Experimental study on cryotherapy for fungal corneal ulcer

Recurrent Filamentous Fungal Keratitis Caused When the Primarily Selected Graft Diameter was Too Small

PURPOSE

To establish the importance of using a sufficiently large corneal graft in primary penetrating keratoplasty in order to prevent recurrence of fungal keratitis.

OBERSERVATIONS

A 58-year-old female patient underwent emergency penetrating keratoplasty (diameter 7.0 mm, double running suture) for therapy-resistant fungal keratitis (Fusarium solani) at an external eye clinic. Despite intensive antifungal therapy, new fungal infiltrates appeared in the host cornea after a few days. The patient was referred to our department for further treatment. On first presentation, circular infiltrates were seen around the corneal graft with anterior chamber involvement and therapy-resistant hypopyon. We performed an emergency penetrating repeat keratoplasty (diameter of 13.0 mm, 32 interrupted sutures) combined with anterior chamber lavage and intracameral and intrastromal drug injection.

CONCLUSION AND IMPORTANCE

Fungal keratitis sometimes has a frustrating clinical course. Therefore, early diagnosis with effective therapy initiation is of the utmost importance. In cases of penetrating keratoplasty, optimal planning and timing (before anterior chamber involvement) should be provided. Sufficient safety distance must be ensured in the choice of graft diameter, fixation with multiple interrupted sutures, and anterior chamber lavage, as well as intracameral and intrastromal drug administration. Incomplete excision carries a risk of recurrence and endophthalmitis in the course. Close postoperative control is necessary to detect early recurrences.

Possible Synergistic Role of Cryo-Alcohol Therapy in Infectious Scleritis-Scope and Rationale for Expanding Indications and Review of the Literature

PURPOSE

The purpose of this study was to highlight the use of topical ethanol as an adjunct to cryotherapy, termed cryo-alcohol therapy, in the management of fungal/acanthamoeba scleritis along with a review of the literature.

METHOD

Retrospective interventional case reports of fungal and acanthamoeba scleritis along with a review of the literature.

RESULTS

The patient with circumferential necrotic fungal scleritis resolved in 6 weeks achieving a best-corrected visual acuity (BCVA) of 20/20, and the patient with acanthamoeba scleritis is awaiting optical keratoplasty after complete resolution in 8 weeks. The literature review from January 1990 to December 2020 revealed BCVA >20/200 in 50% of the eyes with a mean time to resolution being 4.16 ± 2.13 months in fungal scleritis, with 27.02% and 75% of the eyes requiring evisceration in fungal and acanthamoeba scleritis, respectively.

CONCLUSIONS

Cryotherapy is a useful adjunct in managing refractory infectious scleritis, and its efficacy can be enhanced by combining the use of topical ethanol to aid in faster recovery and reduce visual morbidity.

Update on diagnosis and management of refractory corneal infections

Infectious keratitis is a medical emergency resulting in significant visual morbidity. Indiscriminate use of antimicrobials leading to the emergence of resistant or refractory microorganisms has further worsened the prognosis. Coexisting ocular surface diseases, delay in diagnosis due to inadequate microbiological sample, a slow-growing/virulent organism, or systemic immunosuppressive state all contribute to the refractory response of the ulcer. With improved understanding of these varied ocular and systemic factors contributing to the refractory nature of the microbes, role of biofilm formation and recent research on improving the bioavailability of drugs along with the development of alternative therapies have helped provide the required multidimensional approach to effectively diagnose and manage cases of refractory corneal ulcers and prevent corneal perforations or further dissemination of disease. In this review, we explore the current literature and future directions of the diagnosis and treatment of refractory keratitis.

Rabbit Fungal Keratitis Model of Fusarium solani Tested Against Three Commercially Available Antifungal Drugs

The purpose of this study was to develop a reproducible preclinical Fusarium solani keratitis model, which would allow comparative testing of currently available antifungals (NATACYN [Alcon, Fort Worth, TX], voriconazole 1%, and amphotericin B 0.1%) as well as efficacy testing of new antifungals for translation into clinical practice in the future.

Comparison of modified corneal cross-linking with intrastromal voriconazole for the treatment of fungal corneal ulcer

