NEET-PG 2015 Practice Questions

Q: What is the average axial length of the human eyeball?

24 mm. ***24 mm*** - The **average axial length** of the human eyeball is approximately **24 mm**. - This length is crucial for **emmetropia**, where parallel light rays focus precisely on the retina. *16 mm* - An axial length of **16 mm** would indicate extreme **hyperopia** (farsightedness), as the eyeball would be significantly too short [1]. - This would result in light focusing behind the retina, leading to blurry vision. *20 mm* - An axial length of **20 mm** is still considerably shorter than average, suggesting **significant hyperopia**. - This deviation from the norm would impair visual acuity without corrective lenses. *28 mm* - An axial length of **28 mm** would classify the eye as significantly **myopic** (nearsighted), as the eyeball would be too long [1]. - In this case, light would focus in front of the retina, causing distant objects to appear blurry [1].

Q: Which of the following methods is not used to measure refractive error?

Spectrometry. ***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.

Q: Which is the most powerful refractive surface of the eye?

Cornea. ***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.

Q: Strabismic amblyopia is more common in patients with:

Constant strabismus. **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.

Q: What term describes a condition where the axial length of the eye does not match its refractive power?

Axial Ametropia. ***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.

Q: In a case of myopia, LASIK can correct up to how many diopters?

-12D. ***-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.

Q: Which of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?

Ultrasound. ***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

Question 1

What is the average axial length of the human eyeball?

Accepted Answer

24 mm

Answer

16 mm

Answer

20 mm

Answer

28 mm

Question 2

Which of the following methods is not used to measure refractive error?

Accepted Answer

Spectrometry

Answer

Keratometry

Answer

Retinoscopy

Answer

Refractometry

Question 3

Aniseikonia is ?

Accepted Answer

Projection of different sized images into visual cortex of two retinae

Answer

Projection of different colored images into the visual cortex of one eye

Answer

Change in the perception of object size due to distance

Answer

Temporary visual disturbances affecting one eye

Question 4

Which is the most powerful refractive surface of the eye?

Accepted Answer

Cornea

Answer

Conjunctiva

Answer

Vitreous

Answer

Lens

Question 5

Strabismic amblyopia is more common in patients with:

Accepted Answer

Constant strabismus

Answer

Alternating strabismus

Answer

Latent strabismus

Answer

Intermittent strabismus

Question 6

Astigmatism is defined as?

Accepted Answer

Refractive error wherein refraction varies along different meridians

Answer

Refractive error due to long AP length of eyeball

Answer

Varying refractive error in both eyes

Answer

Varying shape perception by both eyes

Question 7

What is regular astigmatism?

Accepted Answer

Astigmatism where the principal meridians are at a 90-degree angle to each other

Answer

Astigmatism in which the principal meridians are parallel

Answer

Asymptomatic astigmatism

Answer

Astigmatism as a result of cataract surgery

Question 8

What term describes a condition where the axial length of the eye does not match its refractive power?

Accepted Answer

Axial Ametropia

Answer

Anisokonia

Answer

Emmetropia

Answer

Curvature ametropia

Question 9

In a case of myopia, LASIK can correct up to how many diopters?

Accepted Answer

-12D

Answer

-4D

Answer

-20D

Answer

-6D

Question 10

Which of the following imaging modalities is most appropriate for initial evaluation of suspected acute appendicitis in a young adult patient?

Accepted Answer

Ultrasound

Answer

CT scan (Contrast-enhanced)

Answer

Plain radiography (X-ray)

Answer

MRI

NEET-PG 2015

Ophthalmology

Radiology