Rim Width Research Articles

Changes of Neuroretinal Rim and Retinal Nerve Fiber Layer Thickness Assessed by Optical Coherence Tomography After Filtration Surgery in Glaucomatous Eyes.

PurposeLowering the intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG) with filtration surgery can induce morphological changes to the bulbus and structures of the retina. In this study, we have evaluated changes of Bruch’s membrane-based parameters and retinal nerve fiber layer (RNFL) derived by spectral-domain optical coherence tomography (SD-OCT) in eyes that have undergone glaucoma filtration surgery.Patients and MethodsSD-OCT imaging of the optic nerve head (ONH) and of the RNFL was performed in 54 eyes of 54 patients with medically uncontrolled POAG before and after IOP-lowering surgery (trabeculectomy or deep sclerectomy). The ONH parameter minimum rim width (MRW) and the size of the Bruch’s membrane opening (BMO-Area) were derived from 24 radial B-scans centered on the ONH.ResultsThe average preoperative IOP was 23.1 ± 7.5 mmHg. One month postoperatively, the average IOP decreased to 12.1 ± 4.6 mmHg (p < 0.01), which caused a significant increase in the thickness of neuroretinal rim. There was no significant change in the automatically detected BMO-Area (p = 0.32). The pressure-related increase in MRW correlated well with the postoperative IOP and cup-to-disc ratio (CDR). In regression analysis, the alteration in thickness of the neuroretinal rim could be well predicted in a model including CDR, change of IOP and mean deviation (MD) (R2 = 0.414, p < 0.001). RNFL showed a significant increase as well.ConclusionIOP-lowering surgery in patients with medically uncontrolled POAG causes an increased thickness of the SD-OCT derived ONH parameters. The changes of the RNFL after surgery showed no significant correlations with IOP changes. In contrast to this, highly significant correlations of MRW values with the IOP could be observed. The BMO-Area remained completely stable A preferred use of RNFL for follow-up should be discussed.

Repeatability of Spectral Domain Optical Coherence Tomography Measurements of Bruch's Membrane Opening-Minimum Rim Width in Epiretinal Membrane Patients with Peripapillary Involvement.

The Bruch’s membrane opening-minimum rim width (BMO-MRW) is a recently introduced parameter of the neuroretinal rim. We analyzed the repeatability of spectral-domain optical coherence tomography (SD-OCT) measurements of BMO-MRW in epiretinal membrane (ERM) patients with peripapillary involvement, since the surface around the optic disc is distorted in such patients. BMO-MRW and retinal nerve fiber layer (RNFL) thickness measurements were performed using SD-OCT in prospectively enrolled ERM patients and age-matched healthy control individuals. After two consecutive measurements with a 5 min interval, repeatability was analyzed using the intraclass correlation coefficient (ICC), repeatability coefficient (RC), and coefficient of variation (CV). Fifty-two eyes of 52 ERM patients and 62 eyes of 62 healthy controls were included in the study. The ICCs of the mean BMO-MRW/RNFL thickness measurements were 0.999/0.985 in ERM eyes and 0.999/0.999 in normal eyes, respectively. The RC values of mean BMO-MRW/RNFL thickness measurements were 9.0/6.25 μm in ERM eyes and 4.61/0.92 μm in normal eyes, respectively. The CV values were 0.91% and 1.45% for BMO-MRW and RNFL thickness in ERM eyes, and 0.63% and 0.33% in normal eyes, respectively. In ERM eyes, the RC, CV of average BMO-MRW were 1.9 and 1.4 times greater than those of normal eyes, but 6.8 and 4.4 times greater for average RNFL thickness. BMO-MRW and RNFL thickness showed good repeatability in the diseased eyes with peripapillary involvement and healthy control eyes. Based on the ICC, RC, and CV values, the repeatability of BMO-MRW measurements in peripapillary membrane patients was better than that of RNFL thickness.

