Microbial Keratitis After Corneal Collagen Cross-Linking for Corneal Ectasia

Epithelium-on versus epithelium-off corneal collagen crosslinking for keratoconus: a systematic review and meta-analysis

PURPOSE

Corneal collagen crosslinking (CXL) is the primary treatment for progressive keratoconus which has a significant impact on vision and quality of life. Our study aimed to compare the efficacy and safety of epithelium-on versus epithelium-off CXL to treat keratoconus.

METHODS

We searched PubMed, Medline, Embase, Web of Science, and Scopus databases. We included studies that compared standard epithelium-off with epithelium-on CXL. The primary outcome measures were changes in corrected distance visual acuity (CDVA) and maximum keratometry (Kmax), and the secondary outcomes were uncorrected distance visual acuity (UDVA), central corneal thickness (CCT), and adverse events. A meta-analysis was performed on the primary and secondary outcomes based on the weighted mean differences between baseline to 12-month follow-up.

RESULTS

The search retrieved 887 publications with 27 included in the systematic review. A total of 1622 eyes (1399 patients; age 25.51 ± 4.02 years) were included in comparisons of epithelium-off to epithelium-on CXL in keratoconus. Epithelium-off CXL treated 800 eyes and epithelium-on CXL for 822 eyes. At 12-month follow-up, CDVA and Kmax showed no significant difference between the epithelium-off and epithelium-on CXL. The secondary outcomes showed that UDVA was better in epithelium-off CXL (- 0.11D, 95% CI - 0.12, - 0.1; p < 0.001) and there was more thinning in CCT in epithelium-off CXL (- 3.23 μm, 95% CI - 4.64, - 1.81; p <0.001).

CONCLUSION

Epithelium-off and epithelium-on CXL were both effective to treat progressive keratoconus. Further research is needed to compare the long-term outcomes and safety of both CXL protocols for adaptation into clinical practice.

Diagnostic utility of in vivo confocal microscopy in Acanthamoeba keratitis following corneal crosslinking

Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening complication of corneal collagen crosslinking (CXL) for keratoconus. In this report, we describe an early adolescent male who underwent routine CXL for progressive keratoconus in his left eye. Preprocedural left visual acuity (VA) was 6/9. At day 5 postprocedure, multifocal corneal infiltrates were identified. Corneal scrape, bandage contact lens cultures and herpetic and Acanthamoeba PCR were negative. In vivo, confocal microscopy (IVCM) identified Acanthamoeba cysts within the corneal stroma. Intensive amoebicidal therapy was initiated, but recovery was complicated by significant inflammation, resulting in widespread aggressive corneal vascularisation necessitating topical steroids and steroid-sparing agents. At 10 months, his left VA was 6/24. This report emphasises the importance of maintaining a high index of suspicion for AK in cases of post-CXL microbial keratitis and highlights the diagnostic value of IVCM, particularly in culture-negative and PCR-negative cases.

A Case Series of Infectious Keratitis After Corneal Cross-linking

PURPOSE

To present the 7-year experience of a tertiary eye hospital while exploring possible risk factors and incidence of infectious keratitis in patients undergoing standard corneal cross-linking (CXL).

METHODS

This retrospective cohort study included patients with progressive keratoconus undergoing standard CXL in the Farabi Eye Hospital and all other patients who had undergone CXL in other facilities and were diagnosed as having infectious keratitis in the 7-year period of the study.

RESULTS

Among the total of 4,863 eyes that underwent CXL, 6 eyes developed infectious keratitis, yielding an incidence rate of 0.12%. Additionally, 13 eyes from 10 patients with a CXL history in other facilities who developed infectious keratitis were included. The mean age was 23.75 years, and 75% of patients were men and 25% were women. Gram-positive bacteria and Staphylococcus aureus were the most prevalent pathogens. Meibomian gland dysfunction, dry eye disease, or blepharitis were present in 12 patients. Medical treatment did not arrest the disease progress in 5 patients, which eventually required cases to undergo keratoplasty.

