Ophthalmologic Procedures

Chapter 62


Ophthalmologic Procedures



The following discussion focuses on procedures performed by emergency clinicians during the evaluation and treatment of injuries and diseases of the eye. Emphasis is placed on practical application of the techniques; cautions to be heeded by the emergency clinician are included.



Assessment of Visual Acuity


Evaluation of visual acuity may initially be deferred with simple, obvious, or straightforward cases, such as a stye, periorbital laceration, or minor eye irritation; however, assessment of visual acuity should be the first procedure performed in the majority of patients seen in the emergency department (ED) with an eye complaint. Even though it may initially be deferred in the triage or trauma room setting or under other relevant scenarios, it is incumbent on the emergency clinician to ensure that visual acuity or function is ultimately assessed adequately.



Indications


Visual acuity should be assessed as soon as practicable and before the patient is examined with bright lights. In the event of blepharospasm from an injury (e.g., abrasion, chemical exposure), a topical anesthetic may facilitate the examination. Patients are often encountered in the context of an eye complaint and say that they “can’t see.” In these instances, emergency visual acuity assessment should be performed first, beginning with evaluation of light perception, then hand motion, and finally counting fingers at 3 ft (Fig. 62-1). If the patient succeeds in performing these assessments, a near vision card may then be used or distant visual acuity assessed. In emergency circumstances, detailed formal vision testing is not essential; however, some form of visual acuity assessment is needed. In this situation, the ability to count fingers or read newsprint gives some indication of gross visual function. Formal visual acuity testing should never delay important therapeutic interventions such as eye irrigation.1




Distant Visual Acuity Procedure


For formal vision testing, ask the patient to face a well-lit standard Snellen or similar eye chart from a premeasured distance of 20 ft. Use a card or the palm of the hand to occlude one eye at a time. If possible, examine all patients while wearing their current lens correction to obtain the best corrected distant visual acuity. If not available, measure visual acuity first without correction and then with a pinhole device, and note any improvement in visual acuity. This device functions as a corrective lens by reducing corneal refractive error. In general, visual acuity is improved with the pinhole device. Decreased visual acuity that is not improved with this device suggests that corneal refractive error is not the cause. Construct a pinhole device by punching one to several holes in the center of a card (3- × 5-inch index card) with an 18-gauge needle. Devices with one or more pinholes drilled into an eye cover are available commercially (Fig. 62-2A and B) or can be constructed from readily available material in the ED, such as the index card with holes just mentioned. Figure 62-2C presents a chart for testing visual acuity while the patient is on a stretcher or in a chair. The chart can be used directly from this text if held 14 inches from the eye. Begin by testing the affected eye or the one presumed to have the worst visual acuity. First, instruct the patient to read the smallest letters on the chart that can easily be seen. Then ask the patient to read letters that can just barely be made out (i.e., they do not have to be clear). If the patient is unable to read the largest letter on the chart, move the patient to half the distance from the chart (10 ft), or if using the figure in this text, move it 7 inches closer to the eye and repeat the procedure. Record the results reflecting the change in distance (e.g., 10/200). The numerator in the vision ratio is the distance of the patient from the chart and the denominator is the distance at which a patient with normal vision can read the line of letters. For patients who still cannot read the letters on the chart, test vision progressively as follows: the ability to count fingers, detect hand motion, and perceive light (with or without projection—the ability to perceive the direction of light), and finally, the inability to perceive light.2




Near Visual Acuity Procedure


Perform near visual acuity assessment in the ED at the bedside or at triage. Hold a pocket near vision card (see Fig. 62-2C) or any printed material in good light at a distance of approximately 14 inches in front of the patient and occlude each eye alternately as described earlier. When using available printed material in lieu of a near vision card, measure the size of the letters that are discerned by the patient. At a later time compare these letters with the size of the letters on the near vision card to deduce the patient’s actual visual acuity. When near vision is decreased, it is usually caused by either loss of visual function or poor accommodation as a result of advancing age (presbyopia). Less commonly, it is caused by traumatic mydriasis. Thus, examine patients with presbyopia with their reading correction in place to obtain the best corrected near visual acuity.


