Contact lens wearers must always replace their lenses in accordance with guidelines, Johnson & Johnson says.
The manufacturer of Vistakon contacts conducted research and found that wearers of monthly replacement contacts find weeks three and four are often less comfortable than weeks one and two.
The study involved 20 different types of lens and discovered that 71 per cent of people who wear monthly silicone hydrogel types and 68 per cent of those with hydrogel report a drop in comfort levels as the month goes on.
Some 95 per cent said weeks three and four were when the discomfort becomes noticeable.
It emphasises the importance of changing contact lenses when guided to, said Johnson & Johnson.
Sheila Hickson-Curran, a former director of medical affairs for the Vistakon division of the company, said: "It is quite simple ... by not following instructions on proper wear and care, contact lens wearers are more likely to experience discomfort and may put themselves at greater risk for infection or other serious complications."
Other brands of contact lens that may be suitable for wearers include 1 Day Acuvue and Freshlook.
by Emily Tait