Optic Nerve Fibers Research Articles

Anatomical and functional changes after internal limiting membrane peeling.

Internal limiting membrane (ILM) peeling has been an acceptable step in vitrectomy surgeries for various retinal diseases such as macular hole, chronic macular edema following epiretinal membrane (ERM), and vitreoretinal traction. Despite all the benefits, this procedure has some side effects, which may lead to structural damage and functional vision loss. Light and dye toxicity may induce reversible and irreversible retina damage, which will be observed in postoperative optical coherence tomography scans. Retinal nerve fiber layer damage is attributed to ganglion cell degeneration and axonal transport alteration, and dissociated optic nerve fiber layer is due to Müller cell damage. Eccentric MHs and recurrence of previous MHs may also lead to vision loss. Iatrogenic retinal damage may cause structural retinal changes without significant vision loss or progression to choroidal neovascularization. The mechanism of persistent macular edema after membrane peeling is still unclear, but it has been related to tractional trauma and blood-retina barrier damage. The reappearance of ERM is another cause of decreased vision after ILM peeling, which might be secondary to incomplete membrane removal. In glaucoma patients, ILM peeling is associated with significantly worsening the mean deviation on the visual field test after the surgery. We discussed various causes of vision loss and structural changes following ILM peeling. These causes may be attributed to the surgical procedure itself or the associated steps, instruments, and dyes used during the ILM peeling procedure.

Peripapillary and Macular Microvasculature of the Retina in Primary Angle Closure Suspect

Purpose: To compare the macular and peripapillary vascular parameters between the primary angle closure suspect (PACS) eyes and normal control eyes using optical coherence tomography angiography (OCTA).Methods: In this retrospective study, 42 PACS subjects and 38 normal individuals are included. Vessel density (VD) and perfusion density (PD) of the macular area and peripapillary area, and fovea avascular zone parameter were analyzed using OCTA and compared between two groups after adjustment for the axial length.Results: There were no statistically significant differences in sex ratio, age, refractive errors and intraocular pressures between both groups. In the peripapillary area, inferior VD and PD in the outer zone were significantly lower in the PACS eyes, while the retinal nerve fiber layer thicknesses were similar between groups (<i>p</i> = 0.032, 0.026). In the macular superficial capillary plexus, inferior VD and PD in the inner zone, inferior VD and PD, nasal VD and PD in the outer zone were significantly lower in the PACS eyes, whereas ganglion cell inner plexiform layer thickness were similar between both groups (all <i>p</i> < 0.005).Conclusions: The VDs and PDs of retinal capillaries in PACS eyes, which have no glaucomatous changes in the retinal nerve fiber layer and optic nerve disc, were significantly lower compared to normal eyes.

Comparative analysis of methods in detecting glaucomatous progression

Aims/Purpose: Glaucoma is an optic neuropathy that, if left untreated, leads to irreversible blindness, making reliable methods for detecting progression essential. Functional damage is assessed by the reduction of the visual field (VF), and structural damage is evaluated by the thinning of retinal parameters. Since 50% of ganglion cells are located in the macular area, their study could be a good indicator of progression. The objective of this work is to evaluate the utility of ganglion cell layer (GCL) analysis using optical coherence tomography (OCT) in diagnosing glaucoma progression.Methods: This is a retrospective cross‐sectional study including 205 eyes with glaucoma followed for at least three years. The progression analysis values obtained from OCT of the GCL and the optic nerve fiber layer (NFL) are compared, taking the VF as a reference and stratifying by severity into mild and moderate‐advanced glaucoma.Results: In mild glaucoma, VF has limitations because functional damage does not occur until there is a 20‐40% loss of ganglion cells. Structural tests classify more cases as progression, and the concordance between them is higher than with VF. OCT of the GCL is the test that classifies progression the most. In moderate‐advanced glaucoma, VF classifies more cases than in mild glaucoma. However, VF is a variable test, influenced by the learning effect, and when damage is very advanced, results can be erroneous because the retina loses sensitivity. OCT of the NFL classifies fewer cases than in mild glaucoma because debris creates a floor effect that artifacts the measurement. OCT of the GCL is the test that classifies progression the most. The concordance is greater between OCT of the GCL and VF.Conclusions: In conclusion, OCT of the GCL may be a better indicator of progression than NFL in both mild and moderate‐advanced glaucoma. It could be a useful strategy in clinical practice for diagnosing glaucomatous progression.References Munuera I, Gándara‐Rodriguez de Campoamor E, Moreno‐Montañes J. Study of the ganglion cell complex of the macula by optical coherence tomography in the diagnosis of glaucoma progression. Arch Soc Esp Oftalmol (Engl Ed). 2024 Apr;99(4):145‐151.

