BVP - Assessment of Binocular Vision Disorders and Accommodation-Vergence Problems - Week 5 Flashcards
What is posture of accommodation?
How accurately the accommodative system focuses relative to where the visual stimulus is located
List two tests that assess posture of accommodation.
MEM retinoscopy
Binocular cross cyl
Is MEM retinoscopy subjective or objective?
Objective
What is the normal value for MEM retinoscopy? What is an abnormal finding (2)?
+0.25 to +0.50
Any minus finding or >+0.75 is abnormal
Is binocular cross cyl subjective or objective?
Subjective
List two disadvantages of binocular cross cyl.
Requires a phoropter
Proximal cues are lost and not a true representative of accommodation
What is the normal value for binocular cross cyl?
+0.50 ±0.50
What is amplitude of accommodation?
How much accommodation capacity the system has
List three tests for the amplitude of accommodation.
NPA
Refractor Head Near Point Rule
Minus lens to blur
What is the most widely used technique for amplitude of accommodation?
NPA
What is the minimum and normal values for NPA?
Minimum - 15 - age/4
Normal - 18 - age/3
Describe the reverse push up method. Does it over- or underestimate accommodation? Explain why.
Use a printed target, have the patient cover one eye, and bring the target close so that its blurry.
Slowly move the card outward until clearly seen and measure. Do this several times.
Will overestimate accommodation due to the magnification effect of bringing it close, improving acuity.
What is a disadvantage of RAF?
Requires the phoropter and proximal cues are lost.
Describe minus lens to blur. What are the expected values compared to the pushup method? Explain why.
Target is placed at 33cm, and minus lenses are added until the target blurs.
Expected values are generally less than with the pushup method by 2D
This is due to no magnification effect and some minification
What is accommodative facility?
How quickly and efficiently accommodation changes.
Can accommodative facility (using flippers) be done monocularly as well as binocularly?
Yesd
What should be noted when doing accommodative facility (also for vergence facility)?
Note if one side is noticeably slower/more difficult
What is the normal value for accommodative facility?
±2.00D flippers should be 8cpm
What is vergence posture (also heterophoria)?
How accurately the eyes are pointing to where the visual stimulus is located
List 5 tests to assess vergence posture.
Prentice card
Maddox rod
Von Graefe
Cover test
Maddox wing
What is the preferred method for measuring phoria in children of school age?
Prentice card
Explain how a maddox rod setup works.
It is made up of a series of grooves on a red filter. When light shines through, it will appear as a single red streak. The eyes will adopt a fusion free position
Which is a more repeatable means of measuring phoria; Von Graefe or Maddox Rod?
Maddox Rod
Is Von Graefe the preferred test for assessing phorias in children?
No
What is an advantage the Maddox Wing has above all other methods? What is its disadvantage that has seen it become less commonly used?
Its advantage is that it can detect cyclodeviations
Its disadvantage is that it fails to adequately control accommodation when determining the phoria
Is the cover test objective or subjective? What three components of a phoria can it assess?
Objective
Assesses presence, direction, and magnitude of a phoria
What can be done to ensure accommodation is controlled during a cover test?
Ensure the target has detail and is engaging. It must be age appropriate.
What is the Hirschberg test?
It evaluates the position of the corneal reflex relative to the pupil to determine the presence of any horizontal or vertical tropia.
What is the Krimsky test?
It is the Hirschberg test, but with the addition of prisms to neutralise the tropia and determine its magnitude.
Prism is added until the corneal reflex overlaps with the centre of the pupil. The prism required is the magnitude.
What is the amplitude of vergence?
How much capacity the vergence system has, and how much it can converge and diverge on demand
What are two tests to assess the amplitude of vergence?
PRC (convergence)
NRC (divergence)
What is vergence facility?
How quickly and efficiently the vergence system can change to uptake convergence or divergence on demand
What prism flippers are generally used to measure vergence facility?
12^BO and 3^BI
What is a normal break-recovery for NPC?
5-7
What is the recommended break in children? What is an abnormal value?
<5cm
>5cm indicates BV issues
In adults, what is deemed an abnormal break-recovery for NPC?
Anything over 10cm is abnormal
Suspicious if over 5cm
What are the normal values for NRA and PRA?
NRA - +2.50D
PRA - -2.50D
What does AC/A assess?
The effect of accommodation on vergence.
What is the normal value for AC/A?
4^/1D ±2 SD
What is the minimum battery of tests to yield good sensitivity and specificity for diagnosing non-strabismic binocular vision anomalies (NSBVAs)? What values for these tests would be anbormal?
NPC - >7.5cm
Monocular accommodative facility - <10cpm
D-N phoria (difference) >1.25^
What is the minimum battery of tests to do on a routine basis (8)?
Cover test
Stereopsis
NPC
NPA
Phoria D-N
Accommodation facility
Vergence facility
MEM retinoscopy
