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Tonometer prism sterilisation: A local and UK national survey

Aman Chandra a, Allon Barsam b, Christopher J. Hammond a,*

a West Kent Eye Centre, Princess Royal University Hospital, Farnborough, Kent BR6 8ND, UKb Department of Ophthalmology, Queen Mary’s Hospital, Sidcup, Kent DA14 6LT, UK

bstract

urpose: First to audit local adherence to a protocol of use of an alcohol wipe for each tonometry, and secondly to assess current practice

ationally in the UK.

ethod: The audit was carried out at two units: The West Kent Eye Centre at the Princess Royal University Hospital (Orpington, UK) and

ueen Mary’s Hospital (Sidcup, UK). The standard set for this audit was 100% sterilisation. During a 1-week period in November 2005, the

umber of alcohol wipes was counted in each consultation room after outpatient clinics, with the doctors being assessed blind to the survey.

he number of Goldman applanation tonometry intra-ocular pressures recorded by each clinician was counted by inspection of the medical

ecords of patients seen.

Secondly, departments listed in the UK Directory of Training Posts were contacted by telephone and the senior nurse was interviewed.

hey were asked directly about their department’s tonometer prism sterilisation and management.

esults: The local audit showed only 54% of tonometry measurements were associated with sterilisation using an alcohol-impregnated wipe.

he national survey included 140 of the 152 UK training departments. Thirty-three (23.6%) departments used disposable tonometer prisms

outinely. The remaining 107 (76.4%) used non-disposable prisms. Eighty-five (60.7%) departments provided sodium hypochlorite for prism

terilisation, with 69 (81.2%) of these departments providing more than one prism/clinician to allow full exposure to the disinfectant. Twenty-

wo (15.7%) departments used alcohol wipes. Only 8 (7.5%) of the 107 departments using non-disposable prisms tracked these prisms, despite

oyal College of Ophthalmologists guidelines that they should be. These same 8 (7.5%) departments replaced the non-disposable prisms as

er manufacturer guidelines. 19.3% of charge nurses were aware of a policy for tonometry in patients with, or at risk of, prion disease.

onclusions: This study highlights that sterilisation of tonometer prisms was inconsistent in a local audit. Nationally, practices were varied.

he majority of ophthalmology departments continued to use non-disposable tonometer prisms, but few seemed aware of the Royal College of

phthalmologists’ recommendation that disposable prisms are used in patients at risk of prion disease, and few track tonometer heads or

eplace them according to manufacturers guidelines. Use of disposable tonometer prisms would seem to reduce concerns about sterilisation, as

ell as prevent spread of common pathogens.

2007 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

www.elsevier.com/locate/clae

Contact Lens & Anterior Eye 31 (2008) 13–16

eywords: Tonometer; Prisms; Sterilisation; Audit; Survey

1. Introduction

Tonometer prisms are an integral part of ophthalmic

examination. They are known to be a potential vector in

iatrogenic transmission of pathogens [1]. Prion disease such

as Creutzfeld–Jacobs Disease (CJD) is of particular concern,

and applanation tonometer prisms have been suggested as a

possible source of infection [2]. As the United Kingdom

may be an area of relatively high risk, the Royal College

* Corresponding author. Tel.: +44 1689 865682; fax: +44 1689 863329.

E-mail address: chammond@btopenworld.com (C.J. Hammond).

367-0484/$ – see front matter # 2007 British Contact Lens Association. Publi

oi:10.1016/j.clae.2007.07.004

of Ophthalmologists (RCOphth) guidance advises use of

disposable tonometers for patients either diagnosed, at

risk of, or suspected of prion disease, but fall short of

recommending disposable tonometer prisms for all patients.

It is suggested that non-disposable prisms should be wiped

and disinfected between use, and should not be moved

between individual clinical stations so any outbreaks may be

tracked easily [3]. Manufacturers recommend that their

tonometer prisms be replaced after 100 uses, though the

extent of adherence to this guidance is not known.

The aim of this study was twofold. The first aim was to

audit the rate of sterilisation of non-disposable tonometer

shed by Elsevier Ltd. All rights reserved.

