The SCUT Trial: Do Steroids Help Bacterial Corneal Ulcers?

The SCUT trial, the Steroids for Corneal Ulcers Trial, is the largest randomized study of corticosteroids in bacterial keratitis.

For decades, clinicians argued about whether steroids reduce scarring or only delay healing, and the evidence was thin.

Also, the trial gave an answer that is more nuanced than either side expected.

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Why the SCUT Trial Was Needed

Much of the damage in a bacterial ulcer comes from the host inflammatory response, with neutrophils releasing enzymes that destroy the stroma.

Steroids suppress this inflammation, so they should reduce scarring, but they also impair healing and may allow organisms to multiply (see stromal corneal ulcers).

Small studies gave mixed results, and some concern remained from cases of worsening after steroid use in fungal or Acanthamoeba ulcers.

SCUT Trial: The Design

• Investigators enrolled patients with culture-positive bacterial corneal ulcers in India and the United States, within the first days of presentation
• All patients received topical moxifloxacin, and investigators then randomized them to topical prednisolone phosphate 1 percent or placebo, starting 48 hours after the antibiotic
• Investigators gave the steroid four times daily at first and tapered it over three weeks
• The primary outcome was best spectacle-corrected acuity at three months

The trial masked patients and included prespecified subgroups by ulcer severity and by organism (see the references).

SCUT Trial: Results at Three and Twelve Months

• There was no significant difference in three-month visual acuity between steroid and placebo groups
• Scar size at three months was not significantly different
• The time to re-epithelialization was slightly longer in the steroid group
• Rates of perforation and adverse events were similar
• At twelve months, the results were also similar between the groups

So steroids were not harmful in the doses and in the setting of the trial, but they did not give a clear benefit overall.

Subgroups and Their Meaning

The study suggested that eyes with central ulcers and poor baseline vision, below 20/400, may have had a better outcome with steroids, though the findings were not statistically conclusive.

Ulcers caused by Pseudomonas and other organisms had no clear pattern.

The study did not aim to test each organism.

The cautious conclusion is that steroids may help in some severe central ulcers, so do not expect a large benefit.

SCUT Trial: How to Apply the Trial

• Do not start steroids at the first visit, and begin the antibiotic first
• Consider steroids after 48 hours or more, when the infection is clearly responding, the organism is known to be bacterial. There is no suspicion of fungus, Acanthamoeba, or herpes
• Choose cases with a central ulcer or severe inflammation, and follow closely
• Use a low dose and taper, and keep the intraocular pressure in mind
• Avoid steroids in Nocardia or fungal ulcers, and in patients who cannot be seen often

Stop steroids if the ulcer worsens or the response stalls.

Limits of the Trial

The trial excluded ulcers close to perforation, and those in which clinicians suspected fungus.

The study had power to detect a difference of a certain size, so it could have missed a smaller benefit.

Also, the data may not apply to every population or to different antibiotic regimens.

A Practical Protocol Many Clinicians Follow

First, scrape and culture, and start a broad-spectrum antibiotic at a loading dose and then every hour or two while awake.

At each review, record the size of the infiltrate and the epithelial defect, and the depth and the anterior chamber response.

If the ulcer is responding at 48 hours, with a clean culture result that shows bacteria and not fungus or amoeba, discuss adding a steroid in cases with a central ulcer or heavy inflammation.

Use prednisolone 1 percent four times daily, and taper over weeks according to the response.

Cases in Which Steroids Should Be Avoided

• Ulcers in which a fungal, Acanthamoeba, or Nocardia infection is possible
• Very thin corneas with imminent perforation
• Patients who cannot attend frequent follow-up
• Uncontrolled culture results, or an ulcer that is worsening on treatment

Related Reading

The trial adds to the wider story of infectious keratitis, in which the organism, the speed of treatment, and the quality of follow-up matter most (see why some keratitis cases fail treatment).

Patients should understand that the aim of a steroid is to limit scarring, that the benefit is uncertain, and that doctors stop the drops if healing slows.

Document the discussion, and arrange review within two to three days after starting.

For the latest studies, see the PubMed results for SCUT trial.

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References

1. Srinivasan M, Mascarenhas J, Rajaraman R, et al. Corticosteroids for bacterial keratitis: the Steroids for Corneal Ulcers Trial (SCUT). Arch Ophthalmol. 2012;130:143-150.
2. Srinivasan M, Mascarenhas J, Rajaraman R, et al. The Steroids for Corneal Ulcers Trial: study design and baseline characteristics. Arch Ophthalmol. 2012;130:151-157.
3. Austin A, Lietman T, Rose-Nussbaumer J. Update on the management of infectious keratitis. Ophthalmology. 2017;124:1678-1689.
4. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 8: External Disease and Cornea. AAO; current edition.