As well as right angles, there are also acute and obtuse angles. An acute angle is very easy to spot; it is any angle smaller than a right angle (0-89 degrees – ah, cute!).

An acute angle-closure glaucoma attack is one of the few true ophthalmic emergencies. Presenting symptoms include severe eye pain or pressure sensation, redness, blurred vision, seeing haloes ...

Narrow angle glaucoma can be acute or chronic. The acute form requires immediate medical attention. For both types, early diagnosis and treatment can help prevent vision loss.

As well as right angles, there are also acute and obtuse angles. An acute angle is very easy to spot; it is any angle smaller than a right angle (0-89 degrees – ah, cute!).