Opticianry and Contact Lenses

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Opticianry and Contact Lenses
2013-10-29 13:01:03
COA ophthalmic ophthalmologic ocular eye refractometry lens

Ophthalmic Medical Assisting 5th ed. Chapters 12 and 14
Show Answers:

  1. 4 functions contact lenses must perform
    • Maintain corneal temperature
    • Metabolize waste
    • Oxygenate the cornea
    • Sustain integrity of corneal epithelium
  2. Pantoscopic angle
    Difference between top & bottom of eyeglass frame in relation to patient's face
  3. Retinopathy of prematurity
    Neovasularization of retina due to high oxygen levels in neonatal incubator
  4. Kestenbaum's Rule: purpose and calculation
    • To determine magnification necessary to read newsprint / J5
    • Reverse Snellan score (ie 20/200 --> 200/20 = +10 D)
  5. How to determine vision between 20/400 and CF & how to record in chart
    • Hold printed card 10' away, keep halving distance until ≥half of a line can be discerned
    • Distance in feet over Snellan score denominator (ie 5/150)
  6. Segment Height
    Distance from bottom of eyeglass rim & top of multifocal lens segment
  7. How to calculate focal length (2 ways)
    • Distance (in meters, in decimal form) x lens power
    • Lens power ÷ distance (in meters, expressed as fraction)
  8. LP with projection vs. without projection
    • With projection: Can tell which quadrant light is coming from (test all 4 and record in chart)
    • Without projection: Cannot determine angle of light
  9. Definition of legal blindness
    ≤20/200 or ≤20° VF
  10. Onchocerciasis
    African river blindness
  11. Xerophthalmia
    low vision due to Vit A deficiency
  12. Typical placement of bifocal and trifocal segment
    • Bifocal: top of segment level with lower lid margin
    • Trifocal: Approx. 7 mm above lid margin
  13. Orthophoric
    Normal eye alignment; straight in the primary gaze
  14. Prismatic effect
    Visual distortion caused when distance between optical centers doesn't match patient's PD
  15. Parallax
    Optical distortion when the patient's line of sight is not parallel to that of person taking measurements
  16. 2 types of interpupillary distance (PD) measurement
    • Binocular: from center of right pupil to center of left pupil
    • Monocular: from center of each pupil to center of bridge of nose
  17. Vertex distance
    Distance from front of cornea to back of eyeglass lens (13.5 average, ideally as close as possible without touching lashes)
  18. Instrument to measure vertex distance (2 names)
    • Distometer
    • Vertometer
  19. Base curve (eyeglasses)
    Curve on outer surface of blank lens
  20. Instrument to measure base curve (eyeglasses)
    Geneva lens clock
  21. Optical center
    Point on lens through which light rays are perfectly parallel
  22. 6 eyeglass lens coatings: name & purpose
    • Photochromic: tint increases as light level increases
    • Polarized: glare reduction
    • Antireflective: increases light transmission through lens by decreasing reflection off of lens
    • Hydrophobic: resists water
    • Oleophobic: resists oil
    • Antistatic: resists airborne dust & dirt
  23. 5 eyeglass lens materials
    • Cr-39 plastic
    • High-Index Plastic
    • Glass
    • Trivex
    • Polycarbonate
  24. Corneal bullous edema
    Corneal edema with epithelial blisters
  25. 2 types of enzyme cleaners: name & purpose
    • Proteolytic: removes protein buildup
    • Triphasic: removes proteins, lipdis & mucoid buildup
  26. Giant Papillary Conjunctivitis: signs, symptoms & treatment
    • Papules on upper tarsal conjunctiva
    • Itching, FBS, redness, mucus
    • Discontinue lens wear for 2-4 wks, possibly with topical mast cell stabilizer drops
  27. Cause of CL-related corneal edema
    Lack of oxygen to the cornea
  28. Corneal vascularization: definition, cause, acceptable limit
    • Ingrowth of blood vessels to the cornea
    • Oxygen deprivation to cornea (or trauma from ill-fitting CL)
    • .5 - 1.5 in superficial peripheral cornea is acceptable
    • Neovascularization that reaches the stroma can lead to corneal scarring, intracorneal hemorrhage, and decreased vision
  29. Corneal infiltrates: 2 types, alternate name
    • Sterile or infectious
    • Sterile = CLPU = contact lens peripheral ulcers
  30. Symptoms & treatment of CL-related corneal infiltrates
    • Discomfort, mild conjunctival inflammation, minimal evidence of inflammation of anterior chamber
    • Discontinue CL wear and use topical abx
  31. Infectious corneal ulcer: signs & symptoms
    • Symptoms: Severe pain, redness, tearing, decreased va
    • Signs: Opacity of cornea with defect of stroma, inflammation of anterior chamber, and possibly hypopyon
  32. Risk factors for fungal & protozoan infections
    • Homemade CL saline solution
    • Hot tub / swimming pool use
    • Use of tap water to clean CLs
  33. Most common protozoan infection
  34. Current standard of care for K-ulcers (& why it was changed)
    • Frequent topical abx; d/c CLs; no patch
    • Corneal ulcers used to be patched, but evidence suggests that can lead to pseudomonas
  35. Pseudomonas : definition & treatment
    • Bacteria that most commonly affects CL wearers
    • Fortified abx: gram+ and gram -