Ocular Toxicology — MCQs
True about acid injury to eye are all except?
A 45 year old male, known case of Rheumatoid arthritis is on a monotherapy since many years. Symptoms of RA are controlled but suddenly patient develops blurring of vision. Which of the following drug is responsible for sudden effect on vision?
A patient diagnosed with Rheumatoid arthritis was on medications. After 2 years, he developed a blurring vision and was found to have corneal opacity. Which drug is most likely to cause this?
Which TB drug causes optic neuritis as a side effect?
Injection of muscarinic agonist in conjunctival sac will lead to all of the following except
The characteristic finding in chloroquine retinopathy is
Mydriasis is caused by:
Which among the following is the BEST irrigating fluid during ECCE?
All are manifestation of dengue virus infection in eye except?
Which of the following intraocular foreign bodies causes severe toxicity and needs to be removed promptly?
Ocular Toxicology Indian Medical PG Practice Questions and MCQs
Question 1: True about acid injury to eye are all except?
- A. more destructive than alkali injuries (Correct Answer)
- B. steroids are used to control inflammation
- C. makes a barrier and prevent deeper penetration
- D. glaucoma is most preventable complication following acid injury
Explanation: ***more destructive than alkali injuries*** - This statement is **false**. **Alkali burns** are generally more severe than acid burns because alkalis have **liquefactive necrosis**, which allows them to penetrate deeper into ocular tissues. - Acids cause **coagulative necrosis**, which forms a protective barrier that limits further penetration, making them typically less destructive than alkali injuries. *steroids are used to control inflammation* - **Topical corticosteroids** are commonly used in the management of ocular chemical burns, including acid injuries, to help **control inflammation** and reduce the risk of secondary complications. - However, their use must be carefully monitored due to potential side effects like increased intraocular pressure and delayed corneal healing. *makes a barrier and prevent deeper penetration* - **Acidic substances** cause **coagulative necrosis** of the superficial tissues, which creates a protective barrier of denatured proteins. - This barrier helps to prevent the acid from penetrating deeper into the ocular structures, thus often limiting the extent of damage compared to alkali burns. *glaucoma is most preventable complication following acid injury* - **Glaucoma** is indeed a significant complication of ocular acid injuries and can be prevented through **immediate copious irrigation**, control of inflammation, and monitoring of intraocular pressure. - While various complications can occur (corneal opacification, symblepharon, limbal stem cell deficiency), glaucoma prevention through early intervention and appropriate medical management is a key focus in acute management, making this statement acceptable as true.
Question 2: A 45 year old male, known case of Rheumatoid arthritis is on a monotherapy since many years. Symptoms of RA are controlled but suddenly patient develops blurring of vision. Which of the following drug is responsible for sudden effect on vision?
- A. Methotrexate
- B. Hydroxychloroquine (Correct Answer)
- C. Sulfasalazine
- D. Leflunomide
Explanation: ***Hydroxychloroquine*** - **Hydroxychloroquine** [1] is known to cause **retinal toxicity** (maculopathy) as a dose-dependent, long-term side effect, leading to **blurring of vision** and other visual disturbances. - Patients on long-term hydroxychloroquine therapy require regular **ophthalmological screening** to detect and prevent irreversible vision loss. *Methotrexate* - **Methotrexate** is a common DMARD used in RA [1], but its ocular side effects are typically rare and less severe, usually involving **conjunctivitis** or **periorbital edema**. - It does not commonly cause **maculopathy** or sudden profound blurring of vision. *Sulfasalazine* - **Sulfasalazine** [1] can cause a range of side effects, including gastrointestinal issues and various hypersensitivity reactions. - Ocular side effects are infrequent and generally mild, such as **conjunctivitis** or **periorbital edema**, and not severe blurring of vision due to retinal damage. *Leflunomide* - **Leflunomide** is an immunosuppressive DMARD [1] whose common adverse effects include hepatotoxicity, gastrointestinal upset, and hypertension. - Significant **ocular toxicity** leading to blurring of vision, particularly retinal damage, is not a characteristic side effect of **leflunomide**.
