2 – Intraocular Structures Flashcards
What is the uvea?
- Vascular tunic of the eye
What are the 2 parts of the uvea?
- Anterior
o Ciliary body
o Iris - Posterior
o Choroid
Iris
- Forms the pupil
o Sphincter muscle=constricts
o Dilator muscle=dilates
Ciliary body
- Produces aqueous humor
- Attachment for zonules (equator of the lens and ciliary processes) that suspend the lens
Choroid
- Blood supply to outer retina
- Contains tapetum lucidum dorsally in the fundus
o Bright structure that increases light capture
What is the circulation of the aqueous humor?
- Posterior chamber
- Pupil
- Anterior chamber
- Filtration angle
- Collecting veins into systemic circulation
What is the function of the aqueous humor?
- Maintains intraocular pressure
- Provides nutrition and waste removal for lens, inner cornea
What are the 2 blood-ocular barriers?
- Blood-aqueous barrier
- Blood-retinal barrier
*each have an epithelial and endothelial portions
What does a breakdown of blood-aqueous barrier result in?
- Anterior uveitis
What does breakdown of blood-retinal barrier result in?
- Posterior uveitis
Uveal pathology
- Congenital
a. Persistent pupillary membranes=vascular strands of iris that failed to regress
b. Iris hypoplasia
c. Heterochromia iridis - Inflammation: uveitis
- Neoplasia
a. Ciliary body adenoma
b. Melanocytomas and melanomas
Anterior uveitis: example
- Iridocyclitis
o Inflammation of iris and ciliary body
What is anterior uveitis due to?
- Protein and cellular leakage into aqueous humor
o Protein: aqueous flare
o WBCs: hypopyon
o RBCs: hyphema
o Fibrin
o Keratic precipitates
What is the sequelae of anterior uveitis?
- Disruption of normal nutrition and waste removal
o Cornea: edema, degeneration
o Lens: cataract, zonular breakdown - Adhesions and scar tissue formation inside the eye
o Secondary glaucoma
Posterior uveitis: examples
- Choroiditis: inflammation of choroid
- **Chorioretinitis: inflammation of choroid and retina
Posterior uveitis: tapetal hyporeflectivity
- Fuzzy, gray exudates within or behind retina or within vitreous that OBSTRUCT view of tapetum lucidum
- Ex. hemorrhage, retinal detachment and granulomas
Panuveitis
- BOTH anterior and posterior uveitis
- Endophtalmitis
What is phthisis bulbi?
- Chronic, uncontrolled uveitis leading to a shrunken globe
o Over time it stops producing aqueous and it gets softer and smaller
What are the 2 broad causes of uveitis?
- Ocular disease
- Systemic disease
What are some ocular disease causing uveitis?
- Ocular trauma
- Complex corneal ulceration or laceration
- Lens-induced
- Pigmentary uveitis
- Intraocular neoplasia
- Scleritis
- Retinal detachment
- Iatrogenic
- Idiopathic
What are some systemic diseases causing uveitis?
- Infectious disease
- Neoplasia: metastasis to eye
- Immune-mediated disease
- Septicemia and endotoxemia
What are 2 potential uveal neoplasia’s?
- Ciliary body adenoma
- Melanocytic tumor of anterior uvea: large heavily pigmented mass arising from iris and ciliary body
What is filtration angle (iridocorneal angle)?
- Located where iris and cornea meet
- Pectinate ligaments span opening of filtration angle
- *drainage of aqueous humor and return to systemic circulation
Filtration angle pathology
- Glaucoma
o Elevated intraocular pressure due to DECREASED drainage of aqueous humor
o *NOT from over production
What are the mechanisms of a glaucoma?
- Blockage at filtration angle
- Blockage at pupil
What are the causes of a glaucoma?
- Congenital glaucoma=embryologic errors
- Primary glaucoma=inherited
- Secondary glaucoma=ocular disease (uveitis, lens instability)
What is posterior synechia?
- Iris is adhered to the lens
- *blockage at a pupil
What do you see with acute glaucoma?
- Corneal: endothelial cell dysfunction=edema
- Iris: muscle dysfunction=dilation
- Retina and optic nerve: cellular dysfunction=temporary vision loss
What do you see with chronic glaucoma?
