34 Vision Problems and Other Common Eye Problems
Patients may think that discomfort in the eyes or noticeable redness is serious. However, visual symptoms are always more serious than nonvisual ones. Blurred vision caused by refractive error is the most common visual complaint, but it is often the most difficult visual symptom to evaluate. Other common vision problems are diplopia, unilateral photopsia (floaters, stars, light flashes) usually due to posterior vitreous detachment (PVD), and visual blurring associated with pain or eye soreness. A correct diagnosis requires knowing the patient’s age and deciding whether the symptoms are unilateral or bilateral, onset is sudden or gradual, and symptoms are constant or intermittent. The prevalence of severe visual impairment is increased in elderly patients. In all instances, visual acuity must be determined with the use of a Snellen chart.
The most common causes of visual symptoms include refractive errors, posterior vitreous detachment (usually due to contraction of the vitreous), migraine, acute angle-closure glaucoma, cataracts, dry eyes, drug side effects, and transient ischemic attacks (TIAs).
In young patients the most common cause of visual blurring is refractive error. The two most frequent refractive errors are myopia (nearsightedness) in teenagers and presbyopia (loss of accommodation) in patients at about age 40 years, when glasses become necessary for reading. Scintillating scotoma, another common visual problem in adolescents and adults, is experienced by patients with migraine as a prodrome to their headaches. Some patients note only the scintillating scotoma but do not experience a headache, a condition known as ophthalmic migraine or migraine sans migraine but currently called migraine aura without headache.
The remainder of the common visual symptoms and causes of vision loss listed in the introduction generally occur in older adults. Cataracts, glaucoma, floaters, light flashes, senile macular degeneration, diabetic retinopathy, TIA, drug side effects, and dry eyes occur almost exclusively in elderly patients. Older women often have dry eyes, which may result in visual blurring sometimes associated with a sense of grittiness and warmth in the eyes. In elderly patients a sudden onset of painless unilateral blurred vision often associated with a relative central scotoma and visual distortion suggests senile macular degeneration, the most common cause of blindness after age 55 years.
Two neuro-ophthalmologic vascular emergencies occur in elderly patients: temporal arteritis and third-nerve palsy. Temporal arteritis presents as a transient (in some cases progressive) unilateral visual loss often associated with visual field defects. Temporal arteritis is twice as common in elderly women as in elderly men. Patients with third-nerve palsy present with a sudden onset of diplopia with pain around the eye or diffusely in the head. Because in approximately 20% of these elderly patients an aneurysm is causing third-nerve palsy, their cases must be investigated promptly.
Monocular blurring, particularly of sudden onset, is more likely to be serious and of ocular origin. If the blurring is binocular and has occurred gradually over months in an otherwise healthy individual, a refractive error is most likely.
In an elderly patient, when primarily distant vision is blurred, the cause is most often cataracts, but if near vision is mainly affected, a retinal circulatory disturbance or macular degeneration should be suspected. Monocular blurring of sudden origin (days or weeks) is generally not a refractive error. In some patients, monocular blurring due to a refractive error may be long-standing but only recently noted.
Episodic blurring is virtually never caused by a refractive error. In older adults it can result from glaucoma, multiple sclerosis (MS), or TIAs. Brief episodes of blurred vision or loss of vision, usually monocular but occasionally binocular, are typically caused by transient impairment of retinal circulation resulting from atherosclerotic emboli from the carotid circulation or heart, carotid insufficiency, or vertebrobasilar insufficiency. Patients with the latter condition may have transient diplopia, blurring accompanied by dizziness, or both. Episodic blurring due to carotid insufficiency is often referred to as amaurosis fugax. Because visual loss becomes permanent in 11 % of these patients, they should be investigated promptly.
Several types of visual auras are experienced by patients with migraine. Scotomas are areas of indistinct or totally obscured vision. A negative scotoma is a circumscribed, obscured region in the visual field that appears translucent or as a dark or shimmering area. Negative scotomas most often begin in the central region of the visual field and then expand across the visual field, sometimes encompassing part of the right or left field. Homonymous hemianopsia may be present, or the vision may be totally obscured. Vision may also be obscured by positive scotomas, which are often described as bright, shimmering, shooting, or scintillating lights. These also occur initially in the center of the visual field and then expand to fill the entire visual field.
When transient blurring (with associated pain and redness) occurs unilaterally in older patients, acute angle-closure glaucoma should be suspected. The sudden loss of central vision in one eye and ocular pain without redness suggest optic neuritis. Fifty percent of patients with optic neuritis eventually have MS. Optic neuritis preceding MS is virtually always unilateral, and the blurring may last several days. Ischemic neuropathy, often due to giant-cell arteritis, usually manifests as variable blurring and superior or inferior field defects. Visual loss is usually permanent.
