Master clinical refraction in optometry and ophthalmology concepts with 40 high-yield MCQs (241–280) on Aphakia, Pseudophakia, Contact Lens optics, and Low Vision aids. Each question includes concise, accurate explanations—ideal for optometry and ophthalmology mcq, and NEET-PG, DHS, DMER exam preparation.
Aphakia – Basics & Optical Implications
241. Aphakia means:
A. Absence of cornea
B. Absence of crystalline lens
C. Absence of iris
D. Loss of retina
View Answer
B. Absence of crystalline lens ✅ Exp: Occurs after cataract extraction or congenital absence of lens.
242. Total refractive power of emmetropic eye ≈
A. +40 D
B. +60 D
C. +100 D
D. +50 D
View Answer
B. +60 D ✅ Exp: Cornea ≈ +43 D, lens ≈ +17 D.
243. After lens removal (aphakia), eye becomes:
A. Myopic
B. Hypermetropic
C. Emmetropic
D. Astigmatic
View Answer
B. Hypermetropic ✅ Exp: Loss of lens power → focus behind retina.
244. Typical refractive correction in aphakia:
A. +5 D
B. +10 D
C. +10 to +12 D
D. +20 D
View Answer
C. +10 to +12 D ✅ Exp: Depends on axial length and corneal curvature.
245. Aphakia causes image:
A. Magnification
B. Minification
C. No change
D. Distortion only
View Answer
A. Magnification ✅ Exp: +10 D lens magnifies image by ~25–30%.
Aphakic Spectacles vs Contact Lenses optometry and ophthalmology
246. Spectacle correction in aphakia leads to:
A. Peripheral scotoma
B. Image minification
C. Field enlargement
D. No distortion
View Answer
A. Peripheral scotoma ✅ Exp: “Jack-in-the-box” phenomenon due to prismatic ring scotoma.
247. Aniseikonia in unilateral aphakia due to:
A. Magnification difference
B. Prismatic error
C. Cylinder misalignment
D. Retinal distortion
View Answer
A. Magnification difference ✅ Exp: Image in aphakic eye ~25% larger.
248. Best optical correction for unilateral aphakia:
A. Spectacles
B. Contact lens
C. Bifocals
D. IOL only
View Answer
B. Contact lens ✅ Exp: Minimizes aniseikonia due to negligible vertex distance.
240. Bilateral aphakia best corrected with:
A. Spectacles
B. IOL implantation
C. Contact lenses
D. Magnifiers
View Answer
B. IOL implantation ✅ Exp: IOLs restore physiological optics and binocular balance.
250. Aphakic glasses cause:
A. Barrel distortion
B. Pincushion distortion
C. Chromatic aberration
D. Spherical aberration
View Answer
A. Barrel distortion ✅ Exp: Magnification increases at periphery → barrel appearance.
Pseudophakia
251. Pseudophakia means:
A. Lens subluxation
B. Artificial intraocular lens implantation
C. Partial aphakia
D. Keratoplasty
View Answer
B. Artificial intraocular lens implantation ✅ Exp: Post-cataract surgery eye with implanted IOL.
252. Pseudophakic eye usually requires:
A. Bifocals for near
B. Distance correction only
C. No glasses
D. Minus lenses
View Answer
A. Bifocals for near ✅ Exp: Accommodation lost → near add needed.
253. Effective power of IOL =
A. +5 D
B. +10 D
C. +19–+22 D
D. +25 D
View Answer
C. +19–+22 D ✅ Exp: Chosen based on axial length and corneal curvature.
254. IOL power formula based on:
A. SRK or Holladay formula
B. Snell’s law
C. Paraxial ray theory
D. Astigmatic cross
View Answer
A. SRK or Holladay formula ✅ Exp: Biometry equations estimate IOL power.
255. Pseudophakia typically causes:
A. Slight hypermetropia
B. High myopia
C. Astigmatism only
D. Presbyopia correction
View Answer
A. Slight hypermetropia ✅ Exp: Target refraction often slightly hyperopic post-surgery.
Contact Lens in Refractive Correction
256. Contact lenses are most beneficial in:
A. High myopia
B. Presbyopia
C. Hypermetropia
D. Emmetropia
View Answer
A. High myopia ✅ Exp: Reduce minification and aberrations from high minus lenses.
257. In anisometropia >3 D, contact lenses prevent:
A. Aniseikonia
B. Diplopia
C. Asthenopia
D. Strabismus
View Answer
A. Aniseikonia ✅ Exp: Equalize image size on both retinas.
258. Contact lens power is measured at:
A. Corneal plane
B. Spectacle plane
C. Retina
D. Vertex 12 mm
View Answer
A. Corneal plane ✅ Exp: Vertex distance = 0, changes effective power.
259. Contact lenses reduce:
A. Peripheral distortion
B. Central acuity
C. Accommodation
D. Spherical aberration only
View Answer
A. Peripheral distortion ✅ Exp: Conform closely to eye → better optical field.
260. Major limitation of contact lenses:
A. Cost
B. Infection risk
C. Chromatic aberration
D. Reduced acuity