- Globe stretching/enlargement (BUPHTHALMOS)
o Breaks in Descemet’s membrane (striae)
o Lens zonule breakage and lens luxation - Retina and optic nerve ischemia and oxidative stress=permanent retinal ganglion cell death
- *end stage eye: 1. Irreversible blindness, 2. Pain
Lens anatomy
- Outer capsule
- Anterior lens epithelium and lens fibers
o Cortex
o Nucleus=gets harder with age
Lens physiology
- Transparent
o Dehydrated state
o Avascular: obtains nutrition from aqueous humor - Biconvex
Lens aging is called
- Nuclear sclerosis
o Lens fibers proliferate through life
o New outer fibers push older inner fibers concentrically towards lens nucleus
o Normal old age change
Lens (‘phak’)pathology
- Congenital: aphakia, microphakia
o Embryologic errors in development - Lens instability: luxation and subluxation
o Due to breakdown of zonules
o Anterior: in front of iris
o Posterior: behind iris
Zonular break down (lens instability)
- Primary: inherited zonular degeneration (Terriers)
- Secondary: uveitis, trauma, glaucoma
What is the consequence to the eye with lens instability?
- Uveitis due to microtrauma of unstable subluxated lens
- Glaucoma due to disrupted aqueous humor outflow
What is cataract due to?
- Protein and/or hydration changes in lens metabolism
o Results in altered organization of lens fibers
o Manifests as an opacity in lens (white) - *inherited or metabolic (diabetes)
What are the consequences for the eye, if there is cataract?
- Disrupts vision
- Causes inflammation due to leakage of proteins across intact lens capsule
o Phacolytic uveitis
- Causes inflammation due to leakage of proteins across intact lens capsule
What is phacolytic uveitis?
- Lymphocytic plasmacytic inflammation
Phacoclastic uveitis
- Penetrating lens trauma with capsule rupture
o Cataract with massive release of lens protein through the rent in lens capsule
o Severe (phacoclastic) uveitis leading to glaucoma - SEVERE
What is the composition of vitreous?
- Water: 99%
- Collagen fibers which serve as a skeleton for the gel
- Cells (hyalocytes)
- Hyaluronic acid
What is the role of vitreous?
- Maintains ocular shape
- Maintains lens and retina in their normal anatomic position
- Transmits light
Pathology of vitreous
- Persistent hyperplastic primary vitreous (congential)
- Vitritis
- Vitreal hemorrhage
- Liquefaction/degeneration/syneresis: due to old age or previous vitritis
- Asteroid hyalosis: calcium and phospholipids in vitreous
What happens with liquefaction/degeneration/syneresis of the vitreous?
- Condensation of collagen fibrils with liquefaction
- Puts retina at risk for detachment
What are the 2 components of the retina?
- Retinal pigment epithelium (RPE)=one cell layer
- Neurosensory retina=multiple layers
Retinal pigment epithelium (RPE)
- One cell layer thick
- Support retina
o Transports ions, removal of waste products, regeneration of photoreceptors
Neurosensory retina
- Phototransduction by photoreceptors
o Conversion of light energy into electrical signal
o Rods (night vision) and cones (day and colour vision) - Blood supply and nutrients
o Outer: choroid
o Inner: retinal vessels
Retinal pathology
- Retinal dysplasia
- Retinal degeneration
- Retinal detachment
- chorioretinitis
Retinal degeneration: retinal thinning
- Dorsal fundus: tapetal hyperreflectivity (looking through less cells)
- Ventral fundus: pigment clumping and depigmentation
- *retinal vascular attenuation
What causes retinal degeneration?
- Inherited
- Toxicity
- Nutritional
- Glaucoma
What is retinal detachment?
- Separation between photoreceptor layer of retina and RPE
o Embryological potential space between them
What does acute retinal detachment lead to?
- Vision loss due to loss of contact between retina and RPE
What does chronic retinal detachment lead to?
- Death of photoreceptors due to loss of support from RPE
What are the 2 mechanisms of retinal detachment?
- Rhegmatogenous retinal detachment
a. Tears or holes, expand due to liquified vitreous entering subretinal space - Non-rhegmatogenous retinal detachment
a. Fluid and cells
b. *looks like a ‘seagull’
Optic nerve=CNII
- Retinal ganglion cells
- Optic nerve to optic chiasm to optic tracts to optic radiations to visual cortex
Optic nerve pathway
- Optic nerve
- Optic chiasma
- Optic tracts
- Optic radiations
- Visual cortex
Optic nerve congenital pathology
- Optic nerve hypoplasia: reduction in ganglion cells
- Optic nerve aplasia: ganglion cells absent
Optic nerve acquired pathology
- Inflammation: optic neuritis
- Degeneration: optic nerve atrophy
- neoplasia
What are the signs of optic neuritis?
- Optic disc may be elevated, enlarged, fuzzy
- Exudates, hemorrhages of optic disc
What are the causes of optic neuritis?
- Immune-mediated
- Systemic infection
- Trauma
What are the signs of optic nerve degeneration?
- Disc appears darker, smaller, cupped
What are the causes of optic nerve degeneration?
- Chronic glaucoma: loss of retinal ganglion cells
- Post-optic neuritis
- Post-traumatic
