Optic Layer Research Articles

Vitrectomy in Small idiopathic MAcuLar hoLe (SMALL) study: Internal limiting membrane peeling versus no peeling.

To compare vitrectomy with and without internal limiting membrane (ILM) peeling in small idiopathic macular holes. Retrospective multicentre study including consecutive eyes with ≤250 μm idiopathic macular hole treated with vitrectomy. The primary outcome was hole closure rate. Best-corrected visual acuity (BCVA) change, closure patterns on optical coherence tomography, rates of external limiting membrane (ELM) and ellipsoid zone (EZ) recovery, and rate of complications were also investigated. In total, 693 eyes were included. Hole closure rate was 98% in the peeling and 85% in the no-peeling group (p < 0.001). At 12 months, mean BCVA change was 0.38 ± 0.22 logMAR in the peeling and 0.45 ± 0.21 logMAR in the no-peeling group (p = 0.02); 66% versus 80% of eyes had a U-shaped morphology, respectively; EZ recovery rate was 75% and 93%, respectively (p = 0.02). In the no-peeling group, eyes with a vitreomacular traction (VMT) showed a 96% closure rate, comparable to the peeling group (p = 0.40). The incidence of adverse events was similar except for dissociated optic nerve fibre layer (55% in the peeling vs. 9% in the no-peeling group, p < 0.001). In small idiopathic macular holes, ILM peeling provides a higher closure rate compared to no-peeling; however, if a VMT is present closure rates are comparable. In closed macular holes, the no-peeling technique provides advantages in terms of visual outcome and anatomical recovery.

Functional segregation and dynamic integration of the corticotectal descending signal in rat

The superior colliculus (SC) receives inputs from various brain regions in a layer- and radial subregion-specific manner, but whether the SC exhibits subregion-specific dynamics remains unclear. To address this issue, we recorded the spiking activity of single SC neurons while photoactivating cortical areas in awake head-fixed Thy1-ChR2 rats. We classified 309 neurons that responded significantly into 8 clusters according to the response dynamics. Among them, neurons with monophasic excitatory responses (7–12 ms latency) that returned to baseline within 20 ms were commonly observed in the optic and intermediate gray layers of centromedial and centrolateral SC. In contrast, neurons with complex polyphasic responses were commonly observed in the deep layers of the anterolateral SC. Cross-correlation analysis suggested that the complex pattern could be only partly explained by an internal circuit of the deep gray layer. Our results indicate that medial to centrolateral SC neurons simply relay cortical activity, whereas neurons in the deep layers of the anterolateral SC dynamically integrate inputs from the cortex, SNr, CN, and local circuits. These findings suggest a spatial gradient in SC integration, with a division of labor between simple relay circuits and those integrating complex dynamics.

Internal Limiting Membrane Peeling for Large Macular Holes Induces Only Structural Remodeling without Functional Impairment Over 12 Years

