Petitioner: Haag-Streit AG
`Petitioner: Haag-Streit AG
`
`Ex. 100(cid:26)
`
`EX. 1007
`
`

`

`United States Patent
`
`[19]
`
`4,518,579
`[11] Patent Number:
`Holly
`[45] Date of Patent: May 21, 1985
`
`
`51,
`
`1973, pp.
`
`v01.
`
`31,
`
`1959, pp.
`
`OTHER PUBLICATIONS
`Refojo et 21]., J. Amer. Optometric Asso., vol. 43, NO. 3,
`Mar. 1972, pp. 321—326.
`Refojo et 21]., Arch Ophtha1., vol. 87, Mar. 1972, pp
`275—277.
`Norm, Acta Ophthalmologica, vol.
`670—678.
`Hoelzl Wallach, Anal. Chem,
`456-460-
`Primary Examiner—Sam Rosen
`ASSI'SIGMZ Examiner—K‘ S. Moss
`Attorney, Agent, or Firm—~Robert L. Goldberg
`[57]
`ABSTRACT
`An ophthalmic composmon for use in the human eye
`comprlsmg an aqueous solution of fluorexon whose pH
`has been adjusted to between pH 5.4 and 6.2 to deliver
`maximum fluorescence and additionally containing suf-
`ficient buffer to maintain that pH even after instillation
`into the eye.
`
`[54] PH STABILIZED FLUORESCING
`OPHTHALMIC COMPOSITION
`CONTAINING FLUOREXON
`.
`Inventor.
`[75]
`Frank J' Holly, LUbeCk’ Tex.
`[73] Assignee: Holles Laboratories, Cohasset, Mass.
`2
`.
`l
`..
`.
`[ 1] App] No
`7 ,738
`[22] Flled:
`Aug. 31, 1979
`[51]
`Int. C13 ..................... G01N 31/00; GOlN 33/43;
`AOIN 43/90
`[52] U.S. Cl. ......................................... 424/9; 424/7.1;
`436/172
`........................ 424 7.1, 8, 9, 253;
`/
`436/172
`
`'
`[58] Field of Search
`[56]
`References Cited
`
`U.S. PATENT DOCUMENTS
`3,306,820
`2/1967 Krezanoski ............................. 424/7
`3,374.144
`3/1968 Stolar ................................... 424/7.1
`FOREIGN PATENT DOCUMENTS
`
`858019
`
`1/1961 United Kingdom .................... 424/3
`
`10 Claims, No Drawings
`
`

`

`PH STABILIZED FLUORESCING OPHTHALMIC
`COMPOSITION CONTAINING FLUOREXON
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`This invention relates to an ophthalmic compositions
`for use as a fitting or diagnostic aid, particularly for use
`with hydrogel contact lens.
`2. Description of the Prior Art
`It is well known in the prior art to use sodium fluores-
`cein, commonly referred to simply as fluorescein, to
`evaluate the fit of contact lens and to evaluate the tear
`film and cornea prior to and following contact lens
`wear. Fluorescein is considered by most authorities to
`be an essential tool in making these evaluations. Desic-
`cation, dry spots, epithelial defects, and certain other
`irregularities are difficult,
`if not impossible, to detect
`without the use of fluorescein.
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`Because of its absorption by hydrogel contact lens
`and its staining the lens, fluorescein can not be used for
`evaluating the fit of the hydrogel lens and, if it has been
`instilled for evaluation of the tear film and cornea, a
`certain amount of time must be allowed to elapse before
`a hydrogel lens can be inserted.
`A one hour wait after using fluorescein is commonly
`recommended before such an insertion is made. This
`delay of an hour prior to hydrogel lens insertion is se-
`verely limiting to the practitioner and may not allow
`the use of fluorescein. Also, there is no direct way of 30
`evaluating the corneal-lens relationship as there is for
`hard lens with fluorescein. The need for a substitute
`fluorescein dye for use with hydrogel lens was appar-
`ent.
`
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`
`To overcome this problem, a new fluorescent water-
`soluble dye, fluorexon, was adopted for use with hydro-
`gel lens.
`Hydrophilic soft contact lens are made of polymers
`having a strong affinity for water. The polymeric mac-
`romolecules are interconnected by crosslinks forming
`3-dimensional networks. The crosslinks render the pol-
`ymer insoluble in all solvents. However, network poly-
`mers swell in good solvents, forming gels. When the
`swelling solvent is water, the material is termed a hy-
`drogel. Hydrophilic soft lens are often referred to as
`hydrogel lens.
