Manifest and latent strabismus PDF

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Binocular Vision And Refraction...

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Manifest and latent strabismus

Manifest Strabismus (Heterotropia) • •

An ocular misalignment whereby the visual axis of an eye deviates either constantly or intermittently Visual axis is not on the fixation object

Comitancy: size of deviation in the position of gaze e.g. is the deviation the same size in primary position compared to elevation. H.F/M. F: holding fixation/maintaining fixation N.H.F/N.M. F: Not holding fixation/ not maintaining fixation Not taking up fixation: when the eye is patched is does not fixate at all, due to very poor vision Alternating deviation: indicates that vision is equal in both eyes Intermittent: have binocular single vision Constant deviation: no binocular single vision Accommodative/ refractive error: is the deviation effected by accommodation or refractive error o Fully accommodative: when eyes are straight with glasses on o Partially accommodative: when eyes are not fully straight with glasses on If the eyes are straight up to the age of 5 they have developed simultaneous perception, fusion, stereopsis, then they suddenly get constant Esotropia they’ve lost their binocular single vision but if the eyes are aligned they may still experience BIV because they have developed it. If they have never developed it as a child you cannot experience BIV.

Size of deviation in prism dioptres • • •

• •

Small less than 16 PD Moderate 16-30 PD Large greater than 30 PD

When looking for a tropia, we are always looking at the uncovered eye to see any movement to take up fixation When there is no movement, it may mean that there is no manifest deviation

• • • • • •

The position of corneal reflection determines the size of the deviation In normal eyes the corneal reflection is symmetrical in both eyes slightly nasal in both pupils Esotropia= corneal refection displaced outward Exotropia= corneal refection displaced inward Hypotropia= corneal refection displaced down Hypertropia= corneal refection displaced up

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

-Right -Esotropia -Moderate (corneal reflection displaced temporally) -Intermittent -Fully Accommodative

-Right -Exotropia -Large -Intermittent

-Left -Hypotropia -Large

-Moderate right Esotropia -Moderate right Hypertropia

-moderate Left Exotropia -moderate left hypotropia

-deviation in secondary position -incomitant deviation -alternating fixation depending in what position of gaze

Manifest Strabismus: Detection • • • •

Observation Corneal Reflections (Hirschberg’s Test) Cover Test (Cover Component) Diplopia (sudden onset strabismus, usually in adults)

Assessment of Ocular Alignment (Cover/Uncover Test) • • • • •

What is the uncovered eye doing when the other eye is covered? o Takes up fixation What does the uncovered eye do when you remove the occluder? o Goes back to deviation What does the covered eye do when you remove the occluder? o Takes up fixation Generally, perform at Near 30cm, Distance 6m and sometimes >6m Record what you observe

Manifest Strabismus Recording/ abbreviations

Esotropia Exotropia Hypertropia Hypotropia () ’ hf

ET XT HT HypoT Intermittent sml = small Near Assessment mod = moderate holding fixation lge = large not holding fixation

nhf

Examples • • • •

sml AET = small alternating Esotropia sml RXT’ n.h.f. f = small right exotropia at near not holding fixation mod LE(T) h. f = moderate left intermittent Esotropia holding fixation lge RE(T)’ h.f = large right intermittent Esotropia at near holding fixation

Alternating = VA is equal in both eyes Not alternating = VA is not equal in both eyes

Manifest Strabismus Case Study •

Greg, aged 15 months old Family has noticed that his eyes do not appear straight occurred intermittently since he was a few weeks old since the measles 2/12 ago, the RE is turned constantly o Moderate RET

Latent strabismus (Heterophoria) • •

An ocular misalignment whereby the deviation is controlled by fusion and is only apparent when the eyes are dissociated Present in both eyes

Recovery: how fast the eye under the cover recovers its binocular single vision position Compensate: maintaining fusion Decompensate: cannot maintain fusion Slow recovery can decompensate into a manifest

Latent Strabismus Detection •

Cover Test (Uncover Component)

Latent Strabismus: Recording/ abbreviations

Esophoria

E

Exophoria Hyperphoria Hypophoria ’ rr mod rec

X H Hypo Near Assessment sml = small Rapid recovery mod = moderate moderate recovery lge = large slow recovery

slow rec

Examples • • •

sml E’ c rr = small esophoria at near with rapid recovery mod X c slow rec. = moderate exophoria with slow recovery slow recovery has more problems than moderate and rapid recovery

Orthotropia: when looking at the uncovered eye there is no movement to take up fixation (no manifest deviation) Orthophoria: eyes have not deviated under the cover (no latent deviation) Manifest Strabismus: Cover component Latent Strabismus: Uncover component Phoria: Latent Tropia: Manifest If there is an orthotropic you don’t have a manifest but a latent is present If there is an orthophoria you don’t have a latent therefore no manifest There is always a latent deviation if there is a manifest...