Master Clinical Refraction concepts with 40 high-yield Optometry exam questions MCQs (201–240) on trial lenses, trial frames, and vertex distance. Each question includes accurate answers and concise explanations—perfect for optometry, ophthalmology exams, and clinical refraction practice. Covers lens types, vertex distance formulas, frame adjustments, aberrations, and coatings for complete understanding.
Trial Lenses & Frames Optometry exam questions
201 Trial lenses are used for:
A. Objective refraction only
B. Subjective refraction
C. Retinoscopy
D. Perimetry
View Answer
B. Subjective refraction ✅ Exp: The patient gives responses to test lenses for best clarity.
202. Trial lens sets usually have steps of:
A. 0.12 D
B. 0.25 D
C. 0.50 D
D. 1.00 D
View Answer
B. 0.25 D ✅ Exp: Fine grading in 0.25 D steps for precise correction.
203. In a standard trial set, maximum spherical power is:
A. ±10 D
B. ±20 D
C. ±6 D
D. ±12 D
View Answer
B. ±20 D ✅ Exp: Allows testing of both high myopia and hypermetropia.
204. The trial frame should align optical centers with:
A. Pupillary centers
B. Limbus
C. Iris margin
D. Corneal apex
View Answer
A. Pupillary centers ✅ Exp: Prevents unwanted prism or aberration.
205. PD (pupillary distance) adjustment is crucial because:
A. Prevents chromatic aberration
B. Avoids prismatic imbalance
C. Improves accommodation
D. Increases magnification
View Answer
B. Avoids prismatic imbalance ✅ Exp: Misalignment induces unwanted base-in or base-out effects.
Lens Types & Markings Optometry exam questions
206. Spherical lenses have:
A. Equal curvature in all meridians
B. Different curvature
C. Flat one side only
D. Toroidal shape
View Answer
A. Equal curvature in all meridians ✅ Exp: Same refractive power in all meridians.
207. Cylindrical lenses have:
A. Power in all meridians
B. Power in one meridian only
C. No axis
D. Same as prisms
View Answer
B. Power in one meridian only ✅ Exp: Refracts light in one plane to correct astigmatism.
208. Axis of a plus cylinder is:
A. Meridian of maximum curvature
B. Meridian of no power
C. Meridian of maximum power
D. Meridian of minimum power
View Answer
B. Meridian of no power ✅ Exp: Axis lies perpendicular to the meridian with refractive effect.
209. Axis markings on trial lenses are spaced at:
A. 30° intervals
B. 15° intervals
C. 45° intervals
D. 60° intervals
View Answer
A. 30° intervals ✅ Exp: Standard trial lenses marked every 30° for axis alignment.
210. Plano lens means:
A. No spherical power
B. No axis
C. Equal curvatures
D. Cylindrical lens
View Answer
A. No spherical power ✅ Exp: Flat surface → 0.00 D refractive power.
Vertex Distance
211. Vertex distance is the:
A. Distance between cornea and spectacle lens
B. Distance between lens and retina
C. Pupillary distance
D. Distance between lenses3
View Answer
A. Distance between cornea and spectacle lens ✅ Exp: Usually 12–14 mm in spectacles.
212. Vertex distance affects:
A. Spherical equivalent
B. Axis orientation
C. Cylindrical power only
D. Accommodation
View Answer
A. Spherical equivalent ✅ Exp: Changes effective power for high prescriptions.
213. For plus lenses, increasing vertex distance:
A. Increases effective power
B. Decreases effective power
C. No effect
D. Causes axis rotation
View Answer
A. Increases effective power ✅ Exp: Lens farther → greater vergence at cornea.
214 For minus lenses, increasing vertex distance:
A. Increases effective power
B. Decreases effective power
C. No effect
D. Reverses sign
View Answer
B. Decreases effective power ✅ Exp: Lens farther → less minus effect.
215. Vertex correction is essential for powers:
A. ±2 D or more
B. ±4 D or more
C. ±1 D
D. ±8 D only
View Answer
Effective Power Calculation
216. Effective power (Fe) formula is:
A. F / (1 – dF)
B. F × d
C. 1/F
D. F + d
View Answer
A. F / (1 – dF) ✅ Exp: Fe = F / (1 – dF), where d = distance (m) from eye.
217. If +10 D lens moved 10 mm away, Fe =
A. +9.9 D
B. +11.1 D
C. +10.5 D
D. +9.0 D
View Answer
B. +11.1 D ✅ Exp: Fe = 10 / (1 – 0.01×10) = 11.1 D.
218 If –10 D lens moved 10 mm away, Fe =
A. –9 D
B. –11 D
C. –10.5 D
D. –8 D
View Answer
A. –9 D ✅ Exp: Fe = –10 / (1 – 0.01×–10) = –9.09 D.
219. Vertex distance effect negligible for:
A. High myopia
B. Low refractive errors (< ±4 D)
C. Aphakia
D. High hypermetropia
View Answer
