NV Syndromes, Prescribing Prism Flashcards
What is convergence insuffiency at Distance and Near?
Distance: Ortho
Near: Exophoria
What is divergence insuffiency at Distance and Near?
Distance: Esophoria
Near: Ortho
What is convergence excess at Distance and Near?
Distance: Ortho
Near: Esophoric
What is divergence excess at Distance and Near?
Distance: Exophoric
Near: Ortho
Overall, what is convergence insuffiency or excess lead to at distance?
ORTHO
Overall, what is divergence insuffiency or excess lead to at near?
ORTHO
If the patient is 4XP at distance and 12XP at near can they still be considered convergence insuffient?
Yes
What are the biological causes for divergence insuffiency?
Anotomical:
Low muscle tone
Abnormal orbital shape
Abnormal orbital position
Abnormal Check ligaments
Abnormal muscle insertions
What is the way to fix divergence insuffiency? What would this lead to?
- Correct Rx
- Train divergence
- VT for vergence
- Rarely prism
ESOPHORIA
What causes convergence insuffiency?
What do these pt show clinically?
Under accommodation from:
- Uncorrected myopia
- Absolute Hyperopia
- Suppression
- Monocular Viewing
- Presbyopia
- Large PD
Reduced PRV and receded NPC
Should convergence insuffiency take off glasses to read?
No because large PD and exo at near
How do you manage convergence insuffiency?
- Correct Rx
- Train accommodation with flippers
- Train vergence with flippers, vectograms or brock string
- Rarely prism
What are the cause of convergence excess?
Excess accommodation due to uncorrected hyperopia (latent hyperopia), accommodative spasm, pseudomyopa or early presbyopia.
What do convergence excess pt display?
Reduced BI, and large lag of accommodation
How do you manage convergence excess?
- Correct Rx
- Use bifocals with high AC/A NOT low AC/A
- Train divergence at near
- Increase Working distance or decrease duration of near work
- Rarely prism
What are the causes of divergence excess?
Basic Exo (Exo at distance and near) with high AC/A
Anotomical factors
With age becomes more Exo
How do you manage divergence excess?
Difficult to do but can train accurate vergence at distance
Rx 2 glasses one with prism for distance and one without for near
When would a pt with divergence excess become symptomatic?
As they get older because they had a larger amplitude of accommodation when they were younger thus they could compensate
Based on EBM VT is only good for which problem?
Convergence insuffiency
(Ortho at distance and exo at near)
How does brock string work?
Point of fixation is single while everything else is seen in diplopia
What happens if the pt is an over converger and perform brock string?
They will converge the two strings together in the front and see bead as double
What happens if the pt is an under converger and perform brock string?
They will converge strings behind the bead and the bead will appear double
What evaluation does brock string give us?
Fixation Disparity
What is the overall goal of brock string?
To make the “two strings” cross at the fixation bead
Prescribing too much horizontal prism is good for which type of pt?
Vertical deviations
What are morgan’s norms?
How is it used to Rx?
Distance: 0-2XP
Near: 0-6XP
Was never meant to Rx but you would add prism until the pt is in normal range
What is percival criterion best for?
What does it not consider?
Best for ESO
Does not consider size of phoria
What is Rx’ing with fixation disparity good for?
Rx with associated phoria this shows the uncompensated phoria and is good for horizontal deviations
What do prisms do to the FD curve?
Shift left and right
What does plus and minus lenses do to the FD curve?
Shift it up or down
What does VT do to the FD curve?
VT flattens the curve
When should plus lenses be used over prisms?
High AC/A
Eso because they are hyperopic
Lead of accommodation
Low Amp of accommodation
In which situation is ground prism better? PD= 65
Ie: 2prisms
When the Rx is lower ie: +1.00
Because if the pt needed 2prisms and you ordered prism by decentration then it would be
p=cF
2=c(1)
c=20mm/ eye which would be a DBC of 65-40= 25= Crazy
What is prism titration?
When you introduce prism till the pt reports the previous higher prism was better
What does VT improve?
The SFV system by improving prism adaption
What is asthenopia?
Eye fatigue from demand on FFV system