To evaluate the very long-term functional and structural outcomes of internal limiting membrane (ILM) peeling for full-thickness macular holes (FTMH). Observational case series nested within a multicenter, randomized, controlled clinical trial (RCT) (ClinicalTrials.gov: NCT00190190). Patients who underwent vitrectomy with or without ILM peeling for an idiopathic large FTMH in a tertiary ophthalmology center, with a minimum follow-up of 10 years after surgery. Review of charts, spectral-domain OCT (SD-OCT) scans, OCT angiography (OCTA) scans, and microperimetry of patients originally enrolled in the RCT. Primary outcome was functional assessment in both groups (ILM peeling or not) including the retinal sensitivity (RS), distance and near best-corrected visual acuity (BCVA), and number of eyes achieving ≥0.3 logarithm of the minimum angle of resolution >10 years after surgery. Secondary outcomes were structural assessment in the entire 3× 3-mm and 6× 6-mm areas, and regionally in the different areas of the ETDRS grid: OCT and OCTA biomarkers in both groups and fellow eyes. Thirteen eyes of 13 patients with a mean follow-up of 12 ± 0.73 years were included. The mean RS and BCVA, or visual improvement did not differ between ILM peeling (n= 8) and no peeling (n= 5) (all P > 0.05). The dissociated optic nerve fiber layers on en face OCT were only observed in eyes with ILM peeling, predominantly in temporal parafoveal (20%) and perifoveal (19%) rings. The mean total retinal thickness and inner retinal thickness in the parafoveal ring were significantly lower in peeled eyes (309 ± 11 μm and 94 ± 9 μm respectively) versus nonpeeled eyes (330 ± 21 μm and 108 ± 11 μm respectively; P= 0.037 and P= 0.040), without significant difference in ganglion cell or retinal nerve fiber layers. Accordingly, the mean superficial capillary plexus density in the parafoveal ring was significantly lower in eyes with peeling versus without (39.65 ± 3.76 % versus 47.22 ± 4.00; P= 0.005). The mean foveal avascular zone area was smaller in eyes with peeling versus without (0.24 ± 0.05 mm2 vs. 0.42 ± 0.13 mm2, respectively, P= 0.005). Despite persistent structural changes especially in the parafoveal ring, ILM peeling for idiopathic large FTMH did not seem to impact long-term RS or BCVA over 12 years. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Retinal displacement after surgery for idiopathic macular hole.

To review and summarize the mechanism hypothesis, influencing factors and possible consequences of macular retinal displacement after idiopathic macular hole (IMH) surgery. PubMed and Web of Science database was searched for studies published before April 2023 on "Retinal displacement", "Idiopathic macular holes", and "Macular displacement". Recently, more academics have begun to focus on retinal displacement following idiopathic macular holes. They found that internal limiting membrane (ILM) peeling was the main cause of inducing postoperative position shift in the macular region. Moreover, several studies have revealed that the macular hole itself, as well as ILM peeling method, will have an impact on the result. In addition, this phenomenon is related to postoperative changes in macular retinal thickness, cone outer segment tips line recovery, the occurrence of dissociated optic nerve fiber layer (DONFL) and the degree of metamorphopsia. As a subclinical phenomenon, the clinical significance of postoperative macular displacement cannot be underestimated as it may affect the recovery of anatomy and function.

Observation on the changes of visual field and optic nerve fiber layer thickness in patients with early diabetic retinopathy

BackgroundDiabetic retinopathy (DR) is a common complication of diabetes mellitus (DM) and is a leading cause of vision loss. Early detection of DR-related neurodegenerative changes is crucial for effective management and prevention of vision loss in diabetic patients. MethodsIn this study, we employed spectral-domain polarization-sensitive optical coherence tomography (SD PS-OCT) to assess retinal nerve fiber layer (RNFL) changes in 120 eyes from 60 types 1 DM patients without clinical DR and 60 age-matched healthy controls. Visual field testing was performed to evaluate mean sensitivity (MS) and mean defect (MD) as indicators of visual function. ResultsSD PS-OCT measurements revealed significant reductions in RNFL birefringence, retardation, and thickness in type 1 DM patients compared to healthy controls. Visual field testing showed decreased MS and increased MD in DM patients, indicating functional impairment correlated with RNFL alterations. ConclusionOur findings demonstrate early neurodegenerative changes in the RNFL of type 1 DM patients without clinical DR, highlighting the potential of SD PS-OCT as a sensitive tool for early detection of subclinical DR-related neurodegeneration. These results underscore the importance of regular ophthalmic screenings in diabetic patients to enable timely intervention and prevent vision-threatening complications.

EXPRESSION OF NEUROFILAMENTS IN THE RETINA IN EXPERIMENTAL DIABETIC RETINOPATHY AND THE INFLUENCE OF THE BENZODIAZEPINE RECEPTOR AGONIST CARBACETAM

