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Since the deformation of structures in the optic nerve head (ONH) is associated with glaucoma and other diseases of the optic nerve, measurement of this deformation is of current research interest. This paper considers the computation of cup depth, a measurement of the depth of the internal limiting membrane (ILM). The computation of cup depth requires a reference structure against which to measure the ILM, and the construction of two reference structures is discussed, one based on Bruch's membrane opening (BMO) and the other based on the anterior surface of the peripapillary sclera (AS). A main focus of the paper is the robust computation of mean cup depth, which requires a good sampling of a reconstruction of the ILM surface. To evaluate our algorithm, the construction of synthetic datasets is considered.

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PURPOSE: This study examined the peripapillary choroidal thickness (PCT) in nonarteritic ischemic optic neuropathy (NAION) in comparison to contralateral eyes and normal eyes. METHODS: We used enhanced depth imaging spectral-domain optical coherence tomography to image the optic nerve head of 20 NAION, 10 contralateral eyes, and 102 normal eyes. Following compensation, the scans were manually delineated to identify relevant surfaces including Bruch's membrane opening (BMO), Bruch's membrane, and anterior sclera. The PCT was defined as the measurement between Bruch's membrane and the anterior sclera and was measured at increasing distance from BMO. Models adjusted for age, BMO area, and axial length were used to compare the mean PCT between NAION and normal eyes, and contralateral eyes and normal eyes. Paired t-tests were used to compare the PCT between NAION and contralateral eyes. RESULTS: The mean PCT was thicker in NAION and contralateral eyes when compared with normal eyes at all distances from BMO (P < 0.001). The PCT was not significantly thicker in contralateral eyes when compared with affected NAION eyes. Choroidal thickness was thinnest in the inferior quadrant in all eyes regardless of the group. CONCLUSIONS: Increased peripapillary choroidal thickness was noted in both NAION and contralateral eyes. The thicker choroid may be an associated feature or a result of the disorder. Although further longitudinal study is required to determine causation, these findings may suggest that a thickened peripapillary choroid may be a component of the disk-at-risk clinical phenotype.

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PURPOSE: To assess if the in vivo mechanical displacement of the anterior laminar cribrosa surface (ALCS) as a response of an acute elevation in intraocular pressure (IOP) differs in individuals of European (ED) and African descent (AD). METHODS: Spectral-domain optical coherence tomography (SDOCT) scans were obtained from 24 eyes of 12 individuals of AD and 18 eyes of 9 individuals of ED at their normal baseline IOP and after 60 seconds IOP elevation using ophthalmodynamometry. Change in depth (displacement) of the LC and to the prelaminar tissue (PLT) were computed in association with the change (delta) in IOP (Δ IOP), race, age, corneal thickness, corneal rigidity (ocular response analyzer [ORA]), and axial. RESULTS: In the ED group for small IOP elevations (Δ IOP < 12 mm Hg), the ALCS initially displaced posteriorly but for larger increase of IOP an anterior displacement of the lamina followed. Inversely, in the AD group the ALCS did not show a significant posterior displacement for small Δ IOP, while for larger IOP increases the ALCS significantly displaced posteriorly. Posterior displacement of the lamina cribrosa (LC) was also significantly correlated with longer axial length, higher corneal thickness, and ORA parameters. Prelaminar tissue posteriorly displaced for any magnitude of Δ IOP, in both groups. CONCLUSIONS: The African descent group demonstrated a greater acute posterior bowing of the LC after adjustment for age, axial length, Bruch's membrane opening (BMO) area, and ORA parameters. Greater PLT posterior displacement was also seen in the AD group with increasing IOP, which was tightly correlated with the displacement of the LC.

