5.1 Background

The lens is composed of a single layer of epithelial cells attached to a basement membrane (lens capsule). The epithelial cells differentiate into lens fibres, after which proliferation ceases and there is terminal differentiation with a restriction of protein synthesis with the formation of crystallins. With aging of the cell protein synthesis and proteolysis is terminated, although deposition of new cells continues at the periphery of the lens.

The essential properties of the lens are its transparency and ability to focus light. A cataract is defined as opacity within the lens that interferes with vision. Cataract can occur in children, or be associated with inherited disease, but the vast majority are age-related. Age-related cataract has enormous economic and public health significance and it is the major treatable cause of blindness worldwide. Even in developed countries cataract is the most common reason for ophthalmic referral. Surgical removal of the lens with implantation or an artificial lens within the eye is the treatment of choice. Unfortunately, although this treatment is cheap and cost effective, delivery to the people most in need is difficult and the number of people blind with cataract continues to rise. In addition, posterior capsular opacification is a significant cause for late visual loss and a further drain on resources. Reducing the growing backlog of patients with cataract will require radical changes in the delivery of surgery. The safety and efficacy of these changes must be proven.

There is no validated medical treatment for cataract. Although prevention or a cure may not be possible in the foreseeable future, an intervention that delayed the onset of cataract would have a major impact. Any approach would almost certainly depend on an understanding of the molecular processes that occur in the normal lens and alterations associated with cataractogenesis.

Presbyopia is the loss of accommodation of the lens, which is the ability to change focus from distance to near. An understanding of how the physical properties of the lens and its support structures change with age may lead to developments that delay or prevent the onset of presbyopia. In addition, the artificial lens that is implanted following cataract extraction is typically a monofocal lens, and glasses are normally required for reading. The restoration of a full range of focus following cataract extraction would be a major advance. Multifocal intraocular lenses are available but not widely accepted. Intraocular lens implants that can accommodate are being developed, although they have not been perfected and further research is required.

The projects listed below anticipate that an understanding of the basic mechanisms of lens physiology will provide a framework to delay the processes of ageing and subvert the complications of cataract surgery. However, it is recognised that the developing these advances to clinical practice may be delayed. Therefore, for pragmatic reasons, consideration is also given for service provision and new technologies that may provide more immediate relief for affected patients.

   5.2 Research Potential