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VisualSystem

Exam 6 - Lecture 3

QuestionAnswer
Top 5 Causes of Blindness (Worldwide): 1. Cataracts 2. Glaucoma 3. Macular Degeneration 4. Corneal Opacity 5. Diabetic Retinopathy Eye Structure consists of:
Accessory Structures of the Eye Palpebrae, Palpebral Fissure, Lateral/Medial Canthus (where the top and the bottom eyelids are connected at the outer/inner corners of the eye), Eyelashes, Glands, Conjunctiva (epithelial covering of the inside of the eyelid and outside of eyeball)
Palpebrae Eyelid (physical barrier, continuous with skin)
Palpebral Fissure Space between the eyelids
Lateral/Medial Canthus Where the top and the bottom eyelids are connected at the outer/inner corners of the eye
Eyelashes Physical barrier of the eye
Glands of the Eye Lacrimal (tear), Tarsal (Mebomian), Sweat
Location of Lacrimal Gland Superior and lateral to the eye
Location of Tarsal Gland Inside of eyelids (produce Mebomian – a lipid-rich secretion)
Location of Sweat Glands (eye) Between eyelash follicles (produce sweat)
Functions of Glands (of the eye) Lubricate eye, prevent evaporation, antibacterial and antifungal properties
Conjunctiva Epithelial covering of the inside of the eyelid (Palpebral) and outside of eyeball (Ocular)
Location of Palpebral Conjunctiva Inside of eyelids
Location of Ocular Conjunctiva Outside of eyeball
Two types of Gland infections: 1. Chalazion (inflamed Tarsal gland) 2. Sty (infected Tarsal gland)
Chalazion Inflamed Tarsal gland; Painless; Lasts for a month
Sty Infected Tarsal gland; Painful; Lasts for days
Treatment for Chalazion and Sty Warm compress, lance; if infected – topical antibiotics
Conjunctivitis Pink Eye; Inflammation of the Conjunctiva; Itching, burning, watery; Bacterial or viral (highly contagious); Chemical, allergy, physical
Symptoms of Conjunctivitis Itching, burning, watery eyes
Conjunctivitis can be _______ or ________ and can be due to _________, __________, or __________. Bacterial or viral; Due to chemical, allergy, or physical
Treatment for Conjunctivitis No contact lenses; Warm, moist compress; Time; Bacterial give antibiotics (drops or ointment); Allergic give anti-inflammatory or antihistamines
What types of antibiotics do you give for Bacterial Conjunctivitis? Drops or ointment
Lacrimal Apparatus Structures of the eye that produce, distribute, store, and remove tears – Lacrimal Gland and Ducts, Lacrimal Caruncle, Lacrimal Punctum, Lacrimal Canaliculus, Lacrimal Sac, Nasolacrimal Duct
The secretions of the Lacrimal Gland: Provide nutrients and oxygen to corneal cells, Contain lysozymes and antibiotics
The Lacrimal Gland produces about ___mL per day 1 mL
Secretions of the ____________ provide nutrients and oxygen to corneal cells Lacrimal Glands
Function of Lacrimal Gland and Ducts Produces and delivers tears to the eye (about 1 mL per day)
Lacrimal Caruncle Glandular tissue near Medial Canthus; Tears pool here (Lacrimal Lake)
Where do tears pool? Lacrimal Caruncle (Lacrimal Lake)
Lacrimal Punctum Pores that drain tears from Lacrimal Caruncle into Lacrimal Canaliculi
Lacrimal Canaliculus Drainage ducts to Lacrimal Sac
Lacrimal Sac Temporary storage of Lacrimal secretions
Nasolacrimal Duct Drainage of secretions into nose
Anterior Cavity of the Eye is filled with: Aqueous Humor
Aqueous Humor is produced by: The Ciliary Processes
The Ciliary Processes secrete Aqueous Humor at the rate of ____ micro liters a minute 1-2 micro liters per minute
Functions of Aqueous Humor It is watery like the CSF; Responsible for nutrient and waste transport; Fluid cushion
Location of the Anterior Chamber Cornea to the Iris
Anterior Cavity of the Eye is divided into: The Anterior Chamber (from Cornea to Iris) and the Posterior Chamber (Iris to the Ciliary Body and Lens)
Location of the Posterior Chamber Iris to the Ciliary Body and Lens
Posterior Cavity of the Eye is filled with: Vitreous Body
