Complicated Ulcers

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    Complicated Corneal UlcersMicrobial KeratitisJames V. Schoster, DVM DACVO

    University of Wisconsin USA

    Learning Objectives

    Recognize the signs of corneal infection

    Recognize the signs of corneal melting

    Understand the diagnostic and therapeutic options.

    IntroductionA corneal ulcer is an area of the cornea that has lost its epithelium and a variable amount ofstroma. Stromal ulcers take longer to heal than simple epithelial abrasions. Uncomplicatedstromal ulcers that were trauma induced should heal in one to two weeks; as apposed to superficialcorneal abrasions that should be healed in less than one week.

    DefinitionA complicated corneal ulcer is one that has additional factors present which are not only delayingthe normal healing response but have the potential to cause further deterioration of the cornea.hese factors can be intrinsic or ac!uired. Sepsis is the most common ac!uired reason which candirectly destroy the cornea as well as by stimulation of intrinsic "self destruct" mechanisms#collagenase$. %n addition& other complications of septic ulcers are uveitis and cataract.

    Epidemiology'ven though corneal ulceration is one of the most common ocular disorders in dogs; the incidenceof complicated corneal ulcers is not known but is felt to be significantly less than uncomplicatedcorneal ulcers.

    Etiology%n most cases the cause is corneal trauma& however considerations of foreign body& eyelidabnormalities& aberrant cilia& e(posure and )*S #keratocon+unctivitis sicca$& should be made.

    Normal Corneal Defense Mechanisms,ormally the cornea is flooded with microorganisms consisting of the normal flora. ,ormal cornealdefense mechanisms provide protection from these organisms.

    'yelids and intact blink refle(

    'yelashes

    Refle( tearing and trilaminar tear film

    ear proteins with antibacterial effects

    -icrobial products #bacteriocins$ from the normal flora that affect pathogenicmicroorganisms

    *orneal epithelial cells

    Smooth corneal surface

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    Impaired Corneal Defense MechanismsWhen any of the above normal protective mechanisms are not present or if they aremalfunctioning; there is increased risk for infection. %n addition& specific risk factors such astrauma& foreign body& corneal surgery and other local or systemic factors can impair the normalcorneal defenses. -icroorganisms may adhere to the corneal tissues more readily if there is

    damage to the tissue and or if the microorganisms are not swept from the surface of the corneaefficiently by the normal blink& and tear film mechanics and physiology.Systemic factors such as senility& *ushings disease& diabetes mellitus& and any other local orsystemic disease or medication can impair the immune system.

    Clinical eatureshe evaluation of an animal with a stromal keratitis should include a careful history ande(amination of the corneal ulcer for signs of infection as well as the entire anterior segment to lookfor predisposing factors.-ost often the history is one of an initial acute onset of ocular discomfort& blepharospasms& tearingand rubbing at the eye.

    '(amination findings that would imply a complicated stromal ulcer and possibly a microbialkeratitis/

    *orneal ulcer present longer than one week with stromal loss

    0rogressive stromal loss

    %nfiltrate

    ,eovascularization 1 perilimbal flush

    Anterior uveitis

    Soft borders

    -alacia #melting$ 2 li!uifactive stromal necrolysis

    Small ulcer #pin point or dot$& minimal to no apparent stromal loss& acute onset withsignificant anterior uveitis #miotic pupil and a!ueous flare and pain$

    3ypopyon *orneal edema

    Sterile complicated stromal ulcerations are fre!uently encountered and usually do not haveinfiltrates or hypopyon; however they may be malacic and have secondary uveitis.

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    our !teps or !uccess "hen dealing#ith Complicated !tromal Ulcers

    !$E% &

    'ttempt to determine the cause for the stromal ulcer and inspect the anteriorsegmentOphthalmic Examination#'specially take note of the following points$

    - 4ocation of ulcer- A(ial- 0ara(ial- %nferior nasal- %nferior temporal- 0erilimbal

    -Size- of the lesion is important especially from a prognostic standpoint.

    - Shape of the lesion is important to note prognostically in that as the lesionheals one can identify the change in shape with healing& which is usually in theform of tongues or waves of epithelium moving toward the center.- he shapemay also infer or corroborate the etiology; e.g.& scratch would

    be linear or out line the path of a foreign body attached to the underside ofthe eyelid and the path or track it makes in the cornea as the eyelidmoves.