For patients who cannot communicate or in whom factitious blindness or malingering is suspected, check for optokinetic nystagmus (OKN) to determine whether the visual pathway is intact. To test for OKN, pass a regularly sequenced pattern in front of the eyes. If an optokinetic drum is available, rotate the drum in front of the patient (Fig. 62-3). This is not available in many EDs, however. In place of the drum, substitute a printed piece of paper such as newsprint (without photographs or large areas with no print) or a standard tape measure. Pass it in front of the patient’s eye at reading distance while instructing the patient to look at it as it moves rapidly by. Evaluate for tracking as demonstrated by nystagmus-like eye movements seen when the test object is moved from side to side in front of the patient. Such movement indicates an intact visual pathway. Finally, another effective method is to hold a mirror in front of the patient and slowly rotate the mirror to either side of the patient. Patients with an intact visual pathway will maintain eye contact with themselves as demonstrated by eye movement as the mirror is moved. A large mirror that reflects the patient’s entire face is most effective for this purpose.



All patients with decreased visual acuity from baseline require routine referral for further ophthalmologic follow-up; however, patients with moderately or severely decreased visual acuity not explained by refractive error require ophthalmologic consultation in the ED.



Dilating the Eye


Dilating the eye is useful for both diagnostic and therapeutic purposes. Be advised, however, that an attack of narrow-angle (angle-closure) glaucoma may be precipitated by dilating the pupil. The most common form of glaucoma, however, is open-angle glaucoma, and this type is not precipitated by dilating the pupil. Some patients may have a “mixed mechanism” glaucoma with both open-angle and narrow-angle components. Systemic reactions, such as bradycardia or even heart block from β-blocker eyedrops, can be induced by mucosal absorption of dilating medications.


There are two types of dilators: sympathomimetic agents, which stimulate the dilator muscle of the iris, and cycloplegic agents, which block the parasympathetic stimulus that constricts the iris sphincter. Cycloplegic agents also block contraction of the ciliary muscles, which control focusing of the lens of the eye. This second effect of cycloplegic agents is beneficial in the therapeutic use of dilators for iritis.


Cycloplegic agents were used cosmetically as early as Galen’s time. Beginning in the early 1800s, extracts from the plants Hyoscyamus and belladonna were used in ophthalmology. Atropine was first isolated in 1833. Epinephrine was used on eyes in 1900 as the first sympathomimetic agent.3



Indications and Contraindications


There are several diagnostic and therapeutic indications for dilating the pupil. Dilation is indicated for diagnosis when the fundus cannot be examined adequately through an undilated pupil. An elderly patient with miotic pupils and cataracts is an example of a patient in whom dilation may facilitate funduscopic examination. Dilation is therapeutically useful for many ophthalmic conditions, including inflammation of the eye. In the emergency setting, corneal injury with secondary traumatic iritis is a common example. Dilation helps the inflamed eye in two ways. First, it may hinder adhesions (synechiae) from forming between the iris and other ocular structures. Such adhesions eventually limit movement of the pupil and may precipitate glaucoma. Second, cycloplegic dilating agents relax the ciliary muscle spasm that often accompanies an inflamed eye and thus may reduce the pain associated with inflammation. Though traditionally used for these purposes, both benefits are largely theoretical with little formal evidence to support or refute their use in the ED.


Dilation is discouraged in patients with head injury who are at risk for herniation when it is necessary to monitor pupil findings. Dilation is contraindicated in the presence of narrow anterior chamber angles. Patients predisposed to having narrow angles may be unaware of this condition. Evaluate the depth of the anterior chamber before this procedure, and do not dilate the eye if there is any question of a narrow angle. To estimate the depth of the anterior chamber, shine a penlight tangentially from the lateral side of the eye. When the depth of the anterior chamber is normal, uniform illumination of the iris is seen. However, when the iris has a forward convexity as in the case of a narrow anterior chamber, only a sector of iris is illuminated and there will be a shadow on the medial (nasal) side of the iris (Fig. 62-4). With a slit lamp, the depth of the anterior chamber angle can be assessed directly. The definitive test for assessing the anterior chamber angle is gonioscopy, in which the anterior chamber angle structures are viewed directly by means of a special mirrored contact lens and a slit lamp. Gonioscopy is not a technique normally performed by emergency clinicians.



