A topical ophthalmic anesthetic agent, if immediately available, should first be instilled into the inferior conjunctival sac. Commonly available topical anesthetics include tetracaine and proparacaine. Proparacaine causes less irritation than tetracaine.24 Each has a duration of action of approximately 10 minutes. Frequent readministration of the topical anesthetic may be necessary every 5 to 10 minutes to ease patient discomfort and facilitate irrigation. An alternative to readministration of local anesthetic would be to add 10 cc of 1% lidocaine to 1 L of crystalloid solution. Compared to an initial instillation of two drops of tetracaine alone, O'Malley et al found that lidocaine added to the irrigant in this way decreased the discomfort of irrigation when the irrigation lasted more than 10 minutes.25
Hang the bag of crystalloid solution at a height of 70 to 200 cm above the patient's head in order to obtain an adequate flow rate.26,27 The traditional eye irrigation technique involves directing the flow of crystalloid solution over the globe at a wide open rate (Figure 155-2). Hold the end of the intravenous tubing 3 to 5 cm above the patient's eye to avoid blunt injury to the ocular surface. An assistant is usually needed to hold the eyelids open. Dry gauze pads will facilitate one's ability to maintain a grip on the slippery eyelids and keep them open. Direct the flow of crystalloid solution at the entire surface of the globe, including into the conjunctival sacs and down to the conjunctival fornices.18,28 Having the patient look in a direction opposite to where the irrigant is directed helps in this regard.29 Although one can point the stream directly at the conjunctiva, it is better to direct it across the cornea in order to reduce the potential for further corneal injury.23
Standard ocular irrigation setup using intravenous tubing. An assistant retracts the eyelids using gauze pads or lid retractors. Complete irrigation of the conjunctival sacs is crucial.
Manual retraction of the eyelids with gauze pads does not always allow for adequate irrigation of the conjunctival fornices. In these instances, eyelid retractors (Desmarres or bent paper clip) must be employed (Figure 155-3). The eye must be well anesthetized when using eyelid retractors, and care must be taken to avoid further ocular injury. Desmarres retractors are preferred to paper clips. Many paper clips are coated with nickel or silver that, when the paper clip is bent, can flake off, resulting in iatrogenic foreign bodies.30 The use of a Water-Pik or handheld drench hose has been described but offers no definite advantages over intravenous tubing.31,32
Eyelid retractors. A. The Desmarres eyelid retractor. B. An eyelid retractor fashioned from a paper clip.
Two commercially available devices exist which are less labor-intensive and facilitate ocular irrigation. The Morgan Lens (MorTan Inc., Missoula, MT) is a scleral contact lens-type device that is designed to fit over the anterior ocular surface (Figure 155-4A). Connect the proximal end of the device to intravenous tubing and start a minimal flow of irrigant solution through the Morgan Lens. Retract the upper eyelid and ask the patient to look down. Insert the lens under the upper eyelid (Figure 155-4B). Retract the lower eyelid and ask the patient to look upward. Insert the lower part of the lens under the lower eyelid (Figure 155-4C). Increase the flow of the irrigant solution through the lens. Remove the lens by reversing these steps (Figure 155-4D).
Eye irrigation with the Morgan Lens. A. The Morgan Lens. B. Placement of the lens under the upper eyelid. C. Placement of the lens under the lower eyelid. D. Removal of the lens. (Photos B–D courtesy of MorTan Inc., Missoula, MT.)
The Eye Irrigator (American Health & Safety, Madison, WI) delivers the irrigant via a U-shaped cannula with multiple perforations through which the irrigant flows (Figure 155-5A). Insert a speculum into the inferior conjunctival sac and retract the lower eyelid (Figure 155-5B). Insert the Eye Irrigator under the upper eyelid (Figure 155-5B). These steps are reversed for removal of the device. This device is somewhat similar to irrigating systems reported both by Yamabayashi and Terzidou.26,27
Eye irrigation with the Eye Irrigator. A. The Eye Irrigator. B. Cross section of the orbit with the Eye Irrigator under the upper eyelid and a speculum opening the lower eyelid.
