Why was this Statement needed?
This BTS Clinical Statement was commissioned to support clinicians managing patients with Ocular TB. The current available evidence around this disease is not strong, and so there is not a standard pathway. By developing this Clinical Statement we wanted to provide a consensus view with best practice points to help both TB and Ophthalmic specialists to navigate the presentations of this disease.
Why is there limited evidence on Ocular TB?
Ocular TB accounts for about 1% of all TB cases (1), it can occur without systemic TB presentation and affects different parts of the surface and inside of the eye.
Given the relative number of cases and the number of combinations in which the disease can present itself, it is difficult to conduct research.
However, around 10m people developed active TB in 2020 around the world (2), and hence this is still an important manifestation of TB which clinicians will have to diagnose and manage.
What are the main challenges to diagnosing and treating this infection?
TB in general exists as a spectrum of infection and disease states. Depending on the interaction with the host’s immune response, this can result in clearance of the bacillus, latent infection, subclinical disease, and active disease. This is true for Ocular TB as well, and to complicate things, Ocular TB can also present as a hypersensitivity state secondary to active disease elsewhere in the body.
The infection can affect several different areas of the eye and its surroundings, and there are several ocular infections that can mimic its symptoms, masking a latent TB infection for example. Sampling the ocular structure to conduct tests is also difficult.
Even after diagnosis, treatment can be complex, as several drugs used to treat the infection can be oculotoxic (harmful to the eye), while drugs used to treat other ocular infections can reactivate latent TB.
It is a very complex landscape in which it is difficult to apply standardised pathways and conduct research.
Why is a joint approach involving TB and Ophthalmic specialists so important that you made it your very first best practice point?
This was very much in recognition of the difficulties with making a diagnosis of Ocular TB and that this required a high level of collaboration between TB specialists and Ophthalmologists. The ability to correctly identify the appropriate level of investigation and interpret results of investigations requires both specialists.
Furthermore the combination of anti-inflammatory treatment and TB treatment with potential toxicity from either modality would require both teams to liaise closely.
What are the main areas you looked at in the Clinical Statement?
First we explored the various phenotypes associated with the disease and provided detail of the ocular inflammations more commonly caused by TB, including presentations in immunosuppressed patients.
We then moved to diagnostics, covering the best tests to perform both in the eye and in the respiratory clinics, when Ocular TB is suspected and guiding the clinician in the interpretation of results.
A sizeable section of the Statement is dedicated to treatment of the most common presentations of the disease, for those with confirmed latent disease and considerations on when treatment is better avoided. We also included notes on potential drug toxicity.
Which areas of the Clinical Statement you think will be the most useful to clinicians?
For TB specialists this will centre around the recognised phenotypes of Ocular TB and the complex assessments required to assess outcome and response to therapy. The Statement helps explain that Ocular TB is not merely latent TB but a recognised manifestation of active extrapulmonary disease with serious repercussions for the patient’s sight. It also provides good practice points to help prioritise the urgency by which a TB assessment and initiation of therapy is required.
For Ophthalmologists this Statement highlights the diagnostic tools available to diagnose TB and the limitations and advantages of each mode. It also provides a background to standard TB therapeutic regimens. The Statement provides clarity on the management of latent infection when coincidentally discovered or when this needs addressing in other Ocular diseases requiring immunosuppression.
Where would evidence/research help most in the future management of Ocular TB?
The Statement recognises that an optimal diagnostic imaging modality/modalities for confirming Ocular TB is still unclear and that an evaluation of the currently available tests is required to define a standard diagnostic approach when Ocular TB is suspected.
There is a need to define the optimal duration and composition of TB therapy in Ocular TB and the Statement recommends that this is evaluated.
References
- Dilraj S. Grewal, in Handbook of Pediatric Retinal OCT and the Eye-Brain Connection, 2020 https://www.sciencedirect.com/science/article/pii/B9780323609845000366
- WHO, https://www.who.int/news-room/fact-sheets/detail/tuberculosis, Accessed February 2022.