Question 3: A patient diagnosed with Rheumatoid arthritis was on medications. After 2 years, he developed a blurring vision and was found to have corneal opacity. Which drug is most likely to cause this?
- A. Sulfasalazine
- B. Leflunomide
- C. Chloroquine (Correct Answer)
- D. Methotrexate
Explanation: ***Chloroquine*** - **Chloroquine (and hydroxychloroquine)** can accumulate in the **cornea**, leading to **corneal opacity** (vortex keratopathy or cornea verticillata) and **retinopathy**, manifesting as blurring vision. - While corneal changes are usually reversible upon discontinuation, the retinal toxicity, particularly **maculopathy** (bull's eye maculopathy), can be permanent and severe. *Sulfasalazine* - Common side effects include **gastrointestinal upset**, headache, skin rash, and **bone marrow suppression**. - It is not typically associated with **corneal opacity** or significant ocular toxicity. *Leflunomide* - Known for side effects such as **hepatotoxicity**, gastrointestinal issues (diarrhea), **alopecia**, and **hypertension**. - **Ocular side effects** like corneal opacity are not characteristic of leflunomide use. *Methotrexate* - Primary side effects include **bone marrow suppression**, **hepatotoxicity**, **mucositis**, and **pulmonary fibrosis**. - Although it can cause ocular side effects like **conjunctivitis**, it is not a common cause of **corneal opacity**.
Question 4: Which TB drug causes optic neuritis as a side effect?
- A. Isoniazid
- B. Pyrazinamide
- C. Rifampicin
- D. Ethambutol (Correct Answer)
Explanation: ***Ethambutol*** - **Ethambutol** is known to cause **optic neuritis**, leading to **decreased visual acuity** and impaired **red-green color discrimination**. - This side effect is **dose-dependent** and usually **reversible** upon discontinuing the drug, though permanent damage can occur with prolonged use. *Isoniazid* - **Isoniazid** is primarily associated with **peripheral neuropathy** and **hepatotoxicity**, which can be mitigated with **pyridoxine (vitamin B6)** supplementation. - While visual disturbances can occur, **optic neuritis** is not its most characteristic or frequent ocular side effect. *Pyrazinamide* - The main side effects of **pyrazinamide** include **hepatotoxicity** and **hyperuricemia**, which can lead to **gouty arthritis**. - It does not typically cause **optic neuritis** or other significant ocular complications. *Rifampicin* - **Rifampicin** is well-known for causing **hepatotoxicity**, **red-orange discoloration of body fluids** (urine, tears, sweat), and various **drug interactions** due to enzyme induction. - Ocular side effects like **optic neuritis** are not a common or characteristic adverse effect of rifampicin.
Question 5: Injection of muscarinic agonist in conjunctival sac will lead to all of the following except
- A. Miosis
- B. Conjunctival and uveal hyperemia
- C. Decreased secretion from ciliary epithelium (Correct Answer)
- D. Ciliary spasm
Explanation: ***Decreased secretion from ciliary epithelium*** - Muscarinic agonists **do NOT significantly decrease** aqueous humor secretion from the ciliary epithelium. - The primary mechanism for reducing intraocular pressure with drugs like **pilocarpine** is by **increasing outflow** of aqueous humor through the trabecular meshwork via contraction of the ciliary muscle, NOT by decreasing production. - Therefore, "decreased secretion from ciliary epithelium" is the correct answer to this "EXCEPT" question—it does NOT occur with muscarinic agonists. *Miosis* - Muscarinic agonists cause the **pupillary sphincter muscle** (which has M3 receptors) to contract, leading to **pupil constriction** (miosis). - This effect opens the trabecular meshwork and facilitates aqueous humor drainage. *Conjunctival and uveal hyperemia* - Muscarinic agonists cause **vasodilation** in the conjunctival and uveal blood vessels, leading to increased blood flow and **redness** (hyperemia). - This is a common side effect associated with topical application of cholinergic drugs to the eye. *Ciliary spasm* - Muscarinic agonists stimulate the **ciliary muscle** (which has M3 receptors), causing it to contract. - This contraction leads to **accommodation spasm**, resulting in blurred distance vision and brow ache, which is a common adverse effect in younger patients.
