1mm change in axial length of the eyeball would change the refracting power of the eye by?
A 30 year old man presents to the clinic with pain in the eye, watering, redness, and photophobia. Examination of his eyes shows circumcorneal congestion and keratic precipitates. Assertion: Keratic precipitates (KPs) are proteinaceous deposits that can occur in various patterns on the corneal endothelium. Reason: Mutton fat KPs are seen in granulomatous iridocyclitis and are composed of epithelioid cells and macrophages.
What does a lensometer measure?
Which of the following is not a standard treatment for myopia?
All are true regarding cornea except:
Sudden loss of vision without pain - Which of the following is NOT a cause?
Which of the following is NOT a cause of crystal keratopathy?
Kayser-Fleischer ring is found in which layer of cornea?
Kayser-Fleischer rings (KF rings) are seen in:
Astigmatism is defined as?
NEET-PG 2015 - Ophthalmology NEET-PG Practice Questions and MCQs
Question 11: 1mm change in axial length of the eyeball would change the refracting power of the eye by?
- A. 1D
- B. 2D
- C. 3D (Correct Answer)
- D. 4D
Explanation: ***3D*** - A 1mm change in the **axial length** of the eyeball leads to an approximate **3 diopter (D) change** in the refractive power of the eye. - This relationship is crucial for understanding **refractive errors** like myopia (if the eyeball is too long) or hyperopia (if it's too short). *1D* - A 1D change in refractive power corresponds to a much larger change in the **focal length** of the eye, not typically 1mm in axial length. - This value is too small to reflect the significant impact of a 1mm axial length alteration on the eye's focusing ability. *2D* - While a direct relationship exists, 2D is an **underestimation** of the actual refractive change caused by a 1mm alteration in axial length. - This value would imply a less sensitive optical system than the human eye. *4D* - A 4D change would represent an **overestimation** of the refractive power change for a 1mm alteration in axial length. - Such a high value is generally seen with more substantial anatomical variations or surgical interventions.
Question 12: A 30 year old man presents to the clinic with pain in the eye, watering, redness, and photophobia. Examination of his eyes shows circumcorneal congestion and keratic precipitates. Assertion: Keratic precipitates (KPs) are proteinaceous deposits that can occur in various patterns on the corneal endothelium. Reason: Mutton fat KPs are seen in granulomatous iridocyclitis and are composed of epithelioid cells and macrophages.
- A. Both Assertion and Reason are true, and Reason is the correct explanation for Assertion
- B. Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion (Correct Answer)
- C. Assertion is true, but Reason is false
- D. Assertion is false but reason is true
Explanation: ***Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion*** **Why both statements are true:** - The **Assertion** is correct: Keratic precipitates (KPs) are inflammatory cell and protein deposits that adhere to the **corneal endothelium** and can present in various patterns including fine dusty KPs, medium-sized KPs, and large mutton fat KPs. - The **Reason** is also correct: **Mutton fat KPs** are characteristic of **granulomatous anterior uveitis** (granulomatous iridocyclitis) and consist of aggregations of **epithelioid cells and macrophages**, appearing as large, greasy, white deposits. **Why Reason does NOT explain Assertion:** - The Reason describes a **specific type** of KP (mutton fat) and its cellular composition in one particular form of inflammation (granulomatous). - The Assertion makes a **general statement** about KPs occurring in various patterns. - The Reason does not explain **why** KPs can occur in various patterns or what determines these different patterns - it only describes one specific pattern. *Incorrect: Both true with Reason explaining Assertion* - The Reason is too specific and only describes one type of KP, not the general mechanism of pattern variation. *Incorrect: Assertion true, Reason false* - Both statements are medically accurate and well-established in ophthalmology literature. *Incorrect: Assertion false, Reason true* - KPs are well-documented deposits on the corneal endothelium in various forms of uveitis, making the Assertion true.
Question 13: What does a lensometer measure?
- A. Corneal topography
- B. Biochemical constitution of lens
- C. Power of IOL
- D. The refractive power of corrective lenses (Correct Answer)
Explanation: ***The refractive power of corrective lenses*** - A **lensometer**, also known as a focimeter or vertometer, is an ophthalmological instrument used to measure the **refractive power** of spectacle lenses, contact lenses, and intraocular lenses. - It determines parameters such as **sphere**, **cylinder**, and **axis**, providing essential information for dispensing and fabricating corrective eyewear. *Corneal topography* - **Corneal topography** maps the curvature and shape of the cornea and is performed by a **topographer**. - This instrument is primarily used to diagnose and monitor conditions like **keratoconus** and to plan refractive surgeries. *Biochemical constitution of lens* - The **biochemical constitution** of the lens refers to its molecular makeup, including proteins and metabolites. - This is typically assessed through laboratory techniques like **spectroscopy** or **chromatography**, not a lensometer. *Power of IOL* - While a lensometer can measure the power of an **intraocular lens (IOL)** once it is manufactured, the initial power calculation for an IOL before implantation is determined using **biometry** (e.g., A-scan ultrasound or optical biometry). - **Biometry** measures the axial length of the eye and corneal curvature to calculate the appropriate IOL power.
