Cataracts cloud the natural lens and eventually make sufferers blind. Every year over 10 million people have surgery to replace their lenses as a result of cataracts, and the number of cases is increasing by approximately 15% each year, in step with ageing populations. In a simple, 20-minute outpatient surgery, the original lens is replaced by an intraocular lens (IOL) made of plastic, and sight is almost miraculously restored. However, unlike the natural lens, the IOL cannot be voluntarily brought into focus; while patients can see perfectly in the distance, they must wear glasses to read. The ‘holy grail’ of IOL development has always been a lens that can both restore sight and allow the patient to focus without glasses: an accommodating intraocular lens (AIOL).
Presbyopia is a condition in which billions of people lose their ability to focus on nearby objects (such as computer screens or newspapers). Mostsufferers are over the age of 40 years. With cataracts, lens replacement is required to restore sight; with presbyopia, lens replacement is an option rather than a necessity. For cataracts, the modern-day monofocal IOL is a simple and safe solution to the catastrophe of blindness; an IOL that accommodates would be a wonderful bonus. For presbyopes, however, there is absolutely no point in removing a healthy but inadequate natural lens by clear lens extraction if it cannot be replaced by a far superior IOL that accommodates. A truly accommodating IOL would improve treatment for cataracts and offer the possibility of restoring focal accommodation to presbyopes. Once an AIOL has been proved to work in cataract patients, the potential for treating presbyopes will represent a potentially vast unexploited opportunity in the healthcare market. Consequently, AIOLs are being pursued intensely by both academia and industry.
One approach to ‘accommodation’ taken by some companies is the multifocal lens. However, this does not truly accommodate, but rather presents the eye with multiple focused images from various distances simultaneously. Multifocal IOLs share several advantages with standard monofocal IOLs, such as fixed positioning in the eye and alignment using proven surgical procedures. However, multifocal IOLs improve uncorrected near vision at the expense of overall sharpness, and also significantly reduce contrast.
In order to restore sight and allow patients to focus without glasses, the lens has to move or change its refraction index. Most of the designs to date have achieved some limited lens movement along the optical axis, allowing focal change over a short distance – perhaps 0.5–1 diopter (D). The AkkoLens solves this problem with a unique design that magnifies the focal change by moving perpendicularly to the optical axis, resulting in true and clear spectacle-free vision (see Figure 1).