image


Figure 62-4 A, Left: The normal eye. Aqueous humor, produced in the posterior chamber, flows through the pupil into the anterior chamber. The major pathway for the egress of aqueous humor is through the trabecular meshwork into Schlemm’s canal. Right: Primary angle-closure glaucoma. In anatomically predisposed eyes, transient apposition of the iris at the pupillary margin to the lens during pupil dilation blocks the passage of aqueous humor from the posterior chamber to the anterior chamber. Buildup of pressure in the posterior chamber bows the iris forward and occludes the trabecular meshwork. B, Left: Normal anterior chamber with a negative transillumination test. Note that the entire iris is illuminated. Right: Shallow anterior chamber with a positive transillumination test. Note the shadow on the outer half of the iris. C, Left: Clinical use of the penlight examination to assess the depth of the anterior chamber of the right eye. The examiner sits face to face with the patient to ensure that the light source is perfectly perpendicular to the line of vision. Right: The axial anterior chamber depth of the right eye is less than normal. This can be demonstrated by shining a light across the eye from the temporal side. Because of the convexity of the iris-lens diaphragm, the nasal iris manifests a crescentic shadow (eclipse sign). (A, From Kumar V, Abbas AK, Fausto N, et al, eds. Robbins and Cotran Pathologic Basis of Disease, Professional Edition. 8th ed. Philadelphia: Saunders; 2009; B, from Swartz MH. Textbook of Physical Diagnosis. 6th ed. Philadelphia: Saunders: 2009. C, from Kanski JJ. Clinical Diagnosis in Ophthalmology. St. Louis: Mosby; 2006.)


Systemic effects can develop after the application of eyedrops.4–10 Review the following sections on agents and complications before using these drugs in patients with compromised cardiovascular function.



Agents


Only two dilating agents are really needed in the ED. Phenylephrine (Neo-Synephrine) 2.5%, a potent sympathomimetic, is used for diagnostic dilation of the pupil and visualization of the fundus. The drug is short acting, and because accommodation is not affected, the patient’s vision is not altered. Phenylephrine 10% should not be used routinely because it can be absorbed systemically and, in rare cases, has caused hypertensive crisis, myocardial infarction, and death.8,9


For therapeutic cycloplegia in patients with iritis, 5% homatropine works well. Even though Table 62-1 indicates a maximum duration of 3 days, 24 hours is more common. Therefore, 5% homatropine is a useful therapeutic agent for traumatic iritis. Atropine should not be used for traumatic iritis because the undesirable effects of pupillary dilation and blurred vision persist for a week or longer after the associated corneal abrasions have healed. Atropine drops may be prescribed as part of the therapy for nontraumatic iritis after appropriate ophthalmologic consultation. Individuals with lightly pigmented irides tend to have greater sensitivity to cycloplegic agents than do individuals with greater pigmentation; the cycloplegic effect might therefore be more prolonged in people with light eyes. It might be difficult to dilate some patients with deeply pigmented irides, however, and numerous applications of drops might be required.



Malingerers may use mydriatic agents to dilate a pupil unilaterally for the purpose of feigning neurologic disease. Normally, the pupillary dilation caused by intracranial compression of the third cranial nerve will constrict with 2% pilocarpine eyedrops. A mydriatic-treated eye can be identified by full motor function of the third cranial nerve and absence of miosis after the instillation of pilocarpine. A fixed and dilated pupil in an awake and alert patient cannot be secondary to brain herniation. Although other neurologic problems may be present, in a normal-appearing patient with a fixed and dilated pupil, a pharmacologic cause is highly likely. It should be noted that legitimate patients may not recall the name of an eye medicine that they used but will usually recall whether the bottle had a red cap, as is found on all cycloplegic solutions. An unexpected mydriasis in a trusted patient may be the result of such an agent. Medications that constrict the pupil, such as pilocarpine, have a green cap. Pressure-lowering drops for glaucoma may be yellow or blue topped (β-blockers), purple topped (adrenergic agents), or orange topped (topical carbonic anhydrase inhibitors).


A fixed and dilated pupil from a pharmacologic cause may be encountered after both nasotracheal and orotracheal intubation (Fig. 62-5). In such ill or injured patients, cerebral herniation must be considered. When phenylephrine is used to constrict the nasal mucosa before nasal intubation (endotracheal tube, nasogastric tube), inadvertent spread to the eye can result in a fixed and dilated pupil. The same scenario may occur during resuscitation when endotracheal epinephrine has been instilled into the lungs and cardiopulmonary resuscitation has expelled epinephrine into the eye. In such scenarios, the affected pupil will not constrict after intraocular pilocarpine administration. Finally, a fixed and dilated pupil might occur as a result of inadvertent contamination of the eye with scopolamine after the application of a scopolamine patch.




Procedure


Instillation of mydriatic agents is similar to the administration of other eye solutions. For medicolegal purposes, note the patient’s visual acuity before instillation of the medicine. This documents that any decreased vision is not the result of the mydriatic agent. Whenever dilation is performed, note on the patient’s chart the dose and time that agents have been given to avoid confusion during subsequent neurologic evaluation.


