Retrobulbar block anesthesia remains a cornerstone of ocular regional anesthesia, particularly as surgery shifts toward ambulatory settings. Many intraocular procedures, including vitreoretinal surgery and glaucoma drainage device implantation, are routinely performed under this block, which suits cooperative patients and elderly individuals with significant comorbidities who face prolonged operative times. Patients can be discharged after a short observation, saving medical resources and reducing financial burden. In developing countries, where anesthesiologists are scarce and general anesthesia access is limited, the technique holds particular importance.

The problem is that the traditional transcutaneous approach is associated with vision-threatening and even life-threatening complications. Alternative techniques such as peribulbar and sub-Tenon’s anesthesia have been developed and increasingly adopted, but each has limitations that may restrict universal application.

The procedure unfolds under the operating microscope. First, 0.1 milliliters of local anesthetic is injected subconjunctivally into the inferotemporal conjunctival fornix. The curved blunt-tip needle is then advanced through the fornix conjunctiva, following the scleral curvature into the muscle cone behind the globe, where 2 milliliters of ropivacaine is deposited. A saline-moistened pad protects the cornea during the block. Because the fornix conjunctiva is loosely attached to the underlying tissue, the authors explain, it provides an anatomical plane that facilitates smooth needle advancement, and the entire placement is visualized rather than performed blind.

The trial enrolled 196 patients and randomized them after stratification by expected surgery duration. The short-duration cohort included 103 patients, split into subgroup A1 with 52 receiving the conventional block and subgroup B1 with 51 receiving the new technique, while the long-duration cohort comprised 93 patients, with 47 in subgroup A2 and 46 in subgroup B2. Baseline characteristics including age, sex, logMAR visual acuity, intraocular pressure, axial length, and endothelial cell density showed no significant differences between groups in either cohort, confirming that the groups were comparable at the outset. Short-duration procedures included epiretinal membrane peeling, silicone oil removal, intraocular lens fixation, and glaucoma drainage device implantation, while long-duration cases involved macular hole surgery with tamponade, retinal detachment repair, and vitrectomy for advanced proliferative diabetic retinopathy.

Pain was assessed with visual analog scale-based grades at four prespecified stages: anesthetic injection, incision creation, intraoperative manipulation, and scleral indentation for exposure of the vitreous base. During injection, group B scored significantly lower than group A in both cohorts, 1.33 plus or minus 0.47 versus 1.94 plus or minus 0.69 in the short-duration group and 1.35 plus or minus 0.48 versus 1.87 plus or minus 0.61 in the long-duration group, both with p less than 0.0001. Grades 1 and 2 had been prespecified as representing adequate analgesia, and the proportion achieving it differed by +21.2 percent (95 percent CI 10.1 to 32.3) at injection in the short-duration cohort, +12.8 percent (95 percent CI 3.2 to 22.3) at injection in the long-duration cohort, and +23.1 percent (95 percent CI 6.3 to 40.0) at scleral indentation, where group B scored 1.54 plus or minus 0.77 versus 2.32 plus or minus 0.95 (p less than 0.0001). Pain grades during incision creation and intraoperative manipulation were comparable between groups, and adequate analgesia was achieved in all patients of both groups at those stages, indicating that for standard surgical steps and shorter procedures both techniques provide adequate analgesia with an injection volume of approximately 2.0 milliliters.

Ocular akinesia was evaluated with the Brahma scoring system, in which lower scores indicate better movement control. Overall, the experimental group achieved significantly better akinesia, with a mean Brahma score of 1.07 plus or minus 0.58 versus 1.29 plus or minus 0.69 in the control group (p = 0.0157). In the short-duration cohort, subgroup B1 scored significantly lower than A1 (p = 0.0437), while the long-duration subgroups did not reach statistical significance (p = 0.1728), though a favorable numerical trend was observed. The authors attribute the enhanced akinesia to more accurate intraconal deposition of anesthetic, which matters for precise procedures during pars plana vitrectomy such as macular hole tamponade, retinotomy, and membrane peeling, and may also reduce discomfort from traction on the extraocular muscles.

Complication data favored the new route, though the trial was not powered to compare complication rates, so these findings are descriptive. The conventional group reported 8 cases of raccoon eyes, meaning subcutaneous ecchymosis, and 2 cases of periorbital hemorrhage, while no such complications occurred in the experimental group. No severe complications such as retrobulbar hemorrhage, optic nerve injury, globe perforation, or brainstem anesthesia were observed in either group. Supplemental anesthesia also differed in the long-duration cohort: seven patients in group A2 required intraoperative supplementation compared with only one in group B2, a difference the authors link partly to the pain experienced during scleral indentation.