View Answer
B. Infection risk ✅ Exp: Risk of microbial keratitis if hygiene poor.
Low Vision & Magnification
261. Low vision defined as best corrected VA less than:
A. 6/12
B. 6/18
C. 6/24
D. 6/60
View Answer
B. 6/18 ✅ Exp: WHO defines <6/18 but better than no perception of light.
262. Legal blindness (India) = VA worse than:
A. 6/18
B. 6/60
C. 3/60
D. 1/60
View Answer
B. 6/60 ✅ Exp: Best corrected VA <6/60 or visual field <20°.
263. Visual field restriction below 20° signifies:
A. Low vision
B. Legal blindness
C. Color blindness
D. Binocular diplopia
View Answer
B. Legal blindness ✅ Exp: Functionally blind though central vision may remain.
264. Magnifying power (M) =
A. D / 4
B. 4 / D
C. 1 / f
D. D / 10
View Answer
A. D / 4 ✅ Exp: For simple magnifier, M = Dioptric power / 4.
265. +20 D magnifier provides magnification of:
A. 2×
B. 5×
C. 10×
D. 20×
View Answer
B. 5× ✅ Exp: 20 / 4 = 5× magnification.
Low Vision Aids
266. Distance vision aid used in low vision:
A. Telescope
B. Magnifier
C. High-plus lens
D. Contact lens
View Answer
A. Telescope ✅ Exp: Increases retinal image size for distant objects.
267. Near vision aid for low vision:
A. Microscope
B. Telescope
C. Prism
D. IOL
View Answer
A. Microscope ✅ Exp: High-plus lenses enlarge near text.
268. Field expansion in tunnel vision by:
A. Reverse telescope
B. Bifocal
C. Contact lens
D. Mydriatic
View Answer
A. Reverse telescope ✅ Exp: Shrinks image → expands perceived field.
269. Telescopic lenses work on:
A. Refraction and reflection
B. Angular magnification
C. Spherical aberration
D. Binocular disparity
View Answer
B. Angular magnification ✅ Exp: Combination of objective and eyepiece lenses.
270. Hand magnifier suitable for:
A. Prolonged reading
B. Intermittent spot reading
C. Distance vision
D. Binocular use
View Answer
B. Intermittent spot reading ✅ Exp: Best for short-duration near tasks.
Prescribing in Low Vision optometry and ophthalmology
271. Magnification required =
A. Required VA / Present VA
B. 1 / VA
C. VA difference
D. LogMAR ratio
View Answer
A. Required VA / Present VA ✅ Exp: Ratio of desired to current visual acuity.
272. Example: if VA = 6/60, target 6/12 → required magnification =
A. 2×
B. 3×
C. 5×
D. 10×
View Answer
C. 5× ✅ Exp: 60 ÷ 12 = 5× magnification needed.
273. Dome magnifier advantage:
A. Increased working distance
B. Resting directly on page
C. Binocular field
D. Adjustable focus
View Answer
B. Resting directly on page ✅ Exp: Eliminates need for holding distance precisely.
274. CCTV magnifiers provide:
A. Electronic image magnification
B. Optical magnification
C. Spectacle-based magnification
D. Binocular magnification
View Answer
A. Electronic image magnification ✅ Exp: Camera projects enlarged image on screen.
275. Prism spectacles in low vision used for:
A. Field expansion
B. Accommodation
C. Astigmatism
D. Color contrast
View Answer
A. Field expansion ✅ Exp: Shift images to usable retina in field loss (hemianopia).
Special Situations & Modifications optometry and ophthalmology
276. Post-keratoplasty refraction often shows:
A. Irregular astigmatism
B. Myopia only
C. Hypermetropia only
D. Regular astigmatism
View Answer
A. Irregular astigmatism ✅ Exp: Corneal sutures and healing cause uneven curvature.
277. In pseudophakia with astigmatism, best correction by:
A. Toric IOL
B. Contact lens
C. Spectacles only
D. Cylindrical lens
View Answer
A. Toric IOL ✅ Exp: Built-in cylinder corrects corneal toricity.
278. Progressive addition lenses (PAL) advantage:
A. Smooth transition between distances
B. Fixed power
C. Narrow near field
D. High distortion
View Answer
A. Smooth transition between distances ✅ Exp: Gradual power change from distance to near.
279. Best correction for presbyopia in anisometropia:
A. Separate reading glasses for each eye
B. Bifocals with differential add
C. Progressive lenses
D. Contact lenses only
View Answer
B. Bifocals with differential add ✅ Exp: Different adds balance accommodation demands.
280. IOL calculation in post-LASIK eye requires:
A. Special formula (Barrett True-K)
B. SRK/T standard
C. Manual keratometry
D. Average corneal power only
View Answer
A. Special formula (Barrett True-K) ✅ Exp: True corneal power altered after LASIK → special formula used.
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