NCLE Study Guide Questions And
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Corneal - ANSWER✔✔ Most common design for rigid and gas permeable lenses.
The three broad categories of contact lens design - ANSWER✔✔ Scleral (haptic),
semi scleral, and corneal lenses
The more common conditions for choosing either smaller or larger contact lens
designs - ANSWER✔✔ Smaller lenses are good for milder forms of keratoconus or
irregular astigmatism.
Larger lenses are good for advanced keratoconus, pathologically dry eyes, or
severe ocular surface diseases.
All seven names for classes of contact lenses - ANSWER✔✔ Bandage lens,
cosmetic/theatrical lens, flexible/prolonged wear lens, gas permeable,
hydrophilic, hydrophobic, and semi-soft lenses
Wetting angle - ANSWER✔✔ The angle that the edge of a bead of water makes
with the surface of a material, the smaller the angle the greater the wetting
ability.
PMMA: Polymethlmethacrylate
CAB: Cellulose Acetate Butyrate - ANSWER✔✔ The two types of rigid lenses.
,Bausch and Lomb soft lens - ANSWER✔✔ HEMA: hydroxyethlmethacrylate.
9 characteristics of contact lenses to take into account to best advise patients -
ANSWER✔✔ Percentage of water content, oxygen permeability, how well the
material defends against deposits, thickness, lens edge, lens color/tint if
applicable, design parameters, length of wear desired, and replacement intervals.
Benefits of soft contact lenses - ANSWER✔✔ Comfortable, shorter adjustment
period, good for patients in athletics or patients with minor corrections, and
better in environments where particles would get lodged under a rigid lens.
Allergic responses to silicone hydrogel lenses - ANSWER✔✔ Most common
complaints that point towards an allergic reaction is redness, discomfort, itchy
eyes, and greater lens awareness.
Common contraindications for soft lenses - ANSWER✔✔ Visual acuity, absorbing
things like chemicals, germs, oils, but also being able to be dehydrated easier by
being in dry environments. Tainted lenses can also cause ocular diseases, and any
irregularities or bumps on sclera/bulbar conjunctiva would cause issues with soft
contacts.
1947 - ANSWER✔✔ The year the first all plastic corneal lens was made by K.
Touhy.
Significance of the year 1968 relating to CLs regulation - ANSWER✔✔ The year the
FDA became involved in regulating contact lenses.
,The three layers of the precorneal tear film that make up the acronym LAM -
ANSWER✔✔ From outside to in; lipid, aqueous, and mucin.
Bandage Contact Lens - ANSWER✔✔ Protects the eye while the healing of corneal
disorders takes place.
Bicurve and tricurve lens design - ANSWER✔✔ Bicurve: A pair of blended curves, a
primary base curve and flatter peripheral curve.
Tricurve: Two peripheral curves labeled intermediate curves, both being 1mm
flatter than base curve.
The anterior zone on the edge of a contact lens - ANSWER✔✔ Portion of the edge
in contact with the upper lid during a blink cycle.
The posterior zone on the edge of a contact lens - ANSWER✔✔ Small reverse
curve placed on the posterior lens surface to flare the edge away from the
cornea.
The edge apex of a contact lens - ANSWER✔✔ Junction between the anterior and
posterior zones on the edge of a contact lens.
Three things that can be attempted to increase tear exchange in a GP lens -
ANSWER✔✔ Reduce overall lens diameter, flatten the peripheral curves, or,
decreasing the optic zone.
, Base curve of a contact lens - ANSWER✔✔ Central portion of the back surface of a
contact lens, also known as CPC or central posterior curve.
Rule of thumb for the effect of radius of curvature changes on CL power -
ANSWER✔✔ Power of a curve changes by 0.50 diopters, radius of curvature
changes by approximately 0.10mm
45 diopters of power is equivalent to this radius - ANSWER✔✔ 7.50 mm of radius.
7.50 mm of radius is equivalent to this power - ANSWER✔✔ 45 diopters.
Sagittal depth or height - ANSWER✔✔ Distance between a flat surface and the
back surface of the central portion of the lens.
Correlation of radius of curvature to sagittal depth - ANSWER✔✔ ROC increases,
sagittal depth decreases and vice versa.
Correlation of radius of curvature to base curve in regard to steepness/flatness -
ANSWER✔✔ ROC increases, base curve becomes flatter. ROC decreases, base
curve becomes steeper.
Multicurve Lens - ANSWER✔✔ Contains a base curve and three or more
peripheral curves. Usually a larger lens.
Truncated lens - ANSWER✔✔ A lens that is cut off to form a horizontal base to
add stability to a soft toric lens and to prevent rotation.