Posterior vitreous detachment rate following intravitreal dexamethasone injection

NONPHARMACOLOGICAL ASPECTS OF INTRAVITREAL DEXAMETHASONE IMPLANT INJECTIONS: A Retrospective Study of 3,430 Injections and Complications

PURPOSE

This study aims to evaluate the nonpharmacological safety profile of intravitreal dexamethasone implants in cases with different etiologies.

METHODS

This retrospective university-based study analyzed clinical reports of patients receiving 0.7 mg dexamethasone implant injections between 2013 and 2023. The study recorded patient demographics, injection indications, and follow-up data. Complications caused by the injection procedure and adverse events other than pharmacological side effects within a 3-month period were included.

RESULTS

In this study, 3,430 dexamethasone implant injections were made into 1,471 eyes of 1,091 patients. Nonpharmacological complications developed in 611 injections (17.8%). Subconjunctival hemorrhage was noted as the leading nonpharmacological complication (n = 576, 16.8%). Sight-threatening 35 nonpharmacological adverse events and complications (1.0%) were recorded. Cases of anterior chamber migration, vitreous hemorrhage, retinal detachment, endophthalmitis, hypotony, and implant misplacement were observed. Cases requiring intensive treatments and additional surgical interventions were encountered.

CONCLUSION

The injection of the dexamethasone implant may lead to nonpharmacological complications caused by the mechanical impact of the injection or improper positioning of the implant, potentially resulting in vision loss. Severe outcomes such as corneal decompensation, retinal detachment, and endophthalmitis can ensue, emphasizing the gravity of these complications. Careful selection of patients and adherence to proper injection techniques are essential in reducing these risks.

The Roles of Vitreous Biomechanics in Ocular Disease, Biomolecule Transport, and Pharmacokinetics

PURPOSE

The biomechanical properties of the vitreous humor and replication of these properties to develop substitutes for the vitreous humor have rapidly become topics of interest over the last two decades. In particular, the behavior of the vitreous humor as a viscoelastic tissue has been investigated to identify its role in a variety of processes related to biotransport, aging, and age-related pathologies of the vitreoretinal interface.

METHODS

A thorough search and review of peer-reviewed publications discussing the biomechanical properties of the vitreous humor in both human and animal specimens was conducted. Findings on the effects of biomechanics on vitreoretinal pathologies and vitreous biotransport were analyzed and discussed.

RESULTS

The pig and rabbit vitreous have been found to be most mechanically similar to the human vitreous. Age-related liquefaction of the vitreous creates two mechanically unique phases, with an overall effect of softening the vitreous. However, the techniques used to acquire this mechanical data are limited by the in vitro testing methods used, and the vitreous humor has been hypothesized to behave differently in vivo due in part to its swelling properties. The impact of liquefaction and subsequent detachment of the vitreous humor from the posterior retinal surface is implicated in a variety of tractional pathologies of the retina and macula. Liquefaction also causes significant changes in the biotransport properties of the eye, allowing for significantly faster movement of molecules compared to the healthy vitreous. Recent developments in computational and ex vivo models of the vitreous humor have helped with understanding its behavior and developing materials capable of replacing it.

CONCLUSIONS

A better understanding of the biomechanical properties of the vitreous humor and how these relate to its structure will potentially aid in improving clinical metrics for vitreous liquefaction, design of biomimetic vitreous substitutes, and predicting pharmacokinetics for intravitreal drug delivery.