Vitreous Body is produced when? In Utero (not regenerated once you are grown)
Properties of Vitreous Body Collagen and proteoglycan rich
Function of Vitreous Body Helps maintain the shape of the eye
Flow of Aqueous Humor: Produced in Posterior Cavity (Vitreous Chamber) → Flows into Anterior Cavity through Pupil → Drains through Canal of Schlemm → Enters the veins in Sclera
Canal of Schlemm Drains Aqueous Humor into the veins in the Sclera
___% of the U.S. population has Glaucoma 1-2%
Glaucoma is the ___% worldwide cause of blindness (number 2) 12%
Glaucoma occurs in people > ____ years, especially people >____ years 35, 65
Glaucoma Increased intraocular pressure due to Aqueous Humor not draining properly; Results in damage to the optic nerve which changes action potentials; Can lead to blindness if untreated
Sclera is _________, not like a balloon Fibrous
What is the weakest part of the Sclera? Optic Disc
What does distorting the Optic Nerve do? Causes changes in action potentials which can lead to blindness
Topical Treatment for Glaucoma Beta-Blockers (decrease Aqueous Humor production) and Muscarinic Agonists (constrict the pupil which increases drainage)
How do topical Beta-Blockers treat Glaucoma? They decrease production of Aqueous Humor
How do topical Muscarinic Agonists treat Glaucoma? They constrict the pupil which increases drainage
Surgical Treatment for Glaucoma Repeatedly perforateing the wall of the Anterior Chamber, which increases drainage
Three Layers of the Eye 1. Fibrous Tunic 2. Vascular Tunic 3. Neural Tunic
Fibrous Tunic The layer of the Eye responsible for support and protection; Attachment site for extrinsic muscles; Assists in focusing
Which layer of the Eye is the attachment site for extrinsic muscles? Fibrous Tunic
Which layers of the Eye are responsible for focusing? Vascular Tunic and Fibrous Tunic (assists)
Which layer of the Eye is for support and protection? Fibrous Tunic
The Fibrous Tunic is made up of what structures? Cornea, Limbus, Sclera
Vascular Tunic Blood and lymphatic connection; Regulates light entering the eye; Homeostasis of Aqueous Humor; Focusing
Which layer of the Eye is the blood and lymphatic connection? Vascular Tunic
Which layer of the Eye regulates light entering the Eye? Vascular Tunic
Which layer of the Eye is responsible for the homeostasis of the Aqueous Humor? Vascular Tunic
The Vascular Tunic is made up of what structures? Ciliary Body, Ciliary Process, Iris, Choroid
Neural Tunic Detects light and color; Relays visual information to Brain
Which layer of the Eye detects light and color? Neural Tunic
Which layer of the Eye relays visual information to the Brain? Neural Tunic
The Neural Tunic is made up of what structures? Ora Serrata, Retina
Sclera White of the Eye; Dense connective tissue (collagen and elastic fibers); Insertion point of the extrinsic Eye muscles; Small blood vessels; Anterior surface covered with the Ocular Conjunctiva
What type of tissue is the Sclera? Dense connective tissue (collagen and elastic fibers)
What is the thickest part of the Sclera? The posterior
What is the thinnest part of the Sclera? The anterior
What is the insertion point of the extrinsic Eye muscles? Sclera
What is the anterior surface of the Sclera is covered with? Ocular Conjunctiva
Limbus Border between Cornea and Sclera
Cornea Continuous with Sclera, BUT is made of collagen fibers; Transparent; No blood vessels; Covered with corneal epithelium; Continuous with but distinct from the Ocular Conjunctiva; Many nerve endings
What type of tissue is the Cornea made of? Collagen fibers (transparent)
The Sclera has ___________ but the Cornea has none Blood Vessels
The Cornea is covered with corneal epithelium which is continuous with, but distinct from, the __________. Ocular Conjunctiva
Iris Colored part of the eye; Contains blood vessels and melanocytes; Have Pupillary Muscles that constrict or dilate the Pupil
A lack of melanocytes in the Iris makes it what color? Blue, Gray
