Proliferative vitreoretinopathy is a highly probable consequence of severe ocular trauma which usually requires pars plana vitrectomy to prevent disease progression. As the vitreous body is unable to regenerate, it is necessary to fill the vitreous cavity with vitreous substitutes to support the retina after vitrectomy. Therefore, the introduction of an optimal vitreous substitute in the course of a vitrectomy is essential. SO is the most widely used intraocular tamponade in clinical practice; however, it has many drawbacks and limitations, such as elevated IOP, oil emulsification, secondary glaucoma, and keratopathy.[11, 21, 22]
FCVB is a new product that has refined the way in which SO works in the inner cavity of the eyeball.[18] It has been reported that it can prevent the displacement and emulsification of SO,[23] and effectively reduce the post-surgical complications .[16] FCVB filled with SO have been shown to be effective and safe in human eyes[16]; however, we have identified some issues with FCVB in clinical practice. The purpose of this study was to summarize our experience with the application of FCVB.
As FCVB is a relatively new product and was not used at our hospital previously, we were very careful in selecting appropriate patients. All cases in this study had a history of severe ocular trauma and underwent several operations, and IOP could not be maintained with SO tamponade. Initially, we selected only cases with no light perception visual acuity and cases of planned eyeball enucleation. All cases in this study had severe ocular injuries, and the prognoses were very poor.
In this study, with the exception of the shallow anterior chamber, no other structural abnormalities were found after FCVB implantation. B-scan ultrasonography revealed that the FCVB was in good contact with the retina and had good retina-supporting function. Further, no retinal detachment was observed during follow-up. Ultrasound biomicroscopy showed that the FCVB smoothly contacted the ciliary body with no crushing action.
Visual acuity did not improve after FCVB implantation in this study, which is consistent with the results of previous studies.[17, 18, 23]
No significant differences were found in IOP after FCVB implantation, although it was higher postoperatively. In clinical practice, we have observed that postoperative IOP is mainly determined by the function of the ciliary body, rather than by the SO injected into the FCVB. Moreover, we do not suggest excessive injection of SO; the amount of SO injected into the FCVB is usually less than that injected into the vitreous body directly, and an IOP of 15 mmHg may be appropriate. Patients with an iris must have space in the posterior chamber to avoid a shallow anterior chamber.
We did not encounter severe surgical complications during the follow-up period. Cataract was not found as the lens was lost in the primary injury or lensectomy was performed during the par plana vitrectomy surgery in this study. Other complications such as uveitis, vitreous hemorrhage, endophthalmitis, retinal detachment, and SO emulsification were not observed during the observation period. Leakage of SO was found in one case, but after refilling with SO, the condition of the eye was stable.
However, serious complications such as corneal opacity and keratopathy were observed in this study. The reason for these may be as follows: first, all eyes in this study had severe injuries and underwent several operations. Thus, the structure of the ocular surface may have changed, leading to an impaired blood supply and nutrition of the cornea. [24] Second, in this study, the time between SO injection and FCVB implantation was 5.29 ± 3.33 months, which is relatively long. This may increase the toxic effect of SO on the corneal endothelium and ciliary body.[25, 26] Previous studies[27–29] have reported corneal perforation secondary to SO keratopathy due to poor corneal nutrition. Risk factors include longer duration of oil in the eye, aphakia, SO in the anterior chamber, and extensive and multiple surgeries, all of which were present in our cases. Third, the function of the ciliary body may be impaired by multiple intraocular surgical procedures, inflammation, ciliary body shock, and destruction. Impaired ciliary body function can lead to persistent chronic hypotony and difficulty in the formation of a normal anterior chamber, carrying the risk of corneal opacification.[30] Therefore, it may be inferred that patients with poor ciliary body function may not be suitable for FCVB implantation.
From our cases, it is suggested that SO dependent eyes should not be filled with SO for an extended amount of time before choosing a FCVB implantation to prevent cornea damage. However, if FCVB implantation is performed too early, the postoperative inflammatory response may be severe, and the function of the ciliary body cannot be accurately predicted. In this study, in cases with relatively good corneal transparency, the duration between SO injection and FCVB implantation was no more than 3 months. Therefore, we hypothesized that 3 months may be an appropriate time to implant the FCVB after filling SO for SO dependent eyes. However, this is our experience with a small sample size and requires further research.
There are a few limitations to the present study. The sample size was small and case selection was relatively tight. In addition, a longer follow-up time is required. However, the results remain viable as they provide valuable information for further improvement of surgical outcomes.