Midterm 2 Flashcards

Cornea. Outermost layer. Transparent and Curved. Refraction and focusing power. Reversible damage is fairly rare but includes short term exposure to high sunlight.

Aqueous Humor. liquid located behind the cornea. source of nutrition for cornea and lens. Made in the ciliary body and trained in the Schlemm’s Canal and trabecular network. Important in glaucoma.

Pupil. The hole in the iris that permits light to enter the eye. It appears black when looking at the eye.

Lens or Crystalline Lens. composed of long, onion-layered prism cells with crysatllin proteins. Transparent and flexible. Connected to the ciliary body by zonular fibers that radiate outward and provide tension. Associated with cataracts.

Iris. Modified portion of the choroid layer. Color part of the eye. Forms the angle associated with glaucoma with the cornea. Two sets of smooth muscle. Set that radiates outward from pupil and are sympathetically innervated (norepinephrine) causing dilation of pupil. Second set circumvents the pupil and are parasympathetically innervated (acetylcholine) and cause constriction of pupil.

Zonular Fibers. Attach the lens to the ciliary body.

Vitreous Body. Usually clear gelatinous layer. Contain “floaters” which are impurities that usually float around. If they are located right above retina will cast a shadow and cause vision disturbances. Sudden changes in floater appearances may indicate a hemorrhage or retinal detachment.

Sclera. outermost layer of eye. modified anteriorly to form the cornea

Choroid. Between the sclera and retina. contains the blood vessels. Blackish-brown to prevent reflection.

Retina. nervous tissue containing rods and cones.

Optic Disk. location where the axons (all are afferent) of the retina converge and exit the eye. Is a blind spot.
Physiology of Glaucoma
Degeneration of afferent axons in the retina near the optic disk due to increased intraocular pressure caused by excessive accumulation of aqueous humor.
Begins with retinal ganglion cell degeneration followed by their cell bodies.
Glaucoma Diagnosis
- Tonometry: measuring tension in the eye. Press against the white of eye to check pressure or you have a machine that blows a puff of air to see the amount of indentation.
- Can look at blood vessels because of changing shape of optic disk
- Retina imaging
Open Angle Glaucoma
90% of glaucoma. Age is biggest risk factor. Slowly and painlessly progresses. Does not cause symptoms until permanent damage has occurred. Cause is improper drainage of aqueous humor.
Closed Angle Glaucoma
more common in younger people. Sudden, painful onset. Iris becomes pushed over against the cornea and the aqueous humor can’t get to the trabecular network. Usually caused with sympathetic innervation causing sudden dilation of pupil. Also have dilated blood vessels around the edge of the cornea. Treatment involves constricting pupil.
Alpha2 Adrenergic Receptors in Glaucoma Treatment
decrease aqueous humor formation at the ciliary body and increase outflow.
Beta Adrenergic Antagonists in Glaucoma Treatment
decrease aqueous humor formation at the ciliary body (in a different mechanism than Alpha2 adrenergic agonists) Example is timolol.
Prostaglandin Analogs in Glaucoma Treatment
Increase the drainage of aqueous humor. Example is latanoprost.
Cholinergic (muscarinic) Agonists in Glaucoma Treatment
decrease aqueous humor formation and constrict the pupil which is used in closed angle glaucoma. Pilocarpine is example.
Carbonic Anhydrase Inhibitors in Glaucoma Treatment
reduces the formation of HCO3 - which in turn reduces solute and thus fluid secretion at the ciliary body.
Laser Trabeculoplasty in Glaucoma Treatment
treatment option where laser is aimed at the trabecular network to increase the flow through the network. Effect is not permanent.
Conventional surgery in Glaucoma Treatment
can be used to create an opening with which the aqueous humor can drain from the eye.
Cataracts Symptoms, Causes and Treatment
Region of the lens becomes cloudy.
- Causes: Biggest cause is age and genetics. Can be promoted by diabetes, UV light exposure, trauma and heavy glucocorticoid use.
- Symptoms include cloudy vision with an increase in glare which produces a halo like affect.
- Completely resolved by surgery: emulsify lens and suck it out then replace with a new custom fitted lens that will also repair any other prior vision problems. New lens cannot accommodate for close-up vision though.
Measuring Focusing Power
diopters are used to measure the focusing power of the lens. 1 diopter has the focusing power of 1 meter. 2 diopters is 1/2 meters etc. The eye is about 1/60th