Ophthalmology is a medically and surgically oriented specialty that is concerned with diseases of the eye, eyelids and muscles responsible for eye movements. It involves the medical and surgical treatment of diseases such as glaucoma, cataracts, retinal detachment, squints or blocked tear ducts. With the aid of ophthalmic examinations, ophthalmology can detect certain diseases and monitor their subsequent development for medical consequences. Examples include cases of high blood pressure or diabetes. Visual field examinations can also reveal abnormalities associated with neurological diseases. This is particularly the case with brain tumours.