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82 Cards in this Set
- Front
- Back
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Mitotic activity occurs in which layer of the cornea?
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basal layer of epithelium
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T/F The epithelium plays a role in immunity
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True--it is a physical barrier
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What two layers of the cornea serve as barriers?
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Endothelium & epithelium
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A commonality of both corneal barriers is that they regulate entry of what substance into the stroma?
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H2O
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What is the first step in corneal wound healing?
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mitosis ceases
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What is the most common type of chemical burn?
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Alkaline
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What is an ocular finding after a chemical burn that indicates a poor prognosis?
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neutrophiles are present
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Name three components of the ocular surface.
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Lipid, aqueous, mucin layer, or protein, water & lipids
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Name one way a contact lens alters the ocular surface.
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Reduces O2 permeability
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Does a gas permeable lens or soft contact lens allow more tear exchange?
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Gas Permeable Lens
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Explain evaporative dry eye disease.
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Deficient lipids, meibomian gland dysfunction
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Describe aqueous deficient dry eye disease.
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Hypertonic
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What is the specific type of proprioceptive detector in the eye?
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Palisade Endings
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EOMs have large, medium, or small motor units.
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Small
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What are the major components of a motor unit?
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Muscle fiber + neuron
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What is one reason EOMs are fatigue-resistant?
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light load, eye weighs very little
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When giving botulinum injections for strabismus, how long is the effect expected to last?
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Permanently
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EOMs have unique properties that make them susceptible to which disease?
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Myasthenia gravis
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EOMs have a decrease or increased number of mitochondria compared to other types of skeletal muscle.
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Increased
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Chronic progressive external ophthalmoplegia is characteristic of which mitochondrial disorder?
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mitochondrial myopathy --> Kararn sayers
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What two ocular findings are consistent with CPEO?
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Ptosis and inability to move eyes (mitochondria are ragged and red)
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What is the reflective index of the aqueous?
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1.3332
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In general, is the production of the aqueous or the outflow of the aqueous more variable?
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Outflow, constant (relatively) rate of production
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Why are diffusion and ultrafiltration important in the production of aqueous (although they contribute minimally to overall aqueous production)?
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They form a reservoir in the CBB
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How does water travel into the posterior chamber?
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Follows Na+ from stroma of NPCE
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What reaction does carbonic anhydrase catalyze?
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Formation of bicarbonate
carbonic anhydrase CO2 + H20 --------> HCO3- + H+ |
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The Na-K-ATPase is found in the
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NPCE
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The Na-K-ATPase drives what ion into the posterior chamber?
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Na+
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How does sodium get into the NPCE?
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Na+/H+ exchanger
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Name the three locations that carbonic anhydrase is found in the body.
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Kidney, brain and eyes
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How is the composition of aqueous different from that of plasma?
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1) Lower protein 2) High ascorbate
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What are the two reasons why the aqueous differs in composition from the plasma?
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1) Blood aqueous barrier 2) Active transport
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Why is ascorbate beneficial?
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protects from UV damage
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How does Schlemm's canal contribute to the blood-aqueous barrier?
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Continuous endothelial cells prevent back flow of aqueous
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Name one factor that can disrupt that blood-aqueous barrier?
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Surgery, trauma, inflammation, infection, drugs
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Why is the blood-aqueous barrier important?
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selects the movement of solutes
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Which is higher--the pressure in the capillaries or the intraocular pressure?
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capillaries
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Which is higher--the pressure in the episcleral veins or the IOP?
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IOP
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Name two factors which can obstruct aqueous outflow
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Neovascularization, inflammatory cells, hyphema, traumatic damage
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Which class of glaucoma drugs are considered first-line therapy?
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prostaglandins (enhance uvealscleral outflow + least side effects)
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Why have topical CAIs fallen into disfavor (why are they not first-line therapy for glaucoma?)
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Side effects including metallic taste and corneal swelling
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Oxidative stress causes the generation of ________ that are damaging to the lens.
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Free radicals (ROS)
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What specific adaptation does the lens employ to minimize damage from oxidative stress?
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It is a reducing structure
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The highly layered structure of the lens poses what type of problem?
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Decreased metabolism centrally
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How do the proteins within the lens differ from other proteins within the body?
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Proteins within the lens are the oldest
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What effect does lactic acid have on the interior of the lens
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Lowers pH (affects metabolism and enzymes)
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Name two noteworthy things about NSC?
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1) Most common 2) Myopic shift
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Which area of the lens do cortical cataracts typically affect?
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Inferior nasal
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Anterior polar cataracts are usually congenital or age related?
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Congenital
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Oral steroids have the propensity to cause which type of cataract?
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Posterior subcapular cataract (PSC)
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What is a hypermature cataract called?
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Morgagnian
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Which enzyme is probably active in the formation of diabetic cataracts?
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aldose reductase
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What is the pathophysiology of posterior capsule opacification?
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Damage from high glucose levels
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Is the near triad an entity of which we have control?
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No
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What effect will the introduction of a -3.00 lens have on a person's visual system
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Stimulate accommodation
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According of Duane, on average a person loses ______ diopters of accommodation per decade
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2.3 diopters/decade
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Explain absolute presbyopia
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Zero accommodation left
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How many diopters of accommodation do we have in youth?
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15 diopters
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By age 50, most people have about _______ diopters of accommodation left.
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1D left
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What structure coordinates the actions of the near triad?
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EW nucleus
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Name the three functions of the pupil.
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1) Depth of focus 2) Reduce aberrations 3) Controls retinal illumination
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What is the range of pupil size (in log units)?
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12 log units
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Why is miosis sometimes beneficial in visual function?
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Increases depth of focus
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Why is pupil size a consideration in refractive surgery?
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Large pupil can cause glare
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If someone has advanced glaucoma in both eyes, will they have an APD?
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No because it is relative to the other eye
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You are studying for ocular physiology and someone drops a medical dictionary behind you, startling you. What is the effect on your pupil size?
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Pupil gets bigger (sympathetic)
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A patient is undergoing a liver transplant---you life the lid and notice the pupil is___
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Anesthsia, miotic
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What symptom would a patient with a fixed pupil potentially have?
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Photophobia
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You are living it up at Salty's and you notice someone with markedly dilated pupils. What is one possible cause?
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Ecstasy, cocaine, heroine
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What are direct and consensual responses equal in humans but not in rabbits?
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Equal vs. varied innervation of pathways b/w brain and eyes
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Why are pupils affected early on in aneurysms of the Circle of Wilis?
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Most aneurysms affect te ICA, which supplies the Ophthalmic artery, which supplies the eye
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The ciliary ganglion is most important in sympathetic or parasympathetic innervations
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Parasympathetic
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Which nerves supply the iris sphincter?
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CN III (more specifically the short ciliary nerve)
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Which muscle is strongest, the dilator or sphincter?
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Sphincter
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The second neuron in the sympathetic chain is considered pre- or post-ganclionic
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Preganglionic
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Where does the first neuron in the sympathetic chain synapse?
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Lateral column of spinal cord (C7-T2)
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Where does the second neuron in the sympathetic chain synapse?
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Superior cervical ganglion
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Which nerves supply the iris dilator?
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Long ciliary nerves
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Describe humoral influences
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Elements of the blood
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Which APD is more sever: a 0.3 log unit defect or a 3.0 defect?
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3.0 log defect
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If a patient has an interruption of parasympathetic flow, when will the defect be most noticeable?
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During the day. --The pupil can't constrict!
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What is the classic triad in Horner's syndrome?
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Ptosis, miosis, anhidrosis
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