Anesthetics in Ophthalmology — MCQs
What is the current medical recommendation regarding topical lignocaine use for teething pain relief in infants?
Ocular effects that include mydriasis are characteristic of which of the following drugs?
Retrobulbar injection of xylocaine blocks all of the following except:
In spinal anesthesia, the needle is pierced up to which space?
What is the commonly used concentration of tetracaine for topical anesthesia in minor ophthalmic procedures?
Which of the following anesthetics is known to increase intraocular pressure?
All of the following drugs increase the risk of postoperative nausea and vomiting after squint surgery in children except?
An 8-year-old child presents with gradual reduction in vision in the right eye. Family history of similar presentation was elicited on the maternal side. On examination, on right side direct light reflex is absent and consensual light reflex is present. Fundus examination was performed. What is the diagnosis?
Which of the following drugs possesses similar cycloplegic action and is a more potent mydriatic than atropine?
Which of the following drugs is used as adjunct therapy for the treatment of fungal corneal ulcer?
Anesthetics in Ophthalmology Indian Medical PG Practice Questions and MCQs
Question 1: What is the current medical recommendation regarding topical lignocaine use for teething pain relief in infants?
- A. Once a day
- B. Twice a day
- C. Three or four times a day.
- D. Topical lignocaine is contraindicated in teething (Correct Answer)
Explanation: ***Topical lignocaine is contraindicated in teething*** - Current medical recommendations strongly advise against the use of **topical lignocaine** for **teething pain relief** in infants. - This is due to the risk of **systemic absorption**, which can lead to serious **adverse effects** such as seizures, cardiac arrest, and brain injury, even with small doses. *Once a day* - This recommendation is incorrect because **topical lignocaine** is not considered safe for daily use in infants for teething due to potential toxicity. - Even infrequent use carries risks of **systemic toxicity** in infants whose smaller body mass and developing metabolic systems make them more vulnerable. *Twice a day* - Administering **topical lignocaine twice a day** for teething is not medically recommended and increases the risk of **adverse systemic effects**. - There is a lack of evidence supporting the safety and efficacy of repeated daily application of lignocaine for this indication in infants. *Three or four times a day.* - Frequent application of **topical lignocaine** (three or four times a day) significantly elevates the risk of **lignocaine toxicity** in infants, which can be life-threatening. - Such usage exceeds any conceivable safe therapeutic window and is strictly advised against by health authorities.
Question 2: Ocular effects that include mydriasis are characteristic of which of the following drugs?
- A. phenylephrine (alpha agonist) (Correct Answer)
- B. neostigmine (cholinesterase inhibitor)
- C. phentolamine (alpha blocker)
- D. mecamylamine (ganglionic blocker)
Explanation: ***phenylephrine (alpha agonist)*** - **Phenylephrine** is a direct-acting **alpha-1 adrenergic agonist** that causes contraction of the **pupillary dilator muscle**, leading to **mydriasis** (pupil dilation). [1] - It is frequently used clinically to dilate pupils for **ophthalmologic examinations** due to its selective action on alpha-1 receptors in the eye. [2] *neostigmine (cholinesterase inhibitor)* - **Neostigmine** inhibits acetylcholinesterase, increasing acetylcholine at the neuromuscular junction and muscarinic receptors. This leads to **miosis** (pupil constriction), not mydriasis. - Its ophthalmic use is primarily for treating **glaucoma** by improving aqueous humor outflow through cholinergic effects on the ciliary muscle. *phentolamine (alpha blocker)* - **Phentolamine** is a **non-selective alpha-adrenergic antagonist** that blocks both alpha-1 and alpha-2 receptors. - Alpha-1 receptor blockade in the eye would relax the pupillary dilator muscle, leading to **miosis** or prevention of mydriasis, not its induction. *mecamylamine (ganglionic blocker)* - **Mecamylamine** is a **ganglionic blocker** that antagonizes nicotinic receptors in both sympathetic and parasympathetic ganglia. - Blocking parasympathetic ganglia can cause some mydriasis, but ganglionic blockers have widespread, non-selective autonomic effects and are not primarily used for isolated mydriasis.
