Anesthesia for Intravitreal Injection: A Systematic Review

Comparing the in vitro efficacy of chlorhexidine and povidone-iodine in the prevention of post-surgical endophthalmitis

BACKGROUND

Intravitreal injections are a common ophthalmologic procedure. While infections following these injections are rare, they can lead to endophthalmitis, with potentially serious consequences. Various methods have been proposed to prevent endophthalmitis, including the use of antisepsis and antibiotics in patient preparation.

PURPOSE

To evaluate the antiseptic efficacy of aqueous chlorhexidine (CHX) and povidone-iodine (PI) when used alone and in combination with lidocaine gel (LG) in vitro.

METHODS

Two independent experimental trials were conducted. The first trial determined the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of CHX and PI against six bacterial strains. The second trial evaluated the bactericidal efficacy of the antiseptic agents (CHX 0.1% and PI 5%) and their combination with LG against the same bacterial strains.

RESULTS

CHX was more effective than PI in reducing the number of colonies forming units (cfus) of the tested bacteria. The order in which the antiseptic and LG were administered affected their effectiveness, with CHX administered before LG resulting in greater reduction of bacterial growth.

CONCLUSIONS

CHX 0.1% is more effective than PI 5% as an antiseptic agent. Application of CHX and PI prior to the use of lidocaine gel results in a more effective reduction of microorganisms.

Comprehensive ocular and systemic pharmacokinetics of dexamethasone after subconjunctival and intravenous injections in rabbits

Even though subconjunctival injections are used in clinics, their quantitative pharmacokinetics has not been studied systematically. For this purpose, we evaluated the ocular and plasma pharmacokinetics of subconjunctival dexamethasone in rabbits. Intravenous injection was also given to enable a better understanding of the systemic pharmacokinetics. Dexamethasone concentrations in plasma (after subconjunctival and intravenous injections) and four ocular tissues (iris-ciliary body, aqueous humour, neural retina and vitreous) were analysed using LC-MS/MS. Population pharmacokinetic modelling for plasma data from both injection routes were used, and for first time the constant rate of absorption of dexamethasone from the subconjunctival space into plasma was estimated (ka,plasma = 0.043 min-1, i.e. absorption half-life of 17.3 min). Non-compartmental analysis was used for the ocular data analysis and resulting in ocular drug exposure of iris-ciliary body (AUC0-∞= 41984 min·ng/g) > neural retina (AUC0-∞= 25511 min·ng/g) > vitreous (AUC0-∞= 7319 min·ng/mL) > aqueous humour (AUC0-∞= 6146 min·ng/mL). The absolute bioavailability values after subconjunctival injection, reported for the first time, were 0.74 % in aqueous humour (comparable to topical dexamethasone suspensions), and 0.30 % in vitreous humour (estimated to be higher than in topical administration). These novel and comprehensive pharmacokinetic data provide valuable information on the potential for exploiting this route in ocular drug development for treating both, anterior and posterior segment ocular diseases. Moreover, the new generated dexamethasone-parameters are a step-forward in building predictive pharmacokinetic models to support the design of new subconjunctival dexamethasone formulations, which may sustain drug effect for longer period of time.

Post-Intravitreal injection pain reduction using topical NSAIDS: A comparative study

PURPOSE

To compare the efficacy of two different topical non-steroidal anti-inflammatory drugs (NSAIDs) drops with versus without conservatives after intravitreal injections (IVIs).

DESIGN

Prospective, randomized, placebo-controlled, single-blinded comparative study.

PARTICIPANTS AND METHOD

A total of 308 eyes of 252 patients receiving an IVI of anti-vascular endothelial growth factor (anti-VEGF) were randomly assigned to receive either a single drop of nepafenac 0.1%, preservative-free diclofenac 0.1%, or artificial tears (control group) immediately after IVI. Primary outcome measure was pain scores immediately, six hours and twenty-four hours post- injection.

RESULTS

166 patients received one topical drop of NSAIDS, of which 90 in the diclofenac group and 76 in the nepafenac group. Additional 86 patients were included in the control group. Mean reported pain score was significantly lower at six hours after IVI in the preservative-free diclofenac group (17.1 ± 23.0) than in the nepafenac group (26.2 ± 31.9) and the control group (27.5 ± 29.2) (p = 0.03). At twenty-four hours post-injection there was no statistically significant difference between the groups. Patients reported less pain compared to previous IVIs and none referred to urgent health care, but these findings were not statistically significant.

CONCLUSIONS

The use of topical preservative-free NSAIDs may be superior to preservative- containing NSAIDs in pain relief after IVIs and may be considered as part of the treatment protocol of this population.

