A sight better than a poke in the eye…

Cross-section of a human eye/Claus Lunau

Even before Mr Darcy’s expressive admiration of Miss Bennet’s fine eyes, our appreciation of sight and the wondrous things we see – the faint rosy tinge of sunrise, the crisp, green brilliance of a freshly mown lawn or for the city dwellers among you, the varying shades of granite-grey – have shocked, stunned and awed us for centuries. So really, it should horrify you (my jaw certainly sagged the short distance between my head and the ground) to discover that approximately one in thirty people currently suffer from sight loss, with numbers only set to increase drastically, according to the RNIB.

Contrast between a normal healthy lens and a cloudy cataract lens/Nucleus Medical Art, JACOPIN

The human eye is akin to a camera. The cornea is made of transparent regenerating cells that forces light to converge on the inside of your eye. The pupil and iris act as a natural aperture mechanism by contracting and dilating to adjust to the level of light – the brighter your surroundings, the more your pupils contract, and vice versa. The light then reaches the retina, which is a photo receptor and analogous to camera film.

One of the main causes of sight loss is cataracts, which is a cloudiness that occurs in the normally transparent, crystalline lens of the eye. It obstructs the passage of light to the retina and as the cataract becomes more prominent, and thus more opaque, there is a noticeable loss of visual acuity. The most effective and common way to treat cataract is via surgical means. Cataract surgery involves a small incision in the cornea to allow access to the lens, which is then broken by a catheter through vibrations that prevent the surrounding tissue from being damaged. Once the cataract has been removed, an artificial intraocular lens (IOL) is placed in the capsular sac.

IOLs are not yet widely accepted in ophthalmic practice, since some require large surgical incisions to be inserted and are monofocal, which means that the patient will have clear vision – but only at a distance and will require further optical correction through the use of contact lenses or reading glasses.

However, Japanese researchers Masahiko Annaka and his team, along with their collaborators at the University of Copenhagen, have developed an injectable material that could replace the IOL in cataract surgery. Instead, a nanocomposite gel, which is an aqueous suspension of silica nanoparticles containing hydrophobically modified polyethylene glycol, is injected into the capsular bag that is left behind when the cataract is removed. As the fluid reaches body temperature, the polymer transforms into a gel that takes on the shape of a full-sized lens that completely fills the capsular sac, thus restoring clear vision without requiring complicated cataract surgery. This exciting field of research has great potential and ultimately, researchers hope to reproduce the effectiveness and full field of view of a young eye.