Sickle cell complications

When an African American patient develops a traumatic hyphema, a sickle cell workup should be performed to evaluate the patient for the possibility of sickle cell hemoglobinopathy. Sickle cell patients and carriers of the sickle cell trait are predisposed to sickling of red blood cells in the anterior chamber. Sickle cells are restricted in their outflow through the trabecular meshwork and may raise the IOP dramatically. In addition, the optic nerve appears to be at greater risk of damage in sickle cell patients, even with modest IOP elevations (presumably due to decreases in blood flow to the optic nerve).

All efforts must be made to normalize IOP in these patients. Carbonic anhydrase inhibitors and osmotic agents must be used with caution because of their tendency to reduce the pH and lead to hemoconcentration, both of which may exacerbate sickling of red blood cells. Surgical intervention has been recommended if the average IOP remains 25 mm Hg or higher after the first 24 hours or if there are repeated, transient elevations, with IOP higher than 30 mm Hg for 2–4 days, despite medical intervention.

Campagna JA. Traumatic hyphema: current strategies. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2007, module 10.

Nonperforating Mechanical Trauma

Conjunctival Laceration

In managing conjunctival lacerations associated with trauma, the physician must be certain that the deeper structures of the eye have not been damaged and that no foreign body is present. After a topical anesthetic has been applied, the conjunctival laceration should be explored under slit-lamp examination using sterile forceps or cotton-tipped applicators. If any question remains as to whether the globe has been penetrated, consideration must be given to performing a peritomy in the operating room to better explore and examine the injured area. In general, conjunctival lacerations do not need to be sutured.

Conjunctival Foreign Body

Foreign bodies on the conjunctival surface are best recognized with slit-lamp examination. Foreign bodies can lodge in the inferior cul-de-sac or can be located on the conjunctival surface under the upper eyelid (Fig 13-12). It is imperative to evert the upper eyelid to examine the superior tarsal plate and eyelid margin in all patients with a history that suggests a foreign body. If several foreign bodies are suspected or particulate matter is present, double eversion of the eyelid with a Desmarres retractor or a bent paper clip is advised to allow the examiner to effectively search the entire arc of the superior cul-de-sac (see Fig 13-4).

Figure 13-12 Foreign bodies seen on the everted surface of the upper eyelid.

Following eversion of the upper eyelid, copious irrigation should be used to cleanse the fornix. This procedure should then be repeated using a Desmarres retractor for the upper and lower eyelids. Glass particles, cactus spines, and insect hairs are often difficult to see, but a careful search of the cul- de-sac with high magnification aids in identification and removal. With slit-lamp magnification, the examiner uses a moistened cotton-tipped applicator to remove superficial foreign material. Occasionally, saline lavage of the cornea or cul-de-sac washes out debris that is not embedded in tissue.

When a patient reports foreign-body sensation, topical fluorescein should be instilled to check for the fine, linear, vertical corneal abrasions that are characteristic of retained foreign bodies on the eyelid margin or superior tarsal plate. Foreign matter embedded in tissue is removed with a sterile, disposable hypodermic needle. Glass or particulate matter may be removed with a fine-tipped jeweler’s forceps or blunt spatula. If a foreign body is suspected but not seen, the cul-de-sac should be irrigated and wiped with a moistened cotton-tipped applicator.

Corneal Foreign Body

Identifying the probable composition of a foreign body based on a detailed history is important due to the increased risk of infection associated with vegetable matter. Occult intraocular foreign bodies must be identified when there is a history of exposure to high-speed metallic foreign bodies, most commonly produced by high-speed grinding tools and metal-on-metal hammering.

Corneal foreign bodies are identified most effectively during slit-lamp examination. Before removing the corneal foreign body, the clinician should assess the depth of corneal penetration. If anterior chamber extension is present or suspected, the foreign body should be removed in a sterile operating-room environment. Overly aggressive attempts to remove deeply embedded foreign bodies at the slit lamp may result in leakage of aqueous humor and collapse of the anterior chamber. If such a leak occurs and cannot be adequately tamponaded with a therapeutic bandage contact lens, tissue adhesive and/or urgent surgical repair is required.

If several glass foreign bodies are present, all of the exposed fragments should be removed. Fragments that are deeply embedded in the cornea are often inert and can be left in place. Careful gonioscopic evaluation of the anterior chamber is essential to ensure that the iris and the angle are free of any retained glass particles.

When an iron foreign body has been embedded in the cornea for more than a few hours, an orange-brown “rust ring” results (Fig 13-13). Corneal iron foreign bodies and rust rings can usually be removed at the slit lamp under topical anesthesia with a disposable (25or 26-gauge) hypodermic needle, resulting in minimal tissue disruption. A battery-powered dental burr with a sterile tip may also be used; however, caution must be taken to avoid excessive tissue disruption and thus minimize scar formation. A metallic foreign body that enters the corneal stroma beyond the Bowman layer always results in some degree of scar formation. When these scars occur in the visual axis, they may result in glare and decreased vision from irregular astigmatism. Corneal perforation is a rare complication of foreign-body removal. Judicious decision making is mandatory; if multiple, very small foreign bodies are seen in the deep stroma (as may occur after an explosion) with no resultant inflammation or sign of infection, the patient may be monitored closely, because aggressive surgical manipulation of the cornea in search of the very last particle may be unnecessary. In these cases, a radiologic search, including use of computed tomography, for an intraocular foreign body should be

performed.

Figure 13-13 Corneal rust ring and multiple retained iron foreign bodies.

Therapy following the removal of a corneal foreign body includes topical antibiotics, cycloplegia, and occasionally the application of a firm pressure patch or bandage contact lens to help the healing process. If a pressure patch or bandage contact lens is used, the risk of infection is increased and therefore the patient should be closely monitored.

Corneal Abrasion

Corneal abrasions are usually associated with immediate pain, foreign-body sensation, tearing, and discomfort with blinking. A slit-lamp examination is essential in determining the presence, extent, and depth of the corneal defect. It is very important to make a distinction between a “clean” corneal abrasion, which generally has sharply defined edges and little to no associated inflammation (when seen acutely), and a true corneal ulcer, which is characterized by an inflammation-mediated breakdown of the stromal matrix and possible thinning. Also, it is important to evert the upper eyelid and examine the superior cul-de-sac to rule out a retained foreign body as a cause of the abrasion. Occasionally, a patient may not recall a definite history of trauma but still present with signs and symptoms suggestive of a corneal abrasion. Herpes simplex virus keratitis must be excluded as a possible diagnosis in such cases.

Patching is not necessary for most abrasions; many patients find patches uncomfortable. Abrasions may be managed with antibiotic ointment in combination with topical cycloplegia alone. Topical nonsteroidal anti-inflammatory agents have anesthetic properties and may be used for the