Losing the ability to perceive clear outlines of objects and differentiate them from the background can have a huge impact on vision, even if visual acuity (VA) remains good. Decreased contrast sensitivity is “more linked to activities of daily living than visual acuity, including face expression perception, mobility, balance control, driving and reading”, says David Elliott FCOptom, Professor of Clinical Vision Science at the University of Bradford. 

Things like cooking and seeing kerbs can cause problems. “The bottom line is that the real world is not in high contrast,” says Kez Latham FCOptom, Professor of Optometry at Anglia Ruskin University. 

Many patients seen by Moad Zaidani MCOptom, an optometrist at Morgan Optometry in Oxfordshire, complain of difficulties reading a newspaper or telling apart medications. “I have spoken to people who avoid eating rice, because in most households the plates are white,” he adds.

Having reduced contrast sensitivity can be particularly frustrating for people with relatively good VA, adds Michael Crossland MCOptom, Principal Optometrist and Senior Research Fellow at Moorfields Eye Hospital, “as they can’t always understand why they can’t see to do things”.

Most patients who suffer from contrast sensitivity difficulties aren’t aware of the reason for their daily difficulties, Moad says. “Therefore, they will assume the cause for their issues is something else,” he adds. “Patients are very good at trying to adapt rather than seek help.”

Measuring contrast sensitivity aids understanding of visual function in a different context, Kez explains. “It can help explain a patient’s symptoms where sometimes visual acuity does not,” she says. “For example, multifocal contact lenses provide help with both distance sight and reading but if a patient feels [the lenses] aren’t quite good enough, measuring contrast sensitivity allows us to investigate why.”