The influence of different intraocular pressure on lamina cribrosa parameters in glaucoma and the relation clinical implication

Elevated intraocular pressure (IOP) is one of the main risk factors for glaucoma, and pathological changes in the lamina cribrosa (LC) may play a leading role. This study aimed to explore the influence of different IOP on LC parameters and the correlation between parameters and glaucoma severity. A total of 91 eyes were examined by swept-source OCT and divided into IOP ≥ 30 mmHg (group A), 21 mmHg ≤ IOP < 30 mmHg (group B), and normal IOP (control, group C). Clinical parameters and all LC parameters such as cup depth (CD), lamina cribrosa depth (LCD), prelaminar tissue thickness (PTT) and LC curvature index (LCCI) were used for statistical analysis. The bulk of parameters were greater in group A than in the other groups (group B, P < 0.05; group C, P < 0.001). PTT and Bruch’s membrane opening minimum rim width (BMO-MRW) were thinner in group A than in group C (P < 0.01). In univariate and multivariable linear regression analysis, visual field (VF), mean retinal nerve fiber layer (RNFL) thickness, CD, LCD, PLCSD, PTT, LCCI, aLCCI, and BMO-MRW were significantly correlated with IOP changes (P < 0.05). Pearson test showed that LCD and LCCI were correlated with mean retinal nerve fiber layer (RNFL) thickness (LCD, r = − 0.420, P = 0.002; LCCI, r = − 0.449, P < 0.001) and BMO-MRW (LCD, r = − 0.245, P = 0.019; LCCI, r = − 0.345, P < 0.001). Therefore, different levels of IOP have a remarkable effect on clinical symptoms (VF, BCVA) and LC parameters, between which there may be a linear relationship. LCCI may exhibit a more significant correlation with RNFL thickness and BMO-MRW, which may further suggest that LCCI shows a better correlation with clinical symptoms under the influence of long-term high IOP.

Agonistic autoantibodies against ß2-adrenergic receptor influence retinal microcirculation in glaucoma suspects and patients.

PurposeAgonistic β2-adrenergic receptor autoantibodies (β2-agAAb) have been observed in sera of patients with ocular hypertension and open-angle glaucoma (OAG). They target the β2-receptors on trabecular meshwork, ciliary body and pericytes (Junemann et al. 2018; Hohberger et al. 2019). In addition to their influence on the intraocular pressure, an association to retinal microcirculation is discussed. This study aimed to investigate foveal avascular zone (FAZ) characteristics by en face OCT angiography (OCT-A) in glaucoma suspects and its relationship to β2-agAAb status in patients with OAG.Material and methodsThirty-four patients (28 OAG, 6 glaucoma suspects) underwent standardized, clinical examination including sensory testing as white-on-white perimetry (Octopus G1, mean defect, MD) and structural measures as retinal nerve fibre layer (RNFL) thickness, neuroretinal rim width (BMO-MRW), retinal ganglion cell layer (RGCL) thickness, and inner nuclear layer (INL) thickness with high-resolution OCT. FAZ characteristics were measured by OCT-A scans of superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). FAZ-R was calculated (area FAZ (SVP)/area FAZ (ICP)). Using cardiomyocyte bioassays we analysed serum samples for the presence of β2-agAAb.Results(I) Total mean FAZ area [mm2]: 0.34±0.16 (SVP), 0.24±0.12 (ICP), and 0.49±0.24 (DCP); mean FAZ-R 1.58±0.94. No correlation was seen for FAZ-R with MD, RNFL, BMO-MRW, RGCL thickness and INL thickness (p>0.05). (II) ß2-agAAb have been observed in 91% patients and showed no correlation with MD, RNFL, BMO-MRW, RGCL thickness and INL thickness (p>0.05). (III) FAZ-R correlated significantly with the β2-agAAb-induced increase of the beat rate of cardiomyocyte (p = 0.028).ConclusionFAZ characteristics did not correlate with any glaucoma associated functional and morphometric follow-up parameter in the present cohort. However, level of β2-agAAb showed a significantly correlation with FAZ-ratio. We conclude that β2-agAAb might be a novel biomarker in glaucoma pathogenesis showing association to FAZ-ratio with OCT-A.