The EyeCap (Splash Medical Devices LLC, Atlanta, GA) is a simple device to irrigate an eye (Figure 155-6). The unit is quick to set up by just screwing it onto a bottle of sterile saline. The base of the unit has universal threads to attach to a bottle of sterile saline (Figure 155-6). The other end is wide and contoured to fit over the orbit. The device allows the saline to deflect off its sidewalls and pool over the eye. The patient can open their eye “under water” to gently allow high volume eye irrigation. This device cannot be used for foreign bodies embedded in the cornea, penetrating injuries, or if a ruptured globe is suspected.
The EyeCap device attached to a bottle of sterile saline. (Photo courtesy of Joseph Schultz, M.D. and BSN Medical Inc.)
Ocular burns can be caused by chemicals that are primarily in the solid form (e.g., lime). Prior to irrigation, attempt to remove as much solid as possible using a moistened cotton-tipped applicator while everting and retracting the eyelids. Quickly proceed to irrigation once most of the solid material has been removed or if removal is limited by blepharospasm. Copious irrigation is often successful in removing any residual solid material.17 Proceed directly to irrigation when solid material is not suspected in significant quantity and inspect the conjunctival sac for foreign material once the initial irrigation has been completed.
Concern that contact lenses may trap chemicals between them and the cornea appears to be unfounded. Contact lenses may, in fact, be protective and act as a shield between the chemical and the cornea.33,34 Irrigation should not be delayed in order to remove a contact lens unless it appears that a contact lens can be removed easily and quickly. This is the case even when commercial irrigation devices are used. Contact lenses can be removed once an initial period of irrigation has been completed. Refer to Chapter 154 regarding the details of contact lens removal. The contact lenses should be discarded as the chemical may be absorbed by the contact lens, only to be released onto the surface of the cornea if reused.15,33
The choice of irrigation fluid is much less important than the speed with which irrigation is started.18,21 Tap water is perfectly acceptable at the scene of the chemical exposure, although there may be problems with patient discomfort.17 Normal saline and Ringer's lactate solution are both acceptable during ambulance transport and in hospital. It has been thought that the more neutral pH of Ringer's lactate solution (pH 6.0 to 7.2) should cause less patient discomfort than normal saline (pH 4.5 to 6.0). Similarly, balanced salt solutions (e.g., BSS Plus, Alcon Laboratories, Fort Worth, TX) should theoretically cause less patient discomfort due to its enhanced buffering capacity, physiologic osmolarity, and physiologic pH. These theories have yet to be clearly substantiated.14,35,36 Use the irrigant fluid that is most readily available. Balanced salt solutions should be used only in patients who require prolonged irrigation and for whom other irrigants are unsuitable due to their expense and time-consuming preparation (requiring reconstitution in glass bottles).14,35
The use of warmed irrigation fluid appears to increase patient comfort.37 Ernst et al have reported an optimal irrigant temperature of 32.2 to 37.8 °C (90 to 100 °F). Werwath et al found that 120 seconds were required to heat 1 L bags of normal saline and Ringer's lactate solution to a temperature of 101 °F in a microwave oven set at the highest cooking intensity.38 This cannot be routinely recommended, as microwave ovens vary and overheated irrigant fluid will cause secondary injury. Irrigation should not be delayed while an irrigant fluid is being warmed despite the potential value of warmed fluid. Commence irrigation with room temperature crystalloid solution and switch to a warmed crystalloid solution once prepared. Although not experimentally validated, Rost et al has suggested that cooler liquids at the beginning of irrigation may help reduce the heat of the reaction, thus limiting chemical injury.21 Saidinejad and Burns has put forward the unproven theory that using a cold irrigant may provide cold anesthesia.39