The present study aimed to evaluate the efficacy of modified corneal cross-linking (CXL) for the treatment of fungal corneal ulcers compared with that following intrastromal voriconazole injection. In total, 31 patients with fungal corneal ulcers treated at The General Hospital of Northern Theater Command between October 2017 and October 2019 were enrolled. Among them, 10 eyes were treated with ultraviolet A (UV-A)/riboflavin CXL (CXL group), whilst 21 eyes were treated with debridement combined with intrastromal voriconazole (stromal injection group). Preoperative microbiological examination was performed in both groups, and evaluated using Fisher's exact test. Postoperatively, infection control and total efficacy rates, localized lesion, ulcer healing rate 1 week after surgery, visual acuity and complications were evaluated using Fisher's exact test, however visual acuity was analyzed by mixed-model ANOVA. The results showed that the pre-operative species distribution between the CXL and stromal injection groups did not significantly differ. The infection control rate in the CXL group was notably higher compared with that in the stromal injection group (P=0.04). Furthermore, the total efficacy rate in the CXL group was also markedly higher compared with that in the stromal injection group, though no statistically significant differences were observed. Localized lesions were observed in nine eyes (90.0%) in the CXL group and nine eyes (42.9%) in the stromal injection group (P=0.02). However, the rate of ulcer healing at 1 week postoperatively and the logarithm of the minimum angle of resolution (logMAR) of visual acuity were not found to be significantly different between the two groups. In terms of complications, with the exception of one patient in the CXL group exhibiting loss of corneal transparency and one patient in the stromal injection group presenting with partial corneal thinning, no other forms of complications were observed. In conclusion, the present study suggested that CXL could have a beneficial impact for treating fungal corneal ulcers in the aspects of infection control, localized lesions and accelerated epithelialization. In addition, except the loss of corneal transparency, this treatment approach could be applied with reduced risks of adverse events.

Successful Treatment of Refractory Candidal Granuloma by Itraconazole and Terbinafine in Combination with Hyperthermia and Cryotherapy

Candidal granuloma is a rare and refractory disease in clinical practice, usually reported in immunocompromised patients. We report a 57-year-old man who presented with candidal granuloma caused by Candida tropicalis. The diagnosis was confirmed according to histopathology and molecular identification. Prolonged duration of initial antifungal therapy did not obtain satisfactory improvement. Finally, the refractory disease was successfully treated by itraconazole and terbinafine in combination with hyperthermia and cryotherapy. The "blackish-red dot" dermoscopic sign of the verrucous granuloma gradually resolved during the treatment.

Experimental Models for Fungal Keratitis: An Overview of Principles and Protocols

Fungal keratitis is a potentially blinding infection of the cornea that afflicts diverse patient populations worldwide. The development of better treatment options requires a more thorough understanding of both microbial and host determinants of pathology, and a spectrum of experimental models have been developed toward this end. In vivo (animal) models most accurately capture complex pathological outcomes, but protocols may be challenging to implement and vary widely across research groups. In vitro models allow for the molecular dissection of specific host cell–fungal interactions, but they do so without the appropriate environmental/structural context; ex vivo (corneal explant) models provide the benefits of intact corneal tissue, but they do not provide certain pathological features, such as inflammation. In this review, we endeavor to outline the key features of these experimental models as well as describe key technical variations that could impact study design and outcomes.

Reduced administration frequency for the treatment of fungal keratitis: a sustained natamycin release from a micellar solution

Background: Natamycin is the only topical ophthalmic antifungal drug approved by the Food and Drug Administration (FDA) of the United States, but has unsatisfactory factors such as high dosing frequency.Methods: We report the synthesis and preparation of self-assembled poly(ethylene glycol)-block-poly(glycidyl methacrylate) (PEG-b-PGMA) micelles. These nanoparticles exhibit sustained delivery of a hydrophobic natamycin by topical administration on eye due to the hydrolysable properties of PGMA segments of micelle. Hydrolysis of glycidyl groups within a physiologically relevant environment provides an additional driving force for drug release by generation of hydrophilic hydroxyl groups to 'push' the encapsulated hydrophobic drug away from the resultant hydrophilic domains and into surrounding environment.Results: In vitro and in vivo results revealed that the self-assembled micelles and the encapsulated natamycin were not cytotoxic and the released drug have strong antifungal ability to Candida albicans. Importantly, sustained natamycin release from micelles leads to the reduced administration frequency of natamycin from 8 times per day to 3 times per day in rabbits suffering from fungal keratitis (FK).Conclusion: This study demonstrates a facile method that can greatly reduce dosing frequency of natamycin administration and thus improve long-term patient compliance.

Can cryotherapy be used as an adjunct in select cases of recalcitrant endophthalmitis? - A case report

We report two cases of recalcitrant endophthalmitis, a delayed postoperative fungal endophthalmitis following cataract surgery and an atypical mycobacterial endogenous endophthalmitis associated with infective scleritis. Due to recalcitrant nature of the endophthalmitis, one or more sittings of double freeze and thaw cryotherapy was applied over and adjacent to the infective foci in each case. This cryotherapy was used as an adjunct alongside conventional endophthalmitis management following which resolution of infection was observed in both cases.

Clinical profile, risk factors and outcome of medical, surgical and adjunct interventions in patients with Pythium insidiosum keratitis

PURPOSE

To report clinical profile and compare management options for Pythium keratitis.

METHOD

Retrospective interventional study of 46 patients diagnosed as Pythium keratitis by PCR DNA sequencing from January 2014 to July 2017. Interventions were categorised into medical management (MM) (topical azithromycin and linezolid with oral azithromycin at presentation), surgery (S) (therapeutic penetrating keratoplasty, TPK), surgical adjunct (SA) (cryotherapy±alcohol with TPK) and medical adjunct (MA) (MM after TPK).

