TOPICAL VS. BLOCK With topical anesthesia (left), patients should be sedated enough that they feel comfortable and relaxed, but not so sedated that they fall asleep. While blocks (right) have a higher risk for complications, some surgeons still feel they're safer overall.

What's the best way to anesthetize cataract patients — topical anesthesia or nerve blocks? Regardless of your preference, intravenous sedation given beforehand helps reduce anxiety and keep patients comfortable. It also helps patients hold relatively still, as long as you don't administer too large of a dose. Administer too much and patients may fall asleep and either snore — moving their heads slightly when they do — or suddenly wake up and jerk their heads, momentarily unaware of their whereabouts. Beyond that, the topical block debate depends on several factors. Let's look at some of the considerations.

Is eye movement OK?
If you choose topical anesthesia, patients will be able to move their eyes, which is fine as far as many surgeons are concerned. The key is that those patients are properly sedated and comfortable. But if you use topical without sedation, you may need to supplement it with an intracameral injection of bupivacaine — an injection within the anterior chamber of the eye. Typically, that's enough to keep patients comfortable, because the procedure will likely be completed well before the anesthetic wears off. On the other hand, surgeons who prefer no eye movement will likely opt for blocks, as will surgeons performing longer or more complex cases. The speed at which the surgeon works is also a consideration. A phacoemulsification with an intraocular lens implant may take anywhere from 10 to 30 minutes.

Block types
Although other types of blocks are also used occasionally — including the Sub-Tenon's (episcleral) block and the van Lint (lid) block — the blocks of choice for cataract surgery remain the retrobulbar and the peribulbar.

• Retrobulbar blocks. They involve injecting local anesthetic inside the muscle cone. They block the ciliary nerves, ciliary ganglion, and cranial nerves III, IV and VI. They're usually deeper than peribulbar blocks and require less volume to attain the goal of no movement and no pain.
• Peribulbar blocks. They're usually injected above or below the orbit. The anesthetic solution is deposited within the orbit, but doesn't enter the muscle cone, which makes them safer overall than retrobulbar blocks.

Incidentally, general anesthesia should probably be used only as a last resort — with pediatric patients and/or with patients who can't tolerate blocks, or who can't hold still. More on that later.

Pros and cons of topical
With topical anesthesia, chemosis and periorbital hematoma are minimal, and subconjunctival hemorrhage is rare. Patients may worry that they'll feel pain, but most are amenable when the method is thoroughly explained. And generally, topical is significantly less painful than the administration of blocks. When patients understand that they won't be completely asleep, but that they'll feel very comfortable and relaxed, both surgeons and patients benefit. As noted, supplementing with appropriate sedation improves the topical experience. The risks associated with topical are minimal and it provides rapid eye recovery immediately after surgery.

While topical is safe and comfortable, it requires a cooperative patient. Some patients who agree to it may grow anxious if they feel the slightest tension on or around the eye, or if they feel manipulation of the iris or distention of the anterior chamber. They might even become restless to the point of needing more sedation, which can make matters worse, even if intracameral injection is done. Also, since the eye still moves, patients may not focus properly. If they're sufficiently awake, they can be directed to overcome this obstacle. But if the level of discomfort and non-cooperation becomes critical, it may even be necessary to perform a block intraoperatively.

Pros and cons of blocks
Both retrobulbar and peribulbar blocks have advantages. Retrobulbar blocks, in particular, can provide adequate anesthesia, akinesia and control of intraocular pressure. With complex procedures or corneal stretching, both offer complete anesthesia. They also eliminate the need for topical administration or intracameral injection into the chamber, which may distort it. Blocks also last longer and offer some post-operative analgesia. While blocks have more contraindications and complications, some surgeons feel they're safer and permit smoother operations. They can be administered by well-trained and experienced anesthesia providers.

