Failing vision means that the sight, as measured by the standard test type, is worsening. The patient might say "I can't see so well doctor" or they might feel that their spectacles need changing. Some patients might not notice visual loss, especially if it is in one eye. Sometimes, more specific symptoms are given; the vision might be blurred, for example in a patient with cataract, or objects might appear distorted or straight lines bent if there is disease of the macular region of the retina. Disease of the macular can also make objects look larger or smaller. Double vision is an important symptom because it can be the result of a cranial nerve palsy,but if monocular, it could be caused by cataract. Patients quite often complain of floating black spots. If these move slowly with eye movement, they might be caused by some disturbance of the vitreous gel in the centre of the eye. If they are accompanied by seeing flashing lights, the possibility of damage to the retina needs to be kept in mind. "Vitreous floaters" are common and in most instances are of little pathological significance. Patients quite often notice haloes around lights and, although this is typical of an attack of acute glaucoma, haloes are also seen by patients with cataracts. Like many such symptoms, they are best not asked for specifically. The question "do you ever see haloes?" is likely to be followed by the answer "yes". Night blindness is another such symptom. No one can see too well in the dark,but if a patient has noticed a definite worsening of his or her ability to see in dim light, an inherited retinal degeneration, such as retinitis pigmentosa, might be the cause.
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