Vertical diplopia on downgaze with bifocals.

Area of Science:

• Optometry and Vision Science
• Ophthalmic Optics
• Human Perception

Background:

• Bifocal lenses are commonly prescribed to correct presbyopia.
• Patients sometimes report a visual phenomenon known as

Purpose of the Study:

• To determine if patients experience "jump" or diplopia at the dividing line of bifocal lenses.
• To investigate if leading questions influence the perception of bifocal "jump".

Main Methods:

• Ten subjects were asked open-ended questions, and ten were asked closed-ended questions about bifocal "jump".
• Six types of bifocal lenses and three eye movement conditions were tested.

Main Results:

• No effects other than near blur were observed with saccadic eye movements.
• Vertical diplopia was frequently reported with round 38 segment bifocals during pursuit movements when open-ended questions were used.
• When leading, closed-ended questions were posed, all subjects reported "jump" with 38 segment bifocals and 50% with C28 segment bifocals during pursuit movements.

Conclusions:

• Bifocal "jump" is often perceived as diplopia, particularly when subjects are prompted with open-ended questions.
• The perception of "jump" and diplopia is influenced by the lens design (e.g., round 38 vs. C28 segments) and questioning technique.
• Diplopia, rather than "jump", may be more relevant in understanding patient adaptation to bifocal lenses.