Surgical Solutions · Evidence Review
The fluid that fills
the eye during surgery.
During phacoemulsification, a large volume of irrigating solution flows across the corneal endothelium, a single layer of cells that does not regenerate. This guide compares balanced salt solution, fortified “plus” solutions, lactated Ringer’s and saline, using fifty years of laboratory work and the randomised trials that followed.
saline vs BSS, in vitro
meta-analysis
of bottle height
By Girish Dave, Agaaz Ophthalmics · Updated 23 October 2026 · Educational content for eye-care professionals
Section 01 — Why Composition Matters
The endothelium is bathed
in whatever we pour in.
The corneal endothelium keeps the cornea clear by pumping water out of the stroma. Its pumps need calcium, magnesium, potassium, a bicarbonate buffer and an energy source. Aqueous humour supplies them. During surgery, the irrigating solution replaces the aqueous, so its ionic make-up, pH and osmolality should approximate the fluid it displaces.[14]
Volume matters as well as chemistry. In a prospective study of 859 eyes, greater infusion volume was an independent predictor of endothelial cell loss, alongside nucleus hardness and size; firm nuclei were the strongest risk factor.[11] Our patient guide to corneal endothelial cell loss covers why these cells matter for life.
In laboratory perfusion of isolated corneas, 0.9% saline caused the fastest swelling, lactated Ringer’s less, standard BSS less again, and a glutathione–bicarbonate Ringer’s solution (the basis of BSS PLUS-type fortified solutions) almost none. In routine cataract surgery, randomised trials found little or no difference in long-term endothelial cell loss between these clinical solutions. Fortified solutions did reduce corneal swelling on the first day in one trial, which matters most in compromised corneas and long procedures. Saline is not an intraocular irrigant.
Section 02 — The Laboratory Evidence
Swelling rates
in isolated corneas.
From the 1970s, Henry Edelhauser’s group perfused the endothelial surface of isolated corneas with each solution and measured how fast the cornea thickened. A cornea that thickens is a cornea whose pump is failing.
| Solution perfused | Corneal swelling rate | Endothelium |
|---|---|---|
| 0.9% sodium chloride | 98 µm/h (1976); 60–90 µm/h (1975) | Cells separated, extensive degeneration |
| Plasma-Lyte 148 | 47 µm/h | Extensive damage after 3 hours |
| Lactated Ringer’s | 39 µm/h (1976); 37–40 µm/h (1975) | Slower but progressive degeneration |
| Balanced salt solution | 24 µm/h (1976); 24–31 µm/h (1975) | Severe changes only after about 2 hours |
| Glutathione–bicarbonate Ringer’s | 4 µm/h | Minimal change for up to 6 hours |
Sources: Edelhauser 1975 (rabbit and monkey corneas)[1] and 1976 (rabbit and human corneas).[2]
A follow-up on human donor corneas compared the commercial fortified solution with lactated Ringer’s. With BSS PLUS, all corneas kept normal thickness and endothelial structure through three to four hours of perfusion; with lactated Ringer’s, only one of six did.[3] In living cat eyes, short irrigation (15–30 minutes) with either standard or fortified BSS left cell density unchanged, but after one to two hours standard BSS caused more corneal thickening and more variation in cell size and shape, a sign of a stressed endothelium.[4]
Section 03 — The Clinical Trials
In routine surgery,
the gap narrows.
Randomised trials in patients have mostly found small or non-significant differences in long-term endothelial cell loss, with a more consistent early advantage for fortified solutions.
| Study | Comparison | Finding |
|---|---|---|
| Matsuda 1991[5] RCT, fellow eyes, ECCE | BSS PLUS vs a citrate–acetate bicarbonate solution | Less swelling on day 1 with BSS PLUS; thickness equal at one week and one month; more cell loss with the comparator. |
| Puckett 1995[6] RCT, 64 patients, ECCE | BSS PLUS vs dextrose–bicarbonate lactated Ringer’s | No difference in change of cell size (P = 0.92), hexagonality or variability at two months. |
| Joussen 2000[7] Controlled trial, 80 patients, phaco | BSS PLUS vs modified Ringer’s, chilled vs room temperature | No difference in cell loss. Less corneal swelling on day 1 with BSS PLUS; equal by day 14. Temperature had no effect. |
| Kiss 2003[8] RCT, fellow eyes, 90 eyes | Dispersive OVD + BSS PLUS vs HPMC OVD + Ringer’s | Acute swelling +10.9 vs +9.8 µm, no significant difference; no difference in cell counts at 3 months. Marginally faster recovery with the costlier pair. |
| Nayak 2012[9] RCT, 70 eyes, phaco | BSS PLUS vs Ringer’s lactate | Cell loss at 6 months 5.03% vs 8.35% (P = 0.483, not significant). |
| Barroso 2025[10] Meta-analysis, 4 RCTs, 322 patients | Ringer’s lactate vs balanced salt solution | No difference in endothelial cell loss or central corneal thickness. |
Most of these trials enrolled healthy corneas and uncomplicated cataracts, and several were small. Absence of a significant difference is not proof of equivalence, especially for eyes with little endothelial reserve. The authors of the Joussen trial concluded that BSS PLUS may decrease corneal risk in compromised corneas or prolonged surgery.[7]
Section 04 — Interactive
Raise the bottle.