Background. One of the typical neurochemical pathogenetic mechanisms causing the dysfunction of retinal neurons in diabetic retinopathy (DR) is a deficiency of GABA-ergic mediation. To some extent, this justifies the prospect of using GABA receptor modulators, including benzodiazepines.&#x0D; Aim: To determine the expression of neurofilaments in the initial stages of the experimental DR development and the influence of the benzodiazepine receptor agonist Carbacetam.&#x0D; Materials and methods. DR was modeled in 35 three-month-old male Wistar rats by a single injection of streptozotocin (50 mg/kg; Sigma-Aldrich, Co, China). The rats were divided into 3 groups: control, with the introduction of Insulin (30 Units; Novo Nordisk A/S, Bagsvaerd, Denmark) and with the introduction of Insulin and Carbacetam (5 mg/kg). NF-H neurofilaments (ThermoFisher Scietific, USA) were detected in the retina by immunohistochemistry.&#x0D; Results. Before DR modeling, NF-H-positive staining was detected in the inner and outer layers of the retina in mainly longitudinal fibers of different lengths, which corresponded to the axons of horizontal and amacrine cells; as well as in fibers and axonal hills of ganglion neurons. In the dynamics of the DR development in the plexiform layers of the retina, a progressive decrease in the intensity of staining was observed. In the optic fiber layer, staining was concentrated around dilated microvessels that tended to form microaneurysms. On the 28th day, NF-H-positive staining disappeared in the inner plexiform layer. Administration of Insulin with Carbacetam prevented the loss of NF-H-positive staining in the layers of the retina.&#x0D; Conclusion. The use of the benzodiazepine receptor agonist Carbacetam may be a promising direction for the correction of retinal neurodegeneration in DR.

Steroid Induced Glaucoma and Primary Angle Closure Glaucoma: A Case Report of Mixed Mechanism Glaucoma

Introduction : Steroid induced glaucoma is a form of secondary open angle glaucoma (OAG) caused by adverse effects of steroid usage. Primary angle closure glaucoma (PACG) is characterized by shallow anterior chamber accompanied by peripheral anterior synechiae (PAS), elevated IOP and glaucomatous optic neuropathy (GON).&#x0D; Case Illustration : A 58 year-old woman presented with red eye, blurry vision, pain in her right eye radiating to the head, watery eye and halo. History of experiencing recurrent red eye, improving after taking steroid topical drug for about 3 months. Visual acuity 6/20 ph 6/20, IOP 39 mmHg, mixed conjunctival injection, shallow anterior chamber Van Herick 1-2, dilated pupil and iris pigment on anterior capsule of lens. Posterior segment showed glaucomatous optic neuropathy with cup disc ratio 0.8-0.9, anterior chamber depth 2.58, and thinning of optic nerve head layer. Patient was diagnosed with steroid induced glaucoma and mixed mechanism PACG. The patient underwent trabeculectomy procedure after mannitol injection was given to reduce IOP.&#x0D; Discussion : We diagnosed the patient with steroid induced glaucoma and mixed mechanism PACG based on history, clinical findings, and diagnostics. Steroid raised IOP by accumulating polymerized glycosaminoglycans (GAGs) in the trabecular meshwork, producing "biologic edema" thus increased outflow resistance. PACG was determined based on Van Herick and anterior chamber depth. Trabeculectomy remains an effective treatment in this case where medications were failed to control IOP.&#x0D; Conclusion : Steroid induced glaucoma commonly found in OAG, definitive treatment includes halting steroid drugs and trabeculectomy. Further follow-up is needed to evaluate angle closure mechanism.

Study of the ganglion cell complex of the macula by optical coherence tomography in the diagnosis of glaucoma progression

IntroductionThe aim of this work is to evaluate the usefulness of the study of the ganglion cell complex of the macula using the OCT technique to estimate the progression of glaucoma according to its severity. Material and methodsThis is a retrospective cross-sectional study. It includes 205 eyes of 131 patients with glaucoma or ocular hypertension followed for a mean of 5.7 years. The parameters and rates of three tests have been analyzed using the progression software of each instrument: visual field, optical coherence tomography (OCT) in the ganglion cell complex of the macula and in the nerve fiber layer of the optic nerve. The results of each test, the concordance between them and how they differ according to severity stage have been evaluated. ResultsVisual field classifies more cases of progression in moderate-advanced glaucoma, while in mild glaucoma its capacity is limited. Optic nerve fiber layer OCT classifies more cases of progression in mild glaucoma than in moderate-advanced glaucoma, as it is artifacted by the floor effect. OCT of the macular ganglion cell complex is the test that classifies more cases of progression and has the highest agreement with visual field, regardless of severity. ConclusionIn both mild and moderate-advanced glaucoma, OCT of the macula ganglion cell complex may be a better biomarker of progression than OCT of the macula ganglion cell complex.

