Maternal-Fetal Conflicts in Anesthesia Practice.

Anesthesia clinicians often navigate a delicate balance between maternal and fetal safety. Interventions for at fetal well-being may introduce risks of harm to the mother and raise ethical dilemmas. Emergency procedures often focus on direct fetal safety, sidelining maternal physical and mental well-being. The clash between ethical principles, particularly nonmaleficence and beneficence, often arises, with maternal autonomy guiding decisions. Fetal surgery exemplifies risking maternal health for fetal benefit, whereas emergent cesarean deliveries pose physical and psychological challenges for both the mother and child.

SLC25A48 influences plasma levels of choline and localizes to the inner mitochondrial membrane.

Choline contributes to the biogenesis of methyl groups, neurotransmitters, and cell membranes. Our genome-wide association study (GWAS) of circulating choline in 2228 college students found that alleles in SLC25A48 (rs6596270) influence choline concentrations in men (p = 9.6 × 10-8), but not women. Previously, the subcellular location and function of SLC25A48 were unknown. Using super-resolution immunofluorescence microscopy, we localized SLC25A48 to the inner mitochondrial membrane. Our results suggest that SLC25A48 transports choline across the inner mitochondrial membrane.

Exome sequencing identifies novel genes underlying primary congenital glaucoma in the National Birth Defects Prevention Study.

BACKGROUND: Primary congenital glaucoma (PCG) affects approximately 1 in 10,000 live born infants in the United States (U.S.). PCG has a autosomal recessive inheritance pattern, and variable expressivity and reduced penetrance have been reported. Likely causal variants in the most commonly mutated gene, CYP1B1, are less prevalent in the U.S., suggesting that alternative genes may contribute to the condition. This study utilized exome sequencing to investigate the genetic architecture of PCG in the U.S. and to identify novel genes and variants. METHODS: We studied 37 family trios where infants had PCG and were part of the National Birth Defects Prevention Study (births 1997-2011), a U.S. multicenter study of birth defects. Samples underwent exome sequencing and sequence reads were aligned to the human reference sample (NCBI build 37/hg19). Variant filtration was conducted under de novo and Mendelian inheritance models using GEMINI. RESULTS: Among candidate variants, CYP1B1 was most represented (five trios, 13.5%). Twelve probands (32%) had potentially pathogenic variants in other genes not previously linked to PCG but important in eye development and/or to underlie Mendelian conditions with potential phenotypic overlap (e.g., CRYBB2, RXRA, GLI2). CONCLUSION: Variation in the genes identified in this population-based study may help to further explain the genetics of PCG.

Gestational exposure to organochlorine compounds and metals and infant birth weight: effect modification by maternal hardships.

BACKGROUND: Gestational exposure to toxic environmental chemicals and maternal social hardships are individually associated with impaired fetal growth, but it is unclear whether the effects of environmental chemical exposure on infant birth weight are modified by maternal hardships. METHODS: We used data from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a pan-Canadian cohort of 1982 pregnant females enrolled between 2008 and 2011. We quantified eleven environmental chemical concentrations from two chemical classes - six organochlorine compounds (OCs) and five metals - that were detected in ≥ 70% of blood samples collected during the first trimester. We examined fetal growth using birth weight adjusted for gestational age and assessed nine maternal hardships by questionnaire. Each maternal hardship variable was dichotomized to indicate whether the females experienced the hardship. In our analysis, we used elastic net to select the environmental chemicals, maternal hardships, and 2-way interactions between maternal hardships and environmental chemicals that were most predictive of birth weight. Next, we obtained effect estimates using multiple linear regression, and plotted the relationships by hardship status for visual interpretation. RESULTS: Elastic net selected trans-nonachlor, lead, low educational status, racially minoritized background, and low supplemental folic acid intake. All were inversely associated with birth weight. Elastic net also selected interaction terms. Among those with increasing environmental chemical exposures and reported hardships, we observed stronger negative associations and a few positive associations. For example, every two-fold increase in lead concentrations was more strongly associated with reduced infant birth weight among participants with low educational status (ß = -100 g (g); 95% confidence interval (CI): -215, 16), than those with higher educational status (ß = -34 g; 95% CI: -63, -3). In contrast, every two-fold increase in mercury concentrations was associated with slightly higher birth weight among participants with low educational status (ß = 23 g; 95% CI: -25, 71) compared to those with higher educational status (ß = -9 g; 95% CI: -24, 6). CONCLUSIONS: Our findings suggest that maternal hardships can modify the associations of gestational exposure to some OCs and metals with infant birth weight.