Effect of Ripasudil on the Change Rates of the Circumpapillary Retinal Nerve Fiber Layer Thickness in Patients With Primary Open-Angle Glaucoma.

Purpose: The effect of the Rho-kinase inhibitor ripasudil on the retinal optic nerve fiber layer (RNFL) remains unclear. We aimed to determine this effect in patients with primary open-angle glaucoma (POAG) using optical coherence tomography (OCT) measurements and linear mixed analysis. Methods: This study prospectively included outpatients from a single center with POAG without a history of vitreoretinal or glaucoma surgery from December 2014 to June 2020, in whom the circumpapillary RNFL thickness (cpRNFLT) was measured more than three times before and after ripasudil initiation, without additional medication or surgery during the period. Measurements were performed using OCT in the follow-up mode. The cpRNFLT change rates were compared before and after treatment using linear mixed models with adjustments for intraocular pressure (IOP) changes. Results: Thirty eyes of 20 patients (12 males and eight females) were included. Upon ripasudil prescription, the average cpRNFLT was 60.2 ± 2.1 μm. The average IOP was 15.1 ± 0.5 and 13.5 ± 0.5 mmHg, respectively, before and after treatment initiation, with a difference of -1.6 ± 0.3 mmHg. Analysis of 343 cpRNFLT measurements using linear mixed models revealed that the cpRNFLT change rate was -0.91 ± 0.15 and -0.40 ± 0.14 μm/year, respectively, before and after treatment onset, with an increase of 0.51 ± 0.21 μm/year. After adjusting for IOP changes, the improvement in cpRNFLT change rate was 0.33 ± 0.23 μm/year, albeit not statistically significant. Conclusion: The cpRNFLT change rate significantly increased after ripasudil administration, whereas the contribution of the IOP decline was not significant.

Glaucoma and dietary intake: a scoping review

IntroductionStudies have suggested that dietary intake may influence the incidence and progression of open-angle glaucoma. However, dietary modification is not usually included in the clinical management of glaucoma. The aim of this scoping review was therefore to map the evidence and determine the nature and extent of research done on “diet and glaucoma” and identify any gaps in this area of scholarship.Materials and methodsA comprehensive search of academic literature was conducted from two relevant electronic databases: PubMed and ScienceDirect. Primary studies that explored the relationship between dietary intake and glaucoma were included if the principal exposure was “diet” and if dietary habits were assessed with dietary questionnaires. The glaucoma outcomes of interest were visual field, retinal nerve fibre layer and/or optic nerve head features.ResultsNineteen studies were included in the final qualitative synthesis. The dates of publication ranged from 2003 to 2023. About 80% of the studies found some significant associations between glaucoma and dietary intake. However, most studies (95%) were observational, i.e., 7 (37%) used a cross-sectional design, 10 (53%) used a prospective cohort design; and 1 (or 5%) used a nested case–control study design. Only 1 study (or 5%) used a randomized intervention trial. Furthermore, while all studies investigated dietary intake with questionnaires, only 2 studies (or 11%) went further to include assessment of nutritional biomarkers.ConclusionAlthough miscellaneous evidence supports the concept that diet may play a role in glaucoma, most data are unfortunately observational without proven causality, reporting associations from subjective dietary questionnaires. More well-designed studies are required, especially randomized controlled trials that can prove causality.

Subsurface multi-physical monitoring of urban development zone using a fiber optic nerve system

Subsurface multi-physical monitoring of urban development zone using a fiber optic nerve system

Challenges in identifying papilledema amid myopic peripapillary atrophy in a patient with idiopathic intracranial hypertension and high myopia: a case report

BackgroundIdiopathic intracranial hypertension (IIH) is a disease entity characterized by elevated intracranial pressure, which usually accompanied by papilledema. However, diagnosing papilledema can be challenging in patients with preexisting ocular conditions, such as high myopia.Case presentationA 39-year-old woman with a long-standing history of high myopia presented with visual field constriction. Her visual acuity was decreased in both eyes, and she also reported morning headaches, pulsatile tinnitus, and intermittent periocular pain. Although she was diagnosed with IIH based on a cerebrospinal fluid study, there was no evident papilledema, which may have been masked by myopic changes in optic nerve and peripapillary retinal nerve fiber layer. After treatment for IIH with acetazolamide, her visual field and visual acuity markedly improved, and her symptoms were relieved.ConclusionsIn highly myopic patients, myopic changes in optic nerve head may obscure papilledema, complicating the diagnosis of IIH. This unusual case highlights the need for detailed history taking and a comprehensive clinical evaluation in patients with high myopia. Clinicians should suspect IIH in the presence of symptoms such as pulsatile tinnitus, morning headache, and visual field constriction, even in the absence of evident papilledema.