A. Chandra et al. / Contact Lens & Anterior Eye 31 (2008) 13–1614

prisms in two District General Hospital (DGH) ophthalmol-

ogy departments. The second aim was a national survey of

UK ophthalmology departments to assess current sterilisa-

tion practice, to identify policies regarding tonometer

prisms, and in particular whether there were local policies

in place for patients with possible CJD.

2. Method

The two DGH departments included in the audit

recommend wiping the tonometer head after each Goldmann

applanation tonometry (GAT) with a single 70% isopropyl

alcohol-impregnated swab, followed by wiping the prism

with a dry tissue. The West Kent Eye Centre at the Princess

Royal University Hospital (Orpington, UK) has around

25,000 ophthalmology outpatient attendances per annum,

and Queen Mary’s Hospital (Sidcup, UK) sees similar

numbers of patients. The standard set for this audit was

100% tonometer prism sterilisation. During a 1-week period

in November 2005, the number of alcohol wipes was

counted in each consultation room after outpatient clinics,

with the doctors being assessed blind to the survey (to avoid

change of practice during the audit). The number of GAT

intra-ocular pressures recorded by each clinician was

counted by inspection of the medical records of patients

seen during the session. Results of individual doctors

were anonymised, but the grade of clinician was recorded. It

was assumed that alcohol wipes were only used for the

purpose of cleaning tonometer prisms. Doctors involved in

the clinics were asked about this after the week of data

collection, and none could recall any other occasion they had

used these.

For the second part of the survey, departments listed in

the UK Directory of Training Posts were contacted by

telephone and an interview with the senior nurse manager in

charge of the clinic was arranged at a time convenient to

him/her. Four direct questions were asked:

� W

hat is your department’s method of tonometer prism

sterilisation?

� I

f you use non-disposable tonometer prisms, did you track

them?

� D

o you replace your tonometer prisms as per manufac-

turer guidelines?

� A

re you aware of a local protocol for tonometry for

patients with, or at risk of, CJD?

Fig. 1. Local audit results showing the proportion of Goldmann applanation

tonometry measurements when a 70% isopropyl alcohol-impregnated swab

was used.

3. Results

3.1. Local audit

The total number of patients who had had their intra-

ocular pressures (IOP) measured was 203. The total number

of alcohol wipes used was 110 (54% of IOPs). Therefore, the

number of patients who had their IOPs measured without

the use of alcohol wipes was at least 93 (46%) (Fig. 1).

This differed between different grades of doctors. The

non-consultant grade doctors measured 165 patient’s GAT

intra-ocular pressures and used 79 alcohol wipes (47.9%).

Consultants measured 38 patients’ GAT intra-ocular

pressures and used 27 alcohol wipes (71.1%).

3.2. National survey

For the survey, interviews were conducted with the senior

nurse in 140 (92%) of the 152 ophthalmology departments

listed in the Directory of Training Posts.

With regard to their methods of sterilisation, 107 (76.4%)

departments used non-disposable tonometer prisms routi-

nely. Sodium hypochlorite was used in 85 (60.7%) depart-

ments and 69 (81.2%) of these departments provided more

than one prism/clinician to allow full exposure to the

disinfectant. Alcohol wipes were used in 22 (15.7%)

departments. Non-disposable prisms were tracked by eight

departments (7.5%). These same 8 (7.5%) departments

replaced their prisms as per guidelines. Disposable tono-

meter prisms were used in the remaining 33 (23.6%)

departments (Fig. 2). Twenty-seven (19.3%) of the surveyed

were aware of a protocol for prion risk patients.

4. Discussion

The local audit showed a very disappointing compliance

with local guidance, as the number of alcohol swabs

identified for only 54% of patient GAT measurements,

assuming the number of alcohol wipes correlates with each

disinfection. Although use of alcohol wipes for tonometer

prism disinfection was not directly observed, the doctors

audited did not recall any other reason for use, and we

believe there were no missed swabs in the count, supporting

the assumption. The results compare poorly to the Aizman

et al. study [4], which showed 100% sterilisation with

alcohol pads. While time constraints in busy clinics and

ignorance of epidemiological principles may have played a

role, these results have been reported to the clinicians, and a

subsequent reaudit 6 months later (again, with clinicians

A. Chandra et al. / Contact Lens & Anterior Eye 31 (2008) 13–16 15

Fig. 2. Methods of tonometer sterilisation used in UK national survey of

ophthalmology departments.

blinded to the audit while it was under way) showed

improved adherence to guidelines.

