Lecture 5: Binocular refraction

Question 1

What is binocular refraction?

Answer 1

where the subjective part of the examination is carried out WITHOUT an occluder being used.

A blurring lens is used in the LE

Question 2

What is binocular refraction a variation off?

Answer 2

Humphriss Immediate Contrast Technique (see next slide), which aims to inhibit the fovea of one eye to control accommodation.

Question 3

What type of px can you do binocular refraction on?

Answer 3

-Must be binocular (not appropriate technique for an amblyope. Even if you fog the better eye they will still use this eye)

Should have reasonably equal acuities (more likely to be binocular)

Definitely not someone with a very dominant eye-impossible to pick up before starting this technique. If you get odd responses abandon this.

Question 4

What should you blur other eye to?

How does binocular refraction relax accommodation?

Answer 4

need to blur the other eye to 6/9-6/12 for foveal suppression-wont use fovea of this eye but will have paracentral and peripheral areas for fusion

1. Fog LE to 6/12
2. Start subjective on RE
3. Accommodation is binocular process. they will accommodate in RE to overcome minus.
4. In LE they will accommodate which will cause distance vison to blur more. Px beomes aware LE is blurring more.
5. This causes them to keep the accommodation relaxed. More likely to say no to minus lenses.

Question 5

What is the routine of binocular refraction on a suitable patient?

Answer 5

1. after ret, carry out a quick monocular subjective check (need good vision)
2. fog left eye to 6/9-6/12. (usually requires +0.75 to +1.00 for foveal suppression)
3. carry out normal subjective routine on Right eye
4. add a +1.00 to RE to fog it and temporarily cover fogged LE
5. uncover LE and do subjective on LE
6. check sphere binocualry with fogging lenses removed. show plus

Question 6

What are the advanatages of binocular refraction?

Answer 6

-Provides an essentially normal visual environment
-Accommodation tends to relax as much as is possible during the subjective examination
-Cylinder axis is determined under binocular conditions (especially when determining a change)
-May save time
-No need to binocularly balance
-More stable accommodation
-Particularly helpful with “latent hyperopes” (people who are so used to accommodating that they don’t relax their eyes)

Question 7

What are the disadvanatages of binocular refraction?

Answer 7

-The technique cannot be applied successfully to every patient

-It follows that patient selection becomes most important with the ideal patient:
Having a good standard of binocular vision
Having reasonably equal right and left acuities