An abundance of melanocytes in the Iris makes it what color? Green, Brown, Black
Two Pupillary Muscles 1. Constrictor (Concentric) – contraction leads to decreased Pupil size 2. Dilator (Radial) – contraction leads to increased Pupil size
Contraction of the Constrictor (Concentric) Pupillary Muscles leads to __________ Pupil size Decreased
Contraction of the Dilator (Radial) Pupillary Muscles leads to ____________ Pupil size Increased
Location of the Choroid Lies between Fibrous and Neural Tunics in the posterior portion of the Eye (posterior to the Ora Serrata)
Functions of the Choroid Delivers oxygen and nutrients to the Retina; Contains melanocytes (particularly near the Sclera) that keep extra light out
What delivers oxygen and nutrients to the Sclera? Choroid
Ciliary Body is composed of: Ciliary Muscles and Ciliary Processes (Suspensory Ligaments aid these structures)
Functions of Ciliary Body Connects the Iris to the Choroid
What type of tissue is the Ciliary Body made of? Epithelia-covered Muscle Tissue
Ciliary Muscle Sphincter muscle; Contraction of the muscle leads to relaxation of Suspensory Ligaments on Lens; Relaxation of the muscle leads to tension in Suspensory Ligaments on Lens
Contraction of the Ciliary Muscle leads to ____________ of the Suspensory Ligaments on the Lens Relaxation
Relaxation of the Ciliary Muscle leads to ____________ in the Suspensory Ligaments on the Lens Tension
Ciliary Processes Folds of epithelia that cover the Ciliary Muscle; Secrete Aqueous Humor
What covers the Ciliary Muscle? Ciliary Processes
Suspensory Ligaments Attach the Lens to the Ciliary Process; Holds Lens in place behind Pupil
What attaches the Lens to the Ciliary Processes? Suspensory Ligaments
What holds the Lens in place behind the Pupil? Suspensory Ligaments
Two Layers of the Retina 1. Neural Layer 2. Pigmented Layer
Neural Layer of the Retina Thick inner layer; Light passes through; Contains Photoreceptors, supporting cells, and neurons; Preliminary processing of information; Extends to the Ora Serrata
Which layer of the Retina is thicker? Neural Layer
Which layer of the Retina does light pass through? Neural Layer
Which layer of the Retina contains Photoreceptors? Neural Layer
The Neural Layer of the Retina extends to the ____________. Ora Serrata
Pigmented Layer of the Retina Thin outer layer; Contains melanocytes; Absorbs light; Close proximity to the neural part; Extends over Ciliary Body and Iris
Which layer of the Retina is thinner? Pigmented Layer
Which layer of the Retina is the inner layer? Neural Layer
Which layer of the Retina is the outer layer? Pigmented Layer
Which layer of the Retina contains melanocytes? Pigmented Layer
Which layer of the Reina absorbs light? Pigmented Layer
The Pigmented Layer of the Retina extends of the ___________ and the ___________. Ciliary Body and Iris
Red Reflex Shining a light into your eye should result in glowing, red eyes
Glowing animal eyes are due to: The Tapetum Lucidum (highly reflective layer behind the Retina that aids with night vision)
Tapetum Lucidum A highly reflective layer behind the Retina in animals that aids with night vision
The good of having a Tapetum Lucidum: Better vision in low light conditions
The bad of having a Tapetum Lucidum: Poorer vision in high light conditions
Eye vasculature is extremely fragile and can help with early detection of: Neurovascularization, Arterosclerosis, Hypertension
Detaches Retina Retinal tear allows Vitreous Body to seep between the Neural and Pigmented Layers
Symptoms of a detached Retina: Flashes, Floaters, Curtains
Causes of a detached Retina: Age, Glaucoma, Head trauma, Genetics, Diabetes, Myopia
Treatment for a detached Retina: Heat or freeze the tear (although the scar tissue will be a blind spot); Inject air into Posterior Cavity
What will heating of freezing a retinal tear cause? Scar tissue which is a blind spot
Diabetic Retinopathy affects ___% of diabetics (who are diabetic for > 15 years) 80%
