Ophthalmology
9 questionsWhich of the following methods is not used to measure refractive error?
Aniseikonia is ?
Which is the most powerful refractive surface of the eye?
Strabismic amblyopia is more common in patients with:
Astigmatism is defined as?
What is regular astigmatism?
What term describes a condition where the axial length of the eye does not match its refractive power?
In a case of myopia, LASIK can correct up to how many diopters?
Which of the following statements about pterygium is false?
NEET-PG 2015 - Ophthalmology NEET-PG Practice Questions and MCQs
Question 831: Which of the following methods is not used to measure refractive error?
- A. Keratometry
- B. Retinoscopy
- C. Refractometry
- D. Spectrometry (Correct Answer)
Explanation: ***Spectrometry*** - **Spectrometry** measures the absorption or emission of light by a substance at different wavelengths, primarily used for chemical analysis and material science. - It does not directly assess the **focal power** of the eye or its refractive state. *Keratometry* - **Keratometry** measures the curvature of the anterior surface of the cornea, which is essential for determining astigmatism and fitting contact lenses. - While it doesn't measure the entire refractive error, it provides crucial data used in **refractive error assessment**. *Retinoscopy* - **Retinoscopy** is an objective method for determining the eye's refractive error by observing the movement of reflected light in the patient's pupil as a light source is swept across the eye. - It helps determine the approximate sphere and cylinder power needed for proper vision correction, especially useful in **uncooperative patients** or children. *Refractometry* - **Refractometry** (often performed with an autorefractor) is an automated method that uses light reflections from the retina to estimate the eye's refractive error. - It provides an objective measurement of the **spherical, cylindrical, and axial components** of refractive error, serving as a starting point for subjective refraction.
Question 832: Aniseikonia is ?
- A. Projection of different colored images into the visual cortex of one eye
- B. Change in the perception of object size due to distance
- C. Temporary visual disturbances affecting one eye
- D. Projection of different sized images into visual cortex of two retinae (Correct Answer)
Explanation: ***Projection of different sized images into visual cortex of two retinae*** - **Aniseikonia** is a condition where the **magnification of images** projected onto the retinas of each eye differs, leading to a difference in perceived image size. - This difference can cause diplopia, spatial distortion, and other visual discomforts, often due to **refractive error differences** between the eyes. *Projection of different colored images into the visual cortex of one eye* - This describes a form of **dyschromatopsia** or color vision deficiency, specifically if restricted to one eye, but it is not aniseikonia. - Aniseikonia concerns the **size** of an image, not its color. *Change in the perception of object size due to distance* - This is a normal phenomenon related to **perspective** and the brain's interpretation of visual cues, not a pathological condition like aniseikonia. - Aniseikonia involves an actual difference in retinal image size, independent of observer-object distance. *Temporary visual disturbances affecting one eye* - This description is too general and could refer to various conditions such as a **migraine aura** or a transient monocular vision loss (**amaurosis fugax**). - Aniseikonia is a persistent discrepancy in image size between the eyes, not necessarily temporary and not limited to affecting only one eye's function in isolation.
Question 833: Which is the most powerful refractive surface of the eye?
- A. Conjunctiva
- B. Cornea (Correct Answer)
- C. Vitreous
- D. Lens
Explanation: ***Cornea*** - The **cornea** is the eye's outermost, transparent layer, responsible for approximately **two-thirds of the total refractive power** of the eye due to its highly curved anterior surface and the significant change in refractive index from air to corneal tissue. - Its fixed curvature and consistent refractive index make it the primary and most powerful component in bending light rays to focus them on the retina. *Conjunctiva* - The **conjunctiva** is a thin, translucent mucous membrane that lines the inner surface of the eyelids and covers the anterior sclera (white part of the eye). - Its primary function is protection and lubrication, producing mucus and tears, but it plays **no significant role in light refraction**. *Vitreous* - The **vitreous humor** is a transparent, gel-like substance that fills the space between the lens and the retina, maintaining the eye's shape. - It has a refractive index very similar to water (approximately 1.334) and contributes **minimally to the eye's total refractive power** because light has already been significantly refracted by the cornea and lens before reaching it. *Lens* - The **lens** is a transparent, biconvex structure located behind the iris, providing the remaining **one-third of the eye's refractive power**. - While crucial for **accommodation** (changing focal length to see objects at different distances), its refractive power is less than the cornea's, and its ability to change shape is what makes it unique, not its absolute power.