Question 14: Which of the following is not a standard treatment for myopia?
- A. Phakic intraocular lens
- B. Radial Keratotomy
- C. Holmium laser thermoplasty (Correct Answer)
- D. LASIK
Explanation: ***Holmium laser thermoplasty*** - This procedure was explored for the treatment of **hyperopia**, not myopia, as it aims to steepen the cornea to increase its refractive power. - It involves using a holmium laser to apply heat to the peripheral cornea, causing **collagen shrinkage** and steepening, which is the opposite of what is needed for myopia correction. *LASIK* - **LASIK (Laser-Assisted in Situ Keratomileusis)** is a common and effective surgical procedure for correcting myopia by reshaping the cornea to reduce its refractive power. - It involves creating a **corneal flap** and using an excimer laser to remove tissue from the underlying stromal bed. *Phakic intraocular lens* - **Phakic intraocular lenses (IOLs)** are implanted into the eye without removing the natural lens and are a standard treatment for moderate to high myopia, especially in patients not suitable for LASIK. - They work by adding refractive power to the eye, allowing light to focus correctly on the retina. *Radial Keratotomy* - **Radial Keratotomy (RK)** was an early surgical procedure for myopia, involving making radial incisions in the cornea to flatten it and reduce its refractive power. - Although largely replaced by LASIK due to its unpredictable outcomes and potential for glare and night vision problems, it was historically a standard treatment for myopia.
Question 15: All are true regarding cornea except:
- A. The cornea is richly vascular. (Correct Answer)
- B. Endothelium help in maintaining dehydrated state
- C. Oxygen is mostly derived by epithelium directly from the air through tear film
- D. Corneal thickness is greater at periphery than center
Explanation: ***The cornea is richly vascular.*** - The cornea is an **avascular** tissue, meaning it lacks blood vessels, which is crucial for its transparency. - This avascularity helps prevent light scatter and maintains clear vision. - The cornea receives nutrition from the **aqueous humor**, **tear film**, and **limbal blood vessels** through diffusion. *Endothelium help in maintaining dehydrated state* - The **corneal endothelium** actively pumps fluid out of the corneal stroma via **Na-K-ATPase pumps**, preventing swelling and maintaining its relative state of dehydration. - This **deturgescence** is essential for the cornea's transparency and optimal refractive power. *Oxygen is mostly derived by epithelium directly from the air through tear film* - The corneal **epithelium** primarily obtains oxygen directly from the atmosphere via the **tear film** when the eyes are open. - During sleep, oxygen is primarily supplied by the **palpebral conjunctival vessels**. *Corneal thickness is greater at periphery than center* - The cornea is **thinner at the center** (around 520-540 µm) and gradually **thicker towards the periphery** (around 600-640 µm). - This structural difference contributes to its optical properties and mechanical stability.
Question 16: Sudden loss of vision without pain - Which of the following is NOT a cause?
- A. CRAO
- B. CSR
- C. Acute congestive glaucoma (Correct Answer)
- D. Vitreous Hemorrhage
Explanation: ***Acute congestive glaucoma*** - This condition is characterized by **sudden, severe eye pain** along with blurred vision, redness, and a fixed, mid-dilated pupil. - The pain arises from abrupt elevation of **intraocular pressure**, which differentiates it from painless vision loss. *CRAO* - **Central Retinal Artery Occlusion** (CRAO) typically presents as **sudden, profound, painless monocular vision loss**. - Funduscopic examination often reveals a **cherry-red spot** in the fovea with generalized retinal whitening. *CSR* - **Central Serous Retinopathy** (CSR) causes **sudden, painless blurred vision** or a scotoma, often described as a "watery" or "shimmering" effect. - It involves leakage of fluid under the retina, typically in the macula. *Vitreous Hemorrhage* - Presents as **sudden, painless loss of vision** or a shower of floaters, often described as cobwebs or clouds. - It results from bleeding into the **vitreous cavity**, which can obscure the retina.
Question 17: Which of the following is NOT a cause of crystal keratopathy?
