Get the complete Q281–320 MCQs from Ophthal mcq book A.K. Khurana’s Optics of Lenses & Ophthalmic Instrument covering optical instrument calibration, common errors, illumination systems & clinical applications. Perfect for NEET PG, NEXT, AIIMS, Optometry & MRCSEd exam prep. More Ophthalmology and Optometry MCQ
Q281. Calibration of keratometer ensures:
A. Accurate corneal curvature readings
B. Reduced astigmatism
C. Clearer reflection
D. High magnification
View Answer
A. Accurate corneal curvature readings ✅ Exp: Standardized using steel balls of known curvature.
Q282. Lensometer calibration verified using:
A. Standard test lenses
B. Calibration mirror
C. Retinoscope
D. Prism bar
View Answer
A. Standard test lenses ✅ Exp: Power readings checked against known diopters.
Q283. Slit-lamp calibration ensures:
A. Beam width and angle accuracy
B. Lens magnification
C. Image inversion
D. Field adjustment
View Answer
A. Beam width and angle accuracy ✅ Exp: Vital for anterior chamber measurements.
Q284. Perimeter calibration involves:
A. Checking background luminance
B. Target color
C. Refractive power
D. Headrest stability
View Answer
A. Checking background luminance ✅ Exp: Ensures uniform sensitivity testing.
Q285. Retinoscope calibration checks:
A. Filament alignment and mirror angle
B. Power reading
C. Field size
D. Polarization
View Answer
A. Filament alignment and mirror angle ✅ Exp: Misalignment leads to reflex errors.
Q286. Optical instrument illumination calibrated by:
A. Luminance meter
B. Photodiode
C. Colorimeter
D. Pupilometer
View Answer
A. Luminance meter ✅ Exp: Ensures light intensity within safety limits.
Q287. Zero error in lensometer indicates:
A. Incorrect neutralization
B. Misaligned reticle
C. Filter problem
D. Wrong prism reading
View Answer
A. Incorrect neutralization ✅ Exp: Verified with plano lens or empty holder.
Q288. Recalibration of autorefractor required:
A. Periodically for accuracy
B. Only after repair
C. Never
D. After every test
View Answer
A. Periodically for accuracy ✅ Exp: Mechanical drift can alter measurements.
Q289. Keratometer calibration reference index =
A. 1.3375
B. 1.376
C. 1.4
D. 1.333
View Answer
A. 1.3375 ✅ Exp: Compensates for posterior corneal curvature.
Q290. Incorrect calibration leads to:
A. Measurement error
B. Increased magnification
C. Better focus
D. Reduced glare
View Answer
A. Measurement error ✅ Exp: Causes false diagnosis in refraction or curvature.
Ophthal mcq book Optical Instruments
Q291. The most common error in retinoscopy:
A. Wrong working distance
B. Pupil centration
C. Mirror alignment
D. Overillumination
View Answer
A. Wrong working distance ✅ Exp: Incorrect distance causes power miscalculation.
Q292. Autorefractor readings may be unreliable in:
A. Media opacities
B. Myopia
C. Astigmatism
D. Emmetropia
View Answer
A. Media opacities ✅ Exp: Cataract or corneal opacity causes reflection errors.
Q293. Parallax error in retinoscopy arises when:
A. Observation not aligned with pupil
B. Too close to patient
C. Excess light
D. In dark room
View Answer
A. Observation not aligned with pupil ✅ Exp: Off-axis viewing misrepresents reflex motion.
Q294. Keratometric error occurs due to:
A. Improper focusing of mires
B. Tear film stability
C. Light color
D. Accommodation
View Answer
A. Improper focusing of mires ✅ Exp: Unclear mire image gives false curvature readings.
Q295. In slit-lamp exam, excessive beam intensity may cause:
A. Photophobia and reflex tearing
B. Improved resolution
C. Increased depth
D. Better focus
View Answer
A. Photophobia and reflex tearing ✅ Exp: Too bright light irritates patient and obscures details.
Q296. Ophthalmoscope image distortion occurs due to:
A. Off-axis viewing
B. Central focusing
C. Low light intensity
D. High diopter lens
View Answer
A. Off-axis viewing ✅ Exp: Eccentric observation distorts retinal view.
Q297. Lensometer parallax avoided by:
A. Centering target and eyepiece alignment
B. Increasing magnification
C. Moving lens holder
D. Reducing illumination
View Answer
A. Centering target and eyepiece alignment ✅ Exp: Alignment ensures correct focal plane reading.
Q298. Perimetry false-negative errors occur when:
A. Patient misses seen target
B. Fixation loss
C. Eye movement
D. High brightness
View Answer
A. Patient misses seen target ✅ Exp: Indicates inattentiveness or fatigue.
Q299. False-positive perimetry error means:
A. Responding to no stimulus
B. Missing bright target
C. Poor calibration
D. Tear film artifact
View Answer
A. Responding to no stimulus ✅ Exp: Patient overresponds; unreliable test.
Q300. Retinoscope reflex too bright indicates:
