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Ophthalmic surgery is one of the most frequent surgical procedures
requiring anesthesia in developed countries.1
Perioperative morbidity and mortality rates associated with eye (eg,
cataract) surgery are low.2,3 Nevertheless, because
patients with cataracts tend to be older and to have serious
comorbidities,4–9 systematic preoperative evaluation
should be performed to consider a patient eligible for
surgery.9 Anesthetic management may contribute to the
success or failure of ophthalmic surgery. A closed-claims analysis by Gild
and coworkers10 found that 30% of eye injury claims
associated with anesthesia were characterized by the patient moving during
ophthalmic surgery. Clinical strategies to ensure patient immobility are
essential, as blindness is the outcome in many cases of eye injury. Most
problems occurred during general anesthesia. Quicker patient rehabilitation
and fewer complications are the main reasons why many ophthalmic surgeons
are choosing local (LA) over general anesthesia.11–13
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In the past, regional anesthesia on the eye typically consisted of
retrobulbar anesthesia (RBA), with the surgeon performing the block.
Widespread use of the phacoemulsification technique, however, has changed
the anesthesia requirements for this technique—total akinesia and lowered
intraocular pressure are no longer necessary. Consequently, conventional RBA
is used less frequently today, particularly since it carries a greater risk
for complications than do the emerging techniques. The newer techniques do
not provide akinesia of the globe paralleling that of the retrobulbar block;
however, they are useful for anterior segment surgery, especially cataract
surgery. Accurate knowledge of anatomy and of various anesthetic techniques
are necessary to determine the appropriate block for specific clinical
situations. This chapter will review the relevant anatomy of the eye,
classic (retro and peribulbar) needle block techniques, emerging anesthesia
techniques, and choice of LAs and adjuvant agents.
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The cavity of the orbit has a truncated pyramid shape, with a posterior
apex, and a base corresponding to the anterior aperture. The orbit contains
mainly adipose tissue, and the globe is suspended in the anterior part. The
four rectus muscles of the eye insert anteriorly near the equator of the
globe (Figure 21–1). Posteriorly, they insert together at the apex
on the tendineus anulus communis of Zinn, through which the optic nerve
enters the orbit. The four rectus muscles delineate the retrobulbar cone,
which is not sealed by any intermuscular membrane.14–17
Sensory innervation is supplied by the ophthalmic nerve (first branch of the
trigeminal nerve [V]), which passes through the muscular cone
(Figure 21–2). The trochlear nerve (IV) provides motor control to
the superior oblique muscles, the abducens nerve (VI) to the lateral rectus
muscle, and the oculomotor nerve (III) to all other extraocular muscles. All
but the trochlear nerve pass through the muscular conus. Injection of LA
solution inside the cone will provide anesthesia and akinesia of the globe
and the extraocular muscles. Only the motor nerve to the orbicularis muscle
of the eyelids has an extraorbital course, coming from the superior branch
of the facial nerve ...