Developing special glasses for patients with keratoconus

Brief lay background

Keratoconus is a progressive ectatic condition where the cornea thins and becomes distorted. This distortion is mainly manifested as irregular astigmatism, in which an irregular curve in the cornea causes blurred asymmetric vision.

The traditional way of correcting vision is to use a combination of a spherical lens to correct short or longsightedness and a cylindrical lens to correct astigmatism.

Although it has been two centuries since astigmatism was first described, it was only recently that non-orthogonal astigmatism was recognised. This is more commonly seen in keratoconus.

What problem/knowledge gap does it help address

This project addresses an important unmet need in enabling advanced keratoconus patients to maintain their independence when they cannot use their usual visual aids. Keratoconus patients commonly use contact lenses to provide reasonable refractive correction, and while these aids are usually effective, they cannot be worn continuously, and have to be removed for example during sleeping hours.

Some patients also suffer additional conditions, such as allergy to disinfecting solutions or dry eye syndrome, which would make wearing of contact lenses uncomfortable. In these cases, the uncorrected refractive errors caused by keratoconus can be serious enough to cause severe loss of vision and can cause safety risks while carrying out common house activities, and more seriously during emergencies.

In these cases, prescription glasses could be used, but their effectiveness is severely reduced by their current design which ignores the non-orthogonal nature of astigmatism caused by keratoconus.

Aim of the research project

To develop spectacles to provide better acuity for keratoconus patients.

Key procedures/objectives

1. Assess the final spectacle lens design with a hospital clinic.
2. Record patient reactions and feedback using Quality of Life questionnaires to improve the final product.
3. Investigate differing stages of keratoconus to understand whether those with longstanding conditions benefit from correction as much as the newly diagnosed.

Potential impact on people with sight loss

Keratoconus patients are commonly fitted with contact lenses to correct corneal irregularities and provide them with good visual acuity. However, as contact lenses cannot be worn all the time, patients are rendered partially sighted when they are removed.

This causes significant safety risks and disruption to their quality of life. For this reason, there is a need for spectacles that can be used at these times, and which can offer clear enough vision. However, a major obstacle is the fact that keratoconus causes nonorthogonal astigmatism which cannot be quantified using current technology.

There is also no commercial route to manufacture non-orthogonal spectacle lenses. The proposed research attempts to address these important technical challenges and further determine whether keratoconus patients could benefit from spectacles in the same way as patients with regular spectacle refraction.