basic tests in orthoptics settings

1. Hirschberg and krimsky test. Cover test, prism
cover test and types. Test for convergence,
accommodative problems, suppression,
stereopsis, prismfusion range, methods and
interpretation
JYOTI SHAH
OPTOMETRIST

2. Hirschberg test
Gives rough estimation of angle of manifest squint
Patient is asked to fixate at a point light held at a distance of 33cm
Amount of deviation=note the angle of corneal light reflex
Each 1 mm decentration of corneal reflex correspond to 7 degree( 1 degree=2 prism
diopter)

4. Krimsky test
To perform this test patient is asked to fixate on a point light at 33cm
Prism is placed in front of deviating eye and strength is increased until corneal
light reflex is centered in squinting eye
Apex towards deviation until the corneal reflex is centered
Base In prism for exotropia and Base out prism for esotropia

5. Modified krimsky test
Prism is placed in normal eye and strength is increased until the squinting eye gets
centered

6. Cover test
It is the main method of detecting manifest and latent squint
The cover tests should be performed with and without glasses at distance 6m and at
near 33cm.
PREREQUISITES OF COVER TEST
patient should be co-operative enough to fixate a target.
Should have sufficient vision to see target
Should have central fixation in both eyes .
Latent nystagmus should not be present.

7. Methods(types) of cover test
1.Direct cover test
Aim : It confirms the presence of a manifest squint
Procedure
Fixate with both eye at a point
Normal looking eye is covered and movement of uncovered eye is noticed.
 if uncovered eye takes the fixation in opposite direction ,manifest squint is present
eg: exotropia is present, the eye taking up fixation will move towards nose
Esotropia is present, it will move towards the temple

9. 2.Cover uncover test
Aim: It establishes the presence and type of heterophoria/latent
squint
Procedure:
Performed after direct test conforms absent of manifest deviation
 one eye covered with occluder and other is made to fixate.
In presence of heterophoria the eye under cover deviates(fusion
is interrupted)
Cover is moved quickly and direction of movement tells the type
of heterophoria

10. Direction of the movement of the eyeball tells the type of heterophoria( eg. The eyeball
will move towards the nose in the presence of exophoria and towards the temple in
presence of esophoria)

11. 3.Alternate cover test
It is performed to establish whether the squint is unilateral or
alternate
Procedure :
Patient is asked to fixate alternately ,placing occluder
alternately.
It is important to place occluder alternately several times to
dissociate the eye and maximize the deviation.
Occluder should be transferred quickly from one eye to
other to prevent fusion.

12. Observations:
In presence of alternate squint either eye fixates and opposite
eye under cover deviates and maintains the position of deviation
on removing the cover.
In presence of unilateral squint , after removal of cover always
normal eye takes up the fixation and opposite deviates.

13. 4.Prism bar cover test
Prism is placed in front of squinting eye and alternately cover test is performed until
movement stops

14. Test for convergence
Near point of convergence:
 it is the point closest to the eye at which convergence can be maintained
It is measured with RAF ruler(near point ruler) subjectively and objectively
In normal adults, its average value is 7cm with a range between 5cm and 10cm
Greater than 10cm is considered as convergence insufficiency and closer than 5cm
is convergence excessive

15. Test for accommodation
1.Near point of accommodation(NPA):
it is the closest point at which small object can be seen clearly
Also called “near point “ or “punctum proximum”
Measured with RAF ruler

16. 2.Amplitude of accommodation
The difference between the dioptric power needed to focus at near point and
far point is called amplitude of accommodation
A=P-R
Measurement of amplitude of accommodation
1.Push up test:
 Done by RAF ruler
Direct patient attention to N8 target of letters on near point card
Near point card is brought close till the patient sees blur. Record the dioptric point on near point rod
2.Using minus lenses
each eye tested separately
Patient asked to fixate 660 target at 6m and minus lenses added till patient reports first blur

17. 3.Assessment of accommodative response
Monocular estimated method(MEM ): it is a form of dynamic retinoscopy widely used
to objectively measure accommodative response
The normal values are between +0.50D and +0.75D
Lag of accommodation: accommodative response is less than accommodative
demand. All the values higher than +0.75D
Lead of accommodation: accommodative response is more than accommodative
demand. All the values below +0.25 D

18. 4.Accommodative facility
An accommodative flipper of +2.ooD with -2.00D is used to test accommodative
facility
Difficulty with plus lenses is seen in patient with accommodative excess
Difficulty with minus lenses is seen in patient with presbyopes

19. Test for stereopsis
1.Titmus stereoacuity test(polaroid vectograph)
2.TNO test
2.Random dot stereogram test
Depth perception is the visual ability to perceive the world in three dimensions (3D)
and the distance of an object
Normal value 4o sec of arc
Reduced in amblyopia, suppression

20. Test for suppression

21. Bagolini striated glasses test
The BSGT is used for patients with strabismus to test for suppression, normal retinal
correspondence or abnormal retinal correspondence particularly in cases of manifest
strabismus

22. PFR(prism fusional range)
Test can be performed using prism bar
Amplitude of divergence(BO) and amplitude of convergence(BI) are measured
Note
Divergence should be performed before convergence
Unless measuring relative fusional vergence do not concerned if the patient
indicates the image is becoming blurred. Concentrate on single vs double.

23. PFR Normal values
BO(convergence) DISTANCE
20-25 PD
NEAR
30-35PD
BI(divergence) 6-8PD 8-10PD

24. Homework
1.what is prism? what are used of prism in ophthalmology?
2.Name of different cover test?
3.Prism,types and uses in ophthalmology?
4. Write about krimsky test?