Question 3: Retrobulbar injection of xylocaine blocks all of the following except:
- A. 3rd cranial nerve
- B. 4th cranial nerve (Correct Answer)
- C. 6th cranial nerve
- D. Ciliary nerves and ciliary ganglion
Explanation: ***4th cranial nerve*** - The **trochlear nerve (CN IV)** innervates the **superior oblique muscle** and has a unique superior and anterior course in the orbit, making it less accessible to retrobulbar injections. - Its location relative to the muscle cone and globe means a retrobulbar injection, which typically aims to block nerves within the muscle cone, often misses it. *3rd cranial nerve* - The **oculomotor nerve (CN III)** supplies most of the extraocular muscles and travels within the **muscle cone**, where retrobulbar anesthetic is deposited. - It is reliably blocked by a retrobulbar injection, causing akinesia of the muscles it innervates. *6th cranial nerve* - The **abducens nerve (CN VI)** innervates the **lateral rectus muscle** and is located within the **muscle cone**, making it susceptible to retrobulbar block. - Anesthetic diffusion within the cone effectively blocks this nerve, leading to paralysis of the lateral rectus. *Ciliary nerves and ciliary ganglion* - The **short ciliary nerves** and **ciliary ganglion** are located in the retrobulbar space, typically within the muscle cone or close to it. - Anesthetic solution injected retrobulbarly readily diffuses to these structures, blocking sensory input from the cornea and iris, as well as parasympathetic innervation to the pupil and ciliary body.
Question 4: In spinal anesthesia, the needle is pierced up to which space?
- A. Subarachnoid space (Correct Answer)
- B. Intrathecal space
- C. Epidural space
- D. Subdural space
Explanation: ***Subarachnoid space*** - In **spinal anesthesia**, the anesthetic agent is injected directly into the **cerebrospinal fluid (CSF)**, which is located in the subarachnoid space. - This space is targeted to achieve rapid and widespread blockade of spinal nerves, leading to anesthesia and paralysis below the level of injection. *Epidural space* - The **epidural space** is located outside the **dura mater** and contains fat and blood vessels; it is targeted in **epidural anesthesia**, not spinal anesthesia. - Anesthetic agents in the epidural space provide a slower onset and a more segmental block compared to spinal anesthesia. *Intrathecal space* - The term **intrathecal space** broadly refers to the space containing CSF, which includes the subarachnoid space, but is a less precise anatomical term for the site of injection in spinal anesthesia. - While technically correct in referring to an injection into the CSF, "subarachnoid space" is the specific anatomical term for where the needle tip rests. *Subdural space* - The **subdural space** is a potential space between the **dura mater** and the **arachnoid mater**; it is not the intended target for either spinal or epidural anesthesia. - Accidental injection into the subdural space during spinal or epidural procedures can lead to an unpredictable block with delayed onset and variable spread.
Question 5: What is the commonly used concentration of tetracaine for topical anesthesia in minor ophthalmic procedures?
- A. 1%
- B. 0.5% (Correct Answer)
- C. 2%
- D. 0.25%
Explanation: ***0.5%*** - **Tetracaine 0.5%** is the standard and most commonly used concentration for **topical ocular anesthesia** in minor ophthalmic procedures. - This concentration provides effective and rapid onset topical anesthesia for procedures like tonometry, foreign body removal, and gonioscopy with minimal side effects. *1%* - **Tetracaine 1%** is a higher concentration not typically used for routine topical ophthalmic anesthesia due to an increased risk of **epithelial toxicity** and other side effects. - While it would provide more potent anesthesia, its use is generally limited to specific cases where stronger anesthesia is needed and the benefits outweigh the risks. *2%* - **Tetracaine 2%** is an even higher concentration, rarely used in ophthalmology because of a significantly increased risk of **corneal damage** and other ocular surface complications. - This concentration is considered too strong for topical use in the eye and could lead to prolonged epithelial defects. *0.25%* - **Tetracaine 0.25%** is a lower concentration that may not provide sufficient depth or duration of anesthesia for most minor ophthalmic procedures. - While it would have a lower risk of toxicity, its **suboptimal anesthetic effect** makes it less commonly used than 0.5%.