The anatomical rationale is straightforward. The average axial length of a normal globe is approximately 24 millimeters, and the lateral conjunctival fornix sits about 12 millimeters posterior to the corneal limbus. Within the intraconal space, the ciliary ganglion lies roughly 1 centimeter anterior to the common tendinous ring, between the optic nerve and the lateral rectus muscle. A retrobulbar block anesthetizes the ciliary ganglion, oculomotor nerve, and abducens nerve, providing stable surgical eye positioning and painless intraocular surgery. The traditional transcutaneous block is generally performed blind, with success influenced by needle insertion depth, operator experience, and hesitation around sharp needles. Reported complications include globe perforation and retrobulbar hemorrhage, and the external ocular compression routinely applied afterward can itself cause retinal or optic nerve ischemia and postoperative ptosis if applied inappropriately. Excessive needle advancement increases the risk of optic nerve injury, and although rare, brainstem anesthesia can occur if anesthetic enters the ophthalmic artery or penetrates the optic nerve sheath and spreads into the cerebrospinal fluid.

The authors position their contribution carefully. Delivering anesthetic to the retrobulbar or intraconal space through a trans-Tenon’s route has been described previously, including by Sugimoto and colleagues and by Xu and colleagues; what this study adds is a simpler and more reproducible clinical method. A single 20-millimeter 27-gauge curved blunt-tip needle is introduced through the conjunctival fornix in one pass and advanced into the muscle cone under the operating microscope, with no conjunctival or Tenon’s capsule incision, no cannula exchange, and no sharp needle advanced within the orbit. Insertion depth is adjusted to individual axial length, and the block is completed with approximately 2.0 milliliters of anesthetic, compared with the 3.5 to 5.5 milliliters typically needed for traditional retrobulbar blocks, without routine ocular compression afterward. The reduced volume may decrease orbital pressure elevation and minimize the risk of systemic anesthetic toxicity, and the shortened 20-millimeter shaft, versus the conventional 38 millimeters, may decrease the likelihood of deep orbital penetration and optic nerve injury, while the blunt tip may reduce the risk of orbital hemorrhage and injury to extraocular muscles. The technique also differs in kind from sub-Tenon’s anesthesia, which is a local infiltration relying on diffusion, whereas this is a nerve block delivered within the muscle cone; after injection only mild conjunctival edema is seen around the needle tunnel, whereas sub-Tenon’s injection commonly produces extensive subconjunctival edema.

The study has limitations the authors acknowledge. It was powered for the primary analgesia outcome and not for rare complications, so the absence of severe events suggests a favorable safety profile rather than establishing a reduction in risk. Follow-up was relatively short, focusing on acute anesthesia-related complications, and the VAS-based pain grade is subjective, though patients and outcome assessors were masked to group allocation. Group B also received an additional 0.1 milliliter subconjunctival injection before needle insertion, so the reduction in injection-related pain reflects the whole approach rather than the needle design alone. The intraconal position of the needle tip was judged clinically and not confirmed by imaging, and further studies are needed to evaluate the learning curve among junior ophthalmologists. Within those bounds, the trial suggests that lower injection-related pain, better ocular akinesia, and reduced need for supplemental anesthesia during prolonged vitreoretinal procedures may make the trans-fornix conjunctival retrobulbar block a practical alternative worth testing more widely.

Subject of Research: A prospective randomized controlled trial comparing a trans-fornix conjunctival retrobulbar block using a curved blunt-tip needle with conventional transcutaneous retrobulbar block for vitreoretinal surgery anesthesia.

Article Title: Efficacy and safety of trans -fornix conjunctival retrobulbar block in a prospective randomized controlled trial

Article References: Chen, R., Xu, T., Chen, C., Liu, K., Shi, G., Xi, C., Yin, M., Chen, R., Hu, K., & Chen, B. (2026). Efficacy and safety of trans-fornix conjunctival retrobulbar block in a prospective randomized controlled trial. iScience, 29(11), Article 118026. https://doi.org/10.1016/j.isci.2026.118026

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.118026

Keywords: retrobulbar block, vitreoretinal surgery, ophthalmic anesthesia, randomized controlled trial, conjunctival fornix, blunt-tip needle, ocular akinesia, ropivacaine, pain scores, periocular complications, sub-Tenon's anesthesia, regional anesthesia