Diabetic Retinopathy causes ___% of worldwide blindness (number 5) 5%
___________ damages the blood vessels in the Retina which causes Diabetic Retinopathy Hyperglycemia
Damage to blood vessels in the Retina leads to leakage of ________ and/or _________ into the Posterior Cavity Blood and/or Lipids
Diabetic Retinopathy Hyperglycemia damages blood vessels in Retina; Blood and/or lipids leak into Posterior Cavity; Deprivation of vital nutrients to Retina; Angiogenesis (growth of blood vessels) into space between Neural and Pigmented Layers
Symptoms of Diabetic Retinopathy Transient blurred vision, Floaters, Loss of vision (blind spots, loss of color), Blindness
Treatment of Diabetic Retinopathy Vitrectomy (removal of some or all of the Vitreous Humor), Cauterize blood vessels, Corticosteroid injections
Location of Photoreceptors Located in Neural Layer but loosely embedded in Pigmented Layer
Types of Photoreceptors 1. Rods (Detect light) 2. Cones (Color vision)
Function of Rods Detect light (photons); Can function in dim light
Function of Cones Color vision (wavelength of photons); Need more light, sharper image
Accessory Neurons in the Neural Layer of Retina Bipolar Cells, Ganglion Cells, Horizontal and Amacrine Cells
Function of Bipolar Cells Synapse with Rods and Cones
Function of Ganglion Cells Synapse with Bipolar Cells; Axons form Optic Nerve
The Optic Nerve is made of axons from which cells? Ganglion Cells
Function of Horizontal Cells Connect the synapses of Photoreceptors and Bipolar Cells; Stimulate or inhibit communication between them; Play an important role in adjusting to a dim or brightly lit environment
Function of Amacrine Cells Connect the synapses of Bipolar Cells and Ganglion Cells; Stimulate of inhibit communication between them; Play an important role in adjusting to a dim or brightly lit environment
Which cells connect the synapses of Photoreceptors and Bipolar Cells? Horizontal Cells
Which cells connect the synapses of Bipolar Cells and Ganglion Cells? Amacrine Cells
Which cells play an important role in adjusting to a dim or brightly lit environment? Horizontal Cells and Amacrine Cells
Features of the Retina: Optic Disc, Macula (Lutea), Fovea (Centralis)
Optic Disc The place where axons from 1 million ganglia converge; Origin of Optic Nerve (Cranial Nerve II); Retinal Artery and Vein enter eye here; No Photoreceptors (blind spot)
What is the origin of the Optic Nerve (Cranial Nerve II)? Optic Disc
Where do the Retinal Artery and Vein enter the Eye? Optic Disc
What is the spot on the Retina called that has no Photoreceptors (Blind Spot)? Optic Disc
How many axons from ganglia converge at the Optic Disc? 1 million
Macula (Lutea) Visual image arrives here after it passes through the Cornea and Lens; About 6 million Cones but 0 Rods
Where does the visual image go after it passes through the Cornea and the Lens? Macula (Lutea)
How many Cones are at the Macula (Lutea)? About 6 million
How many Rods are at the Macula (Lutea)? Zero
Fovea (Centralis) Center of Macula; Greatest concentration of Cones; Sharpest vision
What is the center of the Macula called? Fovea (Centralis)
Where is the greatest concentration of Cones found? Fovea (Centralis) – responsible for sharpest vision
Retinitis Pigmentosa Most common inherited visual abnormality; Visual pigments of discs are abnormal; Gradual destruction of Photoreceptors
What is the most common visual abnormality? Retinitis Pigmentosa (1:3000)
How many different genes have been identified as being linked to Retinitis Pigmentosa? 35 different genes
What is the ratio of children born with Retinitis Pigmentosa? 1:3000
How many mutations in Rhodopsin have been found in Retinitis Pigmentosa? 100
Symptoms of Retinitis PIgmentosa Night blindness → Tunnel vision → Blindness
Retinitis Pigmentosa progresses from ________ to _________. Childhood to 40s
Treatment for Retinitis Pigmentosa Vitamin A can slow the progression
