Cornea
Dec 19, 2015
Cornea
Baby picture of the day!
Sodium Fluorescein
Used to stain dead or devitalized cells on the cornea and conjunctiva
Pooling: green pools of fluorescein caused by dips in the tissue
Negative staining: areas with no staining caused by elevation in the tissue
Keratopathies
Dellen Exposure
keratopathy Filamentary
keratopathy Superficial punctate
keratitis
Thygeson’s superficial punctate keratopathy
Neurotrophic keratopathy
Recurrent corneal erosion
Thermal/UV keratopathy
Dellen
Stromal dehydration Fluorescein pooling
Superficial Punctate Keratitis (SPK)
Non-specific inflammation of epithelium
Causes: contact lenses, infection, dry eye, blepharitis, allergy/toxicity, trichiasis, etc.
Exposure Keratopathy
Eyelid problem – incomplete closure
#1 cause: nocturnal lagophthalmos
Other causes: surgery, nerve palsy, CVA, thyroid eye disease, floppy eyelid syndrome
Filamentary Keratopathy
Filaments = epithelial cells + mucous
#1 cause: keratoconjunctivitis sicca
Dryness lids scrape against
cornea friction chronic inflammation
Thygeson’s Superficial Punctate Keratopathy
Young adult patients White conjunctiva with
“crumb-like” central cornea
Cluster of elevated white lesions in central cornea
Lesions don’t stain (unlike SPK)
Bilateral
Neurotrophic Keratopathy
Think CN V1 (nasociliary)
Trigeminal neuropathy from damage to the nerve
Decreased corneal sensitivity decreased wound healing
Bad combination!
Recurrent Corneal Erosion (RCE)
Poor hemidesmosome attachments between epithelium & BM due to previous trauma
Patient awakens with acute pain
Thermal/UV Keratopathy
UV-C (<300nm) is absorbed by the cornea
Causes: sun, welding, snow, tanning
Signs: SPK Symptoms: pain,
photophobia, blur Symptoms begin 6-12
hours later!
Dry Eye Syndrome (DES): Definition
A “multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface.”
Associated systemic diseases: thyroid, arthritis, Sjogren’s, SLE
Problematic meds: anticholinergic, antihistamines, hormone replacement, diuretics
DES: Testing
Schirmer 1: no anesthetic, normal >10mm/5min
Schirmer 2: anesthetic, normal >5mm/5min
Phenol red thread: pH sensitive, normal >10mm/15sec
Tear osmolarity Tear film instability (TBUT)
DES: Categories
Aqueous tear-deficient
Lack of lacrimal secretion Sjogren’s: includes
autoantibodies & dry mouth
Non-Sjogren’s = Lacrimal gland deficiency
Evaporative
Water loss with normal lacrimal secretion
Intrinsic = due to lid pathology
Extrinsic = no lid pathology (vitamin deficiency, preservatives)
Keratoconus Pellucid Marginal Degeneration (PMD) Keratoglobus
All 3 can cause hydrops (tears in Descemet’s membrane)
Ectasias
Keratoconus
Presents at puberty History of atopy Collagen fibril
displacement, corneal thinning, corneal protrusion
Fleischer’s ring = iron deposit at base of cone
Pellucid Marginal Degeneration (PMD)
Presents in young adults
Inferior thinning/protrusion of the cornea
Against the rule (ATR) astigmatism = “kissing doves” / “crab claws” on topography
Keratoglobus
From birth General corneal
thinning, worst in periphery
Easier to perforate cornea
Dystrophies
Anterior
EMBD Meesman’s Reis-Buckler
Stromal
Macular Granular Lattice Schnyder’s
Posterior
Fuch’sPosterior Polymorphous
All of these are autosomal dominant (AD) except macular dystrophy (AR)
EBMD = Map-Dot Fingerprint
Epithelial Basement Membrane Dystrophy (EBMD)
Excessive basement membrane production
Can cause recurrent corneal erosions
Negative staining shaped like map lines or fingerprints
Fuch’s Endothelial Dystrophy
Older female patients Excess production of
posterior lamina (Descemet’s membrane)
Signs: guttata (clumps of Descemet’s BM), decreased endothelial cell density, stromal edema
Symptoms: blurry vision am
Congenital Anomalies of the Cornea
Megalocornea Microcornea Cornea plana Aniridia
Haab’s Striae Axenfeld-Rieger
syndrome Peter’s Anomaly Limbal dermoid
Megalocornea & Microcornea
Megalocornea
X-linked Diameter >13mm Myopic pts
Microcornea
AD or AR inheritance Diameter <10mm Hyperopic pts
Cornea Plana
AD or AR inheritance Corneal curvature
equals scleral curvature
Flat cornea
Aniridia
Bilateral, AD inheritance
Lack of iris tissue Often accompanied
by foveal hypoplasia (reduces VA) & colobomas
Haab’s Striae
Horizontal lines in Descemet’s membrane
Occurs in congenital glaucoma
Peter’s Anomaly
Present at birth Bilateral White cornea
(leukoma)
Bacterial Keratitis Fungal Keratitis Acanthamoeba Keratitis Herpes Simplex Virus (HSV) Herpes Zoster Virus (HZV)
Infectious Keratitis
Bacterial Keratitis
Most common infectious keratitis
