Revision session flash cards
• cgls
N-sm eso with ad rec
D - sI eso with gd rec
• sgls
N mod Right XOT
D sm R XOT
What type of strabismus is this?
Fully Accommodative Esotropia
Characteristics
•Onset 2-5 years - as increase in accom. tasks
• Starts intermittently becoming more constant
• May rub eyes/close one eye
• Aware of XOT more when tired/unwell
• Mod degree Hypermetropia (+2.00 - +7.00DS)
• BSV N & D when full + corrected (normally NBSV)
- Some control to microtropia
• AC/A ratio normal
• Amblyopia - length of time sgls & level of aniso
Near Esotropia
Aeitiology
• Thought to be due to high proximal convergence or high tonic convergence
Characteristics
• Ortho or small SOP on distance fixation
• Moderate/large SOT for near
• No amblyopia
• Often no significant refractive error
• Normal or low AC/A ratio
• Normal near point of accommodation
• No reduction in angle with plus lenses
• Normal sensory and motor fusion
Management:
• SURGERY
ARC
• Anomalous Retinal Correspondence (ARC) describes a condition in which originally non-corresponding retinal areas of the two eyes co-operate to produce a form of binocular single vision
Two types:
• HARMONIOUS (HARC) - if the angle of anomaly = angle of strabismus
• UNHARMONIOUS (UN-HARC) - if angle of anomaly is greater than zero but less than the angle of deviation
• Occurs in long-standing deviations
• Small angled deviation less than 20^
• Microtropia less than 10^
• Usually convergent
• Only mild amblyopia
• Rare in exotropia
• Provides useful BSV in manifest strabismus
• May revert to original angle after surgery
Near Exotropia (convergence insufficiency)
• Most commonly occurs in the mid-teens when reduced convergence &/or increased myopia break down the BV, can be in adults - Presbyopia with > near add
• Typically XOP at distance XOT at near
• Pxs present with symptoms (diplopia, asthenopia)
• Usually equal VAs, poor or no convergence (less than 10cm) NRC and normal sensory fusion with poor positive fusional amplitude
• Often myopic
Management
• If strabismus is constantly manifest for near and angle ›25^
• For smaller angles and only occasionally manifest:
- Correct any myopia (this may be enough to make deviation latent)
- Orthoptics - exercise base out prism vergences and Improve Conv Near Point if reduced
- Prisms - base In just sufficient to enable BSV for near (Usually tolerated for distance)
- gradually reduce the strength of the prism and combine with orthoptics
- Most importantly improve convergence near point
- If no improvement - refer for surgery.
Visual Stress:
• Visual stress is also known as the “Meares-Irlen” syndrome and the condition generally refers to reading difficulties, light sensitivity and headaches from exposure to disturbing visual patterns or print distortion.
• Moving words on a page a lumbling of words
• Poor Convergence
• Poor accommodation
• Diplopia
• Asthenopia
• Headaches mostly frontal
• Skipping words on the page
• Losing place frequently
• Struggling to copy from the boardReader moves/wriggles a lot!
Management:
• Dynamic ret to see if Lag/Lead in accom
• DEM to assess ocular movement in reading condition, tests saccades to measure speed + accuracy
• Coloured overlays for 3-6months may help
• Cerium lenses may alleviate stress
• CT findings:
N- mod L SOT
D sl eso with gd rec
What type of strabismus is this??
What is your differential diagnosis?
• Convergence excess esotropia
• Differential diagnosis:
- Near Esotropia
- Fully accom esotropia
- Constant esotropia c accom element
- V-Esotropia
How to prove if convergence excess?
• High AC/A ratio (6:1+)
• Bifocal - N sm esophoria with gd rec
• Strabismus at near only OR angle much greater at near
• Strabismus may only be present when looking at fine detail
• Onset 2-5 years, occasionally earlier
• Most have NBSV, rarely a microtropia
• Amblyopia rare (except in anisometropia)
• Most hyperopic but some are emmetropic or even myopic.
• It is important to differentiate convergence excess from non-accommodative NEAR SOT (has normal AC/A ratio) and undercorrected hyperopia ( e.g. do cycloplegic).
• Visual acuity - crowded logmar; no amblyopia, normal VA
• Ocular motility - nothing expecting inferior oblique overactions, convergence normal
• Prism cover test - to calculate ac/a
• Bagolini - suppression/diplopia at near, and in distance cross normal vision
• Prism fusion range- not at near due to manifest, will do in distance. Might do with bifocals to see if it helps the deviation
• CT findings:
N -mod exophoria with fair rec to occasional LDS with
diplopia
D - sl exophoria with gd rec
PCTN 25^ exo
D 10^ exo
What do you need to know now?
Near Exophoria
• increased diplopia at night at near when tired
• Prism fusion range - abnormal, may only be 5-10 (normal is 30), BO at near, normal BI range
• Bagolini - may be diplopic response
• Worths lights - may be 3 lights
• Ocular motility - V pattern, so measure on elevation and suppression.
