Meibomian Gland Morphology: The Influence of Structural Variations on Gland Function and Ocular Surface Parameters.

PURPOSE: To objectively and quantitatively characterize meibomian gland morphology and to investigate the influence of morphological variations on gland function and ocular surface and tear film parameters. METHODS: One hundred fifty subjects were enrolled. The examinations included tear osmolarity, tear meniscus height, bulbar conjunctival hyperemia, noninvasive tear film breakup time, lid margin thickness, foam secretion, meibomian gland expressibility, count of functioning glands, corneal and conjunctival staining, fluorescein breakup time, lid wiper epitheliopathy, and Schirmer test. Patient symptoms were assessed using the Ocular Surface Disease Index questionnaire. Images from noncontact meibography were analyzed using an automated method that objectively estimates dropout area, number of glands, gland length and width, and gland irregularity. RESULTS: Gland irregularity highly correlated with dropout area (r = -0.4, P < 0.001) and showed significant partial correlations with fluorescein breakup time (r = 0.162, P = 0.049) and the Ocular Surface Disease Index questionnaire (r = -0.250, P = 0.002) Subjects with dropout area <32% were divided into 2 groups: high and low irregularity. Gland expressibility was statistically significantly different between the 2 groups (U = 319.5, P = 0.006). In the high irregularity group, gland irregularity correlated with the Schirmer test (r = 0.530, P = 0.001) and corneal fluorescein staining (r = -0.377, P = 0.021). CONCLUSIONS: Automated morphological analysis of meibomian gland structure provides additional quantitative and objective information regarding gland morphology. The link between dropout area and gland function is not clear. Assessment of gland irregularity might better predict gland function and its effects on ocular surface and tear film parameters.

A Novel Automated Approach for Infrared-Based Assessment of Meibomian Gland Morphology.

PURPOSE: We present and validate a new methodology for analyzing, in an automated and objective fashion, infrared images of the meibomian glands (MG). METHODS: The developed algorithm consists of three main steps: selection of the region of interest, detection of MG, and analysis of MG morphometric parameters and dropout area (DOA). Additionally, a new approach to quantify the irregularity of MG is introduced. We recruited 149 adults from a general population. Infrared meibography, using Keratograph 5M, was performed. Images were assessed and graded subjectively (Meiboscore) by two experienced clinicians and objectively with the proposed automated method. RESULTS: The correlation of subjective DOA assessment between the two clinicians was poor and the average percentage of DOA estimated objectively for each Meiboscore group did not lie within their limits. The objective assessment showed lower variability of meibography grading than that obtained subjectively. Additionally, a new grading scale of MG DOA that reduces intraclass variation is proposed. Reported values of MG length and width were inversely proportional to the DOA. Gland irregularity was objectively quantified. CONCLUSIONS: The proposed automatic and objective method provides accurate estimates of the DOA as well as additional morphologic parameters that could add valuable information in MG dysfunction understanding and diagnosis. TRANSLATIONAL RELEVANCE: This approach highlights the shortcomings of currently used subjective methods, and provides the clinicians with an objective, quantitative and less variable alternative for assessing MG in a noninvasive and automated fashion. It provides a viable alternative to more time-consuming subjective methods.

Lamina Cribrosa Depth and Shape in Glaucoma Suspects. Comparison to Glaucoma Patients and Healthy Controls.

Purpose: To evaluate the lamina cribrosa depth and shape parameters in glaucoma suspects compared to glaucoma patients and healthy controls. Materials and Methods: A total of 325 subjects (120 with primary open-angle glaucoma, 103 glaucoma suspects and 102 healthy controls) were included. Serial horizontal B-scan images of optic nerve head were obtained using enhanced depth imaging of the optical coherence tomography. For each of the 325 subjects, lamina cribrosa position was measured manually in 16 horizontal B-scans, hence 5200 scans in total were analyzed. In particular, lamina cribrosa depth (LCD), lamina cribrosa deflection depth (LCDD), lamina cribrosa shape index (LCSI), and its horizontal equivalent (LCSIH) were estimated. Along lamina cribrosa parameterization, intraocular pressure, visual field, central retinal thickness, retinal nerve fiber layer thickness, and disc and neuroretinal rim areas were also measured. Results: LCD was statistically significant different (P < .001) in glaucoma patients when compared to glaucoma suspects and heathy controls (603 ± 172 µm versus 554 ± 114 µm and 531 ± 115 µm, respectively). Similarly, LCDD was statistically significant different (P < .001) in glaucoma patients when compared to glaucoma suspects and heathy controls (250 ± 78 µm versus 213 ± 54 µm and 211 ± 58 µm, respectively). No statistically significant differences were found in LCSI (P = .957). However, LCSIH showed statistically significant differences between healthy controls and glaucoma suspects (P = .003) and between healthy controls and glaucoma patients (P = .006). Conclusions: The deformation of LC in glaucoma suspects, in terms of LCSIH, was not statistically different from that of glaucoma patients. LCD does not have the potential to discriminate glaucoma suspects from healthy controls.

A Fully Automated 3D In-Vivo Delineation and Shape Parameterization of the Human Lamina Cribrosa in Optical Coherence Tomography.

OBJECTIVE: A fully automated method for delineation of the lamina cribrosa in optical coherence tomography (OCT) is proposed. It assesses the three-dimensional (3D) shape of the lamina cribrosa in-vivo, based on a series of OCT B-scans. METHODS: The algorithm has several image processing steps and it is based on active contour detection performed along three orthogonal directions of the B-scan data cuboid. Further, the delineated 3D lamina cribrosa shape is parameterized with a fourth-order polynomial of two variables [Formula: see text] using the least-squares method. Datasets from a total of 255 subjects from three groups were analyzed: 92 primary open angle glaucoma patients, 77 glaucoma suspects, and 86 controls. RESULTS: Statistically significant differences were found in the coefficients of monomials xiyj, with both i and j even, between patients and controls and between suspects and controls. CONCLUSIONS: From the data obtained, it can be concluded that the mean shape parameterization of the lamina cribrosa of glaucoma suspects has similar appearance to that of glaucoma patients but it is markedly different from that of healthy controls. SIGNIFICANCE: The proposed algorithm enables automatically estimating, for the first time, the lamina cribrosa in 3D, further providing clinicians with a time-efficient discrimination tool supporting glaucoma diagnosis.

Fully automated detection of lamina cribrosa in optical coherence tomography: Framework and illustrative examples.

We present an algorithm for automated detection of lamina cribrosa (LC) using optical coherence tomography scans. To the best of our knowledge, it is the first algorithm of this type, as previous attempts relied heavily on characteristic points marked a priori by a human expert and were hence semi-automated at best. First, we highlight the unwanted, yet unavoidable, influence of image rescaling necessary to provide the detection algorithm with real-world image proportions. Next, we simulate an LC phantom and test the influence of various combinations of the rescaling method and SNRs on the LC detection efficacy. Finally, we present some illustrative results from real-data analysis.