Many patients dread the idea of having "a needle stuck in my eye," even when they're assured that the needle goes outside the eye, not into it. They must clearly understand that it's not that big a deal, that blocks have many benefits, and that they'll be sedated before the block is given. If they understand, most patients are agreeable. But unlike topical anesthesia, blocks carry many potential risks:

• Retrobulbar hemorrhage. This uncommon complication is caused by the puncturing of blood vessels in the retrobulbar space.
• Chemosis. This can be caused by rapid injection; minimize the risk by injecting slowly.
• Globe puncture. This can occur even when a blunt needle is used with a retrobulbar block.
• Contralateral eye spread. This usually occurs with peribulbar blocks. The anesthetic spreads and migrates to the contralateral eye.
• Optic nerve injection. Accidentally injecting anesthesia into the nerve sheath can lead to hemorrhage and vision loss.
• Oculocardiac response. Dysrhythmias such as bradycardia and junctional rhythm, and even asystole, can occur when the oculocardiac reflex is stimulated. Moreover, it can occur hours later.
• Central retinal artery occlusion. This is usually caused by retrobulbar hemorrhage and can lead to total vision loss if not treated.
• Brain stem amnesia. If you perforate the meningeal sheaths that surround the optic nerve and inject directly into the cerebrospinal fluid, it can cause convulsions, disorientation, aphasia, hemiplegia and cardiac arrest, all within a few minutes.
• Transient blindness. This usually goes away within hours, once the medication is completely out of the system.

SUBLINGUAL SEDATION
IV-Free Cataracts

UNDER THE TONGUE The MKO Melt sublingual tablet dissolves in a couple minutes and sedates patients for a couple hours.

Topical, block ... or tablet? The bruising and pain from an IV can be more traumatic than cataract surgery, but now you can skip IV sedation for cataract cases and instead give patients a new conscious sedation sublingual tablet called MKO Melt, which stands for midazolam-ketamine-ondansetron.

Patients place 1 or 2 of the small tablets under their tongue. MKO Melt typically dissolves within 2-5 minutes. The compound creates a consistent sedative effect that wears off after a couple hours and has patients ready for timely discharges, says its manufacturer, Imprimis Pharmaceuticals.

MKO Melt costs $25 for a 2-troche dose, says Imprimis, which launched the tablet earlier this year with the aim of giving ophthalmologists the option to go IV-free (Imprimis notes that some patients still may require an IV).

"We've been looking for a way to provide better sedation in an easier, more cost-effective and smoother way," says Y. Ralph Chu, MD, founder and medical director of Chu Vision Institute and Chu Surgery Center in Bloomington, Minn.

— Daniel Cook

In some situations, and for some patients, blocks shouldn't be used. In those cases, either topical or general anesthesia is a better choice.

• Children. They usually shouldn't be done on patients under 15 years of age.
• Long procedures. Procedures that last longer than 90 minutes.
• Long bleeding times/high INR. This increases risk if a vessel is punctured. International Normalized Ratio (INR) is a measure of how much longer it takes the blood to clot when oral anticoagulation is used.
• Mentally impaired patients. They usually find it difficult to hold still and cooperate, especially with head movement.
• Other considerations. Some patients aren't candidates either because they have other comorbidities, or because they won't agree to the procedure.

Peribulbar blocks are safer overall than retrobulbar blocks. They're less likely to cause retrobulbar hemorrhage or perforate the globe, and their potential for dural injection is lower, because the anesthetic is injected outside the muscle cone. But they also have disadvantages. There may be less akinesia, more volume required and a higher instance of chemosis, which can distort the operative site.

The choice
There's no right or wrong selection. In most cases, both topical and blocks are effective, and neither is likely to nudge the other out of existence in the near future (see "IV-Free Cataracts" for a new alternative to topical and blocks). An ophthalmologist's choice is likely to be driven by surgical training, his comfort level and the complexity of the procedure. Surgeons usually opt totally for one or the other, varying only when patients and contraindications call for it. Both topical and block anesthesia have the potential for harm if patients are allergic to the anesthetic. Be sure to get a thorough history regarding past experience with local anesthetics. OSM