Implantation Protocol of the Foldable Capsular Vitreous Body for Complex Vitreoretinal Surgery

Summary

The Foldable Capsular Vitreous Body (FCVB) is an intraocular implant that encapsulates silicone oil within a flexible capsule to reduce silicone oil-related complications. This protocol describes the surgical implantation of the FCVB via scleral incision for the treatment of complex retinal detachment and ocular trauma.

Abstract

The Foldable Capsular Vitreous Body (FCVB) is an implantable vitreous substitute designed to provide internal tamponade in eyes with complex vitreoretinal conditions. This protocol describes a standardized surgical procedure for FCVB implantation via a scleral incision, followed by silicone oil injection. The protocol outlines key preoperative considerations, including patient selection and device sizing, followed by detailed intraoperative steps, including capsule folding, insertion into the vitreous cavity, controlled silicone oil injection, device positioning, and scleral fixation. Postoperative management strategies, including patient positioning, medication regimens, and follow-up evaluation, are also described to support procedural reproducibility.

This protocol is intended for adult patients aged 18 to 65 years, with no sex-related restrictions. Eligible subjects must have a best-corrected visual acuity of less than 0.05 in the treated eye, an ocular axial length ranging from 16 to 28 mm, and present with severe retinal detachment that cannot be effectively managed using currently available vitreous substitutes. Previous clinical studies have reported that FCVB implantation can reduce silicone oil–related complications, such as emulsification and secondary glaucoma, by physically isolating silicone oil from intraocular tissues. These reported outcomes provide the clinical rationale for the use of FCVB but are not generated by this protocol itself. By presenting a step-by-step surgical workflow and highlighting critical technical considerations, this protocol serves as an instructional guide for vitreoretinal surgeons seeking to perform FCVB implantation or adapt the technique to their own surgical settings.

Introduction

Retinal detachment remains a sight-threatening condition, particularly in eyes with severe ocular trauma, multiple recurrences, or prolonged dependence on intraocular tamponade. Silicone oil is widely used as a vitreous substitute in complex vitreoretinal surgery because it provides long-term internal support; however, direct contact between silicone oil and intraocular tissues has been associated with complications such as emulsification, corneal endothelial damage, secondary glaucoma, hypotony, and long-term silicone oil dependence¹. Despite their widespread clinical use, no currently available vitreous substitute fully meets the requirements for long-term anatomical support with minimal complications in complex cases.

Internationally, vitreous substitutes used in clinical practice include silicone oil, expansile gases, and emerging investigational materials such as hydrogels. Based on existing research, current mainstream vitreous substitutes each have their specific indications and limitations. Silicone oil, as a long-term tamponade agent, effectively supports the retina and maintains intraocular pressure, particularly in cases of complex retinal detachment. However, its prolonged retention may lead to complications such as emulsification, secondary glaucoma, cataract, and corneal pathologies^2,3,4. Expanding gases (e.g., SF₆ and C₃F₈) provide effective surface tension for short-term tamponade and are commonly used in pneumatic retinopexy. Nevertheless, they require patients to maintain specific postures, carry a risk of postoperative intraocular pressure elevation, and are limited due to restrictions on air travel^5,6,7. Emerging hydrogels (e.g., PVA and PAA) are designed to mimic the rheological and biological functional properties of the natural vitreous, demonstrating good biocompatibility and potential as drug delivery carriers^8,9,10. However, further optimization is still needed regarding their long-term in vivo stability, precise control of degradation behavior, and injectability through small-gauge needles^8,11.