Place the patient in a supine or a comfortable semirecumbent position. Instruct the patient to gaze at an object in the upper visual field, such as a fixture on the ceiling. Gently depress the lower lid with a finger on the epidermis. Instill a single drop of the solution into the lower lid fornix, and ask the patient to blink to spread the medication. Do not use more than a single drop because it produces reflex tearing and reduces the concentration in contact with the conjunctiva. Forewarn the patient that the medication is uncomfortable when it goes into the eyes. After the medication has been instilled, the patient may blot the eye when it is closed but should not rub it with a tissue. If the desired effect is not noted in 15 to 20 minutes, repeat the dose, but this is seldom required.



Complications


Any dilator can precipitate an attack of angle-closure glaucoma in susceptible patients.10 In the case of angle-closure glaucoma, it may take several hours before symptoms become evident. The patient often complains of smoky vision with “halos” around lights, as well as an aching pain that is sometimes severe. Nausea and vomiting may occur. If the affected eye becomes injected in association with a hazy cornea, elevated pressure on tonometry, and an oval, fixed pupil, consult an ophthalmologist immediately. Place the patient supine and administer analgesics and antiemetics. Treatment usually includes the agents suggested in Box 62-1, and later, definitive laser or surgical procedures.



Be aware that if contaminated, an eye medication can introduce infection. Most solutions contain bactericidal ingredients, but contamination of the tips of droppers can still occur (Fig. 62-6A).11 Use only newly opened bottles of eye medication or single-use vials, particularly if the patient has a deep corneal injury or has recently undergone eye surgery. Promptly discard out-of-date drops and those in which crust or other material is found around the nozzle.



Forewarn the patient that any cycloplegic (in contrast to a sympathomimetic) will blur a patient’s near vision. Vision will be less blurred in adults older than 45 years, who generally have a reduced ability to focus for near vision. Although most adults will be able to drive safely, even with both eyes affected, it is advisable to have someone else drive whenever feasible. Light sensitivity caused by pupillary dilation may also be bothersome; sunglasses are sufficient for this problem.


Systemic reactions may rarely be induced by sympathomimetic and cycloplegic eyedrops.4–10 In one report of 33 cases of adverse reactions associated with 10% phenylephrine, there were 15 myocardial infarctions (11 deaths), 7 cases of precipitation of angle-closure glaucoma, and a variety of systemic cardiovascular or neurologic reactions.9


After instillation of eyedrops into the conjunctival sac, systemic absorption can occur through the conjunctival capillaries, as well as by way of the nasal mucosa, the oral pharynx, and the gastrointestinal tract after passage through the lacrimal drainage system. Mucosal hyperemia enhances absorption. Symptoms can often be avoided by maintaining digital pressure on the nasal canthus to occlude the puncta for several minutes after administration (Fig. 62-6B).4



The Fluorescein Examination


Perform fluorescein staining of the eye as part of the evaluation of all patients with eye trauma and infection. It is a quick and easy technique that is crucial for the proper diagnosis and management of common eye emergencies. View the fluorescein-stained cornea and conjunctiva under a “blue” light and ideally in conjunction with slit lamp magnification (see “Slit Lamp Examination,” later in this chapter).


Sodium fluorescein is a water-soluble chemical that fluoresces. It absorbs light in the blue wavelengths and emits the energy in the longer green wavelengths. It fluoresces in an alkaline environment (such as in Bowman’s membrane, which is located below the corneal epithelium) but not in an acidic environment (such as in the tear film over intact corneal epithelium).12 Thus it is useful in revealing even minute abrasions on the cornea.


Fluorescein was initially used in ophthalmology in the 1880s.13 It was first used as a drop, but when the danger of contamination by bacteria (especially Pseudomonas) was recognized in the 1950s,14 paper strips impregnated with fluorescein were developed. These strips are now supplied in individual sterile wrappers and should be used instead of the premixed solution.



Indications and Contraindications


Fluorescein staining is indicated for the evaluation of suspected abrasions, foreign bodies (FBs), and infections of the eye,15 including “simple” cases of conjunctivitis, which may actually be herpetic keratitis. Exposure of the face to pepper spray has been associated with corneal abrasions, and such patients should undergo fluorescein staining and be evaluated with a slit lamp or Wood’s lamp.16 Corneal defects may be seen after even a few seconds of unprotected viewing of a welder’s arc flame.