Utilidad del estudio del complejo de células ganglionares de la mácula mediante tomografía de coherencia óptica en el diagnóstico de progresión del glaucoma

IntroductionThe aim of this work is to evaluate the usefulness of the study of the ganglion cell complex of the macula using optical coherence tomography (OCT) to estimate the progression of glaucoma according to its severity. Material and methodsThis is a retrospective cross-sectional study. It includes 205 eyes of 131 patients with glaucoma or ocular hypertension followed for a mean of 5.7years. The parameters and rates of three tests have been analyzed using the progression software of each instrument: visual field, OCT in the ganglion cell complex of the macula and in the nerve fiber layer of the optic nerve. The results of each test, the concordance between them and how they differ according to severity stage have been evaluated. ResultsVisual field classifies more cases of progression in moderate-advanced glaucoma, while in mild glaucoma its capacity is limited. Optic nerve fiber layer OCT classifies more cases of progression in mild glaucoma than in moderate-advanced glaucoma, as it is artifacted by the floor effect. OCT of the macular ganglion cell complex is the test that classifies more cases of progression and has the highest agreement with visual field, regardless of severity. ConclusionThe study of the macula ganglion cell complex using OCT could be a better biomarker of progression than the study of the optic nerve fiber layer, at any stage of glaucoma.

Central macular morphology and optic nerve fibre layer thickness in young adults born premature and screened for retinopathy of prematurity.

To investigate central retinal morphology and optic retinal nerve fibre layer (RNFL) in prematurely born young adults and compare to term born controls. The participants were 59 prematurely born individuals, with a birthweight ≤1.500 g, and 44 term born controls, all 25-29 years of age. Visual acuity (VA) and contrast sensitivity (CS) were assessed. The retinal macular thickness, ganglion cell-inner plexiform layer (GC-IPL) thickness and RNFL thickness were assessed with Cirrus optical coherence tomography (OCT). Central macular thickness was increased (mean 26.7 μm) in prematurely born individuals compared to controls. The macular GC-IPL was thinner (mean 3.84 μm), also when excluding those with previous retinopathy of prematurity (ROP) and those with neurological complications. Gestational age at birth and previous treatment of ROP were risk factors for a thicker macula, however, not for reduced GC-IPL. The average peripapillary RNFL was thinner (mean 4.61 μm) in the prematurely born individuals, also when excluding those with previous ROP and/or neurological complications. Within the prematurely born group, treated ROP was correlated with increased average RNFL. Further, both better VA and CS were associated with thinner optic nerve RNFL and thicker average GC-IPL. Macular and optic nerve morphology were influenced by premature birth as assessed with OCT in adult individuals. Gestational age at birth and treatment for ROP seemed to affect central macular thickness, and treated ROP affected the peripapillary RNFL. Thus, retinal sequelae remained in adulthood.

Evaluation of cellular activity in response to sleep deprivation by a comprehensive analysis of the whole mouse brain.

