ACCURACY AND PRECISION OF INTRAVITREAL INJECTIONS OF ANTI–VASCULAR ENDOTHELIAL GROWTH FACTOR AGENTS IN REAL LIFE: What Is Actually in the Syringe?

Clinical Outcomes and Experiences with Prefilled Syringes Versus Vials for Intravitreal Administration of Anti-VEGF Treatments: A Systematic Review

INTRODUCTION

Anti-vascular endothelial growth factor (VEGF) agents have been the standard treatment for retinal diseases for almost two decades. These treatments are administered via intravitreal injection using single-use vials or prefilled syringes (PFS). In this systematic review, we evaluate health care resource use and clinical outcomes and experiences with PFS for intravitreal injection of anti-VEGF treatments.

METHODS

MEDLINE, EMBASE, and The Cochrane Library were searched from January 1, 2015 to February 8, 2024 to identify literature reporting outcomes regarding procedural efficiency, health care resource use, patient and clinician experiences, and safety for currently approved anti-VEGFs (ranibizumab, aflibercept, brolucizumab) administered using PFS. Comparators were vial-based injections of the same anti-VEGFs.

RESULTS

A total of 36 publications met the criteria for inclusion in the systematic literature review; the majority were non-randomized studies, with a small number of reviews, case series, survey studies, and opinion articles. Publications reported that preparation times were significantly shorter for PFS (40.3-57.9 s) versus vials (ranibizumab, 62.8-98.0 s; aflibercept, 71.9-79.5 s), with no differences in product stability between PFS and vials. Clinicians expressed a preference for PFS and thought PFS were faster, easier to use, and had increased safety versus vials. Publications consistently reported significantly lower rates of endophthalmitis per injection with PFS versus vials (ranibizumab PFS, 0-0.02%; aflibercept PFS, 0.01-0.02%; ranibizumab vial, 0.02-0.05%; aflibercept vial, 0.02-0.06%). Four publications reported increased rates of transient vision loss after aflibercept PFS injection versus vial-based injection. No publications reported outcomes regarding health care resource use or patient experiences.

CONCLUSION

The available literature supports the increased procedural efficiency of PFS versus vial-based intravitreal injection of anti-VEGFs. PFS are positively perceived by clinicians and have a safety benefit in the form of a decreased risk of endophthalmitis versus vials.

Accuracy, Precision, and Residual Volume of Commonly Used Syringes for Intravitreal Injections and the Impact on Intraocular Pressure

PURPOSE

To compare accuracy, precision, and residual volume of commonly used syringes for intravitreal injections (IVIs) and to assess the intraocular pressure (IOP) rise by variations in volumes delivered.

DESIGN

Experimental laboratory study.

SUBJECTS

No subjects were involved in this study.

METHODS

We tested 8 syringe models with 2 different needle setups, with 2 different solutions (distilled water or glycerin) and target volumes (50 and 70 μL). To obtain the delivered and residual volumes, we weighed the syringe-needle setups with scale before liquid withdrawal, with liquid, and after liquid release. We also created an experimental eye model to determine the transient rise in IOP following stepwise 10-μL increases in injection volumes.

MAIN OUTCOME MEASURES

Delivered and residual volumes, IOP rise.

RESULTS

We tested a total of 600 syringe-needle setups. Becton Dickinson (BD) Ultra-Fine (0.34 ± 0.28 μL), Zero Residual (1.53 ± 1.15 μL), and Zero Residual Silicone Oil-free (1.40 ± 1.16 μL) syringes showed the lowest residual volume (P < 0.001) in comparison with the others (range: 24.86 ± 1.78 μL for Injekt-F to 51.97 ± 3.37 μL for Omnifix-F). The most accurate setups were (percentage deviation from target volume): Zero Residual Silicone Oil-free (+ 0.70%), Zero Residual 0.3 ml (+ 4.49%), BD Ultra-Fine (+ 7.83%), Injekt-F (9.42%), Norm-Ject (+ 15.88%), Omnifix-F (+ 16.96%), BD Plastipak Brazil (+17.96%), and BD Plastipak Spain syringes (+ 19.41%). There was a statistically significant difference between the Zero Residual Silicone Oil-free syringe and all other syringes (P < 0.0001), except for the Zero Residual 0.3-ml syringe (P = 0.029). The coefficient of variation was low for all syringes. The modeled IOP rise ranged from 32.3 (standard deviation [SD], 1.4) mmHg for 20-μL injection volume to 76.5 (SD, 1.0) mmHg for 80-μL injection volume. For the standard 50-μL injection volume, the peak pressure was 50.7 (SD, 0.1) mmHg, and the pressure rise duration was 28 (SD, 2) minutes.

