Pearls for management of Pseudomonas scleritis

Although just 5% to 10% of all scleritis cases are infectious, approximately 75% of those cases are caused by Pseudomonas aeruginosa. This bacterial infection leads to cell lysis and exotoxins that can cause stromal necrosis and inflammation, which can eventually lead to ischemia, necrosis and significant thinning of the sclera.^1,2

Dr. Zeba Syed

Patients with Pseudomonas scleritis typically present with decreased vision, severe eye pain, discharge and redness. The pain that patients experience can be more advanced or deeper than with other forms of ocular surface infection. Overall, Pseudomonas infection presents similarly to scleritis, but the aetiology is infectious.² Compared with noninfectious cases, infectious scleritis is often associated with longer resolution times and worse outcomes that can result in vision-threatening complications such as cataracts, glaucoma and endophthalmitis.¹

Prior ocular surgery or procedures—most commonly pterygium surgery—increase a patient’s risk of infection. Pterygium surgery can initiate scleral ischemia, especially if mitomycin-C is used, which can lead to infection even years after the procedure.^2,3 Other risk factors that can predispose patients to scleral infection are cataract surgery, intravitreal injections or any trauma to the eye. Patients who are receiving immunosuppressive therapy have an increased risk for infection.²

Comprehensive diagnosis and effective treatment

Diagnosis is based on clinical evaluation, and we often see an area of either necrosis or purulence of the sclera as well as an infiltrate in the sclera. The sclera is typically very inflamed and, in advanced cases, thinned to the point where one can see a bit of a brownish hue and underlying uveal tissue. We can typically identify and diagnose infectious scleritis based on examination, but to make the specific diagnosis of Pseudomonas scleritis, we need to take a culture. We will take a swab of the area and deliver it to the microbiology lab for confirmation.²

Once scleritis has been diagnosed, we deliver as much antibiotic therapy into the area as we can. Unlike corneal ulcers or keratitis, the issue with scleritis is that topical antibiotic drops cannot penetrate the sclera as effectively, so there is often a need for systemic antibiotics.

There are 3 main reasons for this. First, the scleral collagen fibres are very dense, so medications generally have difficulty permeating through. Second, the sclera is quite avascular, so it is a challenge for the body to deliver systemic antibiotics to the area. Third, P aeruginosa creates a biofilm to protect itself, which reduces its susceptibly to antibiotics. Surgery can overcome some of these challenges.¹

I usually start treatment with an oral fluoroquinolone such as ciprofloxacin or moxifloxacin in addition to topical fortified antibiotics, and I monitor the patient closely. I tell the patient to come back in the next day or two because Pseudomonas scleritis can go downhill quickly, eating through the sclera and making its way into the eye or vitreous, causing endophthalmitis; if this occurs, there is an extremely poor prognosis.

If necessary, I inject an antibiotic such as ceftazidime, subconjunctivally. If they become worse on topical, systemic and subconjunctival antibiotics, then I will admit my patient to an inpatient facility and monitor them even more closely. If they continue to worsen, I will bring them into the operating room and perform surgical debridement on the infected, necrotic tissue, which also helps increase antibiotic delivery to the area.

Clinical pearls: Benefits of CAM

Depending on how much debridement was performed and how thin the remaining area is, a cryopreserved amniotic membrane (CAM) patch or graft can be placed over the area. It helps to reduce inflammation and necrosis and has regenerative healing properties.

For patients who need surgery, I use either AmnioGraft or AmnioGuard. AmnioGraft is a sheet of amniotic tissue that can be sutured and molded into the shape I want to fill in the gap that remains after surgical debridement. AmnioGuard is a much thicker amniotic membrane tissue, which I use in patients who may have a deeper defect after surgery. I will often combine them, suturing AmnioGuard in place and using Amnio­Graft on top as a bandage and barrier.

Figure 1 is a 73-year-old man referred with scleritis secondary to Pseudomonas infection after pterygium surgery. He presented with significant scleral thinning with early uveal visibility. He was treated with surgical debridement followed by AmnioGuard and AmnioGraft placement.

Figure 2 is an early postoperative photo. This patient had excellent postoperative results after 3 months (see Figure 3).

For patients who do not require surgery, I use Prokera, which is a self-retaining amniotic membrane ring, and I slip it under the patient’s eyelids in the office. Prokera can be used on patients who have a nonhealing defect in the cornea or in patients with recent burn or chemical exposure. I do not use dehydrated amniotic membrane because Prokera is well tolerated and has excellent results.⁴

Earlier intervention can lead to better outcomes

Lastly, I want to emphasise the importance of performing surgery early on in patients with Pseudo­monas scleritis. Every surgeon will have a personal threshold at which they want to operate. I have experienced good results with operating earlier, and there has been less need for removal of the eye and less clinical deterioration.

Although there have not been many studies whose results demonstrate the benefits of earlier surgery, because of the rarity of this condition, data from small case reports and case series suggest that medical and surgical treatment combined can potentially lead to better visual results and faster resolution of infection, and reduce the need for removal of the eye as compared with medical therapy alone.^1,5-8 I encourage my colleagues to perform surgery sooner rather than later.

Zeba A. Syed, MD, graduated from Harvard Medical School and completed a fellowship in cornea and refractive surgery at Bascom Palmer Eye Institute. She is an assistant professor of ophthalmology at Sidney Kimmel Medical College at Thomas Jefferson University and is codirector of the cornea fellowship program at Wills Eye Hospital in Philadelphia, Pennsylvania, US. Dr Syed is a consultant and speaker for BioTissue.

References

1. Syed ZA, Rapuano CJ. Umbilical amnion and amniotic membrane transplantation for infectious scleritis and scleral melt: a case series. Am J Ophthalmol Case Rep. 2021;21:101013. doi:10.1016/j.ajoc.2021.101013

2. Moshirfar M, Ronquillo Y. Infectious scleritis. In: StatPearls. StatPearls Publishing; 2023-. Updated July 25, 2022. Accessed May 1, 2023. https://www.ncbi.nlm.nih.gov/books/NBK560818/

3. Siatiri H, Mirzaee-Rad N, Aggarwal S, Kheirkhah A. Combined tenonplasty and scleral graft for refractory Pseudomonas scleritis following pterygium removal with mitomycin C application. J Ophthalmic Vis Res. 2018;13(2):200-202. doi:10.4103/jovr.jovr_122_16

4. Jirsova K, Jones GLA. Amniotic membrane in ophthalmology: properties, preparation, storage and indications for grafting–a review. Cell Tissue Bank. 2017;18(2):193-204. doi:10.1007/s10561-017-9618-5

5. Tittler EH, Nguyen P, Rue KS, et al. Early surgical debridement in the management of infectious scleritis after pterygium excision. J Ophthalmic Inflamm Infect. 2012;2(2):81-87. doi:10.1007/s12348-012-0062-1

6. Lin CP, Shih MH, Tsai MC. Clinical experiences of infectious scleral ulceration: a complication of pterygium operation. Br J Ophthalmol. 1997;81(11):980-983. doi:10.1136/bjo.81.11.980

7. Ahmad S, Lopez M, Attala M. Interventions and outcomes in patients with infectious Pseudomonas scleritis: a 10-year perspective. Ocul Immunol Inflamm. 2019;27(3):499-506. doi:10.1080/09273948.2017.1372484

8. Huang FC, Huang SP, Tseng SH. Management of infectious scleritis after pterygium excision. Cornea. 2000;19(1):34-39. doi:10.1097/00003226-200001000-00008