Sleep deprivation (SD) causes several adverse functional outcomes, and understanding the associated processes can improve quality of life. Although the effects of SD on neuronal activity in several brain regions have been identified, a comprehensive evaluation of the whole brain is still lacking. Hence, we performed SD using two different methods, gentle handling and a dedicated chamber, in targeted recombination in active populations 2 (TRAP2) mice crossed with Rosa-ZsGreen reporter mice and visualized cellular activity in the whole brain. Using the semi-automated post-imaging analysis tool Slice Histology Alignment, Registration, and Cell Quantification (SHARCQ), the number of activated cells was quantified. From the analysis of 14 brain regions, cellular activity was significantly increased in the olfactory areas and decreased in the medulla by the two SD methods. From the analysis of the further subdivided 348 regions, cellular activity was significantly increased in the vascular organ of the lamina terminalis, lateral hypothalamic area, parabigeminal nucleus, ventral tegmental area, and magnocellular reticular nucleus, and decreased in the anterior part of the basolateral amygdalar nucleus, nucleus accumbens, septohippocampal nucleus, reticular nucleus of the thalamus, preoptic part of the periventricular hypothalamic nucleus, ventromedial preoptic nucleus, rostral linear nucleus raphe, facial motor nucleus, vestibular nuclei, and some fiber tracts (oculomotor nerve, genu of corpus callosum, and rubrospinal tract) by the two SD methods. Two subdivided regions of the striatum (caudoputamen and other striatum), epithalamus, vascular organ of the lamina terminalis, anteroventral preoptic nucleus, superior colliculus optic layer, medial terminal nucleus of the accessory optic tract, pontine gray, and fiber tracts (medial lemniscus, columns of the fornix, brachium of the inferior colliculus, and mammillary peduncle) were differentially affected by the two SD methods. Most brain regions detected from these analyses have been reported to be involved in regulating sleep/wake regulatory circuits. Moreover, the results from the connectivity analysis indicated that the connectivity of cellular activity among brain regions was altered by SD. Together, such a comprehensive analysis of the whole brain is useful for understanding the mechanisms by which SD and/or sleep disruption affects brain function.

Rho-Kinase Inhibitors as Emerging Targets for Glaucoma Therapy.

Glaucoma, the leading cause of irreversible blindness worldwide, is a chronic and progressive optic neuropathy characterized by damage to the optic and retinal nerve fiber layers, which can lead to permanent loss of peripheral or central vision. Reduction of intraocular pressure (IOP) is the only known modifiable risk factor for preventing and treating glaucoma. Rho kinase (ROCK) inhibitors are a new class of glaucoma drugs with a novel mechanism of action and good safety profile. They exert neuroprotective effects, act on the trabecular tissue, increase the outflow of aqueous humor, and reduce intraocular pressure. However, they also cause local adverse reactions, including common conjunctival congestion and subconjunctival bleeding; however, most are self-limiting and temporary. Netarsudil (0.02%), a ROCK inhibitor, relaxes the trabecular meshwork, increases the outflow of aqueous humor, reduces scleral venous pressure, anddirectly decreases IOP. Conjunctival congestion can be reduced if netarsudil is administered at night. The combination of these medications is always more effective than the single drug. Ripasudil (0.4%), another ROCK inhibitor, also lowers IOP; however, conjunctival hyperemia is the most common adverse drug reaction. The purpose of this review is to summarize the effects and adverse reactions of ROCK inhibitors in the experimental trial stage and in clinical treatment in recent years, providing suggestions for future clinical drug use, and research and development to reduce the side effects of these drugs, maximize the potential for reducing IOP, and improve the therapeutic effect.

Perifoveal Microvascular Changes following Internal Limiting Membrane Peeling Surgery for Epiretinal Membrane and Macular Hole

Introduction: The aim of the study was to evaluate perifoveal microvasculature changes following pars plana vitrectomy with internal limiting membrane peeling for the epiretinal membrane (ERM) and macular hole (MH). Methods: This retrospective study included 59 eyes from 59 patients. Subjects were divided into two groups: an ERM group (n = 43) and an MH group (n = 16) based on the initial diagnosis. Swept-source optical coherence tomography angiography (SS-OCTA) was performed in the macular area, pre- and postoperatively. Perifoveal microvascular changes were calculated using MATLAB from the 6 × 6 mm SS-OCTA images, excluding the foveal avascular zone. Pre- and postoperative perifoveal vessel densities (pfVDs) were separately analyzed in six sectors (superior, superotemporal, inferotemporal, inferior, inferonasal, and superonasal) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP). The baseline characteristics and other clinical factors were compared between the ERM and MH groups. Results: The postoperative best-corrected visual acuity significantly improved in both groups (p < 0.05). One year after surgery, the pfVD in the SCP of the ERM group significantly decreased in the inferotemporal sector (p = 0.049). The postoperative pfVD in the DCP of the MH group significantly decreased in temporal sectors (p < 0.05). The postoperative mean pfVD in the SCP in the MH group was significantly lower than that in the ERM group (p = 0.003). The presence of a dissociated optic nerve fiber layer (DONFL) was 75% in the MH group and 22% in the ERM group (p = 0.018). The correlation between the pfVD and DONFL was not statistically significant. Conclusion: Postoperative pfVD reduction in the temporal sector, a corresponding area in which DONFL is present after MH surgery, was significantly observed. After vitreoretinal surgery in MH patients, OCTA may serve as a useful tool for monitoring perifoveal microvascular changes, especially in temporal sectors.

