A firm from Google's parent company Alphabet has stopped working on one of its first projects - a contact lens designed to monitor blood sugar levels.

The device was supposed to assist people living with diabetes.

Verily had partnered with pharmaceutical giant Novartis to develop the lens in 2014.

In a blogpost, it said its measurements of the glucose levels found in tears, compared with the levels found in blood, were not close enough.

The lens consisted of a tiny wireless chip and glucose sensor, embedded between two layers of lens material.

"Our clinical work on the glucose-sensing lens demonstrated that there was insufficient consistency in our measurements of the correlation between tear glucose and blood glucose concentrations to support the requirements of a medical device," Verily said.

The firm said it had faced various challenges getting reliable readings from the eye, but added that it would continue to explore other uses for the Smart Lens technology - which include a lens to improve eyesight after surgery for cataracts.