`Hydrogel contact lens absorb aqueous solutions until
`swelling equilibrium is reached. The degree of swelling
`depends, for each given type of hydrogel contact lens,
`on its chemical composition, the degree of crosslinking,
`and on the compositon of the bathing solution.
`Hydrogel lens consist of a polymer matrix containing
`interconnecting interstices of the network which are
`filled with an aqueous solution. The interconnecting
`interstices of the network are open to the surface of the
`lens, and it is proper to say that hydrogel lens are po-
`rous. Ions and molecules of dimensions smaller than the
`“pores” in the lens are easily absorbed into the lens.
`Through the pore size of the typical hydrogel lens,
`fluorescein can readily be absorbed. However, it was
`found that fluorexon was of larger dimensions and as
`such much less could be absorbed resulting in only
`negligible staining allowing its use with hydrogel lens
`without the accompanving disadvantages of transpar-
`ency changes due to staining. The use of compounds
`such as fluorexon and fluorescein in these applications
`depends upon their ability to absorb light at characteris-
`tic wave lengths, which peaks for fluorescein at 490 nm
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`and for fluorexon at 494 nm, and they emit light at
`longer wave lengths, which peaks in the case of fluores-
`cein at 520 nm and fluorexon at 524 nm. A disadvantage
`in the prior art has been that a fluorescein solution
`0.25% by weight
`in normal saline excited at wave
`length 490 nm, fluoresces twice as much as fluorexon of
`the same concentration. Because the molecular weight
`offiuorexon (710) is almost twice as large as the molecu—
`lar weight of fluorescein sodium (376), at
`the same
`weight percent concentration, almost twice as many
`molecules of fluorescein as fluorexon will be present in
`equal volume of both solutions. But, even in solutions of
`the same molar concentration, 0.47% by weight fluo-
`rexon and 0.25% by weight fluorescein,
`the fluores—
`cence of fluorexon is still about 50% lower than the
`fluorescence of fluorescein. This happens because, at
`these relatively high levels of concentration,
`fluores—
`cence does not increase linearly with increasing concen—
`tration. In other words, it is impossible to increase the
`concentration of fluorexon to a level where its degree of
`fluorescenceequals that of a 0.25% by weight solution
`of fluorescein.
`
`Accordingly, while fluorexon which stains hydrogel
`lens slowly and gradually and is easily reversible,
`is
`preferred over fluorescein which stains hydrogel lens
`easily and intensively, the lower fluorescene of fluo-
`rexon has been one of the reasons for its limited adopt
`tion by practitioners in the art. Thus, a need exists for a
`means of increasing the relative fluorescence of fluo—
`rexon and maintaining that increased level of fluores-
`cence even after its addition to the eye. As stated above,
`merely increasing the concentration of fluorexon is not
`a complete answer since the fluorescence does not in—
`crease linearly, fluorexon has only limited solubility in
`water, and because it is desirable to reduce the concen—
`tration of materials put into the eye due to the potential
`for irritation.
`
`SUMMARY OF THE INVENTION
`
`The present invention comprises an aqueous solution
`of fluorexon which has been pH adjusted to deliver
`maximum fluorescence and additionally contains a
`buffer to maintain that pH even after instillation into the
`eye.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The fluorescing material of the present invention is
`bis(N,N—bis(carboxymethyl)-aminoethyl)-fluorescein
`tetrasodium salt (fluorexon). Fluorexon has been used in
`the past as an indicator in the laboratory titration of
`calcium. It is commercially available as a yellow pow-
`der. While it is possible to use the fluorexon as it is
`obtained from the supplier, it is preferred that various ’
`contaminants be removed from the fluorexon by adding
`the crystalline fluorexon to ethyl alcohol at a ratio of
`about 1:20, stirring for several minutes and then filtering
`through a Whatman 2V filter which results in the puri-
`fied fluorexon crystals being retained by the filter paper
`with the contaminants being carried away by the ethyl
`alcohol.
`The fluorexon is dissolved in water at a concentration
`by weight of between about 0.01% and about 2.0%,
`preferably between about 0.35% and about 0.60%. In
`contrast to the prior art, where concentrations of 0.6%
`and greater were required due to the lesser relative
`fluorescence of fluorexon as compared to sodium fluo-
`
`

`

`3
`rescein, it has been found that by varying the pH it is
`possible to increase the relative fluorescence of fluo-
`rexon. Accordingly, by varying the pH it is possible to
`decrease the concentration of fluorexon in the composi-
`tion while maintaining a suitable level of fluorescence.
