Term
| Is the Corneal Epithelium Hydro or Lipophillic? Stroma? Endothelium? What does this imply concerned the best composition of pH for opthalmic drops? |
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Definition
Lipo - Hydo - Lipo = Non - ionized - Nonionized
The best composition of opthalmic drops is a weak base |
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Term
| What makes the corneal stroma highly hydrophillic |
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Definition
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Term
| Where does the Corneal epi get its glucose? What causes mild amounts of corneal edema after sleep? |
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Definition
Glucose mostly comes from aqueous. Minor contributions from tears and limbal capillaries.
Glucose goes through lactic acid cycle during sleep due to lack of oxygen, lactic acid them accumulates in the stroma and water follows --> edema in AM |
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Term
| What percent of light above 400 nm is transmitted through the cornea |
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Definition
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Term
| Photokeratits occurs due to UV exposure. We are most sensitive to radiation in what range |
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Definition
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Term
| Do lamellae run parallel or perpendicular to the corneal surface? Why is transparency maintained |
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Definition
Parallel.
Transparency maintained because fibril are spaced perfectly < one half wavelength of visible light apart = destructive interference . SIZE AND SPACING most imp --> proteoglycans responsible for maintaining the spacing |
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Term
| Movement of what molecule into the aqueous stimulates release of what molecule into the tears which dehydrates the cornea? |
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Definition
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Term
| Which channel responds to corneal changes in pH which allows normal corneal thickness after contact lens wear |
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Definition
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Term
| Where does the conrea get its oxygen from an open eye? Closed eye? |
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Definition
Open -- tears 155mmHg
Closed-- front from lids and the back from the aqueous |
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Term
| What is the natural process for conreal regeneration? |
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Definition
| Basal cells under go mitosis --> differentiate into wing wells --> squamous cells --> old cells slough off. Regenerates itself every 7 days |
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Term
| What happens in traumatic injury to the cornea? |
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Definition
1. Basal cell mitosis stops
2. migrate to wounded area
3.mitosis occurs @ rapid rate |
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Term
| What dioptric power does the lens contribute? What is the max amp of accommodation the lens can provide, reached between the ages of 8-12 |
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Definition
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Term
| What varies among the lens which provides a refractive index gradient higher in the nucleus than outer cortical surface? What are these n values |
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Definition
Protein varies
Nucleus = 1.50, Outer cortical = 1.37, Aqueous and Vitreous humor = 1.336 |
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Term
| What 2 lens factors work to reduce spherical aberration |
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Definition
| Gradient index system, peripheral flattening |
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Term
| Which crystallin acts as a chaperone by helping chains revert back to original shape |
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Definition
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Term
| What happens with age to the crystallins to make them less effective at maintaining lens transparency |
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Definition
| go from water soluble to water insoluble |
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Term
| Are amino acids in higher concentrations in the lens or aqueous? vitreous v. plasma? |
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Definition
Higher in lens than aqueous
Higher in plasma than vitreous |
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Term
| How does glutathione help/protect the lens |
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Definition
| It works as a reducing agent that detoxifies free radicals to protect the lens from oxidation. Free radicals from from UV light |
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Term
| Is calcium or Vitamin C (ascorbic acid) high in the lens |
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Definition
| Vitamin C. Calcium is 50x less than in aqueous humor and harms the lens, it increases with age and causes formation of cataracts |
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Term
| Where are all the pumps located to keep water out of the lens and to perform the metabolic tasks of the lens? |
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Definition
| Lens epithelium. Need lots of pumps in the lens because it has the largest percent of protein in the body so it needs lots of glucose and oxygen. It has a Na/K pump that needs ATP to dehydrate the lens |
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Term
| What enzyme is needed for the first step of either aerobic or anaerobic pathway? |
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Definition
| Hexokinase. Is not available -- glucose converted to sorbita via aldose reductase which can cause lens swelling = diabetic cataract |
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Term
| What 4 factors contribute to the lens transparency |
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Definition
1. lack membrane bound organelles
2. closely backed with consistent distances
3. Crystallins minimize light scatter by destructive interference
4. avascular, no nervous supply |
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Term
| Y sutures demarcate which nucleus |
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Definition
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Term
| Which layer of the ciliary body provides the uveoscleral outflow pathway |
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Definition
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Term
| What optical aberrations does a small pupil reduce? What does a small pupil act to increase? |
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Definition
Decreases: Spherical aberration, chromatic aberration
Increases: depth of field |
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Term
| The sphincter muscle is parasympathetic or sympathetic? Dilator muscle? |
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Definition
| Sphincter = para, Dilator = sympathetic |
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Term
| Which layer of the uvea can function to suck edema from the retina? How does it do it? |
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Definition
| Choroid, high a high protein content which forms a gradient |
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Term
| The vitreous acts as a UV filter to decrease transmission of light at what wavelenghts |
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Definition
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Term
| What 2 molecules provide the viscoelastic properties to the vitreous? Why are viscoelastic properties important to the eye |
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Definition
HA + Collagen
Important because the cushion the eye from vibrations and physical damage |
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Term
| Why can topical drugs not reach the retina? |
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Definition
| Gel like consistency of the vitreous |
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Term
| At what age are the gel and liquid equal in composition in the vitreous? WHat causes floaters? Where is the collagen concentration of collagen lowest in the vitreous? Highest? |
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Definition
Age 80
Loss of structure causes pocket of fluid and aggregations of collagen fibrils
Collagen concentration is lowest int he center and highest at the vitreous base = ora serrata |
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Term
| What percent of the vitreous is water? How much of visible light does the vitreous transmit? The vitreous is what percent of the volume of the globe? |
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Definition
| 99% water content; Transmits > 90% of visible light and the vitreous is also 80% of the total volume of the globe |
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