Patients often confuse diplopia (double vision) with blurred vision. Patients with diplopia see two separate objects either side by side or one above the other. Most diplopia in adults is caused by paralysis or weakness in one or more of the extraocular muscles. This paralysis may be caused by trauma, cerebrovascular lesions, MS, thyroid disease, myasthenia gravis, or brain tumors. Diplopia due to strabismus is most common in children and leads to eyes that fail to coordinate. Patients may have intermittent exotropia or esotropia. Young children with these symptoms usually suppress one image and therefore do not complain of double vision. Diplopia due to strabismus is more common in adults when the angle of their squint changes.
Diplopia may be monocular or binocular as well as constant or intermittent. Patients with monocular diplopia experience double vision with one eye occluded. It is most often the result of lens opacities. A slightly dislocated lens associated with trauma or Marfan’s syndrome is a rare cause of monocular diplopia. In an otherwise healthy individual, monocular diplopia suggests that the hysteria is causing diplopia.
Constant binocular diplopia may be caused by head trauma or pathology involving the extraocular muscles or their cranial nerves. If the patient has total third-nerve palsy and the pupil is involved, an aneurysm is probable.
After blurring, the next most common visual complaints are spots floating in the visual field and light flashes. Floaters and flashes are caused by contraction of the vitreous and occur in middle-aged and older patients. Light flashes are usually noted in the temporal field, particularly when the patient is in the dark or in poorly illuminated areas. Flashes are caused by the vitreous shrinking away from the retina and thus stimulating it. Vitreous floaters are produced when the vitreous pulls away from the retina, thus detaching particles suspended in the vitreous. Patients describe these as black or grey spots in the visual field when they look at a bright background such as the sky or a light-colored wall. Neither light flashes nor vitreous floaters are serious, but they should be investigated by an ophthalmologist because they may signal retinal detachment. Likewise, if a peripheral field defect occurs after the patient experiences light flashes and a shower of floaters, retinal detachment should be suspected, and the patient should be examined by an ophthalmologist.
Halos around lights are a common symptom in patients with acute angle-closure glaucoma. The rapid development of a relative central scotoma associated with visual distortion is often caused by senile macular degeneration.
Red eye may be produced by subconjunctival hemorrhage, episcleritis, scleritis, pterygium acute angle-closure glaucoma, superficial keratitis, acute anterior uveitis, and, most frequently, conjunctivitis.
Viral conjunctivitis which usually begins bilaterally is the most common cause of red eye. There is conjunctival hyperemia, tearing, and a watery discharge. It may start in one eye but quickly spread to the other, may be highly contagious, and may be associated with an upper respiratory infection. Bacterial conjunctivitis has a sudden onset in one eye but usually spreads to the other within 2 days. There is much tearing and usually a mucopurulent discharge, causing matting of the lids that is most prominent on awakening. Patient report of eyes being “glued shut” upon awakening has been associated with an odds ratio of 15:1 for a positive bacterial culture result.
Allergic conjunctivitis, which usually begins bilaterally may be the only manifestation of an allergic disorder, but there are usually other manifestations of allergy, such as sneezing, blepharitis, and itching of the eyes and/or roof of the mouth. Seasonal allergic conjunctivitis is the most common form of allergic conjunctivitis and is related to the occurrence of airborne pollens from sources such as trees, grasses, and weeds, including ragweed. There is usually tearing; burning; itchy eyes; sneezing and rhinorrhea; and a thin, watery discharge. Perennial allergic conjunctivitis causes similar symptoms that often occur year round. It is usually caused by household allergens such as animal dander, dust, and dust mites. If the onset of symptoms corresponds to turning on of forced-air heating, dust mites are often the culprit. Vernal keratoconjunctivitis is seasonal, occurs in males between 3 and 20 years of age, and lasts up to 10 years. Contact ophthalmic conjunctivitis involves the ocular surface and the eyelids. It is a form of conjunctivitis medicamentosa due to the use of ophthalmic medications frequently started to relieve seasonal or perennial allergic eye symptoms. Subconjunctival hemorrhage may be caused by a Valsalva maneuver, induced by lifting a heavy object or a coughing spell and rarely by trichinosis.
Loss of vision is more common in the elderly. It is usually caused by age-related macular degeneration, glaucoma, cataracts, or diabetic retinopathy. Although these conditions may be asymptomatic, their usual presenting symptoms are as follows: macular degeneration: blurred vision, central scotomata, trouble reading; glaucoma: visual field loss’ cataracts: glare, halo, blurred vision, monocular diplopia; and diabetic retinopathy: visual field loss, blurred vision, impaired night vision. All patients with loss of vision should be referred to an ophthalmologist for evaluation.