Fluorescein permanently stains soft contact lenses. Therefore, when fluorescein is used, remove soft contact lenses before instilling the fluorescein and caution the patient to not put the lenses back into the eye for several hours. Topically administered fluorescein is considered nontoxic, although reactions to a fluorescein-containing solution (not impregnated strips) have been described.17 These reports, which consist of vagal reactions18 and generalized convulsions,19 are rare, not rigorously supported, and believed to be caused by agents other than fluorescein in the solution. If using one of these fluorescein-containing solutions rather than the fluorescein-impregnated strips, be aware of these potential, yet scientifically suspect idiosyncratic reactions.


Also be aware that fluorescein dye may enter the anterior chamber of the eye in patients with deep corneal defects. This form of intraocular fluorescein accumulation is nontoxic. When the anterior chamber is viewed under the blue filter of the slit lamp, a fluorescein “flare” is visible and should not be confused with the flare reaction noted with iritis.



Procedure


Theoretically, one should not use topical anesthetics before fluorescein staining because a superficial punctate keratitis may develop in some patients from the anesthetic,12 which can confuse the diagnosis. However, in patients who are tearing profusely and squeezing their eyes shut from an abrasion or an FB, the examination is often impossible if a topical anesthetic is not first used. Theoretical downsides notwithstanding, it is common practice to apply a local anesthetic before instilling fluorescein.


Grasp the fluorescein strip by the nonorange end and wet the orange end with 1 drop of saline. Several convenient forms are available, including a small bottle of artificial tears or a 5-mL “bullet” or “fish” of normal saline commonly used for nebulizer treatments. Alternatively, wet the strip with tap water or the recently used local anesthetic drops. Once the strip is moistened, place it gently on the inside of the patient’s lower lid (Fig. 62-7, step 1). Withdraw the strip and ask the patient to blink, which spreads the fluorescein over the surface of the eye. The key to a good examination is to have a thin layer of fluorescein over the corneal and conjunctival surfaces. If the strip is too heavily moistened before placing it in the lower fornix, the eye may become flooded with the solution, which makes evaluation difficult. If too much dye accumulates, the patient can remove the excess dye by blotting the closed eye with a tissue. Conversely, placing a dry strip in an unanesthetized eye may be irritating. Next, use a Wood lamp (4× magnification), the blue filter of a slit lamp, or simply a penlight with a blue filter to examine the eye in a darkened room (see Fig. 62-7, step 2). Check for areas of bright green fluorescence on the corneal and conjunctival surfaces. The naked eye may not be able to see small defects. Ideally, use a slit lamp with 10× or 25× magnification to examine the stained cornea before ruling out a pathologic process. A new handheld magnification device, the Eidolon Bluminator ophthalmic illuminator, produces an intense blue light from a light-emitting diode with 7× magnification (see Fig. 62-7, step 3). After completion of the fluorescein examination, irrigate excess dye from the eye to minimize damage to the patient’s clothing from dye-stained tears.



The Seidel test uses fluorescein to detect perforation of the eye.20 To perform this test, instill a large amount of fluorescein onto the eye by profusely wetting the strip. Examine the eye for a small stream of fluid leaking from the globe (see Fig. 62-7, plate 4). This stream will fluoresce blue or green, in contrast to the orange appearance of the rest of the globe flooded with fluorescein.12



Interpretation


Fluorescein is used mainly for evaluation of corneal injuries. Although conjunctival abrasions pick up the stain, most of the staining on the conjunctiva represents patches of mucus rather than a real pathologic condition. Corneal staining is more specific for injury, and the pattern of injury often reflects the original insult.


Corneal staining patterns are illustrated in Figures 62-7 and 62-8. Abrasions usually occur in the central part of the cornea because of the limited protection of closure of the patient’s eyelids. The margins of the abrasions are usually sharp and linear if seen in the first 24 hours (see Fig. 62-7, plate 6). Circular defects are seen about embedded FBs and may persist for up to 48 hours after removal of a superficial foreign object. Deeply embedded objects may be associated with defects persisting for longer than 48 hours. Objects under the upper lid (including some chalazia) often produce vertical linear lesions on the upper surface of the cornea (see Fig. 62-7, plate 7). When vertical lesions are noted, search diligently for a retained FB under the upper lid. Overuse of hard contact lenses diminishes the nutrient supply to the cornea. The central part of the cornea sustains the most injury and thus fluoresces brightly when stained. Excessive exposure to ultraviolet light as a result of sunlamp abuse, snow blindness, or welding flashes produces a superficial punctate keratitis, which in its mildest form may not be visible without a slit lamp (see Fig. 62-7, plate 8). The central part of the cornea is the least protected by the lids, and a central, horizontal band–like keratitis can result. Herpetic lesions may develop anywhere on the cornea. Classically, these lesions are dendritic, although ulcers may also be punctate or stellate (see Fig. 62-7, plate 9).21,22



