Adult (>18

years old) patients with AU classified according to the primary anatomic site of the intraocular inflammation [
27] were prospectively recruited from Department of Ophthalmology, St. Olavs University Hospital. Initially 38 patients consented to participate in the study. Their records were reviewed on inclusion and re-reviewed at least 6

months later in order to ascertain correct classification of the AU [
2]. The study was approved by the Regional Ethics Committee in May 2005. It was conducted in accordance with the Declaration of Helsinki recommendations.
AU was defined as the presence of inflammatory cells in the anterior chamber and corneal endothelium and absence of posterior vitreous cells and/or other signs of intraocular inflammation. Inclusion criteria were AU of non-traumatic, non-infectious origin [
28] without clinically recognized posterior segment involvement such as vasculitis, macular edema or optic nerve involvement seen on slit lamp biomicroscopy, best corrected VA (Humphery automatic refractor HARK 597, Dublin, CA) ≥0.2 with spheric equivalent of ±6, and intraocular pressure between 8 and 21

mmHg. Subjects with current or previous ophthalmic history other than AU, significant lens opacities, intraocular lens implants after cataract or refractive surgery, glaucoma or diagnosed diabetes were excluded.
Medical history regarding present and previous eye symptoms, their laterality, duration and treatment was recorded. For the purpose of this study time elapsed from the diagnosis of an AU flare-up was used as an approximation of time elapsed from initial AU flare-up. Symptoms of coexistent spondyloarthropathy, morning muscle stiffness and/or joint pain were asked for. The onset, duration and course of the AU and anterior chamber cells grading was managed according to Standardization of Uveitis Nomenclature [
2]. Laboratory investigations were tailored individually to rule out infectious/ systemic origin/ association of AU. HLA-B27 presence was assessed in all patients, chest x-ray was performed in cases where oral corticosteroids were instituted, sacroiliac spine x-ray was performed if spondyloarthropathy was suspected, and patients with considerable systemic complaints were seen by a rheumatologist.
One patient was excluded due to amblyopic AU eye, one due to previous uveitis-related cystoid macular edema, one due to coexisting pigment dispersion syndrome, one due to abnormal pigmentation in macula of the affected eye. Three eyes of two patients were excluded due to lens implants, and another patient was excluded due to presence of posterior vitreous cells during the follow up period. Both eyes of two patients were excluded due to lens opacities and low OCT signal strength in the affected eye, leaving in total 59 included eyes of 30 patients.
All patients were treated with dexamethasone 0.1% eye drops and mydriatics according to the severity of their AU [
29]. Eight subjects received a short course of oral prednisolone in addition to eye drops, because the AU did not respond promptly or adequately to initial topical treatment. Treatment was tapered down slowly after all clinical signs of AU had gone into remission. Three patients were using immunomodulatory agents which had been instituted before the actual AU episode.
All patients but one (who was Asian) were white. One patient had undergone LASIK surgery in both eyes more then 2

years prior to initial AU episode.
Data from healthy subjects reported by us earlier [
30] were used as controls. Their HLA-B27 status is not known. Controls were age and gender matched to patients: mean age in female patients (n

=

15, 50% females in sample) was 40.7 (SD 12.8) range 19–56. Female controls ≤53

years were included, their mean age was 40.5 (SD 9.7) range 21–53 (n

=

47, 51% females in sample). Mean age in male patients (n

=

15) was 40.3 (SD 13.0) range 21–69 and in male controls (n

=

45, 49% males in sample) was 39.0 (SD 12.0) range 22–63. Controls were further gender-and age matched according to patient subgroups.
OCT (Optic Coherence Tomography STRATUS, Carl Zeiss Meditec, Inc., Dublin, CA) scans in macular thickness protocol (software v.5.0.1) were obtained by a single operator on inclusion and on follow up. Follow up intervals were individually tailored depending on the severity of AU, type of treatment and treatment response, as well as practicability for ophthalmologist and patient. Scans with signal strength ≥3 qualified for inclusion. Scans were qualitatively evaluated as to the presence of epiretinal membrane, vitreomacular traction, cystoid space formation and serous macular detachment. Only one scan was excluded due to cystoid space formation. Mean macular thickness was used in subsequent analyses.
The macula was divided into 9 areas as described in our previous paper [
30]: Mean foveal thickness (MFT

=

F1) from a central macular area of one millimeter in diameter, the inner ring (F2-F5) and the outer ring (F6-F9), each divided into four quadrants. The outer ring diameters measured 2.22 and 3.45 millimeters respectively. Regional variables MCT (mean central thickness) and MPT (mean peripheral thickness) were defined by averaging middle (MCT

=

(F2

+

F3

+

F4

+

F5)/4) and outer (MPT

=

(F6

+

F7

+

F8

+

F9)/4) ring data (Figure ). Averaged mean total macular thickness (MTT) was calculated by averaging the nine macular areas (F1

+

F2

+

F3

+

F4

+

F5

+

F6

+

F7

+

F8

+

F9)/9. The inner region (MFT

=

F1) and mean minimal foveolar thickness (MMFT

=

F0) were also analyzed.
In total 126 scans from both eyes in 29 patients, several of which were repeatedly taken on follow-up were available. Inter-ocular differences between AU-affected and their fellow- eyes were analyzed in relation to time elapsed from AU flare-up.
Cases were grouped in two by time elapsed from flare-up. Early measurement was defined by ≤2

weeks, late measurement by 7–12

weeks follow-up. Scans taken at 3–6

weeks and at long time remission were not included (favoring polarization). In cases where several observations of same subject were available in each group (early or late) the observation with shortest follow-up was chosen. Finally bilateral scans from 21 patients measured early and 8 patients measured late were available. Post-hoc two-sample test was performed on inter-ocular differences in macular thickness by the Mann–Whitney U-test.
For further inclusion in statistical analysis only one bilateral scan from each patient was chosen from 126 scans. In cases where several scans of a same patient were available, the scan taken 1–2

weeks after flare-up was preferred. Finally 59 scans (29 bilateral and one unilateral) from 15 males and 15 females were analyzed.
Normal MTT ranges were defined by MTT ±2SD, stratified by gender in controls; (238.35

μm - 259.33

μm) in females and (243.95

μm - 271.81

μm) in males.
Macular thickness in AU eyes of 30 patients were compared with macular thickness in gender- and age matched controls (n

=

92) (one eye of each subject in both groups) by two-sample Student’s

t-test. Inter-ocular differences in macular thickness between affected and fellow-eyes (n

=

28) were assessed in all patients and in a subgroup with best corrected visual acuity ≥0.8 (n

=

23), by one-sample Student’s

t-tests (expected value

=

0).
Macular thickness in currently quiet fellow-eyes (n

=

28) (defined by no symptoms of AU for at least 3

months prior to assessment) and in a subgroup of fellow-eyes with no previous uveitis (n

=

16) in patients was compared with macular thickness in correspondingly gender- and age matched controls (n

=

85, n

=

77) by two-sample Student’s

t-test.
Inter-ocular differences in macular thickness between AU and their fellow-eyes were compared by HLA-B27 (positive n

=

17 versus negative n

=

8). Inter-ocular differences were also compared between the initial AU episode (n

=

15) and subsequent episodes (n

=

9). Both analyses were carried out in scans taken at

≤

6

weeks from flare-up. A non-parametric test for two independent samples (Mann–Whitney U-test) was used.
SPSS v.17.0 was used for statistical analysis. All tests were two-sided and a p-value

<

0.05 was set to be statistically significant.