RESULTS

Primary treatment included MM (1 eye), SA (3 eyes) and S (42 eyes). Recurrence occurred in 27/43 eyes (MM+S group). Second surgery (S) was required in 11 eyes (TPK-2), with additional procedures (SA) in 10 eyes and evisceration in five eyes. 8/43 eyes received MA after TPK-1. One eye required TPK-3. Recurrence occured in all eyes that received MA (100%) and in 28 of 54 TPKs (51.8%) (TPK 1+2+3) in 42 eyes. Recurrence was noted in 1/14 (7.1%) that underwent SA.

CONCLUSION

The currently available and recommended treatment for Pythium keratitis is surgical by means of a TPK and in worse cases evisceration. In our study, MM/MA measures showed no benefit with recurrence or worsening of infection requiring resurgery. Almost 50% of TPKs had a recurrence requiring resurgery. However, adjunctive procedures during TPK appear to have additional benefit with low risk of recurrence and could be included as routine care.

Clinical profile of pythium keratitis: perioperative measures to reduce risk of recurrence

PURPOSE

To report the clinical profile and role of perioperative adjunctive measures to reduce the risk of recurrence in Pythium insidiosum keratitis.

METHODS

Retrospective analysis of 10 eyes of 10 patients with P. insidiosum keratitis. Diagnosis was confirmed by PCR DNA sequencing.

RESULTS

7out of 10 patients were from urban locales, and none had any obvious history of injury with vegetative matter and were being treated for fungal keratitis. 6 eyes presented with central full thickness infiltrates with subepithelial and superficial stromal infiltrates radiating in a reticular pattern. Corneal scraping in all eyes revealed sparsely septate fungal-like filaments on potassium hydroxide/Calcofluor. All eyes underwent the first therapeutic penetrating keratoplasty (TPK) based on worsening or non-responsiveness of clinical features to the antifungal regimen. Recurrence was noted in 7 out of 10 eyes of which 2 eyes underwent evisceration. Of the six eyes that underwent cryotherapy following confirmation of microbiological diagnosis of Pythium (along with primary TPK-1, with re-TPK-5), only one eye had a recurrence and had to be eviscerated. Of the two eyes that did not undergo cryotherapy during re-TPK, following microbiological diagnosis, one eye had a recurrence and had to be eviscerated. In two eyes with adjoining scleritis, the host bed was swabbed using absolute alcohol of which one eye was salvaged.

CONCLUSION

This series highlights the need to be aware of this entity in the management of refractory fungal keratitis. It also brings to fore the adjunctive measures that could have a beneficial role in the management of pythium keratitis.

Medical and surgical management of Pasteurella canis infectious keratitis

Introduction

We describe a case of refractory Pasteurella Canis keratitis that initially failed antimicrobial treatment but was successfully treated with a conjunctival flap followed by a penetrating keratoplasty.

Case discussion

A 70-year-old male had persistent corneal edema related to previous herpes zoster keratouveitis with visual acuity of 20/400. An endothelial keratoplasty was performed with improvement in vision to 20/25. Several months after this surgery the patient developed a corneal infiltrate and cultures grew Pasturella canis. The infection persisted despite topical treatment with broad spectrum fortified vancomycin, tobramycin and fluoroquinolones. A conjunctival flap combined with corneal cryotherapy was performed to help mitigate symptoms and to allow the ulcer to heal. A penetrating keratoplasty was done several months later.

Discussion

The patient achieved pain relief immediately after the flap was placed. Medications were tapered off in the following few months after the procedure. A penetrating keratoplasty was performed 4 months later. The patient has remained almost entirely symptom free, and the graft remained clear one year after surgery.

Conclusions

A keratitis caused by Pasteurella canis that is resistant to medical therapy can be treated successfully with a conjunctival flap and cryotherapy followed by a penetrating keratoplasty.

Excisional keratectomy combined with focal cryotherapy and amniotic membrane inlay for recalcitrant filamentary fungal keratitis: A retrospective comparative clinical data analysis

The aim of the present study was to investigate the efficacy of a novel surgical intervention, excisional keratectomy combined with focal cryotherapy and amniotic membrane inlay (EKCAI), for the treatment of recalcitrant filamentary fungal keratitis. A retrospective analysis was performed of patients who underwent excisional keratectomy combined with conjunctival flap inlay (EKCFI), EKCAI or therapeutic penetrating keratoplasty (TPK) from January 2006 to January 2011. Recalcitrance was determined as being unresponsive to standard medical antifungal therapy for at ≥1 week. Outcome measures among the three intervention modalities were compared. A total of 128 patients had a follow-up of ≥1 year after the primary intervention. The success rates of interventions at 1-year follow-up were 58.33% in the EKCFI group, 88.37% in the EKCAI group and 93.44% in the TPK group (P<0.0002). The preoperative visual acuity of the three groups were similar (P=0.6458), while the postoperative best-corrected visual acuity (BCVA) of patients without recurrence was significantly different among the three groups 3 months after surgery. The best postoperative BCVA was found in the TPK group, while the worst was in the EKCFI group. In conclusion, EKCAI does not require donor cornea, is straightforward surgically, and has a favorable success rate compared with EKCFI.