5. Name : Mrs Saparamadu
Age: 45 years
Occupation : school teacher
P.M.H. : Nill F.H. : Nill P.O.H. : using spectacle since 4 years
co : she has changed her spectacle several times within short period of times as
she has eyestrain, indistinct near vision and diplopia while reading.
1st visit : R) plano-1.00×180
2nd visit : R) plano-1.00×180
ADD 1.25 DS
ADD 1.50 DS
16. Name : Master Raween
Age: 14 years
Occupation : school child
P.M.H. : ocular cutaneous albinism with abnormal head posture
F.H. : mother & farther first cousins marriage
P.O.H. : using spectacle since 4 years
co : double vision in right side
Subjective refraction : R) plano-3.50×180
18. What is yoke prism ?
Yoked prisms is a term used to describe a pair of prisms (one in front of the right eye
and the other in front of the left eye) either used therapeutically in glasses or as a tool
in neuro-optometric rehabilitation therapy, where the bases of the prisms are in the
same direction: left, right, up or down.
27. Name : Master Minidu
Age: 9 Years
Occupation : school child
P.M.H. : R/ Eye trauma by road traffic accident
F.H. : Nill
P.O.H. : R/ Eye surgery done
co : Double vision
Mild blurred vision
Subjective refraction : R) Plano-3.50×180 -> 6/60
L) Plano -> 6/6
28. Double vision is when
we look at 1 object but
can see 2 images. It
may affect 1 eye or both
❖ Patching ( occlusive ) therapy
❖ Identify and treat the underlying cause of the problem.
❖ Other options include eye exercises,
❖ wearing an eye patch on alternative eyes,
❖ prism correction (Fresnel prism)
❖ In more extreme situations, surgery or botulinum toxin
30. A Fresnel prism is a thin, transparent plastic sheet which induces a
prismatic effect (it alters the direction of the image entering the eye).
One side consists of a series of angular grooves (prisms) and the other
smooth side attaches to the lens of glasses.
31. ➢ There are two main types of prisms: Fresnel (press-on) and ground-in.
➢ Fresnel prisms are a thin film that can be stuck onto the inside of the
glasses lens in the office, while ground-in prisms must be made by an
TYPES OF FRESNEL PRISM
33. THE FRESNEL PRISM PRINCIPLE
A Fresnel prism, much thinner than a conventional ophthalmic prism
of the same power, can be imagined to be a series of small plastic
prisms lying adjacent to each other on a thin platform of plastic.
37. what you need in preparation for this task.
•Little screwdriver if you have a metal frame.
•A non-permanent marker
•A large bowl filled with water
•Already cleaned glasses
38. Wearing prism lenses
can eliminate the need
for a surgical solution
to double vision,
but they can only
correct some types of
39. ➢ Using prisms during vision therapy has
many benefits: Prisms create changes in
the eyes and brain, and enhance depth
➢ Prisms enable objects to appear in a
different location, “tricking” the eye into
an aligned position.
➢ Prisms enable clearer, more
comfortable binocular vision