Over the last two decades there has been a gradual but definite trend towards performing most vitreoretinal (VR) surgery under local anaesthesia (LA) as an outpatient procedure (Cannon et al. 1992; Costen et al. 2005). There are numerous reports on visual perceptions during cataract surgery (Tranos & Peter 2005), but the medical literature on similar experiences during VR surgery is relatively scarce (especially in terms of prospective studies). Patients who opt for LA often ask what they can expect and, particularly, whether they will be able to see anything or feel any pain during the operation. This information could help immensely in preoperative counselling.
We undertook a prospective study to analyse the visual experiences and pain of patients undergoing VR surgery under LA. The main aims of the study were:
- 1 to record the incidences of various visual experiences;
- 2 to identify any pre- or intraoperative factor(s) influencing those experiences, and
- 3 to record subjective pain scores during VR surgeries.
Between October 2005 and September 2006, all patients (n = 68) undergoing VR surgery under sub-Tenon (ST) anaesthesia using standard 20-G ports were included in this study. (All surgeries were performed by one surgeon.) Patients completed a standard questionnaire within 24 hours of surgery. It recorded visual experiences and pain scores (on a scale of 1–10).
Patient demographics and results are summarized in Table 1. Among various visual sensations, 75% (51) of patients visualized colours, 88% (60) saw bright intense light and 46% (31) saw moving instruments. Almost all the colours of the light spectrum (sometimes multiple colours) were perceived, but white, red and blue were most common. Some patients vividly described seeing the colour of the membrane blue used during the operation as purple drops against a light background. A few patients also experienced light flashes and saw faces or shapes, but these were infrequent. All patients found the subjective visual experiences to be acceptable.
|Mean age, years||66.27|
|Male : female||1 : 1|
|Mean duration of surgery, minutes||82.84|
|Indication for surgery|
|Different visual sensations|
|Pain scores (1–10 = minimum–maximum)|
|Mean surgical pain score||2.59|
|Mean pain score for longer surgeries (>83 mins); n = 12||5.16|
|Mean pain score for shorter surgeries (<83 mins); n = 56||2.12|
In this study, we did not find any difference in visual experiences based on age, sex or race. Patients with better preoperative visual acuities (≥ 6/60) had more visual sensations than those with poor preoperative vision (< 6/60), but the difference was not statistically significant.
Patients’ macular status did not affect the visual experiences. Of the 68 patients, 29 patients (21 with macular hole, eight with macula-off retinal detachment) had very poor macular function, but their visual experiences did not differ statistically from those of the other patients.
The mean pain score for all VR procedures was 2.588. Longer procedures (> 83 mins) showed higher average pain scores (5.16 versus 2.12). Patients tolerated sub tenons (ST) anaesthesia well; only 10 patients (with longer duration of surgery) needed supplemental anaesthesia in the form of amethocaine drops (towards the end of the operations). Several objective measures correlated with elevated pain: duration of surgery (p = 0.005, t-test); previous intraocular surgery under LA (n = 18; p = 0.03, Fisher’s exact test), and type of surgery (p < 0.004, chi-squared test). Procedures involving scleral buckling had significantly (p < 0.0005) higher pain scores (5.33 versus 2.32). There was no correlation between intraoperative pain scores and different visual sensations (p > 0.05, Spearman’s correlation test).
In our study, none of the patients actually found the subjective visual experiences frightening. This is in slight disagreement with the findings of a study by Tan et al. (2005), in which 13.8% of patients found their experiences frightening. This may be explained by the fact that we had specifically counselled our patients regarding these visual sensations preoperatively and thus our patients may have been expecting them and consequently did not find them frightening.
Although this study gives a fair idea of the visual sensations and degree of pain experienced by patients during VR surgery under local anaesthesia, we still do not know the cause(s) of variations in different patients. However, we can certainly use this information to provide better preoperative counselling for patients who choose to undergo VR procedures under LA.