CONCLUSIONS

There were significant differences in accuracy and residual volume between syringes, whereas they showed a high precision. Volume excess results in a considerable increase in IOP rise after injection. These findings may provide a relevant overview to clinicians and to both device and drug manufacturers regarding pharmacoeconomic, safety, and efficacy issues.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

SYRINGE DESIGN AND FILLING TECHNIQUE AFFECT ACCURACY OF ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR INTRAVITREAL INJECTIONS

PURPOSE

To evaluate the effect of syringe design and filling technique on the accuracy of anti-vascular endothelial growth factor delivery.

METHODS

Volume output was measured with three syringe designs: a 1.0-mL slip-tip syringe, a 1.0-mL Luer-lock syringe, and a ranibizumab prefilled syringe-using two filling techniques ("upward" and "downward") and two fluids (water and bevacizumab). A total of 300 simulated injections were performed. Accuracy was determined by difference from the intended volume of 50 µ L and by mean absolute percentage error.

RESULTS

Volume outputs were significantly different between syringe designs, with mean values of 61.99 ± 4.18 µ L with the 1-mL slip-tip syringe, 57.43 ± 4.95 µ L with the Luer-lock 1-mL syringe, and 51.06 ± 4.74 µ L with the ranibizumab syringe, making the latter the most accurate syringe. There were 37 cases (12.3%) of underdosing below 50 µ L, the majority of which occurred with the ranibizumab syringe. The "downward" technique reduced the occurrence of air bubbles.

CONCLUSION

Intravitreal injections using 1.0-mL syringes are less accurate than using the ranibizumab prefilled syringe, which has a low-volume and low dead-space plunger design. The variability in volume output may result in less predictable treatment response, especially in cases of underdosing, which were more common with the ranibizumab syringe.

Deformation of Aflibercept and Ranibizumab Syringes Causes Variation in Intravitreal Injection Volume and Risks Retinal Tear Formation

PURPOSE

The intravitreal injection volume is known to vary with plunger alignment and the speed of injection. We investigated the role that syringe stopper deformation plays in allowing excess volumes to be injected into the eye and the potential for the vitreous humor to become incarcerated when excess force is released within the eye.

DESIGN

Experimental study.

METHODS

Aflibercept prefilled syringes (PFSs), ranibizumab PFSs, and 1-ml tuberculin (TB) syringes were subjected to increasing injection force to assess the extent to which each design allowed for excess volumes to be expelled after the stopper reached the bottom of the syringe barrel (i.e., after the 50-μl dose was expelled).

MAIN OUTCOME MEASURES

Additional volume expelled with stopper deformation.

RESULTS

Syringe stoppers are capable of deformation into the dead space when additional force is applied. This allows for progressively greater medication doses to be administered. At an additional force of 3.92 N after the syringe stopper came in contact with the bottom of the syringe barrel, the aflibercept PFSs, ranibizumab PFSs, and 1-ml TB syringes dispensed an additional 17.2%, 11.4%, and 0.8% higher volume than the intended volume of 50 μl, respectively. Upon release of this force, a proportional volume was observed to be drawn back into the needle.

CONCLUSIONS

The intravitreal injection volume varies with the force applied to fully depressed syringes because of syringe stopper deformation. We advise that performing forceful intravitreal injections be avoided to prevent excessive dosing of medication. We also caution that pressure applied to the plunger during intravitreal injections not be released while the needle is in the vitreous cavity to guard against vitreous incarceration, which could lead to retinal tear formation or detachment.

Incidence of severe rise in intraocular pressure after intravitreous injection of aflibercept with prefilled syringes

