The ophthalmoscope is the most elegant, powerful and gentle diagnostic tool ever invented. It allows the observer to look inside the eye through the pupil, like looking through a window. Delicate retinal vessels and the optic nerve are seen in exquisite detail, magnified 15 times by the patient’s own eye.
Apart from eye diseases such as cataract and glaucoma, many diseases of the body reveal their presence with an ophthalmoscope. Microaneurysms of diabetes, some as small as 30 micrometres across, are clearly seen. Swelling of the optic nerve (papilloedema) implies pressure on the brain perhaps from a tumour or an abscess. Glittering crystals of cholesterol point to a diseased heart valve or carotid artery. Tiny haemorrhages may result from diseases as diverse as high blood pressure, bloodstream infection, leukaemia, or heart surgery complicated by debris entering the circulation - cautioning the surgeon to review the technique. In tropical Africa cerebral malaria kills one million children a year; an ophthalmoscope may give an immediate life-saving diagnosis. The instrument is equally useful for veterinary practitioners.
When Helmholtz announced his invention of the ophthalmoscope in December 1850, he gave the healing professions a priceless gift which he refused to patent.