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PURPOSE: This study examined the association between peripapillary choroidal thickness (PCT) with age and race in a group of African descent (AD) and European descent (ED) subjects with normal eyes. METHODS: Optic nerve head images from enhanced depth imaging spectral-domain optical coherence tomography of 166 normal eyes from 84 subjects of AD and ED were manually delineated to identify the principal surfaces of Bruch's membrane (BM), Bruch's membrane opening (BMO), and anterior sclera (AS). Peripapillary choroidal thickness was measured between BM and AS at increasing distance away from BMO. The mean PCT was compared between AD and ED subjects and generalized estimating equation (GEE) regression analysis was used to examine the association between race and PCT overall, in each quadrant, and by distance from BMO. Models were adjusted for age, BMO area, and axial length in the regression analysis. RESULTS: Overall, the mean PCT increased from 63.9 µm ± 18.1 at 0 to 250 µm to 170.3 µm ± 56.7 at 1500 to 2000 µm from BMO. Individuals of AD had a greater mean PCT than those of ED at all distances from BMO (P < 0.05 at each distance) and in each quadrant (P < 0.05 in each quadrant). Results from multivariate regression indicate that ED subjects had significantly lower PCT compared to AD overall and in all quadrants and distances from BMO. Increasing age was also significantly associated with a lower PCT in both ED and AD participants. CONCLUSIONS: Peripapillary choroidal thickness varies with race and age, as individuals of AD have a thicker peripapillary choroid than those of ED. (ClinicalTrials.gov number, NCT00221923.).

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PURPOSE: To determine if laminar depth (LD) and prelaminar tissue volume (PTV) are associated with age and race in healthy human eyes. METHODS: Optic nerve head images from enhanced depth imaging spectral-domain optical coherence tomography of 166 normal eyes from 84 subjects of African descent (AD) and European descent (ED) were manually delineated to identify the principal surfaces: internal limiting membrane, Bruch's membrane (BM), anterior sclera (AS), and anterior surface of the lamina cribrosa. These four surfaces defined the LD and PTV using Bruch's membrane opening (BMO) and AS for reference structures. Generalized estimating equations were used to evaluate whether the effect of age on each outcome was differential by race. RESULTS: When age was analyzed as a continuous variable, the interaction term between age and race was statistically significant for mean LDBMO (P = 0.015) and mean LDAS (P = 0.0062) after adjusting for axial length and BMO area. For every 1-year increase in age, the LDAS was greater on average by 1.78 µm in AD subjects and less by 1.71 µm in ED subjects. Mean PTV was lower in the older subjects (1248 × 10(6) µm(3) AD, 881 × 10(6) µm(3) ED) compared to the younger subjects (1316 × 10(6) µm(3) AD, 1102 × 10(6) µm(3) ED) in both groups. CONCLUSIONS: With increasing age, the LD changes differently across racial groups in normal subjects. The LD in ED subjects showed a significantly decreasing slope suggesting that the lamina moves anteriorly with age in this group.

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PURPOSE: This study explores variation in the axial location of Bruch's membrane opening (BMO) to determine if this reference plane varies with age and race. METHODS: There were 168 spectral-domain optical coherence tomography (SDOCT) optic nerve head volumes that were obtained from healthy subjects and manually delineated within 24 axial slices to develop point clouds for Bruch's membrane and anterior scleral surfaces. A BMO-independent reference plane was generated based on the peripapillary sclera to measure BMO position. General estimating equations were used to determine the relationship of the axial position of BMO (BMO height) with choroidal thickness, age, and race (African Descent [AD] versus European Descent [ED]) controlling for variations in axial length. RESULTS: The peripapillary choroid was thinner with increasing axial length (-14.9 µm/mm, P = 0.0096), advancing age (-1.1 µm/y, P = 0.00091), and in the ED group (20.2 µm, P = 0.019) in a multivariable model. Choroidal thickness was also strongly related to BMO height (P < 0.00001) independent of all covariates. Bruch's membrane opening position was more posterior relative to the sclera in older subjects (1.3 µm/y, P = 0.00017), independent of axial length and race. However, when choroidal thickness was included in the model, this association was lost (P = 0.225). There was no significant difference in BMO height between racial groups after adjustment for age and axial length. CONCLUSIONS: Bruch's membrane opening is more posteriorly located in older individuals. These differences are largely due to differences in choroidal thickness and suggest that BMO migrates posteriorly with age due to age-related choroidal thinning. However, additional studies in longitudinal datasets are needed to validate these findings.

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