What is the Spaulding classification and why is it used?

The Spaulding classification is a framework developed by Dr. Earle Spaulding to guide the level of disinfection or sterilization required for medical devices based on their potential to cause infection. Devices in the critical category contact sterile tissues and require sterilization. Semi-critical devices contact mucous membranes or non-intact skin and require high-level disinfection. Non-critical devices contact only intact skin and require low-level disinfection. This tiered approach ensures that resources are used appropriately, applying the highest levels of processing only where the infection risk is greatest.

Why is alcohol wiping of tonometer tips insufficient?

Alcohol (isopropyl or ethyl, 70%) is a low-to-intermediate level disinfectant. It effectively kills many bacteria and lipid-enveloped viruses but does not reliably destroy non-enveloped viruses (such as adenovirus, which causes EKC), mycobacteria, or fungal spores. Since tonometer tips contact the corneal epithelium (a mucous membrane), they are semi-critical devices requiring high-level disinfection. A quick alcohol wipe reduces microbial load but does not constitute HLD. The risk of transmitting EKC via inadequately disinfected tonometer tips in an eye clinic is a real and documented concern.

What is orthophthalaldehyde (OPA) and when is it used?

Orthophthalaldehyde (OPA), sold commercially as Cidex OPA, is a high-level disinfectant used for semi-critical medical devices. It is a less irritating and faster-acting alternative to glutaraldehyde (Cidex). OPA achieves high-level disinfection in 12 minutes at room temperature. It is used for tonometer tips, endoscope components, and other semi-critical instruments. Advantages include low vapor pressure (less odor and irritation than glutaraldehyde) and stability. The main disadvantage is that it stains proteins gray, so any tissue contact (corneal protein) or splashing on clothing or skin can cause gray staining. Instruments must be thoroughly rinsed after OPA exposure.

What are standard precautions and to whom do they apply?

Standard precautions are a set of infection prevention practices applied to every patient at every encounter, regardless of their known or suspected infection status. They treat all blood, body fluids (except sweat), non-intact skin, and mucous membranes as potentially infectious. Core components include: hand hygiene before and after patient contact, use of appropriate PPE (gloves, mask, gown, eye protection) when exposure to blood or body fluids is anticipated, safe handling and disposal of sharps, proper respiratory hygiene and cough etiquette, and appropriate cleaning and disinfection of patient-care equipment and the environment.

How should a tonometer tip be properly disinfected according to CDC guidelines?

The CDC recommends soaking tonometer tips in either 3% hydrogen peroxide or a 1:10 dilution of sodium hypochlorite (bleach) for a minimum of 10 minutes, followed by thorough rinsing with sterile water or tap water and air drying before the next use. Some facilities use 70% isopropyl alcohol wipes followed by at least 5 minutes of air drying, but this does not technically constitute high-level disinfection per the Spaulding classification. A fresh tip for each patient, when feasible, eliminates this concern entirely. Whatever protocol is used should be standardized, documented, and consistently followed.

Equipment Disinfection for the CPO Exam

Proper equipment disinfection is fundamental to patient safety in any ophthalmic practice. Every piece of equipment that contacts patients or is used in the patient environment carries infection transmission risk. Understanding the principles of disinfection, the Spaulding classification, and specific protocols for common ophthalmic instruments is essential CPO knowledge.

The Spaulding Classification

The Spaulding classification categorizes medical devices by their infection risk potential, which determines the required level of disinfection or sterilization:

Category	Definition	Required Processing	Ophthalmic Examples
Critical	Contacts sterile tissue or the vascular system	Sterilization	Surgical instruments, intraocular needles
Semi-critical	Contacts mucous membranes or non-intact skin	High-level disinfection (HLD)	Tonometer tips, trial contact lenses, lid specula
Non-critical	Contacts intact skin only	Low-level disinfection	Slit lamp chin rest, phoropter, frame rulers, trial frames

Tonometer tips contact the corneal epithelium, which is a mucous membrane. They must receive high-level disinfection between every patient, not just wiping with an alcohol swab. The CDC recommends soaking in 3% hydrogen peroxide or 1:10 diluted sodium hypochlorite (bleach) for at least 10 minutes, then thorough rinsing before next use.

Levels of Disinfection

Sterilization

Sterilization destroys all microorganisms including bacterial spores. Methods include:

Steam autoclave (most common for heat-tolerant instruments)
Ethylene oxide gas (for heat-sensitive items)
Dry heat oven

High-Level Disinfection (HLD)

High-level disinfection kills all microorganisms except high numbers of bacterial spores. Used for semi-critical items. Common agents include glutaraldehyde (Cidex), orthophthalaldehyde (OPA/Cidex OPA), and hydrogen peroxide-based products. Contact time must be adequate (product-specific, usually 10 to 20 minutes minimum).

Low-Level Disinfection (LLD)

Low-level disinfection kills most bacteria, some fungi, and some viruses but not mycobacteria or spores. Used for non-critical items. Common agents include diluted bleach solutions, quaternary ammonium compounds (quat), and some 70% alcohol products.

Disinfecting Common Ophthalmic Equipment

Slit Lamp

The chin rest, forehead bar, and joystick (all non-critical items) should be wiped with a low-level disinfectant between patients. The slit lamp should also be wiped before the first patient of the day.

Goldmann Tonometer Tips

Tonometer tips that contact the cornea require HLD. The CDC recommends one of these protocols:

Soak in 3% hydrogen peroxide for 10 minutes, rinse with water, air dry.
Soak in 1:10 sodium hypochlorite (diluted bleach) for 10 minutes, rinse thoroughly, air dry.
Wipe with 70% isopropyl alcohol and allow to completely air dry for at least 5 minutes (less preferred; does not meet HLD definition but is widely practiced as a minimum).

Trial Frames and Trial Lenses

Trial frames and lenses contact only intact skin (non-critical) and can be cleaned with 70% alcohol or a disinfectant wipe. Lenses should be cleaned and inspected for scratches that could distort the refraction result.

A quick alcohol wipe of a tonometer tip between patients is not equivalent to high-level disinfection. It reduces microbial load but does not constitute HLD as defined by the Spaulding classification. This is particularly important given the risk of adenoviral keratoconjunctivitis (EKC), which is highly resistant to alcohol and can be transmitted via tonometer tips.

Standard Precautions

Standard precautions are the minimum infection prevention practices applied to all patients regardless of diagnosis. They include:

Hand hygiene before and after every patient contact (soap and water, or alcohol-based hand rub)
Using gloves when contact with blood, body fluids, or mucous membranes is anticipated
Proper disposal of sharps in designated sharps containers
Using personal protective equipment (PPE) appropriately

Key Takeaways

The Spaulding classification divides devices into critical (sterilization), semi-critical (HLD), and non-critical (LLD) categories.
Tonometer tips are semi-critical and require HLD (hydrogen peroxide soak or diluted bleach soak) between patients, not just alcohol wipes.
Slit lamp external surfaces are non-critical and require low-level disinfection between patients.
Standard precautions apply to all patients regardless of known infection status.
Contact time for disinfectants is critical; products must be used at the correct concentration and for the specified time to be effective.