There is probably no chemical ocular burn for which crystalloid irrigants are contraindicated.18 Metallic sodium, metallic potassium, and white phosphorus may react violently. Remove any visible solid particles with a cotton-tipped applicator prior to irrigation. Irrigation with copious amounts of crystalloid probably dissipates the heat of the initial reaction more than it initiates a thermochemical reaction.18
The mainstay of treatment for chemical ocular burns is early and copious irrigation. Although specific antidotes usually play little role in the treatment of most ocular exposures, there are some instances where antidotes can be helpful once the initial irrigation has been performed. Consultation with a poison center or Toxicologist should be considered in cases of exposure to unusual agents.23
EDTA may be helpful in removing adherent calcium hydroxide corneal deposits from lime exposures that cannot be removed with a cotton-tipped applicator or toothless forceps.1,10,23 A 0.05 M neutral solution of EDTA can be prepared by diluting 20 mL of Endrate disodium (150 mg/mL) with 180 mL of normal saline.10 A cotton-tipped applicator soaked in the EDTA solution can be used to loosen such deposits. EDTA may also be useful in exposures to potassium permanganate and zinc chloride.10
Ascorbic acid may be useful in potassium permanganate exposures. A 5% solution can be prepared by dissolving a 500 mg tablet of ascorbic acid in 25 mL of normal saline. The resultant manganese oxide deposits can be dissolved by dripping the solution into the eyes from a moistened piece of gauze.40
Numerous other miscellaneous antidotes can be used for specific exposures. Copper sulfate (3% solution) can be used to negate the effects of embedded white phosphorus.10,23 Polyethylene glycol may be useful in phenol exposures.41 Mineral oil has been suggested in the removal of cyanoacrylates.23 Calcium gluconate solutions have no beneficial effect in ocular exposures to hydrofluoric acid.42
Irrigation should be continued for 20 minutes in the home or workplace prior to patient transport. Emergency medical technicians should continue irrigation during ambulance transport until hospital arrival. The duration of any further irrigation in the Emergency Department depends on the severity of the exposure and the nature of the agent.
Minor exposures with nontoxic substances need not undergo copious irrigation. Irrigation with crystalloid solution using a squeeze-type bottle may be sufficient. In fact, irrigation that had been performed either in the home or in the workplace may be all that is needed. However, treatment should proceed as for caustic agents if the chemical nature of the substance is unknown. Assume that any previous irrigation was inadequate and that further irrigation is necessary in the Emergency Department.4
Although no definite standard duration for ocular irrigation is available in the literature, most would agree that patients who are significantly symptomatic or who have received a caustic exposure should have their eyes irrigated with a minimum of 1 to 2 L of crystalloid solution over 20 to 30 minutes.17,43 Exposures to noncaustic agents, milder acid burns, and very mild alkali burns will usually not need further irrigation. Moderate to severe acid burns and anything more than a mild alkali burn will likely require more prolonged irrigation.
The duration of irrigation for caustic exposures is in part governed by pH measurement. After the initial irrigation, measure the pH of the inferior conjunctival sac using wide-range pH paper (i.e., accurate in the pH range of at least 2 to 10) or litmus paper.10 Litmus paper with a narrower range and urine dipsticks may not be adequate. If the pH is abnormal, continue irrigation and recheck the pH at 10 to 15 minute intervals until it normalizes.10,23 If the pH has reached the near-normal range (i.e., 7 to 8), discontinue irrigation and recheck the pH in 10 to 30 minutes to ensure that it continues to remain normal.18,23 In clinically severe caustic burns, regardless of the ocular pH, irrigation should be continued until the patient is evaluated by an Ophthalmologist. Alkali burns are more likely to require prolonged irrigation than acid burns. In fact, several hours of irrigation may be required for severe alkali burns. In this instance, the Ophthalmologist may opt to perform a regional nerve block to incapacitate the orbicularis oculi muscle, thus limiting blepharospasm and improving patient comfort.11