Surgical Treatment of Epiretinal Membranes: a Comparative Analysis of Various Removal Techniques.

In most cases, vitreoretinal surgery is the only way to treat epiretinal membrane (ERM). For a long time, surgeons only removed epiretinal fibrosis. But relapse of ERM took place in 10% of cases. Internal limiting membrane (ILM) peeling reduced the number of relapses, but this membrane is connected closely with terminal legs of Müller cells and its removal leads to mechanical and functional damage of the latter. In addition, frequent cases of "dissociation of the optic nerve fiber layer" were noticed in the long term after ILM removal, which caused a deterioration in the functional state of the retina. Purpose. The purpose of study was to conduct a comparative analysis of various methods of surgical treatment of epiretinal membrane. Materials and methods. On the base of the National Medical Center of Ophthalmology 75 patients with epiretinal membrane were treated with vitreoretinal surgery. All patients were divided into 3 groups. Patients of the first group were operated according to the standard procedure with the removal both ERM and ILM. The second group included patients after ERM removal without ILM peeling. The third group of patients were operated according to the original method – after ERM removal specific "debilitating notches" were performed on ILM. A complete ophthalmological examination was conducted for all patients in the pre- and postoperative period (1,3,6,12 months after surgical treatment). There were no significant differences between groups in age, gender, preoperative BCVA, preoperative intraocular pressure, preoperative CMT on optical coherence tomography, and cataract status. Results. Analysis of the results in the postoperative period revealed a significant improvement in BCVA at 6 months after surgery in the 2nd and 3rd groups of patients in comparison to the 1st group of patients. Assessment of morphological parameters of the retina in the postoperative period showed a significant improvement of condition in epiretinal fibrosis in groups 2 and 3 at 6 and 12 months after surgery. The reduce of foveolar thickness was more noticeable in groups 2 and 3 during all the period. In the postoperative period, a statistically significant improvement in central light sensitivity was revealed in patients of the 2nd and 3rd groups in comparison to similar parameters of patients of the 1st group at 3 months after surgical treatment. The same trend took place at 6 and 12 months after surgery. Conclusion. Our results showed that surgical treatment of ERM without ILM peeling yielded a better functional result compared to a group where peeling was performed within up to 12 months of follow-up. In order to reduce the risks of ERM relapse, we have developed an innovative technique of "debilitating notches", which allows us to achieve higher functional results than traditional ILM peeling and reduces the risks of relapse.

Influencia de la longitud axial ocular en el grosor de la capa de fibras nerviosas peripapilar medido con tomografía de coherencia óptica

BackgroundOptical coherence tomography (OCT) allows the measurement of the peripapillary optic nerve fiber layer (RNFL) thickness. The effect of ocular axial length (AL) on RNFL thickness measurement may be relevant in the interpretation of OCT results in diagnosing optic nerve diseases. PurposesTo assess the influence of ocular AL on RNFL thickness and on optic disc topographic parameters (optic disc area, rim area and cup volume) measured by OCT, in healthy individuals. MethodA sample of 109 healthy eyes classified into three groups according to AL (A: AL <22mm; B: AL 22–24.5mm; C: AL >24.5mm) was studied. RNFL thickness and optic disc topographic parameters were measured using Swept-Source OCT Triton (Topcon Corporation, Tokyo, Japan) and were compared between groups using a variance analysis. Correlation between the AL and the study variables was performed using a Pearson's correlation coefficient test. ResultsThe RNFL thickness was lower in eyes with higher AL in the superior (r=−0.41; p<0.001), inferior (r=0.58; p<0.001) and nasal (r=−0.43; p<0.001) quadrants, in the mean value of the RNFL (r=−0.49; p<0.001), optic disc area (r=−0.40; p<0.001) and rim area (r=−0.25; p=0.01). ConclusionAL is negatively correlated with RNFL thickness and optic disc topographic parameters measured by Swept-Source OCT Triton (Topcon).