Prevalence of contraindicated combinations amid behavioral and mental health medications filled in a pediatric population.

BACKGROUND: Behavioral or mental health disorders are common in children, adolescents, and young adults. Medication use is increasingly common, with few data describing drug-drug combinations in ambulatory settings. The objectives of this study were to describe the pharmaco-epidemiology of behavioral and mental health (BMH) medications among children, adolescents, and young adults in New York Medicaid and assess the prevalence of contraindicated drug pairs within this population. METHODS: This observational cross-sectional study evaluated New York State Medicaid managed care and fee-for-service enrollees under 21 years of age dispensed BMH medications in 2014. Main outcomes included number of members with prescriptions filled; number filling > 1 medication prescription concurrently for ≥ 30 days (polypharmacy), and number and nature of potentially contraindicated drug pairs. RESULTS: Of 2,430,434 children, adolescents, and young adults, 422,486 (17.4%) had a visit associated with a BMH diagnosis and 141,363 (5.8%) received one or more BMH medications. With 84 distinct medications evaluated, polypharmacy was common, experienced by 53,388 individuals (37.8% of those with a prescription filled), generating 11,115 distinct drug combinations. 392 individuals filled prescriptions for a contraindicated pair of ≥ 2 BMH medications for 30 days or longer. With ≥ 1 day overlap, 651 were exposed to contraindicated medications. The most common contraindicated pairs increased potential risk for prolonged QT interval and serotonin syndrome (n = 378 and n = 250 patients, respectively). Most combinations involved ziprasidone (3247.1 per 10,000 ziprasidone prescriptions filled). CONCLUSIONS: With nearly 6% of members dispensed a BMH medication, contraindicated drug pairs were uncommon. However, any of those combinations represent a potential risk. Clinicians should attend to the balance of potential risks and benefits before contraindicated pairs are dispensed. The methodology described could serve as a basis for monitoring such rare instances and might reduce harm.

Factors Affecting Implant Length in Primary Inflatable Penile Prosthesis Placement.

OBJECTIVE: To evaluate predictors of implant length for men undergoing primary IPP placement. METHODS: A multicenter, retrospective cohort study was performed for men undergoing primary IPP placement at 16 high-volume surgical centers. Patient demographics, comorbidities, operative approach, and implanted cylinder and rear-tip extender length were recorded. Associations between potential preoperative and intraoperative predictors of total device length were tested using non-parametric correlation and Kruskal-Wallis tests, followed by multiple regression. RESULTS: Of 3951 men undergoing primary IPP placement from July 2016 to July 2021, the median implant length was 20 cm (IQR: 19-22). Shorter implant length was associated with increasing age in years (ß = -0.01, P = .009), Asian ethnicity (ß = -2.34, P = .008), history of radical prostatectomy (ß = -0.35, P = .001), and use of an infrapubic surgical approach (ß = -1.02, P <.001). Black or African American ethnicity was associated with the implantation of longer devices (ß = 0.35, P <.001). No significant associations were recorded with BMI, history of intracavernosal injections, diabetes mellitus, tobacco use, radiation therapy, Peyronie's disease, priapism, or cavernosal dilation technique. CONCLUSION: The length of an implanted penile prosthesis was found to be associated with preoperative and intraoperative factors including history of radical prostatectomy and operative approach. The knowledge of these associations may assist in the preoperative counseling of patients receiving IPP and help create accurate postoperative expectations.

Infectious disease surveillance needs for the United States: lessons from Covid-19.

The COVID-19 pandemic has highlighted the need to upgrade systems for infectious disease surveillance and forecasting and modeling of the spread of infection, both of which inform evidence-based public health guidance and policies. Here, we discuss requirements for an effective surveillance system to support decision making during a pandemic, drawing on the lessons of COVID-19 in the U.S., while looking to jurisdictions in the U.S. and beyond to learn lessons about the value of specific data types. In this report, we define the range of decisions for which surveillance data are required, the data elements needed to inform these decisions and to calibrate inputs and outputs of transmission-dynamic models, and the types of data needed to inform decisions by state, territorial, local, and tribal health authorities. We define actions needed to ensure that such data will be available and consider the contribution of such efforts to improving health equity.

