Uveal Tract Flashcards
What are the 3 anatomical components to the uveal tract?
Iris whihc is apart of the anterior uvea
Ciliary Body whihc is apart of the anterior uvea
Choroid which is a part of the posterior uvea
What are the zones that make up the iris?
Ciliary zone (peripheral)
Pupillary zone (central)
Collarette (transition)
Describe the anatomy of the iris
Made up of stroma which is a fibrous connective tissue made of collagen bundles.
Contains both pigmented and non pigmented cells as well as blood vessels.
The sphincter muscles are also located here
Anterior surface made of a modified stromal border
Posterior surface has a bilayer iris epithelium
Ciliary body and iris are back to back on the same structure
Describe the blood supply to the iris
Long posterior ciliary arteries and anterior ciliary arteries which make up an incomplete arteriole surface
What is the function of the iris?
Controls amount of light entering the eye
Forms part of blood-ocular barrier
Describe the interspecies variation of the iris between dogs, cats & horse and ruminant
Dogs: Constrictor muscle as a circle surrounding the pupil with radial dilator muscle coming off of it
Cats: Radial dilater muscles and two bands of constrictor muscle whihc give way to a slit pupil
Horse & Ruminant: Radial dilator muscles and two bands of constrictor muscle surrounding the horizontal oval pupil
Black bobbles along the dorsal and ventral pupil known as Corpora nigra & granular iridica
What are the different components to the ciliary body and their functions?
Made of structures including the ciliary muscle, ciliary processes, ciliary vessels and ciliary epithelia.
The ciliary muscle is in charge of changing the shape of the lens
The ciliary processes participate in the production of the fluid in the eye also known as the aqueous humour.
The ciliary body is attached to the lens by the collection of tiny fibrous cords known as the zonular fibers. This attachment is crucial in changing the eye focus by changing the shape of the lens, a process known as accommodation.
The ciliary body forms part of the iridocorneal drainage angle which is where the aqueous humour is drained (via a trabecular meshwork)
Constitutes apart of the blood aqueous barrier & provides nutrients to the lens & cornea
What is the aqueous humour?
A liquid composed of 98% water & protein.
Supplies nutrients and removes waste from avascular tissue of the eye. By removing this debris it plays a role in maintaining optical clarity
Describe the anatomy of the Choroid
Made up of 5 layers within each is a network varies blood vessels.
The choroid sits up in thee retinal pigment epithelium
What is the function of the choroid?
Blood supply of the retina (provides nutrients) it is also a key formation in the blood ocular barrier
The choroid also contains the tapetum which reflects light back onto the retina improving eyesight in poor light conditions
Detail the mechanisms in which the eye has immune privilege
Mechanisms include:
Blood-ocular barriers: limiting access of pathogens into eye
Absence of lymphatic pathways: limiting access to lymphatic tissues
Aqueous humour composition: ascorbic acid and other anti-oxidants
Immunomodulatory ligands on intraocular cells (esp pigmented epithelial cells)
Indigenous, tolerance-promoting antigen-presenting cells
Sometimes individual mechanisms are overwhelmed or breakdown, with resulting inflammation: UVEITIS
How would you examine the anterior uvea?
Darkened room
Light source +/- magnification
Pupillary light reflex
Distant direct ophthalmoscopy to look for anisocoria (more later)
Intraocular pressure testing
Explain the concept of Uveitis
Inflammation in the uvea caused by an increased permeability of vessels and WBC migration in response to a pathogen
What are the clinical signs of uveitis
Clinical Signs
Pain –
Blepharospasm (squinting), epiphora, photophobia
Red eye –
conjunctival and episcleral hyperaemia
Miosis, swollen dull iris, rubeosis iridis
Inflammation in anterior chamber
Aqueous flare
Hypopyon (Pus in anterior chamber)
Hyphaema (Blood in anterior chamber)
Keratic precipitates
Corneal oedema
Low intraocular pressure (may help diagnosis!)
What are some secondary consequences to uveitis?
Synechiae (iris adheres to lens or cornea)
Secondary glaucoma
Cataract
Retinal detachment, retinal degeneration, optic nerve atrophy
Vision loss
