Preoperative evaluation




Introduction


In this chapter many of the techniques of examination used in ophthalmic plastic surgery are described.


After taking an accurate history it is helpful to approach the examination in a methodical way. The relative importance of each test varies with the condition being assessed and this is discussed in later chapters.




Obvious pathology


Check the visual acuity.


Look for scars, inflammation, tumours, lid malpositions and any other obvious abnormality of the eyelids and face. Record accurately the size and site of any skin lesions and any attachment to deeper structures.




Eyelid position


With the patient’s eyes open look for ptosis or lid retraction, entropion, ectropion, telecanthus and rounding or medial displacement of the lateral canthus.


3.1


Margin–reflex distance




3.1a


While the patient looks at an examination torch held about half a metre away, measure the distance of each upper and lower lid margin from the corneal light reflex.




Fig. 3.1a


Corneal light reflex as the reference point for measuring the position of the lids (margin–reflex distance).



3.1b


The margin–reflex distance (MRD) allows an accurate assessment of the relative positions of each of the four eyelids. It provides more information than simple measurement of the vertical palpebral apertures (between the upper and lower lids) because an inaccurate record of the position of the upper lids occurs if the lower lids are not level with each other. The MRD reveals this.




Fig 3.1b


The value of the ‘margin–reflex distance’ – an obvious ptosis but almost equal vertical palpebral apertures due to a retracted right lower lid.



3.2


Telecanthus





The normal intercanthal distance is approximately half the interpupillary distance (see Table 1.1 ). In simple telecanthus the orbits are in a normal position. It should be distinguished from hypertelorism in which the orbits are more widely spaced than normal. The intercanthal distance may be altered following traumatic rupture of the medial canthal tendon, or in some congenital conditions, for example blepharophimosis (see Figs 9.7 pre B , 18.1 pre ).





Eyelid movement


Check that the lids open and close normally and move normally in upgaze and downgaze. Assess levator function ( 3.3 ), the power of the orbicularis oculi and frontalis muscles and Bell’s phenomenon ( 3.5 ). In isolated congenital ptosis and other myogenic causes of ptosis the upper lid hangs up in downgaze ( 3.3e,g ). In levator aponeurosis dehiscence, an acquired ptosis, the upper lid drops in downgaze ( 3.3h,j ). Look for jaw-winking ( 3.6 ).


3.3


Levator function




3.3a,b


Fix the brow with a thumb and measure the excursion of the upper lid between upgaze and downgaze.


Repeat the test two or three times on each side to check. Normal levator function is 12 to 15 mm.




Fig. 3.3a


With the brow fixed, measure the upper lid excursion between upgaze …



Fig. 3.3b


… and downgaze.



3.3c,d


Children may need something to watch and it may be helpful to hold the rule and the brow together leaving the other hand free.




Fig. 3.3c


In children, fix the brow and hold the rule with the same hand …



Fig. 3.3d


… to allow one free hand to hold an attractive target.



3.3e–g


In congenital ptosis the levator muscle is not normal. It does not relax fully, causing reduced excursion of the upper lid in relation to the eye and a hang up as the eye looks down.




Fig. 3.3e


Left congenital ptosis.



Fig. 3.3f


Reduced lid movement in upgaze.



Fig. 3.3g


Lid hang-up in down gaze.



3.3h–j


In levator aponeurosis dehiscence the muscle is normal and can relax normally. In downgaze the lid remains low.




Fig. 3.3h


Left acquired ptosis.



Fig. 3.3i


Reduced lid movement in upgaze.



Fig. 3.3j


Lid drop in down gaze.



3.4


Laxity of the lower lid retractors





This may be present with no clinical abnormality. The downward excursion of the lower lid in downgaze may be reduced and the tarsal plate, having lost its inferior attachment, may rotate inwards or outwards. If the lower lid retractors are very lax or detached the lower conjunctival fornix may be noticeably deeper than normal.



3.5


Bell’s phenomenon


Although an eye movement rather than a lid movement, Bell’s phenomenon is conveniently tested while assessing lid closure. Hold the upper lid open while the patient attempts gentle closure of the eye. Upward duction of the eye confirms the presence of Bell’s phenomenon ( Fig. 3.5a ). A patient who is unsure what you are going to do may suppress Bell’s phenomenon: gentle lid closure uses just the palpebral part of the orbicularis muscle and Bell’s phenomenon, if present, cannot be suppressed; forced closure uses also the orbital part of the orbicularis oculi and allows the patient to suppress the reflex and give the false impression of an absent Bell’s phenomenon ( Fig. 3.5b ).




Fig. 3.5a


Testing for Bell’s phenomenon.



Fig. 3.5b


Voluntary suppression of Bell’s phenomenon.


3.6


Jaw wink





Fig. 3.6a


Ptosis due to jaw-winking phenomenon.



Fig. 3.6b


Ptosis corrected by jaw movement to the opposite side.



Fig. 3.6c


Ptosis due to jaw-winking phenomenon.



Fig. 3.6d


Ptosis corrected by opening the mouth wide.


Ask the patient to move the jaw from side to side, or open the mouth, several times. The lid will lift with jaw movement if jaw-winking is present. In children, sucking a sweet or drinking may reveal jaw-winking. Occasionally, spontaneous brief upper lid jerks can be observed in jaw-winking.


3.7


Fatigue in myasthenia gravis





Fig. 3.7a


Right ocular myasthenia fatigue.



Fig. 3.7b


After 5 minutes ‘sleep test’ with eyes closed.

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Sep 8, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Preoperative evaluation

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