Consulting room laboratory

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Over the coming years, the ability to make diagnostic decisions in practice will become more important. Already, professional fee structures are being redesigned to take into account the many and varied extra skills and services available to the public in, for example, screening for and monitoring diseases, helping with common conditions such as allergy and dry eye and providing specialist vision services such as for certain professions, sport and for the visually impaired.

A new instrument was recently showcased in London in anticipation of a major launch at the BCLA conference at the end of May. The Tearlab, (to be distributed in the UK by Birmingham Optical Group) is an in-house tear sampling and biomarker analysis system which should not only help practitioners assess the tear status of their patients, but may well in years to come aid screening and diagnosis.

The osmolarity of the tears is a useful indicator of the ocular surface physiological state. In dysfunctional tear states, the concentration of solutes within the tears will increase and this leads to subsequent breakdown of the ocular surface. This is followed by the activation of enzyme pathways, leading to an inflammatory cascade in the cornea and conjunctiva. This cycle is self-replicating. An accurate assessment of tear osmolarity is therefore a useful indicator of either current dry eye type states or those that might cause problems in the future, for example in patients thinking of contact lens wear.

The Tearlab unit consists of the main measurement unit and two hand units (Figure 1), each about the size of an electric hair clipper. Onto the hand unit a sterile disposable gold 'Test-Card' is inserted (Figure 2). Upon touching the tear reservoir (no anaesthetic or particular skill beyond a steady hand needed), tears fill 'nanofluidic' channels by capillary action to reach electrodes. On reinserting the hand-held unit back into the main console, a measure of osmolarity is displayed within seconds. The unit then may have a new test card fitted for the next patient.

Having used the instrument I can verify that tear sampling is as easy as it could be and the manufacturers insist that repeatability is acceptable. One might question the need to confirm to somebody already symptomatic that they indeed have dry eye, the development of a quick, but easy and apparently accurate practice-based test offers some exciting potential opportunities. As an add-on test to help predict potential dry eye problems and related contact lens wear problems the instrument should prove a boon to both clinical practice and, assuming an appropriate charging structure, practice profitability. Yet more exciting still, in my opinion, is the potential for further test cards enabling immunoglobulin assessment in predicting and monitoring allergic conditions, or in distinguishing viral from bacterial infective agents in conjunctivitis presentations. The Tearlab osmolarity measurement system is, I suspect, the start of an exciting new area of practice in eye care.

Further details of Tearlab are available from Birmingham Optical Group on 0845 230 3020