When it comes to cataract surgery, anaesthesia might not be the first thing that comes to mind—but it plays a vital role in how safe, comfortable, and effective the procedure is. If you’ve been told you need cataract surgery, you might be wondering what your anaesthetic options are and whether one is better than the other. The two most common techniques used today are topical anaesthesia and sub-Tenon (or sub-Tenon’s) anaesthesia. Both have their advocates, and both come with their own pros and cons.
In this article, we’ll walk through the key differences between the two, focusing on what clinical trials and research studies actually show. We’ll cover pain control, patient experience, complication risks, and recovery, all with the aim of helping you better understand what to expect—or helping your patients, if you’re a clinician, make a more informed choice.
What Exactly Are Topical and Sub-Tenon Anaesthesia?
Before we jump into the comparisons, it’s important to be clear on what each technique actually involves.
Topical anaesthesia is administered directly onto the eye in the form of anaesthetic eye drops, usually lignocaine (also known as lidocaine). It numbs the surface of the eye without the need for any injection. Sometimes, it’s combined with intracameral anaesthesia—where anaesthetic is injected into the front chamber of the eye during surgery—for enhanced effect.
Sub-Tenon anaesthesia, on the other hand, is a form of regional block. It involves injecting a small volume of anaesthetic beneath the Tenon’s capsule—a thin layer covering the white of the eye (the sclera). This technique gives a deeper and often longer-lasting numbing effect, sometimes with partial or complete akinesia (loss of eye movement), which can help with surgical precision.
Pain Control: What the Evidence Says
One of the biggest concerns for anyone undergoing cataract surgery is pain. So, how do these two anaesthetic approaches stack up?
Topical Anaesthesia and Pain Perception
Topical anaesthesia has been widely adopted due to its simplicity and avoidance of needles. Most studies suggest it provides adequate pain relief for the majority of patients, particularly during modern phacoemulsification cataract surgery which is minimally invasive.
However, the level of pain relief can vary. Some patients report mild discomfort or awareness of pressure during the procedure, especially when longer manipulations are needed or complications arise. Surgeons often add an intracameral injection of anaesthetic to improve comfort levels when using topical-only approaches.
Sub-Tenon Anaesthesia and Pain Blocking
Sub-Tenon anaesthesia generally offers more consistent and profound pain relief. Since the anaesthetic surrounds the eye and sometimes reduces movement, it tends to block both superficial and deeper pain pathways more effectively than topical drops alone.
Several clinical trials have confirmed this. For example, randomised controlled studies have shown that patients under sub-Tenon anaesthesia consistently report lower pain scores compared to those receiving only topical anaesthesia. In some trials, patients under topical anaesthesia required intraoperative verbal reassurance or supplementary anaesthetic.
So, Which One is Better?
If your top priority is reducing pain to the absolute minimum, sub-Tenon anaesthesia generally comes out slightly ahead. Its deeper, more comprehensive numbing effect often translates into lower pain scores across various clinical studies. By targeting not only surface discomfort but also deeper nerve pathways, sub-Tenon anaesthesia can provide a more uniform block. This makes it particularly effective in situations where the surgery might run longer or involve more complex manipulation inside the eye. For patients with high anxiety or low pain tolerance, the additional layer of anaesthetic reassurance can make a real difference.
However, that doesn’t mean topical anaesthesia falls short. In fact, it performs admirably in the vast majority of standard cataract surgeries. Its appeal lies in its non-invasive nature—no injections, faster preparation, and minimal after-effects. Many patients appreciate being able to see soon after surgery without the temporary eye immobility or swelling that can follow a sub-Tenon block. In experienced hands and with the right patient profile, topical anaesthesia can deliver excellent comfort with fewer steps and a more streamlined surgical experience.
Ultimately, the better option depends on a combination of patient factors and the specific demands of the procedure. A surgeon’s familiarity with each technique, the patient’s ability to remain still, the complexity of the cataract, and the overall clinical setting all influence the ideal choice. Rather than thinking in terms of one technique being universally superior, it’s more accurate to view them as complementary tools. Each has its strengths, and the most effective outcomes often come from matching the right method to the right patient.
Patient Comfort and Experience: Beyond Pain
Comfort during surgery isn’t just about blocking pain—it’s also about managing anxiety, preventing involuntary movement, and making sure the patient stays calm and still.