Any area of corneal staining with an infiltrate or opacification beneath or around the lesion should alert the practitioner to the possibility of a viral,21,22 bacterial,23 or fungal24 keratitis. Obtain urgent ophthalmologic consultation so that cultures of the possible etiologic agents can be procured and appropriate treatment initiated.


Many Pseudomonas organisms fluoresce when exposed to ultraviolet light25; therefore, the presence of fluorescence before the instillation of fluorescein in a red eye should suggest the possibility of infection with this organism.




Eye Irrigation


The crucial first step in the treatment of chemical injuries to the eye is irrigation. Irrigate as clinically appropriate for the severity, length of exposure, and causative agent. Serious chemical injury to the eye requires irrigation at the site of the injury, even before the patient is brought to the ED.15 Corneal injury can occur within seconds of contact with an alkaline substance. Continue eye irrigation in the ED.


This section discusses methods of irrigation. Although it is best to irrigate liberally, copious irrigation is not needed when the patient has just a small amount of a noncaustic, nonalkaline compound in the eye.





Procedure



Basic Technique


First, instill a topical anesthetic into the eye (Fig. 62-9, step 1). Evert the eyelid and sweep out any particulate matter in the conjunctival fornices with a moistened, cotton-tipped applicator15 (see “Ocular FB Removal,” later in this chapter, and Fig. 62-9, step 2). Hold the eyelids open during irrigation (see Fig. 62-9, step 3). The easiest method is to use gauze pads to grasp the wet, slippery lids and hold them open. If the patient has severe blepharospasm, consider using lid retractors (Desmarres or paper clip retractors; Fig. 62-10). When lid retractors are used, be certain that the eye is well anesthetized, that the retractors do not injure the globe or the lids, and that chemicals are not harbored under the retractors. Be aware that simple retractors fashioned from metal paper clips (especially those that are nickel plated and shiny) may have surface chipping, which can create an ocular FB.26 Exercise caution to avoid ocular injury when using such a makeshift retractor.




Deutsch and Feller15 recommended an ipsilateral facial nerve block for severe blepharospasm (Fig. 62-11). To avoid swelling of periorbital tissue, block the facial nerve just anterior to the condyloid process of the ipsilateral mandible. Place a subcutaneous line of anesthetic (2% lidocaine) to temporarily paralyze the orbicularis muscle.



Irrigate with normal saline or LR solution directed over the globe and into the upper and lower fornices (see Fig. 62-9, step 4). The choice of fluid initially is less important than initiating irrigation as rapidly as possible. If tap water is available at the scene of the injury, begin irrigation immediately with copious amounts of fluid before transporting the patient to the hospital. Teach out-of-hospital care providers to irrigate all acid injuries of the eye for at least 5 minutes at the scene and to irrigate all alkali injuries for at least 15 minutes.27,28 LR or normal saline solution is preferred over tap water or 5% dextrose in water for eye irrigation because these solutions are isotonic and do not contain dextrose. Dextrose can be quite sticky if spilled and might serve as a nutrient for an opportunistic bacterial infection. Although one clinical trial found a balanced salt solution less painful in patients with a chemical eye injury,29 another volunteer study on uninjured eyes found that LR solution is better tolerated than normal saline and balanced saline solution when used with a Morgan lens.30 Warmed fluids are also better tolerated than fluids at room temperature.31 Warmed LR solution should be considered when both it and normal saline are available for eye irrigation.


Be careful to direct the irrigating stream onto the conjunctiva and then across the cornea without letting the stream splash directly onto the cornea because striking the eye with the solution can in itself be harmful and cause mechanical injury (see Fig. 62-9, step 5). Direct irrigation of the cornea can result in the development of a superficial punctate epithelial keratopathy.


Before irrigation, instill anesthetic eyedrops, such as 0.5% tetracaine. Adding 10 mL of 1% lidocaine to a liter of irrigating fluid can decrease patients’ discomfort during prolonged irrigation.



