Diabetes mellitus is a significant risk factor for the development of cataracts, the second most common ocular complication in this patient population. Various visual disturbances may be noted in diabetic cataract, and the diagnosis requires a slit-lamp examination.
Cataracts are considered to be one of the earliest complications of diabetes mellitus, and they are confirmed as the most common cause of visual impairment in older age diabetics  . Some studies report that female patients are more likely to develop a cataract, but the observed gender predilection is yet to be confirmed . Other studies, however, report that poor glycemic control greatly contributes to the development of cataracts, particularly ketoacidosis, which can directly promote corneal damage by reducing the number of viable antioxidant molecules . Compared to classical senile cataracts that have a slow development over a period of years , diabetic forms seem to have an earlier onset and a more progressive clinical course , with most important features being the development of posterior, anterior, subcapsular or cortical opacities of the cornea . These pathological changes can affect only one eye, but cases of bilateral diabetic cataracts have been documented . Loss of contrast, a necessity for more illumination to maintain adequate vision, issues with distinguishing dark blue from black color, as well as halos around lights, are most common complaints . In severe cases, painless blurring and severe vision impairment can occur, and it is not uncommon for cataracts to cause blindness   . Swelling of the cataract may occur in rare cases and cause pain provoked by secondary closed-angle glaucoma, due to mechanical compression of the iris and the trabecular meshwork .
Cataracts can be confirmed by a slit-lamp examination that will identify yellow, gray or white opacities in the lens . Other signs may include recurrent corneal erosions and ulcerations, increased autofluorescence and reduced corneal sensitivity, while the examination of the red reflex at a distance of around 30 cm from the affected eye through the use of an ophthalmoscope will confirm the presence of corneal opacities  . Pupillary dilation before the eye examination is advocated, to obtain a better view of the entire apparatus and possibly detect other pathological changes, such as diabetic retinopathy . Assessment of visual acuity, gonioscopy, funduscopy, and tonometry are other tests that can be employed, so that the exact type and location of the cataract may be determined . In addition to physical examination, a detailed laboratory workup should be carried out in all patients with an undisclosed cause of cataract development, comprising serum glucose levels and hemoglobin A1C (HbA1c). Obtaining a proper family history that will potentially determine the presence of diabetes mellitus within the family or close relatives is also an important step when assessing patients with cataracts. Moreover, patients should be asked whether they exhibit some of the more common symptoms of diabetes (polyuria, polydipsia or polyphagia), the primary reason being the detection of diabetes.