Question 6: Which of the following anesthetics is known to increase intraocular pressure?
- A. Thiopental
- B. Alfentanil
- C. Ketamine (Correct Answer)
- D. Propofol
Explanation: ***Ketamine*** - **Ketamine** is known to increase **intraocular pressure (IOP)**, making it generally avoided in patients with **glaucoma** or those undergoing ocular surgery. - This effect is due to its influence on sympathetic nervous system activity and extraocular muscle tone. *Thiopental* - **Thiopental**, a barbiturate, typically causes a **reduction in intraocular pressure**, which can be beneficial in certain ocular procedures. - Its mechanism involves decreasing cerebral blood flow and metabolic rate, indirectly leading to a decrease in IOP. *Alfentanil* - **Alfentanil**, an opioid, generally has **minimal to no significant effect on intraocular pressure**. - Its primary actions are analgesia and sedation, without direct impact on oculomotor tone or fluid dynamics. *Propofol* - **Propofol** is known to **decrease intraocular pressure**, making it a favorable agent for ophthalmic surgery. - This effect is attributed to a reduction in cerebral blood flow and an inhibition of aqueous humor production.
Question 7: All of the following drugs increase the risk of postoperative nausea and vomiting after squint surgery in children except?
- A. Halothane
- B. Propofol (Correct Answer)
- C. Nitrous Oxide
- D. Opioids
Explanation: ***Propofol*** - Propofol is known to have **antiemetic properties** and is often used to reduce the incidence of postoperative nausea and vomiting (PONV). - Its mechanism involves modulating **GABA-A receptors** and potentially other pathways that suppress emetic responses. *Halothane* - **Inhalational anesthetics** like halothane are a significant risk factor for PONV, particularly in children and following surgeries like squint repair. - They tend to increase PONV by directly stimulating the **chemoreceptor trigger zone** and altering gut motility. *Opioids* - Opioids, commonly used for postoperative pain control, are a well-known cause of **nausea and vomiting**. - They activate **opioid receptors** in the chemoreceptor trigger zone and the gastrointestinal tract, leading to emesis and delayed gastric emptying. *Nitrous Oxide* - The use of **nitrous oxide** as part of a general anesthetic regimen has been consistently associated with an increased risk of PONV. - It is believed to contribute to PONV by increasing the risk of **bowel distension** and stimulating neurotransmitter release involved in emesis.
Question 8: An 8-year-old child presents with gradual reduction in vision in the right eye. Family history of similar presentation was elicited on the maternal side. On examination, on right side direct light reflex is absent and consensual light reflex is present. Fundus examination was performed. What is the diagnosis?
- A. ICSOL
- B. Devic's disease
- C. Iritis
- D. Optic atrophy (Correct Answer)
Explanation: ***Optic atrophy*** - The clinical finding of **gradual reduction in vision**, **absent direct light reflex** (indicating an afferent pupillary defect), and **present consensual light reflex** in the affected eye confirms optic nerve pathology. - The fundus image shows **optic disc pallor**, indicating loss of retinal ganglion cell axons, which is characteristic of optic atrophy. - The **positive family history on the maternal side** in an 8-year-old child strongly suggests **hereditary optic atrophy** (such as Leber's Hereditary Optic Neuropathy or Dominant Optic Atrophy), making this the most likely diagnosis. *ICSOL* - **Intracranial space-occupying lesions** can cause compressive optic neuropathy and secondary optic atrophy, but typically present with other neurological signs such as headache, papilledema, or focal neurological deficits. - While possible, the strong family history and isolated unilateral presentation in a child make hereditary optic atrophy more likely than an acquired ICSOL. *Devic's disease* - **Devic's disease** (Neuromyelitis Optica Spectrum Disorder) involves optic neuritis and transverse myelitis, typically presenting with acute, painful, often bilateral vision loss along with spinal cord symptoms. - The gradual, unilateral vision loss with established optic disc pallor suggests chronic nerve damage rather than the acute inflammatory process seen in Devic's disease. - Family history is not a typical feature of NMO. *Iritis* - **Iritis** (anterior uveitis) is an inflammatory condition of the iris characterized by eye pain, redness, photophobia, and decreased vision due to inflammation. - Examination would reveal inflammatory cells in the anterior chamber, circumcorneal congestion, and possibly posterior synechiae—not optic disc pallor. - Iritis does not cause afferent pupillary defects or optic nerve damage as the primary pathology.
