Thermal and Radiation Injuries — MCQs
True about acid injury to eye are all except?
A patient presents with eye pain, redness, and blurred vision after sleeping in contact lenses. Fluorescein staining reveals a corneal ulcer. What is the most appropriate management?
The most serious alkali burns of the eye are produced by
A patient complains of an inability to read a newspaper, particularly in bright sunlight. What is the most likely diagnosis?
Most visually handicapping cataract is:
What is the most likely complication of the condition shown in the image below?
Which of the following is a true statement regarding the human eye?
In photophthalmia, which part of the eye is primarily affected?
What is the primary cause of snow blindness?
Which of the following statements regarding thermal injury is correct?
Thermal and Radiation Injuries 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 patient presents with eye pain, redness, and blurred vision after sleeping in contact lenses. Fluorescein staining reveals a corneal ulcer. What is the most appropriate management?
- A. Topical antibiotics (Correct Answer)
- B. Oral antibiotics
- C. Topical corticosteroids
- D. Saline irrigation
Explanation: ***Topical antibiotics*** - A **corneal ulcer**, especially in a contact lens wearer, is highly suspicious for **bacterial infection**, necessitating immediate and aggressive topical antibiotic therapy. - **Broad-spectrum antibiotics** (e.g., fluoroquinolones) are often started empirically and adjusted based on culture results. *Oral antibiotics* - **Systemic antibiotics** are generally not indicated for uncomplicated bacterial corneal ulcers, as they don't achieve sufficient concentrations in the cornea to be effective. - They may be considered for severe cases with limbal involvement or scleral extension, or if there is a concern for concurrent systemic infection. *Topical corticosteroids* - **Corticosteroids** are contraindicated in the initial management of suspected infectious corneal ulcers because they can suppress the immune response and worsen the infection. - They may be cautiously used later in treatment to reduce inflammation after the infection is well-controlled. *Saline irrigation* - While helpful for removing foreign bodies or debris, **saline irrigation alone** is insufficient to treat a bacterial corneal ulcer. - It does not eradicate the infection and delaying definitive antibiotic treatment can lead to severe complications.
Question 3: The most serious alkali burns of the eye are produced by
- A. Lime
- B. Liquid ammonia (Correct Answer)
- C. Caustic soda
- D. None of the options
Explanation: ***Liquid ammonia*** - **Liquid ammonia** produces the most severe alkali burns due to its small molecular size, which allows for rapid and deep penetration into ocular tissues. - Its high lipid solubility facilitates passage through cell membranes, leading to extensive tissue damage, including to the **cornea**, **lens**, and **ciliary body**. *Lime* - While **lime (calcium hydroxide)** causes significant alkali burns, its larger molecular size and lower lipid solubility limit its penetration compared to ammonia. - It often forms precipitates in superficial tissues, which can be mechanically removed, making its long-term effects less severe than ammonia. *Caustic soda* - **Caustic soda (sodium hydroxide)** is a strong alkali, causing severe burns by liquefaction necrosis. - However, its molecular characteristics and penetration depth are generally less extreme than that of liquid ammonia, resulting in slightly less severe damage. *None of the options* - This option is incorrect because **liquid ammonia** is indeed known to cause the most serious alkali burns of the eye due to its unique chemical properties.
Question 4: A patient complains of an inability to read a newspaper, particularly in bright sunlight. What is the most likely diagnosis?
- A. Nuclear cataract
- B. Cortical cataract
- C. Posterior subcapsular cataract (Correct Answer)
- D. Congenital cataract
Explanation: ***Posterior subcapsular cataract*** - This type of cataract causes significant **glare** and **photophobia**, making it difficult to read in bright light due to opacities located at the **posterior lens capsule**. - The patient experiences worsening vision in **bright light** conditions because the constricted pupil directs more light through the **central posterior opacity**, which lies directly in the visual axis. *Nuclear cataract* - Patients with **nuclear cataracts** typically experience **myopic shift** and improved near vision (second sight) due to increased refractive power of the lens. - Vision is usually worse in **dim light** conditions because of pupillary dilation, which allows more light to pass through the central opacity. *Cortical cataract* - Characterized by **spoke-like opacities** that start in the periphery and extend inward. - While it can cause glare, vision often remains good until the opacities encroach upon the **visual axis**, and it doesn't specifically cause worsening vision in bright light to the same degree as PSC. *Congenital cataract* - Present at birth or shortly after, and symptoms depend on the density and location of the opacity. - While it affects vision, the specific complaint of difficulty reading in bright sunlight is not a typical distinguishing feature of **congenital cataracts**.
