Finding The Eye’s Natural Balance

Sponsored by Alcon

Surgeons are starting to embrace near physiologic IOP during cataract surgery, and they’re finding calmer chambers, happier patients and smoother cataract cases…proof that sometimes, nature really does know best.

Sometimes, the eyes prefer the way nature made them. Thanks to advances in surgical equipment and devices, cataract surgeons can now operate at near-physiological intraocular pressure (IOP) without sacrificing safety, efficiency or outcomes.¹

To understand why this approach is gaining momentum, we spoke with Dr. Shail Vasavada (India), a pioneer in low IOP cataract surgery and an advocate for bringing cataract procedures closer to the eye’s natural pressure.

Why surgeons are switching to physiological IOP

During cataract surgery, IOP can spike to levels that would make a glaucoma specialist break a sweat. “IOP can go as high as 80 to 90 mmHg during surgery,” said Dr. Vasavada. “In glaucoma, we are worried about 21 to 23 mmHg — and here we are operating at 60, 70 or 80 mmHg without any fear.”

Dr. Vasavada said that a study with Alcon’s INFINITI gravity-based fluid system was his turning point for adopting physiological IOP. The study showed that using lower bottle heights and flow rates led to significantly better outcomes², prompting the need to explore even lower settings with Alcon’s CENTURION (Alcon, Geneva, Switzerland).³

What they discovered was compelling and prompted Dr. Vasavada to explore even lower settings with Alcon’s upgraded system. “We realized that if we could go lower with INFINITI, we could go lower with CENTURION.⁴ That was the tipping point for us,” he recalled.

Lower pressure prioritizes safety during surgery

Patient safety was the top concern when Dr. Vasavada first began experimenting with low IOPs. Would the chamber remain stable? Would the risk of posterior capsule rupture rise?

To get answers, Dr. Vasavada and his colleagues studied two groups: one operating at 20 mmHg and low flow rates, and another at 55 mmHg and high flow rates. Similar to other studies, they found that the low-IOP group had better occlusion break response, surge control and more stable pressures.^2,5 In addition, a 2022 study demonstrated a significantly higher preservation of endothelial cell density at both day 4 and the 3-month follow-up when using near-physiologic IOP (20 mmHg) compared to high IOP (50 mmHg).⁶ Notably, this is a compelling finding because the phacoemulsification machine settings were nearly identical between the two [IOP] groups.

“Although it may sound counterintuitive, low intraocular pressure may have benefits⁶ — even for surge response and other issues,” he said.

“You finish the surgeries much faster¹ because you have fewer intraoperative issues, like iris flutter, pupil coming down during the surgery or anterior chamber fluctuations⁷,” he explained. “So, it’s more efficient time- and surgery-wise.”⁷

Happier patients, fewer surprises

Patients are simply more comfortable⁸, too. When cataract surgery is performed at 20 to 30 mmHg IOP instead of the traditional 50 to 60 mmHg, according to Dr. Vasavada, more patients had corneal clarity (94.6% vs 69.0% in the high IOP group, p<0.01), more had mild edema resolving by week 1, patients reported significantly reduced perioperative pain (1.67 vs 3.19 on a 10-point scale, p<0.01) — all these directly can contribute to faster visual recovery and potentially fewer postoperative visits.¹

Operating at lower IOPs also helps protect delicate intraocular structures. It demonstrated less retinal microvascular disturbance (i.e. posterior-segment circulation), found no increase in complications and reported less retinal changes.⁹

Another benefit Dr. Vasavada has noticed? The lack of disruption to anterior chamber structures as evidenced by less postoperative inflammation, less disruption to the corneal endothelium, and less corneal edema in the early postoperative period.¹⁰ “Having a few central Descemet’s folds was very common, particularly with denser cataracts and we would counsel patients that you’ll have a longer recovery time — and now we no longer have to do that.”

Lower pressure, smoother surgeries

A common misconception is that operating at lower IOPs have detrimental effects on the cornea and anterior segment. In reality? Cataract surgery at a near-physiologic IOP showed a higher preservation of endothelial cell density versus high IOP (50 mmHg).⁶

Smoother surgeries with fewer complications also creates a better patient experience, which can enhance their overall perception of cataract surgery.

A valuable edge in challenging cases

“[Physiological IOP]⁶ definitely gives us an edge in difficult case scenarios, especially in young patients with posterior polar cataracts,” said Dr. Vasavada. “You don’t want a high IOP intraoperatively because the posterior capsule is very fragile.”¹¹

Patients with extremely high myopia also benefit from lower intraoperative IOPs.^1,8 “They feel the stretch, they feel the pain and surgeons find it very difficult — even with low bottle heights — to actually reach the nucleus,” he continued. Operating at lower IOPs can make cataract surgery less painful and more comfortable for these patients.

Bringing physiological IOP into the OR

Thinking about lowering intraoperative pressure to something closer to the eye’s natural state? Dr. Vasavada has some practical advice for putting the concept into practice.

#1 Don’t get stuck on a particular number. “When we say physiological IOP, it doesn’t always mean 20 mmHg for every eye. It may mean a range,” he noted. Dr. Vasavada’s sweet spot is typically 20 to 40 mmHg, but he’ll generally work between 20 to 30 mmHg.

For example, when he’s chopping or dividing the nucleus, he operates at 20 mmHg. During fragment removal, he increases the IOP to about 30 mmHg.

If you’re transitioning to a fluidics-based system, he recommends starting around 50 mmHg, which is already equivalent to a 75-cm bottle height in traditional setups.