`The pH of the composition is preferably adjusted to
`obtain the maximum fluorescence. While this pH is
`more acidic than that of the tearfilm covering the
`preocular surface, it is still less acidic than that of the
`skin surface and has been found to be tolerated well in
`the eye. It is preferred that the pH be adjusted to be—
`tween about 5.4 and 6.2, preferably between about 5.8
`and about 6.0, most preferably 5.9. The pH of the solu-
`tion may be adjusted by adding one or more of the acids
`or bases known for use in ophthalmic solutions. An
`aqueous solution of fluorexon is acidic requiring the
`addition of a base, a preferred base being sodium hy-
`droxide.
`Since the pH of the tearfilm coveringthe preocular
`surface of the human eye differs from that of a solution
`of fluorexon which has been adjusted for maximum
`fluorescence such that dilution by the tears in the eye
`will change the pH of the composition somewhat, the
`composition should be buffered to maintain the desired
`pH and therebymaintain the maximum amount of fluo-
`rescence. Any of the buffers previously used in ophthal-
`mic preparations are suitable for the present invention
`including phosphates, acetates, carbonates, and citrates
`provided the combinations are compatible with the eye.
`For the preferred range of pH between 5.8 and 6.0, the
`preferred buffer is phosphate, Le. a mixture of monoba-
`sic and dibasic phosphate salts, ranging in molar ratio
`between about 13.9:1 and about 8.921, at a total phos-
`phate molarity of about 0.1. Such a concentrated buffer
`is nearly isotonic. The total phosphate concentration in
`the buffer could range from this maximum molarity of
`about 0.1M to about 0.005M, with a concurrent change
`in the ratio of monobasic to dibasic phosphate being
`needed in order to correct for the pH shift that occurs
`upon dilution. At this twenty-fold dilution, the buffer
`capacity of the phosphate solution is still somewhat
`greater than that of the tears. However, at this low
`concentration, the osmolality of the buffer is negligibly
`small.
`If pH values lower than 5.7 are desired, then a mix-
`ture of sodium acetate and acetic acid is the preferred
`buffer. At pH 5.4, the molar ratio of salt to acid is 4.8:1
`at a total acetate concentration of 0. 1 8M, which is about
`isotonic. The method of preparation of various other
`buffers suitable forophthalmic formulations is well
`known to those skilled in the art.
`It is preferred that the ophthalmic solution of the
`present invention be isotonic. Since the salts used to
`prepare the buffer are usually present at
`insufficient
`levels to render the solution isotonic, any of the salts
`described as useful in the prior art for rendering an
`ophthalmic solution isotonic may be used in the present
`invention to increase osmolality to isotonic levels, such
`as, for example, sodium chloride, potassium chloride,
`calcium chloride, magnesium chloride, and various
`sulfates, phosphates, borates, nitrates, citrates, acetates,
`etc.
`
`If desired, it is also possible to add a preservative to
`the ophthalmic solution used in the present invention.
`For example, biocides such as benzalkonium chloride,
`thimerosal,
`phenylmercuric
`nitrate,
`chlorobutanol,
`methyl paraben, propyl paraben, chlorhexidine diglu-
`conate, and sorbic acid and chelating agents, such as,
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`tri, or tetrasodium ethylene diamine
`for example, di,
`tetraacetate, also known as edetates, may be added at
`concentrations between about 0.001% and 1.0% by
`weight.
`In addition, the composition of the present invention
`can also contain as an optional ingredient an eye com-
`patible anesthetic such as, for example, benoxinate,
`buty1-4-aminobenzoate, naepaine, and phenacaine. A
`preferred anesthetic is proparacaine. The following
`example is given by way of illustration only and is not to
`be considered as limiting the scope of the invention.
`EXAMPLE I
`
`25 grams of fluorexon crystals (Aldrich Chemicals)
`were added to 500 milliliters of absolute ethanol. The
`solution was stirred for 60 minutes, after which time the
`undissolved fluorexon crystals were recovered by
`straining the solution through a Whatman 2V filter. The
`crystals were removed from the filter paper and al-
`lowed to dry.
`To 5 liters of deionized water were added 17.50
`grams of purified fluorexon. To this was added 39.75
`grams of potassium phosphate monobasic and 5.80
`grams of sodium phosphate dibasic. Next, 2050 grams
`of sodiumchloride were added to make the composition
`isotonic. At
`this point
`the pH of the solution was
`checked with the pH meter and was determined to be
`between 3.8 and 3.9. To the composition was added a
`sufficient amount of l N sodium hydroxide to bring the
`pH up to the desired value.