Question 5: Most visually handicapping cataract is:
- A. Rosette cataract
- B. Nuclear cataract
- C. Posterior subcapsular cataract (Correct Answer)
- D. Conical cataract
Explanation: ***Posterior subcapsular cataract*** - This type of cataract causes **the most significant visual impairment** due to its location at the posterior pole of the lens, **directly in the visual axis**. - Symptoms include **severe glare** (especially in bright light when pupil constricts) and **marked difficulty with reading** and near vision tasks, often **disproportionate to the cataract's size**. - Causes rapid and debilitating visual symptoms compared to other cataract types. *Rosette cataract* - Typically forms after **ocular trauma** and is characterized by a flower-petal-shaped opacity. - While it can impair vision, its severity depends on size and location, and is usually not as visually debilitating as posterior subcapsular cataract. *Nuclear cataract* - Involves the **central nucleus** of the lens and causes gradual blurring of vision with possible **myopic shift**. - Progresses more slowly, allowing better adaptation compared to the sudden, severe glare and near vision loss of posterior subcapsular cataract. *Conical cataract* - Refers to **lenticonus**, a conical protrusion of the lens capsule, usually associated with **Alport syndrome**. - Relatively rare developmental anomaly, not a common form of acquired cataract, and less functionally debilitating than posterior subcapsular cataract.
Question 6: What is the most likely complication of the condition shown in the image below?
- A. Exposure Keratitis (Correct Answer)
- B. Difficulty in eye movement
- C. Cataract
- D. Glaucoma
Explanation: ***Exposure Keratitis*** - The image shows **proptosis** (exophthalmos) of the right eye, where the eyeball protrudes forward. This condition often leads to incomplete eyelid closure (lagophthalmos). - **Exposure keratitis** occurs when the cornea is inadequately covered by the eyelids, leading to drying and damage due to constant exposure to air and environmental factors. *Difficulty in eye movement* - While **proptosis** can sometimes be associated with restricted eye movements (e.g., in severe Graves' ophthalmopathy due to muscle swelling), it is not the **most likely direct complication** of the exposure itself. - The image primarily depicts the physical displacement of the globe, which predisposes to corneal issues, not necessarily oculomotor dysfunction as the primary complication. *Cataract* - **Cataracts** are opacities of the lens and are typically associated with aging, trauma, or certain systemic conditions (e.g., diabetes, steroid use). - They are not a direct or common complication of **proptosis** or the resulting **exposure of the ocular surface**. *Glaucoma* - **Glaucoma** is a group of conditions characterized by damage to the optic nerve, often due to elevated intraocular pressure. - While severe **proptosis** leading to orbital congestion can theoretically increase intraocular pressure, it is not the most direct or prevalent complication compared to **exposure keratitis**, which is a direct consequence of inadequate globe protection.
Question 7: Which of the following is a true statement regarding the human eye?
- A. Lens will not reflect light
- B. Even after cataract surgery UV rays do not penetrate
- C. Normal eye medium will permit wavelengths of 400-700 nm (Correct Answer)
- D. Cornea cuts off wavelengths up to 400 nm
Explanation: ***Normal eye medium will permit wavelength of 400- 700 nm*** - The **normal human eye** can perceive light in the **visible spectrum**, which ranges approximately from **400 nm (violet)** to **700 nm (red)**. - This range of wavelengths is efficiently transmitted through the ocular media (cornea, aqueous humor, lens, vitreous humor) to reach the retina. *Lens will not reflect light* - The human **lens** does **reflect some light**, contributing to phenomena like **glare** and internal reflections, especially if there are opacities like cataracts. - While its primary function is to transmit and refract light, it is not perfectly non-reflective. *Even after cataract surgery UV rays are not penetrated* - Modern **intraocular lenses (IOLs)** implanted during **cataract surgery** are designed to **block UV light (UVA and UVB)** to protect the retina. - However, the natural lens also blocks UV light, and before the development of UV-blocking IOLs, patients sometimes experienced increased retinal exposure to UV post-surgery. *Cornea cut off wavelength upto 400 nm* - The **cornea** primarily absorbs and blocks **UVB (280-315 nm)** and **UVC (100-280 nm)** radiation, protecting the anterior segment structures and retina from harmful short-wavelength light. - It does **not cut off wavelengths up to 400 nm**; it primarily transmits wavelengths longer than approximately 300-310 nm into the eye.
Question 8: In photophthalmia, which part of the eye is primarily affected?
