Eye Pathology I Flashcards
What are the main functions of the eyelid?
- Protection
- Distribution of the tear film
- removal of excess tears and foreign material
What are the fornices?
Areas where the conjunctiva forms small pockets
What are the two main functions of the conjunctiva?
- Secretory- mucous contributions to the tear film
- Immunity- CALT which is part of the mucousal associated lymphoid tissue system
- Stem Cells that migrate from the conjunctiva to the site of injury
What are the two types of lymphoid tissue found in the eye?
- Mucousal
- Diffuse lymphoid tissue
What occurs to the antigen in mucousal lymphocytes?
- The antigen is taken up by APC’s and then presented to the lymphocytes
What cells are mainly in the diffuse lymphoid tissue?
Mainly cytotoxic CD8+ cells
Plasma cells that produce igA antibodies
effector tissue
What is the gross appearance of the conjunctiva?
- Smooth
- Shiny
- Can be pigmented
- Visible mobile blood vessels (salmon pink colour but is its whiter over the globe)
What is the main function of the sclera?
- External support to the globe contents
- movement of globe acts as an insertion point for extraocular muscles
What is the function of the third eyelid?
- Protection of the cornea
- Distribution of the tear film
- Nicitans gland contributes around 30-40% of the aqueous component of the tear film
What composes the lacrimal system?
e.g the two main functions
Tear Production and tear drainage
What are the three components of the tear film?
- Mucus- goblet cells in the conjunctiva
- Aqueous- lacrimal gland in the upper eyelid and nicitans gland in the third eyelid
- Lipid- meibomian glands on the eyelid margin
What are meibomian glands?
large sebaceous glands present in the eyelids which secrete lipids that form the superficial layer of the tear film
What are the four functions of the tear film?
- Lubrication
- Immune modulation
- removal of debris
- Nutrition to the cornea
What is endotropion?
Internal rolling in of the eyelid
What is ectropion?
External rolling out of the eyelid
What causes endotropion/ ectropion?
- Congenital
- Developmental
- Trauma
- Inflammation
- Iatrogenic (poor surgical technique)
What is distichia?
- abnormal hairs arising from the meibomian gland and exciting out of the eyelid margin
What is ectopic cillia?
Abnormal hairs arising from the meibomian gland but exciting out of the palpebral conjunctiva
What is blepharitis?
Inflammation of the eyelids
What is chalazonian?
small lump or cyst develops on the eye due to a blocked oil gland
* response to the leakage of meibomian gland secretions
* leakage of lipid into the subconjunctival space
* chronic inflammation leads to calcification of the gland and surrounding tissue
What is a stye?
Suppurative inflammation of the adnexal glands
What causes parasitic blepharitis?
Demodex and sarcoptes scabei
What causes idiopathic blepharitis?
- Predominantly macrophages and neutrophils
- it is not associated with adnexal structures and there is no identifiable agent
What is the protrusion of the nicitans gland also called?
Cherry eye
What happens when there is a decrease in laxity of the ligament that holds the nicitans gland in place?
Nicitans gland ‘pops’ out
causes cherry eye
What are the two causes of conjunctivitis?
- Infectious- e.g bacterial, viral
- non-infectious- allergies, environmental irritants
What is the most common cause of non-infectious canine conjunctivitis?
Dry eye is the most common in dogs
local irritation is also common
any type of eyelid abnormality
What is the main virus that causes conjunctivitis in cats?
Feline Herpes Virus
What is Infectious Bovine Keratoconjunctivitis?
- Caused by Moraxella bovis
- causes ‘pink-eye’
- pilli allow epithelial treatment
What is Immune-Mediated Keratoconjunctivitis Sicca?
the body recognises self-antigens in the lacrimal gland
starts a T-Cell response against the antigens
decreases the tear film quantity and quality
When should you use a schirmer tear test?
in all mucky and red eyes
What are some common causes of dry eye?
- Developmental KCS
- Metabolic
- Neurological Inflammation/ Infection
What species usually gets retained spectacles and why?
Snakes
* due to poor environment
* lack of correct humidity
What is the difference between a stye and a chalazonian?
- Chalazonian is granulomatous inflammation
- Stye is Suppurative inflammation
What does Feline Herpes Virus Cause in cats?
- Conjunctivitis
- Keratitis
- Upper Respiratory Disease in Young Cats
What may cause blepharitis?
- Bacterial
- Mycotic
- Parasitic
- Protozoal
- Immune-mediated
What are the clinical signs of conjunctivitis?
- Hyperaemic/ Edematous coonjunctiva (vasodilation/ increased blood flow)
- Lymphoid follicles
- Ulceration
- Fibrosis
What does FHV-1 cause in cats?
- Conjunctivitis
- Keratitis
- URD
- Superficial ulcers
What is the pathogenesis of the T-Cell response in immune mediated sicca?
- immune system becomes overeactive and starts attacking its own tissues
- white blood cells accuulate in the lacrimal gland
- inflammation of the lacrimal gland
- ability to produce tears is diminished
What are the results of the schirmer tear test?
- Less than 10= insufficient tear production
- 20= normal tear production
