To the Editor:

We noted the recent use of anterior segment optical coherence tomography (AS-OCT) to quantify anterior chamber inflammation in a pilot study of intravitreal anti-vascular endothelial growth factor agents [1]. The authors reported an incidence of postinjection anterior chamber reaction of 30.5%, as detected on AS-OCT. This is more than 50-fold higher than previous clinical reports using slit lamp based examinations.

The perfect diagnostic tool is able to discriminate between subjects with and without disease. The current gold standard diagnostic for grading anterior chamber inflammation is slit lamp bio-microscopy using the Standardized Uveitis Nomenclature (SUN) inflammatory cell count scoring system. Under this system, “0” (a level denoting disease inactivity) represents no cells seen by the clinician within a 1-mm beam of light at maximal intensity. Crucially, it does not denote the absence of anterior chamber cells.

We have derived the diagnostic accuracy measures, specifically sensitivity, specificity, negative, and positive predictive values (NPV/PPV), from five of the key recent AS-OCT validation studies (Table 1) [2,3,4,5,6]. Figure 1 shows the accuracy metrics of AS-OCT for active inflammation in each of these studies. The consistently high-negative predictive values suggest that AS-OCT would be able to exclude anterior uveitis with high certainty. However, all studies reported detection of free floating cells in eyes which were ‘clinically’ free of inflammation. If one were to directly apply the thresholds provided by the SUN grading to AS-OCT, it would result in overdiagnosis and overtreatment. Further clinical validation and clinical utility work on normal and diseased cohorts is needed for us to understand the clinical relevance of imaging based cell counts.

Table 1 Summary of studies comparing anterior segment OCT grading of anterior chamber inflammation with standard clinical assessment
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Fig. 1
figure 1

Diagnostic accuracy measures from five key anterior segment OCT validation studies [2,3,4,5,6]

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Anterior uveitis is the most common form of uveitis worldwide, and is a common cause of attendance to emergency ophthalmology care. This disease burden combined with a worsening national shortfall of ophthalmologists represents a challenge to care provision. The use of virtual clinics has revolutionized the delivery of glaucoma and age related macular degeneration services. AS-OCT quantification of anterior chamber inflammation could, following further clinical validation work, emerge as a valuable tool for improving the quality and efficiency of clinical service provision.