OTHER STUFF NEED TO KNOW Flashcards
whats the dioptres and differences between A and V patterns?
A Pattern:
* Relative convergence on up gaze and relative divergence on down gaze
* Minimum of 10-pd dioptres difference b/w upgaze and down gaze
V Pattern:
* Relative divergence on up gaze and relative convergence on down gaze
* Minimum of 15-pd dioptres difference b/w upgaze and down gaze
* This allows for a slight physiological V pattern
why is it important to record patterns (A/V)?
- Countless surgical overcorrections and undercorrections have been made due to failure to recognise patterns
- Decompensation of the binocular vision particularly on down gaze can affect near visual functions
- Diplopia + asthenopia + AHP
what are observations you can make before testing px?
- Gait (how walking? falling or bumping into things)
-obvious squint or manifest nystagmus
-pupils
-face asymmetry
-head turn or tilt
-proptosis or ptosis
-chemosis or oedema or bruising
muscle sequlae of NEURO
- Original palsy
- Overaction of the contralateral synergist
- Overaction of the ipsilateral antagonist
- Inhibitional palsy
(under, over, over, under)
(same diff, same, diff)
whats the diff features in longstanding vs newly acquired
Longstanding:
* AHP - fixed and pt usually unaware
* No diplopia
* Enlarged fusion ranges
* Old photographs
* Gradual onset of symptoms usually
* Amblyopia
* Suppression
Newly Acquired:
* Pt aware of AHP and uncomfortable
* Diplopia
* Sudden onset
* No enlarged fusion range
whats the diff features in mechanical vs neurogenic
Mechanical:
-smaller deviation in PP
-ductions = versions
-ceasing of movement abrupt
-pain
-reversal of diplopia
-up and downshoots
Neurogenic:
-large deviation in pp
-ductions better than versions
-gradual failure of movement
-no pain
-no upshoots and downshoots
What is H + S law?
- When one muscle is weak or limited muscle sequelae develops determined by Herring’s Law of equal innervation and Sherrington’s Law of reciprocal innervation
- Herring’s Law: When an impulse goes to a muscle, causing it to contract, a simultaneous and equal impulse goes to its contralateral synergist to contract by an equal amount
- Sherrington’s Law: When increased innervation is sent to a muscle to cause it to contract, decreased innervation goes to it’s direct antagonist, which is therefore relaxed.
What are the timings like for muscle sequelae to develop?
- Overaction of the Contralateral synergists according to Hering’s Law of equal innervation. – Immediately (a week)
- Overaction of the Ipsilateral antagonist according to Sherrington’s Law of reciprocal innervation – Time (few weeks)
- Secondary inhibition of the Contralateral Antagonist with Hering’s Law. This happens because the overaction of the antagonist in the affected eye requires less innervation – More Time
Pituitary adenomas
Pituitary adenomas are a collection of tumors that arise from the pituitary gland. These tumors are the most common cause of optic chiasm compression in adults.[1][2] Ophthalmologic findings typically involve visual field defects (e.g., optic neuropathy, junctional visual loss, bitemporal hemianopsia), although less commonly patients may also have efferent complaints (e.g., ocular motility deficits from cavernous sinus involvement, Nystagmus). Rarely compression of the third ventricle can produce Increased intracranial pressure.
what are the aetiologies of neurogenic palsies?
Trauma
Space-occupying lesion
Tumour
Vascular: aneurysm; carotid cavernous fistula;
subdural haematoma
Microvascular
Diabetes
Hypertension
Inflammatory
Tolosa–Hunt syndrome
Viral infections
Herpes zoster
Meningitis/encephalitis
Vasculitis
Giant-cell arteritis
Demyelination
Ophthalmoplegic migraine
Miller Fisher/Guillain–Barré
Acquired immunodeficiency syndrome
What is the cerebral peduncle?
The cerebral peduncle is a bundle of nerve fibers in the midbrain that contains major motor pathways (corticospinal and corticobulbar tracts) from the cerebral cortex to the spinal cord and brainstem.
Damage to the cerebral peduncle can disrupt these motor pathways, resulting in contralateral hemiparesis (weakness to opposite side of body).
what is Horner’s syndrome?
Horner’s syndrome results from a lesion of the sympathetic chain supplying the eye.
Horner’s syndrome is characterised by the triad of ptosis (drooping eyelid), anhidrosis (lack of sweating) and miosis (constricted pupil) on the ipsilateral side
The sympathetic nervous system innervates three important structures in the eye:
- Dilator pupillae: involved in mydriasis or dilation of the pupil
- Superior tarsal (or Muller’s) muscle: aids in elevating the upper eyelid with the levator palpebrae superiors
- Sweat glands
Characteristics of Mechanically Limited Ocular Movement
Positive Forced Duction Test (FDT): Essential feature of mechanical restriction.
Normal Saccadic Velocity: Until the point of mechanical restriction is reached, differentiating mechanical restriction from a neurogenic palsy.
Retraction of the Globe: Usually associated with narrowing of the palpebral aperture, seen when gaze is directed away from the site of the leash.
Equal Limitation of Duction and Version: Although commonly seen with mechanical disorders, effort may increase duction movement.
Reversal of the Deviation: Usually indicative of a mechanical factor, but can also occur in third nerve palsy, myasthenia, and multiple palsies.
Limited Development of Muscle Sequelae: Often confined to overaction of the contralateral synergist in the unaffected eye.
Abnormal Patterns of Movement: Particularly up-shoot and/or down-shoot from a tight lateral rectus muscle in some cases of Duane’s syndrome.
Torsional Movements of the Globe: Frequently seen, especially when horizontal gaze reaches the point of mechanical restriction.
Rise in Intraocular Pressure: When the eye attempts to move in the direction of the mechanical restriction.
General principles of management
of mechanically limited ocular movement surgery
Aims:
Centralize and Enlarge BSV: Reducing the need for an abnormal head posture (AHP).
Improve the Range of Movement: In the affected eye.
Restore a Normal Appearance: May be compromised by strabismus or other factors such as enophthalmos or eyelid anomalies.
Considerations: Surgical results can be less consistent and permanent compared to other forms of strabismus, but appropriate surgical intervention can offer great benefit.
Investigations for supranuclear stuff
- qualitative and, if possible, quantitative assessment of saccadic and pursuit movements;
- examination of the VOR and assessment of integrated head and eye movements;
- demonstration of Bell’s phenomenon;
- measurement of convergence and accommodation amplitude;
- an optokinetic drum to generate an optokinetic response to accentuate convergence–retraction nystagmus in the dorsal midbrain syndrome and pursuit deficits in patients with parietal lobe and brainstem lesions;
- qualitative and, if possible, quantitative assessment of nystagmus if present (see Chapter 24 for further details);
- pupil size and reflexes;
- eyelid position and movement;
- visual fields.