Clinical and Structural Parameters in Autosomal Dominant Optic Atrophy Patients: A Cross-Sectional Study Using Optical Coherence Tomography.

Autosomal Dominant Optic Atrophy (ADOA) is a hereditary optic neuropathy characterized by retinal ganglion cell degeneration and optic nerve fiber loss. This study examined the correlation between clinical and structural parameters in patients with ADOA using optical coherence tomography (OCT) and explored potential clinical biomarkers. A cross-sectional, case-control observational study included 27 patients with ADOA and 27 age- and sex-matched healthy controls. Clinical examinations, OCT imaging, and OCT angiography (OCTA) were performed. Statistical analyses were conducted to establish correlations between clinical and OCT parameters. Patients with ADOA exhibited gradual bilateral vision loss, central scotomas, and optic disc pallor. Structural OCT analysis revealed significant reductions in central macular thickness, macular volume, ganglion cell complex (GCC), and peripapillary retinal nerve fiber layer compared with controls. Correlation analysis demonstrated associations between worsening clinical parameters (best corrected visual acuity, Sloan Letters Low Contrast Chart 25%, Pseudoisochromatic Test) and increased OCT damage (structural and OCTA). GCC emerged, at least at exploratory terms, as the most important clinical biomarker in patients with ADOA given its multiple positive functional associations, while OCTA parameters correlated with visual field defects. Our study revealed significant correlations between clinical and structural parameters in patients with ADOA, highlighting the importance of OCT in assessing disease severity. GCC measurement shows promise as a clinical biomarker, aiding in disease monitoring. OCTA parameters offer potential early biomarkers for vascular changes. These findings contribute to understanding ADOA pathophysiology and may improve patient diagnosis and management. Further research is warranted to validate these findings and explore potential therapeutic interventions.

Imprint of preterm birth with very low birth weight on optic disc OCT in adulthood-A two-country birth cohort study.

To determine the pattern, degree and prevalence of optic disc optical coherence tomography (OCT) alterations in adults born preterm with very low birth weight (VLBW; birth weight < 1500 g). Optic disc OCT was assessed in 98 VLBW participants and 139 term-born controls from birth cohorts in Finland and Norway at the mean age of 36 years. The participants had not been treated for retinopathy of prematurity and had no diagnosed brain abnormality. OCT assessment included parameters for optic disc size, neural rim and peripapillary retinal nerve fibre layer thickness (pRNFLT), and for the foveal developmental stage. Background data, visual acuity, refractive error and intraocular pressure were recorded. In the VLBW group, optic disc neural rim and pRNFLT were significantly decreased, most frequently in the nasal and inferior sectors. In 40% (95% CI: 33-47) of the VLBW eyes, nerve fibre thickness of at least one optic disc sector was below the fifth percentile of the control group, including 9% (95% CI: 6-14) subgroup falling below the first percentile, that is, clinically below normal limits. VLBW participants with nerve fibre thickness below the fifth percentile did not differ by perinatal data or foveal developmental stage from the other VLBW participants. All participants had normal visual acuity. A moderate decrease of the optic disc neural rim and pRNFLT is frequently seen in clinically healthy adults born preterm with VLBW. Awareness of the VLBW-related optic disc nerve fibre shallowness especially in the inferior and nasal sectors is important while evaluating acquired optic disc pathology in adulthood.

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.

Delayed Surgical Reversal of Optic Nerve Compression Leads to Exponential Degeneration of Optic Nerve Fibers and Selective Sparing of the Small Fibers.

