Using anterior segment optical coherence tomography to compare the smoothness of anterior iris surface between two eyes in unilateral Fuchs' uveitis syndrome

Iridian anterior segment OCT in rubella uveitis syndrome and cytomegalovirus anterior uveitis: a comparative study

PURPOSE

To compare iris affectation in cytomegalovirus anterior uveitis (CMVAU), rubella virus-associated uveitis (RVU), and healthy contralateral eyes, using swept-source anterior segment optical coherence tomography (SS-AS-OCT).

MATERIALS AND METHODS

A comparative, transversal, retrospective study examining 60 eyes from 30 patients-18 eyes (17 patients) with CMVAU, 14 eyes (13 patients) with RVU, and 28 healthy eyes-was performed. Six-millimeter cross-sectional SS-AS-OCT B-scans were obtained in each iris quadrant. Images were exported to ImageJ®. Qualitative and quantitative analyses were done: stromal thickness (ST), smooth index (SI), and optical density (OD) of pigment epithelium. Comparisons between measurements and clinical-demographic parameters were performed using SPSS®.

RESULTS

Qualitative analysis showed extensive damage in iris stroma but was unable to differentiate between both uveitis. RVU eyes had a lower mean ST (315.72 μm ± 42.4) compared to those with CMVAU (348.6 μm ± 46) (p = 0.047) and a lower ST in the upper (338.9 μm ± 38.52)/(386.25 μm ± 47.2) (p = 0.005) and temporal (281.5 μm ± 57.3)/(326.43 μm ± 62.3) (p = 0.016) quadrants. Mean (0.94 ± 0.02)/(0.9 ± 0.03) (p = 0.001), temporal (0.94 ± 0.02)/(0.89 ± 0.03) (p < 0.001), and nasal SI (0.094 ± 0.02)/(0.9 ± 0.04) (p = 0.005) were higher in RVU. OD was similar in both uveitis. In healthy eyes, mean ST (376.8 μm ± 39.7) was higher and mean SI was lower (0.87 ± 0.04) than in RVU (p < 0.001) and CMVAU eyes (p = 0.032). Mean OD was higher in healthy eyes (911 ± 130) than in CMVAU eyes (800 ± 200) (p = 0.037).

CONCLUSIONS

The quantitative analysis of the SS-AS-OCT iris images allows for the differentiation between healthy eyes and those with CMVAU and RVU, as well as between both uveitis.

Anterior segment structures in dark iris Chinese patients with unilateral Fuchs' uveitis syndrome

Purpose

To compare binocular anterior segment structures in Chinese patients with dark iris and unilateral Fuchs’ uveitis syndrome (FUS).

Methods

This was a cross-sectional study including 34 phakic eyes (17 patients) with unilateral FUS. Anterior segment parameters were measured by rotating Scheimpflug imaging camera, noncontact specular microscopy, and anterior segment optical coherence tomography.

Results

Corneal volume was higher in FUS eyes compared to unaffected eyes (p < 0.05). The iridocorneal angles were larger in FUS eyes compared to contralateral eyes (p < 0.05). Mean endothelial cell density (ECD) was lower, and the coefficient of variation in endothelial cell size and average cell area of endothelial cells (ACA) were higher, in FUS eyes (p < 0.05). Mean densitometry values of the midstromal cornea (zones with a diameter of 0–2, 2–6, or 10–12 mm), posterior (0–2, 2–6, 10–12, or 0–12 mm), or total thickness (0–2 or 2–6 mm) were higher in FUS eyes compared with unaffected eyes (p < 0.05). ECD, percentage of hexagonal cells, and ACA were strongly related to densitometry values of the midstromal and posterior cornea in the FUS eyes (p < 0.05). Smoothness index of iris was lager in affected eyes (p < 0.05).

Conclusion

In Chinese patients with unilateral FUS, loss of endothelial cells, wider iridocorneal angle, thicker cornea, higher corneal densitometry of midstromal and posterior layer, and smoother iris were observed in affected eyes compared to contralateral eyes. These data can help to elucidate anterior segment characteristics of unilateral FUS in this population.

Automated measurement of iris surface smoothness using anterior segment optical coherence tomography

Fuchs uveitis (FU) is a chronic and often unilateral ocular inflammation and characteristic iris atrophic changes, other than heterochromia, are common in FU and are key to the correct diagnosis in many cases. With the advent of anterior segment optical coherence tomography (AS-OCT), some investigators attempted to quantitatively study these atrophic changes; mostly by introducing various methods to measure iris thickness in AS-OCT images. We aimed to present an automated method in an observational case series to measure the smoothness index (SI) of the iris surface in AS-OCT images. The ratio of the length of the straight line connecting the most peripheral and central points of the anterior iris border (in nasal and temporal sides) to the actual length of this border on AS-OCT images, was defined as SI. In a uveitis referral center, twenty-two eyes of 11 patients with unilateral Fuchs uveitis (FU) (7 female) and 22 eyes of 11 healthy control subjects underwent AS-OCT imaging. Image J and a newly developed MATLAB algorithm were used for manual and automated SI measurements, respectively. Agreement between manual and automated measurements was evaluated with Bland–Altman analysis and interclass correlation coefficient. The inter-eye difference of SI was compared between the FU group and the control group. Automated mean overall SI was 0.868 ± 0.037 and 0.840 ± 0.039 in FU and healthy fellow eyes, respectively (estimated mean difference =  − 0.028, 95% CI [− 0.038, − 0.018], p < 0.001). Bland- Altman plots showed good agreement between two methods in both healthy and FU eyes. The interclass correlation coefficient between the manual and automated measurements in the FU and healthy fellow eyes was 0.958 and 0.964, respectively. The inter-eye difference of overall SI was 0.029 ± 0.015 and 0.012 ± 0.008 in FU group and control group, respectively (p = 0.01). We concluded that the automated algorithm can rapidly and conveniently measure SI with results comparable to the manual method.

Quantitative Analysis of the Iris Surface Smoothness by Anterior Segment Optical Coherence Tomography in Fuchs Uveitis

OBJECTIVE

To demonstrate the value of "smoothness index (SI)" as a novel tool for quantitative analysis of iris surface findings in unilateral Fuchs' uveitis (FU).

METHODS

Both phakic eyes from patients with unilateral FU as well as healthy control subjects underwent anterior segment optical coherence tomography (AS-OCT). The ImageJ software was used for calculating the SI.

RESULTS

Forty eyes from 20 patients with unilateral FU and 40 eyes from 20 healthy subjects were enrolled. In FU eyes, mean overall SI (0.876 ± 0.030) was significantly higher than fellow control eyes (0.841 ± 0.041) (p = .001). Mean inter-eye difference for overall SI in the FU patients (0.037 ± 0.030) was significantly larger than the healthy control subjects (0.018 ± 0.014) (p = .033).

CONCLUSION

Iris "smoothness index" can be used to quantitatively assess iris surface smoothness and may facilitate the diagnosis of subtle iris atrophic changes in eyes affected by FU especially in the absence of heterochromia.