• llustration by Mark M. Miller
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    Comprehensive Ophthalmology

    Retrobulbar block. A 1.25-inch, 25- or 27-gauge needle is inserted at the inferotemporal orbital rim at a point in line with the lateral limbus (A). The needle is advanced tangential to the globe and parallel to the bony floor of the orbit, which inclines at an angle of 10 degrees from the transverse plane (B1). Once the equator of the globe is passed, the needle is redirected upward and medially into the muscle cone (B2). Either a transcutaneous (B) or transconjunctival (C) approach may be used. (D) The midsagittal plane of the eye should not be crossed because the optic nerve lies on the nasal side of this plane.