CONCLUSIONS

This study supports the need for proper patient selection by using a comprehensive medical history. It also highlights the imperative role of rigorous patient education and follow-up, particularly in the first postoperative week. Finally, the study emphasizes aggressive early therapy for patients with suspicious findings. [J Refract Surg. 2023;39(8):564-572.].

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Low-intensity low-frequency ultrasound mediates riboflavin delivery during corneal crosslinking

We employed the mechanical effect from 40 kHz ultrasound (US) to improve the delivery of riboflavin into corneal stroma for collagen crosslinking, which can benefit the treatment of keratoconus and other corneal ectasias. Experiments were conducted, first with porcine corneas ex vivo and then with New Zealand white rabbits in vivo, at varying mechanical index (MI) and sonication time. Results showed that 15 min of US applied on the cornea at MI = 0.8 in the presence of 0.5% of riboflavin solution enabled its delivery to deeper corneal stroma. Excessive heat was removed by a cooling setup to negate the thermal effect. The corneal absorption amount and penetration of riboflavin through cornea as detected by fluorotron, as well as the enhancement of corneal stiffness as measured by Young's modulus, were comparable to the conventional approach that requires complete corneal epithelium debridement. Histological analysis revealed minor exfoliation of superficial cell layers of corneal epithelium and loss of ZO-1 tight junctions immediately after US. Full recovery of the corneal epithelium and restoration of tight junctions occurred in 3-4 days. The study shows that low-intensity low-frequency ultrasound (LILF US) is a less invasive alternative to the conventional epithelium-off method for delivering riboflavin into the corneal stroma.

EpiSmart® Crosslinking for Keratoconus: A Phase 2 Study

PURPOSE

The aim of this study was to assess changes in visual acuity after epithelium-on ("epi-on") corneal crosslinking after a diagnosis of keratoconus.

METHODS

Subjects with corneal ectatic diseases were enrolled in a prospective, randomized, controlled, open-label, multicenter trial. Subjects were randomized to 1 of 3 treatment groups and treated with an epi-on crosslinking system including riboflavin/sodium iodide and pulsed UVA exposure (EpiSmart® , CXL Ophthalmics, Encinitas, CA). The UVA treatment groups were 2.4 J/cm2 over 20 minutes, 3.6 J/cm2 over 20 minutes, and 3.6 J/cm2 over 30 minutes. The primary end point was logarithm of the minimum angle of resolution corrected distance visual acuity (CDVA). Secondary end points were logarithm of the minimum angle of resolution uncorrected distance visual acuity (UCVA), maximum corneal curvature (Kmax), and minimum corneal thickness. Data were assessed 6 and 12 months post-operatively, using t-tests for differences from baseline.

RESULTS

Two thousand two hundred twenty-eight subjects were treated with epi-on crosslinking. One thousand nine hundred twenty-two subjects had a diagnosis of keratoconus; other treated eyes had postsurgical and other ectasias. At 6 and 12 months, the subjects with keratoconus demonstrated significant improvements in CDVA, UCVA, and Kmax; minimum corneal thickness was unchanged. One hundred ninety-five subjects (8.7%) reported at least 1 adverse event (AE). A mild corneal epithelial defect was reported in 31 cases (1.4%) and was the only AE reported in >1% of subjects. There were no serious AEs related to the treatment.

CONCLUSIONS

EpiSmart® epi-on crosslinking resulted in mean improvements in CDVA, UCVA, and Kmax at both 6 and 12 months and an excellent safety and efficacy profile in subjects with keratoconus, with few significant side effects. Differences between UVA treatment groups were not significant.