The Foldable Capsular Vitreous Body (FCVB), is a Class III implantable medical device developed as a novel vitreous substitute designed to address limitations associated with conventional vitreous substitutes¹². The FCVB consists of a capsule, drainage tube, drainage valve, and fixation loop, fabricated as a single unit through high-temperature and high-pressure molding of medical-grade silicone polymer¹³. Its design is based on a computerized simulation of the vitreous cavity, allowing personalized sizing and implantation. The core mechanism of the FCVB lies in its innovative capsule design. Made of medical-grade silicone polymer and shaped based on computer simulations of the human vitreous cavity, the capsule can form a physically isolated chamber after implantation, encapsulating the filling material (such as silicone oil) to prevent direct contact with and damage to intraocular tissues such as the retina and ciliary body¹². This fundamental design shift addresses issues caused by direct tissue contact in traditional silicone oil tamponade, such as emulsification, toxicity, and chronic inflammation. Based on published clinical studies, the practical implications of this design include: 1) Maintaining ocular structure and intraocular pressure: By supporting the posterior chamber space, the capsule aids in the recovery of ciliary body function and helps maintain stable intraocular pressure¹²; 2) Significantly reducing long-term complications: Physical isolation effectively lowers the risks associated with prolonged silicone oil retention, such as emulsification, secondary glaucoma, and corneal pathologies¹²; 3) Providing a new option for eye preservation in severe cases: Particularly suitable for severe post-traumatic retinal detachment, cases with multiple surgical failures, and silicone oil-dependent eyes where conventional vitreous substitutes are ineffective, the FCVB offers a novel therapeutic approach for patients who might otherwise face phthisis bulbi or enucleation¹².

First introduced in clinical practice in 2012, the FCVB was recognized as one of the four major advances in global retinal detachment surgery in 2013¹⁴ and was listed among China’s Top Ten Ophthalmological Achievements in 2015¹⁵. The device is particularly valuable in eyes with severe trauma, recurrent detachment, silicone oil dependence, and impaired ciliary function¹⁶. Published evidence on FCVB implantation includes early experimental studies, prospective clinical case series, and systematic reviews evaluating its safety and clinical performance in complex vitreoretinal conditions¹². Commonly reported endpoints include retinal reattachment status, rates of silicone oil emulsification, secondary glaucoma, corneal complications, intraocular pressure stability, and long-term globe preservation. Across these studies, FCVB implantation has been associated with lower rates of silicone oil emulsification and improved intraocular pressure stability compared with conventional silicone oil tamponade, particularly in eyes with silicone oil dependence or ciliary body dysfunction. These findings provide a growing clinical rationale for the use of FCVB in selected complex cases, while underscoring the need for standardized surgical techniques¹².

This article describes a standardized, step-by-step protocol for FCVB implantation, including preoperative planning, intraoperative surgical technique, and postoperative management, to provide a reproducible instructional guide for vitreoretinal surgeons.

Protocol

This protocol describes a standard surgical technique using an approved medical device and does not involve experimental interventions. Therefore, formal institutional ethics committee approval was not required. Written informed consent was obtained from all patients or their legal guardians prior to surgery, in accordance with the principles of the Declaration of Helsinki.

1. Preoperative preparation¹²

1. Select appropriate patients, including those with severe ocular trauma (e.g., perforating injury, choroidal rupture), recurrent retinal detachment, silicone oil-dependent eyes, endophthalmitis, or hypotony with corneal opacity.
2. Exclude patients meeting any of the following contraindications: (1) Patients are allergic to the silicone rubber or the scar diathesis; (2) Entophthalmia; (3) Uveitis; (4) The lens of the treated eye is transparent; (5) Patients have proliferative diabetic retinopathy; (6) The corrected visual acuity of the contralateral eye is ≤ 0.4; (7) The contralateral eye has an anamnesis of an internal surgery of the eye; (8) The patients have other uncontrollable eye diseases; (9) The patients have a severe renal and hepatic impairment and/or some severe systemic diseases (e.g., cardiovascular, respiratory, digestive, neurological, endocrine, and genitourinary diseases); (10) Pregnant or lactating women; (11) The patients have a history of drug abuse or alcoholism.
3. Perform preoperative imaging: B-scan ultrasonography and UBM to assess anterior and posterior segments; where possible, use OCT and three-dimensional MRI reconstruction of the vitreous cavity to determine the appropriate FCVB model and silicone oil volume.
4. Prepare all materials and instruments listed in the Table of Materials
5. Ensure the surgical team is familiar with device handling, including identification of the capsule surface, drainage valve orientation, and fixation loop.
6. Preoperatively fold a demonstration device at least once to become familiar with the process.
7. Administer topical antibiotics and anti-inflammatory agents for 3 days prior to surgery. Measure corneal diameter and intraocular pressure, and photograph the anterior segment.