Duration of Irrigation


Although Deutsch and Feller15 recommended that a full liter of irrigating solution be used in every case of caustic injury, the duration of irrigation is best determined by the extent of the exposure and the causative agent. Acids are quickly neutralized by proteins in the surface tissues of the eye and, once irrigated out, cause no further damage. The only exceptions are hydrofluoric and heavy metal acids, which can penetrate through the cornea. Alkalis can penetrate rapidly and, if not removed, will continue to produce damage for days because of slow dissociation of the cation from combination with proteins.15 Therefore, prolonged irrigation is indicated and at least 2 L of solution should be used. Although rapid flushing with the first 500 mL is prudent, slow continuous irrigation, as discussed later, at a rate sufficient to generate a continuous trickle is often more effective and better tolerated than continued high-volume flushing. If the nature of the offending agent is unknown or in question, use prolonged irrigation.


Consult ophthalmology for all alkaline, hydrofluoric acid, and heavy metal acid injuries. Irrigation on an inpatient basis may be required for a period of 24 hours or longer, especially when the cornea is hazy or obviously thickened. Note that the magnesium contained in sparklers combines with water from tears to produce magnesium hydroxide.32 Treat such fireworks injuries as alkaline injuries rather than as thermal injuries. Treat eye damage from hair straighteners,33 phosphate-free detergents,34 and automobile air bags35 as alkaline injuries also.


Measure the pH of the conjunctival fornices with a pH paper strip to check the effectiveness of irrigation (see Fig. 62-9, step 6). In addition to litmus paper, the pH indicator on urine multi-indicator sticks can be used. The pH indicator on urine dipsticks is conveniently closest to the handle; all the distal indicator squares can be cut off with scissors. Normal tear film pH is 7.4. Use the noninjured eye as a control if the results are equivocal. If the pH measured in the conjunctival fornices is still abnormal after the initial irrigation, continue to irrigate. If the pH is normal after irrigation, wait 20 minutes and check it again to make sure that it remains normal, especially if alkaline contamination has occurred. Delayed changes in pH are usually the result of incomplete irrigation and inadequate swabbing of the fornices. In anticipation of this deficiency, measure the pH deep in the fornices. Consider double-lid eversion with a lid elevator to expose the upper fornix for swabbing, irrigation, and pH testing.



Prolonged Irrigation


Alkaline burns may require prolonged irrigation, and it is essential to consult ophthalmology in such cases. The Morgan Therapeutic Lens is a contact lens–type irrigation device that can provide slow, continuous irrigation once the more vigorous initial irrigation has been completed (Fig. 62-12). First, anesthetize the eye with topical anesthetic drops. Then place the device carefully on the surface of the eye with the lids closed around the intravenous tubing adaptor. Attach the intravenous tubing to the adaptor and provide continuous flow through the device onto the cornea and into the fornices. As the local anesthetic agents wash out during the irrigation process, the device can become uncomfortable, so reapply the anesthetic drops frequently during irrigation for patient comfort. Such short-term use of local anesthetics will not inhibit healing of the cornea.




Complications


The only significant complication from irrigation is abrasion of the cornea or the conjunctiva. This can be a mechanical injury from trying to keep the lids open in an uncooperative patient, a small corneal epithelial defect from a Morgan irrigating lens, or fine punctate keratitis from the irrigation itself.36 For this reason, do not direct the stream directly onto the cornea. If a superficial corneal defect occurs, treat it in the usual manner. Deep or penetrating corneal injuries are likely to be a result of the caustic chemical and require emergency ophthalmologic consultation. Continue to provide slow continuous irrigation pending arrival of the ophthalmologist. Some experimental evidence suggests that massive parenteral or oral ascorbic acid supplementation may prevent the development of deep corneal injury,37 but such treatment has not gained universal acceptance.




Ocular FB Removal


Patients with an external FB in the eye are frequently seen in EDs. They are often in pain and desperate for help. Maintain a high degree of suspicion for FB injuries and perforation of the eye because such injuries may be occult and not readily detected. Not all FB injuries are associated with pain. Glass embedded in the cornea may be particularly difficult to detect. This section reviews procedures for locating and removing extraocular FBs and appropriate postprocedural care. Finally, a brief discussion covering evaluation of the eye for potential perforation of the globe and detection of the presence of an intraocular FB is provided.