Corneal Crosslinking: Present and Future

Keratoconus is a progressive corneal thinning disorder that can lead to vision loss. In the last 2 decades, corneal crosslinking (CXL) has emerged as an effective method to halt the progression of keratoconus and reduce the number of patients requiring keratoplasty. The procedure has been adopted globally and has evolved to become a part of combination treatments to regularize the cornea and improve visual outcomes. CXL has even been extrapolated in managing other ocular pathologies such as progressive myopia, infectious keratitis, and bullous keratopathy. This review aims to summarize the current role of CXL in keratoconus and its alternative uses, and provide insights into future developments in this fast-developing field.

Review of the literature on the currently available evidence for the management of infectious keratitis with PACK-CXL

Infectious keratitis (IK) is one of the most common causes of monocular blindness worldwide, especially in developing countries and may account for 5.1%-32.3% of all indications for penetrating keratoplasty (PK). However, performing a therapeutic PK on a "hot eye" is associated with a higher incidence of IK recurrence and graft rejection. Standard treatment includes antimicrobials (ATM) and, once the causative pathogen has been identified, must be continued with targeted treatment, depending on antibiogram sensitivity. However, appearance of multiresistant strains to ATM is progressively increasing at an alarming rate. Besides that, the diversity of the causative microorganisms (bacteria, fungi, parasites, viruses) may hinder the clinical diagnosis and secondarily the proper treatment from the beginning. It is estimated that only 50% of eyes will have a good visual result if the correct therapy is delayed. All these factors make the identification of alternatives to ATM treatment of paramount importance. Due to the ATM properties of photoactivated chromophore (riboflavin, RB) and ultraviolet (UV) light of wavelength (λ) 200-400 nanometers (nm), used in multiple medical and non-medical applications for disinfection, photoactivated chromophore for corneal cross-linking (CXL) of IK (PACK-CXL), as an addition to the therapeutic arsenal for the management of IK has been proposed. It must be differentiated from CXL used for the management of progressive keratoconus (KC). The objective of this review is to update the available evidence on the efficacy and safety of PACK-CXL in IKs.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Clinical Characteristics and Outcomes of Fungal Keratitis in the United Kingdom 2011-2020: A 10-Year Study

Fungal keratitis (FK) is a serious ocular infection that often poses significant diagnostic and therapeutic dilemmas. This study aimed to examine the causes, clinical characteristics, outcomes, and prognostic factors of FK in the UK. All culture-positive and culture-negative presumed FK (with complete data) that presented to Queen’s Medical Centre, Nottingham, and the Queen Victoria Hospital, East Grinstead, between 2011 and 2020 were included. We included 117 patients (n = 117 eyes) with FK in this study. The mean age was 59.0 ± 19.6 years (range, 4–92 years) and 51.3% of patients were female. Fifty-three fungal isolates were identified from 52 (44.4%) culture-positive cases, with Candida spp. (33, 62.3%), Fusarium spp. (9, 17.0%), and Aspergillus spp. (5, 9.4%) being the most common organisms. Ocular surface disease (60, 51.3%), prior corneal surgery (44, 37.6%), and systemic immunosuppression (42, 35.9%) were the three most common risk factors. Hospitalisation for intensive treatment was required for 95 (81.2%) patients, with a duration of 18.9 ± 16.3 days. Sixty-six (56.4%) patients required additional surgical interventions for eradicating the infection. Emergency therapeutic/tectonic keratoplasty was performed in 29 (24.8%) cases, though 13 (44.8%) of them failed at final follow-up. The final corrected-distance-visual-acuity (CDVA) was 1.67 ± 1.08 logMAR. Multivariable logistic regression analyses demonstrated increased age, large infiltrate size (>3 mm), and poor presenting CDVA (<1.0 logMAR) as significant negative predictive factors for poor visual outcome (CDVA of <1.0 logMAR) and poor corneal healing (>60 days of healing time or occurrence of corneal perforation requiring emergency keratoplasty; all p < 0.05). In conclusion, FK represents a difficult-to-treat ocular infection that often results in poor visual outcomes, with a high need for surgical interventions. Innovative treatment strategies are urgently required to tackle this unmet need.