Master chua ophthalmology mcq of optics for NEET PG, AIIMS, NEXT, and MRCSEd with this comprehensive MCQ guide on keratometers, lensometers, retinoscopes, autorefractors, and perimetry. Learn corneal curvature, astigmatism measurement, lens power evaluation, retinoscopy, automated refraction, and visual field testing with clinically focused explanations. More Ophthalmology mcq Visit Our Index page click here
Q121. The keratometer is used to measure:
A. Axial length
B. Corneal curvature
C. Retinal thickness
D. Lens power
View Answer
B. Corneal curvature ✅ Exp: Measures radius of curvature of the anterior corneal surface.
Q122. The main principle of keratometry is:
A. Reflection from corneal apex
B. Refraction through the cornea
C. Parallax
D. Diffraction
View Answer
A. Reflection from corneal apex ✅ Exp: Based on reflected image size from corneal surface (first Purkinje image).
Q123. The instrument uses which optical principle?
A. Convex lens
B. Convex mirror
C. Prism deviation
D. Interference
View Answer
B. Convex mirror ✅ Exp: Corneal surface acts as a convex mirror reflecting mires.
Q124. Normal corneal curvature corresponds to refractive power of about:
A. +30 D
B. +43 D
C. +50 D
D. +60 D
View Answer
B. +43 D ✅ Exp: Average keratometric value = 43 D (radius ≈ 7.8 mm).
Q125. Javal–Schiotz keratometer uses:
A. Fixed image size, variable object size
B. Fixed object and image size
C. Variable mirror
D. Digital analysis
View Answer
A. Fixed image size, variable object size ✅ Exp: Uses doubling system for precise measurement of astigmatism.
chua ophthalmology mcq
Q126. The Bausch and Lomb keratometer uses:
A. Fixed object size, variable image size
B. Variable object and image
C. Dual reflection
D. Manual scaling
View Answer
A. Fixed object size, variable image size ✅ Exp: Measures corneal curvature by varying image size.
Q127. Keratometer readings represent:
A. Total corneal power
B. Posterior corneal curvature
C. Corneal refractive index only
D. Axial length
View Answer
A. Total corneal power ✅ Exp: Measures anterior surface assuming standard refractive index 1.3375.
Q128. Keratometry mainly measures:
A. Astigmatism
B. Myopia
C. Amblyopia
D. Convergence
View Answer
A. Astigmatism ✅ Exp: Determines type and amount of corneal astigmatism.
Q129. Keratometric index (1.3375) is used to account for:
A. Posterior corneal curvature
B. Tear film
C. Iris pigment
D. Accommodation
View Answer
A. Posterior corneal curvature ✅ Exp: Adjusts for the refractive contribution of posterior surface.
Q130. The reflected images seen in keratometry are called:
A. Purkinje images
B. Newton rings
C. Retinal reflex
D. Pupil images
View Answer
A. Purkinje images ✅ Exp: First Purkinje image from anterior corneal surface
chua ophthalmology mcq
Q131. Keratometry readings are expressed in:
A. Millimeters and diopters
B. Degrees only
C. Seconds of arc
D. Microns
View Answer
A. Millimeters and diopters ✅ Exp: Curvature radius (mm) → refractive power (D).
Q132. Steeper corneal curvature gives:
A. Lower dioptric power
B. Higher dioptric power
C. No change
D. Irregular reflection
View Answer
B. Higher dioptric power ✅ Exp: Smaller radius → higher refractive power.
Q133. Keratometry cannot measure:
A. Central 3 mm of cornea
B. Entire corneal surface
C. Total refraction
D. Posterior curvature
View Answer
A. Central 3 mm of cornea ✅ Exp: Measures only central zone of cornea.
Q134. Modern automated keratometers also provide:
A. Corneal topography
B. Pupil size
C. Axial length
D. Visual acuity
View Answer
A. Corneal topography ✅ Exp: Capture curvature maps for irregular astigmatism and keratoconus.
Q135. Lensometer is used to measure:
A. IOL power
B. Spectacle lens power
C. Corneal power
D. Field of view
View Answer
B. Spectacle lens power ✅ Exp: Determines spherical, cylindrical, and axis of lenses.
chua ophthalmology mcq
Q136. Principle of lensometer:
A. Focusing a target image through the test lens
B. Reflection
C. Diffraction
D. Polarization
View Answer
A. Focusing a target image through the test lens ✅ Exp: Uses the principle of Badal’s optometer.
Q137. Power of unknown lens =
A. Difference between target positions
B. Thickness of lens
C. Refractive index
D. Base curve
View Answer
A. Difference between target positions ✅ Exp: Reading difference gives dioptric power.
Q138. Axis marker in lensometer used to:
A. Locate cylindrical axis
B. Center optical axis
C. Align pupil
D. Focus target
View Answer
A. Locate cylindrical axis ✅ Exp: Rotating wheel determines cylinder axis orientation.
Q139. Lensometer prism compensator is used for:
