Optics and Refraction (Myopia, Hypermetropia, Astigmatism) MCQs

Ophthalmology · 43 free questions with answers & explanations.

1. A patient's cycloplegic refraction reveals -3.00 DS / -1.50 DC × 90°. The cylinder axis at 90° means the more myopic meridian (steeper corneal curvature) is located at:
2. A 10-year-old child complains of headache and difficulty reading. Cycloplegic refraction shows +3.50 D in both eyes. The manifest refraction (without cycloplegia) was +0.50 D. This difference represents:
3. A 12-year-old boy with progressive myopia of -3.00 D is counselled about myopia control. Which of the following interventions has the highest level of evidence for slowing myopia progression in children?
4. A patient's refraction is: right eye +3.00 DS / +2.00 DC × 90°. Converting to minus cylinder notation, the equivalent prescription is:
5. A 50-year-old emmetrope finds she needs +2.50 D reading glasses to read at 40 cm. Her amplitude of accommodation is now 1.00 D. She asks about multifocal contact lenses. What is the expected near addition required for clear vision at 40 cm, and what is the formula involved?
6. A myopic patient has an eyeglass prescription of -6.0 DS. She wants LASIK. Her corneal topography shows a K-max of 47.0 D, central corneal thickness 520 μm, and normal topographic pattern. The minimum residual stromal bed thickness after ablation must be maintained at:
7. A 55-year-old patient with presbyopia wants to understand why they can no longer accommodate. The mechanism of loss of accommodation with age (nuclear sclerosis theory/Helmholtz theory) is best explained as:
8. A patient's refraction is: -3.00 DS / -2.00 DC × 180°. This means the correcting cylinder axis is at 180°. What is the power of the most curved meridian of this eye's cornea (the principal meridian with maximum refraction)?
9. In the optical principle underlying LASIK surgery, the Munnerlyn formula calculates the depth of ablation required. For myopia correction of −5.0 D with an optical zone of 6 mm, the approximate ablation depth is closest to:
10. A patient's cycloplegic refraction shows +4.0 DS in the right eye while the manifest refraction shows +1.5 DS. The amount of latent hypermetropia is:
11. Orthokeratology (Ortho-K) for myopia control works through which optical mechanism to reduce myopia progression?
12. In the calculation of IOL power using the SRK/T formula, which parameter's measurement error causes the greatest magnitude of refractive surprise postoperatively?
13. A patient presents with irregular astigmatism post-LASIK with complaint of 'starbursts' and halos at night. Topography shows central island pattern. The refractive mechanism causing the symptoms is:
14. In retinoscopy, which of the following conditions would produce a 'with movement' of the retinoscopy reflex when using a plane mirror at a working distance of 67 cm?
15. A prescription written as -3.00DS / -2.00DC × 180 (negative cylinder form) is transposed to its positive cylinder equivalent. What is the correct positive cylinder form?
16. In orthokeratology (overnight corneal reshaping contact lenses) for myopia control, the primary mechanism of axial elongation inhibition is:
17. A patient has a spectacle prescription of −4.00 DS at vertex distance 12 mm. The equivalent contact lens power should be approximately:
18. In Javal's rule for estimating corneal astigmatism from keratometry, the formula is: Total ocular astigmatism = corneal astigmatism × 1.25 + (−0.50 × 90). This rule breaks down most frequently in:
19. A child has -4.00 DS / -2.00 DC × 90° in the right eye. The least myopic meridian (flattest) is at 90° and the most myopic (steepest) is at 180°. This is classified as:
20. In the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study, which clinical finding at baseline most strongly predicted progression to corneal transplantation?
21. Orthokeratology (Ortho-K) lenses slow myopia progression in children by which proposed primary mechanism?
22. In optical coherence tomography (OCT) biometry for IOL calculation, the Barrett Universal II formula consistently outperforms third-generation formulas for axial lengths outside the normal range. The key variable that Barrett Universal II additionally incorporates compared to SRK/T is:
23. In orthokeratology (Ortho-K) for myopia control in children, the mechanism by which overnight rigid contact lens wear reduces peripheral hyperopic defocus and thereby slows axial elongation is:
24. In transposition of astigmatic prescriptions, a cylinder of -2.00 DS / -1.50 DC × 90° transposed to positive cylinder form gives:
25. The minimum distance of distinct vision (MDDV) is abnormally close in which condition?
26. A child aged 8 years with high myopia (-10 DS) is found to have an axial length of 28 mm. The myopia is most likely classified as:
27. A patient with Leber's hereditary optic neuropathy (LHON) is found to have mitochondrial DNA mutation at position m.11778G>A. Regarding inheritance and genetic counseling, which statement is CORRECT?
28. A 16-year-old myope with increasing spectacle prescription is being considered for myopia control. Which intervention has the STRONGEST evidence for reducing myopia progression in children?
29. A 14-year-old student presents with progressive myopia that has increased by 1.5 D over the past year. His cycloplegic refraction is -5.00 D. Which strategy has the strongest current evidence for reducing the rate of myopia progression?
30. A patient's refraction is recorded as +3.00 / -2.00 × 90. The axis 90° means the minus cylinder axis is vertical. What type of astigmatism is this?
31. A patient's spectacle prescription is -3.00 DS/-1.50 DC × 90. Converting this to the cross-cylinder (power cross) notation, the power meridians are:
32. A child has hypermetropia of +6.00D. At what minimum age is the full correction most safely given without precipitating accommodative spasm, according to standard prescribing guidelines for high hypermetropia in young children?
33. A patient has a prescription of -3.00 / -1.00 × 180 in the right eye. In cross-cylinder notation, the two principal meridians and their powers are:
34. A spectacle lens prescription reads −3.00 DS / −1.50 DC × 90. When converted to the cross-cylinder notation, what is the power in the 90-degree meridian?
35. Which type of astigmatism has both focal lines on the same side (anterior or posterior) of the retina?
36. A patient's refraction is recorded as +1.50 DS / +1.50 DC × 180°. Transposing this prescription to its minus cylinder equivalent yields:
37. A patient's refraction is −3.00 DS / −2.00 DC × 90. What is the equivalent sphere (spherical equivalent) of this prescription?
38. A child wearing +4.00 D spectacles at the standard vertex distance of 12 mm. If contact lenses are prescribed, the required contact lens power will be:
39. Keratometry in a patient shows readings of 42 D at 90° and 46 D at 180°. What type and axis of astigmatism does this represent?
40. A patient with irregular astigmatism after corneal scarring achieves 6/60 with spectacles but improves to 6/9 with a rigid gas-permeable (RGP) contact lens. The mechanism by which RGP corrects irregular astigmatism (spectacles cannot) is:
41. A patient presents with -2.00 DS / -3.00 DC × 180. This prescription can be transposed to the following minus cylinder notation:
42. Duochrome (bichrome) test in refraction uses red and green filters. In a myopic patient whose red letters are clearer than green, the clinical interpretation and appropriate action is:
43. In LASIK, the flap creation with microkeratome followed by excimer laser ablation is designed to reshape the anterior corneal curvature. For myopia correction, the excimer laser (193 nm ArF) ablates tissue in which pattern?