Pathophysiology Flashcards
Prolapsed orbital fat
Orbital septum gets weaker with age
Preseptal cellulitis
Infection anterior to orbital septum, can be caused by:
1. Ocular infection - acute hordeolum, dacryocystitis
2. Systemic infection - URI or middle ear infection
3. Skin infection - puncture wound, insect bite
Usually due to S. Aureus (adults) or H. Influenzae (kids)
Orbital cellulitis
Infection posterior to the orbital septum, can be caused by:
1. Ethmoid or other sinus infections
2. Orbital infection (dacryoadenitis/dacryocystitis, preseptal spread)
3. Orbital fracture
4. Dental fracture
Thyroid eye disease
Autoimmune disorder, TSH receptor antibodies directed against the EOMs and orbital tissue. Causes fibroblast proliferation, inflammation, and thickening of EOMs, and possibly optic nerve compression.
Carotid-Cavernous Fistula
Abnormal communication bw the arterial and venous systems: high pressure from the carotid artery builds up in the CS and impedes the return of blood, leading to a build-up of pressure behind the globe.
Orbital pseudotumour / idiopathic orbital inflammatory syndrome
Idiopathic inflammatory process that can impact any soft tissue component of the orbit. Can resemble TED or orbital cellulitis. May include the tendons of the EOMs in severe disease (in contrast to TED which only affects the EOMs even in severe disease).
Tolosa-Hunt syndrome
Rare type of idiopathic orbital inflammation that can affect the cavernous sinus and the superior orbital fissure (palsies of CN3,4,6, V1, V2)
Ocular rosacea
Inflammatory condition that affects the sebaceous glands (including meibomian) resulting in chronic ocular surface disease
Contact dermatitis
Type 4 hypersensitivity reaction that typically develops 24-72 hours after exposure to the inciting agent. Common to happen with cosmetics, jewelry, plants, CL solutions, medications, preservatives.
Ocular cicatricial pemphigoid
Chronic autoimmune idiopathic mucous membrane disorder affecting oral and ocular mucous membranes (conj esp.) caused by type 2 hypersensitivity reaction involving autoantibodies directed against the conj BM. Can also be drug-induced from timolol, epinephrine, and pilocarpine.
Stevens-Johnson syndrome
severe progression of a type 3 or 4 hypersensitivity reaction that affects mucous membranes, most commonly drug induced (sulfonamides, phenytoin, penicillin, aspirin, barbiturates, isoniazid, tetracyclines, NSAIDs, immunizations), or from an infectious agent (HSV, mycoplasma pneumoniae, adenovirus, strep)
Acute phase (2-4wks) may be followed by chronic phase
Chalazia
Chronic, localized, sterile inflammation of a meibomian gland due to retention of normal secretions. 25% of chalazia resolve spontaneously without treatment.
Hordeolum
Acute staphylococcus infection of meibomian glands for internal hordeolum, and of glands of Zeis and Moll for external hordeolum
Ectropion
Eversion of the lid away from the globe of the eye. Most common cause is age-related/involutional, loss of muscle tone of the orbicularis oculi. The other causes include mechanical, cicatricial, paralytic, and congenital
Entropion
Inversion of the eyelid against the globe. causes include age-related/involutional (most common), cicatricial (trachoma, OCP, SJS, chemical burns, previous lid sx, etc.) and congenital
Floppy eyelid syndrome
Significant reduction in elastin within the tarsal plate, can be caused by face-down sleeping - mechanical trauma to the tarsal plate from chronic lid to pillow contact. During sleep, lid eversion exposes superior tarsal conj to the bedding causing a papillary conjunctivitis due to friction.
Basal cell carcinoma
Malignancy of the basal cell layer of the epidermis. Increased sun exposure in childhood and teen years is a critical risk factor for the development of BCC later in life. Incidence of metastasis is less than 0.1%
Squamous cell carcinoma
Malignancy of the stratus spinosum of epidermis. Associated with UV exposure, actinic keratosis, fair skin, prior radiation, burn scars, chemical exposure (smoking), and other forms of chronic irritation. More aggressive than BCC, 13-24% of SCCs undergo metastasis to nearby lymph nodes
Sebaceous gland carcinoma
Neoplasm of sebaceous glands of the eyelids (meibomian glands or Zeis), poor prognosis, if the lesion is greater than 2cm, the mortality rate is 60%. If symptoms have been present longer than 6 months, the mortality rate is 38%. The overall mortality rate is 10%.
Malignant melanoma
Malignancy of melanocytes, the cells that produce pigment within the skin. Risk factors include age, skin colour, family history, repeated irritation and sun exposure
Dacryoadenitis
Inflammation of the lacrimal gland: acute - resulting from an infection by bacteria (S. Aureus, N. Gonorrhoeae, Strep) or viruses (mumps, mononucleosis, influenza, herpes zoster). Or chronic - more common than acute, results from inflammatory disorders including sarcoidosis, tuberculosis, Graves, idiopathic orbital inflammation.
Canaliculitis
Inflammation of the canaliculi that can be caused by bacterial, viral, or fungal infections. Most commonly due to actinomyces israelii, which is characterized by yellow sulfur granules after expression of the canaliculi. Others include S. Aureus, Candida, Aspergillus, Nocardia, and Herpes Simplex/Zoster
Dacryocystitis
Lacrimal sac infection that occurs when the lacrimal drainage system is obstructed (ex. NLDO) resulting in a back flow of bacteria from the nasolacrimal duct into the lacrimal sac. S.aureus, S. Epidermidis, pseudomonas, H. Influenzae in children
Nasolacrimal duct obstruction
Older pts - involutional stenosis, or also could be from chronic sinus disease, dacryocystitis, and nasal-orbital trauma
Young pts - membranous blockage at the valve of Hasner (congenital NLDO), occurs in 5-30% of newborns. Spontaneous opening of the valve of Hasner frequently occurs 1-2 months after birth, or digital massage can be performed.
Conjunctival melanoma
uncontrolled proliferation of melanocytes, pigmented or non-pigmented, most arise from PAM (5-75% of cases), other from pre-existing nevus (33%) and rarely de novo
Gonococcal conjunctivitis
Neisseria gonorhhoeae (gram neg intracellular diplococci), dx on Thayer-Martin agar (chocolate agar)
Adenoviral conjunctivitis
- Acute Nonspecific Follicular - serotypes 1-11 and 19, most common
- Epidemic Keratoconjunctivitis (EKC) - serotypes 8, 19, 37 - pain and corneal involvement
- Pharyngoconjunctival fever -serotypes 3-5 and 7
Molluscum contagiosum
chronic infectious skin conition caused by the DNA pox virus that is spread through direct contact, if multiple nodules consider HIV or other immunodeficiency conditions
Vernal keratoconjunctivitis
occurs in pts predisposed with atopy conditions (rhinitis, asthma), 40-75% of pts w/VKC have eczema or arthritis, seasonal outbreaks
Atopic keratoconjunctivitis
AKC is not seasonal, year-round itch, type 1 and type 4 hypersensitivity
GPC
non-infectious inflammatory disorder assoc w/friction (mechanical trauma), and an immune response to contact lens surface deposits (proteins), or environment (severe allergies)