2. Intraoperative Steps¹²

1. Perform the procedure under general anesthesia or retrobulbar anesthesia according to the patient's condition and institutional practice. For general anesthesia, induce anesthesia using intravenous agents such as propofol (1.5–2.5 mg/kg) combined with short-acting opioid analgesics (e.g., remifentanil or fentanyl), with or without a neuromuscular blocking agent as required for airway management. Maintain oxygen supplementation at approximately 2 L/min.
2. Create conjunctival peritomy at the 10:30 and 4:30 positions. Using a 9-0 polypropylene suture with a long needle, enter the sclera 5 mm posterior to the limbus at 10:30 and exit 4 mm posterior at 4:30.
3. Perform a leakage test by injecting balanced salt solution into the capsule before implantation.
4. Evacuate the capsule to vacuum without inverting its curvature. Fold the capsule tightly from top to bottom and secure the center with a 5-0 external suture.
   CAUTION: Avoid contact between sharp instruments and the capsule to prevent microperforation or valve damage.
5. Create a scleral tunnel incision (3.5–4.5 mm wide, based on implant size) 2 mm posterior to the limbus between the 9 and 12 o’clock positions.
6. Introduce the pre-folded device into the vitreous cavity using intraocular lens platform forceps. Once half of the capsule is inserted, cut the temporary suture and begin silicone oil injection.
7. Connect a silicone oil injection system to the drainage valve, and purge air from the tubing. Insert the needle vertically into the center of the drainage valve using gentle, controlled pressure to avoid tearing the valve. Initiate silicone oil injection at a slow, controlled rate (approximately 0.05–0.1 mL/s) under continuous visualization. Adjust injection pressure using the injector’s low-pressure or manual-assist mode to allow gradual capsule expansion.
   CAUTION: Excessive injection speed or pressure may cause valve damage or asymmetric capsule expansion.
8. Use an iris repositor to gently rotate and position the FCVB so that the lens-facing surface is oriented anteriorly and the drainage tube lies at the predetermined scleral exit site (typically the 10:30 position). Confirm correct orientation by visualizing symmetric capsule expansion and absence of folding or torsion.
9. Close the scleral tunnel incision with 10-0 nylon sutures. Restore the anterior chamber with viscoelastic.
10. Secure the fixation sutures in a Z-shaped scleral tunnel. Close the conjunctiva and Tenon’s capsule with 8-0 absorbable suture.
11. Administer subconjunctival injections of tobramycin and dexamethasone. Apply topical antibiotic and steroid ointment.
    CAUTION: Apply a pressure dressing to the operated eye to immobilize the globe and prevent postoperative bleeding.

3. Postoperative management¹²

1. Position the patient prone for the first week, then maintain a prone or lateral position for up to 3 months. Avoid supine positioning.
2. Prescribe topical tobramycin-dexamethasone eye drops 4x daily for 2 months, tapered based on clinical response.
3. Apply atropine 1% ointment once daily for 2 weeks, then switch to compound tropicamide eye drops for 1 month.
4. In cases of severe inflammation, administer periocular triamcinolone acetonide (10 mg) weekly for up to 3 weeks.
5. If hypotony, shallow anterior chamber, or exudative membrane formation is detected within 1–3 months postoperatively, viscoelastic material should be administered to both the anterior and posterior chambers, together with 1 mg of triamcinolone acetonide (TA) in the anterior chamber and 10 mg of TA via periocular injection. If these conditions recur during subsequent follow-up, the same intervention should be repeated, for a maximum of two additional treatments, to facilitate the gradual recovery of ciliary body function.
6. Manage complications such as hypotony or shallow anterior chamber with intracameral viscoelastic and triamcinolone acetonide (1 mg). Repeat if necessary.
7. Schedule follow-up visits at 1 week, 2 weeks, 1 month, 2 months, 3 months, 6 months, and annually thereafter. At each visit, assess visual acuity, intraocular pressure, retinal status, and device position.
   NOTE: This protocol is intended for vitreoretinal surgeons with formal fellowship-level training or equivalent experience in complex vitreoretinal surgery. Prior experience with silicone oil tamponade and scleral fixation techniques is strongly recommended before performing FCVB implantation independently.