`The fluorescence of the resulting solution is measured
`by a fluorophotometer system, which consists of a dis-
`secting microscope, a photomultiplier tube, an Amicon
`photomultiplier photometer, and a light source. The
`fluorescence is measured by pipetting an aliquot of
`solution into a polyethylene trough of exact dimensions,
`which is placed on a black support in the visual field of
`the microscope and is illuminated with blue light at the
`excitation wave length of fluorexon, 494 my. by means
`of a flberoptic cable connecting a Dyonics light source
`to the left eyepiece of the microscope. The light re-
`flected from the trough is picked up by a fiberoptical
`probe placed in the right eyepiece of the microscope,
`passed through a filter, so that only the emission wave
`length of fluorexon, 524 mu is allowed through. This
`light is then conducted through a fiberoptic cable to the
`photomultiplier tube, which amplifies the signal elec—
`tronically. The signal is measured by the photomulti-
`plier photometer. The focusing is adjusted until maxi—
`mum light intensity is measured for the sample. The
`measurements are made in a dark room, the only illumi-
`nation coming from a red lamp,
`to obtain maximum
`sensitivity.
`Table I below illustrates the pH dependence of a
`0.35% fluorexon solution measured as described above,
`the pH having been adjusted to the appropriate value by
`adding 1N sodium hydroxide.
`TABLE I
`Relative Fluorescence
`pH
`13.2
`5.20
`14.7
`5.45
`15.3
`5.90
`14.8
`6.15
`13.8
`6.35
`12.9
`6.60
`1 1.7
`7.10
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`7.40 1 1.4
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`4,518,579
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`3. The ophthalmic solution of claim 1 in which said
`fluorexon is present in a concentration by weight of
`between about 0.0% and about 2.0% by weight.
`4. The ophthalmic solution of claim 1 in which said
`buffer is present
`in a concentration between about
`0.005M and about 0.1M.
`5. The ophthalmic solution of claim 1 in which said
`buffer is a combination of potassium phosphate monoba-
`sic and sodium phosphate dibasic.
`6. The ophthalmic solution of claim 1 in which said
`ophthalmic solution comprises, in addition, an eye com-
`patible anesthetic.
`7. The ophthalmic solution of claim 6 in which said
`anesthetic is proparacaime.
`8. The ophthalmic solution of claim 1 in which said
`ophthalmic solution comprises, in addition, one or more
`cationic salts at a level sufficient to provide an isotonic
`solution.
`
`9. An ophthalmic solution for use in a human eye
`comprising an aqueous solution containing about 0.35%
`by weight fluorexon, the solution having a pH of be-
`tween about 5.8 and about 6.0, and the solution contain-
`ing about 1% by weight of a combination of potassium
`phosphate monobasic and sodium phosphate dibasic in a
`ratio of about 6:1.
`
`10. A method of fitting hydrogel contact lens in a
`human eye comprising instilling an aqueous solution of
`fluorexon the solution having a pH between about 5.4
`and about 6.2, and sufficient eye compatible buffer to
`maintain said pH after said solution is instilled into the
`eye, and examining said eye and lens with a light of an
`appropriate wavelength.
`*
`*
`II:
`*
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`5
`While the table shows the relative fluorescence for a
`
`solution of 0.35%, corresponding increases will be seen
`regardless of the relative concentration of fluorexon in
`the composition.
`The prepared solution can be used for fitting contact
`lens by placing a drop of the fluorexon solution on the
`concave, inner surface of the lens and then placing the
`lens on the eye. The fluorescent tearfilm can be readily
`observed between the lens and the cornea. Observation
`
`is best made with a strong black light source and the
`naked eye or loupe rather than with the biomicroscope
`since it is desirable to make the initial observation prior
`to blinking. Other comparable procedures for use in
`fitting contact lens are well known in the prior art.
`Other embodiments of the invention will be apparent
`to those skilled in the art from a consideration of this
`
`specification or practice of the invention disclosed
`herein. It is intended that the specification and example
`be considered as exemplary only, with the true scope
`and spirit of the invention being indicated by the follow-
`ing claims.
`What is claimed is:
`
`1. An ophthalmic solution for use in a human eye
`comprising an aqueous solution of fluorexon, the solu-
`tion having a pH between about 5.4 and about 6.2, and
`sufficient eye compatible buffer to maintain said pH
`after said solution is instilled into the eye.
`2. The ophthalmic solution of claim 1 in which said
`pH is between about 5.8 and about 6.0.
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