Strabismus Flashcards
1.Name the extraocular muscles of the eye.
2.Which muscles are intortors.
3.Which muscles are extortors.
1.7 muscles
4 recti
2 oblique
And levator palpebrae superiorus
2.Both Superior muscles SO,SR
3.Both inferior muscles IO,IR
Binocular single vision advantages
Ability to use both eyes simultaneously so each eye can contribute to a single perception
Advantages
3D perception of images
Both Blind spots are overlapped
An 8 years old child comes to opd with mother complaining of occasional crossed eyes esp left eye. You did cover uncover test and it showed esotropia of left eye.Pin hole test does not improved vision.You check visual acuity by Snellen chart and see two lines visual aquity difference in the eyes. He can see some words and not others(crowding phenomenon).
1.what is your diagnosis?
2.causes of this condition?
3.how would you treat this child?
- Amblyopia….Decrease in visual acuity due to abnormal binocular interaction.
2.causes
(Monocular) Strabismic amblyopia
Visual deprivation amblyopia (due to any opacity in eye)
Refractive error (Anisometropic,isometropic, astigmatic amblyopia).
3.Removal of cause of opacity…removal of cataract, corneal opacity.
Correct the refractive error
Using the poor vision eye and limiting the use of Normal eye by patching and penalization.
1.Pseudo squint 2 causes
2.What is heterophoria? Which test is done for its Dx?
3.What is heterotrophia?
- Prominent epicanthal folds and wide separation of the two eye give a false impression of esotropia and exotropia respectively.
- Tendency of misalignment of eyes but it is Kept latent by fusion mechanism(latent squint). Dx is based on cover uncover test.
Two types exophoria(common in myopia )and esophoria(common in hypermetropia) - It is manifest squint. Can be esotropia,exotropia, Hypertropia,hypotropia.
A 2 year old child comes to eye opd with squint eyes.The deviation remains same in all directions of gaze. On examination there is no ocular movement restriction and no diplopia.
1. Which type of squint is this?
2. What are the causes of this squint?
3. What examination tests would you perform?
4.Treatment?
- Non paralytic (concomitant) squint.
2.🌺 Refractive error
Hypermetropia causes esotropia.
Myopia causes exotropia.
Astigmatism causes exotropia.
🌺 Hyper and hypoactivity of convergent and diverging centres.
🌺Phoria may convert to Tropia.
🌺 Defective fusion mechanism.
🌺Sensory deprivation e.g corneal opacity, cataract, retinoblastoma.
3.Hirschberg test,cover test,krimsky corneal reflex test and fundus examination. - Correction of refractive error.
Amblyopia treatment
Bifocal glass
Recession or succession of involved muscle.
Concomitant squint types
ESOTROPIA
1.Congenital esotropia
2.Aquired esotropia….which further includes
…Accommodative refractive type
… Accomodative non refractive type
…mixed
EXOTROPIA
1.congenital exotropia
Intermittent
Constant
Secondary exotropia
Congenital infantile esotropia
Esotropia which occurs during the first 6 months of life.
Features
Angle of deviation is larger than 30 prism diopter
Cross fixation (using left eye for right gaze and vice versa). It gives false impression of bilateral 6th nerve palsy.
Latent nystagmus may be present.
Dissociate vertical deviation occurs.
TTT:Surgical correction
Most common type of squint in childhood is….
Types of this squint…
Accomodative squint
Can be of two types
1. Refractive Accomodative esotropia
2. Non refractory Accomodative esotropia
Refractive Accomodative esotropia…. Caused by Accomodative convergence associated with hypermetropia.Angle deviation is not same for distant and near vision.AC/A ratio is normal.
TTT…hypermetropia correction
Non refractive Accomodative esotropia…angle deviation is same for distant and near Vision. AC/A ratio is high.BSV is reduced for near and normal for distant vision.
TTT…bifocal glasses, amblyopia treatment and surgery.
Paralytic (Non concomitant) squint
1.Cause
2.Signs
3.Examination and tests
4.TTT
heterotropia in which the amount of deviation varies in different directions of gaze and there is ocular movement restriction.
1.Neurological lesion of CN 3,4 and 6 due to DM,HTN, trauma, congenital cause, infection etc.
2.systemic disease Hx
Limitation of eye movement in the direction of affected muscle.
Secondary deviation is greater than primary deviation.abnormal head posture. Diplopia present. False projection present.
Amblyopia absent.
- Hirschberg test,prism bar cover test, Hess chart to record limitations of extraocular muscles .
CBC,ESR,Blood sugar,VDRL,CT scan
4.prisms, occlusion, botulinum inj in strong muscle making it weak, surgery.
A 50 years old man presented with Diplopia and partial ptosis of right eye. On history he is found to be diabetic for the last 10 years.on examination,his upwards,downwards and adduction are limited . Pupils do not react to light.
1.What is your dx?
2.What will be your dx if ptosis was complete, diplopia absent and other signs were present?
1.partial 3rd nerve palsy
2.complete 3rd nerve palsy.
1.Surgical compressive lesions involving superficial parasympathetic fibers of 3rd nerve cause pupil…..3rd nerve palsy.
2.vascular or ischemic Medical lesion which involve central fibres of 3rd nerve cause pupil….3rd nerve palsy.
1.involving
2.sparing
- A patient on examination shows right hypertropia, limitation of right depression and head tilt to left side. He has normal right abduction , depression and elevation. What is dx?
- A patient on examination shows face turned to right and right esotropia in primary gaze,marked limitation of right abduction and diplopia on right abduction. What is your dx?
- 4th CN Palsy
- 6 CN palsy
DUANE RETRACTION SYNDROME
Simultaneous co contraction of medial and lateral rectus on attempted adduction cause retraction of the globe.
There is innervation of Lateral rectus and medial rectus by by 3rd nerve.
Classification
Type 1…limited abduction and esotropia in primary gaze.
Type 2…limited adduction and exotropia in primary gaze.
Type 3…both above
There is narrowing of palpebral fissure on adduction and widening of palpebral fissure on abduction.
TTT….do not usually need surgery.
If severe retraction occurs,large up shoot or down shoot occurs or cosmetic reasons present then surgery is indicated.
Surgery includes recession of strong muscle depending on type of Duane syndrome.