Our aim was to analyze the intraocular pressure (IOP) changes following different intravitreous injection (IVI) procedures with or without prefilled syringes (PFS) and to elaborate their possible causes. Clinical study and laboratory assessment. 173 eyes of 141 patients. The IOP was prospectively measured pre- and postoperatively in three groups of patients receiving IVI either with ranibizumab (RP), aflibercept PFS (AP) or aflibercept vials (AV). The AP emptying volume (EV) was assessed using 40 aflibercept PFS vials: the plunger was aligned precisely (normal volume, NV) or right below the indication line (high volume, HV) and the drug was ejected with (wP) or without forced pressure (nP). Primary outcome was post-treatment IOP with type of IVI and pre-treatment IOP as fixed factors. Secondary outcome was identification of possibly confounding factors (age, sex, pathology, presence of pseudophakia, spherical error, and number of injections) and IOP > 30 mmHg post-treatment. An IOP rise above 30 mmHg was observed in 8/38 (22%), 16/51 (31%) and 35/86 (41%) cases in the RP, AV and AP groups, respectively (p = 0.129). Pre-treatment IOP was the only predictive variable for IOP rise (p < 0.001). The EV values in the NVnP, NVwP, HVnP and HVwP groups were 56.06 ± 10.32, 70.69 ± 4.56, 74.22 ± 7.41 and 81.63 ± 3.67 µl, respectively (p < 0.001). We observed a marked, although not significantly higher incidence of IOP elevations with the aflibercept PFS. One possible reason may be the error-proneness of administering the correct volume with the AP. Caution should be taken when using the aflibercept PFS in order to prevent potential optic nerve damage in cases with marked elevation in IOP.

Accuracy of intravitreal injection volume for aflibercept pre-filled syringe and BD Luer-Lok one-milliliter syringe

Background

To evaluate the accuracy of intravitreal injection volume of the pre-filled syringe (PFS) in which aflibercept is packaged compared to the BD Luer-Lok 1-mL syringe.

Methods

Ophthalmologists injected their typical intravitreal volume for aflibercept using either the PFS or BD Luer-Lok 1-mL syringe for 5 times each. The injected fluid was weighed using a micro-scale and converted to volume. The volume of fluid injected was also evaluated when the 0.05 mL line on the PFS was lined up to the tip or base of the dome-shaped plunger.

Results

Injection volume was measured for 12 physicians. The average injected fluid volume was 74.22 ± 15.87 µL for PFS and 53.42 ± 4.61 µL for the BD Luer-Lok 1-mL syringe (p < 0.0001). The average deviation in volume injected for the PFS was higher compared to the BD Luer-Lok 1-mL syringe (11.36 µL vs. 3.35 µL, p < 0.0001). When the PFS was lined up with the tip of the dome-shaped plunger at the 0.05-mL line, the average injected volume was 71.03% higher.

Conclusions

The intravitreal injection volume and variability using the new PFS were significantly higher than the volume injected using the BD Luer-Lok 1-mL syringe previously used, potentially leading to higher rates of visually significant elevation of intraocular pressures.

Silicone oil droplets in the vitreous after intravitreal injections: review of literature with clinical examples

Currently, intravitreal injections are firmly in the lead as a drug delivery method for treatment of a wide range of eye diseases. With the accumulation of clinical material, knowledge about the complications and side effects of this technique is expanding. One of the undesirable phenomena that has been actively studied recently is the ingress of silicone oil droplets from single-use syringes and needles used to perform the procedure into the vitreous cavity of patients eyes. The analysis of the results of original studies on this issue is carried out, and the currently available practical recommendations aimed at reducing the risk of this complication are presented. The article is illustrated with original clinical examples. It can be concluded that the penetration of silicone oil into the eye cavity during intravitreal injections is an urgent problem of modern ophthalmology that requires further investigation and solution.

Intravitreal air bubbles following intravitreal injections: a comprehensive analysis

PURPOSE

To evaluate the prevalence of residual air bubbles following intravitreal injections of anti-VEGF agents, and to compare two techniques designed to reduce their occurrence.

METHODS

Patients who received intravitreal injections reported the presence of air bubbles following the procedure, and were followed to determine when they disappeared. Two techniques used to reduce air bubbles prior to injection were compared-tapping the syringe with the needle up ("upwards" technique) or down ("downwards" technique). Rates of residual air bubbles were compared between techniques, and between different drugs.

RESULTS

The study included 344 intravitreal injections, 172 injected with each technique. The overall rate of residual air bubbles was 11.3%, with 94.9% resolution by 48 h. The rate was significantly lower with the "downwards" technique (7.5% vs. 15.1%, p = 0.027). It was also significantly lower with ranibizumab injected using pre-filled syringes than with bevacizumab and aflibercept (0% vs. 12.1% and 14.7%, p < 0.0001). A questionnaire revealed patients reported medium levels of discomfort and a high importance of avoiding air bubbles.

CONCLUSIONS

Residual air bubbles are a common occurrence, likely to be experienced by most patients undergoing repeated injections. This phenomenon may be significantly reduced by using the described "downwards" technique, or pre-filled syringes.