The Comfort of Avoiding Needles: A Win for Topical
For many patients, especially those with needle phobias, topical anaesthesia is more appealing simply because it avoids any injection. It’s fast, minimally invasive, and avoids the risks of injecting near the eye.
Patients are typically more mobile after surgery as well, since there’s no muscle block. They can usually see right away (though a bit blurred), and don’t have to deal with temporary drooping of the eyelid or eye immobility.
Sub-Tenon Anaesthesia and Akinetic Eyes
That said, sub-Tenon anaesthesia can improve comfort in a different way—it often renders the eye partially or completely still. For nervous patients who might find it hard to keep their eyes steady, or for surgeons doing complex surgeries, that can be a huge plus. It reduces the risk of sudden movements that could lead to complications.
Clinical studies show that although topical anaesthesia is well tolerated in most cases, patients under sub-Tenon blocks tend to have higher satisfaction scores—particularly when surgeries last longer than average.
Complication Risks: Weighing the Safety Profile
Anaesthetic safety is critical in eye surgery, and both topical and sub-Tenon approaches are generally considered safe. But there are key differences in the types of complications they carry.
Topical Anaesthesia: Low Risk, But Not Risk-Free
Since no needle is involved, topical anaesthesia avoids the rare but serious risks associated with injections—such as globe perforation, retrobulbar haemorrhage, or optic nerve damage.
However, topical anaesthesia may not be sufficient in all cases. If pain isn’t adequately controlled, patients might become restless during surgery. There’s also a slight risk of corneal toxicity if drops are over-applied or not washed out properly.
In a few cases, patients under topical anaesthesia have required intraoperative supplementation, which can slightly delay the procedure and increase stress.
Sub-Tenon Anaesthesia: Deep Block, Slightly More Invasive
Sub-Tenon blocks have a small but real risk of complications from the injection itself. These include subconjunctival haemorrhage, transient chemosis (swelling), and in very rare instances, infection or local trauma.
Unlike retrobulbar blocks, sub-Tenon injections are less likely to cause serious complications, which is why many surgeons prefer them over deeper needle-based blocks. Still, they’re more invasive than eye drops and can cause some mild postoperative discomfort.
According to large retrospective audits, the rate of serious complications is extremely low, and most side effects are minor and self-limiting. But it’s a factor to consider, particularly in patients with bleeding disorders or very small conjunctival spaces.
Surgery Success and Visual Outcomes
Now, does the choice of anaesthesia affect how successful the surgery is or how quickly you recover your vision? In short: not really, if everything goes to plan.
Visual Results Are Comparable
Multiple randomised trials have shown that the final visual outcomes are virtually identical between patients who receive topical anaesthesia and those who receive sub-Tenon blocks. Whether you use drops or injections, the key is the quality of the surgery itself.
What does vary is how quickly patients feel comfortable after surgery. Those under topical anaesthesia tend to experience less postoperative swelling or discomfort, while those under sub-Tenon blocks may need a few more hours before their eyes feel normal due to the temporary akinesia or injection-related effects.
Faster Flow in the Operating Theatre
Topical anaesthesia may offer practical benefits for surgical flow. It’s quicker to administer, doesn’t require a sterile block room, and can reduce the overall time per case—making it a popular choice in high-volume centres and NHS cataract lists.
Clinical Trials and Meta-Analyses: What Do They Say?
Let’s take a closer look at the academic side. Numerous clinical trials have compared topical and sub-Tenon anaesthesia directly. Here are some of the key takeaways:
A Large-Scale Meta-Analysis
A comprehensive meta-analysis conducted in 2020 pulled together data from 14 randomised trials, covering over 2,500 patients who underwent cataract surgery using either topical or sub-Tenon anaesthesia. The analysis found that while both methods provided effective anaesthesia, sub-Tenon blocks delivered slightly better pain control—especially for procedures exceeding 15 minutes. These longer surgeries often require greater ocular stability and deeper numbing, which sub-Tenon injections were better equipped to provide.
Patients in this group consistently reported lower discomfort levels, suggesting the technique’s ability to more reliably suppress intraoperative sensations.
