32 - BV accommodation

Question 1

How to test ill-sustained accommodation issues?

Answer 1

Repeated testing of amplitude or facility. Don’t test on >35 since incipient presbyopia (presbyope without needing add yet).

Question 2

Describe Nott.
Purpose:
Equipment:
Lighting:
Method:

Answer 2

Purpose: Assess acucracy of accommodation at near
Equipment: Ret, ruler/tape measure, near target
Lighting: Bright
Method:
- View target binocularly with prescription (and they’re accommodating)
- Ret at 40cm and look for response.
- Move back and forth until getting neutral reflex.
(Ensure not swipe light over eye too many times or may bleach retina).

Question 3

MEM work how?
Purpose:
Equipment:
Lights:
Method:

Answer 3

Purpose: Accuracy of accommodation at near
Equipment: Ret, MEM card, trial lenses, ruler/tape measure
Lights: Bright
Method:
- Have patient fixate on card on your ret
- Scope eye briefly. If with movement, add plus lenses for them and vice versa.

Question 4

Binocular cross cyl how?
Purpose:
Target:
Method:

Answer 4

Purpose: Assess accommodation accuracy at near and estimate add in early presbyope.
Target: crossed lines, usually at 40cm
Method:
- Phoropter adds –ve cyl at axis 90.
- Ask which is clearer. Add plus BE until vertical lines clearer.

Question 5

Duochrome how?
Purpose:
Equipment:
Target:
Method:

Answer 5

Purpose assess accommodative accuracy (not use in red-green CVD)
Equipment: DIstance = 6m chart w/ red/green background. Near = Mallet box (NV-100) or similar.
Target: Black letter/shape on red/green background
Method: Which letters/shapes more clear? If green, add plus. If red, add minus.

Question 6

Relative accommodation test?
Purpose:
Equipment:
Light:
Target:
Method:

Describe the systems in the eye being used during the relative accommodation test.

Answer 6

Purpose: Assess ability to change accommodation w/o changning vergence
Equipment: Phoropter + near target on phoropter rod
Light: Bright
Target: Small letters close to VA at 40cm
Method:
- Confirm clear and single
- Add +ve until first sustained blur or diplopia.
- Dial back to distance Rx and confirm clear and single.
- Add –ve until first sustained blur or diplopia.
- Record blur/break for both times (no recovery).

• When adding +ve, accom decreases, causing divergence. BSV maintained via reflex convergence.
• Eventually reflex convergence can’t keep up in which case either blur (accom can’t decrease anymore) or break (convergence runs out before accom fully relaxes)
• When adding –ve, accom increases causing convergence. BSV maintained via reflex divergence.
• Eventually, reflex divergence runs out which then either blur (cannot accom anymore) or break (accom continues but divergence system breaks).

Question 7

How to obtain calculated AC/A ratios?
Difference between stimulus and response calculated?

Answer 7

Purpose: Asses vergence-accommodation rleationship with view distance changes.
Method:
- Measure deviation at 6m and at near.
Note: remember to account for how much actual convergence is required for a given distance.
- Note either different in STA or actual response (measure accom lead/lag at near)

Question 8

How to find gradient AC/A?
Purpose:
Method:

Answer 8

Purpose: Assess how applying lenses to change accommodation also changes vergence.
Procedure: Either,
- At 40cm, measure deviation, then again with +2.00DS
- At 6m, measure phoria then again with –2.00DS
- At 40cm, measure phorias ranging from –2.00DS to +2.00DS and work out graident.
3-5 is normal range.