A. High prism lenses
B. High cylinder lenses
C. Spherical lenses
D. Plano lenses
View Answer
A. High prism lenses ✅ Exp: Maintains alignment during measurement.
Q140. Marking pens in lensometer used to:
A. Center and orient lenses for glazing
B. Write prescription
C. Check IOL power
D. Align mirrors
View Answer
A. Center and orient lenses for glazing ✅ Exp: Marks optical center and axis lines for mounting.
Q141. Focimeter is another name for:
A. Lensometer
B. Keratometer
C. Autorefractor
D. Optometer
View Answer
A. Lensometer ✅ Exp: Both measure lens power.
Q142. The reference wavelength for lensometer calibration is:
A. 480 nm
B. 546 nm
C. 600 nm
D. 400 nm
View Answer
B. 546 nm ✅ Exp: Uses green light (e-line of mercury) for neutral refraction.
Q143. The reading target in lensometer appears as:
A. Crosslines or dots
B. Rings
C. Bright circle
D. Grid pattern
View Answer
A. Crosslines or dots ✅ Exp: Crosslines correspond to meridians of power.
Q144. A lens with +2.00 DS / –1.00 DC × 180 shows:
A. Two line foci separated by 1.00 D
B. One point focus
C. Virtual image
D. Prism shift
View Answer
A. Two line foci separated by 1.00 D ✅ Exp: Cylinder adds difference in one meridian.
Q145. Retinoscope is used to measure:
A. Axial length
B. Refractive error objectively
C. Pupil size
D. Accommodation amplitude
View Answer
B. Refractive error objectively ✅ Exp: Determines refraction by observing retinal reflex movement.
Q146. Retinoscopy is based on:
A. Movement of retinal reflex
B. Mirror reflection
C. Prism deviation
D. Optical coherence
View Answer
A. Movement of retinal reflex ✅ Exp: Direction of reflex guides lens correction.
chua ophthalmology mcq
Q147. “With” movement in retinoscopy indicates:
A. Hypermetropia
B. High myopia
C. Emmetropia
D. Astigmatism
View Answer
A. Hypermetropia ✅ Exp: “With” motion → focus behind retina → need plus lens.
Q148. “Against” movement indicates:
A. Myopia
B. Hypermetropia
C. Emmetropia
D. Astigmatism
View Answer
A. Myopia ✅ Exp: “Against” → focus in front of retina → need minus lens.
Q149. Neutral point in retinoscopy occurs when:
A. Reflex fills pupil with no movement
B. Bright reflex
C. Dark reflex
D. Maximum glow
View Answer
A. Reflex fills pupil with no movement ✅ Exp: Indicates far point conjugate with examiner’s pupil.
Q150. Working distance correction (at 66 cm) =
A. 1.50 D
B. 1.00 D
C. 2.00 D
D. 0.75 D
View Answer
A. 1.50 D ✅ Exp: 1/0.66 ≈ +1.50 D subtracted from gross result.
Q151. Plane mirror retinoscope produces:
A. “With” movement
B. “Against” always
C. Stationary reflex
D. None
View Answer
A. “With” movement ✅ Exp: Plane mirror: light diverges; concave: converges.
Q152. Cycloplegic refraction eliminates:
A. Accommodation
B. Astigmatism
C. Spherical power
D. Convergence
View Answer
A. Accommodation ✅ Exp: Gives true refractive status.
Q153. Autorefractors determine refraction using:
A. Infrared light reflection
B. Visible light
C. Sound waves
D. Polarization
View Answer
A. Infrared light reflection ✅ Exp: Measure reflected light from retina for objective refraction.
Q154. Autorefractors provide:
A. Objective refraction data
B. Subjective refraction
C. Visual acuity
D. Stereopsis
View Answer
A. Objective refraction data ✅ Exp: Rapid computerized refraction before subjective testing.
Q155. Advantage of autorefractor:
A. Quick and reproducible
B. Eliminates subjective testing completely
C. Always more accurate
D. Cannot detect astigmatism
View Answer
A. Quick and reproducible ✅ Exp: Used for screening and preliminary refraction.
chua ophthalmology mcq
Q156. Perimetry measures:
A. Visual field
B. Visual acuity
C. Contrast
D. Pupil response
View Answer
A. Visual field ✅ Exp: Detects defects in visual field from retinal or neural causes.
Q157. The principle of perimetry:
A. Light threshold detection
B. Accommodation
C. Convergence
D. Spherical reflection
View Answer
A. Light threshold detection ✅ Exp: Determines smallest light intensity visible in various directions.
Q158. Standard automated perimetry uses:
A. Static threshold method
B. Kinetic moving target
C. Prism field
D. Flash stimuli
View Answer
A. Static threshold method ✅ Exp: Tests sensitivity at fixed locations with varying brightness.
Q159. Tangent screen perimetry is used for:
A. Central 30° field
B. Peripheral vision only
C. Color vision
D. Acuity
View Answer
A. Central 30° field ✅ Exp: Projects targets on flat black screen for central defects.
Q160. Bjerrum screen detects:
A. Central and paracentral scotomas
B. Total blindness
C. Diplopia
D. Astigmatism
View Answer
A. Central and paracentral scotomas ✅ Exp: Especially useful in early glaucoma field testing.
