The SAFE-VISA study on safety and feasibility of sutureless vitrectomy in sub-Tenon anesthesia showed good results in terms of intra- and postoperative pain perceived, intraoperative anxiety, intra- and postoperative adverse events, and surgical feasibility. Perceived pain did not differ 1 day after surgery comparing sub-Tenon and general anesthesia. A correlation between perceived pain and surgery duration or pain and patients’ age was not found; none of the patients demanded an anesthetic top up. We found a moderate correlation between levels of pain and anxiety perceived during surgery in sub-Tenon anesthesia.
Pain
Visual analogue scales have been used successfully to assess pain in various similar studies and in other topics [
15,
16,
20,
21].
In a prospective, randomized single center study on 26 patients receiving 23 Ga vitreoretinal surgery for macular hole or epiretinal membrane, Ribeiro et al. reported a median pain score of 1.0 on a VAS from 0.0 to 100.0, with 50.0% of patients reporting no sensation of pain at all during surgery [
17]. In their study, patients received 2.0% lidocaine gel in the superior and inferior fornices, followed by a 2.0–4.0 ml 1.0% ropivacaine injection in the sub-Tenon’s space [
17]. Furthermore, it is noteworthy that patients in their study received 5.0 ml midazolam 5 mg/ml intravenously [
17]. Compared to our study, differences in the applied anesthetics and the standard application of 5.0 ml midazolam 5 mg/ml, a benzodiazepine, could explain the lower reported pain perception. In other settings, a sedoanalgesia combination showed lower levels of perceived pain than analgesia alone [
22]. We decided not to use systemic anxiolytic benzodiazepines to reduce risk of cardiovascular depression, avoid obligatory involvement of anesthesiologists and postoperative monitoring, thus reducing workload, and accelerating the workflow up to, and after the surgery itself. 1.0% ropivacaine has been reported to have similar analgetic properties as 0.25% bupivacaine used in our study [
23]. Even though surgery duration was longer in their study (62.0 min vs. 22.7 min), pain perception was reported lower than in our study [
17]. This supports our finding, that surgery duration is not obligatory correlated with pain experienced.
In a retrospective study on 30 eyes receiving 25 Ga vitreoretinal surgery for macular hole, epiretinal membrane and vitreous hemorrhage for causes other than retinal detachment or proliferative diabetic retinopathy, Roman-Pognuz et al. reported 76.7% of patients perceiving no pain during surgery, and 23.3% perceiving mild pain (2.0 on a VAS from 1.0 to 4.0) [
15]. Patients received 5.0 ml 2.0% mepivacaine after topical anesthesia with oxybuprocaine eye drops (concentration not disclosed) three times [
15]. In both studies mentioned above, number of patients reporting no perception of pain (50.0% and 76.7%) was lower than in our study (36.3%). Compared to the studies mentioned above, patient age was highest in our study (72.9 vs. 64.0 and 69.6 years), while surgery duration was shortest (22.7 vs. 62.0 and 42.2 min) [
15,
17].
In a prospective randomized study, Lai et al. reported pain levels during surgery in sub-Tenon anesthesia of 1.7 on a VAS from 0. to 10.0 in 30 eyes receiving pars-plana vitrectomy (with or without intraocular lens implantation), pars-plana vitrectomy and scleral buckling, or scleral buckling surgery only, matching our results of 1.8 on the VAS [
16]. The conjunctiva was opened prior to trocar placement and sutured at the end of surgery [
16]. In both our and their study, patients were asked the day after surgery, and curiously, in both studies patients received an anesthetic mixture of 50:50 4.0% lidocaine: 0.75% bupivacaine [
16]. While in our study, supplemental anesthesia was not needed, Lai et al. gave 36.7% of the patients a mean 1.6 ml of additional anesthetic mixture [
16]. It is of note, that intravenous midazolam (0.5–3.0 mg), fentanyl (20.0–100.0 µg), or propofol (0.0–100.0 mg) was given at a dose determined by the anesthesiologist prior to surgery for sedation [
16].
Gill et al. reported pain levels of 3.4 on a VAS from 1.0 to 10.0 intraoperatively [
18]. In their prospective study, 27 patients received a single 5.0 ml inferonasal sub-Tenon injection of a 50:50 mixture of 2.0% lidocaine and 0.5% bupivacaine with 150.0 IU hyaluronidase, an enzyme suspected to reduce the effective anesthetic volume [
18,
24]. Oculopression after application of the sub-Tenon anesthesia was not applied [
18]. Patients did not receive any additional sedatives [
18]. 70.4% of the patients received cryotherapy, while none of our patients underwent that treatment, potentially causing a higher pain perception [
18].
Regarding pain perceived during surgery, all authors concluded, that sub-Tenon anesthesia is a valid option, similarly effective as retrobulbar anesthesia, and more effective than peribulbar anesthesia [
4,
15,
17,
22]. Gill et al. added that a two-quadrant sub-Tenon injection provided significantly better perioperative anesthesia for vitrectomy compared with a standard single-quadrant technique using the same mixture [
18].
Bayerl et al. compared pain perception after 23 Ga vitrectomy under general anesthesia with and without additional retrobulbar anesthesia in 130 eyes in a prospective setting [
25]. Twenty-four hours after surgery, only one patient (2.4%) receiving sub-Tenon anesthesia only reported pain over 2.0 on a numerical pain scale, similar to the VAS used in our study [
25]. In our study, 8.8% of patients had pain levels above 2.0 on the VAS and mean perceived pain of 0.6. The authors concluded that additional retrobulbar anesthesia was not beneficial in preventing or reducing pain [
25].
A patient acceptable symptomatic state (PASS) is understood as the outcome score on the VAS a patient needs to have (or better) to “feel good”, and is defined, i.e., for various orthopedic diseases [
26]. For vitreoretinal surgery, or ophthalmological surgery in general, a PASS has not been defined yet.