Macular Degeneration Leading cause of blindness in the U.S. (> 50 yrs); Neural Tunic components may separate; Loss of central vision around Fovea; Blindness (especially if “dry”)
What is the leading cause of blindness in the U.S.? Macular Degeneration
Macular Degeneration is responsible for __% of blindness cases worldwide (number 3) 9%
Types of Macular Degeneration ”Dry” and “Wet”
“Dry” Macular Degeneration Cellular debris (damaged photoreceptors, etc) build up around Fovea and surrounding Macula; Loss of Photoreceptors in Macula; Less damaging, but no treatment (antioxidants slow it)
“Wet” Macular Degeneration Abnormal vascular growth at Macula; Bleeding, leaking, and scarring which causes damage to Photoreceptors; Treatment is laser surgery, Avastin (anti-VEGF [vascular endothelial growth factor] = anti-angiogenesis)
___% of Macular Degeneration is the “Dry” type 85%
___% of Macular Degeneration is the “Wet” type 15%
Which type of Macular Degeneration is less damaging? ”Dry”
Which type of Macular Degeneration has no treatment? ”Dry”
Which type of Macular Degeneration results in a loss of Photoreceptors at the Macula? ”Dry”
Which type of Macular Degeneration involves abnormal vascular growth at the Macula? ”Wet”
Which type of Macular Degeneration is more likely to result in blindness? ”Dry”
Treatment for “Wet” Macular Degeneration Laser surgery; Avastin (anti-VEGF = anti-angiogenesis)
Avastin Anti-VEGF (vascular endothelial growth factor) = anti-angiogenesis; used to treat “Wet” Macular Degeneration
Photoreceptors are made up of: Outer Segments of Neural Part (which contains Discs), Inner Segment of Neural Part, Synaptic Terminal
Discs Part of Photoreceptors (in the Outer Segment of Neural Part): Contain visual pigments that absorb photons (Retinal and Opsin); Rod discs have more pigment, which means they have greater photosensitivity
Where are the visual pigments that absorb photons located? Discs (part of Photoreceptors)
What two pigments absorb photons? Retinal (molecule derived from Vitamin A) and Opsin (Protein)
Retinal Visual pigment that is derived from Vitamin A; Found in Discs in Photoreceptors
Opsin Visual pigment that is a protein; Found in Discs in Photoreceptors
Which type of Photoreceptors have more pigment (dominant Photoreceptor)? Rods: greater photosensitivity
Outer Segment of Neural Part Part of Photoreceptor that contains Discs; Old Discs are phagocytized by pigment epithelium cells of the Pigmented Layer (they recycle Retinal)
Why don’t you have to do tissue matching when doing Cornea transplants? Because there are no blood vessels there that would bring in white blood cells
Where is Retinal recycled? In the Outer Segment of Neural Part
Inner Segment of Neural Part Contains organelles and metabolic machinery; Photopigment synthesis
Where does photopigment synthesis occur? Inner Segment of Neural Part
Synaptic Terminal The place where Photoreceptors synapse with Bipolar Cells; Photoreceptors release neurotransmitters
Where do Photoreceptors release neurotransmitters? Synaptic Terminal
How many Rods are in the Eye? 125 million
How many Cones are in the Eye? 6 million
Where are the Rods predominantly located? Periphery of the Retina
Rods are responsible for ________ vision Achromatic (non-color) vision
Where are Cones predominantly located? Macula Lutea and particularly in the Fovea
Cones are responsible for ________ vision Color vision
Achromatic vision is Retinal + __________ Rhodopsin
Color vision is Retinal + __________ Photopsin (SWS2 = blue, MWS = green, LWS = red)
___% of Cones are Blue Cones 16%
___% of Cones are Green Cones 10%
___% of Cones are Red Cones 74%
Blue Cones are Retinal + ____ Photopsin SWS2
Green Cones are Retinal + ____ Photopsin MWS
Red Cones are Retinal + ____ Photopsin LWS
Color Blindness Sex-linked recessive disease; Varying types, depending on which Opsins have decreased sensitivity or complete absence