EVALUATION OF GLAUCOMA MODULE PREMIUM EDITION IN EGYPT

The mean prevalence of high myopia increases over time in Egypt Prevalence of high myopia in Egypt which was 0.2%, in 1960 increased to 7.4% in 1976 and 10.8% in 2015. Optical coherence tomography (OCT) is a noninvasive, painless and quick precise technology that can be used for interpreting tissue structure and function. Time-domain OCT was fast enough to scan a circle centered on the optic nerve head (circumpapillary) to assess the retinal nerve fiber layer (RNFL) thickness. Glaucoma Module Premium Edition (GMPE) is a new, objective method of ONH analysis using BMO. The termination of Bruch's membrane at the ONH marks the opening through which RGC axons exit the eye to form the choroidal and scleral portions of the neural canal, this anatomic opening, termed Bruch's membrane opening (BMO). The minimum distance from the BMO to the internal limiting membrane represents the most geometrically accurate measurement of neuroretinal rim width. This neuroretinal rim measurement has been termed Bruch's Membrane Opening-Minimum Rim Width (BMO-MRW).

The influence of axial myopia on optic disc characteristics of glaucoma eyes

This study characterizes differences in glaucomatous eyes with and without high axial myopia using custom automated analysis of OCT images. 452 eyes of 277 glaucoma patients were stratified into non (n = 145 eyes), mild (n = 214 eyes), and high axial myopia (axial length (AL) > 26 mm, n = 93 eyes). Optic disc ovality index, tilt and rotation angle of Bruch´s membrane opening (BMO) and peripapillary choroidal thickness (PCT) were calculated using automated and deep learning strategies. High myopic optic discs were more oval and had larger BMO tilt than mild and non-myopic discs (both p < 0.001). Mean PCT was thinnest in high myopic eyes followed by mild and non-myopic eyes (p < 0.001). BMO rotation angle, global retinal nerve fiber layer (RNFL) thickness and BMO-minimum rim width (MRW) were similar among groups. Temporal RNFL was thicker and supranasal BMO-MRW was thinner in high myopic eyes. BMO tilt and PCT showed moderate and temporal RNFL and nasal BMO-MRW showed weak but significant associations with AL in multivariable analyses (all p < 0.05). Large BMO tilt angle and thin PCT are characteristics of highly myopic discs and were not associated with severity of glaucoma. Caution should be exercised when using sectoral BMO-MRW and RNFL thickness for glaucoma management decisions in myopic eyes.

Longitudinal Observation of Border Tissue Configuration During Axial Elongation in Childhood.

PurposeTo investigate the change of border tissue configuration during axial elongation in childhood.MethodsFifty-four subjects (108 eyes; age range, 29.3–132.5 months) who had undergone a series of swept-source optical coherence tomography scans at intervals of 6 months or longer were classified into stable axial length (AXL) eyes (n = 55; AXL change of ≤0.36 mm) and elongating AXL eyes (n = 53; AXL change of >0.36 mm). The angle between the Bruch's membrane opening (BMO) reference plane and the border tissue of Elschnig was defined as the border tissue angle (BTA). The border tissue angle, BMO distance (BMOD) and minimum rim width (MRW) were measured in the temporal and nasal regions.ResultsDuring 15.6 ± 7.2 months of follow-up, the AXL significantly increased from 22.8 ± 1.3 mm to 23.3 ± 1.4 mm (P < 0.001). Changes of border tissue angle and AXL showed a significant correlation only in the temporal region of elongating AXL eyes (r = –0.409; P = 0.002), but not in stable AXL eyes. Both BMOD and nasal MRW significantly increased from 1482.5 ± 153.0 to 1506.1 ± 154.6 µm and from 310.6 ± 83.2 to 324.6 ± 95.6 µm, respectively (all Ps < 0.001). The changes of BMOD and nasal MRW showed a significant positive correlation with changes of AXL in elongating AXL eyes but not in stable AXL eyes.ConclusionsDuring the axial elongation in childhood, temporal border tissue configuration change, BMO enlargement, and nasal peripapillary tissue elevation showed a significant correlation with changes in the AXL.