The Influence of Wire Diameter Uniformity on the Quality of Fiber Optic Wire Package

The fiber optic wire package is the core component of fiber optic guided rockets. Due to the non-uniformity of the fiber optic wire diameter, the winding process is prone to winding defects, which affects the missile launch process. In this paper, a finite element simulation model for the winding process of the fiber optic wire package is established. The accuracy of the simulation model is verified by comparing it with the analytical model for the contact pressure between fiber optic layers. Then finite element models considering the wire diameter tolerance are established to analyze the effect of diameter uniformity on the winding quality of the fiber package. The results show that the stress distribution of a fiber optic package becomes increasingly uneven with increasing wire diameter non-uniformity, and the structural stability of the package decreases. The edge fibers of a 20-layer optical fiber package are easily extruded when the deviation from the nominal diameter is more than 3%. This study helps to guide the manufacturing accuracy of optical fibers and improve the structural stability of the wire package.

Ocular axial length influence on peripapillary retinal nerve fiber layer thickness measurement with optical coherence tomography

BackgroundOptical coherence tomography (OCT) allows the measurement of the peripapillary optic nerve fiber layer (RNFL) thickness. The effect of ocular axial length (AL) on RNFL thickness measurement may be relevant in the interpretation of OCT results in diagnosing optic nerve diseases. PurposeTo assess the influence of ocular AL on RNFL thickness and on optic disc topographic parameters (optic disc area, rim area and cup volume) measured by OCT, in healthy individuals. MethodsA sample of 109 healthy eyes classified into 3 groups according to AL (A: AL<22mm; B: AL 22−24.5mm; C: AL>24.5mm) was studied. RNFL thickness and optic disc topographic parameters were measured using Swept-Source OCT Triton (Topcon) and were compared between groups using a variance analysis. Correlation between the AL and the study variables was performed using a Pearson's correlation coefficient test. ResultsThe RNFL thickness was lower in eyes with higher AL in the superior (r=−0.41; p<0.001), inferior (r=0.58; p<0.001) and nasal (r=−0.43; p<0.001) quadrants, in the mean value of the RNFL (r=−0.49; p<0.001), optic disc area (r=−0.40; p<0.001) and rim area (r=−0.25; p=0.01). ConclusionsAL is negatively correlated with RNFL thickness and optic disc topographic parameters measured by Swept-Source OCT Triton (Topcon).

THREE-DIMENSIONAL HEADS-UP VITRECTOMY VERSUS CONVENTIONAL MICROSCOPIC VITRECTOMY FOR PATIENTS WITH EPIRETINAL MEMBRANE.

To investigate the efficacy and safety of 3D heads-up display (3D-HUD) vitrectomy compared with conventional microscopy (CM) vitrectomy in epiretinal membrane (ERM) surgery. Epiretinal membrane removal with or without internal limiting membrane (ILM) peeling was performed using a 3D-HUD or CM system. The mean changes in best-corrected visual acuity (BCVA) and in central macular thickness (CMT) and postoperative complications were assessed. Baseline demographics were comparable except for the follow-up period. Both BCVA and CMT improved at the final visit (all P < 0.05). The ERM recurrence and dissociated optic nerve fiber layer (DONFL) rates were lower in the 3D group (both P < 0.05). conventional microscopic vitrectomy (odds ratio [OR] = 12.86, P = 0.02) and absence of ILM peeling (OR = 45.25, P < 0.05) were associated with ERM recurrence. In the DONFL, CM vitrectomy (OR = 1.98, <0.05) and combined phacovitrectomy (OR = 2.33, P = 0.03) were analyzed as risk factors for DONFL. The improvement in BCVA and CMT in ERM surgery using a 3D-HUD is comparable with that of CM vitrectomy, with a significantly low rate of ERM recurrence and DONFL occurrence. Therefore, 3D vitrectomy might have an advantage for ERM surgery.

