Domain III: Instrumentation for Measurement and Observation Flashcards
Rigid contact lenses are verified before/after dispensing to the patient
before
Verify CPC/base curve, power, diameter, optic zone, center thickness, peripheral curves, tint
For rigid lens contacts
Base curve ansi
0.1mm
diameter
0.1mm
POZ
0.1mm
pc’s
0.1mm
thickness
0.1mm
power
0.12D
also know as the base curve, falls on the back of the lens/tear film of the eye
base curve=size of contact
central posterior curve
radius of curvature measures the …, not the linear measurment
curve
measures to 0.01 mm, drop of saline in the lens holder, lens floats concave side up
read clockwise
radiuscope
a) Determines size of both diameter and optical zone.
b) Used to examine surface of contact lens and edge of contact lens.
Shadowgraph
a) Used to determine diameter of lens and optical zone
b) Used to examine front surface of contact lens
c) Check Edge Contour
Hand held magnifier
Measured with handheld magnifier or shadowgraph
Optical zone
Curves flatten towards the periphery as the cornea flattens.
Specified to nearest 0.1 mm
peripheral curve
posterior optical zone is always … than the diameter
smaller
What checks blends
Profile analyzer
RGP tint
usually Blue, Gray or Green
on keratometer steeper curve = more
minification
In keratometer steeper curve =
Higher diopter
lower base curve
In keratometer flatter curve =
lower diopter
higher base curve
in keratometer record … first
horizontal reading
symmetrical astigmatism has … or … k readings
180 90
between 30 and 60 or 120 & 150
oblique astigmatism
Can observe the entire extent of a corneal scar or
infiltration
Diffuse illumination
The presence of folds in Descemet’s membrane
become visible
Diffuse illumination
The presence of any invading blood vessels in the
cornea is disclosed.
Diffuse illumination
set-up
(1) wide-open slit (flood light)
(2) low magnification
Diffuse illumination
Overall view of anterior segment. Lens position and movement of contact lenses. Surface quality of lens.
Diffuse illumination
1-2mm slit, medium to high magnification, Cross-sectional view of cornea, Corneal clarity, Lens deposits
Parallelpiped
Useful in observing scars, infiltrates, staining, and the corneal-lens relationship
parallelpiped
1-2mm slit, Medium to high mag., Fine lens deposits, Subtle corneal imperfections, corneal endothelium
Specular reflection
direct illuminations ( microscope trained directly into the slit)
Parallelpiped
Optic section
specular reflection
Lets one identify the tear layer, epithelium, bowman’s layer, stroma, endothelial zone
Optic section
helps to discover thickening, thinning, and distortions in the corneal contour.
Optic section
Determines the depth of foreign bodies or opacities in the cornea and capable of perceiving flare in the aqueous
Optic section
microscope trained adjacent to the slit
indirect, Retro illumination and sclerotic scatter
