Eye Pathology P1 PDF

Eye Pathology P1 Conjunctival and corneal pathologies Disorders of the eye appendages BMS 200 Outcomes Describe the pathophysiological processes that underlie the main eye illnesses and relate them to their clinical features: Cataracts, keratitis blepharitis, conju...

Eye Pathology P1 Conjunctival and corneal pathologies Disorders of the eye appendages BMS 200 Outcomes Describe the pathophysiological processes that underlie the main eye illnesses and relate them to their clinical features: Cataracts, keratitis blepharitis, conjunctivitis Hypopyon, chalazion Eyelid/conjunctival anatomy and histology The eyelid, conjunctiva, and associated structures are known as the ocular adnexa (can also include lacrimal apparatus) ▪ Conjunctiva = a mucous membrane that extends over the the interior surface of the eyelids (palpebrae) and the anterior aspect of the sclera (bulbar conjunctiva) The palpebrae have a complex structure ▪ Skin on the outer surface, conjunctiva on the inner surface ▪ are supported internally by a strong, fibroelastic connective tissue known as the tarsus (or tarsal plates) ▪ Cilia on the lid margin (eyelashes) that are associated with sebaceous glands and suderiferous glands ▪ Orbicularis oculi (CN VII) and levator palpebrae muscles (SNS innervation) found beneath the skin ▪ Modified sebaceous glands in the tarsus – known as Meibomian glands – contribute to the tear film Eyelid/conjunctival anatomy and histology Glands of Zeis - small, modified sebaceous glands that open into the hair follicles at the base of the lashes Glands of Moll - modified sweat glands that open near the base of the lashes Other named glands here are accessory lacrimal glands Eyelid/conjunctival anatomy and histology Left is doesn'terone “zoomed-out” view, right is “zoomed in” Note the complex, sebum-filled tarsal glands that empty into the duct at the edge of the eyelid Eyelid/conjunctival anatomy and histology Conjunctiva are located over the sclera - not cornea – (bulbar conjunctiva) and the inner aspect of the eyelid (palpebral conjunctiva) ▪ Stratified columnar epithelium with lots of goblet cells Secretes mucous over the surface of the eye, which contributes to the tear film ▪ Also contains accessory lacrimal glands that secretes tears ▪ Deep to the epithelial layer lymphoid follicles are found (like tiny disorganized lymph nodes) Therefore the tear film over the eye is complex: L ▪ Tears secreted from lacrimal glands ▪ Lipids secreted from sebaceous-like glands – mostly associated ↑ with the eyelid ▪ Mucous from goblet cells in the conjunctiva Orbital septum – a brief word Fascial plane behind the orbicularis oculi Separates the eyelid form the orbit ▪ Important barrier to infection Infectious agents that get past the orbital septum can cause a very dangerous cellulitis known as orbital cellulitis ▪ Vision loss ▪ Intracranial infection, thrombosis of intracranial venous sinuses Life-threatening More later in Emerg Med  Lacrimal glands – a brief word Innervated mostly by CN VII (great petrosal nerve, FYI) and sympathetic branches that accompany the lacrimal artery ▪ Puncta are part of the drainage routes that connect to the lacrimal sac, which in turn drains into the inferior meatus ▪ Not shown here are the accessory lacrimal glands located in the conjunctiva Conjunctivitis - overview Types: Infectious: ▪ Bacterial Staph aureus, Strep pneumoniae, H. influenzae, M. catarrhalis Chlamydial and gonococcal ▪ Viral (usually adenovirus) ▪ Parasitic, fungal ! uncommon Immune-mediated ▪ Allergic, atopic, vernal ▪ Irritants (dust, smoke), toxins/chemicals  Inflammation of the conjunctiva Bacterial conjunctivitis ▪ Common infection caused by staph aureus, Strep pneumoniae, Chlamydia trachomatis, or Neisseria gonorrhea Staph aureus and Strep. pneumoniae infections are very common and are usually self-limited Chlamydial and gonorrheal infections can cause conjunctival scarring and blindness ▪ Scarring of the conjunctiva may lead to eradication of the goblet cells in the conjunctival fornix ▪ Loss of mucous production keeps tears from adhering to the cornea, leading to corneal irritation and scarring ▪ Bacterial conjunctivitis tends to have more purulent discharge and last for less time than a viral conjunctivitis Inflammation of the conjunctiva Viral conjunctivitis ▪ Extremely common Usually caused by adenovirus ▪ extremely infectious, self-limited May also be caused by herpes virus and varicella virus ▪ Antivirals for herpes and varicella conjunctivitis improve outcome Redness and swelling of the conjunctiva (hyperemia and chemosis) as well as excessive tearing (epiphora) Has a longer time course than bacterial conjunctivitis (2-4 weeks to resolve) Clinical Features – Infectious Conjunctivitis Red eye (conjunctival injection) Eye feels itchy, sometimes like there’s a foreign body in it – rare for pain to be any more than mild Tearing, discharge, crusting