The Field Representative's Manual instructs interviewers to probe to emphasize "even when wearing glasses" if respondents indicate they may have trouble seeing when they do not wear their glasses. Further, if respondents state they have they do not wear glasses when asked the question, then interviewers should repeat they question, but exclude the phrase "even when wearing glasses."

These include:

• CONTACTS Uses contact lenses, 1971, 1979-1981, 1984

• GLASSES Uses eyeglasses (prescription or non-prescription), 1971, 1979-1981, 1984

• GLASSESRX Uses prescription eyeglasses 1984 only

• LENSIMPLANT Has a lens implant. 1984 only

• VDIFAMOUNT Amount of vision trouble, 1984 only

• VDIFPEPL2FT Sees enough to recognize people w/in 2 feet, 1984 only

• VDIFSEEFREND Sees enough to recognize friend across street, 1984 only

• VDIFREADNEWS Sees enough to read newspaper, 1984 only

• VDIFSEETV Sees enough to watch TV, 1984 only

• VDIFSTEPCURB Sees enough to step off curb or step, 1984 only

• VDIFREADMAGL Uses magnifying glass to read, 1984 only