Indications and Contraindications


Extraocular FBs must always be removed. The timing of removal and the technique required vary according to the patient’s clinical status and the type of injury. For the most part the emergency clinician can proceed directly to removal of the object via the techniques described in this section. When the patient is extremely uncooperative (e.g., an intoxicated patient, a mentally deficient patient, or a young child) or when the injury is complicated (e.g., deeply embedded object, multiple foreign objects from a blast injury, or possible globe penetration), consult ophthalmology immediately. A patient with a suspected FB or abrasion after exposure to a projectile (e.g., grinding wheel, hammering, metal objects colliding) should be rigorously evaluated for the presence of a deep intraocular FB. See further discussion later in this chapter. A penetrating injury of the cornea is of particular concern because the iris tissue may prolapse and have an appearance similar to a corneal FB (Fig. 62-13). Hence, in addition to the history of projectile exposure, an irregular pupil, especially a pear-shaped pupil, should alert the clinician that a penetrating injury might have occurred.




Globe Protection


In the evaluation of a patient in whom a penetrating injury to the globe is suspected, perform a careful expeditious examination of the eye, preferably with a slit lamp. Avoid any pressure on the eye or rapid eye movements. If perforation is obvious (e.g., teardrop pupil, flaccid globe, flat anterior chamber, prolapsed iris) or confirmed by slit lamp (positive Seidel test; see Fig. 62-7, plate 4), do not perform any procedures (except perhaps irrigation) and consult ophthalmology early for definitive diagnosis and care. Until the ophthalmologist arrives, protect the eye from further harm by keeping the patient quiet, elevating the head of the bed, and placing a protective shield over the eye. Commercial shields are available for this purpose. When a metal shield is not available, construct a makeshift protective shield with the material available (e.g., paper, plastic, or Styrofoam cups; Fig. 62-14). The protective shield helps avoid pressure on the globe and overlying tissue and assists in preventing extrusion of vitreous and other ocular contents. Extend the edges of the shield up to or beyond the bony orbital rim for this purpose. Apply adhesive tape over the shield from the forehead to the cheek to secure the shield in position.



If a patient has a globe perforation, treat with systemic antibiotics (a combination of cefazolin and gentamicin is a good initial choice), tetanus toxoid, and antiemetics in doses aggressive enough to halt vomiting.




Consideration of an Intraocular FB


When examining a patient with an ocular “FB” sensation, always remain cognizant of the potential for an intraorbital or intraocular FB. Penetrating injuries represent a greater threat to visual loss than an extraocular FB does and can be disastrous if overlooked. Note that an intraocular FB can be deceptively subtle on initial evaluation. Bedside ED ultrasound is a useful adjunct for identification of intraocular FBs (Fig. 62-15).



The clinical findings are most helpful in determining which patients are at risk for a penetrating injury to the globe. An individual who complains of an FB sensation in the absence of trauma or one whose history is simply that something “fell” or “blew” into the eye is at low risk for perforation of the globe. Conversely, there is a greater probability of globe penetration in an individual who has sustained a high-velocity wound to the eye (e.g., drilling, hammering, grinding metal, blasting rock). The presence of any of the following findings on physical examination should alert the clinician to a probable intraocular FB: irregular pupil, shallow anterior chamber on slit lamp examination, prolapsed iris, positive Seidel test (see “The Fluorescein Examination,” earlier in this chapter), focal conjunctival swelling, hemorrhage, hyphema, lens opacification, and reduced intraocular pressure (IOP). Do not perform tonometry if penetrating injury to the globe is suspected. Be aware that a penetrating injury may not be associated with eye pain. If there is strong historical evidence and physical findings to support a diagnosis of globe penetration, obtain emergency ophthalmologic consultation.


An intraocular FB is often not visible on direct ophthalmoscopy. Although orbital radiography for radiopaque objects and ultrasonography of the globe have been used for indirect FB localization,15,38 computed tomography of the orbit is now considered the most useful technique (Fig. 62-16).39,40 When plain orbital radiography is performed to look for an intraocular FB, be aware that an eyelid FB may mimic an intraocular FB.41 Patients with a suspected metallic FB should not undergo magnetic resonance imaging if the FB may be intraocular. Therapy for intraocular and intraorbital FBs must be individualized. Frequently, an ophthalmologist can localize an intraocular FB (if the vitreous is clear) with indirect ophthalmoscopy. The role of the emergency clinician is to suspect the diagnosis, protect the eye from further harm, and obtain ophthalmologic consultation. The remainder of this section addresses the problem of extraocular FBs.


Sep 17, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Ophthalmologic Procedures
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