“Once surgeons are comfortable with the machine, I would gradually start lowering IOP by 10 mmHg,” he said, “until they find their own ‘sweet spot’.”

#2 Embrace technological advances. According to Dr. Vasavada, two Alcon innovations have made the lower IOP surgical approach practical:

CENTURION’s Active Fluidics keeps the chamber stable regardless of the parameters used.³
The Active Sentry handpiece places a pressure sensor right at the phaco probe level, giving a faster response to surge mitigation.⁴

“The Active Fluidics and the Active Sentry handpiece combine^5,13 to improve efficiency,” he said.

Although many surgeons worry about increased surge when operating at low IOPs and higher vacuum settings, Dr. Vasavada explained that complete occlusion is rare, and the balanced tip and cutting efficiency of the phaco probe make a difference.³

“With the Active Sentry handpiece^5-6, the pressure and surge response is so fast that even if I’m working at an IOP of 20 mmHg and a maximum vacuum of 700, I’m not worried about the posterior capsule or surge at all,” he noted.

#3 Make reductions in the transition. In the initial transition period, when you’re lowering IOP, Dr. Vasavada advised to lower both the aspiration flow rate and vacuum.

For example, if you use an aspiration flow rate of 40 to 45 cc per minute, reduce it to 30 to 35 cc per minute. “Once you get the hang of the chamber stability and how the chamber is deepening at an IOP of 30 or 20 mmHg, then you can step back on your vacuum and flow rate,” he said.

The future of physiological IOP in cataract surgery

Dr. Vasavada believes that operating at physiological IOP will soon be the norm in the next few years. Even though naysayers may suggest operating at lower IOP could take longer or compromise safety¹⁴, the evidence has found that operating near physiologic IOP resulted in less trauma to corneal physiology and maintained the stability of the anterior vitreous face (AVF).⁷ Dr. Vasavada says that “there are no downsides to operating at a low IOP—and there are some added benefits.”

For surgeons hesitant to change a system that’s already working, he offered a gentle nudge: “But that’s how medicine is—if you don’t keep evolving, sometimes you get left behind.”

“Keep an open mind,” he continued. “Try it out, and then decide whether it works for you, rather than having a fixed mindset of ‘this is how it is, and this is how it will be.”

He said that operating at near physiological intraocular pressures has definitely helped him improve his surgical performance, patient comfort^1,8 and his overall outcomes.³

“I would urge everyone that it’s time – we’ve been doing things far too long in the same way,” he concluded. “It’s time that we refine it even further and take the next step. The willingness to evolve in the pursuit of better patient outcomes stands as both a privilege and an obligation for every surgeon.”

References

Sarossy A, Chakrabarti R. Physiological Intraocular Pressure in Cataract Surgery: A Comparative Consecutive Case Series Study. Clin Ophthalmol. 2025;19:2289-2294.
Vasavada V, Raj SM, Praveen MR, Vasavada AR, Henderson BA, Asnani PK. Real-time dynamic intraocular pressure fluctuations during microcoaxial phacoemulsification using different aspiration flow rates and their impact on early postoperative outcomes: a randomized clinical trial. J Refract Surg. 2014;30(8):534-40.
Liu Y, Hong J, Chen X. Comparisons of the clinical outcomes of Centurion® active fluidics system with a low IOP setting and gravity fluidics system with a normal IOP setting for cataract patients with low corneal endothelial cell density. Front Med (Lausanne). 2023;10:1294808.
Alcon data on file, 2017, REF-02559.
Vasavada V, Vasavada AR, Vasavada VA, Vasavada SA, Bhojwani D. Real-time dynamic changes in intraocular pressure after occlusion break: comparing 2 phacoemulsification systems. J Cataract Refract Surg. 2021;47(9):1205-1209.
Kokubun T, et al. Verification for the usefulness of normal tension cataract surgery. Presented at: The 126th Annual Meeting of the Japanese Ophthalmological Society (JOS); Apr 14-17, 2022; Osaka, Japan.
Vasavada V, Srivastava S, Vasavada V, et al. Impact of fluidic parameters during phacoemulsification on the anterior vitreous face behavior: Experimental study. Indian J Ophthalmol. 2019;67(10):1634-1637.
Scarfone HA, Rodriguez EC, Rufiner MG, et al. Vitreous-lens interface changes after cataract surgery using active fluidics and active sentry with high and low infusion pressure settings. J Cataract Refract Surg. 2024;50(4):333-338.
Raimondi R, Sow K, Peto T, et al. The effect of intraocular pressure during phacoemulsification in patients with either diabetic retinopathy or glaucoma; a randomized controlled feasibility trial. Graefes Arch Clin Exp Ophthalmol. 2025;263(8):2277-2288.
Rauen MP, Joiner H, Kohler RA, O’Connor S. Phacoemulsification using an active fluidics system at physiologic vs high intraocular pressure: impact on anterior and posterior segment physiology. J Cataract Refract Surg. 2024;50(8):822-827.
Sharif-Kashani P, Fanney D, Injev V. Comparison of occlusion break responses and vacuum rise times of phacoemulsification systems. BMC Ophthalmol. 2014;14:96.
Cyril D, Brahmani P, Prasad S, et al. Comparison of two phacoemulsification system handpieces: prospective randomized comparative study. J Cataract Refract Surg. 2022;48(3):328-333.
Machiele R, Motlagh M, Zeppieri M, et al. Intraocular Pressure. [Updated 2024 Feb 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532237/ Accessed on August 25, 2025

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