Ophthalmic Pathology: Posterior Segment Flashcards
What is the part of the eye that converts light into a neuronal impulse?
The retina
What are the layers of the retina?
- Inner limiting membrane
- Nerve fiber layer
- Ganglion cell layer
- Inner plexiform layer
- Inner nuclear layer
- Outer plexiform layer
- Outer nuclear layer
- External limiting membrane
- Photoreceptor layer (Rods and Cones)
- Pigmented epithelium
Retina function…
- Photoreceptors:
- Retinal pigmented epithelium:
- Photoreceptors: Specialized neuron that converts light into neuronal signal
- Retinal pigmented epithelium: Nourishes and supports the photoreceptors
- Absorption of scattered light
- Formation of blood-retina barrier
- Nutrients to photoreceptors/eliminates waste
Function of the retina…
- Inner plexiform layer:
- Inner nuclear layer:
- Outer nuclear layer:
- Inner plexiform layer: transmits information to the brain
- Inner nuclear layer:** houses the bipolar, horizontal, and amacrine cells**
- Outer nuclear layer: contains the cell bodies of the rods and cones
What are the causes or retinal pathology (ITMIINDIO)
- Inborn errors (congenital)
- Trauma and healing
- Medications and exposure
- Infection
- Ischemia or vascular insufficiency
- Neoplasm
- Degeneration
- Immune dysregulation
- Other organ, system
What is the most common form of inherited retinal degeneration? What causes it?
Retinitis Pigmentosa
Caused by abnormalities in photoreceptors or the retinal pigmented epithelium
15% of all retinitis pigmentosa is due to a mutation in _______
rhodopsin
What is rhodopsin?
What is it composed of?
Rhodopsin: light sensitive receptor protein found in rod photoreceptors
Composed of the protein opsin and the cofactor chromophore retinal (produced from Vitamin A)
Mutations in retinis pigmentosa (rhodopsin) usually cause ________ of the opsin protein
misfolding
Why would mutations that affect all cells in the body cause retinitis pigmentosa?
The photoreceptors are very metabolically active and would be affected more than other cells
What are the 3 types of retinitis pigmentosa?
How is it inherited?
- 3 types:
- Non-syndromic
- Syndromic
- Secondary to other systemic disease
- Inherited: Autosomal dominant/recessive and X-linked (multiple methods)
What is age-related macular degeneration?
What accumulates and why?
- Degeneration of the retinal pigmented epithelium
- Accumulation of drusen excrescences believed to represent byproducts of vision
What is another name for the progressive accumulation of drusen in age-related macular degeneration?
Dry macular degeneration
What is the end result of age-related macular degeneration?
Eventually, loss of retinal pigmentation epithelium causes loss of receptors
What is wet age-related macular degeneration?
How is this treated?
This is when blood vessels from the choroidal layer invade the disrupted Bruch’s membrane causing bleeding in the outer layers of the retina
Tx: Injection of anti-VEGF
What is retinopathy of prematurity?
What birth abnormalities increase its risk?
- Abnormal development of the vasculature of the retina in babies born pre-term
- Increased risk if born <1250 grams or earlier than 31 weeks
In normal retinal vasculature:
What provides the posterior circulation?
What provides the anterior circulation?
- Posterior circulation: blood from the choroid feeds the posterior 1/3 of the retina
- Anterior circulation: blood from the central retinal artery feeds the anterior 1/3 of the retina
Why are premature babies at increased risk for retinopathy?
- The babies are born prior to full retinal vascular maturation (halts normal vascular migration to the peripheral retina)
- Vessels and retina become abnormal
What will happen in untreated retinopathy of prematurity?
If untreated, the retina will detach, causing blindness
What is the treatment of retinopathy of prematurity?
Laser the ischemic retina OR
Inject anti-VEGF
(both are equally good treatments)
What is the leading cause of blindness for people aged 20-64 years in the United States?
Diabetic retinopathy
What are the characteristics of diabetic retinopathy?
- Retinal dysfunction due to hyperglycemia
- Pericyte loss in retinal capillaries
- Weak vessels bleed in the retina
What are the vascular findings in diabetic retinopathy?
- Microaneurysms
- Dot-blot hemorrhages
- Flame hemorrhages
What causes retinal detachment in diabetic retinopathy?
- Underperfused retina secretes VEGF
- Abnormal blood vessels grow towards the vitreous and over other structures - fragile vessels bleed
- Contraction of the abnormal vasculature pulls the retina, causing retinal detachment
What are some causes of central retinal artery occlusion?
Atherosclerosis of the carotid artery or embolism
What is the prognosis for central retinal artery occlusion with visualized emboli?
56% mortality rate over 9 years
What part of the retina dies in central retinal artery occlusion?
Inner retina
What is retinoblastoma?
What are the two forms?
Cancer of the immature retinal cells
- 2 forms
- Non heritable (usually unilateral)
- Heritable (usually bilateral) - AD inheritence
What is the mutation in retinoblastoma?
What cell pattern is seen?
Mutation in Ch. 13 on the RB1 gene
Flexner-Wintersteiner rosettes
What is the name and function of cranial nerve II?
Optic nerve: transmits sensory information regarding brightness and contrast perception, color perception and visual field information
What is traumatic optic neuropathy?
What are common mechanisms?
- Direct or indirect injury to the optic nerve results in traumatic optic neuropathy
- Common mechanisms: bike accident; motor vehicle accident; fall and assault
What causes the loss of axons in optic neuropathy?
Axonal loss appears to occur either through direct trauma, hemorrhagic infarction, direct compression of the nerve fibers from an extrinsic nerve sheath hematoma, shearing forces, or a combination of these mechanisms
What is glaucoma?
What are the risk factors?
- Progressive optic neuropathy due to slow loss of optic nerve fibers
- Risk factors:
- Intraocular pressure
- Age
- Central corneal thickness
- Race