A. Overillumination or large pupil
B. Under-correction
C. Astigmatism
D. Short focus
View Answer
A. Overillumination or large pupil ✅ Exp: Adjust brightness for optimal reflex observation.
Ophthal mcq book Optical Instruments
Q301. The main illumination system in ophthalmic optics is:
A. Koehler illumination
B. Diffuse reflection
C. Paraxial alignment
D. Pupil conjugation
View Answer
A. Koehler illumination ✅ Exp: Provides uniform light distribution for microscopes.
Q302. Koehler illumination ensures:
A. Even field illumination
B. Increased contrast only
C. Reduced magnification
D. Direct reflection
View Answer
A. Even field illumination ✅ Exp: Separates field and aperture planes optically.
Q303. Critical illumination differs by:
A. Direct imaging of light source on specimen
B. Diffused light path
C. Prism reflection
D. Polarization
View Answer
A. Direct imaging of light source on specimen ✅ Exp: Simpler but less uniform than Koehler.
Q304. Neutral density filters used to:
A. Reduce light intensity without color change
B. Improve focus
C. Change wavelength
D. Polarize beam
View Answer
A. Reduce light intensity without color change ✅ Exp: Maintain color fidelity during brightness reduction.
Q305. Diffuser in slit lamp provides:
A. Even low-intensity illumination
B. Increase magnification
C. Narrow beam
D. Focused field
View Answer
A. Even low-intensity illumination ✅ Exp: Used for diffuse illumination of ocular surface.
Q306. Polarizing filters reduce:
A. Surface glare and reflections
B. Resolution
C. Magnification
D. Field of view
View Answer
A. Surface glare and reflections ✅ Exp: Used in corneal imaging and fundus photography.
Q307. Cobalt blue filter function:
A. Excites fluorescein dye
B. Increases magnification
C. Enhances red vessels
D. Filters UV
View Answer
A. Excites fluorescein dye ✅ Exp: Used for corneal defect evaluation.
Q308. Heat-absorbing filter prevents:
A. Thermal damage to ocular tissues
B. Chromatic aberration
C. Glare
D. Spherical aberration
View Answer
A. Thermal damage to ocular tissues ✅ Exp: Protects cornea and lens from infrared heat.
Q309. Barrier filter allows:
A. Only specific emission wavelength
B. Excitation light
C. Full spectrum
D. Infrared radiation
View Answer
A. Only specific emission wavelength ✅ Exp: Used in fundus fluorescein angiography.
Q310. Red-free filter improves visibility of:
A. Retinal vessels
B. Macular pigment
C. Vitreous
D. Lens cortex
View Answer
A. Retinal vessels ✅ Exp: Enhances contrast between blood vessels and background.
Ophthal mcq book Optical Instruments
Q311. In retinoscopy, dull reflex suggests:
A. High ametropia
B. Low illumination
C. Normal focus
D. Astigmatism
View Answer
A. High ametropia ✅ Exp: Far from neutrality → slower, dimmer reflex.
Q312. “Scissors reflex” indicates:
A. Irregular astigmatism
B. Myopia
C. Hyperopia
D. Corneal opacity
View Answer
A. Irregular astigmatism ✅ Exp: Reflex moves unevenly due to irregular surface curvature.
Q313. Keratometer readings fluctuating indicate:
A. Unstable tear film
B. Calibration error
C. Incorrect index
D. Small pupil
View Answer
A. Unstable tear film ✅ Exp: Tear instability alters reflected mire pattern.
Q314. Lensometer target not visible means:
A. Lens not centered
B. Wrong wavelength
C. Overillumination
D. Filter issue
View Answer
A. Lens not centered ✅ Exp: Proper centration needed for focus alignment.
Q315. Ophthalmoscope glare caused by:
A. Corneal reflection
B. Wrong diopter
C. Dim illumination
D. Large pupil
View Answer
A. Corneal reflection ✅ Exp: Angle adjustment reduces reflex glare.
Q316. Slit-lamp corneal haze best examined using:
A. Oblique illumination
B. Retroillumination
C. Diffuse light
D. Direct
View Answer
A. Oblique illumination ✅ Exp: Oblique light highlights epithelial and stromal opacities.
Q317. Retroillumination highlights:
A. Lens opacities
B. Corneal edema
C. Iris pattern
D. Pupil block
View Answer
A. Lens opacities ✅ Exp: Uses fundus reflex to visualize backscatter lesions.
Q318. Purkinje images observed in:
A. Lens curvature evaluation
B. Retinoscopy
C. Perimetry
D. Tonometry
View Answer
A. Lens curvature evaluation ✅ Exp: Reflection images help in cataract surgery alignment.
Q319. Optical axis misalignment in instruments causes:
A. Aberration and measurement error
B. Clearer image
C. Reduced glare
D. Larger field
View Answer
A. Aberration and measurement error ✅ Exp: Alignment is key for precision optical readings.
Q320. Proper instrument maintenance prevents:
A. Optical drift and calibration errors
B. Increased aberration
C. Reduced magnification
D. Patient discomfort
View Answer
A. Optical drift and calibration errors ✅ Exp: Regular cleaning, calibration, and bulb replacement ensure accuracy.
Ophthal mcq book Optical Instruments.