    - 0alpebral Refle(- 5lobe size and position

    -Schirmer ear est #6o not perform if 6escemetocele$

    - 'yelids #conformation& aberrant cilia$- 7oreign body search- 'valuation for uveitis- %ntraocular pressure measurement #do not perform if ulcer is very deep and

    there is impending rupture$- %s this ulcer infected8

    - %nfiltrates- %ndistinct borders- 5rey to yellow color

    - %s a foreign body present8

    -'vert all eyelids and e(amine the con+unctival surfaces and forni( withmagnification and good light

    - What is the depth of the ulcer8 #Amount of stroma remaining at its deepestpoint$

    - What is the breadth of the ulcer8- Are there other complications/ Uveitis& *ataract& 5laucoma

    Essential E(aminationE)uipment

    4oupes 7ocal 4ight Source Slit 4ight Source Schirmer ear est

    Strips 6elicate 9 ( : rat

    toothed forceps -uscle hook

    onometer #do notmeasure %0 ifthere is a deepcorneal ulcer$.

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    !$E% *

    Laboratory Evaluations

    - -icrobiological 'valuation-

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    !$E% ,I $-E DE%$- O $-E CO.NE'L ULCE. I!

    4ess than 9: the thickness of the normalcornea

    MEDIC'L!

    5reater than :> rds the normal cornealthickness

    !U./IC'L!

    opical herapy6rug *hoice- Antimicrobial- Antiinflammatory- -ydriatic 1 cycloplegic

    0reparation 7ormA!ueous solutionSuspension'mulsion5elintment

    *ollagen Shield7ortified drops6elivery

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    MEDIC'L $-E.'%0 !%ECIIC!

    ypically infected #septic$ corneal ulcers can have either cocci or rods& or both; septic ulcers areusually of an aerobic variety. ml of Artificialears to make concentration of >> mgml. 6o not use ears ,aturale #precipitates$.'(piration 2 9 month

    Cefa2olinAdd @BB mg 9.@ ml of *efazolin #>>B mgml$ to 9>.@ ml of Artificial ears. '(p. 2 F days.Refrigerate. Shake well. he final concentration is >> mgml.

    /entamicino make G mgml final concentration& add >@ mg #B.>@ ml of the 9BB mgml in+ectable$ to @ml of gentamicin ophthalmic solution. '(p./ 9 month.

    InsulinRemove : ml from Artificial ears bottle. Add :BB units #U9BB 1 : ml$ regular insulin. 7inalconcentration 2 9>.@ units ml. '(p. 2 9 month Refrigerate

    %enicillin /3 40enicilina 55Remove @ ml from 9@ ml Artificial ears bottle. Add 9: ml sterile water to :B million unitvial of 0enicillin 5) #concentration 2 9 million units per ml$& add @ ml 0enicillin 5) to 9B mlArtificial ears. 7inal concentration of 0enicillin is >>>&>>> unitsml. '(p. 2 F days.Refrigerate. Shake well.

    $obramycino make G mg ml& add HB mg ml of obramycin in+ectable to @ cc of obramycinophthalmic solution. '(p. 2 9 month.

    6Use Methylcellulose &7 for 'rtificial $ears Unless Other"ise Indicated8

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    'ntimicrobial 'pplication !uggestionsAll of the above drugs are in drop form #solutions$. ne or two drops of the solution can be used ateach dosing interval. he dosing interval for bacterial stromal keratitis usually begins at one to twodrops every >B minutes for the first :H hours. %f improvement is noted after :H hours& the fre!uency

    can persist for another 9: 1 :H hours or begin to taper by 9: #if ! >B minutes then go to ! 9 hour 1 if! 9 hour then go to ! :hours$.

    opical application to mimic subcon+unctival in+ection can be done by instilling one drop minute for@ minutes each hour.When two or more different drugs are being used; they must be instilled at different times 1 at least@ to 9B minutes apart since the lacrimal lake in the dog and cat can not accommodate more thanone drop at a time.

    !pace for NO$E!

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    'nti9inflammatory $herapy

    Anterior uveitis is commonly associated with corneal irritation because when the cornea isabraded& factors are released #substance 0 and likely others$ from the ophthalmic branch of the @thnerve in the cornea. hese factors enter the anterior chamber and cause the release of

    prostaglandin leukotrienes& which generate the signs of anterior uveitis; break down of the blooda!ueous barrier& vasodilatation& leakage of protein& smooth muscle contraction1ciliary spasm andthe respective resulting pain and miosis$.opical or subcon+unctival steroids would be contraindicated yet topical andor systemic anti1inflammatory drugs such as one of the nonsteroidal agents would be indicated.

    9D 0rofenol Suprofen/ one drop : 1 > times per dayoo fre!uent usage will cause a punctate keratitis and may also reduce cornealneovascularization

    B minutes to J times per day.*are should be taken in handling this product since it could become contami