Question 9: Which of the following drugs possesses similar cycloplegic action and is a more potent mydriatic than atropine?
- A. Hyoscine (Correct Answer)
- B. Tropicamide
- C. Homatropine
- D. All of the above
Explanation: **Explanation:** The correct answer is **Hyoscine (Scopolamine)**. **Why Hyoscine is the correct answer:** Hyoscine is a belladonna alkaloid that acts as a competitive antagonist at muscarinic receptors. In terms of ocular potency, it is significantly more potent than atropine on a weight-for-weight basis. While it produces a **similar degree of cycloplegia** (paralysis of the ciliary muscle), it is a **more potent mydriatic** (pupillary dilator) than atropine. Its duration of action (3–7 days) is shorter than that of atropine (7–10 days), making it a useful alternative when a potent but slightly shorter-acting cycloplegic is required. **Analysis of Incorrect Options:** * **Tropicamide:** This is the shortest-acting mydriatic (duration 4–6 hours). While it is excellent for fundus examination, its cycloplegic action is much weaker and shorter than atropine. * **Homatropine:** A semi-synthetic derivative that is 10 times less potent than atropine. It has a shorter duration of action (1–3 days) and is primarily used in the treatment of anterior uveitis to prevent synechiae without the prolonged blurriness of atropine. **High-Yield Clinical Pearls for NEET-PG:** * **Potency Order:** Hyoscine > Atropine > Homatropine. * **Duration of Action (Cycloplegia):** Atropine (7–10 days) > Hyoscine (3–7 days) > Homatropine (1–3 days) > Cyclopentolate (24 hours) > Tropicamide (6 hours). * **Drug of Choice:** Atropine is the drug of choice for refraction in children <5 years (due to strong accommodation), while Homatropine/Cyclopentolate is preferred for older children. * **Side Effect:** Systemic absorption of atropine in children can lead to "Atropine flushing," fever, and tachycardia.
Question 10: Which of the following drugs is used as adjunct therapy for the treatment of fungal corneal ulcer?
- A. Atropine eye drops (Correct Answer)
- B. Dexamethasone eye drops
- C. Pilocarpine eye drops
- D. Lidocaine
Explanation: **Explanation:** In the management of a fungal corneal ulcer, **Atropine (1%) eye drops** serve as a vital adjunct therapy. The primary medical rationale for its use is to manage **secondary ciliary body inflammation (iridocyclitis)**, which is a common complication of deep corneal ulcers. **Why Atropine is the Correct Answer:** 1. **Ciliary Muscle Relaxation:** It acts as a cycloplegic, paralyzing the ciliary muscle to relieve the intense pain caused by ciliary spasms. 2. **Prevention of Synechiae:** As a potent mydriatic, it dilates the pupil, preventing the formation of posterior synechiae (adhesion of the iris to the lens). 3. **Reduction of Exudation:** It reduces the permeability of iris vessels, thereby decreasing the inflammatory exudate in the anterior chamber. **Why Other Options are Incorrect:** * **Dexamethasone:** Steroids are strictly **contraindicated** in active fungal ulcers as they promote fungal growth, inhibit collagen synthesis (leading to corneal perforation), and suppress the local immune response. * **Pilocarpine:** This is a miotic. It would worsen the pain by causing ciliary muscle contraction and increase the risk of pupillary block and synechiae formation. * **Lidocaine:** While a local anesthetic, it is not used as a therapeutic adjunct; chronic use is toxic to the corneal epithelium and can delay healing. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC) for Fungal Keratitis:** Natamycin (5% suspension) is the first-line topical antifungal. * **The "Steroid Rule":** Never use steroids in a dendritic (Herpetic) or fungal ulcer. * **Atropine Duration:** It is the longest-acting cycloplegic (effect lasts 7–10 days). * **Fungal Ulcer Features:** Look for "feathery margins," "satellite lesions," and a "dry/leathery" appearance in clinical vignettes.
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