- A. Schnyder's Dystrophy
- B. Bietti's Dystrophy
- C. Diabetes (Correct Answer)
- D. Cystinosis
Explanation: ***Diabetes*** - While diabetes can cause various ocular complications, such as **diabetic retinopathy**, **neovascular glaucoma**, and **cataracts**, it is **not associated** with crystal keratopathy. - Corneal changes in diabetes might include epithelial defects or reduced corneal sensitivity, but **not the deposition of crystalline substances in the cornea**. - **This is the correct answer** as diabetes does NOT cause crystal keratopathy. *Cystinosis* - **Cystinosis** is a metabolic disorder characterized by the accumulation of **cystine crystals** throughout the body, including the **cornea**. - These crystals can lead to significant **photophobia**, **corneal erosions**, and visual impairment, making it a **classic cause of crystal keratopathy**. - Corneal involvement typically appears in childhood with diffuse crystalline deposits. *Schnyder's Dystrophy* - **Schnyder's corneal dystrophy** is an inherited corneal dystrophy characterized by the deposition of **cholesterol and lipid crystals** in the central and peripheral cornea. - This leads to **dense corneal opacification** and can significantly impair vision over time, representing a **classic cause of crystal keratopathy**. - The cornea shows characteristic subepithelial and stromal crystal deposits. *Bietti's Crystalline Dystrophy* - **Bietti's crystalline dystrophy** is a rare, inherited chorioretinal dystrophy characterized by **crystalline deposits primarily in the retina and choroid**. - While the name suggests crystalline involvement, these crystals are predominantly **intraretinal and do NOT typically cause corneal crystal deposits**. - Therefore, Bietti's is **NOT a typical cause of crystal keratopathy** (corneal disease), though minimal peripheral corneal crystals have been rarely reported in advanced cases. - The confusion arises from the word "crystalline" in its name, but the pathology is retinal, not corneal.
Question 18: Kayser-Fleischer ring is found in which layer of cornea?
- A. Endothelium
- B. Descemet's membrane (Correct Answer)
- C. Bowman's layer
- D. Corneal stroma
Explanation: ***Descemet's membrane*** - Kayser-Fleischer rings are caused by **copper deposition** at the periphery of the cornea, specifically within **Descemet's membrane**. - This membrane is located between the **corneal stroma** and the **endothelium**. *Bowman's layer* - Bowman's layer is a thin, acellular layer of the cornea that lies beneath the **corneal epithelium**. - While it plays a role in corneal integrity, it is not the site of **copper deposition** in Wilson's disease. *Corneal stroma* - The corneal stroma is the thickest layer of the cornea, composed primarily of **collagen fibrils**. - Although it contains most of the corneal mass, **copper deposition** in Kayser-Fleischer rings does not specifically occur within the main stromal layer. *Endothelium* - The corneal endothelium is the innermost layer of the cornea, responsible for maintaining **corneal deturgescence**. - While it is adjacent to Descemet's membrane, the copper rings are deposited in the membrane itself, not directly in the endothelial cell layer.
Question 19: Kayser-Fleischer rings (KF rings) are seen in:
- A. Pterygium
- B. Hemochromatosis
- C. Wilson's disease (Correct Answer)
- D. Menke's kinked hair syndrome
Explanation: ***Wilson's disease*** - **Kayser-Fleischer (KF) rings** are pathognomonic for **Wilson's disease**, resulting from **copper deposition** in the Descemet's membrane of the cornea. - This genetic disorder leads to excessive **copper accumulation** in the liver, brain, and other tissues due to impaired copper excretion. *Pterygium* - A **pterygium** is a benign growth of the **conjunctiva** that extends onto the cornea, typically appearing as a fleshy, triangular lesion. - It is not associated with systemic copper metabolism disorders or the presence of KF rings. *Hemochromatosis* - **Hemochromatosis** is a disorder of **iron overload**, leading to iron deposition in various organs, including the liver, heart, and pancreas. - It does not involve copper metabolism or the formation of corneal rings. *Menke's kinked hair syndrome* - **Menke's syndrome** is a genetic disorder characterized by **copper deficiency**, leading to impaired copper transport and utilization. - It presents with severe neurological deterioration, connective tissue abnormalities, and characteristic **kinky hair**, but not KF rings.
Question 20: Astigmatism is defined as?
- A. Refractive error due to long AP length of eyeball
- B. Varying refractive error in both eyes
- C. Varying shape perception by both eyes
- D. Refractive error wherein refraction varies along different meridians (Correct Answer)
Explanation: ***Refractive error wherein refraction varies along different meridians*** - **Astigmatism** is a type of **refractive error** where the eye’s cornea or lens has a different curvature in different directions (meridians). - This irregular curvature causes light rays to focus at multiple points on or in front of the retina, leading to **blurred or distorted vision**. *Refractive error due to long AP length of eyeball* - A long axial length of the eyeball is characteristic of **myopia** (nearsightedness), where light focuses in front of the retina. - This definition does not describe **astigmatism**, which is primarily about irregular curvature rather than overall length. *Varying refractive error in both eyes* - This describes **anisometropia**, a condition where the two eyes have significantly different refractive powers. - While anisometropia can coexist with astigmatism, it is not the definition of **astigmatism** itself. *Varying shape perception by both eyes* - This could imply conditions like **aniseikonia**, where the perceived size and shape of images differ between the two eyes. - It does not directly define **astigmatism**, which is a primary refractive error related to the focusing of light.