Correct Eye Scope distance setting: which statement is true?

Correct Eye Scope distance setting: which statement is true?

• A. Contains +5.00 D lenses ACTUALLY separated by 95 mm; The ortho targets are separated by 87 mm.
• B. Contains +5.00 D lenses ACTUALLY separated by 87 mm; The ortho targets are separated by 68 mm.
• C. Lenses +5.00 D separated by 68 mm; ortho targets 87 mm.
• D. Lenses +4.00 D separated by 87 mm.

Answer: (B)

In this Eye Scope setup, the numbers matter because the device’s optical geometry must create the correct vergence and accommodation demands for the test. The two lenses in front of each eye provide a +5.00 D accommodation cue, which targets a near working distance of about 20 cm. To translate that demand into the proper binocular angle of convergence at the testing plane, the lenses are positioned a specific distance apart, and the ortho targets in front of the eyes are separated by a matching distance. The combination that matches the instrument’s geometry is lenses separated by 87 mm with the two ortho targets separated by 68 mm. This pairing ensures the visual axes and the disparity stimulus align with the +5.00 D accommodation cue at the intended distance, giving an accurate distance setting on the Eye Scope. Using a different lens separation or a different target separation would disrupt the intended vergence angle at the given accommodation demand, leading to inaccurate results.

In this Eye Scope setup, the numbers matter because the device’s optical geometry must create the correct vergence and accommodation demands for the test. The two lenses in front of each eye provide a +5.00 D accommodation cue, which targets a near working distance of about 20 cm. To translate that demand into the proper binocular angle of convergence at the testing plane, the lenses are positioned a specific distance apart, and the ortho targets in front of the eyes are separated by a matching distance.

The combination that matches the instrument’s geometry is lenses separated by 87 mm with the two ortho targets separated by 68 mm. This pairing ensures the visual axes and the disparity stimulus align with the +5.00 D accommodation cue at the intended distance, giving an accurate distance setting on the Eye Scope.

Using a different lens separation or a different target separation would disrupt the intended vergence angle at the given accommodation demand, leading to inaccurate results.