The Impact of COVID-19 on Individuals Across the Spectrum of Visual Impairment

PurposeTO assess perceptions and implications of COVID-19 infection across the spectrum of individuals with visually impairment (VI) and those with normal sight.DesignProspective cross-sectional comparative study.MethodsSetting: institutional. Patients: 232 patients and their caregivers. Four groups were created based on better eye characteristics: blind (best-corrected distance visual acuity [BCDVA] <3/60 or visual field <10 central degrees); severe VI (BCDVA ≤3/60 to <6/60; vertical cup-to-disc ratio ≥0.85 or neuroretinal rim width ≤0.1); moderate VI (BCDVA ≤6/60 to <6/18); or no or mild VI (controls: BCDVA ≥6/18) based on International Classification of Diseases-10 criteria and Foster and Quigley's consensus definition of glaucoma. Procedure: telephone questionnaires. Main outcome measures: differences in perceptions and implications of COVID-19 infection across various levels of VI. Caregiver perceptions were a secondary outcome measure.ResultsSurveys were completed by 232 participants, with 58 participants in each VI group. Mean age was 58.9 ± 13.2 years old. Greater degrees of VI were associated with older age (P = .008) and lower education level (P = .046). Blind participants more commonly perceived vision as a risk factor for contracting COVID-19 (P = .045), were concerned about access to health care (P <.001), obtained news through word of mouth (P <.001), and less commonly wore masks (P = .003). Controls more commonly performed frequent handwashing (P = .001), were aware of telemedicine (P = .029), and had fewer concerns about social interactions (P = .020) than groups with substantial VI. All caregivers reported more frequent patient care since the COVID-19 pandemic began.ConclusionsThe pandemic might have had a disproportionate impact on the visually impaired, and evidence-based assessments of COVID-19 health outcomes in this population are warranted.

Diagnostic capability of different morphological parameters for primary open\u2010angle glaucoma in the Chinese population

BackgroundTo assess the diagnostic capability of novel Bruch’s membrane opening (BMO)-based disc parameters, the BMO-minimum rim width (BMO-MRW) and the BMO-minimum rim area (BMO-MRA) in the Chinese population and compare them to the retinal nerve fiber layer (RNFL) from optical coherence tomography (OCT) and the rim area (RA) from the Heidelberg retinal tomograph-III (HRT-III).MethodsIn total, 200 eyes of 77 healthy and 123 primary open-angle glaucoma (POAG) subjects were included in this cross-sectional study. All participants underwent the visual field test and structural measurements by OCT and HRT-III. The areas under the receiver operating characteristic curves (AUCs) of different structural parameters were calculated to assess their diagnostic power and compared using the DeLong test.ResultsIn populations with different characteristics, the BMO-MRW and BMO-MRA had better diagnostic power than the RA. In discriminating between all POAG subjects and healthy controls and between early-stage patients and controls, the global BMO-MRW had comparable AUCs with the RNFL, but the BMO-MRA had lower AUCs than the RNFL. In healthy subjects with macrodiscs, both the global and sectoral BMO-MRW were thinner than those in healthy subjects with normal disc size. The AUCs of BMO-MRA, BMO-MRW and RNFL in subjects with macrodiscs were comparable. Additionally, in the myopic population, the BMO-MRA and BMO-MRW had comparable AUCs with the RNFL.ConclusionsThe BMO-MRW had comparable diagnostic power with the RNFL, and compared with BMO-MRW, the BMO-MRA might have advantages in certain populations, such as macrodiscs. All OCT-derived parameters exceeded the RA in diagnostic capability.

Optic Nerve Head and Retinal Abnormalities Associated with Congenital Fibrosis of the Extraocular Muscles.

Congenital fibrosis of the extraocular muscles (CFEOM) is a congenital cranial dysinnervation disorder caused by developmental abnormalities affecting cranial nerves/nuclei innervating the extraocular muscles. Autosomal dominant CFEOM arises from heterozygous missense mutations of KIF21A or TUBB3. Although spatiotemporal expression studies have shown KIF21A and TUBB3 expression in developing retinal ganglion cells, it is unclear whether dysinnervation extends beyond the oculomotor system. We aimed to investigate whether dysinnervation extends to the visual system by performing high-resolution optical coherence tomography (OCT) scans characterizing retinal ganglion cells within the optic nerve head and retina. Sixteen patients with CFEOM were screened for mutations in KIF21A, TUBB3, and TUBB2B. Six patients had apparent optic nerve hypoplasia. OCT showed neuro-retinal rim loss. Disc diameter, rim width, rim area, and peripapillary nerve fiber layer thickness were significantly reduced in CFEOM patients compared to controls (p < 0.005). Situs inversus of retinal vessels was seen in five patients. Our study provides evidence of structural optic nerve and retinal changes in CFEOM. We show for the first time that there are widespread retinal changes beyond the retinal ganglion cells in patients with CFEOM. This study shows that the phenotype in CFEOM extends beyond the motor nerves.

