Abstract
Purpose: :
To report long–term activity and outcome in a sympathetic ophthalmia (SO) cohort and calculate needed sample size for future studies comparing classic immunosuppressive therapy with biological immunomodulating antibodies
Methods: :
Retrospective cohort study (n=20) of patients with SO. Activity, therapy and visual acuity at 1,3,5 and 10years post onset was studied. Statistical analysis of parameter variability was performed to determine future study sample size for different ranges of power (P), outcomes and follow–up times.
Results: :
55% (n=11) of patients developed SO after ocular surgery without previous trauma, 45% (n=9) had a history of ocular trauma. Male–female ratio was 13 : 7. Mean age at onset of SO was 46.1y (range 9–81.5y), with a delay of 5.8y (range 0.1–36.6y) after the original trauma or last ocular surgery. Mean follow up was 6.8y (range 1–31y). All patients were treated with systemic steroids and in 50% steroid sparing 2nd line immunosuppressive agents (cyclosporine,methothrexate, azathioprine, chlorambucil) were added.
Snellen Visual Acuity at 1, 3, 5 and 10 years post onset was 0.51±0.34 , 0.50±0.37, 0.49±0.41 and 0.35±0.30 respectively (mean ± standard deviation). The prevalence of legal blindness was 10 % at 1y and increased to 25% at 10y post onset.
Of all active episodes noted in the cohort (n= 74), 34% had taken place before the end of the first year of follow–up, 70% before the third, and 85% before the fifth year of follow–up.
In one of four patients followed over 10 years, two active episodes occurred 15y and 18y post onset of SO.
For a power of 0.80, a study evaluating a new treatment that would reduce legal blindness in SO by 50% at 5 years post onset should include 70 patients.
Conclusions: :
In accordance to previous studies, the original event in SO has shifted from trauma to surgery. Contrary to our expectations, ocular surgery without previous trauma as the initial cause of SO was higher in the male than female population (62% vs. 14%). Although more (55% at 5 years) patients with SO retain driving vision (snellen 0.5) using steroids and steroid sparing agents, 25% of patients still become legally blind. Sympathetic Ophthalmia may be more active in the first 5 years post onset, but occasional flare ups occur up to 18y post onset and warrant long–term follow–up. Based on this cohort study, given the important spread of visual acuity at set time points and the variable intervals between active episodes, a future study to validate superiority of new drugs in this rare disease should at least include 70 patients, pointing towards a multi–centre approach.
Keywords: uveitis-clinical/animal model • visual acuity