Staphylococcus, Pseudomonas, Haemophilus influenzae, Moraxella catarrhalis
Ulcer = infiltrates (immune) + epithelial defect
Infectious ulcers stain
Fungal Keratitis
Feathery edges Caused by plant
trauma Candida infection
indicates immune compromise
Acanthamoeba Keratitis
Contact lens abuse (tap water)
Pain out of proportion to signs
Ring ulcer
DNA virus that infects the trigeminal ganglion (CN5)
Decreases corneal sensitivity Type 1 (top) vs. Type 2 (bottom) Transmission
Herpes Simplex Virus (HSV)
HSV
Epithelial Disease
Dendritic ulcers (stain)
Geographic ulcers (stain)
Neurotrophic Keratitis
Reduced innervation to cornea
Poor wound healing & reduced sensation
HSV
Stromal Disease
Interstitial keratitis = neovascularization, immune ring, stromal thinning/scarring
Endotheliitis
Disciform keratitis = most common
Immune reaction causes stromal edema
Herpes Zoster Virus (HZV)
Varicella Zoster Virus (VZV) Older patients or immune
compromise Pre-zoster prodrome (fever,
malaise, tingling) Active zoster = skin
involvement respecting the vertical midline
Hutchinson’s sign = tip of nose
Peripheral Ulcerative Keratitis
Staph Marginal Keratitis
Type 3 hypersensitivity Sterile infiltrates where lid
touches cornea
Mooren’s Ulcer
Unilateral peripheral crescent-shaped ulcer
Corneal Deposits
Whorl Keratopathy Fleischer’s ring Rust rings Hudson-Stahli lines
Stocker’s line Ferry’s line Kayser-Fleischer Ring Band Keratopathy
Whorl Keratopathy
Caused by systemic disease or medication
No symptoms, no reduction in vision
Fleischer’s Ring
Keratoconus Iron ring at the base
of the con
Rust Rings
Form around metallic corneal foreign bodies
Must be removed along with foreign body
Hudson-Stahli Lines
Iron lines in lower cornea
No symptoms, no reduction in vision
Stocker’s Line
Iron deposit along edge of pterygium
Ferry’s Line
Iron deposits along edge of filtering bleb
Kayser-Fleischer Ring
Copper deposition around edges of cornea
Wilson’s disease (liver)
Band Keratopathy
Calcium deposition Bowman’s layer
Arcus Senilis
Corneal degeneration Most common peripheral
corneal opacity Older patient or high
cholesterol
Unilateral arcus indicates contralateral carotid disease
Corneal Graft Rejection
Type 4 Hypersensitivity
30% rejection rate in first year following transplant
Epithelial, stromal, or endothelial
Look for white blood cells
Refractive Surgery
Types
RK PRK CK Intact RLE PIOL AK
Contraindications
Age <18, unstable refraction
Keratoconus Active herpes/infection Connective tissue disease Immune compromise
(including diabetes) Large pupils
Radial Keratotomy (RK)
Radial incisions flatten the corneal stroma
Unstable Hyperopic shifts
Photorefractive Keratectomy (PRK)
Outer cornea removed (epithelium, Bowman’s, some stroma)
Less myopic because thinner cornea
No flap Healing: 1-2 weeks Problem: stromal haze
Laser-assisted In Situ Keratomileusis (LASIK)
Flap of cornea moved, laser applied beneath to thin stroma, then flap replaced
Less myopic because thinner cornea
Healing: 1-2 days Problem: dry eye
LASIK Complications
Initial pain Infection Flap complications Corneal ectasia
(thinning & protrusion, like keratoconus)
Residual refractive error (under-correction)
Glare Dry eye (#1) Epithelial ingrowth Corneal haze
Conductive Keratoplasty (CK)
Treats hyperopia & presbyopia
Shrink peripheral collagen fibers with radio energy
Problem: regression
Intacs (Intrastromal corneal rings)
PMMA ring in peripheral stroma
Used for keratoconus Less myopic because
ring flattens cornea Can be removed
Refractive Lens Extraction (RLE)
Remove natural crystalline lens, replace with new lens (like cataract surgery)
Works because lenses come in varying powers, select appropriate one
Phakic Intraocular Lens (PIOL)
Lens implanted into an eye in front of the iris (natural crystalline lens remains intact)
Great for high myopia Removable
Astigmatic Keratotomy (AK)
Blade incisions relax the steeper meridian of the cornea
Contact Lens-Related Disorders
Solution hypersensitivity/toxicity
Corneal neovascularization
Corneal warpage
Contact lens deposits Superior epithelial
arcuate lesion (SEAL)
Solution Hypersensitivity/Toxicity
Diffuse SPK (superficial punctate keratitis)
Corneal Neovascularization
Due to lack of oxygen (hypoxia)
If it’s >1.5mm, switch contact lenses or stop wearing them
Corneal Warpage
Cornea changes shape due to contact lenses
GP lenses (gas permeable, “hard” lenses)
Contact Lens Deposits
Deposits of tear components on contact lenses
Clean lenses better!
Dimple Veiling
Air bubbles trapped under a GP contact lens create divots in the cornea