Container Closure and Delivery Considerations for Intravitreal Drug Administration

Intravitreal (IVT) administration of therapeutics is the standard of care for treatment of back-of-eye disorders. Although a common procedure performed by retinal specialists, IVT administration is associated with unique challenges related to drug product, device and the procedure, which may result in adverse events. Container closure configuration plays a crucial role in maintaining product stability, safety, and efficacy for the intended shelf-life. Careful design of primary container configuration is also important to accurately deliver small volumes (10-100 μL). Over- or under-dosing may lead to undesired adverse events or lack of efficacy resulting in unpredictable and variable clinical responses. IVT drug products have been traditionally presented in glass vials. However, pre-filled syringes offer a more convenient administration option by reducing the number of steps required for dose preparation there by potentially reducing the time demand on the healthcare providers. In addition to primary container selection, product development studies should focus on, among other things, primary container component characterization, material compatibility with the formulation, formulation stability, fill volume determination, extractables/leachables, and terminal sterilization. Ancillary components such as disposable syringes and needles must be carefully selected, and a detailed administration procedure that includes dosing instructions is required to ensure successful administration of the product. Despite significant efforts in improving the drug product and administration procedures, ocular safety concerns such as endophthalmitis, increased intraocular pressure, and presence of silicone floaters have been reported. A systematic review of available literature on container closure and devices for IVT administration can help guide successful product development.

The influence of dead spaces and the designs of injectors on the amount of drug dose in intra-vitreal injection

AIM

To evaluate the dead spaces resulting from different designs of the insulin injectors used for intravitreal injections and the amounts of drug doses.

METHODS

In the study, five different brands of sterile insulin injectors of 1 mL were used for the test. The weight of the injectors was determined before and after filling the injectors with 0.05 and 0.1 mL distilled water. The weight of the injectors was measured with and without the needle after the water within the injectors had been taken out and weight differences were measured. The difference between the intended amount of fluid to be thrown out and the weight of the fluid remaining in the injector was calculated as percent error.

RESULTS

After throwing out 0.05 mL distilled water from the injector, weights of the Beybi^®, Traf^®, Becton Dickinson^®, Ayset^®, and Setojet^® brands of injectors with 30 G needle were detected to increase the mean 0.0220 ± 0.006 g, 0.0208 ± 0.008 g, 0.0355 ± 0.016 g, 0.0219 ± 0.017 g, and 0.0150 ± 0.007 g, respectively compared to the weights of the dry injectors. The 0.1 mL injector group was found to be mean 0.0350 ± 0.014 g, 0.0264 ± 0.008 g, 0.0405 ± 0.015 g, 0.0272 ± 0.013 g, and 0.0245 ± 0.014 g, respectively. The maximum increase due to the dead spaces in the injectors was found in the Becton Dickinson^® injector, both in the 0.05 mL and the 0.1 mL groups (p < 0.000).

CONCLUSION

The injector designs may affect the dose of IVI required to be given. More correct amounts of drugs may be administered via the intra-vitreal route through designs that reduce the dead spaces at the end part of the injector and between the inner wall and the plunger.

Issues with Intravitreal Administration of Anti-VEGF Drugs

Purpose

To provide an update of summary of risk factors and side effects of long-term use and contamination of intravitreal anti-VEGF injections.

Methods

We reviewed relevant publications of the topic of contamination of anti-VEGF injections and long-term side effects due to this reason.

Results

Due to the long-term use of anti-VEGF drugs and the higher number of injections worldwide, various studies have shown side effects in recent years, ranging from increased intraocular pressure to visual disturbing silicone oil vesicles in the vitreous cavity. Several studies have demonstrated that both the drug and the processing, storage, environmental factors and the material and design of the syringes have a decisive influence on these side effects.

Conclusion

The risks of deposits from syringes in the eye can be significantly reduced by various optimizations in transport, storage and syringe and cannula selection.

Prefilled syringes for intravitreal drug delivery

Intravitreal injections of anti-vascular endothelial growth factor (VEGF) medications play an increasingly critical role in numerous retinal vascular diseases. Initially, anti-VEGF medications came in vials that had to be drawn up by the physician into a syringe for administration. In 2018, the US Food and Drug Administration (US FDA) approved the ranibizumab 0.3 mg prefilled syringe (PFS), and in October 2016, the US FDA approved the ranibizumab 0.5 mg PFS. This article discusses the advantages of the PFS, including reduced injection time, possible reduced risk of endophthalmitis, reduction in intraocular air bubbles and silicone oil droplets, and improved precision in the volume and dose of intravitreal ranibizumab administered, along with possible disadvantages. Implications of the innovation of the PFS on intravitreal injection technique and clinical practice pattern are discussed and reviewed.