___________ variants are more common than ___________ variants Red/Green are more common than Blue
___% of Males are Colorblind 10%
___% of Females are Colorblind < 1%
Photoreceptrion in Darkness Converts photons into electrical energy; “Resting” membrane potential of Photoreceptors is -40mV
What is the “Resting” membrane potential of Photoreceptors in the dark? -40mV
What happens in the Outer Segment in the dark? Na+ channels are open, Na+ enters Outer Segment; cGMP opens gated Na+ channels
What happens in the Inner Segment in the dark? Continuously pumps Na+ out
Dark Current Movement of Na+ ions
What happens at the Synaptic Terminal in the dark? Depolarization and release of Glutamate
A photon strikes the retinal portion of an _________ molecule in a Disc Opsin
Photon converts ______ Retinal to ______ Retinal 11-cis Retinal to 11-trans Retinal
Once 11-cis Retinal is converted by a photon to 11-trans Retinal, Opsin activates ________ (G-Protein) which then activates ____________. Opsin activates Transducin (G-Protein) which then activates Phosphodiesterase (PDE)
Phosphodiesterase (PDE) Activated by Transducin; Converts cGMP (which opens Na+ channels in the Outer Segment) to GMP which causes the Na+ channels to close → Decrease in Na+ entering the Outer Segment
PDE converting cGMP to GMP causes: Gated Na+ channels to close → Decrease in Na+ entering the Outer Segment
Na+ is pumped out of the __________ Segment even in light Inner
Na+ being pumped out of the Inner Segment reduces _________ and causes hyperpolarization of the Photoreceptor (___ mV) which decreases Glutamate release Reduces dark current; -70 mV
Hyperpolarization of a Photoreceptor makes the membrane potential of the Photoreceptor ___ mV -70 mV
Na+ being pumped out of the Inner Segment results in ___________ Glutamate release Decreased
What kind of cells signal that a photon was detected? Bipolar Cells
Does Retinal spontaneously revert back to 11-cis form? No, ATP is required to convert it back
Photoreceptors can’t respond to subsequent photons until _____________ molecules regenerate Rhodopsin/Photopsin
Rhodopsin/Photopsin is composed of: Retinal + Opsin
____ is required to convert 11-trans Retinal back to 11-cis Retinal ATP
____ levels gradually build up during the recovery period due to inactive Opsin and dark current is reestablished cGMP
Bleaching When Photoreceptors can’t respond to subsequent photons until Rhodopsin/Photopsin molecules regenerate
Lingering visual impressions after a flash of light are an example of what? Bleaching
How do we adapt to brint light? Bleaching followed by gradual regeneration of Rhodopsin/Photopsin
Rhodopsin is found in _______ and Photopsin is found in ________. Rhodopsin found in Rods, Photopsin found in Cones
Functions of Lens Focuses visual image on Photoreceptors by changing shape
Location of Lens Posterior to Iris; Held in place by Suspensory Ligaments at Ciliary Body
The Lens is made up of: Concentric layers of cells surrounded by a capsule
_______ and ________ are absent in Lens fibers Nuclei and organelles
Lens fibers contain _________ (proteins) that provide clarity and focusing power Crystallins
Crystallins Proteins found in Lens fibers that provide clarity and focusing power
The Lens capsule is made up of: Elastic and collagen fibers that intermesh with Suspensory Ligaments of Ciliary Body
Light is refracted at ___ interface(s) Two: Air/Cornea and Aqueous Humor/Lens
When an image is ‘in focus,’ light is refracted to produce: A single, clear image on the Retina
An image is ___________ and ___________ on the Retina Inverted and Reversed
What does an object appear as on the Retina? Numerous, individual points of light
The top of an image lands on the ________ of the Retina Bottom
The bottom of an image lands on the ________ of the Retina Top
The left of an image lands on the ________ of the Retina Right
The right of an image lands on the ________ of the Retina Left
Brain compensates for image __________ and ___________. Inversion and Reversal