of lashes in the morning (more crusting with bacterial) ▪ LN involved – pre-auricular and/or submandibular – also more likely for bacterial infection Allergic and atopic conjunctivitis will be addressed more when we talk about it in relation to rhinitis (hay fever) and asthma (BMS 250) – all are common types of Type 2 allergic inflammation ~ allergic + atopic ▪ To note – chemosis (swelling of the conjunctiva) is often more pronounced with these types of conjunctivitis Selected types of conjunctivitis Gonorrheal and chlamydial conjunctivitis ▪ Need to be treated urgently, since they can lead to damage to the conjunctiva (reduced ability to produce an effective tear film) and corneal damage Cornea can become ulcerated and scarred ! opacity With gonorrheal infections can perforate the cornea ▪ Trachoma – typical of chlamydial conjunctival infection, leading cause of blindness in the world (not common in industrialized countries) Severe inflammation of the conjunctiva and cornea ! corneal abrasion, ulceration, and scarring Large follicles can be seen (enlarged lymphatic tissue) under the superior palpebral conjunctiva (can also be seen with viral) Conjunctivitis findings The “bumpies” indicated by the arrows are follicles – seen in viral and chlamydial conjuncitivitis These “bumpies” are papillae – seen in allegic Trachoma (cornea is and bacterial conjunctivitis opaque, basically destroyed) Blepharitis Blepharitis = inflammation of the eyelids Can be multiple causes: ▪ Purulent infection of the eyelid at the margin with formation of a cyst = hordeolum (a stye) ▪ Seborrheic dermatitis (like dandruff) or rosacea can cause eyelid inflammation ▪ Allergic, drug toxicity, or autoimmune disease Sjogren syndrome = an autoimmune disorder that damages the lacrimal and salivary glands ▪ In the eye ! dry eyes and minor inflammation ▪ Generalized infections – herpes or varicella (HSV-3) viruses General Clinical Features Blepharitis may cause redness of the eyes, itching and irritation of the eyelids in one or both eyes Often makes the eyes feel dry or “gritty” ▪ Often confused with conjunctivitis, more common mistake is to miss blepharitis in the elderly ▪ Eyedrops don’t tend to help much Untreated blepharitis, in particular due to rosacea, can lead to conjunctivitis ▪ Severe cases ! corneal inflammation and scarring (keratitis) and Infections of the eyelid Hordeolum (stye) ▪ Purulent bacterial infection of a sebaceous or suderiferous gland (either accessory sebaceous glands or Meibomian glands) Tends to be caused by Staph aureus ▪ Small, inflamed, very tender bump appears on the margin of the eye (smaller, more tender than a chalazion) Often resolve without treatment, though warm compresses and good hygeine aid resolution and prevent future recurrences Infections of the eyelid Chalazion – not that “infectious”, more of a granulomatous inflammation: ▪ Lipid products (from breakdown of bacteria or blocked sebaceous secretions) penetrate into the tarsal tissue Elicits a granulomatous inflammation ▪ An inflamed, mildly tender “bump” appears on the eyelid (usually upper eyelid since the glands are longer) ▪ Very common and generally benign, usually treated with heat and massage (though sometimes antibiotics are necessary) They do tend to need treatment to resolve, though Keratitis Usually caused by HSV-1 (usual cause of cold sores) but can be caused by HSV-2 (genital herpes) ▪ Does not tend to cause severe damage on initial infection ▪ After “resolution” of an HSV infection, it lives latent in the trigeminal ganglion and can periodically migrate down the nerve and cause reactivation of symptoms ▪ Reactivation more typically causes a more severe inflammatory reaction in the cornea ! ulceration Reactivation of HSV causing keratitis is often associated with: ▪ Stress, excess exposure to sunlight ▪ Fluctuations in reproductive hormones throughout the menstrual cycle  HSV Keratitis Pathogenesis: ▪ Typically causes many small intraepithelial ulcerations with opacities that occur due to edema just below the epithelium ▪ If chronic (see below) then the stroma is thinned and scarred, edema in the stroma, and abnormalities in the corneal endothelium (see arrows) Clinical Features: ▪ Pain, tearing, foreign-body sensation ▪ Red eye ▪ Can have modestly decreased vision unless damage is severe (scarring)  , ~ Dar HSV Keratitis trig - Herpes zoster ophthalmicus – Herpes zoster (HSV-3) ▪ Dermatitis in the dermatomal distribution of CN V1 that is typically unilateral Hutchinson’s sign: if tip of nose is involved (nasociliary branch of V1) then globe will be involved in ~75% of cases If no nasal involvement, eye is involved in 1/3 of patients ▪ Clinical Features Pain, tearing, photophobia, red eye, corneal edema Corneal hypoesthesia ▪ Complications n Keratitis, ulceration, perforation and scarring al 4- Secondary iritis, secondary glaucoma, cataract - Occasionally severe post-herpetic neuralgia