As an individual ages, their eye is less able to accommodate or bend the natural lens to focus on objects relatively nearer to the observer. This condition is known as presbyopia, says the company in its filing with the patent office. Johnson and Johnson has its multifocal lenses sold under its contact lenses brand Acuvue, to address the issue of presbyopia.
The patent office has earlier raised objections including that the first claim of the company do not sufficiently define the invention and there are many features in principle claim which are unwarranted and others.
However, on finding that the company's agent has complied the objections by submitting revised claims, Parijat Saurabh, deputy controller of patents and designs, of patent office, Kolkata, issued an order granting application for patent.
According to the specification the company filed with the patent office, the invention provides contact lenses that provide correction for presbyopia using multifocal designs that are scaled to an individual, or group of individuals, based on both pupil size and the Stiles-Crawf 3rd effect.
It says that the pupil size of the individuals vary with age, luminance and distance frmo the eye to the object being viewed and as the luminance increases, the size of pupil has to be decreased. However, in aged individual, the response of the pupils to change when it comes against luminance are decreased.
Some conventional multifocal contact lenses do not take the pupil size into account and will be less efficeint in providing light to the viewer in all conditions. According to the Stiles-Crawford effect, the intensity of the response of light is higher in the centre of the pupillary aperture and the response will decrease towards the edges.
"Therefore, the best visual result for a lens cannot be obtained by merely matching the size of the optical zones of a multifocal lens by taking into account only pupil size. Rather, the design must take into account both the pupil size and the Stiles-Crawford Effect," said the company.