Interconnected drying phenomena in nanoparticle laden water-ethanol binary droplets.

Understanding the evaporation of a multi-component droplet has found immense importance in various technological applications. This study investigates the evaporation behaviour of a colloidal binary droplet system comprising of the ethanol-water mixture and polystyrene nanoparticles. The wetting and evaporation dynamics were studied with an emphasis on the collective influence of ethanol and nanoparticle concentrations. The temporal behaviour of the contact angles, shapes and volumes of the droplets was monitored in order to analyse the evaporative behaviour. With increase of ethanol concentrations, the binary droplet volumes were found to decrease nonlinearly with time. Ethanol being more volatile evaporated in the initial stage. Towards the end of the evaporation process, the evaporation characteristics mimics the behaviour of pure water. Our study shows that the initial contact angle decreases monotonically with increased concentration of ethanol in the mixture. The contact angle is maximum for a particular nanoparticle concentration. Droplets with higher ethanol concentration show higher wettability which in its turn is maximum for low nanoparticle concentrations. This trend shows the interconnected effect of ethanol and nanoparticle concentrations on evaporation. Rim width of the final deposition pattern increases with nanoparticle concentration although it is almost independent of ethanol concentration. Finally, it is noticed that fast evaporation of a relatively more volatile component in a binary mixture droplet leads to nanoparticle segregation for low nanoparticle concentrations. Thus for binary mixtures, the evaporation of the more volatile component, ethanol for our case, offers characteristic differences in the resulting evaporation dynamics from that of pure water which finds applicability for multi-component evaporation processes.

Sites of highest predictability for neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy.

Identifying earlier retinal thickness affection and predictability for diabetic retinal neurodegeneration (DRN) in patients with type 2 diabetes mellitus (DM2) without diabetic retinopathy (DR). This is a comparative cross-sectional study. Thirty-eight eyes of 19 patients with DM2 without any signs of DR and 38 eyes of 19 controls underwent retinal evaluation using optical coherence tomography. Macular ganglion cell layer (GCL), macular retinal nerve fiber layer (mRNFL), inner plexiform layer (IPL), total macular thickness, peripapillary retinal nerve fiber layer (pRNFL) and Bruch's membrane opening-minimum rim width (BMO-MRW) were evaluated. GCL showed significant thickness reduction in the total, superior and inferior halves as well as the 9 ETDRS regions (except the nasal and lower outer regions). The mRNFL showed a significant reduction in the total, superior and inferior halves as well as the lower and nasal outer regions. The IPL showed significant reduction in the 4 inner regions only. The pRNFL showed significant reduction in the total, superotemporal and inferotemporal sectors values. The BMO-MRW did not show any significant thickness change. The total, superior and inferior GCL and mRNFL, in addition to the global pRNFL were the most affected and predictive layers for DRN in patients with DM type 2 without DR. It appears that the GCL is the primary site of DRN and the rest of the changes represented a degeneration of the axonal path between the optic disk and the macular GCL.

Bruch's membrane opening-minimum rim width: An alternative OCT biomarker study for multiple sclerosis.

