Bifocals and trifocals result in a more complex lens profile, compounding multiple surfaces. Bifocals are eyeglasses with two distinct optical powers. The American scientist Benjamin Franklin, who suffered from both myopia and presbyopia, invented bifocals. Manual adjustment is more cumbersome than bifocals or similar lenses. Gradients should not be confused with bifocals and progressive lenses. She says that the glasses are not Mulwray's, as he did not wear bifocals. At first, Hakimi offered glasses for $8/pair ($12 for bifocals), which far undersold any competitors. Archbold, like Franklin, was balding and required the use of bifocals and cane. Bifocals can cause headaches and even dizziness in some users. Benjamin Franklin is generally credited with the invention of bifocals. Research continues in an attempt to eliminate the limited field of vision in current bifocals.