Intracerebral Hemorrhage in a Child with Renal Artery Stenosis and COVID-19.

Pediatric intracerebral hemorrhage is a rare condition among children. We discuss the case of a 7-year-old Filipino male with generalized tonic seizures and diagnosed to have both SARS-CoV-2 infection and hypertension secondary to renal arterial stenosis. The occurrence of intracerebral hemorrhage in children, though commonly caused by arteriovenous malformations, may be secondary to an acute hypertensive episode. In this case, the presence of COVID-19 in the patient may have been contributory to the development of spontaneous intracerebral hemorrhage due to its direct endothelial effects, as well as its dysregulatory action on the renin-angiotensin-aldosterone system.

Identification of rare genetic variants in the PCDH genetic family in a cohort of transgender women.

OBJECTIVE: To study the identification of rare genetic variants in the PCDH genetic family in a cohort of transgender women (TGW) and their potential role in gender identity. DESIGN: Exome sequencing and functional ontology analysis. SETTING: Outpatient gender health and reproductive endocrinology clinics. PATIENT(S): A total of 24 TGW and 22 cisgender men (CM). INTERVENTION(S): Exome sequencing followed by variant confirmation through Sanger sequencing and functional classification analysis using the Database for Annotation, Visualization, and Integrated Discovery tool. MAIN OUTCOME MEASURE(S): Identification of rare, functionally significant genetic variants in the PCDH gene family and their prevalence in TGW compared with CM. RESULT(S): Exome sequencing revealed 38,524 genetic variants, of which 2,441 were rare and predicted to be functionally significant. The Database for Annotation, Visualization, and Integrated Discovery analysis demonstrated a statistically enriched functional group, "homophilic cell adhesion via plasma membrane adhesion molecules," containing 55 genes, including 18 PCDH gene family members. A total of 37 rare variants in 21 PCDH genes were identified, with 36 confirmed using Sanger sequencing. A statistically significant increase in these variants was observed in TGW compared with CM (Z = 2.08905). CONCLUSION(S): Transgender women exhibited a greater than threefold increase in functionally significant PCDH gene variants compared with CM. These findings suggest that the PCDH family may play a role in the genetic pathways associated with gender identity in TGW.

Researching COVID to enhance recovery (RECOVER) pediatric study protocol: Rationale, objectives and design.

IMPORTANCE: The prevalence, pathophysiology, and long-term outcomes of COVID-19 (post-acute sequelae of SARS-CoV-2 [PASC] or "Long COVID") in children and young adults remain unknown. Studies must address the urgent need to define PASC, its mechanisms, and potential treatment targets in children and young adults. OBSERVATIONS: We describe the protocol for the Pediatric Observational Cohort Study of the NIH's REsearching COVID to Enhance Recovery (RECOVER) Initiative. RECOVER-Pediatrics is an observational meta-cohort study of caregiver-child pairs (birth through 17 years) and young adults (18 through 25 years), recruited from more than 100 sites across the US. This report focuses on two of four cohorts that comprise RECOVER-Pediatrics: 1) a de novo RECOVER prospective cohort of children and young adults with and without previous or current infection; and 2) an extant cohort derived from the Adolescent Brain Cognitive Development (ABCD) study (n = 10,000). The de novo cohort incorporates three tiers of data collection: 1) remote baseline assessments (Tier 1, n = 6000); 2) longitudinal follow-up for up to 4 years (Tier 2, n = 6000); and 3) a subset of participants, primarily the most severely affected by PASC, who will undergo deep phenotyping to explore PASC pathophysiology (Tier 3, n = 600). Youth enrolled in the ABCD study participate in Tier 1. The pediatric protocol was developed as a collaborative partnership of investigators, patients, researchers, clinicians, community partners, and federal partners, intentionally promoting inclusivity and diversity. The protocol is adaptive to facilitate responses to emerging science. CONCLUSIONS AND RELEVANCE: RECOVER-Pediatrics seeks to characterize the clinical course, underlying mechanisms, and long-term effects of PASC from birth through 25 years old. RECOVER-Pediatrics is designed to elucidate the epidemiology, four-year clinical course, and sociodemographic correlates of pediatric PASC. The data and biosamples will allow examination of mechanistic hypotheses and biomarkers, thus providing insights into potential therapeutic interventions. CLINICAL TRIALS.GOV IDENTIFIER: Clinical Trial Registration: http://www.clinicaltrials.gov. Unique identifier: NCT05172011.