Bruch's membrane opening-minimum rim width (BMO-MRW) and RNFL measured using anatomic positioning system (APS-RNFL) are novel OCT methods and remained unexplored in MS patients.To investigate the novel parameters of spectral-domain OCT as an alternative biomarker in patients with multiple sclerosis (MS). Retrospective cohort study; participants consisted of relapsing-remitting MS (RRMS) patients and healthy controls (HC). Eyes were classified according to the presence of MS and previous optic neuritis (ON). Measurements of standard peripapillary RNFL (S-RNFL), BMO-MRW, and APS-RNFL were performed. A total of 244 eyes of 122 participants (MS-patients: 63, HC: 59) were included in the study. Fifty-one eyes had a history of previous ON. In almost all measured parameters, neuroretinal rim thicknesses were observed the thinnest in eyes with ON history between all subgroups. S-RNFL and APS-RNFL techniques showed the difference in neuroretinal rim thickness in all three subjects (ON+, ON-, and HC). However, BMO-MRW, on the other hand, could not distinguish between ON(-) patients and HC. The relationship between OCT parameters and EDSS were observed only in eyes with an ON history in all three techniques. A meaningful model with 78% accuracy was obtained by using only the OCT parameters as risk factors. In the ROC analysis, no parameters were found to have acceptable high sensitivity and specificity. BMO-MRW was statistically weaker in every aspect than other RNFL techniques. The novel APS-RNFL technique appears to be a bit more reliable alternative to S-RNFL technique to support therapeutic decision-making in MS. BMO-MRW has not been found as a successful alternative to S-RNFL.

Comparison of Retinal Nerve Fibre Layer versus Bruch Membrane Opening-Minimum Rim Width as an Optical Coherence Tomography-based Marker for Glaucoma in Myopia.

To compare the reliability of Bruch Membrane Opening-Minimum Rim Width (BMO-MRW) Optical Coherence Tomography (OCT) with Retinal Nerve Fibre Layer (RNFL) in myopic patients. Cross-sectional study. LRBT Free Base Eye Hospital, Karachi, from May 2019 to July 2020. Moderate myopes with refractive errors between -3 to -6 diopters were examined by 2 glaucoma consultants separately, who performed fundoscopy to evaluate the optic nerve head, checked IOP and assessed CCT and visual fields to stratify the eyes into myopic normal and myopic glaucomatous eyes. All eyes were imaged with SD OCT of Spectralis version 1.10.2.0 of Heidelberg Engineering. Two scanning patterns, one for BMO-MRW and the other for RNFL thickness analysis, were performed. Fifty eyes of 50 patients were diagnosed with glaucoma in 50% (25 out of 50 patients). OCT RNFL detected glaucoma in 72% (36 out of 50 patients). While OCT BMO-MRW detected glaucoma in 56% (28 out of 50 patients). There was strong agreement between the consultant's judgements and BMO-based test (κ = 0.800, p <0.001), but the association was comparatively weaker with RNFL-based prediction (κ = 0.480, p <0.001). Specificity was better with OCT BMO-MRW (85.7%) than RNFL (66.7%). There were lower false positive rates with BMO-MRW (14.3%) than RNFL (33.3%). OCT BMO-MRW is a better indicator of glaucomatous damage in moderately myopic eyes as compared to OCT RNFL analysis. Key Words: Glaucoma, Myopia, Optical Coherence Tomography (OCT), Bruch Membrane Opening-Minimum Rim Width (BMO-MRW), Retinal Nerve Fibre Layer (RNFL).

Retinal Vascular Endothelial Cell Dysfunction and Neuroretinal Degeneration in Diabetic Patients.

Diabetes mellitus (DM) has become a vital societal problem as epidemiological studies demonstrate the increasing incidence of type 1 and type 2 diabetes. Lesions observed in the retina in the course of diabetes, referred to as diabetic retinopathy (DR), are caused by vascular abnormalities and are ischemic in nature. Vascular lesions in diabetes pertain to small vessels (microangiopathy) and involve precapillary arterioles, capillaries and small veins. Pericyte loss, thickening of the basement membrane, and damage and proliferation of endothelial cells are observed. Endothelial cells (monolayer squamous epithelium) form the smooth internal vascular lining indispensable for normal blood flow. Breaking its continuity initiates blood coagulation at that site. The endothelium controls the process of exchange of chemical substances (nutritional, regulatory, waste products) between blood and the retina, and blood cell passing through the vascular wall. Endothelial cells produce biologically active substances involved in blood coagulation, regulating vascular wall tension and stimulating neoangiogenesis. On the other hand, recent studies have demonstrated that diabetic retinopathy may be not only a microvascular disease, but is a result of neuroretinal degeneration. Neuroretinal degeneration appears structurally, as neural apoptosis of amacrine and Muller cells, reactive gliosis, ganglion cell layer/inner plexiform (GCL) thickness, retinal thickness, and retinal nerve fiber layer thickness, and a reduction of the neuroretinal rim in minimum rim width (MRW) and functionally as an abnormal electroretinogram (ERG), dark adaptation, contrast sensitivity, color vision, and microperimetric test. The findings in early stages of diabetic retinopathy may precede microvascular changes of this disease. Furthermore, the article’s objective is to characterize the factors and mechanisms conducive to microvascular changes and neuroretinal apoptosis in diabetic retinopathy. Only when all the measures preventing vascular dysfunction are determined will the risk of complications in the course of diabetes be minimized.

