Ophthalmology is the practice of medical and surgical care that deals with the diagnosis, treatment and prevention of diseases of the eye and visual system. It is used to treat a range of eye conditions such as corneal pathology (diseases of the cornea); cataracts (loss of transparency in the eye lenses); glaucoma (abnormally high pressure inside the eyes); squints (where there is a problem with the alignment of the eyes); retinal problems (e.g. oedema within, bleeding, tears or detachment of the retina, the back inner surface of the eye that receives light); intraocular inflammation (inflammation within the eye); eye-related neurological problems. Ophthalmology can also help to identify underlying causes of diseases that affect the eyes e.g. diabetes and hypertension. Ophthalmology is carried out by physicians (ophthalmologists) specializing in this field, and are the only practitioners medically trained to diagnose and treat all eye and visual problems. Ophthalmic patients comprise from every age group, from premature babies to the elderly members of the population. Usually, individuals can only gain access to an ophthalmologist through a referral by a family doctor, pediatrician, or emergency room doctor.