Corneal Abrasion

A corneal abrasion is a cut or scratch on the cornea, which is the clear, protective membrane covering the colored part of the eye (iris). Corneal abrasion can be caused by sand, dust, dirt, and shavings from materials such as metal. Fingernails, tree branches, rubbing your eyes, and even contact lenses can also scratch the cornea. Some patients have a weak outer layer of the cornea that can sustain an abrasion for no apparent reason.

Most corneal abrasions heal properly with the proper treatment. However, if the treatment isn't successful, the abrasion can reappear months following the originally injury.

Corneal abrasions are painful because of the sensitivity of the cornea. Patients may feel as if there is sand in their eye. Their eyes become teary and red. Their vision is blurry and light hurts their eyes (photophobia). Corneal abrasions have been known to cause headaches.

Fluorescein sodium and fluress (fluorescein sodium and benoxinate HCl) are used to diagnose corneal abrasions and to locate lesions or foreign objects in the eye.

Fluorescein is a dye used to demonstrate defects in corneal epithelium and is excreted in nasal secretions if the lacrimal (tear) duct is patent.

When fluorescence strips are used to examine the eye:

• Corneal scratches turn bright red.

• Foreign bodies are surrounded by a green ring.

• Loss of conjunctiva appears orange yellow.

Fluress is a dye and a local anesthetic and is used for short corneal and con-junctival procedures such as removing foreign bodies from the eye.

Eye Medication

Eye disorders are treated by using one of a variety of medications (Table 22-1). Topical Anesthetics

Topical anesthetics are used to anesthetize the eye for comprehensive eye examinations and for removal of foreign bodies from the eye. Onset occurs in about 1 minute and lasts for 15 minutes. During this time, the blink reflex is temporarily lost and the corneal epithelium is temporarily dried. The patient is required to wear a protective eye patch until the effects of the drug wear off.

Anti-infectives and Antimicrobials

Anti-infectives and antimicrobials are administered for eye infections such as conjunctivitis. These drugs can cause local skin and eye irritation. You learned about anti-infective and antimicrobial medication in Chapter 12 and Chapter 13.

Lubricants

Lubricants are used to alleviate the discomfort that is associated with dry eyes and to moisten contact lenses and artificial eyes. Lubricants are also used to maintain the integrity of the epithelial surface and to moisten the eye during anesthesia and unconsciousness.

Miotics

Miotics lower intraocular pressure in open-angle glaucoma allowing increased bloodflow to the retina. This results in less retinal damage and prevents the loss of vision. There are two types of miotics: direct-acting cholinergics and cholin-esterase inhibitors. Direct-acting cholinergics pupillary constrict and cholinester-ase inhibitors pupillary constrict. Patients who take miotics might experience headache, eye pain, decreased vision, brow pain, and less frequently hyperemia of the conjunctivia (red eye). Miotics can be systemically absorbed resulting in the patient experiencing nausea, vomiting, diarrhea, frequent urination, precipitation of asthma attacks, increased salivation, diaphoresis, muscle weakness, and respiratory difficulty.

Carbonic Anhydrase Inhibitors

Carbonic anhydrase inhibitors are used as a long-term treatment for open-angle glaucoma by decreasing intraocular pressure by interfering with the production of aqueous humor. Patients who take carbonic anhydrase inhibitors can experience lethargy, anorexia, drowsiness, paresthesia, depression, polyuria, nausea, vomiting, hypokalemia, and renal calculi. It is because of these adverse side effects that patients frequently discontinue taking carbonic anhydrase inhibitors. Carbonic anhydrase inhibitors are contraindicated in the first trimester of pregnancy and for patients who are allergic to sulfonamides.

Osmotics

Osmotics are preoperative and postoperative medications used to reduce intraocular pressure by decreasing vitreous humor volume. They are also used in the emergency treatment of closed-angle glaucoma. Patients who are administered osmotics can experience headache, nausea, vomiting, and diarrhea. Elderly patients can become disoriented.

Anticholinergic mydriatics and cycloplegics

Anticholinergic mydriatics and cycloplegics are used in diagnostic procedures and ophthalmic surgery. Anticholinergic mydriatics dilate the pupils. Cycloplegics paralyze eye muscles. Patients who are treated with these medications experience tachycardia, photophobia, dryness of the mouth, edema, conjunctivitis, and derematitis. You learned about anticholinergics in Chapter 15.

A list of eye disorder drugs is provided in the Appendix. Detailed tables show doses, recommendations, expectations, side effects, contraindications, and more; available on the book's Web site (see URL in Appendix).

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