Opticianry and Contact Lenses

• Maintain corneal temperature
• Metabolize waste
• Oxygenate the cornea
• Sustain integrity of corneal epithelium

Difference between top & bottom of eyeglass frame in relation to patient's face

Neovasularization of retina due to high oxygen levels in neonatal incubator

• To determine magnification necessary to read newsprint / J5
• Reverse Snellan score (ie 20/200 --> 200/20 = +10 D)

• 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)

Distance from bottom of eyeglass rim & top of multifocal lens segment

• Distance (in meters, in decimal form) x lens power
• Lens power ÷ distance (in meters, expressed as fraction)

• With projection: Can tell which quadrant light is coming from (test all 4 and record in chart)
• Without projection: Cannot determine angle of light

≤20/200 or ≤20° VF

African river blindness

low vision due to Vit A deficiency

• Bifocal: top of segment level with lower lid margin
• Trifocal: Approx. 7 mm above lid margin

Normal eye alignment; straight in the primary gaze

Visual distortion caused when distance between optical centers doesn't match patient's PD

Optical distortion when the patient's line of sight is not parallel to that of person taking measurements

• Binocular: from center of right pupil to center of left pupil
• Monocular: from center of each pupil to center of bridge of nose

Distance from front of cornea to back of eyeglass lens (13.5 average, ideally as close as possible without touching lashes)

• Distometer
• Vertometer

Curve on outer surface of blank lens

Geneva lens clock

Point on lens through which light rays are perfectly parallel

• 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

• Cr-39 plastic
• High-Index Plastic
• Glass
• Trivex
• Polycarbonate

Corneal edema with epithelial blisters

• Proteolytic: removes protein buildup
• Triphasic: removes proteins, lipdis & mucoid buildup

• Papules on upper tarsal conjunctiva
• Itching, FBS, redness, mucus
• Discontinue lens wear for 2-4 wks, possibly with topical mast cell stabilizer drops

Lack of oxygen to the cornea

• 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

• Sterile or infectious
• Sterile = CLPU = contact lens peripheral ulcers

• Discomfort, mild conjunctival inflammation, minimal evidence of inflammation of anterior chamber
• Discontinue CL wear and use topical abx

• Symptoms: Severe pain, redness, tearing, decreased va
• Signs: Opacity of cornea with defect of stroma, inflammation of anterior chamber, and possibly hypopyon

• Homemade CL saline solution
• Hot tub / swimming pool use
• Use of tap water to clean CLs

Acanthamoeba

• Frequent topical abx; d/c CLs; no patch
• Corneal ulcers used to be patched, but evidence suggests that can lead to pseudomonas

• Bacteria that most commonly affects CL wearers
• Fortified abx: gram+ and gram -