Changes in the lens proteins (crystallins) affect how the lens refracts light and reduce its clarity, therefore decreasing visual acuity. Chemical modification of these lens proteins leads to the change in lens colour. New cortical fibres are produced concentrically and lead to thickening and hardening of the lens in nuclear sclerosis, which often appears yellow and can increase the focusing power of the natural lens. Increasing myopia can also be evidence of a progressing nuclear sclerotic cataract. In an experimental model, oxidative stress contributed to cataract formation, causing a decrease in the level of adenosine triphosphate and glutathione disulfideCortical cataracts are most often seen as whitish spokes peripherally in the lens, separated by fluid. Vacuoles and water clefts can also be seen in these lenses. Posterior sub-capsular cataracts are due to the migration and enlargement of lens epithelial cells (Wedl cells) posteriorly. Diabetes mellitus is a major factor in the formation of this type of cataract. Osmotic stress due to sorbitol accumulation has been linked with sudden worsening in patients with uncontrolled hyperglycaemia. However, research has also found that when sorbitol dehydrogenase was blocked, preventing sorbitol accumulation, oxidative stress was connected with slow-developing cataracts. [5]