20/20 Emmetropia (what a normal person can see at 20 feet)
Emmetropia What a normal person can see at 20 feet
20/15 What a normal person can see at 15 feet is seen at 20 feet (better than 20/20)
20/200 What a normal person can see at 200 feet is seen at 20 feet (worse than 20//20)
Legally Blind means that corrected vision is worse than: 20/200
20/200 is ____ diopters -2.50
The Ciliary Muscle contracts to focus on ________ objects Close
When the Ciliary Muscle contracts, the Lens becomes _________. Rounder
What happens to the Ciliary Body when the Ciliary Muscle contracts? The Ciliary Body moves toward the Lens and reduces tension in Suspensory Ligaments; makes a rounder Lens; ability to focus on close objects
The Ciliary Muscle relaxes to focus on ________ objects Distant
When the Ciliary Muscle relaxes, the Lens becomes __________. Flatter
What happens to the Ciliary Body when the Ciliary Muscle relaxes? The Ciliary Body moves away from the Lens and increases tension in Suspensory Ligaments; makes a flatter Lens; ability to focus on distant objects
Myopia Near-sightedness (Focus in front of Retina)
Causes of Myopia (near-sightedness) Eyeball is too ‘deep’ or Lens is too round
Hyperopia/Presbyopia Far-sightedness (Focus behind Retina)
Causes of Hyperopia/Presbyopia Eyeball is too ‘shallow’ or Lens is too flat
The Lens is less elastic and has weaker muscles in people with __________. Hyperopia/Presbyopia (Far-sightedness)
Astigmatism Misshapen Cornea; Light focused on 2 spots on Retina which causes a blurry image
Treatements for Myopia, Hyperopia/Presbyopia, Astigmatism Corrective lenses (glasses, contacts); Surgery to reshape Cornea
Cataracts Denaturing of crystallin protein in Lens
Cataracts cause ___% of blindness worldwide (number 1) 50%
Causes of Cataracts Genetics, radiation, aging
Symptoms of Cataracts Loss of visual, ‘halos,’ impaired color vision
In Cataracts, crystallin protein in Lens can “liquefy” over time which can cause the Lens capsule to ________. Rupture
Treatments of Cataracts High frequency sound waves break up denatured protein, remove proteins but leave lens capsule, implant new lens
Visual Pathway (Eyes to Brain): Photoreceptors → Bipolar Cells → Ganglion Cells → Optic Nerve
How many photoreceptors in the Eye? 130 million
How many Bipolar Cells in the Eye? 6 million
How many Ganglion Cells in the Eye? 1 million
There are ______ Rods per every 1 Ganglion Cell (M Cell) 1000
Rods go to which Ganglion Cells? M Cells; M Cell activation signals general stimulation; Less acuity due to convergence (on center neurons respond more strongly than off center neurons)
In the Fovea, there is _____ Cone per every 1 Ganglion Cell (P Cell) 1
Cones go to which Ganglion Cells? P Cells; Greater acuity due to lack of convergence (1:1 ratio)
Information from only the _________ fields of each eye crosses over at the Optic Chiasm Peripheral (Lateral)
Information from the _________ field does not cross over at the Optic Chiasm Central
Crossing over of information at the Optic Chiasm allows for: Binocular vision and depth perception
Binocular vision and depth perception are possible because: Information crosses over at the Optic Chiasm
Impulse from Optic Tract proceeds to which 3 regions in the Brain? 1. Lateral Geniculate Nuclei in Thalamus (one on each side) 2. Superior Colliculi in Midbrain (sent here from Lateral Geniculate) 3. Suprachiasmatic Nuclei in Hypothalamus (sent here from Lateral Geniculate)
Lateral Geniculate Nuclei (in Thalamus) send Optic Radiation on to ________ for interpretation of images Occipital (visual) Cortex
Lateral Geniculate sends visual information to the ___________ in the Midbrain to coordinate Eye movement, papillary reflexes (Melanopsin), etc Superior Colliculi
Lateral Geniculate sends visual information to the ___________ in the Hypothalamus to control circadian rhythm (Melanopsin) and cortisol production Suprachiasmatic Nuclei
Created by: Cyndi1087