In the UK national survey, almost a quarter of

departments (23.6%) used disposable tonometer heads

routinely. The remaining three quarters provided reusable

GAT prisms, 60.7% of the departments sampled used

sodium hypochlorite, and 15.7% of departments used

disposable alcohol swabs between patient contacts. Ton-

ometer prisms have been shown to be vectors for

transmission of epidemic keratoconjunctivitis (EKC) [2].

Sterilisation of instrumentation abruptly ends EKC out-

breaks [5]. Soaking GAT prisms in 500 parts per million of

sodium hypochlorite (NaOCl) for 10 min has been shown to

destroy adenovirus 8 [6], herpes simplex, enterovirus 70 and

most bacteria [7]. Wiping tips with swabs impregnated with

70% isopropyl alcohol has also been shown to be effective in

removing adenovirus 8 [6] and most other common ocular

viral and bacterial pathogens [8]. Although Hepatitis C

nucleic acid has been detected on tonometer tips after

sterilisation with wiping with a 70% isopropyl ethanol swab,

it is not thought to confer infectivity [9]. There is therefore

ample evidence that these two methods of sterilisation

are adequate alternatives in routine practice to prevent

transmission of common pathogens. The majority (81.4%)

of departments using hypochlorite confirmed that more than

one tonometer prism was provided per clinician, to allow

adequate exposure to the cleaning solution.

Haag-Streit, the manufacturers of the tonometer prisms

most widely used in the UK, recommends a maximum of

100 uses per prism. However only 7.5% of departments

regularly monitored their tonometer head use, and therefore

followed manufacturer instructions. Although this is most

probably due to the financial implications of regular

tonometer replacement, this low figure may also reflect

ignorance of this guidance.

Regarding prion disease, only 19.3% of charge nurses in

this survey were aware of a departmental protocol in

accordance with RCOphth recommendations that disposable

tonometers are used for any patients at risk of CJD. While

prion disease is rare, and there are no reported cases of prion

disease transmission via GAT, the resistance of prions to

conventional sterilisation methods is the reason for this

cautious advice. Wadsworth et al. [10] found no detectable

concentrations of prion protein in the anterior segments of

eyes from patients with sporadic and variant CJD-appreci-

able concentrations were found only in their retinae and

optic nerves. The risk of transmission via tonometry

therefore seems theoretical, but this survey suggests the

majority of ophthalmology departments have poor knowl-

edge of the guidance regarding those subjects at risk.

Although charge nurses were surveyed in this study, rather

than the medical staff, it seems likely that if the nurse in

charge was unaware of a protocol, then the doctors would

also have been unaware.

In studies of residual epithelial cells on tonometer heads

(which are increased in patients on topical medication), the

biggest reduction is found by wiping the tonometer head

with a tissue which should be performed for all non-

disposable prism GAT, even when using sodium hypo-

chlorite solution [11]. However, importantly, no method

completely removed debris; and therefore none completely

eliminated the risk from transmission of pathogens,

including prion disease.

Desai et al. [12]. showed close agreement between results

using reusable tonometer and disposable prisms. An

alternative method of using a disposable latex cover over

the tonometer head has also been shown to give accurate

results [13]. In busy clinics, this may however impinge

unacceptably on time constraints. Disposable prisms would

therefore seem the preferable alternative.

As has been shown by this survey, there is incomplete

sterilisation of tonometer prisms. Even if carried out, there

is debate as to whether complete elimination of corneal

epithelial debris occurs with any method. In addition,

ophthalmology departments across the UK do not seem to

adhere to manufacturer guidelines for tonometer heads. The

use of disposable prisms currently seems the most effective

method of reducing cross contamination. Although dis-

posable prisms are currently recommended for use in

patients at risk of prion disease, their real benefit may lie in

prevention of transmission of other, more common,

pathogens. The majority of UK ophthalmology training

departments do not seem to have a well-publicized policy for

patients at risk of prion disease. A simpler recommendation

for the use of disposable prisms in all clinical cases may be

easier to follow, and have further reaching benefits. Our

survey has shown that 23.6% of UK training ophthalmic

departments have incorporated such devices in their daily

clinics. Perhaps the rest should follow suit.

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