讲义成果讲稿cornea

1、corneaKey point Clinical findings and course of common keratitis; treatment and prevention of common keratitis and its sequelae Also to know concept of superficial diseases concept of limbal stem cells pathophysiology of cornea corneal diseases as main cause of blindness limbal stem cell bacterial k

2、eratitis fungal keratitis herpes simplex keratitis corneal ulcer KPIntroductionThe cornea is the anterior transparent part of the collagenous wall of the eyeballIt is the window of the eyeTransparency and regularity are requiredGross anatomy1 The diameter: slightly larger horizontally than verticall

3、yhorizontally: 11.512mmvertically: 10.5mm 11mm2 The thickness: periphery more than centralcentral: 0.50.57mmPeriphery: 1.0mm3 The curvature: larger anterior surface than posterior surfaceanterior surface: 7.8mmposterior surface: 6.8mm Diopter of cornea: +43D70% of the total diopters We can do lots o

4、f things on the corneaHistologyEpitheliumBowmans membraneStroma Descemets membraneEndothelium InnervationMost densely innervation tissues in the bodySensory branches from the trigeminal nerveLoose myelin sheathsLocated in the anterior third of the stromaNutrition and metabolic supplyGlucose : from a

5、queousOxygen : directly from the air by diffusionWhy TransparencyThe corneal epithelium is a stratified, squamous, nonketatinized epitheliumThe corneal epithelium has cellular functions common to other epithelia, so called housekeeping function, maintaining the basal celluar function in renewal and

6、the overall barrier function against the outsideWhy TransparencyThe stroma makes up about 90% of the corneal thickness.Highly ordered collagen fibrills Blood vessels are absent except for the extreme peripheryWhy TransparencyEndothelial cell layer is extrordinarily importantFluid-transporting functi

7、on is what keeps the cornea transparentFluid leaks slowly from the anterior chamber of the eye into the corneal stroma. As fluid leaks in, the endothelium pumps it out.Why TransparencyTear film Extreme molecular regularity of lipid layer in surface soluble, colorless molecules in lipid film and in w

8、ater phaseOcular Surface Star: Surface epithelium lids/sclera/cornea bulbar palpebralSupporting Cast: Lids lashes meibomian glands Tear film Lacrimal glandtear filmLipid, aqueous and mucin components1 Outer lipid layer prevents evaporationSecreted by meibomian glands2 Aqueous component a complex mix

9、ture of proteins,mucins,electrolytesSecreted by main & accessory lacrimal glands3 Mucins provide viscosity and stability during the blink cycleLimbal StructureTransitional zone: clear cornea continues into the opaque scleraThe basallayer of the limbal epithelium contains the stem cells of the epithe

10、liumRegenerationosmolarity ocular surface inflammationdigests tight junctionsdesquamationHyperosmolarity is the most important factor (Mathers)Hyperosmolarity causes ocular surface epithelium damage (Kenyon, Gilbard, Farris) - goblet cells reduced- damaged epithelial cells - inflammation- symptomsCa

11、uses of HyperosmolarityDecrease Tear Secretion Lacrimal gland inflammation/damage Closure of ducts (pemphigoid, etc.) Decreased corneal sensation (contact lens wear)Increase Tear Evaporation Meibomian gland dysfunction Increased surface area of palpebral fissure (proptosis)Tear quantityTear qualityR

12、ole of inflammationDiagnostic tests- rose bengal, lissamine green, fluorescein- tear film break-up- Schirmer testLots of “tears”preserved/non-preservedPunctal plugsCyclosporine (Restasis)Topical steroids (be real careful!)Autologous serum (Tsubota)Inhibitors of cytokines, etc.Loss of corneal epithel

13、ium stem cell population (limbus) leads to re- epithelialization of cornea by bulbar conjunctival cellsCorneal epithelial repair by conjunctival epithelium results in neovascularization, inflammation, recurrent epithelial defects, goblet cells on cornea,scarringOcular surface disease limbal stem cel

14、l deficiencyChemical burnsAniridiaStevens-Johnson SyndromeThermal burnsIatrogenic (limbal surgery)Contact lens inducedDont forget “Blepharitis”!meibomian gland dysfunction, acne rosaceaStaph blepharitislid scrubsdoxycycline antibiotic ointmentwarm compresses three to four times a day soften the oils

15、 and debris that are in the eyelid margin for easy Massage in a circular motion to loosen the debris Regular eye hygiene: daily washing topical antibiotics, artificial tearskeratitisCornea disease: inflammation, trauma, conginetal diseases, dystrophy,degenerationKeratitis: the eye condition in which

16、 the cornea es inflamedVarious types of infections, dry eye, injury, and a large variety of underlying medical diseases may all lead to keratitis. Some cases of keratitis result from unknown factorsKeratitis can be classified by its location, severity, and causesuperficial keratitis. stromal keratit

17、is or interstitial keratitis mild moderate severe keratoconjunctivitis kerato-uveitis acute chronicsymptoms and signs pain tearing sensitivity to light blurring of vision diagnosis history physical examination: slit lamp laboratory examination vivo confocal microscopy culture may be taken from the s