Question 6: The characteristic finding in chloroquine retinopathy is
- A. Retinopathy that resolves immediately after stopping the drug
- B. Bull's eye maculopathy (Correct Answer)
- C. Primarily CNS involvement rather than retinal
- D. Vision loss that is usually reversible
Explanation: ***Correct: Bull's eye maculopathy*** - **Bull's eye maculopathy** is the **pathognomonic (characteristic) finding** of chloroquine retinopathy - This distinctive pattern shows a ring of pigmentary changes surrounding the fovea, resembling a bull's eye target - Results from **chloroquine accumulation in retinal pigment epithelium (RPE) cells**, leading to selective damage in the macular region - This finding is specifically tested on screening examinations like **fundus autofluorescence and spectral-domain OCT** *Incorrect: Primarily CNS involvement rather than retinal* - Chloroquine **primarily affects the retina**, not the CNS - this is why it's called chloroquine **retinopathy** - While chloroquine can cause CNS effects (psychosis, seizures) at toxic doses, the main concern with chronic use is **irreversible retinal damage** - Regular **ophthalmologic screening** is mandatory precisely because retinal toxicity is the primary limiting side effect *Incorrect: Vision loss that is usually reversible* - Vision loss from chloroquine retinopathy is **typically IRREVERSIBLE** once significant damage occurs - The drug continues to be released from tissue stores even after discontinuation due to its **extremely long half-life** (weeks to months) - Early detection through screening is critical to **prevent irreversible blindness** - This is why regular monitoring with fundoscopy, visual field testing, and OCT is essential for patients on long-term therapy *Incorrect: Retinopathy that resolves immediately after stopping the drug* - Chloroquine retinopathy can actually **progress even after drug cessation** - a phenomenon called "rebound toxicity" - Due to chloroquine's **long tissue half-life** and continued release from tissue stores (especially in RPE), retinal damage may continue or worsen for months after stopping - The drug accumulates in melanin-containing tissues and is released slowly over time - This underscores the importance of **early detection and prevention** rather than relying on drug discontinuation to halt progression
Question 7: Mydriasis is caused by:
- A. Horner syndrome
- B. Atropine (Correct Answer)
- C. Neurosyphilis
- D. Organophosphorus poisoning
Explanation: ***Atropine*** - **Atropine** is an **anticholinergic drug** that blocks the action of **acetylcholine** at **muscarinic receptors** in the iris sphincter muscle. - This blockage leads to the relaxation of the **sphincter muscle**, causing **pupil dilation (mydriasis)** and loss of accommodation. *Horner syndrome* - **Horner syndrome** results from damage to the **sympathetic nervous pathway** to the eye. - It classically presents with a triad of **miosis** (constricted pupil), ptosis (drooping eyelid), and **anhydrosis** (decreased sweating) on the affected side. *Neurosyphilis* - **Neurosyphilis** can cause various neurological manifestations, including **Argyll Robertson pupils**. - **Argyll Robertson pupils** are characterized by **small, irregular pupils** that *accommodate but do not react to light* (miosis rather than mydriasis). *Organophosphorus poisoning* - **Organophosphorus compounds** inhibit **acetylcholinesterase**, leading to an excess of acetylcholine at cholinergic synapses. - This overstimulation causes **miosis** (pinpoint pupils), along with other cholinergic symptoms such as salivation, lacrimation, and bradycardia.
Question 8: Which among the following is the BEST irrigating fluid during ECCE?
