Institute of Optometry 2005

Infection control and a review of a selection of ocular infections less commonly seen in optometric practice

Dr Simon Barnard

Infection control

Definitions

Infectious Agent

A microbial organism with the ability to cause disease. The greater the organism's virulence (ability to grow and multiply), invasiveness (ability to enter tissue) and pathogenicity (ability to cause disease), the greater the possibility that the organism will cause an infection. Infectious agents are bacteria, virus, fungi, and parasites.

Reservoir

A place within which microorganisms can thrive and reproduce. For example, microorganisms thrive in human beings, animals, and inanimate objects such as water, table tops, and doorknobs.

Portal of exit

A place of exit providing a way for a microorganism to leave the reservoir. For example, the microorganism may leave the reservoir through the nose or mouth when someone sneezes or coughs. Microorganisms, carried away from the body by faeces, may also leave the reservoir of an infected bowel.

Mode of transmission

Method of transfer by which the organism moves or is carried from one place to another. The hands of the health care worker may carry bacteria from one person to another.

Portal of entry

An opening allowing the microorganism to enter the host. Portals include body orifices, mucus membranes, or breaks in the skin. Portals also result from tubes placed in body cavities, such as urinary catheters, or from punctures produced by invasive procedures such as intravenous fluid replacement.

1 Institute of Optometry 2005

Susceptible host

A person who cannot resist a microorganism invading the body, multiplying, and resulting in infection. The host is susceptible to the disease, lacking immunity or physical resistance to overcome the invasion by the pathogenic microorganism.

Cross infection

Patients receiving treatment within an optometric environment are at risk of contracting an infection from another patient or from the optometrist, dispensing optician or contact lens fitter. Such an unexpected outcome can arise from contact with the practitioner’s hands or from equipment used to examine the eye. The courteous act of shaking hands with a patient is sufficient to transfer organisms so that hand washing between examining patients, preferably with an antiseptic soap, is considered important (Seal et al, 1998).

Hand washing

For effective hand washing  Nails should be kept short and clean with no nail varnish  Jewellery should be kept to a minimum (e.g., one ring)  Watches and bracelets should be removed  Sleeves should be rolled up  Cuts or abrasions should be covered

“Social” hand washing should always be carried out before handling food or drink, after toilet use, and before or after social contact with a patient.

Soaps that have antiseptic properties include 4% chlorhexidine (Hibiscrub) or 10% povidone iodine (Betadine scrub). Hibiscrub is only bactericidal whereas Betadine is bactericidal and viricidal.

Hands should be washed before carrying out clinical procedures on any patient. Hibiscrub should be used but is permissible to us an alcohol hand washes alternately. In the event of examining a patient with a viral eye disease, it is advisable to hand wash afterwards with Betadine.

Tonometer heads

Disposable heads are available but not always preferred for accuracy. If not using a disposable, Goldmann tonometry should be added to your risk register if a decision is made to use a conventional cone. Alternatives are non-contact techniques and electronic instruments such as Pascal.

2 Institute of Optometry 2005

After use, a tonometer head should be wiped with a paper towel and placed in a galley pot of Milton (hypochlorite) at 10ppm for a minimum of 10 minutes (30 minutes in the presence of an adenovirus outbreak). Change galley pot and solution each day. And soak cone in new solution before use.

Gonioscopes and contact fundus lenses

These can pose problems where there are plastic haptics bonded to a lens. The 4-mirror Volk glaucoma lens is a one piece that may be disinfected using the Milton regime above with the lens rinsed in sterile saline, dried and stored after use.

Slit lamp microscope

Wipe head and chin rests with disposable alcoholic wipe between patients

Eye drops

Use single dose units e.g., Minims

Lacrimal syringes

Single use disposable canulae should be used.

Instruments for corneal foreign body removal

Sterile disposable hypodermic needles may be used. If using surgical blunt spud this should be cleaned and disinfected with Milton and then autoclaved.