Anxiety
To our knowledge, none of the studies published on sub-Tenon anesthesia for vitreoretinal surgery incorporated a VAS for anxiety. The VAS to evaluate anxiety has been validated [
27]. We showed a moderate correlation between pain perception and anxiety during surgery, fortifying the need for adequate analgesia. In a systemic meta-analysis by Obuchowska et al. on anxiety and fear in cataract surgery, pain during surgery was identified to be the second most common cause of anxiety (41.0%) [
28]. They concluded, that next to preoperative education and counselling for patients sufficient analgesia is crucial to reduce anxiety and fear [
28]. While reports on anxiety perception during cataract surgery are scarce, Foggitt et al. reported a median anxiety level of 2.0 of 7.0 on the VAS in 108 patients receiving, higher than the 2.3 of 10.0 during surgery we found [
29]. Overall, they deemed anxiety levels detected to be acceptable for surgery in local anesthesia [
29].
Visual sensation
In a prospective questionnaire survey, Vohra et al. reported that 90.0% of patients perceived light at some stage during vitreoretinal surgery under local anesthesia [
4]. Of these, 70.8% observed movements, 62.5% saw colors, 52.8% saw instruments and 33.3% saw flashes. The commonest observations were colorful swirls, black pipes, and the color red [
30]. 77.5% of patients received sub-Tenon anesthesia, while the rest received peribulbar block [
30]. Interestingly, 10.0% of patients reported to have not experienced any sensation of light during the entirety of the procedure, while, in our study only 3.0% stated to not have seen any light [
30]. This difference could be explained by 12.5% of patients having received peribulbar block as anesthesia [
30]. In other studies, a higher percentage of patients not perceiving any light was reported, too [
31]. Here, the difference could be explained due to patients being asked about their visual sensations during surgery, and not the day after [
31]. 2.7% of their patients felt that the experienced light perception was “frightening”, while the rest deemed it to be either “pleasant” (22.2%) or “bearable” (72.2%) [
30]. In our study, mean level of anxiety during surgery on the VAS was 1.3 in patients who reported to see details during surgery, while patients not seeing details reported an anxiety level of 2.8 (
P = 0.069). Overall, Vohra et al. and our study did not find evidence that visual perception during surgery is linked to a disadvantageous course of the surgery [
30].
Complications
Subconjunctival hemorrhage occurred in 24.2% of patients receiving sub-Tenon anesthesia. Seen as a minor complication, patients, especially when using antithrombotic agents, should be informed about the transient and innocuous character of the bleeding [
32,
33].
Gill et al. reported on chemosis, a parameter we also incorporated in our study. 0.6 quadrants were affected in their group of patients, compared to 1.0 quadrants in our study [
18]. There was no information on the course of chemosis on the day after surgery. Overall, chemosis did not affect the surgery. The incidence of chemosis in general is variable and depends on length of cannula, volume of the anesthetic, speed of injection and entry to the sub-Tenon’s space [
33]. Lerch et al. reported 14.8% of patients had chemosis that affected one quadrant, and 4.5% of eyes had chemosis affecting two or more quadrants [
34]. In our study, 45.5% of patients had chemosis in one quadrant, 21.2% in two or more quadrants during surgery. Differences in the cannula (single-use sterile polyurethane vs. metal blunt cannula in our study) used and speed of application could have led to higher rates of chemosis in our study. In our study, patients with filtrating glaucoma surgery in the past were excluded. In these patients, chemosis must be taken seriously [
33].
Slight and severe complications such as cilioretinal artery occlusion, anaphylaxis, perforating the globe, injuring the optic nerve, inducing retrobulbar hemorrhage and injecting intravascularly resulting in brainstem anesthesia were not seen [
2,
11,
12,
33,
35]. We conclude that sub-Tenon anesthesia can be applied safely in vitreoretinal surgery.
Limitations
The design of the study made it impossible to mask the groups or blind the surgeon. Randomization of both study arms was not practical, since in Germany, vitreoretinal surgery in general anesthesia is the standard procedure. As described above, we intentionally did not include retrobulbar anesthesia in our study, due to a reported increased risk of complications. Other studies did not show inferiority of sub-Tenon anesthesia [
15‐
17]. While asserting world-wide use of sub-Tenon anesthesia is difficult, especially in vitreoretinal surgery, there seems to be a move away from retro/peribulbar anesthesia using a sharp needle, towards sub-Tenon or topical anesthesia in cataract surgery [
33]. As this study was non-randomized by design, the possibility of confounding factors must not be overlooked. Patients who denied surgery in sub-Tenon anesthesia were not included in the group of patients who underwent surgery in general anesthesia. In doing so, possibly overly sensitive patients were not over-represented in the respective group. As for patient characteristics, patients in the sub-Tenon group were older (
P = 0.002) and more often pseudophakic (
P < 0.001). While no conclusive statements were made, studies on the perception of pain in relation to age suggested that older patients report lower intensity of postoperative pain, though not specifically in vitreoretinal surgery [
36]. Considering lens status, studies on pain perception during surgery on the first compared to the second eye should be taken into account [
19]. For second eye surgery, higher pain perception was reported, possibly related to lower anxiety before the second surgery [
19]. Pain and anxiety were enquired on the day after surgery. While different results immediately after surgery were possible, assessing these parameters on the day after surgery is common practice [
37]. A significant difference in surgery duration reflects the real-life data the population was drawn from. It could also be the case, that in general anesthesia, the surgeon felt more comfortable with taking time during surgery. Further studies could investigate differences in sub-Tenon surgery with and without sedoanalgesia or an anesthesiologist in stand-by, respectively.