Randomized Controlled Study of Cooled vs Room-Temperature Artificial Tears for Reducing Ocular Surface Irritation After Intravitreal Injection

Purpose: To evaluate the efficacy of cooled vs room-temperature artificial tears in reducing ocular discomfort after intravitreal injections (IVIs). Methods: Patients receiving a standard intravitreal injection in the retina clinic who met the eligibility criteria and provided informed consented were enrolled in the study. Patients were randomized to the cooled tears or room-temperature tears intervention group. Both groups rated their ocular discomfort following IVI after cooled or room-temperature tears were administered. Results: The cooled group comprised 48 patients and the room-temperature group, 61 patients. There was no significant difference in the reduction of ocular discomfort between the cooled vs room-temperature artificial tears groups (P = .387). In addition, there was a similar level of reduction in ocular discomfort after either intervention (P = .681) regardless of whether or not the patients routinely used artificial tears after previous IVIs. Conclusions: Cooled tears provided no additional benefit in reducing ocular discomfort post-IVI compared with room-temperature tears. Baseline tear use after an IVI may have no true benefit other than a potential placebo effect, recall bias, or both.

Cooling Anesthesia for Intravitreal Injections - A Review

Intravitreal (IVT) injections are the most common procedure performed in retinal clinics today. It has revolutionized the treatment of neovascular age-related macular degeneration (nAMD), diabetic macular edema, macular edema due to veinous occlusive disease and other forms of exudative maculopathy. Though IVT injections prevent vision loss, the discomfort at the time of the injection has been troublesome to patients. This has led to patients missing their regular and routine dosage of treatment. Various modes of pre-injection anesthetic methods have been tried but in vain. Lidocaine-based topical anesthesia, in the form of pledgets, topical gel or subconjunctival lidocaine injection, has been the standard of care (SOC) for IVT injections worldwide. This article highlights the role of cooling anesthesia in reducing pain, anxiety and discomfort associated with needle penetration at the time of injection. PubMed and MedLine search were related to anesthesia for intravitreal injections, cooling anesthesia, mechanism of cooling anesthesia, COOL-1 trial, COOL-2 trial, results of COOL-1 trial and ultrarapid cooling anesthesia.

Two Randomized, Double-masked, Placebo-controlled Studies of the Local Anesthetic Effect of Articaine Ophthalmic Solution

Background

We wanted to develop a new topical ocular anesthetic with good bioavailability in anterior segment tissues. Given concerns about contamination and sterility in multi-dose products, we selected a unit-dose, nonpreserved presentation of AG-920 (articaine ophthalmic solution) in blow-fill-seal containers (similar to currently marketed pharmacological therapies for dry eye disease).

Methods

Consistent with US Food and Drug Administration guidance, two pivotal, Phase 3, randomized, placebo-controlled, double-masked, parallel design studies conducted at two US private practices in 240 healthy subjects. A single dose of AG-920 or identical looking placebo into one (study) eye (2 drops 30 s apart). Subjects underwent a conjunctival pinch procedure and assessment of the pain associated with the pinch. The main outcome measure was the proportion of subjects with rating of "No pain at 5 minutes".

Results

AG-920 provided a rapid onset of local anesthesia (less than one minute) with clinically and statistically significantly greater effect in AG-920 (68% and 83%) than placebo (3% and 18% for Study 1 and Study 2, respectively, P<0.0001). The most frequent adverse event was instillation site pain (27% vs 3%) followed by conjunctival hyperemia (probably related to the pinch, 9% vs 10%) in the AG-920 and placebo groups, respectively.

Conclusion

AG-920 was found to be have a rapid onset and useful duration of local anesthesia with no major safety issues, and may be useful for the eye-care professional. Registered with clinicaltrials.gov as NCT04513652 and NCT04829344.

Preventive factors, diagnosis, and management of injection-related endophthalmitis: a literature review

BACKGROUND

Intravitreal medication injections represent the gold standard treatment for a variety of potentially blinding chorioretinal vascular diseases. Despite their excellent safety profile, they are associated with the feared complication of injection-related endophthalmitis (IRE). Though the overall incidence of IRE is low, due to the ever-increasing number of injections being performed, it is a complication that all retina specialists are likely to encounter. This article reviews various factors that could potentially influence the risk of IRE and discusses evidence-based strategies for management.

METHOD

PubMed was searched for keywords "intravitreal injection" and "endophthalmitis" from the period of 1995-2021. Relevant articles were reviewed and selected articles were analyzed with respect to the incidence, potential preventive factors, clinical presentation, microbial profile, management, and outcomes for IRE.