- A. Ringer lactate
- B. Normal saline
- C. Balanced salt solution
- D. Balanced salt solution + glutathione (Correct Answer)
Explanation: ***Balanced salt solution + glutathione*** - **Balanced salt solution with glutathione** is considered the best irrigating fluid for ECCE because it closely mimics the **natural aqueous humor**, maintaining corneal endothelial cell health and viability during surgery. - The addition of **glutathione** provides an antioxidant effect, protecting the corneal endothelium from oxidative stress and maintaining its metabolic function during prolonged irrigation. *Ringer lactate* - While **Ringer's lactate** is a balanced electrolyte solution, it lacks the specific components and buffering capacity present in specialized ophthalmic irrigating solutions. - It does not contain **glutathione** or other agents crucial for maintaining corneal endothelial viability and function during intraocular surgery. *Normal saline* - **Normal saline (0.9% NaCl)** lacks essential ions (calcium, magnesium, potassium) and appropriate pH buffering required for intraocular use. - Its use can lead to **corneal edema** and endothelial cell damage due to ionic imbalance and the absence of protective components found in balanced salt solutions. *Balanced salt solution* - A **plain balanced salt solution (BSS)** is a significant improvement over normal saline or Ringer's lactate as it is physiologically balanced for intraocular use, containing essential electrolytes. - However, it lacks the **antioxidant properties of glutathione**, which provides superior protection to corneal endothelial cells during extended surgical procedures.
Question 9: All are manifestation of dengue virus infection in eye except?
- A. Cataract (Correct Answer)
- B. Vitreous hemorrhage
- C. Maculopathy
- D. Optic neuritis
Explanation: ***Cataract*** - **Cataracts** are primarily associated with aging, congenital factors, trauma, or long-term steroid use, not directly with acute dengue virus infection. - While dengue can cause various ocular manifestations, the formation of cataracts is a **chronic process** that does not fit the typical acute or subacute presentation of dengue-related eye complications. *Vitreous hemorrhage* - **Vitreous hemorrhage** can occur in dengue due to associated **thrombocytopenia** and coagulation abnormalities, leading to bleeding in the eye. - Severe dengue can induce systemic vasculopathy and bleeding tendencies, which may manifest as intraocular hemorrhage. *Maculopathy* - **Dengue maculopathy** is a recognized complication, often presenting as macular edema, hemorrhage, or foveolitis, leading to visual impairment. - This is thought to be due to direct viral effects, immune-mediated responses, or vasculitis affecting the retinal microvasculature. *Optic neuritis* - **Optic neuritis** following dengue infection has been reported, characterized by inflammation of the optic nerve, causing acute vision loss. - This is considered to be an **immune-mediated post-infectious complication** rather than a direct viral cytopathic effect on the nerve.
Question 10: Which of the following intraocular foreign bodies causes severe toxicity and needs to be removed promptly?
- A. Aluminium
- B. Copper (Correct Answer)
- C. Chromium
- D. Nickel
Explanation: ***Copper*** - **Copper foreign bodies** cause **chalcosis bulbi**, a severe toxic reaction characterized by: - **Greenish discoloration** of anterior lens capsule and cornea - **Retinal degeneration** and pigmentary changes - **Vision loss** if not removed promptly - **Pure copper is highly toxic** and mandates immediate surgical removal to prevent irreversible ocular damage *Aluminium* - **Aluminum foreign bodies** are **inert** and well-tolerated in the eye - Generally do not cause significant inflammatory reactions or toxicity - Removal not required unless causing mechanical complications *Chromium* - **Chromium foreign bodies** are **inert** and non-toxic - Do not cause significant inflammation or tissue damage - Removal typically not necessary unless mechanically disruptive *Nickel* - **Nickel foreign bodies** are **relatively inert** within the eye - Rarely cause toxic reactions or significant inflammation - Removal usually not required unless causing mechanical irritation
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