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: Which of the following statements about Fuchs' corneal dystrophy is incorrect?

A. Endothelial dystrophy
B. Occurs in old age
C. Unilateral condition (Correct Answer)
D. Posterior dystrophy

Explanation: ***Unilateral condition - INCORRECT STATEMENT*** - **Fuchs' corneal dystrophy** is typically a **bilateral condition**, although it can be asymmetric in its presentation. - The disease often affects both eyes, progressing from early morning blurriness to constant visual impairment. - This is the INCORRECT statement - Fuchs' is NOT unilateral. *Posterior dystrophy - Correct statement* - **Fuchs' corneal dystrophy** is classified as a posterior corneal dystrophy, meaning it primarily affects the **corneal endothelium** and Descemet's membrane. - This posterior involvement leads to the characteristic guttata and corneal edema. *Endothelial dystrophy - Correct statement* - It is fundamentally an **endothelial dystrophy**, resulting from primary dysfunction and loss of corneal endothelial cells. - The compromised endothelial pump function leads to **stromal edema** and reduced visual acuity. *Occurs in old age - Correct statement* - Fuchs' corneal dystrophy typically presents in **middle to old age**, with symptoms often becoming noticeable in individuals over 50. - While congenital forms of corneal dystrophy exist, Fuchs' is not usually one of them.

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: Corneal endothelial cell count is measured by?

A. Specular microscope (Correct Answer)
B. Ophthalmoscope
C. Synoptophore
D. Amsler's grid

Explanation: ***Specular microscope*** - A **specular microscope** is specifically designed to provide a high-magnification, non-contact view of the **corneal endothelium**, allowing for direct visualization and counting of endothelial cells. - It measures cell density, morphology, and polymegethism, which are crucial for assessing corneal health, especially before and after intraocular surgeries. *Ophthalmoscope* - An **ophthalmoscope** is used to examine the **fundus** or the back of the eye, including the retina, optic disc, macula, and blood vessels. - It does not have the magnification capabilities required to visualize or count individual corneal endothelial cells. *Synoptophore* - A **synoptophore** is an instrument used to diagnose and treat **strabismus** (eye misalignment) and to assess **binocular vision**. - Its function involves showing different images to each eye to test fusion, suppression, and stereopsis, unrelated to corneal cell count. *Amsler's grid* - **Amsler's grid** is a diagnostic tool used to detect **macular degeneration** and other retinal diseases that affect central vision. - It consists of a grid of straight lines and helps identify distortion or missing areas in the patient's central visual field.

Question 406: Satellite nodules are typically associated with which of the following conditions?

A. Tuberculosis
B. Sarcoidosis
C. Viral ulcer
D. Fungal corneal ulcer (Correct Answer)

Explanation: ***Fungal corneal ulcer*** - **Satellite lesions** (small, isolated infiltrates surrounding a larger central ulcer) are a characteristic feature of **fungal keratitis**, indicating the spread of fungal hyphae. - Unlike bacterial ulcers, fungal ulcers often have a feathery, indistinct margin and can be slow-growing. *Tuberculosis* - Ocular tuberculosis can present with granulomatous inflammation, often involving the uvea or retina, but **satellite nodules** around a corneal ulcer are not typical. - Corneal involvement in tuberculosis is rare and usually manifests as interstitial keratitis or phlyctenular keratitis. *Sarcoidosis* - Ocular sarcoidosis commonly causes **uveitis**, conjunctival nodules, or retinal vasculitis. - While it can cause corneal deposits or band keratopathy, it does not typically present with satellite lesions around a primary corneal ulcer. *Viral ulcer* - Viral corneal ulcers, particularly those caused by **herpes simplex virus**, often present as **dendritic ulcers** or geographic ulcers. - Although epithelial lesions can spread, the distinct **satellite infiltrates** in the stroma seen in fungal infections are not characteristic of viral keratitis.

Question 407: 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 408: 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 409: 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 410: 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.

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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