CUREs for high-level Galectin-3 expression.

Galectins are a large and diverse protein family defined by the presence of a carbohydrate recognition domain (CRD) that binds ß-galactosides. They play important roles in early development, tissue regeneration, immune homeostasis, pathogen recognition, and cancer. In many cases, studies that examine galectin biology and the effect of manipulating galectins are aided by, or require the ability to express and purify, specific members of the galectin family. In many cases, E. coli is employed as a heterologous expression system, and galectin expression is induced with isopropyl ß-galactoside (IPTG). Here, we show that galectin-3 recognizes IPTG with micromolar affinity and that as IPTG induces expression, newly synthesized galectin can bind and sequester cytosolic IPTG, potentially repressing further expression. To circumvent this putative inhibitory feedback loop, we utilized an autoinduction protocol that lacks IPTG, leading to significantly increased yields of galectin-3. Much of this work was done within the context of a course-based undergraduate research experience, indicating the ease and reproducibility of the resulting expression and purification protocols.

Electronic Health Record-Based Algorithm for Monitoring Respiratory Virus-Like Illness.

Viral respiratory illness surveillance has traditionally focused on single pathogens (e.g., influenza) and required fever to identify influenza-like illness (ILI). We developed an automated system applying both laboratory test and syndrome criteria to electronic health records from 3 practice groups in Massachusetts, USA, to monitor trends in respiratory viral-like illness (RAVIOLI) across multiple pathogens. We identified RAVIOLI syndrome using diagnosis codes associated with respiratory viral testing or positive respiratory viral assays or fever. After retrospectively applying RAVIOLI criteria to electronic health records, we observed annual winter peaks during 2015-2019, predominantly caused by influenza, followed by cyclic peaks corresponding to SARS-CoV-2 surges during 2020-2024, spikes in RSV in mid-2021 and late 2022, and recrudescent influenza in late 2022 and 2023. RAVIOLI rates were higher and fluctuations more pronounced compared with traditional ILI surveillance. RAVIOLI broadens the scope, granularity, sensitivity, and specificity of respiratory viral illness surveillance compared with traditional ILI surveillance.

Heterozygous ZNHIT3 variants within the 17q12 recurrent deletion region are associated with Mayer-Rokitansky-Kuster Hauser (MRKH) syndrome.

The molecular basis of mullerian aplasia, also known as Mayer-Rokitansky-Kuster Hauser (MRKH) or congenital absence of the uterus and vagina, is largely unknown. We applied a multifaceted genetic approach to studying the pathogenesis of MRKH including exome sequencing of trios and duos, genome sequencing of families, qPCR, RT-PCR, and Sanger sequencing to detect intragenic deletions, insertions, splice variants, single nucleotide variants, and rearrangements in 132 persons with MRKH. We identified two heterozygous variants in ZNHIT3 localized to a commonly involved CNV region at chromosome 17q12 in two different families with MRKH. One is a frameshift, truncating variant that is predicted to interfere with steroid hormone binding of the LxxLL sequence of the C-terminal region. The second variant is a double missense/stopgain variant. Both variants impair protein expression in vitro. In addition, four more probands with MRKH harbored the stopgain variant without the nearby missense variant. In total, 6/132 (4.5%) of patients studied, including five with associated anomalies (type 2 MRKH), had ZNHIT3 variants that impair function in vitro. Our findings implicate ZNHIT3 as an important gene associated with MRKH within the 17q12 CNV region.

Prevalence of pathogenic variants and digenic disease in patients diagnosed with normosmic hypogonadotropic hypogonadism/Kallmann Syndrome.

