(c) Retrobulbar injection. Two Luer-Lok 2-or 5-ml syringes or one 10-
ml syringe and two 24-gauge needles, 1-or 1 1/2-inch length.
(a) Tetracaine hydrochloride (Pontocaine hydrochloride ) in a 2
percent solution may be instilled into the eye before an operation. For local anesthesia
in adults, 2 percent lidocaine (Xylocaine ) with epinephrine hydrochloride in a 1:150,000
or 1:200,000 dilution is frequently used.
(b) Hyaluronidase (Wydase , Alidase) is commonly mixed with the
anesthetic solution (75u/10ml). The enzyme increases the diffusion of the anesthetic
through the tissue, thereby improving the effectiveness of the anesthetic nerve block.
For cataract surgery, an effective retrobulbar injection reduces intraocular pressure by
preventing positive muscle contraction, thus becoming a surgical safeguard against
vitreous loss. Hyaluronidase is nontoxic and is effective over a wide range of
(c) In cataract surgery, alpha chymotrypsin in a 1:5,000 or 1:10,000
solution may be used to dissolve the zonular fibers that suspend the cataract within the
eye. To produce eye muscle paralysis in intraocular surgery, tubocurarine chloride or
succinylcholine chloride may be administered intravenously by the anesthesiologist.
(d) Epinephrine in a 1:1,000 solution may be applied topically to
mucous membranes to decrease bleeding. Epinephrine in a 1:500,000 to 1:200,000
solution may be combined with injectable anesthetics to prolong the duration of
anesthesia. Epinephrine in a 1:1,000 solution is not used in local anesthetics because if
it were used in such concentrations, the patient could succumb to cardiac arrhythmia.
(4) Methods used for administration of local anesthetics. The three
methods of administration are instillation of eye drops, infiltration, and block or regional
(a) Instillation of eye drops. With the patient's face, tilted upward, the
first drop is placed in the lower cul-de-sac, and the following drops (number depends on
the type of operation to be performed) may be placed from above, with the patient
looking downward and the upper lid raised. However, the natural blinking of the lids
distributes the drug evenly on the eye surface, regardless of where the drop is placed.
When a toxic drug is instilled, the inner corner of the eyelids should be dried of
excessive fluid with a tissue or clean cotton ball after the instillation of each drop,
thereby minimizing systemic absorption of the drug. The tip of the applicator must not
touch the patient's skin or any part of the eye.
(b) Infiltration method. The surgeon injects the anesthetic solution
beneath the skin, beneath the conjunctiva, or into Tenon's capsule, depending on the