Retention of corneal epithelial cells following Goldmann tonometry: implications for CJD risk

Abstract

Aims: To assess the adequacy of current decontamination methods for the Goldmann tonometer in the context of variant Creutzfeldt-Jakob disease (vCJD). Methods: Reusable Goldmann tonometer prisms were used to perform applanation tonometry on different groups of patients. Following tonometry, retained materials were collected from the tonometer prism head and examined using cytological methods. The used tonometers were subjected to a series of conditions to evaluate their effect on the residual cell numbers found on the tonometer heads. These included wiping alone and wiping or washing followed by disinfection of the tonometer prism. The effect on cell counts of drying the prism overnight was studied, as well as drying overnight and then wiping and disinfecting. All disinfections were performed with sodium hypochlorite (0.05% w/v). Results: The cytology specimens of 69 patients were studied. Patients using eye drops regularly desquamated significantly more corneal epithelial cells with Goldmann tonometry than patients not using regular eye drops. The mean number of cells was 156 (range 0-470) for patients using eye drops and 14 (4-57) for patients not using eye drops (p = 0.004). Wiping or washing the tonometer head reduced the cell number significantly but neither method completely eliminated cells. The two methods were not significantly different (p=0.3). Drying left a large number of cells (23-320 cells). Conclusions: Retained corneal epithelial cells, following the standard decontamination routine of tonometer prisms, may represent potential prion infectivity. Manual cleaning was the most important step in reducing epithelial cell retention.

Minimal cross-infection risk through Icare rebound tonometer probes: a useful tool for IOP-screenings in developing countries

“…24 The Icare tonometer probe has a diameter of 1.7 mm and surface area of approximately 4.6 mm During measurement with the Goldmann tonometer, the cornea is flattened and the entire anterior surface is in contact with both the tearfilm and the corneal epithelium. In contrast, the Icare probes are accelerated against the cornea and rebound.…”

Tonometer disinfection practice in the United Kingdom: A national survey

“…23,24 This leads to reduced clarity of the corneal contact rings, causes corneal epithelial disturbance and may potentially harbour epithelial cells and microbes, making them harder to eradicate during disinfection. 7,25 A 70% isopropyl alcohol wipe causes similar, but less severe structural damage. 23,26 Of the disinfection methods available, immersion in 3% hydrogen peroxide has been found to be the least abrasive, followed by 0.5% sodium hypochlorite.…”

“…5 Although there have been no documented cases of transmission of these via contaminated ophthalmic equipment, hepatitis B infection following exposure of the ocular surface to infectious material has been demonstrated in a primate. 6 More recently, corneal epithelial cells 7 and proteinaceous material 8 have been found to be retained on the tonometer head following decontaminaton of the prism using standard cleaning and disinfection regimes. This has been proposed as a potential source of CreutzfeldtJakob disease (CJD) transmission, the infectious agent being the prion protein.…”

A comparison of clinical performance between disposable and Goldmann tonometers

“…15,16 However, relatively few studies have been conducted assessing the reliability of disposable tonometers, none yet featuring the Tonojet.…”