Findings from a recent study published in Clinical Ophthalmology show that iota-carrageenan (I-C) eye drops eased dry eye disease (DED) symptoms and protected the ocular surface in adults with mild-to-moderate disease.
Give me some background first.
Some context: DED is one of the most common reasons patients see eyecare practitioners (as evidenced in the Tear Film Ocular Society’s DEWS II), and its global prevalence runs anywhere from 5% to 50% depending on region and age group (see this epidemiology report for more on this).
The lubricant market has been dominated for decades by hyaluronic acid (HA) products. Innovation since then has mostly meant new combinations of existing compounds.
But real gaps remain, with tolerability issues, little ability to help damaged tissue heal, and a therapeutic effect that can take weeks or months to kick in.
So what’s the argument favoring I-C drops?
The pitch: I-C is a natural polysaccharide extracted from red seaweed.
It forms a gel on contact with the ocular surface, holds water there, and thins under the shear of a blink so it does not fight the eyelid.
Among its unique characteristics: It acts locally, is not absorbed—and is listed as Generally Recognized As Safe (GRAS) by the FDA.
Now, talk about the study.
Investigators ran a prospective, single-arm, open-label trial at a single center in Spain. There was no control group. Participants used one drop of preservative-free (PF) I-C (3.2 mg/mL) in each eye, three times daily, for four weeks.
The setup:
- Symptoms were rated under two conditions at baseline and at the final visit
- A normal controlled environment (NCE) used 23°C, 50% humidity, no airflow
- An adverse controlled environment (ACE) dropped humidity to 10% and added airflow for 90 minutes to provoke dryness
The primary endpoint was the change in total DED symptom score after ACE exposure.
Talk about these participants.
Thirty adults with mild-to-moderate DED, defined as an Ocular Surface Disease Index (OSDI) score ≥13 and <33, diagnosed at least 3 months before study enrollment.
Demographics: Mean age was 50.6 years (range 22 to 77), and 67% were female.
Also take note: Two participants dropped out early and two missed the 80% compliance bar, leaving 26 who finished per protocol.
- Effectiveness was analyzed in the 28 participants with data at every visit.
Next up: the findings.
The headline number: After 4 weeks, the mean total DED score after ACE fell from 21.89 to 10.00—a drop of −11.89 points (95% confidence interval [CI] −15.11, −8.67; p<0.001)
- That is a 54% cut in symptom severity under adverse conditions.
Under NCE, the score fell by −8.07 points (95% CI −10.71, −5.43; p<0.001), roughly a 38% reduction. All seven individual symptoms contributed to the improvement.
Responders: Most participants improved. 93% (26 of 28) recorded a lower DED score after ACE, and 89% (25 of 28) after NCE.
Tell me more.
OSDI: The OSDI score dropped by −7.75 points (95% CI −10.86, −4.63; p<0.001)
- The minimal clinically important difference for OSDI in mild-to-moderate DED sits at 4.5 to 7.3 points, so this clears the bar for a clinically meaningful change.
Patient-reported change: On the Change in Dry Eye Symptoms Questionnaire (CDES-Q):
- 75% (21 of 28) reported feeling better, one reported feeling worse, and the rest noticed no difference
- Mean improvement among those who got better was 6.10 points
Let’s talk about the ocular surface and tear film.
Ocular surface protection: Corneal damage on the Oxford scale improved after ACE, from 0.89 to 0.52 (mean difference −0.38; 95% CI −0.59, −0.18; p<0.001)
- The ACE-induced spike in corneal damage seen at baseline was gone after four weeks of treatment.
Tear film stability: At baseline, ACE shortened tear break-up time (TBUT) versus NCE by 0.83 seconds.
- After treatment that gap shrank to 0.09 seconds, meaning the drops held the tear film together even under stress
- There was no measurable effect on tear evaporation or tear production by Schirmer test
Any notable limitations?
This was a small, single-center study with no control group, an open-label design that invites expectation bias, and only four weeks of follow-up.
- Long-term effectiveness, tolerability, and safety remain open.
Expert opinion?
The authors argued that I-C offers a natural, PF option with a notably low dosing burden as compared to OTC artificial tears.
They expect a similar or stronger effect in severe DED and see I-C as a fit for add-on therapy in patients whose dry eye stems from conditions like Sjögren’s syndrome.
Anything else?
Tolerability stood out: 90% of participants rated tolerability as good or very good after the very first drop, rising to 93% by week four. .
On safety: 21 of 30 participants (70%) reported a total of 107 adverse events (AEs), all of them mild, transient, and confined to the eye.
- The most frequent were eye pain (33%), then itching and blurred vision (27% each)
- There were no serious AEs, no deaths, and no pathologic intraocular pressure (IOP) readings
Take home.
For patients with mild-to-moderate dry eye, I-C drops cut symptoms by more than half under adverse conditions, protected the cornea, and stabilized the tear film, all on a TID schedule.A randomized controlled trial (RCT) is the next step before treating these results as settled.