While many general diseases cannot be diagnosed by examining the eye in isolation, others may be detected before any symptoms have been experienced.
The case of a 29 year-old lady whom I saw recently illustrates this point. She had been experiencing blurred distance vision, especially in dull illumination.
The initial diagnosis of myopia (shortsightedness) appeared to explain the symptoms. However, when the inside of the eye was checked with sophisticated instrumentation, the optic nerve, which connects the eye to the brain, was obviously swollen and surrounded by haemorrhages. This appearance indicated a condition called papilloedema, which occurs when an increase in cerebrospinal fluid pressure in the brain has a “flow-on effect” on the optic nerve.
While this appearance does not provide a full diagnosis, it does raise the suspicion of a brain tumour or other brain abnormality. The patient was referred to her GP who ordered a CT scan. This confirmed that the patient did have a brain tumour. The patient was referred to a neurosurgeon who performed brain surgery.
In this case early intervention was possible purely because of an eye examination as no other symptoms were being experienced. However, it is important to emphasise that many brain tumours do not affect the visual pathway and cannot be diagnosed by an eye examination.