3 Institute of Optometry 2005

4 Institute of Optometry 2005

Risk register

If an optometrist determines that the risk to patients of carrying out a procedure using a disinfection regime that is less than optimal is minimal, it is permitted to do so. There is no need to inform the patient but the optometrist must have in the practice a Risk Register.

For a risk register the practice will have to describe the nature of the risk, give it some form of evidence based description and /or rating and give an explanation of why the guidelines in relation to the risk are not being followed. It should also be stated explicitly what those guidelines are and how the local procedure is different. e.g., Tonometry

Risk: Transmission of infection, organic debris on tonometer prism.

Risk description and/or rating: here have some form of evidence relating to transmission and quantify the risk in your practice. Only the people working in the practice can do this as they know best the working systems in the environment. Examples may be the Royal College Guide, particularly in our case www.site4sight.org.uk/quality/rgov/guidelines/cjd.htm#2 or the DOH's Transmissible spongiform encephalopathy agents: Safe working and the prevention of infection AND HSC Variant CJD minimising the risk of transmission, both available from www.doh.gov.uk

A clear statement of current guidelines: This should be clear and brief to demonstrate that you are aware of what the most current best practice guidance is. Also include manufacturers guidelines (e.g., of the prisms). Do the national and manufacturer guidelines match? If not how do they differ?

A statement of local policy: Again be clear and state what you are going to do locally. State how your local policy/procedure differs from current guidelines.

Next is the final and most important part. JUSTIFY THE DIFFERENCE BETWEEN WHAT YOU DO AND WHAT THE GUIDELINES RECOMMEND YOU DO. If possible support this with one good piece of current research.

Points to note:

Remember that the guidelines are only guidelines. They do represent a statement of best practice but unless they are pieces of legislation we are not obliged by law to adhere to them. Having said that one would need a solid explanation of why there was any deviation from them. This is where the risk register comes in. It simply shows that an assessment has been made and

5 Institute of Optometry 2005 consideration given before the decision was taken to have a local practice not recommended in current guidelines.

A risk register is not a legal document. It is a local record. It may be in any format. It is best to use a consistent template for each risk (JP Nolan, 2005, personal communication)

HIV and AIDS

Immunosuppression leads to many possible opportunistic infections and ocular or neuro-ocular manifestations occur in approximately 1% of HIV positive patients but become considerably more prevalent in AIDS.

Ocular manifestations include

 HIV or AIDS retinopathy o Cotton wool spots o Retinal haemorrhages o Ischaemic macular oedema  Cytomegalovirus retinopathy o Vision threatening o The most common severe ocular manifestation of AIDS affecting a large minority of patients o White granular lesions near juxta-papillary large vessel arcades o These coalesce and the destruction spreads outwards with necrosis and haemorrhages which, untreated engulf the retina in six months  Acute retinal necrosis syndrome  Toxoplasmosis retinopathy (more common as a neurologic manifestation)  Histoplasmosic retinopathy  Kaposi sarcoma (commonly conjunctival)  Papilloedema  Opportunistic disseminated choroiditis

Neurologic manifestations include

 Cerebral toxoplasmosis  CNS lymphoma  Cerebral toxoplasmosis  Meningitis  Visual field loss

When examining an HIV or AIDS patient the optometrist must be aware of the wide range of possible ocular and neurological signs that may be present.

6 Institute of Optometry 2005

Trachoma

This infection is caused by TRIC organisms (chlamydia trachomatis species) and is one of a series of oculogenital diseases

 Trachoma  Neonatal chlamydial disease  Adult inclusion conjunctivitis

Trachoma is endemic in underdeveloped countries and certain ethnic groups. Trachoma is seen in the UK amongst new immigrants.

