Abstract
Purpose:
Posterior scleritis is a less common form of scleral inflammation that can be easily misdiagnosed or overlooked. The physician often uses a patient’s history in conjunction with exam findings and imaging studies to make a clinical diagnosis. Exam findings can be limited. As such, B-scan ultrasonography has become the mainstay in diagnosing posterior scleritis. Current literature often cites the value of 2mm and greater of scleral thickening to diagnose the disease. However, we hypothesize that values less than 2mm on ultrasound are often encountered in symptomatic disease. By using the contralateral eye as a control and updating population norms of scleral thickness, we can enhance the sensitivity of diagnosis with B-scan ultrasound.
Methods:
The retrospective case series study included patients with active posterior scleritis and a control group. All patients were obtained from a uveitis clinic at a tertiary-care center under one provider. Scleral thickness was measured with ultrasound by one trained clinician. Measurements of scleral thickness were made at initial examination using the mean cross-section of the sclera at the posterior pole. Additional anatomical changes were also noted, such as “T-signs” or fluid collection between the optic nerve and sclera, scleral nodules, and optic disc sheath distension.
Results:
Eight patients (16 eyes) were included. Scleral thickness was measured in 81.3% of patients and measurements were reproducible. The scleral thickness in inflamed eyes was 1.94 ± 0.18mm. This was compared to normal data showing thickness of 0.94 ± 0.18mm. A significant difference was seen between the normal mean and patients with posterior scleritis (P value < 0.00001). A subset of patients had one unaffected eye and one affected eye which were compared. The scleral thickness between their two eyes was significantly different (P value of 0.03). Although scleral thickening was evident on the images of all inflamed patients, only five eyes presented with scleral thickness ≤ 2mm. Three eyes presented with T-signs. No eyes showed scleral nodules. One eye showed optic disc sheath distention.
Conclusions:
Our results are consistent with our hypothesis that B-scan ultrasound can be effectively used to observe disease at values less than 2mm. It also opens a dialogue for updated guidelines regarding B-scan ultrasound for posterior scleritis, ultimately to improve the sensitivity of diagnostic testing.