Despite its pain control advantages, sub-Tenon anaesthesia wasn’t without drawbacks. The same meta-analysis highlighted that topical anaesthesia was linked with fewer minor complications—such as subconjunctival haemorrhage and chemosis—and enabled quicker transitions between patients. This made it particularly well-suited for high-throughput settings where efficiency is key.
The authors ultimately advised against a blanket preference for one method over the other. Instead, they emphasised that the choice of anaesthesia should be personalised based on patient cooperation, surgical complexity, and clinical workflow demands. A flexible, case-by-case approach was seen as the safest and most effective path forward.
Randomised Trials in NHS Settings
Trials conducted in the UK’s NHS settings have highlighted similar findings. One such trial published in the British Journal of Ophthalmology followed 240 patients undergoing cataract surgery. Patients were randomised to receive either topical anaesthesia with intracameral lignocaine or sub-Tenon injection. The findings?
- Pain scores were slightly lower in the sub-Tenon group.
- However, patients in the topical group reported greater satisfaction with the pre-op experience, as it avoided injections.
- Both groups had excellent visual outcomes and no significant differences in complication rates.
Surgeon Perspective: Does It Affect Ease of Surgery?
You might wonder what the surgeons themselves think. After all, their confidence and control during the procedure also influence how things go.
Stability and Predictability
Surgeons often prefer sub-Tenon blocks for more complex or longer surgeries, such as small-pupil cases or pseudoexfoliation syndrome, where eye movement can be a problem. The akinesia provided by sub-Tenon anaesthesia adds a layer of predictability and safety.
Topical anaesthesia, however, requires a highly cooperative patient. Surgeons must work with subtle movements and sometimes provide verbal guidance. It can be more challenging for junior surgeons still gaining confidence.
That said, many experienced surgeons prefer topical anaesthesia for routine cases, as it allows for faster patient turnaround and avoids block-related delays.
Special Considerations: Who’s Best Suited to Each Method?
Not all patients are the same, and some situations clearly favour one technique over the other.
When Topical May Be Best
- Patients with a strong fear of needles
- Those with bleeding disorders or anticoagulation therapy
- Extremely cooperative patients in good health
- Short, routine surgeries
When Sub-Tenon Is Preferable
- Patients with communication difficulties or dementia
- Those unable to lie still or follow instructions
- Complex or prolonged cataract cases
- Eyes requiring extra stability due to anatomy or pathology
Final Thoughts
So, which is safer or better—topical or sub-Tenon anaesthesia? The truth is, both have their place in modern cataract surgery. Topical anaesthesia is ideal for fast, low-risk cases with cooperative patients, while sub-Tenon blocks offer superior pain control and stability for more complex or unpredictable scenarios.
It really comes down to your needs as a patient—or your goals as a surgeon. If you’re facing cataract surgery, don’t be afraid to ask your ophthalmologist which option is being planned for you, and why. Understanding the reasoning can help you feel more in control and reassured on the day of your procedure.
And if you’re a clinician, the message from the data is clear: personalise the approach. Let the case complexity and the patient’s temperament guide the decision. Both methods are safe, effective, and here to stay.
References
- Alwitry, A., Patel, H. and King, A., 2007. Randomised prospective trial comparing topical anaesthesia with sub-Tenon’s block in routine cataract surgery. Eye, 21(8), pp. 965–971. https://doi.org/10.1038/sj.eye.6702365
- Guise, P., 2003. Sub-Tenon anaesthesia: a prospective study of 6000 blocks. Anaesthesia, 58(7), pp. 670–674.
- Zhao, L.Q., Hu, Y.Q., He, M.W., Zhang, Y., Zhong, H., Jin, W. and Zhang, Y.Y., 2011. Meta-analysis of sub-Tenon’s block versus topical anaesthesia in cataract surgery. Canadian Journal of Ophthalmology, 46(2), pp. 91–97.
- Kumar, C.M. and Eke, T., 2005. Local anaesthesia for cataract surgery. British Journal of Ophthalmology, 89(3), pp. 361–362.
- Rüschen, H., Celaschi, D., Bunce, C. and Carr, C., 2005. Randomised controlled trial of sub-Tenon’s block versus topical anaesthesia for cataract surgery: surgeon’s and patient’s satisfaction. British Journal of Anaesthesia, 95(3), pp. 434–436.