BACKGROUND: Hypogonadotropic hypogonadism (HH) is due to impaired gonadotropin releasing hormone (GnRH) action resulting in absent puberty and infertility. At least 44 genes have been identified to possess genetic variants in 40-50% of nHH/KS, and 2-20% have presumed digenic disease, but not all variants have been characterized in vitro. HYPOTHESIS: The prevalence of pathogenic (P)/likely pathogenic (LP) variants in monogenic and digenic nHH/KS is lower than reported. DESIGN: Cross-sectional study. SETTING: University Research Laboratory. SUBJECTS: 158 patients with nHH/KS. METHODS: Exome sequencing (ES) was performed and variants were filtered for 44 known genes using Varsome and confirmed by Sanger Sequencing. MAIN OUTCOME MEASURES: P/LP variants in nHH/KS genes. RESULTS: ES resulted in >370,000 variants, from which variants in 44 genes were filtered. Thirty-one confirmed P/LP variants in 10 genes (ANOS1, CHD7, DUSP6, FGFR1, HS6ST1, KISS1, PROKR2, SEMA3A, SEMA3E, TACR3), sufficient to cause disease, were identified in 30/158 (19%) patients. Only 2/158 (1.2%) patients had digenic variant combinations: a male with hemizygous ANOS1 and heterozygous TACR3 variants and a male with heterozygous SEMA3A and SEMA3E variants. Two patients (1.2%) had compound heterozygous GNRHR (autosomal recessive) variants-one P and one variant of uncertain significance (VUS). Five patients (3.2%) had heterozygous P/LP variants in either GNRHR or TACR3 (both autosomal recessive), but no second variant. CONCLUSION: Our prevalence of P/LP variants in nHH/KS was 19%, and digenicity was observed in 1.2%. These findings are less than those previously reported, and probably represent a more accurate estimation since VUS are not included.

Necroptosis blockade prevents lung injury in severe influenza.

Severe influenza A virus (IAV) infections can result in hyper-inflammation, lung injury and acute respiratory distress syndrome1-5 (ARDS), for which there are no effective pharmacological therapies. Necroptosis is an attractive entry point for therapeutic intervention in ARDS and related inflammatory conditions because it drives pathogenic lung inflammation and lethality during severe IAV infection6-8 and can potentially be targeted by receptor interacting protein kinase 3 (RIPK3) inhibitors. Here we show that a newly developed RIPK3 inhibitor, UH15-38, potently and selectively blocked IAV-triggered necroptosis in alveolar epithelial cells in vivo. UH15-38 ameliorated lung inflammation and prevented mortality following infection with laboratory-adapted and pandemic strains of IAV, without compromising antiviral adaptive immune responses or impeding viral clearance. UH15-38 displayed robust therapeutic efficacy even when administered late in the course of infection, suggesting that RIPK3 blockade may provide clinical benefit in patients with IAV-driven ARDS and other hyper-inflammatory pathologies.

Trends, safety, and efficacy of wearable male sexual devices.

INTRODUCTION: The prevalence of male sexual dysfunction (MSD) increases with age, with >50% of men aged >40 years reporting erectile dysfunction (ED). In recent years, wearable male sex devices (WMSDs) have been increasingly utilized by patients and recommended by sexual medicine clinicians. OBJECTIVES: This study seeks to investigate the safety and efficacy of products currently marketed for the treatment of MSD. METHODS: Available products for WMSDs were reviewed by analyzing product websites, forums, advertisements, and clinical recommendations. Qualitative comparisons were based on patient reviews, cost, and specific features. Investigatory evidence and Food and Drug Administration status were also reviewed. Additionally, Google Trends was used to determine the popularity of devices over time. RESULTS: Eight WMSDs for the treatment of MSD and enhancement of sexual pleasure were reviewed. Constriction bands, such as the Maintain Ring Loop, Eddie by Giddy, and Xialla, have shown significant benefits in clinical trials and were the most popular devices among patients. Smart devices can provide real-time feedback on erectile quality and/or sexual performance. Similar to the RigiScan, the Adam sensor provides feedback on erectile quality while monitoring changes in penile tumescence during sleep with additional analysis available through a mobile application. Neuromodulation devices such as the Morari Patch and vPatch/in2 Patch use electrical stimulation to delay ejaculation and improve sexual function. The FirmTech Performance Ring uses sensors to track the vital signs of erectile fitness with clinical trials ongoing. CONCLUSIONS: Overall, this review describes the available investigatory evidence for a range of WMSDs and highlights the potential benefits and limitations of these devices in treating MSD and enhancing sexual pleasure. Further research is needed to evaluate the effectiveness of these devices and to determine which ones may be the most suitable for individual patients.

Rosacea Core Domain Set for Clinical Trials and Practice: A Consensus Statement.

