Chapter 36. Local and Regional Anesthesia for Ophthalmic Surgery
In 2012, the most popular form of anesthesia employed by US cataract surgeons was:
C. Topical anesthesia alone
D. Topical anesthesia with supplemental intracameral lidocaine
D is correct. This answer is based on the 2012 survey of the American Society of Cataract and Refractive Surgeons. Sub-Tenon’s blocks are more popular in the UK and Australia.
A, B, C, and E are incorrect. Based on the same US survey, these options were less popular.
Regarding the anatomy of the orbit, which of the following is true?
A. There is no free communication between intraconal and extraconal spaces.
B. The lateral walls of the orbits are roughly perpendicular to each other.
C. The average axial (anteroposterior) length of the adult male globe is almost invariably 24 mm.
D. All the nerves supplying the extraocular muscles of the eye pass through the muscular cone (or annulus of Zinn).
E. The Tenon’s capsule extends from the conjunctival fornix anteriorly to the optic nerve posteriorly.
B is correct. The cavity of each orbit is a truncated pyramid, with a flattened apex posteriorly and a trapezoidal base facing anterolaterally. The medial (nasal) walls of each orbit are parallel to each other, while the lateral (temporal) walls are offset approximately 45 degrees to the medial walls, making them perpendicular to each other.
A is incorrect. The retrobulbar cone is not sealed by any intermuscular membrane, so there is free communication between the intraconal and extraconal spaces.
C is incorrect. The average axial length of the adult eye is 24 mm but varies considerably across the human population, especially in myopic and hypermetropic individuals; that is why it needs to be individually measured prior to surgery.
D is incorrect. The abducens nerve (the sixth cranial nerve) usually travels outside the muscular cone.
E is incorrect. The Tenon’s capsule extends from the corneal limbus to the optic nerve.
Important considerations in determining the type of anesthetic technique for a given ophthalmic procedure include:
A. The preferences of the surgeon
B. The need for akinesia of the eye