Optic disc morphology in primary open-angle glaucoma versus primary angle-closure glaucoma in South India.

Purpose:The aim of this study was to investigate the optic disc morphology in primary angle-closure glaucoma (PACG) versus primary open-angle glaucoma (POAG) in South Indians.Methods:A total of 60 patients (60 eyes) with PACG and 52 patients (52 eyes) with POAG were included in a cross-sectional observational study. The glaucoma diagnosis was based on a glaucomatous appearance of the optic disc correlating with visual field defects. The glaucoma was graded as early, moderate, or severe, depending upon perimetric loss. All patients underwent an ophthalmic evaluation, including visual field examination and planimetric analysis of 30° stereoscopic color optic disc photographs.Results:The POAG and PACG groups did not differ significantly in a disc or rim area, rim width, and frequencies of disc hemorrhages or rim notches. However, early POAG group (n = 15) had a significantly deeper cup depth (P = 0.01), larger beta zone (P = 0.01), and a higher frequency of localized retinal nerve fiber layer (RNFL) defects (P = 0.02) than early PACG (n = 20).Conclusion:In the early stage of the disease, POAG compared to PACG may be characterized by deeper disc cupping, a larger beta zone of peripapillary atrophy, and a higher frequency of localized RNFL defects. Such differences in early glaucoma may suggest differences in pathophysiology in POAG and PACG.

Modeling and performance evaluation of a small solar parabolic trough collector (PTC) for possible purification of drained water

Small-scale solar thermal contaminated water purification is a promising green energy based decentralized process especially for rural area. The present work describes thermal performance estimation of a Parabolic Trough Collector (PTC) suitable for contaminated water purification. Contaminated drain water is pressurized through a slow sand filter and PTC with glass cover enclosing a copper tube. The diameter of the copper tube was estimated as 26 mm and that of the glass cover was 50 mm. The rim angle and width of the parabola were 60° and 1.2 m respectively. The PTC focal length, concentration ratio, overall heat loss coefficient was 493.4 mm, 13.93 and 7.39 W/m2K respectively. The maximum modeled and experimental thermal efficiency were about 60% and 55% respectively. Around water flow rate of 0.002 kg/s and solar radiation 750 W/m2, both water temperature and useful heat gain were maximum. The exergetic efficiency of the system increases with the increase of inlet temperature of water for different solar intensity. The solar purified water had all other parameters within acceptable limit except residual chlorine (0.24 mg/L).

Relationship between crack length, wedge-shaped cutter geometry, and salt rocks viscosity in a cross-cutting scheme