Question 834: Strabismic amblyopia is more common in patients with:
- A. Constant strabismus (Correct Answer)
- B. Alternating strabismus
- C. Latent strabismus
- D. Intermittent strabismus
Explanation: **Constant Strabismus** - In **constant strabismus**, one eye is always deviated, leading to **continuous suppression** of the image from the deviated eye by the brain. - This consistent suppression prevents proper visual development in the deviated eye, resulting in **amblyopia**. *Alternating strabismus* - In **alternating strabismus**, the deviation switches between the two eyes, allowing each eye to take turns fixing. - This alternation helps maintain relatively good visual acuity in both eyes, making **amblyopia less common** or severe. *Latent strabismus* - **Latent strabismus** (phoria) is a deviation that is only present when binocular fusion is disrupted (e.g., when one eye is covered). - Since fusion is typically maintained in daily vision, there is **no constant suppression** of one eye, and amblyopia is rare. *Intermittent strabismus* - **Intermittent strabismus** involves periods of deviation alternating with periods of straight eye alignment, often varying with fatigue or visual tasks. - While it can lead to amblyopia, it is **less common and severe** than with constant strabismus because there are periods when the visual input from both eyes is utilized.
Question 835: 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.
Question 836: What is regular astigmatism?
- A. Astigmatism in which the principal meridians are parallel
- B. Asymptomatic astigmatism
- C. Astigmatism as a result of cataract surgery
- D. Astigmatism where the principal meridians are at a 90-degree angle to each other (Correct Answer)
Explanation: ***Astigmatism where the principal meridians are at a 90-degree angle to each other.*** - In **regular astigmatism**, the two principal meridians of the eye's refractive power are **perpendicular** (90 degrees apart), meaning they are not random. - This perpendicularity allows for correction with **sphero-cylindrical lenses**, as the different focal powers are along well-defined axes. *Astigmatism in which the principal meridians are parallel* - This statement is incorrect as it describes a non-existent or mischaracterized form of astigmatism; for astigmatism to occur, there must be a **difference in curvature** and thus power between two meridians, which cannot be parallel and distinct. - While meridians are typically measured, the concept of **parallel principal meridians** does not align with the definition of astigmatism. *Asymptomatic astigmatism* - This describes the **presence of astigmatism without noticeable symptoms**, not the type of astigmatism itself. - Astigmatism can be asymptomatic, particularly if it is of a **low magnitude**, but this term does not define its optical characteristics. *Astigmatism as a result of cataract surgery* - This refers to **induced astigmatism**, often post-surgical, which can be regular or irregular. - **Surgically induced astigmatism** is a cause, not a classification of astigmatism based on the orientation of its principal meridians.
Question 837: What term describes a condition where the axial length of the eye does not match its refractive power?
- A. Anisokonia
- B. Axial Ametropia (Correct Answer)
- C. Emmetropia
- D. Curvature ametropia
Explanation: ***Axial Ametropia*** - This term precisely describes a refractive error where the **axial length** of the eye is either too long or too short relative to its **optical power**, leading to images focusing in front of or behind the retina. - Examples include **myopia** (eye too long) and **hyperopia** (eye too short), which are fundamentally caused by a mismatch in axial length. *Anisokonia* - This condition refers to a significant difference in the **perceived size of images** between the two eyes, often due to unequal refractive errors between the eyes. - It does not directly describe the mismatch between axial length and refractive power itself, but rather a perceptual consequence that can result from asymmetric refractive errors. *Curvature ametropia* - This type of ametropia occurs when the **curvature** of the cornea or lens is abnormal, causing light rays to converge incorrectly. - While it's a form of refractive error, it specifically relates to the curvature of refractive surfaces, not the overall **axial length** of the eyeball. *Emmetropia* - This is the state of having **perfect vision**, where the refractive power of the eye correctly matches its axial length, allowing light to focus precisely on the retina without accommodation. - It describes the absence of refractive error, which is the opposite of the condition described in the question.
Question 838: In a case of myopia, LASIK can correct up to how many diopters?
