science

Retrobulbar block

Retrobulbar block is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Retrobulbar block rather than just read about it. In short: A retrobulbar block is a regional anesthetic nerve block in the retrobulbar space, which is the area located behind the globe of the eye. Injection of local anesthetic into this space constitutes the retrobulbar block.

Key takeaways

Retrobulbar block belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Retrobulbar block to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Retrobulbar block from memory before moving on to harder problems.

Reference excerpt

A retrobulbar block is a regional anesthetic nerve block in the retrobulbar space, which is the area located behind the globe of the eye. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia of the extraocular muscles by blocking cranial nerves II, III, and VI, thereby preventing movement of the globe. Cranial nerve IV lies outside the muscle cone, and therefore is not affected by the local anesthesia. As a result, intorsion of the eye is still possible. It also provides sensory anesthesia of the conjunctiva, cornea and uvea by blocking the ciliary nerves. This block is most commonly employed for cataract surgery, but also provides anesthesia for other intraocular surgeries.

Side effects and complications Complications associated with this block are either ocular or systemic. Local ocular complications include hematoma formation, optic nerve damage and perforation of the globe with possible blindness. Systemic complications include local anesthetic toxicity, brainstem anesthesia, and stimulation of the oculocardiac reflex. Most commonly, patients will report discomfort during the performance of the block, such as the sensation of the needle during insertion and/or pressure behind the eye during injection. In recent years, peribulbar block has become increasingly used because of its lower incidence of complications.

Technique Resuscitative equipment, monitoring and personnel must be immediately available prior to performance of this block. The retrobulbar block is performed with the patient either seated or supine and looking straight ahead. The head should be maintained in a neutral position. A needle (22–27 Gauge, 3 cm long) is inserted at the inferolateral border of the bony orbit and directed straight back until it has passed the equator of the globe. It is then directed medially and cephalad toward the apex of the orbit. Occasionally a 'pop' is felt as the needle tip passes through the muscle cone delineating the retrobulbar space. Following a negative aspiration for blood, 2–4 mLs of local anesthetic solution is injected and the needle is withdrawn. 2% Lidocaine (Xylocaine) and 0.5% to 0.75% bupivicaine (Marcaine) are two commonly used agents. Epinephrine, commonly mixed in with local anesthetics for vasoconstriction, is not used in seeing eyes as this can cause a central retinal artery occlusion. An enzyme, hyaluronidase, is frequently a component of the anaesthetic solution, as it accelerates and improves dispersal of the agent. Akinesia and anesthesia quickly ensue within minutes with a successful retrobulbar injection. Retrobulbar block can be used successfully for corneal transplantation but may require a supplemental facial nerve block. Retrobulbar block can block levator palpebrae muscle but not orbicularis oculi. Several techniques for facial nerve block can be used in conjunction with retrobulbar block.

Worked examples

Example 1 — a first encounter with Retrobulbar block

Start with the simplest possible case. Write down what Retrobulbar block claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Retrobulbar block before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Retrobulbar block ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Retrobulbar block

In research: Retrobulbar block appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Retrobulbar block in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Retrobulbar block is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cataract, Eye procedures, Ophthalmic drug administration, so understanding it makes those chapters shorter.
In everyday life: Look for Retrobulbar block outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Retrobulbar block in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Retrobulbar block means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Retrobulbar block out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Retrobulbar block in simple terms?

Why does Retrobulbar block matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Retrobulbar block?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Retrobulbar block.