- Dacryocystitis is an inflammation of the tear drainage sac caused by an infection. It usually affects one eye only and may become a chronic disorder. It is found most commonly in adult females. Dacryocystitis may be caused congenitally, from a blockage or obstruction of the tear duct, or from a trauma or injury. A resulting infection is caused most often by such bacteria as Staphylococcus aureus and betahemolytic Streptococcus, as well as by such fungi as Candida albicans. Symptoms may include constant tearing, swelling, discharge, and eye tenderness. A culture of the discharge will identify the infecting agent. The condition can be difficult to treat because the sac is located deep within the tissues surrounding the eye. Also, the condition can be hard to pinpoint and sometimes remains undetected for long periods, leading to scarring and tearing problems. Dacryocystitis is usually treated with warm compresses and topical or systemic antibiotics. Blocked nasolacrimal ducts of infants may be massaged to encourage dilation; but, if the duct fails to open, it may require surgical dilation. Occasionally, the condition produces an abscess, which has to be drained by an ophthalmologist.
Dermatochalasis is an age-related drooping of the skin in the upper and lower eyelid. In the upper eyelid, this condition may cause the eyelid skin to sag over the eyelashes and interfere with vision. The lower eyelid may form what is commonly known as “bags under the eyes”. The condition usually affects both eyes. A surgical procedure called blepharoplasty is commonly performed to remove excess skin, muscle, and fat from the eyelid. It is generally a safe procedure and performed on an outpatient basis and should not interfere with vision. Any swelling, tenderness, or pain afterwards should subside in two to four weeks. Mild cases of dermatochalasis are sometimes treated with laser surgery. In this procedure, skin and muscle are shrunk and tightened rather than removed. Whether this procedure is covered by insurance will depend on whether the condition impairs vision. Most insurers will not cover surgery done for cosmetic reasons, but will if the eyesight is hampered.
- Diabetic Retinopathy
- is a serious eye complication stemming from diabetes. (See separately.)
Diopter is a unit of measurement for the power of a lens. It measures the extent light rays will bend as they pass through the lens. Diopters are written in prescriptions as OD or OS followed by a plus or minus sign and a number. The OD stands for the Latin oculus dexter, or right eye. The OS stands for oculus sinister, or left eye. The plus signs indicate convex or farsighted lenses. Minus signs stand for concave or nearsighted lenses. A +3.00 prescription calls for a 3 diopter convex lens for a farsighted eye. A-1.5 prescription requires a 1-1/2 diopter concave lens for a nearsighted eye. The stronger the lens is, the higher the number.Prescriptions to correct astigmatism employ cylindrical lenses that are often incorporated into a convex or concave lens to curve it more in one direction. Astigmatism prescriptions indicate the diopter degree of nearsightedness or farsightedness, plus the word “axis” and a number from 1 to 180. The axis number refers to the number of degrees on a protractor and determines to which degree the cylindrical lens must be oriented. The prescription -3.25-2.00 axis 95, calls for 3-1/4 diopters of nearsightedness with 2 diopters of astigmatism. The axis 95 indicates the degree at which the cylindrical lens must be oriented. In this case, 95 degrees.