- A. -4D
- B. -12D (Correct Answer)
- C. -20D
- D. -6D
Explanation: ***-12D*** - LASIK can effectively correct myopia up to approximately **-12 diopters** in suitable candidates, though this can vary slightly based on individual corneal thickness and health. - The excimer laser reshapes the **cornea** to reduce its curvature, thereby decreasing the focusing power of the eye and correcting the myopic error. *-20D* - While some highly myopic individuals might desire such a correction, LASIK is generally not recommended or effective for myopia higher than **-12 to -14 diopters** due to limitations in corneal tissue removal and potential for complications. - Correcting very high myopia with LASIK would require removing too much corneal tissue, potentially leading to **corneal instability** or vision-threatening complications like **ectasia**. *-6D* - This is a common and highly successful range for LASIK correction, but it represents only a **moderate level of myopia** and not the maximum correctable range. - Patients with myopia of -6D typically achieve excellent visual outcomes with very low complication rates after LASIK. *-4D* - This is a relatively low level of myopia, and LASIK is very effective for this amount of correction, but it is far from the **upper limit** of what LASIK can achieve. - This level of correction requires minimal corneal reshaping and typically results in a very high success rate and predictable outcomes.
Question 839: Which of the following statements about pterygium is false?
- A. Arise from any part of conjunctiva (Correct Answer)
- B. Can cause astigmatism
- C. Surgery is treatment of choice
- D. UV exposure is risk factor
Explanation: ***Arise from any part of conjunctiva*** **(FALSE - Correct Answer)** - This statement is **FALSE** and thus the correct answer. - Pterygium characteristically arises from the **nasal (interpalpebral) bulbar conjunctiva** in 90-95% of cases. - It does NOT arise from "any part" - it has a specific predilection for the medial (nasal) limbus in the palpebral fissure zone. - Temporal pterygium is much less common (~10% of cases). *Can cause astigmatism* **(TRUE)** - This statement is TRUE. - As a pterygium grows across the cornea, it can induce **corneal astigmatism** by altering the curvature of the cornea. - This irregular corneal surface can blur vision, especially as the pterygium progresses towards the central visual axis. *Surgery is treatment of choice* **(TRUE)** - This statement is TRUE. - **Surgical excision** is the primary treatment for pterygium when it is symptomatic, threatens vision, or causes significant cosmetic concerns. - Indications for surgery include: growth towards the visual axis, inducing high astigmatism, significant discomfort, or cosmetic desire. - Adjunctive measures (mitomycin C, conjunctival autograft) help reduce recurrence. *UV exposure is risk factor* **(TRUE)** - This statement is TRUE. - **Ultraviolet (UV) radiation exposure** is a well-established and significant risk factor for the development and progression of pterygium. - This explains its higher prevalence in individuals living in sunny climates (between 37° N and 37° S latitude - "pterygium belt") and those with outdoor occupations.
Radiology
1 questionsWhich of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?
NEET-PG 2015 - Radiology NEET-PG Practice Questions and MCQs
Question 831: Which of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?
- A. Ultrasound (Correct Answer)
- B. CT scan (Contrast-enhanced)
- C. Plain radiography (X-ray)
- D. MRI
Explanation: ***Ultrasound*** - **First-line imaging modality** for suspected acute appendicitis in young adults, especially in children, pregnant women, and young females - **Advantages:** No ionizing radiation, readily available, cost-effective, can be performed at bedside - **High specificity** (>90%) when positive findings are present - **Graded compression technique** helps visualize the appendix and assess for periappendiceal inflammation - **Limitations:** Operator-dependent, may be difficult in obese patients or with overlying bowel gas *CT scan (Contrast-enhanced)* - **Most sensitive imaging modality** (sensitivity >95%) for acute appendicitis - Considered when ultrasound is inconclusive or technically difficult - **Gold standard** in adults, especially in obese patients - Provides excellent visualization of the appendix and complications (perforation, abscess) - However, involves **ionizing radiation**, making it less ideal as first-line in young patients *MRI* - **Preferred in pregnant women** when ultrasound is inconclusive - No ionizing radiation exposure - High accuracy but **limited availability**, longer scan time, and higher cost - Not typically used as first-line imaging in non-pregnant young adults *Plain radiography (X-ray)* - **Limited role** in diagnosing acute appendicitis - Non-specific findings; may show fecalith, loss of psoas shadow, or signs of perforation - Cannot reliably visualize the appendix - **Not recommended** as initial imaging for suspected appendicitis