18、urface of the eye Infection is the most frequent cause of keratitisBacteria, viruses, fungi, and parasitic organisms High risk: any break or disruption of the surface layer (epithelium) Treatment depends on the cause of the keratitisInfectious keratitis generally requires antibacterial,antifungal, o

19、r antiviral therapy to treat the infectionEyedrops, pills, intravenous therapySteroid drops may often be prescribed to reduce inflammation and limit scarringContact-lens wearers are typically advised to discontinue contact-lens wearSurgery treatmentResultsuperficial keratitis: without scardeeper lay

20、ers: scarBacterial Keratitis Bacterial keratitis is an infection of the that is caused by bacteriaTypes of bacteria that commonly cause bacterial keratitis include:StaphylococciHemophilusStreptococciPseudomonas Natural history Colonization : the first step after the arrival of pathogenic bacteria to

21、 corneal surfaceInvasion: the microorganism can breakdown the epitheliun layer cells and originate a corneal epithelial ulcer or crossing Bauman layerMultiplicationInflammatory response: some potent mediators named cytokines to response which can cause edemaNatural history Migration of leukocytes: f

22、rom new vessels formed on clear cornea or from limbus ingest bacteria and digest it Anterior Chamber inflammatory reaction: the arrival of leucocytes and fibrin to anterior chamber is called flare and the accumulation of inflammatory cells is visualized like hypopyonScarPathogenic bacteria colonize

23、the corneal stroma and immediately e antigenic, both directly and indirectly, by releasing enzymes and toxinssight-threatening processrapid progression processcorneal destruction may be complete in 24-48 hours Risk factorsContact lens wearOvernight wear Temporary reshaping of the cornea (to correct

24、nearsightedness) by wearing a rigid contact lens overnight, otherwise known as orthokeratology (Ortho-K) Not disinfecting contact lenses wellNot cleaning contact lens casesStoring or rinsing contact lenses in waterUsing visibly contaminated lens solutionTopping off lens solution rather than discardi

25、ng used solution and replacingSharing non-corrective contact lenses used for cosmetic purposesRisk factorsTrauma (including previous corneal surgery)Use of contaminated ocular medicationsDecreased immunologic defensesAqueous tear deficienciesRecent corneal disease (herpetic keratitis, neurotrophic k

26、eratopathy)Structural alteration or malposition of the eyelidsSymptomsEye painExcessive tearingSensitivity to lightBlurred visionEye rednessEye dischargesignupper eyelid edemaconjunctival hyperemiaulceration of the epithelium,dense suppurative stromal inflammation with indistinct edges stromal absce

27、ss formationsurrounding stromal edema Increased anterior chamber reaction with or without hypopyonDiagnosHistorySymptoms and SignLaboratory TestLaboratory methodsTo take a small sample of corneal secretion of the surrounding or central zone of the ulcer with the aple with cotton swab to do the stain

28、 or culturevivo confocal microscopy TreatmentIf no organisms are identified on the slide smear, initiate broad-spectrum antibiotics with the following: tobramycin (14 mg/mL) 1 drop every hour alternating with fortified cefazolin (50 mg/mL) 1 drop every hourThe fourth-generation ophthalmic fluoroquin

29、olones include moxifloxacin and gatifloxacin antibiotic administrationBlunting of the perimeter of the stromal infiltrateDecreased density of the stromal infiltrateDecreased stromal edema and endothelial inflammatory plaqueDecreased anterior chamber inflammationSurgeryPenetrating keratoplastyFungal

30、keratitis Fusarium and Aspergillus ,Dematiaceae (pigmented filamentary fungi, including Curvularia and Lasiodiplodia species), and yeasts (including Candida species) Fungi gain access into the corneal stroma through a defect in the epithelium, then multiply and cause tissue necrosis and an inflammat

31、ory reactionHard to diagnosis: lack of suspicion Hard to management: poor corneal penetration and the limited commercial availability of antifungal agents. HistoryA history of outdoor eye trauma often is reportedForeign body sensationIncreasing eye pain or fortSudden blurry visionUnusual redness of

32、the eyeExcessive tearing and discharge from the eyeIncreased light sensitivitySignConjunctival injection Fine or coarse granular infiltrate within the epithelium and anterior stromaGray-white color, dry, and rough corneal surface that may appear elevatedTypical irregular feathery-edged infiltrateWhi

33、te ring in the cornea and satellite lesions near the edge of the primary focus of the infectionanterior chamber inflammation, hypopyon, iritis, endothelial plaque, or possible corneal perforation obtaining a sample of the lesion by scraping or corneal biopsy Treatment is difficultNatacyn (natamycin

34、5%, Alcon)amphotericin Bpyrimidine analogs (flucytosine)midazoles (clortrimazole, miconozole,ketoconazole)triazoles (fluconazole, itraconazole)Surgerycorneal transplantation (15-27% ) therapeutic penetrating keratoplasty within 4 weeks of presentationconjunctival flap to control the infection and to

35、 maintain the integrity of the globeHerpes Simplex KeratitisHerpessimplex keratitis (HSK) is a major cause of visual morbidity worldwide60-70% of children under 5 90% adults are serapositive for the HSVPrimary HSV-related eye disease is usually asymptomatic Herpes simplex is transmitted via bodily fluids, usually saliva, and may affect the skin and mucous membranes of the hostAfter resolution, the virus remains dormant i