What is Fusional Reserve?
Fusional reserves are a measure of how much vergence a person has in reserve that can be used to overcome a heterophoria. The patient is instructed to fixate on a near target (usually at 33 cm) binocularly and a horizontal prism bar is placed before one eye starting with the weakest prism strength.
How do you test Fusional reserves?
The fusional reserve that opposes the heterophoria is measured first (convergent, using base-out prisms, for exophoria), to blur point (if present), break point, and then the prism is reduced until the recovery of single vision.
What is positive Fusional Reserve?
The fusional reserves are the maximum amount the eyes can converge (positive fusional reserves, measured with base out prism) or diverge (negative fusional reserves, measured with base in prism) while still maintaining BSV. As the image doubles, the break point is reached.
How do you know if you have convergence insufficiency?
What are the symptoms of convergence insufficiency?
- Headache.
- Double vision.
- Eye fatigue.
- Blurred vision.
- Sleepiness when reading.
- Needing to re-read things.
- Trouble concentrating on what you are reading.
- Often losing your place when reading.
What does Exophoria mean?
Exophoria is a condition in which your eyes drift outward out of your control. It usually appears for a short time while you’re doing certain types of tasks. It’s not a serious condition and can be corrected with the right treatment.
What causes lack of convergence?
Convergence insufficiency can arise following infection, traumatic brain injury, certain medications, neurodegenerative diseases (e.g. Parkinson’s), myasthenia gravis, or Graves ophthalmopathy.
Can vertical Heterophoria come and go?
Your VH symptoms can come in waves throughout the day, leading you to feel 100 percent one moment and as if you’ve been locked in a centrifuge the next. Your headaches and dizziness can be brought on by: Quickly standing from a seated position. Moving your head from side to side.
Can you treat exophoria?
Once properly diagnosed, exophoria can be treated and corrected. It usually takes several months of regular treatment or exercises to correct exophoria. Most treatments are done at home, so it’s important that you do your exercises regularly as prescribed by your doctor.
Why do I have low fusional reserves at near?
Extending this further – a borderline posture (small-moderate esophoria) with weak muscles (low base-in fusional reserves) can also be an issue. Grab your horizontal prism bar and an interesting near target – I use “Mr Camel” or a small picture stick. What, you say you don’t have a horizontal prism bar? Gasp! Please order one immediately!
How are fusional reserves assessed in an exophoric posture?
An exophoric ‘posture’ requires at least twice as much ‘petrol in the tank’ as assessed on convergent (base-out) fusional reserves. 10 From the myopia control point of view, we are especially interested in divergent (base-in) fusional reserves, to balance any esophoria which carries a higher risk for myopia development and progression.
How is the fusional reserve of a system measured?
Fusional reserves can be measured by placing prisms in front of the eyes until single binocular vision can no longer be maintained. This is essentially a measurement of how much power the fusional system has over that which is already being used. There are several criteria that can be used to determine if the fusional vergence is under stress:
What do you need to know about fusional vergences?
A. The fusional vergences are optomotor reflexes designed to improve and maintain the alignment of the eyes so that similar retinal images project on corresponding retinal areas, a requirement for single binocular vision that utilizes normal retinal correspondence B. Vergences move the eyes in opposite directions