The complaint of blurred vision is the most common visual symptom. In order to see an object clearly, its image must pass clearly through multiple structures of the eye. The lens of the eye must refract the image seen so that it falls on the retinal nerve cells surrounding the back of the eye and then be transmitted along the optic nerves and optic tracts in the brain to the vision center of the brain in the occipital lobes located in the back of the brain where the image is recognized and interpreted.
An image must pass multiple structures of the eye as well as the optic nerve tract until it reaches the visual cortex of the brain. As a result, there are many causes of blurred vision. Any abnormalities in function or inflammation of the conjunctiva, iris, lens, vitreous humor (a jelly-like substance which fills the globe of the eye) and retina can cause blurred vision. Two very common causes of blurred vision are changes of aging affecting the refraction function of the lens and cataract formation on the lens. Other causes of blurred vision are: glaucoma, which is an increase in pressure in the eye; diabetes with high blood sugar causing swelling of the lens; or damage to the arterial supply to the retinal nerve cells from diabetic retinopathy. Long-standing uncontrolled hypertension can cause hypertensive retinopathy which also can damage the small arteries that supply the retinal nerve cells. Age-related degeneration of the most sensitive retinal nerve area for vision (the macula) can cause blurred vision. Unilateral or one-sided blurred vision is a much more worrisome symptom than bilateral blurred vision as it is more suggestive of a serious problem within the eye, retina or brain which would require rapid evaluation and treatment.
Common causes of unilateral painless blurred vision are cataracts, glaucoma, hemorrhage into or detachment of the vitreous, retinal detachment, and brain stroke or a brain tumor causing increased intracranial pressure and/or compression of any portion of the optic pathway from the back of the eye to the visual center of the brain. The most common brain tumors are malignant glioblastomas and meningiomas, most of which are benign. Meningiomas usually have a slow rate of the growth but often cause headaches because of increased intra-cranial pressure. Pressure from the tumor on any portion of the optic tracts often causes defects in the visual field or blurred vision depending on the location of the pressure caused by the meningioma.
Blurred vision medical expert witness specialties include ophthalmology, retina-vitreous ophthalmology, neuro ophthalmology, endocrinology, emergency medicine, nephrology, internal medicine, and neurosurgery.