Signs & symptoms

 Symptoms are usual absent in non-corneal forms  Moderate to severe upper tarsal follicles  Conjunctival papillary hypertrophy and moderate to severe infiltration of superior palpebral conjunctiva o Grading scheme

1. Follicles without scarring or papillae 2. Follicles with papillary hypertrophy 3. Scarring with follicles 4. cicatrical scarring replacing follicles

 Superior cornea and upper lid secondarily involved and scarred o Trichiasis and entropion o Superficial epithelial keratitis o Superior pannus o Ulceration o Limbal follicles and subsequent depressed scarring (Herbert pits)

Patient risk management

Impress on the patient the need for hygiene; treat family members with topical tetracycline

Treatment

Oral tetracycline 250 mg for 3 to 6 weeks; topical tetracycline.

7 Institute of Optometry 2005

Demodicosis

This is caused by demodex follicularum an arachnid mite that lives in hair follicles and sebaceous glands. The organism is endemic in older adults and there is some evidence to show a correlation (but not cause) with acne rosacea. Excessive numbers produce toxic or hypersensitive marginal type reaction.

Symptoms and signs of demodicosis include acute itchiness of the eyelids especially on awakening and tubular/pyramidal collarettes extending from the base of lash.

Treatment of demodicosis

Lid scrubs and ointment (e.g., Vaseline) applied liberally, at night to the eye lids should be prescribed for 10 days with a review after that period. After resolution, continued regular lid hygiene should be carried out.

Pediculosis

There are a number of species of lice that may infest humans including pediculosis corporis, pediculosis capitis, and pthirius pubis.

They may be transmitted by direct contact or through contaminated bed linen etc.

Symptoms and signs of lice include itching and burning of the eyelids, a crusty appearance to lid margins as well as the presence of lice and nits.

Treatment of lice

The nits and lice should be removed with forceps or debride with alcohol soaked cotton-wool bud. Vaseline should be applied to lids tid for 5 days to smother the organisms. Lice specific shampoo and careful combing to rid scalp should be recommended. The patient should be reviewed after 5 days

Toxocariasis

Toxocariasis is an infestation caused by a common intestinal roundworm of cats (Toxocara cati) and dogs (Toxocara canis). Human infestation is due to accidental ingestion of soil or food contaminated with roundworm eggs which are shed in dog or cat faeces. Young children who play in the vicinity of dogs and who ingest dirt are particularly at risk. According to Kanski (1992) surveys have shown that the prevalence of infestation in puppies 2-6 months of age is greater than 80%.

8 Institute of Optometry 2005

Once in the human intestine, the ova develop into larvae which penetrate the gut wall and travel to the liver, lungs, skin, brain and eye. The larvae die and cause inflammatory responses:

 Visceral larva migrans o Severe systemic infection commonly at around age 2-years o Fever, pneumonitis and convulsions (if brain affected)  Ocular Toxocariasis o Patient otherwise healthy o Average age of patient at diagnosis is 7 years

Ocular manifestations may be a chronic endophthalmitis-like picture which has a poor prognosis due to cyclitic membranes and retinal detachment

More commonly, peripheral granuloma and posterior pole granulomas occur and these can be devastating if the macular is affected.

Patient risk management

 Avoid exposure to kittens or pregnant cats  Avoid exposure to puppies  Wash hands after handling cat or puppies

Treatment

 If close to macula, diethylcarbamazine.

Toxoplasmosis

Toxoplasmosis is caused by toxoplasma gondii, an intracellular protozoan parasite that produces either a congenital or acquired retinochororoiditis as well as neurologic manifestations (Alexander, 1994). Infestation is a widespread infection with around 25% of the world’s population either being infected or have been infected. Prevalence is as high as 90% in some areas (Seal et al, 1998).

There are three forms. In the host, the cat, the parasite is in the intestine as a spore contained in oocysts. These oocysts are excreted in cat faeces.

In the intermediate host the parasite may exist as a tachyzoite which is the proliferative form, or as a bradyzoite which is an encysted form.