4. Typical postoperative complications and management

1. Hypotony
   1. Manage postoperative hypotony (IOP < 6 mmHg) with intracameral viscoelastic (0.1–0.2 mL) to restore chamber depth. If imaging shows insufficient silicone oil, perform a supplemental injection. Ensure the patient is in a prone or lateral position and monitor the IOP digitally.
2. Shallow anterior chamber
   1. A shallow anterior chamber may result from underfilling or malposition of the foldable capsular buckle. Ensure preoperative 3D-guided device sizing, silicone oil adjustment, intracameral viscoelastic injection, and balloon repositioning.
3. Corneal opacification
   1. Corneal opacification is usually related to endothelial stress or anterior chamber shallowing. Assess the endothelial cell density at 2 weeks postoperatively. Treat with viscoelastic to deepen the chamber and with standard anti-inflammatory and mydriatic therapy.

Results

To evaluate the clinical relevance of the proposed procedure, we reviewed previously published studies reporting postoperative complication rates following FCVB implantation and conventional silicone oil tamponade. The data are summarized and compared to highlight differences in safety profiles between the two approaches (Table 1).

Published studies consistently demonstrate that accurate FCVB folding and implantation (Figure 1) result in lower rat...

Discussion

Within this manuscript, intraoperative and postoperative images demonstrate procedural checkpoints indicating correct execution of the protocol, such as complete capsule unfolding, correct orientation, and anatomical stabilization. In contrast, statements regarding safety, complication rates, and long-term outcomes are derived from previously published studies and should be interpreted as literature-supported expectations rather than outcomes demonstrated by this protocol.

The FCVB implantatio...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Anesthetic agent	As per institutional protocol		Local or general anesthesia Quantity: 1
Balanced saline solution (BSS) / sterile normal saline	—		30ml Quantity: 1
Caliper	—		Ophthalmic surgical caliper Quantity: 1
Foldable Capsular Vitreous Body (FCVB)	Guangzhou Vesber Biotechnology		Size determined preoperatively (AV-10P, AV-10PX, AV-12P, AV-13.5P, AV-15P, and AV-17P) Quantity: 2
Intraocular lens (IOL) implantation forceps	—		Ophthalmic Quantity: 1
Iris repositor	—		Ophthalmic type Quantity: 1
Lid speculum	—		Adult ophthalmic Quantity: 1
Lint-free sterile gloves			Quantity: 1
Microsurgical forceps (non-toothed)	—		Ophthalmic Quantity: 1
Microsurgical forceps (toothed)	—		Ophthalmic Quantity: 1
Microsurgical scissors (angled)	—		Ophthalmic Quantity: 1
Needle (25G) or 25G vitrectomy trocar needle	—		25-gauge Quantity: 1
Ophthalmic viscosurgical device (sodium hyaluronate)	Bausch + Lomb		1 mL Quantity: 1
Positioning hook	—		Ophthalmic Quantity: 1
Silicone oil	Bausch + Lomb		VRL600 Quantity: 1
Silicone oil	Fluoron (Germany)		Siluron 5000 Quantity: 1
sterile beaker	—		30 mL Quantity: 1
Sterile gauze pads	—		Quantity: 1
Sterile syringe	—		2 mL Quantity: 1
Sterile syringe	—		10 mL Quantity: 1
Suture, absorbable (Vicryl)	Ethicon		7-0 Quantity: 1
Suture, non-absorbable	—		10-0, Model 8065307901 Quantity: 1
Suture, non-absorbable	—		5-0
Suture, non-absorbable (US)	—		10-0 Quantity: 1