Comparative neurotoxicity of dietary methylmercury and waterborne inorganic mercury in fish: Evidence of optic tectum vulnerability through morphometric and histopathological assessments

This work investigated the effects of inorganic mercury (iHg) and methylmercury (MeHg) on the fish optic tectum morphology, viz. in relation to: (i) vulnerability of specific optic tectum layers; (ii) preferential targeting of Hg forms to neurons or glial cells; (iii) comparative toxicity of iHg and MeHg in this brain area that is in the maintenance of several fish behaviors. Two experiments exposing juvenile white seabream (Diplodus sargus) to waterborne iHg [HgCl2 (2 μg L−1)] and dietary MeHg (8.7 μg g−1) were performed, comprising both exposure (7 and 14 days; E7 and E14, respectively) and post-exposure (28 days; PE28) periods. Morphometric assessments were performed using stereological methods where the layers of the optic tectum were outlined, while its area and the number of neurons and glial cells were estimated. A histopathological assessment was also performed per section and per layer of optic tectum. iHg exposure did not trigger the loss of neurons during the exposure periods, while a decrease of glial cells was detected in a single layer of the optic tectum at E14. Differently, upon MeHg exposure, a decrease on the number of neurons and glial cells was found in several layers of optic tectum. In the post-exposure, both Hg forms triggered the loss of neurons, while only MeHg exposure led to a decrease on the number of glia cells. The histopathological assessment pointed out a higher toxicity of MeHg in the optic tectum layers, particularly in the post-exposure period, while no significant alterations were found in fish exposed to iHg. Hg forms targeted preferentially neurons. iHg and MeHg are relevant neurotoxicants to fish, with MeHg exposure leading to a higher toxicity than iHg in the optic tectum. After 28 days of post-exposure, iHg and MeHg neurotoxicity remained prominent, suggesting long-term effects of these toxicants.

The impact of perinatal brain injury on retinal nerve fiber layer thickness and optic nerve head parameters of premature children

PurposeThis study aims to evaluate the impact of birth weight (BW), gestational age (GA), retinopathy of prematurity (ROP), and perinatal brain injury (PBI) on optic nerve head (ONH) parameters and nerve fiber layer thickness (RNFLT) in preterm children.MethodsONH parameters and RNFLT were examined prospectively in 5–15-year-old preterm and full-term children with RTVue-100 OCT (Optovue, USA). The parameters of the two groups were compared and possible influences of BW, GA, ROP, and PBI analyzed in preterm children.ResultsIn total, 51 full-term and 55 preterm children were included. The mean age was 9.98 ± 3.4 years in full-term and 10.0 ± 2.5 years in preterm children. The mean GA in preterm children was 29.6 ± 3.8 weeks with a BW of 1523 ± 732 g. RNFLT was significantly lower in preterm than in full-term children in all but temporal quadrants. Cup area, volume, cup/disc area ratio, and horizontal cup/disc ratio (CDR) were significantly larger and rim area significantly thinner in preterm children. GA was positively correlated with superior, nasal, and overall RNFLT and negatively correlated with cup area, volume, and horizontal CDR. ROP stage correlated negatively with superior and nasal RNFLT. PBI was the only significant predicting factor for RNFL thinning in all but temporal quadrant in multiple regression analysis. Preterm children with PBI had a significantly larger optic cup (CDR 0.70 ± 0.33 vs. 0.37 ± 0.27) and thinner optic rim.ConclusionPBI correlated strongest with RNFL thinning, a thinner optic rim, and a larger optic cup in preterm children and should be evaluated in each patient to prevent incorrect diagnosis like glaucoma.