In the care of spinal diseases, epiduroscopy has emerged as a transformational tool, delivering diagnostic and therapeutic benefits with little invasiveness. Epiduroscopy includes both diagnostic and therapeutic benefits. This technique was initially created to visualise the epidural space; however, it has since evolved with enhanced instrumentation and procedural protocols, which now enable doctors to directly evaluate pathology, deliver drugs, and guide therapies (1). Notwithstanding these benefits, the manipulation of epidural structures and the infusion of irrigation fluids during the treatment may unintentionally induce alterations in intracranial dynamics (2).

A notable consequence is the temporary increase in intracranial pressure (ICP), which may manifest as changes in the morphology of the optic nerve. Due to the intimate physical connection between the optic nerve sheath and the subarachnoid space, elevations in intracranial pressure (ICP) frequently result in quantifiable enlargements of the optic nerve sheath diameter (ONSD) (3). Recent advancements in ocular ultrasonography (OUS) have allowed practitioners to document these alterations in real time. As a non-invasive, bedside method, OUS offers instantaneous feedback on optic nerve structure, facilitating the swift identification of prospective increases in intracranial pressure (4, 5).

While invasive ICP monitoring is real-time but invasive, moderately expensive, and less user-friendly, CT/MRI is non-invasive but lacks real-time capabilities, is expensive, and has limited portability (6, 7). In contrast, Ocular Ultrasonography (OUS) is a non-invasive, real-time, low-cost, highly portable, and simple-to-use alternative for monitoring intracranial pressure (Table 1; Figure 1).

This narrative review seeks to consolidate contemporary understanding of the relationship between epiduroscopy and alterations in the optic nerve, highlighting the efficacy of OUS as a monitoring instrument. To date, no prospective study has systematically evaluated dynamic optic nerve sheath diameter changes during epiduroscopy, and no outcome-based intervention thresholds have been established. Therefore, ocular ultrasonography should currently be regarded as a supportive decision-making tool rather than a “standalone surrogate for intracranial pressure.” By investigating the physiological foundations and therapeutic ramifications of these discoveries, we aim to advocate for more standardised monitoring techniques to improve patient safety during epiduroscopy (Table 2).

In the last twenty years, epiduroscopy has become a vital method in pain management and spinal diagnostics (8). Epiduroscopy, once limited to patients with intractable spinal pain or radiculopathy, now encompasses a wider range of uses, including the assessment of epidural fibrosis and the precise administration of drugs. Its minimally invasive characteristics diminish the necessity for open surgical procedures, shorten recovery duration, and provide the combined advantages of visualisation and intervention (9).

Epiduroscopy is not risk-free, despite its advantages. The possibility of elevated ICP is a serious but little-known consequence (3). Fluid overload may occur from the administration of irrigation fluids, which are utilised to expand the epidural space for better visualisation. Furthermore, the dynamics of the distribution of cerebrospinal fluid (CSF) may change if the epidural space is mechanically altered. These circumstances have the potential to temporarily raise ICP in vulnerable patients, which is a shift that is both measurable and clinically significant (10).

The optic nerve, enclosed in a sheath that is continuous with the brain's subarachnoid space, is highly sensitive to variations in cerebrospinal fluid pressure. In instances of elevated intracranial pressure, the optic nerve sheath dilates, serving as an indirect yet dependable indicator for assessing intracranial dynamics (11). These pathophysiological insights underscore the necessity for vigilant monitoring during epiduroscopy, particularly in patients with predisposing factors for elevated ICP.

Ocular ultrasonography utilises high-frequency sound waves to produce pictures of eye structures. This approach excels in visualising the optic nerve, facilitating accurate measurements of the ONSD. The core premise is based on the transmission of ultrasonic waves that, upon contacting tissue boundaries, are reflected back to the transducer (12). Through the analysis of these echoes, physicians can recreate an image of the optic nerve and assess the surrounding sheath. A schematic illustration of optic nerve sheath diameter measurement using ocular ultrasonography and its relationship with intracranial pressure changes during epiduroscopy is provided in Figure 2.

Ocular ultrasonography can be safely and effectively performed intraoperatively with minimal disruption to the surgical workflow. In most reported settings, patients are positioned supine with the head maintained in a neutral position. A high-frequency linear ultrasound probe (typically 7–15 MHz) is gently placed over the closed eyelid using an adequate amount of ultrasound gel, ensuring minimal pressure is applied to avoid ocular compression. Routine sterile precautions are generally not required; however, careful attention to eye protection and operator technique is essential to ensure patient safety (12).

Optic nerve sheath diameter is commonly measured approximately 3 mm posterior to the globe in the transverse plane, where changes related to intracranial pressure are most reliably detected. In the intraoperative context, baseline ONSD measurements may be obtained prior to epidural irrigation, followed by intermittent or event-triggered reassessments during epiduroscopy, particularly during periods of increased irrigation pressure or prolonged procedural duration. Interpretation of ONSD findings should emphasize dynamic trends rather than isolated absolute thresholds, as transient increases may reflect procedural effects on cerebrospinal fluid dynamics. When integrated into perioperative monitoring, ocular ultrasonography provides a practical, repeatable, and non-invasive method for real-time assessment of intracranial pressure changes during epiduroscopy (6).

A crucial element of utilising OUS is its ability to quantitatively evaluate the ONSD. Multiple investigations have established a threshold, generally between 5.0 and 5.7 mm in adults (13), beyond which a substantial connection with increased ICP is observed. The swift, bedside characteristics of OUS render it an attractive option in acute care environments, when timely choices are crucial. In the realm of epiduroscopy, the capacity to consistently observe ONSD provides an early alert mechanism for detrimental intracranial occurrences (14).

OUS is non-invasive and reproducible, making it a valuable instrument in dynamic clinical situations. In contrast to conventional imaging methods, which necessitate patient relocation and result in delayed analysis, OUS offers immediate input. This immediacy is especially crucial during epiduroscopy, since fluctuations in ICP may be ephemeral yet clinically significant. Moreover, OUS is less resource-demanding than magnetic resonance imaging (MRI) or computed tomography (CT), hence reinforcing its incorporation into standard monitoring programs (15).

The utilisation of ocular ultrasonography in epiduroscopy signifies a notable progression in procedural oversight. OUS facilitates the real-time identification of alterations in the optic nerve sheath, acting as a significant surrogate marker for variations in intracranial pressure, a crucial factor in maintaining patient safety during minimally invasive spinal procedures.

The increasing popularity and scope of epiduroscopy may transform the integration of OUS into standard monitoring regimens, enhancing doctors' ability to foresee and address issues linked to temporary ICP rises. Despite the limitations of measurement variability and the necessity for comprehensive clinical validation, the advantages of OUS are evident. Further research, especially through extensive prospective studies and technical advancements, may soon establish ocular ultrasonography as a fundamental component of intraoperative monitoring in epiduroscopy, therefore improving patient safety and procedural results.

This review emphasises the significance of acknowledging the correlation between epidural fluid dynamics and optic nerve morphology. It underscores the pivotal role of OUS in reconciling procedural innovation with patient safety, a synergy that promises to enhance both clinical practice and patient outcomes in the treatment of spinal diseases.