Striving for the Sterile LASIK Environment

As ophthalmic surgery becomes increasingly sophisticated with excimer laser technology, surgeons must realize that the induced optical changes are occuring in a biological system. The goal of sterilization in the surgical suite is to provide instruments that are free of contamination during the LASIK procedure, for the safety of each patient who is undergoing LASIK. The recommended practices for cleaning and sterilizing microkeratomes have varied considerably between centers and individual surgeons, as well as between different microkeratomes and their manufacturers. However, I believe that as a basic recommended practice, a sterile microkeratome head and a new blade should be used for every patient, and each microkeratome blade should be visually inspected for any defects under the microscope prior to use.

Maintaining the Microkeratome
The challenge of sterilizing microkeratomes lies in the fact that these instruments are often motor-driven units with gears, assembly housing, and cords, which will be damaged if autoclaved, and so these parts are considered ?unsterile.? They must be wiped during the procedure with a lint-free cloth and disinfectant, although some disinfectants are more effective against certain organisms than others. For example, isopropyl alcohol 70% (standard rubbing alcohol) may not offer a sufficient concentration to universally sterilize a cord or a motor.

With respect to the different motors and units, great care must be taken to avoid allowing the cleaning liquid to enter into the power box, and users should unplug the power cable prior to wiping the unit to avoid shock. Manufacturers' instructions vary with respect to the care and cleaning as well as the process of rinsing and sterilization of microkeratomes, but the general principle is that microkeratome parts should be rinsed thoroughly with sterile or distilled water following cleaning. Tap water should be avoided, as it may contain minerals that could affect microkeratome function. The various parts or components of the microkeratome should be thoroughly rinsed by pouring sterile or distilled water over all the surfaces, or by simply immersing them in a clean plastic container of cleaning solution. It may be necessary to rinse each part several times in order to remove the cleaning solution or rinse agent; there have been concerns that these can build up and contribute to inflammation after reuse. After each part is cleaned, it should be dried and visually inspected for any stains, such as water spots, because any defect, debris, or stain could cause a malfunction or the incomplete operation of the microkeratome.

Sterilizer care
Steam sterilizers with reservoirs, or so-called ?tabletop sterilizers,? are very popular. The water should be drained from the reservoir of these sterilizers at the end of the day's cases to prevent them from contaminating the instruments. There have been some clinical situations in which the fluid within the reservoir has built up, allowing organisms to proliferate within this fluid through the weekend or even overnight. When the team turns on the sterilizer the next day, the bacteria may be killed, but byproducts or toxins from the microbial carcasses are allowed to remain, contaminating the instruments and causing severe inflammation or toxic reactions under the flap. Simon Holland, MD, et al have shown that endotoxins released from the remnants of biofilms from the sterilizer reservoir could contribute to postoperative inflammation or infection after LASIK (Ophthalmology 2001). Therefore, at the end of each day, the reservoir chamber and cap should be cleaned with an enzymatic cleaner or any cleaning solution recommended by the manufacturer. If tubing is present, it should be changed periodically. The staff should establish a procedure for specifying the frequency of change and for performing epidemiologic cultures to test the growth of microorganisms periodically for excessive overgrowth. The team should culture the interior of the sterilizer reservoir as well as the rim of the unit to survey growing microorganisms.

When the team acquires a new sterilizer, it is important to test it with several cycles of operation before actually applying the cleaned instruments to patients. New sterilizers are sometimes treated with different sprays or silicone materials that can build up and cause problems during surgery. Therefore, before putting a new sterilizer to service, the clinical engineering department or service company should perform the facility procedure for testing the equipment. The test should be completed for three consecutive routine cycles, and each cycle should have a satisfactory physical functioning with a negative biological indicator result. Also, the chemical indicator or integrator on the test tray should show safe parameters.

Monitoring Sterilization
There is considerable information on how to monitor sterilization, which includes mechanical, physical, biological, or chemical indicators, or integrating chemical integrators. A combination of these is ideal to assure sterility of the instruments and functioning of the sterilizer. This can only be achieved with standardized methods of sterile processing that render a device or instrument free of microorganisms.

Sometimes flash sterilization, which is a very brief sterilization on an item, is performed on instruments. Flash-sterilized items are for immediate use, and wrapped trays that are flash-sterilized should be differentiated in the operating suite from unwrapped trays that are conventionally sterilized. Open trays and containers can be used where the potential for contamination is minimal.

Location of the Sterilizer
The sterilizer must be located adjacent to the OR suite. Sometimes, because of space limitations the laser is located at a distance from where the instruments are sterilized, and the instruments can become contaminated during transportation. The staff must also follow the principles of asepsis for transferring open trays. The overall bioburden must be reduced and the sterile technique observed to obtain sterility for these instruments.

Not to Be Forgotten
The sterilizer is an integral part of the laser procedure. We can have the most sophisticated equipment, including the smallest flying spot wavefront-guided excimer laser, but if we do not have an aseptic environment or properly sterilized instruments for the procedure, it's a recipe for disaster. It behooves the surgeon and the team to educate themselves, or to have someone with the requisite knowledge in this area to inspect their setup to make sure their environment can be as sterile as possible for the patient. The American Society of Ophthalmic Operating Room Nurses has organized a task force to try to build consensus on the most appropriate steps to eliminate contamination and maintain a safe LASIK environment. Adherence to the recommendation of this and other groups can help promote LASIK as a safe and often miraculous medical procedure.

Terrence P. O'Brien, MD, serves as Associate Professor of Ophthalmology at the Wilmer Ophthalmological Institute of Johns Hopkins University School of Medicine as Director, Refractive Eye Surgery, and Director, Ocular Infectious Diseases. Dr. O'Brien may be reached at (410) 583-2842; tobrien@jhmi.edu