To evaluate the effectiveness of surgical reversal of experimental optic nerve compression in treating persistent compressive optic neuropathy and to explore the relationship between surgical outcomes and the timing of the procedure. Surgical reversal procedures (decompression surgery) were conducted at five time intervals: 1, 3, and 7 days and 2 and 3 weeks following optic nerve compression in a rabbit model. The groups were labeled as DC-1d, DC-3d, DC-7d, DC-2w, and DC-3w, respectively. The study investigated changes in ganglion cell complex (GCC) thickness using spectral-domain optical coherence tomography and the percentage of surviving retinal ganglion cells (RGCs) through immunofluorescence staining and optic nerve axons stained with p-phenylenediamine at 4 weeks after decompression. Additionally, the area distribution of surviving axons was analyzed. The decline in GCC thickness was halted following decompression. The remaining thickness of the GCC in group DC-1d was found to be statistically significantly higher at 2, 3, and 4 weeks postonset compared to the no-decompression group. Similarly, GCC thickness in group DC-3d was significantly higher at 3 and 4 weeks postonset. The percentage of surviving RGCs and axons at 4 weeks postonset exhibited an exponential correlation with the onset time of decompression, with R2 values of 0.72 and 0.78, respectively. The surviving axon area declined following delayed decompression. Persistent substantial compression on the optic nerve leads to exponential degeneration of the optic nerve, initially affecting larger optic nerve fibers. Early intervention aimed at relieving the compression on the optic nerve may offer potential benefits in mitigating the degenerative effects and conserving visual function.

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.

Morphometric, immunohistochemical and ultrastructural examination of age-related structural alterations in optic nerve

Aims: As individuals age, there is a known decline in visual function attributed to a reduction in the optic nerve fibers and myelin sheath degeneration. Studies present conflicting findings on whether aging affects axonal integrity in the human optic nerve. This study aims to investigate degenerative changes in the aging rat optic nerve. Methods: The investigation involved 36 Wistar albino rats. The rats were divided into six groups: the newborn, prepubertal, pubertal, junior, adult, and elderly groups. This study investigated optic nerve axon counts, axon diameters, levels of glial fibrillary acidic protein immunoreactivity (GFAP-IR) and nerve growth factor immunoreactivity (NGF-IR), as well as findings from light microscopy (LM) and electron microscopy (EM) in these groups. Results: This study observed age-related alterations in rat optic nerves, including increased diameter, irregular axon count fluctuations (both increases and decreases), elevated astrocyte count, and a simultaneous decline in oligodendrocyte count. Additionally, it was observed that NGF-IR was predominantly at the membrane level in newborns and moderately in the cytoplasm, whereas in older ages, it was evident at both cellular and axonal levels furthermore, it was observed that GFAP-IR increased with age. However, in LM and EM examinations, axonal loss and rarefaction, accumulation of osmiophilic substances, splitting of the myelin sheath, vacuolization, axonal retraction were observed. Conclusion: In this study, it was found that one of the causes of age-related vision loss is the advanced degenerative changes in the optic nerve and it was concluded that the remaining small-diameter myelinated nerve fibers may partially compensate for the sense of vision. Our study reveals that age-related degenerative changes in the central nervous system resemble those in multiple sclerosis (MS), suggesting a potential contribution to MS pathogenesis.

Secondary silicone-induced glaucoma after vitrectomy for regmatogenic retinal detachment

BACKGROUND: Retinal detachment is a leading cause of impaired vision and blindness, affecting 2–9% of individuals. Research has shown that local immune-inflammatory processes contribute significantly to the development of this condition. Polymethylsiloxane has long been used as a tamponade substance in the treatment of retinal detachment. It is currently utilized in various forms of retinal detachment as well as in the management of complications such as retinal edge folding and vitreous opacity. However, the use of silicone oil in the vitreous cavity can lead to the development of secondary ocular hypertension and glaucoma, with prevalence rates ranging from 2.2% to 64.2% according to studies. AIM: Conduct a comparative analysis of biochemical and morphometric indicators and justify the expediency of conducting immune therapy for patients with secondary silicone-induced glaucoma. METHODS: A prospective study included 22 patients (22 eyes) in the main group and 22 patients in the comparison group (22 eyes). The average age of the patients was 55±5.3 years (46–68 years), with 28 females and 16 males. Patients in the main group received anti-cytokine therapy (aminopropyldithioethylene-diamine sodium and anakinra). The primary endpoint of the study was the assessment of retinal nerve fiber layer thickness and perimetric indices. RESULTS: The results revealed an inverse relationship between cytokine levels and retinal nerve fiber layer thickness in patients who underwent vitrectomy with silicone tamponade. Additionally, a direct relationship was observed between the diameter of emulsified silicone in the anterior chamber and cytokine levels. The impact of mechanical fragmentation of polymethylsiloxane during nystagmus and direct toxic effects on optic nerve fibers requires further investigation. The study also highlighted the need for more accurate methods of selecting anterior chamber fluid for evaluating the effectiveness of immune therapy. Determining the appropriate dosage, duration, and administration method of anti-cytokine drugs also requires further research. Evaluation of ophthalmotonometric indicators, retinal nerve fiber layer thickness, and mean deviation revealed significantly better outcomes in patients receiving anti-cytokine therapy compared to the control group. CONCLUSION: The findings of this study support the use of anti-cytokine therapy to normalize biochemical parameters in the anterior chamber and reduce clinical manifestations of secondary silicone-induced glaucoma.

