Term
| What are the accessory structures of the eye? |
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Definition
- Eyebrows - protective
- Eyelids/palpebrae - blinking
- Conjunctiva - transparent mucous membrane lines eye to moisturize
- Lacrimal apparatus
- Extrinsic eye muscle
**Ciliary gland - oily secretions, site of sty. Caruncle - lubricates. Sleepy tears |
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Term
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Definition
Inflammation of the conjunctiva
- Bacterial - thicker discharge
- Viral - watery
- Allergic - itchy |
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Term
| What are styes and chalazions? |
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Definition
- Stye - inflammed ciliary gland
- Chalazion - tarsal gland
Tx: Warm compress |
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Term
| What is the lacrimal apparatus? |
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Definition
Consists of the lacrimal gland, produces tears at constant rate. PNS Stimulation by CN 7 - empty into nasolacrimal duct to enter nasal cavity
**alpha1, M2/M2 receptors |
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Term
| What are extrinsic eye muscles? |
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Definition
- 4 rectus muscles
- 2 oblique muscles
- Diplopia - double vision from paralysis
- Strabismus - wandering eye from muscle weakness |
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Term
| What are the 3 layers of the eye? |
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Definition
- Fibrous - outer. Also called Sclera
- Vascular/uvea - Also called Choroid
- Inner/Retina |
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Term
| What are the parts of the fibrous layer of the eye? |
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Definition
- Sclera - protects/shapes, anchor for extrinsic eye muscle
- Cornea - light enters eye, avascular |
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Term
| What are the parts of the vascular layer of the eye? |
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Definition
- Choroid - nutrients, absorbs light
- Ciliary body - produces aqueous humor, holds and shapes lens
- Iris - Colored, contraction changes shape of pupil. Myosis (constriction of circular muscles) or mydriasis (dilation by radial muscles) |
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Term
| How does the pupil constrict and dilate? |
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Definition
- Circular muscles - PNS, in bright light. Pinpoint pupils (Miosis)
- Radial muscles - SNS, in dim light = dilated pupils (mydriasis) |
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Term
| What are the parts of the Inner layer of the eye? |
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Definition
- Pigmented layer - absorbs light, stores Vit A, clears dead cells
- Neural layer - light to chemical energy. Optic disc - optic nerve leaves the eye. Blood from choroid, central artery/vein |
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Term
| What divides the anterior and posterior chambers? |
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Definition
The iris
- Aqueous humor in posterior chamber gets to anterior through pupil. Maintains IOP |
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Term
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Definition
- epithelium (outer lens) --> fibers, made up of crystallins
- Refracts light onto retina |
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Term
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Definition
| Focusing on close objects - ciliary muscles contract causing the lens to bulge |
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Term
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Definition
| Clouding of the lens caused by crystallin clumping - nutrients not delivered to deep lens fibers |
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Term
| What is contained in the posterior segment? |
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Definition
| Vitreous humor - maintains shape, prevents retinal detachment |
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Term
| How is color detected by the eye? |
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Definition
- Rods - grey tones. Sensitive to dim light. Several to one ganglion
- Cones - color 400-700 nm. Need bright light. 1:1 cone to ganglion
- Bipolar cells - transports signal to ganglion cells
- Ganglion cells - generate AP. Die in glaucoma and blindness
- Interneurons - modify signals from photoreceptors. Horizontal - between photo and bipolar. Amacrine - between bipolar and ganglion |
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Term
| How are rods/cones distributed in the retina? |
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Definition
- Macula lutea - mostly cones, lateral to optic disc
- Fovea centralis - only cones
- Retina periphery - rod density increases |
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Term
| What is the visual pigment Rhodopsin? |
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Definition
- In rods: contain retinAL (absorbs light) and Opsin (determines wavelength)
- Light enters, 11-cis retinal converted to trans-retinal activating rhodopsin. PDE breaks down cGMP--> GMP leading to hyperpolarization
- Rest: Na/Ca influx, glutamate inhibits bipolar cells: No synapse w/ ganglion cells
**Similar for cones, which use iodopsin |
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Term
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Definition
| Congenital lack of 1+ cone type: X-linked, most common is red-green |
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