• Convergence - may be reduced. Exophoria of 25D, breaking down. If bringing RAF towards may reduce convergence. Therefore treating convergence (6-7cm) may be able to control weakness
• Stereopsis - frisby good, 55sec but slightly reduced due to potential of breaking down
May give:
Base out prism to help or exercises
• CT:
N- sm exo with ad rec
D - mod R/alternating divergent squint
What additional tests do you need to do now to form a diagnosis?
Distance Exotropia
• Manifest for distance fixation only, usually intermittently but may be constant
• Most apparent during inattention, ill health and fatigue, and in bright light
• Little refractive error
• VA usually good and equal
• Usually no symptoms as the sensory adaptations are good, dip in distance
• Px may not have known about strabismus until told by others
• AC/A may be high in simulated type or they have increased fusional control
• True type is unaffected by AC/A or fusion.
Management of distance XOT:
• Diagnosis of True or Simulated 1st
• Correction of myopia or anisometropia
• Low degrees of hyperopia best left uncorrected- unless surgery is going to be planned or amblyopia potential
• Most require referral for surgery
• Orthoptist will use Newcastle Control Score to decide when Sx is required
• Where angle is <15^ and BSV maintained most of the time, optical &/or orthoptic treatment may be of benefit - but usually only in the short term to delay surgery
• Optical:negative lenses can be successful in the short term, where accommodation is good
• Prisms (full base in - then gradually reduce) - short term
• Tinted spectacles - useful in countries with high light intensity - again only short-term- high illumination has a dissociation effect
• True - Bilat Lateral Rectus Recession
• Simulated MR Resection with LR Recession in one eye
Infantile Esotropia + investigations + differentials
• Occurs before 6 months (usually 3-6 months)
• Usually large angle (>40 A)
• Same angle distance and near
• Crossed alternating fixation
• Less than half have ambyopia with EF
• Latent nystagmus develops later
• DVD - develops later around 18 months
Looks like a bilateral LR palsy (distinguish by “dolls head” movement)
• Cross Fixation
• Always require surgery!!
• Visual acuity - Cardiff cards and forced choice
• Motility - infantile will be same size in distance and near
• Family history - may be positive family history
Differential Diagnosis
• Duanes retraction syndrome
• VIth nerve palsy
• Accomodative esotropia
VAR 0.4 VAL 0.1
Microtropia
• Small angle <10^ with ARC
• Common
• Stable
• Anisometropia (usually 1.50DS or more)
• Always mildly amblyopic (one line at least)
• Central suppression
• Good but not perfect BSV
• Strong motor fusion
•Differs from classic ARC because associated with eccentric fixation
• Not possible to treat but may prevent successful orthoptic exercises
Investigations
• Stereo: reduced 70-80sec/ arc, not better than 55
• Prism reflect test: 4^ for micro, if central suppression scotoma
• Visuscope: looking for normal or abnormal fixation
• Ct: manifest deviation, may be flick
• Sbisa bar: density of suppression
• Refractive adaptation - 16-18weeks before intervening with occlusion therapy
• VA - never equal, may be reduced a line between eyes
Worths 4 lights:
• sensory fusion test i.e. retinal correspondence
• this test consists of four lights arranged in a diamond shape (two green lights horizontally, one red light and one white light)
• based on complementary colours
• subjective and partially dissociative
• tests the projection of retinal points used for fixation under binocular conditions
• 6m or 33cm
• Abnormal: 3 if suppression, 5 in dip
Advantages
• quick and fairly easily understood
• near and distance
Disadvantages
• very dissociative and unnatural viewing conditions
• can produce many false positive/negative results
• False Pos: The eyes are easily dissociated with the red-green spectacles and therefore a patient with unstable but functionally useful binocular vision may exhibit a suppression response.
• False Pos: retinal rivalry can occur which may cause false positive results
• False Neg: also a suppression area may fall within the centre of the test and miss all the apertures
Amblyopia Classification:
• Functional: Improvement after treatment expected
Strabismic
Anisometropic
Stimulus Deprivation
Meridional
Ametropic
• No Lesion: May be reversible
Organic:
Toxic
Amblyopia Management:
• Refractive: Cycloplegia
- 18 weeks to adapt, resolution of 1/3 anisometropia and strabismic amblyopia
- 90% resolve by 18 weeks, improvement up to 30 weeks
• Occlusion: Total (light+form), Total (form only), Partial (Bangeter foils).
- Moderate 0.300-0.600: 2-6hrs; increasing in 2hr steps
- Severe amblyopia: 0.700 or worse, full time (all waking but 1) or partial
• Atropine penalisation: prevents accommo/blurry vision.
- mild/mod amblyopia, conflicting for severe
• Optical penalisation: Distance (+3.50) added to normal eye, Near cycloplegia in normal eye + full rx with hypermetropic lens in amblyopia, Total penalisation: High hypermetropic lens added to healthy eye to induce blur both distance+near