RESULTS

There is strong consensus supporting the use of povidone iodine topical antiseptic, eyelid retraction away from the injection site, and avoiding treatment of eyes with active surface or eyelid disease, but there is less agreement on the use of face masks versus "no-talking" policies and optimal anesthetic technique. Current evidence comparing tap and inject or early vitrectomy for treatment of IRE is inadequate to determine an optimal treatment strategy.

CONCLUSION

Intravitreal injections are sight saving, but even using established prophylactic measures there remains a small but real risk of infectious injection-related complications. Further investigations comparing tap and inject versus vitrectomy may help to establish optimal treatment, although the rarity of IRE makes designing adequately powered prospective trials a difficult task.

Cooling Anesthesia for Intravitreal Injection: Results of the Prospective Open-Label, Dose-Ranging COOL-1 Trial

Purpose

To evaluate the safety and efficacy of a novel medical device to provide cooling anesthesia to the eye as local anesthesia for intravitreal injections.

Study Design

First in human, open-label study of 43 subjects assessed at three different doses: −10°C for 20 seconds (group 1), −15°C for 15 seconds (group 2), and −15°C for 20 seconds (group 3). Main outcome measures were safety and pain of injection using a numeric rating scale (NRS).

Results

Cooling anesthesia did not result in any serious ocular adverse events. One grade 1 adverse event was a vasovagal response during cooling administration which resolved immediately after cooling. Mean NRS scores at the time of injection for each group ranged from 2.5 to 4.3 There was a statistically significant difference between pain scores of the 3 groups at injection in aggregate but not in pairwise comparisons (P value = 0.047). There was a statistically significant decrease in pain from injection to 5 minutes post injection in all groups (P value = 0.00008, 0.003, 0.0005 for groups 1, 2, 3, respectively) as well as from 5 minutes to 24–48 hours (P value = 0.00001, 0.018, and 0.0545 for groups 1, 2, 3, respectively).

Conclusion

The rapid cooling anesthesia device was well tolerated for achieving local anesthesia among patients receiving intravitreal injections with no serious ocular adverse events.

Intravitreal Injection Therapy: Current Techniques and Supplemental Services

Purpose:

Intravitreal injection is the most frequently performed eye procedure in the world and is an essential component in the management of sight-threating retinal diseases and conditions. Given the seriousness and range of diseases treated and the risks of the procedure, retina specialists must weigh the pros and cons of each individual treatment. Complexities guiding injection treatment are multifaceted and involve patient-history review, careful examination, diagnostic testing selection and interpretation, customized medical decision-making, and follow-up considerations.

Methods:

This article by the Intravitreal Injection Task Force Committee of the American Society of Retina Specialists documents the intricacies and necessary components of the intravitreal injection procedure.

Results:

By expert consensus, the task force further recommends ancillary services and decision-making that may accompany intravitreal injection visits, when appropriate, to monitor response to treatment, adjust treatment, and manage additional considerations in the same or fellow eye.

Conclusions:

Retina specialists can optimize safety and therapeutic outcomes with individualized consideration and customization of intravitreal injection treatment for each patient.

Novel Needle for Intravitreal Drug Delivery: Comparative Study of Needle Tip Aspirates, Injection Stream and Penetration Forces

Purpose

To study the efficacy of a novel needle for intravitreal injection (IVI) in comparison to the conventional needle under experimental conditions.

Methods

The newly designed 30-gauge (G) needle (NDN) (EP 18158 542.3, patent pending) with occluded outer orifice and a side port for drug delivery was compared to the conventional standard hypodermic 30 G needle for IVI (SHN). An animal study to obtain needle tip aspirates was performed on 10 albino rat eyes. During IVIs, cellular content, which was cut by the needle tip, was aspirated. Cellular material was studied in regard to cell types and their quantity. The injection stream was studied using trypan blue dye in vitro and pig cadaver eyes. The penetration force was tested on polyurethane Testing Foil Strips PU 04 (Melab, Leonberg, Germany) by applying a velocity of 100 mm/min. The results were analyzed using descriptive statistics, correlation matrices and t-test methods with p<0.05 as statistically significant.

Results

Cytological analysis of the needle aspirates showed the presence of cellular content in each case. The amount of conjunctival, ciliary body epithelial cells and granulated basophilic protein sediments (sign of cellular damage) in the case of the NDN tips was significantly lower compared to the SHN. The average penetration force of the NDN was 0.791 N, and in the case of the SHN was 0.566 N. The injection stream study revealed a difference in the initial injection phase between the two needle types, although the diffuse filling of the vitreous area which surrounded the needle tip appeared to be similar.

Discussion

The NDN demonstrated superior performance with regard to a significantly reduced number of cells being captured by the needle tip. Delivery of the injected fluid into the vitreous cavity was comparable. In order to investigate superior properties of the NDN needle design, further studies with improved prototypes would be necessary.