Watch the pressure.
In a gravity-fed system, the solution reaches the eye under the weight of its own column. The figure shows the static pressure that column creates, before any fluid flows.
Real surgery is never static. Aspiration draws fluid out, the wound leaks, and occlusion breaks cause surges. In an 80-eye randomised study, settings of 90 cm with 20 cc/min flow produced pressure peaks of about 69 mmHg, while 110 cm with 40 cc/min produced about 85 mmHg and a greater early change in corneal thickness.[12] Active-fluidics systems use pressure sensors to hold a preset target pressure rather than relying on bottle height.[13] In both cases, each millilitre that enters the eye has passed over the endothelium.
Section 05 — Choosing a Solution
Match the solution
to the eye and the case.
| Situation | What the evidence suggests |
|---|---|
| Routine phaco, healthy cornea | Standard BSS is the usual choice. Trials found similar long-term outcomes with lactated Ringer’s and fortified BSS.[9][10] |
| Fuchs dystrophy, guttata or low cell count | Fortified solutions have the laboratory advantage and less day-1 swelling; their use is reasonable when reserve is low.[3][7] See Fuchs’ dystrophy. |
| Long or complex cases (dense nucleus, small pupil, pseudoexfoliation, combined procedures) | Longer exposure is where differences between solutions grew in the laboratory and in vivo.[1][4] See pseudoexfoliation. |
| Cost-constrained, high-volume settings | Trials comparing costlier and lower-cost combinations found similar outcomes in unselected patients.[6][8] |
| Normal saline | Not an intraocular irrigant: fastest swelling and endothelial damage in the laboratory.[2] |
The irrigating solution is one layer of protection. A dispersive viscoelastic coat on the endothelium, careful fluidics and efficient phaco energy all work alongside it. Our guides to cohesive vs dispersive OVDs and the surgeon’s blueprint cover the rest of the sequence.
Section 06 — Agaaz Surgical Solutions
Irrigation and
endothelial protection.
Agaaz Ophthalmics has manufactured ophthalmic products since 2009 and exports to more than 15 countries. The products below are described as listed on their product pages.
Section 07 — FAQ
Frequently asked questions
about irrigating solutions.
Standard balanced salt solution (BSS) is a sterile salt solution buffered with acetate and citrate. BSS PLUS-type “fortified” solutions add bicarbonate, glucose and glutathione, bringing the composition closer to aqueous humour. In laboratory perfusion of isolated corneas, the fortified type kept the cornea at normal thickness for hours, while standard BSS let it swell slowly. In routine cataract surgery, randomised trials found the difference in endothelial cell loss to be small or not statistically significant.
Lactated Ringer's has been used widely, particularly where cost matters. A 2025 meta-analysis of four randomised trials (322 patients) found no difference from balanced salt solution in endothelial cell loss or corneal thickness after phacoemulsification. In the laboratory it performed worse than BSS during prolonged perfusion, so the evidence for equivalence applies to routine, uncomplicated surgery.
Normal (0.9%) saline is not formulated as an intraocular irrigant. In isolated-cornea experiments it produced the fastest corneal swelling of all solutions tested, about 98 micrometres per hour, with endothelial cell damage. It lacks the calcium, potassium, magnesium and buffer that the endothelium needs.
Probably not for short, routine surgery on a healthy cornea, where trials show similar long-term cell counts. The case for a fortified solution is strongest when the endothelium is already compromised, for example in Fuchs dystrophy or low cell counts, and in long or complicated procedures. One trial found less corneal swelling on the first day with BSS PLUS than with Ringer’s solution, though by day 14 thickness was equal.
In gravity-fed systems, the bottle height sets the pressure pushing fluid into the eye: each centimetre above the eye adds about 0.74 mmHg before any flow. Higher bottles keep the chamber deep but raise intraocular pressure. One randomised study measured higher pressure peaks and more early corneal swelling with a higher bottle and faster aspiration settings.
In one controlled trial of 80 patients, refrigerated and room-temperature solutions gave the same results for pupil size, endothelial cell loss and corneal thickness. Temperature did not affect any measured outcome.
References & Evidence Base
Peer-reviewed
citations.
Bibliographic data from PubMed (U.S. National Library of Medicine). Study type is shown for each source. Numbers in the text refer to this list.
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