claim 5 specifies an acrylic-acid crosslinked material),
- or hyaluronic acid (dependent claim 5 specifies sodium hyaluronate).

This produces a three-by-two architecture in practice: the claim is “two polymers only,” and the combinations are capped to three.

What does “synergistic viscosity” mean in legal terms here?

The claims use a bright-line benchmark:

Viscosity of the two-polymer formulation must be >150% of the simple sum of viscosity contributions from the corresponding single polymer solutions.

So a competitor cannot satisfy the claim merely by using a mixed-viscosity system that increases viscosity. The system must demonstrate more-than-additive viscosity.

Practical consequence: litigation and patent enforcement will likely hinge on:

the specific viscosity measurement method used in the patent,
formulation preparation conditions,
polymer grade and concentration,
and whether “simple sum” is properly constructed as the baseline.

What formulations are excluded if carboxyvinyl polymer is used?

The claims introduce an explicit exclusion (Claim 1 and Claim 11 path):

If the formulation contains a carboxyvinyl polymer, it must not contain:
- sodium chloride
- boric acid

This is a meaningful narrowing element because many ophthalmic formulations rely on NaCl for tonicity and borate buffers for pH control.

What do the dependent claims add (scope expansion vs. tightening)?

Below is a claim-by-claim map of what the dependent claims do.

Polymer-pair specificity (dependent claims 2-5, 12-15)

Claim 2: HPMC + guar gum (explicit pair)
Claim 3: carboxyvinyl polymer + guar gum
Claim 4: hyaluronic acid + guar gum
Claim 5: specifies example polymer identities and molecular specs:
- carboxyvinyl polymer: polymer of acrylic acid crosslinked with allyl sucrose or allylpentaerythritol
- HPMC: number average molecular weight ~86,000 Da
- guar gum: hydroxypropyl guar
- hyaluronic acid: sodium hyaluronate

The dependent specificity in Claim 5 matters because it pins a particular embodiment. But Claims 1 and 10 already cover the broader polymer pair categories without requiring those exact grades unless asserted through dependent claim scope.

Concentration tightening (Claim 6)

Total two-polymer concentration: 0.2% to 2.0% (w/w) (Claim 6), which aligns with the independent drug formulation range (Claim 10).

Optional formulation ingredients (Claim 7, Claim 16, Claim 18)

These claims allow typical ophthalmic excipient classes:

buffering agents
preservatives
tonicity-adjusting agents
surfactants
solubilizers
stabilizers
comfort-enhancing agents
emollients
pH-adjusting agents
lubricants

This language is broad and typically helps enforceability by not requiring a particular excipient set. It also means avoiding the patent likely requires altering the polymer pairing and/or synergy design, not just swapping preservatives.

Drug class inclusion (Claim 8-9, Claim 17, Claim 18)

The drug-dependent claims list broad therapeutic categories:

anti-glaucoma agents
anti-angiogenesis agents
anti-infective agents
non-steroidal and steroidal anti-inflammatory agents
growth factors
immunosuppressant agents
anti-allergic agents

These categories are wide enough to cover many modern ophthalmic programs.

Additional formulation parameters (Claim 18)

Claim 18 further specifies:

selected ophthalmic drug categories (same list)
preservative present
two-polymer system as above
total polymer concentration 0.2% to 2.0%
viscosity synergy >150% simple sum
pH 6-8
“suitable for topical administration” (additional generality)

This claim is an embodiment that can narrow enforcement to formulations in that pH window, but it does not limit Claim 10 unless an asserted theory depends on Claim 18.

Claims 19-20

Duplicate dependent claims focusing on carboxyvinyl polymer + guar gum in the Claim 18 framework.

How does this patent sit in the US ophthalmic viscosity patent landscape?

Core design pattern: viscosity synergy using guar as a second polymer

The most enforceable claim feature is not merely “two polymers in ophthalmic drops.” It is the requirement for >150% of additive viscosity using one of three polymer pair combinations that all involve guar gum as a partner.

This creates a recognizable landscape node:

Many ophthalmic viscosifiers use HPMC or hyaluronates.
Guar derivatives appear in lubrication and gel-like formulations.
Fewer patents (in typical portfolios) set a quantitative synergy threshold tied to “simple sum” across single-polymer controls.

So the patent is best treated as a claim over a specific viscosity-performance relationship rather than over polymer mixing generally.

Risk categories for competitor formulations

A competitor faces three independent “escape levers” from a literal infringement standpoint:

Use different polymer pairs (not one of the three listed)
Keep guar out (guar gum is embedded in every acceptable pairing)
Fail the synergy requirement (formulate where combined viscosity is 150% or less of simple sum)
If using carboxyvinyl polymer, include NaCl or boric acid (but this is not always feasible if the formulation’s tonicity and buffer are mandated)
- Note: this does not help if the competitor stays outside the carboxyvinyl route entirely.