Importance: Inconsistent reporting of outcomes in clinical trials of rosacea is impeding and likely preventing accurate data pooling and meta-analyses. There is a need for standardization of outcomes assessed during intervention trials of rosacea. Objective: To develop a rosacea core outcome set (COS) based on key domains that are globally relevant and applicable to all demographic groups to be used as a minimum list of outcomes for reporting by rosacea clinical trials, and when appropriate, in clinical practice. Evidence Review: A systematic literature review of rosacea clinical trials was conducted. Discrete outcomes were extracted and augmented through discussions and focus groups with key stakeholders. The initial list of 192 outcomes was refined to identify 50 unique outcomes that were rated through the Delphi process Round 1 by 88 panelists (63 physicians from 17 countries and 25 patients with rosacea in the US) on 9-point Likert scale. Based on feedback, an additional 11 outcomes were added in Round 2. Outcomes deemed to be critical for inclusion (rated 7-9 by ≥70% of both groups) were discussed in consensus meetings. The outcomes deemed to be most important for inclusion by at least 85% of the participants were incorporated into the final core domain set. Findings: The Delphi process and consensus-building meetings identified a final core set of 8 domains for rosacea clinical trials: ocular signs and symptoms; skin signs of disease; skin symptoms; overall severity; patient satisfaction; quality of life; degree of improvement; and presence and severity of treatment-related adverse events. Recommendations were also made for application in the clinical setting. Conclusions and Relevance: This core domain set for rosacea research is now available; its adoption by researchers may improve the usefulness of future trials of rosacea therapies by enabling meta-analyses and other comparisons across studies. This core domain set may also be useful in clinical practice.

Vitamin B12 status and folic acid supplementation influence mitochondrial heteroplasmy levels in mice.

One-carbon metabolism is a complex network of metabolic reactions that are essential for cellular function including DNA synthesis. Vitamin B12 and folate are micronutrients that are utilized in this pathway and their deficiency can result in the perturbation of one-carbon metabolism and subsequent perturbations in DNA replication and repair. This effect has been well characterized in nuclear DNA but to date, mitochondrial DNA (mtDNA) has not been investigated extensively. Mitochondrial variants have been associated with several inherited and age-related disease states; therefore, the study of factors that impact heteroplasmy are important for advancing our understanding of the mitochondrial genome's impact on human health. Heteroplasmy studies require robust and efficient mitochondrial DNA enrichment to carry out in-depth mtDNA sequencing. Many of the current methods for mtDNA enrichment can introduce biases and false-positive results. Here, we use a method that overcomes these limitations and have applied it to assess mitochondrial heteroplasmy in mouse models of altered one-carbon metabolism. Vitamin B12 deficiency was found to cause increased levels of mitochondrial DNA heteroplasmy across all tissues that were investigated. Folic acid supplementation also contributed to elevated mitochondrial DNA heteroplasmy across all mouse tissues investigated. Heteroplasmy analysis of human data from the Framingham Heart Study suggested a potential sex-specific effect of folate and vitamin B12 status on mitochondrial heteroplasmy. This is a novel relationship that may have broader consequences for our understanding of one-carbon metabolism, mitochondrial-related disease and the influence of nutrients on DNA mutation rates.

Normal diameter of the optic nerve using magnetic resonance imaging: A retrospective Nigerian study.

PURPOSE: The variations in the diameter of the optic nerve (ON) are important clinically in the diagnosis of conditions associated with the ON such as raised intracranial pressure, meningioma, optic neuritis, and Grave's orbitopathy. This study determined the normal diameters of the ON in adult Nigerians seen in a Hospital in Delta State. METHODS: Axial T1-weighted brain magnetic resonance imaging images of 150 patients (75 males and 75 females) aged ≥20 years were retrieved from the hospital's radiological database and retrospectively used to evaluate the diameter of the ON on axial and coronal sections. The data were analyzed and summarized using descriptive statistics. The mean diameters were compared based on gender, side, and age groups and correlated with age using inferential statistics. The significance level was considered at 5%. RESULTS: The diameter of the ON measured 0.45 ± 0.07 cm on the coronal section, besides 0.50 ± 0.07 cm, and 0.46 ± 0.06 cm at 0.3 cm and 0.8 cm from the posterior pole of the globe, respectively, on the axial slices. The diameters were significantly larger in males than in females (P < 0.05) and were symmetrical. However, they lacked significant association with age (P > 0.05). The three diameters measured had a significant positive correlation with each other (P < 0.05). CONCLUSION: The study provides a normal range of ON diameter in the study center to aid in the diagnosis of raised intracranial pressure and pathologies involving the nerve and its sheath.