Updates on the utility of anterior segment optical coherence tomography in the assessment of filtration blebs after glaucoma surgery.

The formation of filtration blebs is the main drainage mechanism for reducing intraocular pressure after traditional incisional glaucoma surgery such as trabeculectomy and non-penetrating deep sclerotomy. Early and short-lasting blebs may also occur after canaloplasty. Bleb formation also plays an important role after the implantation of glaucoma drainage devices, including Minimally Invasive Glaucoma Surgery devices. Anterior segment optical coherence tomography (AS-OCT) is a rapid and non-invasive high-resolution imaging technique that has evolved in recent years to become a routine examination. Anterior segment optical coherence tomography (AS-OCT) provides key information in the assessment and follow-up of glaucoma surgery, especially in the assessment of filtration blebs. Thus, bleb morphology can be qualitatively classified into diffuse, cystic, encapsulated and flattened, and AS-OCT imaging can also provide several quantitative parameters of the bleb, such as total bleb height, bleb fluid-filled cavity height, bleb wall thickness, number of microcysts and trabeculectomy opening size. These parameters could have an impact on clinical management during follow-up because they may predict the success or failure of the surgery in the early and late postoperative periods. Additionally, they may also guide the procedures used to increase filtration and reduce intraocular pressure, such as bleb needling and laser suture lysis.

Assessment of the anterior scleral thickness in central serous chorioretinopathy patients by optical coherence tomography.

PURPOSE: To assess the anterior scleral thickness (AST) and describe the presence of a visible supraciliary space (SCS) in central serous chorioretinopathy (CSC) patients by swept-source optical coherence tomography (SS-OCT). STUDY DESIGN: Cross-sectional comparative study. MATERIAL AND METHODS: Three groups were studied: 1) 64 eyes of 54 patients with CSC with persistent subretinal fluid (SRF); 2) 42 fellow eyes of CSC patients without SRF; 3) 65 eyes of 65 controls matched by age, sex and axial length (AL). The AST was measured in the temporal and nasal quadrants at 0, 1, and 2 mm from the scleral spur by SS-OCT. The presence of a visible SCS was also assessed. RESULTS: No differences were observed in the AST0 among the three groups (p≥ 0.665). The temporal AST1 was significantly thicker in the CSC group (530.3 ±67.1 µm) than in the controls (505.5 ±73.9; p=0.041). Mean AST2 was also thicker in the CSC group and the fellow eyes both for the temporal (519.4 ±89.1 µm and 519.8 ±98.5 µm respectively) and nasal quadrants (564.2 ±124.9 µm and 570.5 ±131.0 µm) than in the controls (450.1 ±76.8 and 473.3 ±111.6 µm) (all p≤0.001). A visible SCS was detected in the eyes of 8 CSC patients, in 4 fellow eyes and only in 1 control eye. CONCLUSIONS: AST measured by SS-OCT was significantly greater in CSC eyes than in healthy eyes. Also, a visible SCS was detected in CSC eyes. Thus, thicker sclera in CSC eyes could be associated with the physiopathology of this disease.

Assessment of lower tear meniscus measurements obtained with Keratograph and agreement with Fourier-domain optical-coherence tomography.

AIMS: To compare intraobserver repeatability and interobserver and intersession reproducibility of lower tear meniscus height measurements (LTMH) obtained with the new Keratograph 5M and a Fourier-domain optical-coherence tomography (OCT; Spectralis OCT) and to assess the agreement between the two devices. METHODS: This is a observational cross-sectional study. Thirty eyes of 30 normal subjects were randomly imaged twice with both devices in our setting. Two examiners randomly made LTMH measurements using the devices. To assess intraobserver repeatability and interobserver and intersession reproducibility within-subject SD (Sw), test-retest repeatability, coefficient of variation (CoV) and intraclass correlation coefficients (ICCs) were calculated. Agreement between both devices was also determined. RESULTS: Average LMTH for Keratograph was 235.46±57.61 µm, whereas the mean LTMH measured by OCT was 245.84±67.18 µm. Intraobserver repeatability and interobserver and intersession reproducibility were moderate with Keratograph (CoV ≥0.16%, ≥0.19%, ≥0.17% and ICC ≤0.83, ≤0.76, ≤0.83, respectively) and high for the Spectralis OCT (CoV ≤0.13%, ≤0.12%, ≤0.11% and ICC ≥0.9, ≥0.92, ≥0.92, respectively). No statistically significant difference was detected in mean LMTH measurements made with both devices, although correlation was low (CoV 0.25%, ICC 0.55). CONCLUSIONS: Spectralis OCT LTMH measurements were more reliable than the new Keratograph data. Agreement between the devices was poor.