Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 401: Ameboid ulcers are primarily associated with which type of corneal ulcer?

A. Fungal corneal ulcer
B. Acanthamoeba corneal ulcer (Correct Answer)
C. Bacterial corneal ulcer
D. Herpetic corneal ulcer

Explanation: ***Acanthamoeba corneal ulcer*** - **Acanthamoeba** infections are classically associated with **ameboid ulcers** due to the movement and destructive nature of this protozoan. - This type of ulcer often presents with severe pain, disproportionate to clinical findings, and can have a **ring infiltrates** appearance. *Fungal corneal ulcer* - Fungal ulcers typically present with a **feathery border** and satellite lesions, not ameboid shapes. - They are often associated with a history of **ocular trauma** involving plant material. *Herpetic corneal ulcer* - Herpetic ulcers are characterized by a **dendritic pattern** (tree-branch-like), which is distinct from an ameboid shape. - They are caused by the **herpes simplex virus** and can lead to recurrent episodes. *Bacterial corneal ulcer* - Bacterial ulcers typically present as a **round or oval infiltrate** with stromal edema and an overlying epithelial defect. - They can progress rapidly and are not described as having an **ameboid configuration**.

Question 402: 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 403: Which structures are most commonly involved in a ciliary staphyloma?

A. Choroid and sclera
B. Cornea and conjunctiva
C. Iris and sclera
D. Ciliary body and sclera (Correct Answer)

Explanation: ***Ciliary body and sclera*** - A **staphyloma** is a localized bulging of the outer coat of the eye (sclera or cornea) lined internally by uveal tissue. - A **ciliary staphyloma** specifically involves the **ciliary body** and **sclera** at the region of the ciliary body, typically presenting as a dark bluish bulge at the limbal or perilimbal area. - This occurs due to weakening and ectasia of the sclera with prolapse of the underlying ciliary body, commonly seen following scleritis, perforating injuries, or surgeries. *Choroid and sclera* - This combination describes a **posterior staphyloma**, which occurs at the posterior pole of the eye, commonly seen in pathological myopia. - While medically accurate for posterior type, it does not describe a **ciliary staphyloma**. *Iris and sclera* - An **anterior staphyloma** primarily involves bulging of the **cornea** with incarceration of iris tissue, rather than sclera alone. - It occurs after corneal perforation with iris prolapse. *Cornea and conjunctiva* - This does not describe a staphyloma. Bulging of the cornea alone is termed **keratectasia** or **keratoconus**. - The **conjunctiva** is a superficial membrane and is not a structural component of staphyloma formation.

Question 404: Corneal tattooing is done by ?

A. Titanium chloride
B. Aluminium chloride
C. India ink (Correct Answer)
D. Gold chloride

Explanation: ***India ink*** - **India ink (carbon black)** is the traditional and most commonly used pigment for corneal tattooing due to its stable black color and inert properties. - It is applied to the **corneal stroma** to mask corneal opacities or for cosmetic purposes in cases of unsightly leucomatous corneal scars. - India ink has been the **gold standard** for corneal tattooing since the 19th century. *Gold chloride* - While **gold preparations** (including platinum-gold) have been used historically for corneal tattooing, they are much less common than India ink. - Gold chloride specifically is not the standard or preferred agent for this procedure. - India ink remains the pigment of choice due to better cosmetic results and established safety profile. *Titanium chloride* - **Titanium chloride** is a corrosive chemical and is not used in corneal tattooing; its application would cause severe damage to the delicate corneal tissue. - It is primarily used in industrial applications and chemical synthesis, not in ophthalmic procedures. *Aluminium chloride* - **Aluminium chloride** is an astringent and antiseptic, often used in dermatological products, but it is not a tattooing pigment for the cornea. - Its chemical properties would be highly irritating to the eye and potentially damaging to corneal cells.

Question 405: Herpetic keratitis is treated by which of the following?