B. Low refractive errors (< ±4 D) ✅ Exp: Small vergence difference at low powers.
220. Effective power correction more important in:
A. Contact lenses to spectacles
B. Spectacles to spectacles
C. IOLs
D. Bifocals only
View Answer
A. Contact lenses to spectacles ✅ Exp: Contact lenses sit directly on cornea → different vertex.
Trial Frame Adjustments Optometry exam questions
221. Pantoscopic tilt refers to:
A. Downward tilt of spectacle plane
B. Inward lens rotation
C. Forward displacement
D. Vertical PD shift
View Answer
A. Downward tilt of spectacle plane ✅ Exp: Lens tilted ~10–15° for cosmetic fit and field optimization.
222 Excessive pantoscopic tilt causes:
A. Induced astigmatism
B. Magnification
C. Color distortion
D. Myopia
View Answer
A. Induced astigmatism ✅ Exp: Alters effective power along oblique meridians.
223. Trial frame height adjustment ensures:
A. Equal accommodation
B. Centered visual axis
C. Binocular disparity
D. Reduced reflections
View Answer
B. Centered visual axis ✅ Exp: Maintains optical alignment with pupil.
224. Frame vertex distance increased by:
A. Moving temples outward
B. Moving bridge forward
C. Increasing PD
D. Reducing pantoscopic tilt
View Answer
B. Moving bridge forward ✅ Exp: Forward shift increases lens–cornea gap.
225. PD for near work is:
A. Larger
B. Smaller
C. Equal
D. Unchanged
View Answer
B. Smaller ✅ Exp: Eyes converge → reduced near PD.
Lens Properties & Magnification
226. Plus lenses cause:
A. Image magnification
B. Minification
C. No change
D. Field reduction only
View Answer
A. Image magnification ✅
227. Minus lenses cause:
A. Image minification
B. Magnification
C. Field narrowing
D. No change
View Answer
A. Image minification ✅ Exp: Diverging lenses reduce image size.
228. Magnification of +10 D lens at 12 mm vertex =
A. 2%
B. 10%
C. 15%
D. 25%
View Answer
B. 10% ✅ Exp: Approx. 1% magnification per diopter of power.
229. Contact lenses cause:
A. More magnification
B. Less magnification/minification
C. Same effect
D. Increased distortion
View Answer
B. Less magnification/minification ✅ Exp: Minimal vertex → minimal size distortion.
230. High plus spectacles produce:
A. Barrel distortion
B. Pincushion distortion
C. Chromatic aberration
D. Astigmatism
View Answer
A. Barrel distortion ✅ Exp: Due to magnification toward lens periphery.
Lens Aberrations
231. Spherical aberration occurs because:
A. Peripheral rays refract more
B. Chromatic difference
C. Unequal curvature
D. Tilted axis
View Answer
A. Peripheral rays refract more ✅ Exp: Peripheral rays focus closer than paraxial rays.
232. Chromatic aberration caused by:
A. Different refractive indices for colors
B. Lens tilt
C. Axial misalignment
D. Unequal curvature
View Answer
A. Different refractive indices for colors ✅ Exp: Blue refracted more than red due to dispersion.
233. Coma results from:
A. Off-axis object rays
B. Unequal meridians
C. Cylindrical distortion
D. Tilted cornea
View Answer
A. Off-axis object rays ✅ Exp: Produces comet-shaped image points.
234. Distortion due to magnification variation:
A. Barrel & pincushion
B. Spherical aberration
C. Chromatic
D. Coma
View Answer
A. Barrel & pincushion ✅ Exp: Edge magnification difference leads to shape change.
235. Astigmatic error due to lens tilt =
A. Oblique astigmatism
B. Chromatic
C. Distortion
D. Coma
View Answer
A. Oblique astigmatism ✅ Exp: Tilt alters meridional focus → induced cylinder.
Lens Materials & Coatings Optometry exam questions
236. Crown glass refractive index ≈
A. 1.5
B. 1.7
C. 1.3
D. 1.4
View Answer
A. 1.5 ✅ Exp: Standard optical glass material for lenses.
237. Flint glass refractive index ≈
A. 1.6–1.7
B. 1.3
C. 1.4
D. 1.5
View Answer
A. 1.6–1.7 ✅ Exp: Higher index, used in bifocals and prisms.
238. High-index lenses reduce:
A. Lens thickness
B. Refractive power
C. Chromatic aberration
D. Reflection
View Answer
A. Lens thickness ✅ Exp: Thinner and lighter for same optical power.
239. Anti-reflective coating reduces:
A. Glare and reflection
B. Chromatic aberration
C. Astigmatism
D. Distortion
View Answer
A. Glare and reflection ✅ Exp: Increases light transmission (~99%).
240. Scratch-resistant coating applied to:
A. Glass
B. Plastic lenses
C. High-index only
D. Mineral lenses
View Answer
B. Plastic lenses ✅ Exp: Protects soft plastic lens surface from wear.
