Ординатура / Офтальмология / Английские материалы / Primary Care Ophthalmology_Palay, Krachmer_2005

of extreme shifts in intraocular pressure and force waves through the intraocular tissues. Chorioretinal injuries (tears, detachments, and edema), vitreous hemorrhage, lens subluxation, and damage to the anterior chamber structures (hyphema) are possible consequences of the blunt trauma.

•Nasal decongestants (e.g., Afrin) are administered twice a day on the involved side for 2 or 3 days.

•Antibiotic coverage is controversial, but should be considered if there is a previous history of sinus disease.

•Cold compresses or ice packs are applied to the periorbital region to help diminish edema.

•Instructions for gentle or minimally restricted nose blowing and sneezing are given.

•In most patients, surgical repair of the orbit floor is indicated for persistent entrapment, gross enophthalmos, diplopia (in primary gaze, distance and near) with motility limitation, and extremely large fractures of greater than or equal to one half of the orbital floor on CT evaluation, often associated with inferior displacement of the globe. An additional indication for repair is increased vagal tone from muscle entrapment stimulating the oculocardiac reflex. Patients may manifest persistent nausea, vomiting, and bradycardia.

Follow-up

•Follow-up evaluation is performed approximately 1 week after the initial injury. At this point, the acute edema should be decreased, so the position of the globe and motility can be more accurately assessed. The patient is instructed to watch for local changes, specifically periorbital erythema, an increase in pain, and fever, which can be signs of impending orbital cellulitis.

Traumatic Optic Neuropathy

Symptoms

•A history of traumatic injury to the globe or orbit, causing direct injury of the optic nerve, or to the forehead or temporal region, causing indirect injury of the optic nerve, is reported. Optic nerve injury manifests as a reduction in visual acuity not explained by refractive error or injury to the cornea, lens, or retina.

•Visual acuity can decrease immediately after injury or can be delayed.

Signs

•Color vision and red saturation are decreased and may be accompanied by a visual field defect.

•The optic disc appears normal initially. If an atrophic disc is seen on examination, a chronic process is ongoing or the nerve sustained injury at least 6 weeks previously.

•Signs of nerve injury such as disc hemorrhage and edema may be seen.

•A new relative afferent pupillary defect in the traumatized eye suggests the diagnosis (i.e., no concurrent retinal pathologic conditions or chiasmal damage).

366 CHAPTER 16 • Ocular Trauma

Etiology

•Direct injury to the optic nerve from a sharp injury or compression by fragments of bone, foreign body, blood, or edema can lead to traumatic optic neuropathy.

•A shearing injury to the optic nerve in the optic canal from blunt trauma to the head also has been implicated (indirect traumatic optic neuropathy).

Differential Diagnosis

Diagnostic possibilities include the following:

•Widespread retinal injury, with detachment and/or massive subretinal hemorrhage

•Optic chiasm injury

Workup

•A ruptured globe is ruled out in the involved eye and the fellow eye is examined. A careful pupillary examination demonstrates a relative afferent defect if an optic neuropathy is present.

•Color vision (red saturation) and confrontation visual field testing are performed. Perceived loss of central red recognition in the involved eye is a strong sign of optic nerve compromise.

•CT scanning of the head and orbits should pay special attention to the optic chiasm and optic canal to rule out chiasm and compressive injuries if the history is suggestive of these conditions.

Treatment

•Once the diagnosis is suspected, the patient is immediately referred to an ophthal- mologist/neuro-ophthalmologist for complete assessment and management. If a traumatic optic neuropathy is diagnosed, the patient can be hospitalized and given intravenous high-dose corticosteroids. A recommended regimen is Solu-Medrol 30 mg/kg loading dose, then 5.4 mg/kg/hr for 24 to 48 hours before reevaluating for further therapy. This is the same dosage of corticosteroids currently recommended for spinal cord trauma. Patients should be properly advised about the risks and benefits of this therapy, and appropriate consent should be obtained.

•Antacids or histamine H2 blockers (e.g., oral ranitidine [Zantac] 150 mg every day) are administered in conjunction with the corticosteroids for prophylaxis against corticosteroid-induced gastrointestinal bleeding.

•The patient is reexamined after 2 or 3 days of the corticosteroid regimen. If the visual acuity, color vision (red saturation), and relative afferent defect are stable or improved, the patient begins an oral prednisone taper. If the signs are worse (or get worse after corticosteroid taper), surgical exploration of the orbit or unroofing of the optic canal may be indicated.

•If signs return during the oral prednisone taper, intravenous corticosteroid administration may be reinstituted.

•Serum electrolyte and glucose levels are carefully monitored during heavy corticosteroid administration.

Follow-up

•The prognosis depends on the mechanism of injury and the degree of damage sustained by the optic nerve. With a clinically evident relative afferent pupillary defect, the optic nerve must have sustained a fairly severe injury; therefore, ultimate visual functioning may be poor.

Pupil Asymmetry

See Anisocoria in Chapter 12 for a discussion of disorders potentially causing pupillary asymmetry.

370 CHAPTER 17 • Guide to Ophthalmic Medications

Table 17–1 Ophthalmic Medications

Table 17–1 Ophthalmic Medications—cont’d

372 CHAPTER 17 • Guide to Ophthalmic Medications

Table 17–1 Ophthalmic Medications—cont’d

Diagnostic Medications

Diagnostic medications are agents used to facilitate the ophthalmic examination.

Stains

Stains used in eye examinations include fluorescein and rose bengal. These are topical agents used to highlight epithelial abnormalities.

Fluorescein. Helpful in diagnosing corneal abrasions, fluorescein stains epithelial basement membrane in areas where the epithelium has been removed. Fluorescein is supplied on sterile paper strips, which is the preferred modality, and as a 2% solution that contains benoxinate, a topical anesthetic. However, the bottle containing the 2% solution is easily contaminated in a clinical setting.

Rose Bengal. Rose bengal dye stains sick devitalized epithelial cells and may be helpful in the diagnosis of herpetic ulcers, which may mimic corneal abrasions. Rose bengal is supplied on sterile paper strips.

Anesthetics

Anesthetics are used with diagnostic stains and are essential for ensuring patient comfort and cooperation in intraocular pressure measurements. These agents facilitate ocular examination in the setting of trauma and hasten penetration of dilating agents. Tetracaine hydrochloride (Pontocaine) is available in 0.5% and 1.0% solutions, with a duration of effect of approximately 15 minutes, and stings. Proparacaine hydrochloride (Ophthetic, Ophthaine) is available in a 0.5% solution, with a duration of effect of 10 to 15 minutes, and is less irritating.

Note: All anesthetics are toxic to epithelial cells and thus will delay or prevent epithelial wound healing when used repeatedly. Dispensing these agents to patients is a medical-legal risk and is strongly discouraged unless they are followed carefully.