- A. Lens
- B. Cornea (Correct Answer)
- C. Retina
- D. Optic nerve
Explanation: ***Cornea*** - **Photophthalmia** (also known as **snow blindness** or **arc eye**) is caused by overexposure to **ultraviolet (UV) light**, which primarily damages the **corneal epithelium**. - This damage leads to **superficial punctate keratitis**, characterized by pain, foreign body sensation, photophobia, and blurred vision. - Symptoms typically appear **6-12 hours after exposure** and resolve within **24-48 hours** with supportive care. *Retina* - The **retina** can be damaged by certain types of light (e.g., solar retinopathy from looking at the sun), but **UV light** in photophthalmia is largely absorbed by the anterior structures of the eye, particularly the cornea. - Retinal damage would typically present with **central visual loss** or **scotomas**, differing from the acute pain and photophobia of photophthalmia. *Optic nerve* - The **optic nerve** transmits visual information from the retina to the brain and is generally not directly affected by **UV light exposure** causing photophthalmia. - Optic nerve issues would manifest as severe **vision loss**, **pupillary abnormalities**, or **pain with eye movement**, which are not typical for photophthalmia. *Lens* - While chronic **UV exposure** can contribute to **cataract formation** in the lens over time, this is a long-term effect, not the acute primary damage seen in photophthalmia. - The acute presentation of photophthalmia with severe pain, photophobia, and foreign body sensation is characteristic of **corneal epithelial damage**, not lens involvement.
Question 9: What is the primary cause of snow blindness?
- A. UV rays (Correct Answer)
- B. Infrared radiation
- C. Microwave radiation
- D. Defect in optical devices
Explanation: **UV rays** - **Snow blindness**, clinically known as **photokeratitis**, is primarily caused by exposure of the eyes to high levels of **ultraviolet (UV) radiation**. - This radiation is particularly intense in snow-covered environments due to the **high reflectivity of snow**, which can reflect up to 80% of UV rays, effectively exposing the eyes to double the amount of UV. *Infrared radiation* - While infrared radiation can cause **heat-related injury** to the eyes (e.g., glassblower's cataract), it does not directly lead to the corneal damage characteristic of snow blindness. - Infrared radiation is sensed as heat and is not responsible for the **phototoxic effect** on the cornea. *Microwave radiation* - Microwave radiation can cause internal heating of tissues, but it is not a direct cause of photokeratitis or snow blindness. - Exposure to high levels of microwave radiation can lead to other ocular issues like **cataracts**, but through different mechanisms. *Defect in optical devices* - While defective optical devices (e.g., sunglasses without proper UV protection) can *contribute* to snow blindness by failing to block UV radiation, they are not the primary cause themselves. - The underlying harmful agent is the **UV radiation**, and the defect merely allows the exposure to occur.
Question 10: Which of the following statements regarding thermal injury is correct?
- A. In child below 5 years, genitals form 1% of area
- B. Lund-Browder chart is the most accurate method for estimating TBSA in children (Correct Answer)
- C. Rule of nines is more accurate than Lund-Browder chart in children
- D. Burn index is the standard clinical method for assessing burn severity
Explanation: ***Lund-Browder chart is the most accurate method for estimating TBSA in children*** - The Lund-Browder chart is the **most accurate method** for estimating the **total body surface area (TBSA)** affected by burns, especially in children, due to its ability to adjust for age-related body proportion changes. - It assigns different body proportions based on age, making it superior to the Rule of Nines for pediatric patients. - This is the **CORRECT** statement. *Rule of nines is more accurate than Lund-Browder chart in children* - This is **FALSE**. The Rule of Nines is **less accurate in children** because their head and neck comprise a larger percentage of TBSA and their lower limbs a smaller percentage compared to adults. - The Lund-Browder chart is specifically designed to account for age-related differences and is therefore more accurate in pediatric burn assessment. *In child below 5 years, genitals form 1% of area* - While this statement is **technically true**, it is not the **most correct** answer in the context of thermal injury assessment methods. - In both adults and children, the **genitals and perineum** together typically account for **1% of TBSA**. - This is a specific anatomical fact but doesn't address burn assessment methodology, which is the main focus of the question. *Burn index is the standard clinical method for assessing burn severity* - This is **FALSE**. The **Burn Index** is not a commonly used term in standard clinical burn assessment. - Burn severity is assessed by considering both **depth** (superficial, partial-thickness, full-thickness) and **TBSA percentage**, along with other factors like location and patient age, but "Burn Index" is not the standard terminology or method used.
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