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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.

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