Suppression 1 Flashcards
(22 cards)
What is the definition of suppression?
The cortical inhibition of visual sensation in one eye in favour of the other, when both eyes are open.
This may occur in binocular single vision (BSV) and in manifest strabismus. It may vary in area and density.
What is a defined suppression area known as?
A scotoma.
What is physiological suppression?
To eliminate physiological diplopia when using a monocular instrument and to suppress the peripheral field during intense concentration.
What is pathological suppression?
To eliminate symptoms when fusion cannot be achieved, such as binocular diplopia in manifest strabismus, confusion, and incompatible images.
What are the characteristics of suppression?
- Although a cortical function, it is often described in relation to the retina.
- Suppression of the fovea to eliminate confusion is usually the first to occur.
- An area around the point of diplopia occurs next.
In esotropia, what may the suppression area produce?
An elliptical scotoma.
How does suppression depend on the type of deviation present?
In intermittent strabismus, pathological suppression may occur when the manifest deviation is present.
At what age does suppression develop less rapidly?
After the age of 10 years.
What clinical tests may investigate suppression?
- Worth Lights
- Bagolini glasses
- Suppression plates on stereotests
- TNO / Wirt / Randot
- Polarised 4 dot test
- Prism reflex test
- 4 dioptre prism reflex test.
What is the purpose of the Post Operative Diplopia Test (PODT)?
Used pre-operatively to aid in strabismus management decisions and to investigate suppression area & risk of diplopia.
What does the density of suppression refer to?
Not all suppression is the same; it can be weak or dense, with dense suppression typically around the fovea and less dense in the periphery.
What is the purpose of the Sbisa bar?
To measure the density of suppression and scotoma dimensions.
Fill in the blank: Suppression develops rapidly in _______.
infancy.
True or False: An entire eye is rarely if ever totally suppressed.
True.
What may occur in patients with anisometropic amblyopia?
Some may experience suppression.
What does the term ‘intermittent strabismus’ refer to?
A condition where the strabismus is not constant and may alternate.
What is the significance of the 4 dioptre prism reflex test?
It is used to measure the presence and area of suppression.
What happens when prisms are held in front of the deviating eye?
The patient reports diplopia when they are no longer suppressing.
What is the recommended reading for understanding ocular motility disorders?
Ansons and Davis (2014) Diagnosis and management of ocular motility disorders.
What does the presence of suppression indicate when using the Synoptophore?
It measures the size of the suppression area in degrees.
What is the aim of using Botulinum Toxin (BT) in strabismus treatment?
To temporarily paralyse muscles to reduce the deviation.
What is the significance of the findings by Khan et al (2008) regarding postoperative diplopia?
Of 195 patients, only 14 (7%) developed diplopia, and only a small number found it troublesome.
