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VisualSystem
Exam 6 - Lecture 3
| Question | Answer |
|---|---|
| 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 |
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Cyndi1087
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