Binocular Subjective Refraction Flashcards
Binocular refraction techniques are performed with
- both eyes open and unoccluded
- both eyes viewing a common distance target
Advantages of a binocular refraction
- testing conditions are more realistic; closer to the habitual state
- accommodation, convergence and light adaption are held more constant
- greater control of accommodation
Which is better, monocular or binocular refraction?
-monocular subjective refraction is much more commonly performed in routine optometric practice, although expert opinion suggests that binocular refraction is superior
Difference in findings between monocular and binocular refraction
May be subtle or profound, depending upon the individual patient
Refractive conditions for which bino subjective refraction may be especially advantageous
- hyperopic anisometropia
- antimetropia
- intermittent latent hyperopia
- pseudomyopia
Unequal maximal acuity conditions for which bino refraction may be advantageous
- amblyopia
- disease condition
Ocular motility conditions for which bino refraction may be advantageous
- large heterophoria
- cyclo phoria
- latent nystagmus
What are techniques of achieving binocularity during refraction
- partial occlusion
- blur
- vectographic techniques
Partial occlusion as a bino refraction technique
The target is partially occluded such that only part of its visible to the right eye and only part is visible to the left eye
Disadvantage of partial occlusion in bino refration
May suffer from inadequate fusion lock
Blur as a bino refraction techniques
Use of plus lenses over eye not being examined
Disadvantage for using blur as bino refraction technique
May suffer from inadequate suppression control
Vectographic technique as a bino refraction
Polarized targets or filters are used such that only part of the target visible to the right eye and only part is visible to the left eye
Disadvantage of vectographic techniques as bino refraction
Suffers from decreased contrast of targets
Fusion locks
- when viewing an acuity chart under partial occlusion or vectographic conditions, portions of the chart can be seen by both eyes, while other parts are seen by only the left of right eye
- the potions seen by both eyes ensures the binocular fusion necessary for associate of the target
Necessary for good refraction
Expected findings in binocular refraction
- similar to those obtained using a monocular subjective
- additional plus acceptance and/or a small change in the cyl axis
What kind of bino refraction uses a septum as a fusion lock
Turville
What is the most common blur technique to use during bino refraction
Humphriss immediate contrast test
What kind of binocular blur refraction do you add +0.75 to fog the other eye, and reach an endpoint that is a reversal from -0.25D being preferred to a +0.25D being preferred
Humphriss immediate contrast
What kind of bino refraction uses polarized light
Vectographic technique
Why is it good to have convergence of both eyes during a bino refraction
It will help stabilize accommodative system
Why do fusion lock?
Ensures binocularity
What do we use to check for suppression
Vectographic acuity chart
What do we use to find associated phoria with no fusion lock
Vectographic acuity chart
