Computational study on the effects of central retinal blood vessels with asymmetric geometries on optic nerve head biomechanics.

Optic nerve head (ONH) biomechanics are associated with glaucoma progression and have received considerable attention. Central retinal vessels (CRVs) oriented asymmetrically in the ONH are the single blood supply source to the retina and are believed to act as mechanically stable elements in the ONH in response to intraocular pressure (IOP). However, these mechanical effects are considered negligible in ONH biomechanical studies and received less attention. This study investigated the effects of CRVs on ONH biomechanics taking into consideration three-dimensional asymmetric CRV geometries. A CRV geometry was constructed based on CRV centerlines extracted from optical coherence tomography ONH images in eight healthy subjects and superimposed in the idealized ONH geometry established in previous studies. Mechanical analyses of the ONH in response to the IOP were conducted in the cases with and without CRVs for comparison. Obtained results demonstrated that the CRVs induced anisotropic ONH deformation, particularly in the lamina cribrosa and the associated upper neural tissues (prelamina) with wide ranges of spatial strain distributions. These results indicated that the CRVs result in anisotropic deformation with local strain concentration, rather than function to mechanically support in response to the IOP as in the conventional thinking in ophthalmology.

Fundus examination using a wide-angle viewing system and intraocular illumination through the corneal incision during cataract surgery: a case series.

PURPOSE: To report a new technique for fundus examination using a wide-angle viewing system combined with intraocular illumination without accessing the vitreous cavity. STUDY DESIGN: Retrospective case series METHODS: Consecutive patients with atopic dermatitis-related cataracts who underwent standard cataract surgery and the novel fundus examination technique were included. After phacoemulsification, the anterior and posterior chambers were filled with ocular viscoelastic devices. A 27-gauge endo-illumination probe was inserted into the anterior chamber through a corneal incision made for cataract surgery. The fundus examination was performed with a wide-angle viewing system and scleral indentation. If any retinal breaks/detachments were detected, they were treated simultaneously. Finally, an intraocular lens was implanted. RESULTS: Ten patients (13 eyes) were included (mean age 26.8 years; 9 men). Retinal breaks were detected in 5 eyes (38%); 2 of the 5 had rhegmatogenous retinal detachment (RRD) (15%). Intraoperative cryopexy was performed for 3 eyes with retinal breaks, while 2 eyes with RRD underwent a scleral buckling procedure (SBP) during the same surgery. There were no intra- or postoperative complications, including posterior capsule damage. The average surgical time was 22 minutes for cases requiring only fundus examination and about 28 and for eyes with cryopexy and 80 minutes for SBP. CONCLUSION: The described technique may reduce the disadvantages of creating scleral incisions and provide comparable visibility to inserting the illuminator into the vitreous cavity.

Association of Bergmeister Papilla and Deep Optic Nerve Head Structures With Prelaminar Schisis of Normal and Glaucomatous Eyes.

PURPOSE: To investigate factors associated with the severity of prelaminar schisis (PLS) in heathy subjects and glaucoma patients. DESIGN: Prospective cross-sectional study. METHODS: A total of 217 eyes of 217 subjects (110 normal eyes and 107 open angle glaucoma eyes) were studied. Frequency and severity of PLS were compared between normal and glaucomatous eyes. Multivariate logistic models were used to assess factors associated with the severity of PLS. Factors considered were age, axial length, glaucomatous damage indices, Bruch membrane opening (BMO) and anterior scleral canal opening parameters, tractional forces (posterior vitreous staging and presence of Bergmeister papilla), circumpapillary choroidal thickness, lamina cribrosa (LC) parameters, and peripapillary scleral (PPS) angle. RESULTS: The frequency of PLS was 70.9% in normal eyes and 72.0% in glaucomatous eyes. There was no difference in frequency and severity between the groups. The presence of Bergmeister papilla was the strongest predictor of a more severe PLS in both normal and glaucomatous eyes (odds ratio [OR] + 9.78, 12.5; both P < .001). A larger PPS angle in normal eyes (OR = 1.19; P = .003) and a larger BMO area and a deeper LC depth in glaucomatous eyes (OR = 1.08, 1.05; both P = .038) were associated with severity of PLS. CONCLUSIONS: The severity of PLS was strongly associated with the presence of Bergmeister papilla, suggesting a traction-related phenomenon. Correlation of PLS severity with larger BMO area and deeper LC depth, which are optic nerve head structures associated with glaucoma, suggested its possible relationship with glaucomatous damage.

Effects of Deep Optic Nerve Head Structures on Bruch's Membrane Opening- Minimum Rim Width and Peripapillary Retinal Nerve Fiber Layer.

PURPOSE: To explore the effects of deep optic nerve head (ONH) structures on Bruch's membrane opening (BMO)-minimum rim width (MRW) and peripapillary retinal nerve fiber layer thickness (pRNFLT) in healthy eyes. DESIGN: Prospective cross-sectional study. METHODS: Two hundred five healthy eyes of 141 subjects (mean ± standard deviation of age and axial length (AXL): 46.9 ± 10.0 years and 24.79 ± 1.15 mm) were enrolled. Best fit multivariable linear mixed models identified factors associated with BMO-MRW and pRNFLT. Explanatory variables included age, gender, AXL, BMO and anterior scleral canal opening (ASCO) area and ovality, magnitude of BMO and ASCO shift, peripapillary choroidal thickness, lamina cribrosa (LC) parameters, prelaminar thickness, and peripapillary scleral (PPS) angle. RESULTS: Thinner BMO-MRW was associated with older age, smaller ASCO/BMO offset magnitude, larger BMO area, thinner prelaminar thickness, deeper LC, and thinner pRNFLT (P = .011, <.001, .004, <.001, <.001, <.001 respectively). Thinner pRNFLT was associated with shorter AXL, smaller ASCO area, a more posteriorly bowed PPS, shallower LC and thinner BMO-MRW. (P = .030, .002, .035, .012, <.001 respectively) CONCLUSIONS: BMO-MRW and pRNFLT were influenced by several deep ONH structures such as BMO and ASCO position shift, BMO or ASCO area, prelaminar thickness, PPS bowing and LC depth in addition to patient characteristics such as age and AXL. The degree and/or direction of associations varied between deep ONH structures and BMO-MRW or pRNFLT. Despite both BMO-MRW and pRNFLT being surrogate parameters for RGC loss, a complex relationship with ONH deep-layer morphology was indicated.