ABO NOCE Basic Opticianry General Practice 5 — Questions and Answers
Question 1: A lensometer power cross shows +2.00 at 180 and +4.00 at 090. The prescription in minus-cylinder form is:
- +4.00 -2.00 x 090 (Correct answer)
- +2.00 +2.00 x 180
- +4.00 -2.00 x 180
- +2.00 -2.00 x 090
Correct answer: +4.00 -2.00 x 090
In minus-cylinder form, the sphere equals the highest plus meridian (+4.00 at 090); cylinder = +2.00 − +4.00 = −2.00; axis = 090.
Question 2: Pantoscopic tilt is the angle formed between the lens plane and:
- The vertical plane (Correct answer)
- The horizontal plane
- The patient's optical axis
- The pupillary plane
Correct answer: The vertical plane
Pantoscopic tilt is measured from the vertical plane; standard tilt is 8–12° with the bottom of the lens closer to the face.
Question 3: A patient complains of a 'swim' or 'sway' effect with new progressive lenses. The most likely cause is:
- Peripheral distortion inherent in the progressive corridor design (Correct answer)
- Incorrect pupillary distance measurement
- Excessive pantoscopic tilt
- Wrong vertex distance
Correct answer: Peripheral distortion inherent in the progressive corridor design
Progressive lenses have unavoidable peripheral astigmatic distortion outside the central corridor, causing a swim sensation during adaptation.
Question 4: According to ANSI Z80.1, the allowable axis tolerance for a 2.00 D cylinder power is:
- ± 7° (Correct answer)
- ± 3°
- ± 5°
- ± 10°
Correct answer: ± 7°
ANSI Z80.1 specifies ±7° axis tolerance for cylinder powers between 1.25 D and 2.00 D.
Question 5: A patient inadvertently receives lenses with base-in prism. This will most likely cause the patient to experience:
- Eyestrain or diplopia as the eyes are forced to diverge more than normal (Correct answer)
- Difficulty converging at near
- Superior image displacement
- No noticeable symptoms
Correct answer: Eyestrain or diplopia as the eyes are forced to diverge more than normal
Base-in prism displaces images temporally (toward the apex), requiring the eyes to diverge; excess divergence demand causes eyestrain or diplopia.
Question 6: Which lens style is most appropriate for a patient who works at a computer 8 hours daily and also needs reading correction?
- Occupational (office) progressive lens (Correct answer)
- Standard distance progressive
- Flat-top bifocal
- Single-vision reading lens
Correct answer: Occupational (office) progressive lens
Occupational progressives are optimized for intermediate and near ranges, providing wider and more comfortable zones for computer and desk work.
Question 7: Effective power is clinically important when converting between spectacle and contact lens prescriptions because:
- Vertex distance changes alter the vergence power reaching the cornea (Correct answer)
- Contact lenses always require stronger powers
- Pupillary distance differs between the two modalities
- Contact lenses have a different refractive index
Correct answer: Vertex distance changes alter the vergence power reaching the cornea
When vertex distance changes, the effective vergence at the cornea changes, requiring a power compensation for prescriptions above ±4.00 D.
ABO NOCE Basic Opticianry General Practice 5
A lensometer power cross shows +2.00 at 180 and +4.00 at 090.
The prescription in minus-cylinder form is: