Ocular inflammation contributes to a number of patient symptoms and, in some cases, can even result in a loss of visual acuity. This month’s column will review recently released information that may provide guidance to manage the often-devastating effects of corneal inflammation associated with microbial keratitis.

Additionally, we will cover a new, in-office test that can aid practitioners in diagnosing ocular surface inflammation and selecting an appropriate treatment regimen.

Revisiting SCUT
We’re all aware of what causes a corneal ulcer: the infectious agent adheres to the corneal epithelium and penetrates into the stroma. The response to the infection is inflammation, degradation of corneal structural proteins, ulceration and scarring.¹

Because steroid use to manage infectious keratitis is controversial, many were hopeful that the NEI’s Steroids for Corneal Ulcers Trial (SCUT) would provide insight on this topic when it was published. To some extent, it did.

SCUT enrolled 500 patients with culture-confirmed bacterial ulcers and randomized them to either prednisolone or a vehicle with a tapering dose over a three-week period; all patients first received moxifloxacin for two days. As we learned in 2012, the study found that a majority of subjects did not demonstrate an improved outcome in best spectacle-corrected visual acuity (BSCVA) at three months, nor did they experience an increased incidence of side effects.²

Those who presented with the most central, severe corneal ulcers—which resulted in visual acuity of count fingers or worse—did appear to benefit from steroid use at the three-month evaulation.² While this study may not have had a radical impact on clinical practice, it did provide some reassurance to those who opt to use steroids in corneal ulcer management.

Additionally, this trial exemplifies why it is often important to read more than just the abstract to understand the nuances of a study. For example, just 3% of the patients were recruited from the US, while the remaining 97% were from India (of which 44% were agricultural workers).³  As such, the organisms causing the ulcers were different than those expected in a study population primarily from the US.

Another factor to consider: only eight of the 500 subjects were CL wearers—a statistic atypical of a population presenting in the US with corneal ulcers. Also, the steroid used was prednisolone phosphate rather than acetate; ocular penetration is much poorer in the former once the cornea has re-epithelialized.⁴ This choice of steroid prompts the question: Had the acetate formulation been used, would the outcome have been different?

Now, with new 12-month SCUT data published on BSCVA and corneal scar size in 399 cases from the original sample, we’ve learned:^5,6

• Myofibroblasts and fibroblasts—active during wound healing—may help restore corneal transparency.

• There is some thought that the steroid benefit may be delayed.

• Immune-mediated tissue damage may be reduced, corneal remodeling may occur and the scar density may be reduced well after steroid use has been discontinued.

Following this 12-month analysis (note that steroid use had been discontinued for over 11 months), the researchers concluded that adjunctive topical steroid therapy might be associated with long-term clinical improvement in corneal ulcers not caused by Nocardia organisms.

In a small case series that examined five patients from SCUT, McClintic et al. published dramatic images at presentation, three months and 12 months. Over the course of the study, the density of the opacity in each patient was dramatically reduced by the 12-month evaluation.

Additionally, when compared to the three-month visits, these patients also exhibited improved BCVA (when fitted with rigid contact lenses) at the 12-month follow up.⁷ This case series demonstrates that corneal scars may continue to improve for many months after the ulcer has healed and the topical steroid has been discontinued.

Examine the Tears
Matrix metalloproteinases (MMP), a family of proteolytic enzymes involved in remodeling of normal and pathological tissue, have the ability to degrade all components of the extracellular matrix.⁸

While the number of distinct MMP enzymes continues to grow, one is of particular interest to eye care professionals. MMP-9, produced by stressed epithelial cells on the ocular surface, is detected in higher levels as a non-specific inflammatory marker of ocular surface disease. Elevated MMP-9 levels are found in a number of conditions, including ocular rosacea, meibomitis, Sjögren’s syndrome and recurrent corneal erosions.⁹

Studies have shown that the range of MMP-9 in normal tears is between 3ng/mL and 40ng/mL.¹⁰ A level greater than 40ng/mL is indicative of inflammation. Additionally, there is a direct correlation between MMP-9 concentration and the severity of dry eye (Table 1).¹¹

Solomon et al. showed that MMP-9 levels increased 66-fold in patients with meibomian gland dysfunction and 90-fold in patients with Sjögren’s syndrome when compared to normal controls.⁹

In February 2014, Rapid Plasma Screening (RPS) received FDA CLIA-waived approval for a new in-office test called InflammaDry. It uses a process in which two antigen-specific antibodies capture the MMP-9 antigens. The test is confirmatory for inflammation if MMP-9 levels are 40ng/mL or higher.