The toxoplasmic protozoa enters the human eye via the circulatory system and then locates within the nerve fibre layer. This potentiates a possible retinochoroiditis but if resistance is high the organism may encyst itself within the infected cell and remain viable for many years. The bradyzoite may exist asymptomatically for several years in the inner retina but if there is

9 Institute of Optometry 2005 immunocompromise they may multiply, liberate tachyzoites and producing a hypersensitivity reaction manifesting itself as “headlights in the fog” (Alexander, 1994).

Recurrent attacks of congenital toxoplasmosis retinitis can occur a few times over the life of a patient with retinal scarring after each attack. The patient may present with blurred vision or floaters, visual field defects secondary to optic nerve head inflammation or red eye secondary to uveitis.

Patient risk management

 Avoid exposure to kittens or pregnant cats  Wash hands after handling cat  Ensure meat is fully cooked  Thermal death point of toxoplasma is 56° C  Salad vegetables should be washed before ingestion

Treatment

 Active retinitis must be treated if macula is threatened  Sulfonamides; steroids; pyrimethamine; clindamycin

Loa Loa

Loiasis is caused by the filarial nematode worm Loa loa which is transmitted to humans by day-biting Chrysops flies and which infects the skin and eyes.

Human loiasis geographical distribution is restricted to the rain forest and swamp forest areas of West Africa, being especially common in Cameroon and on the Ogowe River. Humans are the only known natural reservoir. It is estimated that 2-13 million humans are infected with the Loa loa larvae. It is occasionally seen in the UK.

Once inside the body the infective larvae develop slowly into a mature adult (the process takes about a year). During this period it lives and moves around the fascial layers of the skin. In periods of growth and development Loa loa often makes frequent excursions through the subdermal connective tissues where it is often noticed by the host. Once they reach maturity (measuring 3-3.4 cm x 0.35- 0.43 mm for males and 5.7 x 0.5 mm for females) the adults mate and produce sheathed microfilariae 298 x 7.5 micrometers in size.

The microfilariae are diurnally periodic in synchrony with their vector and once they reinfect a fly they undergo two stages of growth into infective larvae (in about 10 days time) which can then be transmitted back to humans.

10 Institute of Optometry 2005

Most of the pathological problems observed in people infected with Loa loa are connected to periods when the migrating adult worms appear near the surface of the skin. The worms often appear around the eye where they can be easily seen and extracted before they damage the conjunctiva.

Immune reactions to the migrating worms can also cause calabar swellings in the arms and legs. Recurrent swelling can lead to the formation of cyst like enlargements of the connective tissues around the tendon sheaths. These swellings can be extremely painful when moved. Dying worms can also cause chronic abscesses followed by granulomatous reactions and fibrosis. (Acknowledgement: Filiarial Genome Network).

Presumed Ocular Histoplasmosis

This is a fungal infection caused by Histoplasma capsulatum. The disease is acquired by inhalation and the spores pass via the blood stream to the spleen, liver and occasionally, the choroid. It is particularly prevalent in the Ohio- Mississippi River Valley but occasionally is seen in the UK.

POHS is asymptomatic unless it causes a maculopathy. Fundus lesions include small white/yellow atrophic spots scattered in the mid periphery and posterior pole; peripapillary atrophy; linear streaks of chorioretinal atrophy; and subretinal Choroidal neovascularisation

Acknowledgements

Thanks to JP Nolan, Specialist Nurse and the Institute of Optometry for infection definitions and hand washing graphics.

References and bibliography

Alexander L (1994), Primary Care of the Posterior Segment, Appleton & Lange. Norwalk

Filarial Genome Network (1996) Loa loa: a cutaneous filarial parasite of humans http://maven.smith.edu/~sawlab/fgn/pnb/loaloa.html

Kanski JJ (1992) Clinical Ophthalmology, Butterworth Heinemann, Oxford

Seal DV, Bron A, Hay J (1998) Ocular Infection. Investigation and Treatment in Practice, Martin Dunitz, London

For details of the Institute of Optometry Additional Supply and Supplementary Prescriber course which leads to GOC registration and includes a module infection control please contact [email protected]

11