Optic nerve head and retinal nerve fiber layer changes by spectral domain optical coherence tomography in glaucoma suspects at tertiary care hospital

Introduction: Glaucoma is a progressive optic neuropathy characterized by functional loss or optic nerve dysfunction which is one of the leading causes of irreversible but preventable blindness. The aim of the study was to determine which of the retinal nerve fiber layer and optic nerve head parameters are reliable markers of optic nerve damage in glaucoma suspects. Methods: Observational cross-sectional study of 250 patient’s including147 glaucoma suspect eyes, 103 normal eyes. All subjects underwent complete eye examination and imaging with the spectral domain optical coherence tomography (SD-OCT) cirrus-TM OCT (Carl Zeiss Meditec, Dublin, CA). Retinal nerve fiber layer (RNFL) and optic nerve head (ONH) OCT protocols were used to evaluate all study participants. The main outcome measures were the difference in OCT parameters among groups. Results: Study shows statistically significant difference in the average RNFL thickness, superior, nasal, inferior, temporal quadrants, rim area, cup volume, average cup to disc ratio (CDR), vertical CDR with P value &lt;0.001 between the two groups. Average CDR, vertical CDR and cup volume had significantly greater AROC values (ROC: 0.99, 0.98, 0.95) than RNFL parameters for discriminating glaucoma suspects from normal eyes. Conclusion: Assessment of RNFL, macular and ONH damage with SD-OCT has been proven useful for diagnosing the disease at different levels of severity, as well as for quantifying risk in glaucoma suspects. In our study ONH measurements, as provided by the SD OCT, have more diagnostic value than RNFL parameters in the diagnosis of glaucoma suspects from normal. Keywords: glaucoma suspects; optic nerve head; retinal nerve fiber layer; optical coherence tomography

Maculopapillary Bundle Degeneration in Optic Neuropathies.

Degeneration of the maculopapillary bundle (MPB) is a prominent feature in a spectrum of optic neuropathies. MPB-selective degeneration is seen in specific conditions, such as nutritional and toxic optic neuropathies, Leber hereditary optic neuropathy (LHON), and dominant optic atrophy (DOA). Despite their distinct etiologies and clinical presentations, which encompass variations in age of incidence and monocular or binocular onset, these disorders share a core molecular mechanism: compromised mitochondrial homeostasis. This disruption is characterized by dysfunctions in mitochondrial metabolism, biogenesis, and protein synthesis. This article provides a comprehensive understanding of the MPB's role in optic neuropathies, emphasizing the importance of mitochondrial mechanisms in the pathogenesis of these conditions. Optical coherence tomography studies have characterized the retinal nerve fiber layer changes accompanying mitochondrial-affiliated optic neuropathies. Selective thinning of the temporal optic nerve head is preceded by thickening in early stages of these disorders which correlates with reductions in macular ganglion cell layer thinning and vascular atrophy. A recently proposed mechanism underpinning the selective atrophy of the MPB involves the positive feedback of reactive oxygen species generation as a common consequence of mitochondrial dysfunction. Additionally, new research has revealed that the MPB can undergo degeneration in the early stages of glaucoma, challenging the historically held belief that this area was not involved in this common optic neuropathy. A variety of anatomical risk factors influence the propensity of glaucomatous MPB degeneration, and cases present distinct patterns of ganglion cell degeneration that are distinct from those observed in mitochondria-associated diseases. This review synthesizes clinical and molecular research on primary MPB disorders, highlighting the commonalities and differences in their pathogenesis. 1.Temporal degeneration of optic nerve fibers accompanied by cecocentral scotoma is a hallmark of maculopapillary bundle (MPB) degeneration. 2.Mechanisms of MPB degeneration commonly implicate mitochondrial dysfunction. 3.Recent research challenges the traditional belief that the MPB is uninvolved in glaucoma by showing degeneration in the early stages of this common optic neuropathy, yet with features distinct from other MPB-selective neuropathies. 4.Reactive oxygen species generation is a mechanism linking mitochondrial mechanisms of MPB-selective optic neuropathies, but in-vivo and in-vitro studies are needed to validate this hypothesis.