	Table 1. Severity Levels of Tear Dysfunction and Corresponding Average MMP-9 Levels.11
	Severity Level	Average MMP-9 Level
	One	35.57ng/mL
	Two	66.16ng/mL
	Three	101.42ng/mL
	Four	381.24ng/mL

Those familiar with the AdenoPlus detection test from the same manufacturer will note that the sample collector and test cassette look identical. However, the way samples are collected is different. With AdenoPlus, the collector should be dabbed and dragged along the inferior palpebral conjunctiva to rupture the follicles (freeing adenoviral hexon proteins). When collecting a sample with InflammaDry, the dragging motion is omitted.

The collector should be dabbed six to eight times, moving from temporal to nasal, allowing the patient to blink after each two dabs. A final five-second press on the nasal palpebral conjunctiva is recommended to ensure adequate saturation of the sampling pad. The collector is then snapped into the test cassette and placed in buffer for 20 seconds.

The results are available in 10 minutes. A single blue line indicates a good test and a normal MMP-9 level, while an additional red line of any intensity confirms the MMP-9 is at least 40ng/mL. The line intensity provides a semi-quantitative indicator of the concentration of MMP-9s; a lighter shade of red indicates lower MMP-9 levels, while a darker line signifies higher levels.

A multi-center trial noted a sensitivity of 85% and a specificity of 94% for InflammaDry. In the clinical setting, we may be able to use this test to identify dry eye patients who have an inflammatory component. These patients would benefit from anti-inflammatory therapy, such as corticosteroids, cyclosporine and doxycycline—all of which have been shown to inhibit MMP-9 activity.

Conversely, we could also use the test to determine when to avoid therapies in patients with normal levels of MMP-9; this might help to avoid treatment failures.

Overall, the test may help to better determine appropriate treatments for our dry eye patients. The company also suggests it may be of benefit to identify elevated MMP-9 levels in patients prior to surgery (e.g., refractive surgery). Pre-surgical intervention with anti-inflammatory therapy for patients with elevated MMP-9 levels could then improve post-surgical outcomes and reduce potential complications.¹²  

1. Tull SS, et al. Science and strategy for preventing and managing corneal ulceration. Ocul Surf. 2007;5(1):23-39.
2. Srinivasan M, et al. Corticosteroids for bacterial keratitis. Arch Ophthalmol. 2012;130(2):143-50.
3. Srinivasan M, et al. The steroids for corneal ulcers trial. Arch Ophthalmol. 2012;130(2):151-57.
4. Bartlett JD, Siret DJ. Clinical ocular pharmacology, 5th edition. St. Louis: Butterworth Heinemann Elsevier, 2008.
5. Srinivasan M, et al. The steroids for corneal ulcers trial (SCUT): secondary 12-month clinical outcomes of a randomized controlled trial. Am J Ophthalmol. 2014;157(2):327-33.
6 .Hassell JR, Birk DE. The molecular basis of corneal transparency. Exp Eye Res. 2010;91(3):326-35.
7. McClintic SM, et al. Improvement in corneal scarring following bacterial keratitis. Eye. 2013;27(3):443-6.
8. Verma RP, Hansch C. Matrix metalloproteinases (MMPs): chemical-biological functions and (q)sars. Bioorg Med Chem. 2007;15(6):2223-68.
9. Solomon A, et al. Pro- and anti-inflammatory forms of interleukin-1 in the tear fluid and conjunctiva of patients with dry-eye disesase. IOVS. 2001;42(10):2283-92.
10. Sambrusky R, et al. Sensitivity and specificity of a point-of-care matrix metalloproteinase 9 immunoassay for diagnosing inflammation related to dry eye. JAMA Ophthalmol. 2013;131(1):24-8.
11. Chotikavanich S, et al. Production and activity of matrix metalloproteinase-9 on the ocular surface increase in dysfunctional tear syndrome. IOVS. 2009;50(7):3203-09.
12. www.rpsdetectors.com/in/products/about/product-information accessed 4/12/2014.