2. TRIAL CASE
It contains the set of spherical and cylindrical
lenses of known power.
Components present in Trial set are
o Spherical lenses.
o Cylindrical lenses.
o Prism.
o Accessories.
3. Reduce APERTURE LENSES
Always Plano convex & Plano concave.
Diameter of the lens is 20mm.
These lenses probably gives the best
approximation.
Use of the lens is neutralize the spectacle
lens with their opposite sign.
5. Spherical lenses
Present in plus and minus form
Range: +& -0.12D to +& - 20.00D.
Variation:-
0.25 to 4.00D in increment of 0.25D
4.00 to 6.00D in increment of 0.50D
6.00 to 14.00D in increment of 1.00 D
14.00 to 20.00D in increment of 2.00D
6. Cylindrical lenses
Present in plus & minus form.
Range:- +&-0.25D to +&-6.00D.
Variations:-
0.25 to 3.50D in increment of 0.25D
3.50 to 6.00D in increment of 0.50D
8. continue..continue..
Prisms up to 10 prism diopter with addition of
15to20prism diopter.
Range:-0.50,1,2,3,4,5,6,8,10,12 prism dioptre.
It is Plano thickness gradient prism.
9. Continue..
There are mounted with base apex notation.
Use:
To measure small squint.
To prescribe prism in spectacle.
12. TRIAL FRAMETRIAL FRAME
It is made up of metallic/plastic frame.
Ideal trial frame features are:-
1.Light weight with comfortable nose rest
2.At least 3 compartment one each for
spherical lenses
cylindrical lenses
occluder
13. Continue…Continue…
Compartment of cylindrical lens has smooth and
accurate rotation.
Properties of ideal frame:-
Non allergic material.
Nose bridge & temple are adjustable according
to patient face.
14. JACKSON’S CROSS-CYLINDERJACKSON’S CROSS-CYLINDER
The cross cylinder is a combination of two
cylinders.
Their axis at right angles to each other and
mounted in a handale.
The commonly used cross cylinders are of
+&-0.25 or +&-0.50.
It is used for Astigmatic refraction.
18. PIN HOLEPIN HOLE
Pinhole:-
It is black opaque disc with central pinhole
of 1 to 2 mm.
Ideal central pinhole diameter is 1.42mm.
PRINCIPLE:-
It allowed only one ray of light to passed
through along the principle axis of eye.
19. Continue …Continue …
USES:-
To see best corrected visual acuity.
Used for macular function test.
To analyzed opacity of cornea is central or
Para central.
21. STENOPIC SLITSTENOPIC SLIT
It is made of black opaque with slit aperture.
Slit aperture with 15mm length and 1mm width.
It allowed ray of light to passed through only 1
meridian.
24. MADDOX RODMADDOX ROD
It is the series of high power convex cylinder
mounted with their axis parallel to each other.
This available in red and green colours.
Principle:-
It convert spot light into a line.
27. GREEN & RED FILTERS.GREEN & RED FILTERS.
Green & Red filters:-
This are red glasses of 640nm & green 535nm
wavelength.
Red filter in front of the RE and Green filter for the
LE.
Principle:-
This dissociate the eye using colour sense.