Changes in the level of tyrosinase expression in the retinal pigment epithelium during the development of experimental optic nerve degeneration

BACKGROUND: With optic nerve degeneration of various origins, retinal neurons are the most vulnerable, and their state under these conditions has been studied in sufficient detail. At the same time, the retinal pigment epithelium plays a very important role, realizing the synthesis of melanin and performing antioxidant, phagocytic, transport, protective, and homeostatic functions. Tyrosinase serves as a key enzyme in melanogenesis by cells of this epithelium. The development of methods for early diagnosis of optic nerve atrophy is extremely important due to the fact that functional visual impairments appear later than structural ones, at more advanced stages of the disease. The retinal pigment epithelium cannot be insensitive to the processes that occur during optic nerve degeneration. That is why its study in experimental degeneration of the optic nerve is necessary for a more complete understanding of the processes occurring in the visual analyzer under these conditions. AIM: To study changes in the level of tyrosinase expression in the retinal pigment epithelium at different development stages of experimental optic nerve degeneration based on morphological data. MATERIAL AND METHODS: The subjects of the study were 40 rat eyes after creating a model of optic nerve atrophy using methanol. The animals were divided into five groups: the first group — control; the second to fifth groups included animals whose eyes were enucleated 1, 3, 6 and 9 weeks after the creation of the aminophylline-methanol model of optic nerve atrophy, respectively. The retinal pigment epithelium was studied using fluorescent antibodies to tyrosinase Tyrosinase Mouse Monoclonal. Immunofluorescence staining was performed on fixed transverse sections of the eyeball. Statistical analysis and visualization of the obtained data were carried out using the environment for statistical computing R 4.2.2. RESULTS: A comparative analysis of the results obtained revealed that the level of tyrosinase expression in the fifth group was on average 4.21 times [95% confidence interval (CI) 2.49–7.13, p=0.00076], 9.31 times (95% CI 5.47–15.85, p=0.00033), 2.63 times (95% CI 1.51–4.58, p=0.0009) and 3.44 times (95% CI 1.96–6.03, p=0.00055) higher compared to the first, second, third and fourth groups, respectively. The level of tyrosinase in experimental samples in the first, third and fourth groups was statistically higher compared to the level of tyrosinase in the second group by an average of 2.21 times (95% CI 1.33–3.66, p=0.0003), 3.53 times (95% CI 2.08–6.02, p=0.00069) and 2.71 times (95% CI 1.58–4.65, p=0.00022), respectively. CONCLUSION: As degenerative processes develop in the optic nerve fibers under these conditions, the integrity of the retinal pigment epithelium is disrupted, which is characterized by an increase in antibodies to tyrosinase in the retinal pigment epithelium of experimental animals.

Neuron mapping in the Molly fish optic tectum: An emphasis on the adult neurogenesis process.

Teleost fish exhibit the most pronounced and widespread adult neurogenesis. Recently, functional development and the fate of newborn neurons have been reported in the optic tectum (OT) of fish. To determine the role of neurogenesis in the OT, this study used histological, immunohistochemical, and electron microscopic investigations on 18 adult Molly fish specimens (Poecilia sphenops). The OT of the Molly fish was a bilateral lobed structure located in the dorsal part of the mesencephalon. It exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. The stratum opticum (SO) was supplied by optic nerve fibers, in which the neuropil was the main component. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). Furthermore, oligodendrocytes with their processes wrapped around the nerve fibers could be observed. The stratum album centrale (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. The neuronal cells of the SO and large tectal cells of the SAC expressed autophagy-related protein-5 (APG5). Interleukin-1β (IL-1β) was expressed in both neurons and glia cells of SGC. Additionally, inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventriculare (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. In all strata, S100 protein and Oligodendrocyte Lineage Transcription Factor 2 (Olig2) were expressed by microglia, oligodendrocytes, and astrocytes. In conclusion, it was possible to identify different varieties of neurons in the optic tectum, each with a distinct role. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT. RESEARCH HIGHLIGHTS: The OT of the Molly fish exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). The stratum album central (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. Inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventricular (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT.

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.