Introduction. Existing publications lack studies on the relationship between salt rocks physical properties, cutters geometry, cutting force, and intergranular fracture of rock under the cutter. By analyzing the system of cracks formed by the cutters between the cutting lines, it is possible to estimate the effi ciency of fracture and design the nature and conditions of cutting. Research aim is to obtain an analytical dependence that links cracks size, cutter geometry, and salt rocks crack resistance; calculate the cutting force; experimentally determine sylvine, halite and carnallite fracture toughness coeffi cients necessary for the calculation. And fi nally, based on the obtained data, the research aimed to build 3D graphs of crack length dependence on cutter geometry for a cross-cutting scheme. Methodology. Sylvine, halite and carnallite crack resistance coeffi cients were obtained by indentation. The coeffi cient values were used in the formula for calculating the size of cracks between the cutting lines in these rocks. The formula was corrected after D6.22 cutter indentation test in salt rocks. Light microscopy technique was used to study fl uid inclusions in salt rocks. Results. Analytical dependence, values of crack resistance coeffi cients were obtained. 3D graphs for halite, sylvine and carnallite were constructed for the cross-cutting scheme. The type, size and concentration of fl uid inclusions along the grain boundaries are given that accelerate intergranular fracture under the cutter. Conclusions. The resulting formula relates cutter geometry (cutting rim width and cutting angle) to the cutting force and viscosity of rocks. The formula was used to build the 3D graphs for sylvine, halite and carnallite for the cross-cutting scheme. The size of cracks under the cutter is connected with the presence of fl uid inclusions. The obtained analytical dependence allows to model the spatial distribution and size of microfractures in salt rocks under the action of the cutting tool. Excessive branching of cracks, energy intensity, and the number of small fractions decrease, when the trajectory of the cutter partially passes through the “technogenic” cracks of the previous bed. This is implemented in the cross-cutting scheme, where this group of cracks plays the role of “starting” ones. Their length in actual practice is important for justifying the optimal cutting parameters and estimating the cutter’s effi ciency.

Recent developments in the use of optical coherence tomography for glaucoma.

The aim of this article is to summarize findings of recent reports highlighting the utility of novel optical coherence tomography (OCT) parameters in the diagnosis and monitoring of glaucomatous optic neuropathy. Optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular parameters show high levels of diagnostic capability. The Bruch's membrane opening-minimum rim width (BMO-MRW) measurement is a novel ONH parameter obtained using the Spectralis SD-OCT device (Heidelberg Engineering, Inc., Heidelberg, Germany). The inferotemporal BMO-MRW sector shows the highest diagnostic performance for this parameter. Minimum ganglion cell and inner plexiform layer thickness shows the highest diagnostic performance among macular parameters obtained with the Cirrus HD-OCT (Carl Zeiss, Inc., Dublin, CA, USA). Optic nerve head, macular, and retinal nerve fiber layer parameters are not interchangeable across protocols generated by varying OCT manufacturers. Novel machine-learning algorithms show promise with regards to achieving higher levels of diagnostic accuracy using OCT imaging platforms. Digital imaging in glaucoma continues to evolve with novel parameters of the optic nerve head, retinal nerve fiber layer, and macula. Diagnostic abilities of these parameters are high and complementary to each other.

Optic Nerve Head Morphological Changes Over 12 Hours in Seated and Head-Down Tilt Postures.

PurposeThe purpose of this study was to determine changes in optic nerve head (ONH) morphology in seated and 6° head-down tilt (HDT) postures over a 12-hour period.MethodsThirty eyes of 30 healthy human subjects (15 females) were included. Composite radial and circular optical coherence tomography (OCT) scans centered on the ONH, intraocular pressure (IOP), and optic nerve sheath diameter (ONSD) were acquired every two hours from 7 a.m. to 7 p.m. for both seated (n = 30) and HDT (n = 10) sessions. Global minimum rim width (BMO-MRW), total retinal thickness (TRT), retinal nerve fiber layer thickness (RNFLT), and Bruch's membrane opening (BMO) height were quantified.ResultsBMO-MRW decreased an average of 9.55 ± 8.03 µm (P < 0.01) over 12 hours in a seated position (range, −26.64 to +3.36 µm), and thinning was greater in females (−13.56 vs. −5.55 µm, P = 0.004). Modest decreases in TRT from the BMO to 500 µm (P < 0.04) and RNFLT for the 2.7, 3.5, and 4.2 mm circular scans (P < 0.02) were also observed. BMO-MRW thinning was not related to changes in IOP or ONSD (P = 0.34). In HDT, IOP and ONSD increased, BMO height moved anteriorly, and BMO-MRW thinning did not occur (P > 0.1).ConclusionsThe neuroretinal rim thins throughout the day in healthy individuals, and this change cannot be explained by changes in IOP or ONSD during the same time period. A HDT posture blunts the neuroretinal rim thinning observed in a seated position, suggesting a role of the translaminar pressure difference.