Likely infringement attack surfaces

If a product is marketed in a way that maps onto the claim, enforcement or licensing pressure will likely focus on:

polymer identities and grades (HPMC molecular weight, specific carboxyvinyl crosslinking, sodium hyaluronate)
total concentration ranges (0.05-3.0% or 0.2-2.0%)
viscosity measurement results demonstrating the “>150% simple sum” threshold

Claim scope matrix (what’s covered vs. likely not)

Permitted polymer pairings

Polymer combination (two polymer system)	Included in Claim 1 and Claim 10?	Key dependent specifics
HPMC + guar gum	Yes	Claim 2; Claim 5 gives example HPMC ~86,000 Da
Carboxyvinyl polymer + guar gum	Yes	Claim 3; Claim 5 specifies acrylic acid crosslinked polymer
Hyaluronic acid + guar gum	Yes	Claim 4; Claim 5 specifies sodium hyaluronate

Concentration ranges

Claim scope	Total two-polymer concentration
Claim 1 (polymer-only)	0.05% to 3.0% (w/w)
Claim 6 / Claim 10 onward	0.2% to 2.0% (w/w)
Claim 18	0.2% to 2.0% (w/w) and pH 6-8

Synergy threshold

Requirement	Threshold
“synergistic effect” on viscosity	viscosity >150% of simple sum of viscosities from single polymer solutions

Carboxyvinyl exclusion

Condition	Excluded components
If carboxyvinyl polymer is present	sodium chloride and boric acid

How to interpret dependent claim strategy for enforcement

The dependent claims create multiple “entry points” into a product claim chart:

Generic two-polymer system entry point: Claim 1 or Claim 10
Concentration and pH entry point: Claim 6 and Claim 18
Carboxyvinyl formulation exclusion entry point: Claim 11 (to tighten arguments against NaCl/borate-containing products)
Product-specific polymer identity entry point: Claim 5 (and similar embodiment constraints via the dependent chain)

This structure supports enforcement by matching a product progressively:

If the product’s polymer grades are unknown or disputed, the broad claims (1/10) can still target the pairing and synergy.
If polymer grades are confirmed in discovery, Claim 5 increases precision.

What is the practical business takeaway for ophthalmic R&D?

The patent is a performance claim anchored to a quantified synergy benchmark, not only a formulation recipe.
The polymer selection is tightly enumerated: only three two-polymer pairings are within the literal scope.
The carboxyvinyl exclusion (no sodium chloride, no boric acid) is a notable constraint that can affect buffering and tonicity strategies.
Drug inclusion is broad. If an ophthalmic drug formulation uses one of the three polymer pairings at the relevant concentration and meets the synergy threshold, it can fall within scope.

Key Takeaways

US 7,947,295 claims ophthalmic aqueous formulations where two polymers act with measured viscosity synergy: >150% of the simple sum of single-polymer viscosities.
Only three two-polymer combinations qualify: HPMC + guar gum, carboxyvinyl polymer + guar gum, and hyaluronic acid + guar gum.
The total polymer concentration is 0.05-3.0% (Claim 1) and 0.2-2.0% (Claim 10 and related dependents).
If a carboxyvinyl polymer is used, the formulation must exclude sodium chloride and boric acid.
The claims cover both polymer-only compositions and drug-containing ophthalmic products across major therapeutic categories.

FAQs

1. Does the patent require an ophthalmic drug?
No. Claim 1 covers a polymer system without an ophthalmic drug. Claim 10 adds drug-containing embodiments.

2. What polymer is common to all three covered combinations?
Guar gum appears in every permitted two-polymer pairing.

3. What is the quantitative definition of “synergy” in the claims?
Viscosity must be greater than 150% of the simple sum of the viscosities of corresponding single-polymer solutions.

4. What happens if the formulation uses a carboxyvinyl polymer?
It cannot contain sodium chloride or boric acid.

5. Are the covered drugs limited to a specific mechanism?
No. The dependent claims list broad categories including anti-glaucoma, anti-infective, anti-inflammatory (steroidal and non-steroidal), anti-angiogenesis, growth factors, immunosuppressants, and anti-allergic agents.

References

United States Patent 7,947,295. (Claims 1-20 provided in user prompt text).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2004249137	⤷ Start Trial
Australia	2010200297	⤷ Start Trial
Australia	2012205283	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,947,295

Summary for Patent: 7,947,295