A. Analgesics
B. Atropine
C. Steroids
D. Acyclovir (Correct Answer)

Explanation: ***Acyclovir*** - **Acyclovir** is an **antiviral agent** that specifically targets the **herpes simplex virus**, which is the causative agent of herpetic keratitis. - It works by inhibiting viral DNA replication, thereby reducing viral load and preventing further damage to the cornea. *Analgesics* - **Analgesics** are used to manage pain but do not address the **viral etiology** of herpetic keratitis. - While they can improve patient comfort, they are not a definitive treatment for the underlying infection. *Atropine* - **Atropine** is a **cycloplegic agent** used to paralyze the ciliary muscle and dilate the pupil, often to reduce pain from ciliary spasms in uveitis. - It does not have **antiviral properties** and is not effective against the herpes virus. *Steroids* - **Corticosteroids** can suppress inflammation but are generally **contraindicated** in active herpetic keratitis, especially in the epithelial form. - They can worsen the viral infection by compromising the immune response, potentially leading to **corneal ulceration** and perforation.

Question 406: Which of the following statements about corneal dystrophy is true?

A. It involves neovascularization.
B. It is caused by inflammation.
C. It is usually unilateral.
D. It is typically bilateral. (Correct Answer)

Explanation: ***It is typically bilateral.*** - **Corneal dystrophies** are inherited genetic disorders that usually affect both eyes symmetrically. - This bilateral presentation is a key characteristic distinguishing them from other corneal conditions. *It is caused by inflammation.* - **Corneal dystrophies** are primarily genetic and degenerative, not inflammatory. - While inflammation can cause corneal damage (e.g., keratitis), it is not the underlying cause of dystrophy. *It involves neovascularization.* - **Neovascularization** (growth of new blood vessels) is typically a response to chronic inflammation, hypoxia, or infection in the cornea. - It is generally not a feature of primary corneal dystrophies, which are characterized by abnormal deposits or structural changes within the corneal layers. *It is usually unilateral.* - As inherited genetic conditions, **corneal dystrophies** almost always affect both eyes. - Unilateral involvement would suggest a different etiology, such as trauma, infection, or a localized acquired condition.

Question 407: Which virus is most commonly associated with disciform keratitis?

A. Rubella Virus
B. Herpes Simplex Virus (HSV) (Correct Answer)
C. Human Immunodeficiency Virus (HIV)
D. Hepatitis B Virus (HBV)

Explanation: ***Herpes Simplex Virus (HSV)*** - **HSV** is the most common cause of **infectious disciform keratitis**, often following a primary ocular HSV infection or reactivation. - Disciform keratitis caused by HSV is a form of **immune-mediated stromal keratitis**, characterized by corneal edema, inflammation, and potential vision loss. *Rubella Virus* - While Rubella can cause ocular manifestations, such as **congenital cataracts** and **glaucoma** in infants, it is not typically associated with disciform keratitis in adults or children. - **Congenital rubella syndrome** is the primary context for ophthalmic issues related to this virus. *Human Immunodeficiency Virus (HIV)* - HIV can lead to various ocular complications, such as **CMV retinitis**, **Kaposi's sarcoma** of the conjunctiva, and **HIV retinopathy**. - However, HIV itself is **not directly linked** to disciform keratitis. *Hepatitis B Virus (HBV)* - HBV infection primarily affects the **liver** and is not commonly associated with direct ocular infections like keratitis. - Ocular manifestations are rare and often nonspecific, mainly related to systemic immune responses rather than direct viral replication in the eye.

Question 408: Which of the following is a known complication of vernal keratoconjunctivitis?

