Lecture 8 Flashcards
Retinal disease: Photoreceptors
- Retina pigmentosa
-Macular degeneration
Retinal disease: Horizontal cells
-Retinoblastoma
Retinal disease: Bipolar cells
-Stationary (night blindness)
Rertinal disease: Amacrine cells
-Nystagmus
-Glaucoma
Retinal Disease: Retinal ganglion cells
-Glaucoma
-Retina neuropathy
-Optic neuritis
What are the most susceptible retinal cells in dysfunction and cell death?
1) Retinal ganglion cells
2) Photoreceptors
Environmental exposures leading to ocular disease / injury:
Anterior:
-Cornea and Sclera : Inflammation, irritants
-Vitreous: formic acid
-Lens: lead
Posterior:
- Lead, prenatal lead, methylmercury, toluene, cyanide, pesticides
Toxic optic neuropathies
- At the optic nerve
-retinal ganglion cells are the main cells effected
Common symptoms in humans:
– Loss of color vision (not related to cone photoreceptors)
– Visual field loss
– Reduced contrast sensitivity
– Slowed visual search speeds
Why are retinal ganglion cells (RGCs) more susceptible to toxins?
-They have long axons that require a lot of nutritional energy support from the mitochondria and other cells
- RGCs with small cell bodies are more susceptible to dysfunction and death
- Acute exposures lead to temporary vision loss, but most people recover
-Chronic loss of oligodendrocytes will lead to retinal ganglion cell death and permanent loss of vision
Cuba experienced an optic and peripheral neuropathy epidemic:
Symptoms:
* Blurry vision
* Loss of color vision
* Scotoma (blind spot in vision)
* Blindness
* Peripheral neuropathy
“paresthesia”
Men and women had different neuropathy symptoms
In 2 years, the epidemic spread across the entire nation
Caused by inadequate nutrition
What caused the optic neuropathy epidemic in Cuba?
Initial studies suggested a nutritional toxicity mechanism for the neuropathy.
- The change in diet led to a B-vitamin deficiency.
* B12 (cobalamins) & B9 (folate/folic acid) - Cyanide poisoning:
* Tobacco usage
* Consuming cassava root & cabbage - Increase physical activity
* Drains energy & B-vitamins
Cyanide inhibits cytochrome oxidase preventing oxidative phosphorylation
Cuban leaders refused to believe the results their own scientists presented
What aided in reducing the effects of neuropathy epidemic?
Multi-vitamins
Myelin was damaged
- About 10% of patients exhibited permanent vision loss & blindness.
Of the patients with chronic
vision loss (10%):
- 90.4% had some vision
impairment.
- 8.6% disabled by vision loss.
- 1% were legally blind.
- Opa1 mutations
- Leber’s Hereditary Optic
Neuropathy (LHON)
Retinal ganglion cells (RGCs) connect the ________ to the ________ via the optic nerve
connect the retina to the brain
Developmental exposure to lead (Pb2+)
Has toxic effects on the nervous system and can cause several symptoms:
* Learning disabilities (i.e. reduction in
IQ)
* Behavioral deficits
* Sensory deficits (including vision loss)
Pb exposure disrupts ______________ and _________________ morphology and proliferation
myelination and oligodendrocyte
These are critical for axon integrity and function
- Pb exposure decreases the total oligodendrocytes and
oligodendrocyte precursor cells (OPCs) in the optic nerve
Many toxicants target what to disrupt neuronal function and survival?
Mitochondria