Diplopia is a term for double vision and is often confused with blurred vision when cited as a patient complaint. Blurred vision is a cloudy or hazy image, but diplopia is the sighting of two separate images at the same time. Diplopia may be constant or intermittent and binocular or monocular. Monocular diplopia occurs if the double image persists when one eye is closed. This is a common form of diplopia and often caused by cataracts. Binocular diplopia occurs when the diplopia is corrected when one eye is closed. Diplopia may go unnoticed in adults or children due to poor general vision or suppression of image. Children often accommodate to the double image by suppressing the image of one eye, a condition called amblyopia. This condition may lead to vision loss. Diplopia is a serious symptom and requires testing of the gross eye movements to check the degree of separation of images in various positions. The Hess chart, red-glass test, or the cover-uncover test may be used.The Hess chart involves placing a red filter in front of one eye and a green filter in front of the other. The patient looks at a screen of small white dots and then is asked to point to specific dots with a pointer where the amount of mislocation is measured. The red-glass test involves placing a red glass in front of the right eye and a green glass in front of the left. The patient looks at a light 20 feet away and then at a separate light 14 inches away. The patient tells the examiner if separate red and green lights are seen while fixating on the near or far light. During the cover-uncover test, the patient looks at a letter or object at 20 feet. One eye is covered and the other is observed to see whether it moves to fixate on the object. If the eye moves, a disorder is present. The other eye is tested at 20 feet and then both are tested at 14 inches. Diplopia may be caused by a misalignment of the eyes, as in strabismus (or a latent strabismus from childhood), an ocular muscle imbalance; third, fourth, or sixth cranial nerve palsy; orbital lesions; muscle lesions; cataracts; nerve lesions; multiple sclerosis; myasthenia gravis; injury to the orbit; thyrotoxicosis, in which extraocular muscles become inflamed; stroke; or intracranial tumor. The condition is treated with corrective lenses, surgery, or medication, depending on the underlying cause.
Divergence is the movement of the eyes from a convergent position. Convergence is the turning-in movement of the eyes to focus on a near object. When the object is too close to the nose to be seen as one image, the eyes diverge, or move from the convergent position.
Dominant Eye – Many people not only have a dominant hand (either right or left) but also a dominant eye that gives them more comfortable vision despite equal vision with their nondominant eye. To find your dominant eye, bring together the tip of your thumb and forefinger into an “O”, about six inches from your face. Focus on an object across the room so that it is in the middle of the “O”. Closing one eye and then the other will tell you which eye is dominant. If you close your left eye and the object is still in the center of the “O”, then your right is the “sighting” or dominant eye – or vice versa. Interestingly, when a person has had lenses replaced, as in the case of bilateral cataract surgery, the dominant eye is removed and both eyes are the same.
- Drugs – Those that can damage the optic nerve, the retina, and other vital parts of the eye are as follows:
- ACTH (an adrennocorticotropic hormone prescribed to stimulate adrenal glands, especially in the treatment of allergies
- Allpurinol (used to treat gout)
- Anitcoagulants (for example, Heparin or Coumadin)
- Anti-infection drugs
- Diruetics, antihistamines, marijuana, and digitalis preparations, which cause disturbances in color distinction
- Nicotinic acid (found in cigarette and cigar smoke and in chewing tobacco)
- Diazepam, haloperidol, psychotropic drugs, quinine, and sulfonamides
Dry eyes occur when the system that produces tears breaks down causing the cornea, or parts of it, to dry out. Some people produce a normal amount of tears, but the composition of the tears is of poor quality. That means the tears lack such components as oil that are essential for lubrication. Tear production and quality will decrease with age, as they will with some medications, menopause, autoimmune disorders, chemical burns, pollutants, disruptions of the blink reflex, an allergic reaction to eyedrops or ointments, eyestrain, or eyelid deformities.The medical term for a dry-eye condition resulting from the aging process is keratoconjunctivitis sicca. Although dry eyes affect both men and women at any age, it is more common among post-menopausal women and may be causesd by hormonal changes. There are certain diseases or disorders that may also lead to a drying of the eyes and a scratchy feeling, including rheumatoid arthritis, SLE (lupus), scleroderma, Sjogren’s syndrome, blepharitis, entropion, or ectropion. Damage to the lacrimal glands from inflammation or radiation can also hamper tear production. Dryness usually affects both eyes and will cause such symptoms as stinging, burning, a scratchy sensation, stringy mucus in or around the eyes, increased eye irritation from smoke or wind, eye fatigue after short periods of reading, and difficulty wearing contact lenses. One study found that people with Sjogren’s syndrome, which is characterized by dry eyes, had the lowest levels of essential fatty acids. Therefore, consuming good quality, cold-pressed oils everyday and staying away from the hydrogenated ones, go a long way in improving this syndrome and preventing dry eyes in general.