A. Keratoconus (Correct Answer)
B. Retinal detachment
C. Vitreous hemorrhage
D. Cataract

Explanation: ***Keratoconus*** - **Vernal keratoconjunctivitis (VKC)** is a chronic allergic eye condition associated with persistent eye rubbing, which can lead to thinning and bulging of the cornea, a condition known as **keratoconus**. - Long-term inflammation and mechanical stress from allergic reactions and *eye rubbing* contribute to the corneal structural changes seen in keratoconus. - This is the **most common and well-recognized complication** of VKC. *Cataract* - While cataracts can occur in VKC patients (particularly from **chronic topical steroid use** or severe disease with shield ulcers), they are **less common than keratoconus** as a direct complication. - Keratoconus remains the more characteristic and frequently encountered complication specifically associated with the mechanical trauma of eye rubbing in VKC. *Retinal detachment* - **Retinal detachment** is a condition where the retina separates from its underlying support tissues and is typically associated with trauma, high myopia, or diabetic retinopathy, not VKC. - VKC primarily affects the conjunctiva and cornea, and its inflammatory processes do not directly cause retinal detachment. *Vitreous hemorrhage* - **Vitreous hemorrhage** involves bleeding into the gel-like substance that fills the eye and is commonly caused by conditions like diabetic retinopathy or retinal tears, not VKC. - VKC does not involve the posterior segment of the eye in a way that would lead to vitreous hemorrhage.

Question 409: Among the following organisms, which is the most common cause of postoperative endophthalmitis following corneal transplantation?

A. Streptococcus
B. Pseudomonas
C. Propionibacterium acnes
D. Staph epidermidis (Correct Answer)

Explanation: ***Staph epidermidis*** - **Coagulase-negative Staphylococcus** (CoNS), including *S. epidermidis*, is the most frequent cause of **postoperative endophthalmitis** after both cataract surgery and corneal transplantation due to its presence on the normal ocular flora. - These organisms can form **biofilms on intraocular lenses** or transplanted corneal tissue, making eradication difficult. *Streptococcus* - While *Streptococcus* species can cause endophthalmitis, they are associated with a **more virulent and rapid onset** of severe inflammation and are not the most common causative agents of postoperative endophthalmitis compared to *S. epidermidis*. - They tend to cause more aggressive infections with often **poorer visual outcomes**. *Propionibacterium acnes* - *Propionibacterium acnes* can cause a **late-onset, indolent form of endophthalmitis**, typically months or even years after surgery. - While it is a recognized cause, it is far **less common** than *Staphylococcus epidermidis* in immediate or early postoperative cases. *Pseudomonas* - **Pseudomonas aeruginosa** is an aggressive and rapid-onset pathogen often associated with **severe keratitis** or **post-traumatic endophthalmitis**. - Although it can cause postoperative endophthalmitis, it is **much less common** than coagulase-negative staphylococci due to its infrequency on normal conjunctival flora.

Question 410: What is the most common protozoan associated with keratitis?

A. Plasmodium
B. Acanthamoeba (Correct Answer)
C. Toxoplasma
D. Entamoeba histolytica

Explanation: ***Acanthamoeba*** - **Acanthamoeba keratitis** is a serious and painful infection of the eye's cornea, most commonly associated with **contact lens wearers** who do not properly disinfect their lenses. - The organism is a **free-living protozoan** found in soil and water. *Plasmodium* - **Plasmodium** species are the causative agents of **malaria**, a disease that primarily affects **red blood cells** and the liver. - While it can manifest with ocular symptoms like **retinopathy**, it does not typically cause **keratitis**. *Toxoplasma* - **Toxoplasma gondii** causes **toxoplasmosis**, an infection that can lead to **chorioretinitis** (inflammation of the retina and choroid), especially in immunocompromised individuals or congenitally infected infants. - It does not directly cause **keratitis** as its primary ocular manifestation. *Entamoeba histolytica* - **Entamoeba histolytica** is the protozoan responsible for **amebiasis**, particularly **amoebic dysentery** and **liver abscesses**. - Ocular involvement with *Entamoeba histolytica* is extremely rare and typically involves **metastatic lesions** to the orbit or eyelids, not directly primary keratitis.

Practice by Chapter

Corneal Anatomy and Physiology

Practice Questions

Bacterial Keratitis

Practice Questions

Viral Keratitis

Practice Questions

Fungal Keratitis

Practice Questions

Protozoan Keratitis

Practice Questions

Corneal Degenerations

Practice Questions

Corneal Dystrophies

Practice Questions

Keratoconus and Ectatic Disorders

Practice Questions

Corneal Transplantation

Practice Questions

Corneal Topography and Imaging

Practice Questions

Dry Eye Disease

Practice Questions

Corneal Trauma

Practice Questions

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