Accelerated high fluence photoactivated chromophore for infectious keratitis-corneal cross-linking (PACK-CXL) at the slit lamp: a pilot study.

Introduction: Photoactivated Chromophore for Infectious Keratitis-Corneal Cross-Linking (PACK-CXL) has garnered substantial interest among researchers and ophthalmologists due to its high promise as a potential treatment for infectious keratitis. The aim of this study is to evaluate the efficacy and safety of high fluence PACK-CXL, using 10.0 J/cm2 (30 mW/cm2, 5 min, and 33 s) at the slit lamp. Methods: This prospective interventional, nonrandomized cohort study included 20 eyes of 20 patients with bacterial, fungal, or mixed origin keratitis who underwent high fluence PACK-CXL treatment as an adjunct therapy to conventional antimicrobial therapy per American Academy of Ophthalmology treatment guidelines. The re-epithelization time was recorded, and corneal endothelial cell density was counted before and after treatment. Results: The average re-epithelization time was 8.2 ± 2.8 days (range 3-14 days). After PACK-CXL treatment, eight patients (40%) were directly discharged, while the remained patients stayed in the hospital for an average of 5.6 ± 3.5 days. No eyes required keratoplasty. Endothelial cell density counts before and after the PACK-CXL procedure were 2,562.1 ± 397.3, and 2,564.8 ± 404.5 cells/mm2, respectively (p = 0.96). Conclusion: although it was not a randomized control trial, we conclude that high fluence PACK-CXL as an adjuvant therapy is safe with no complications observed, and efficient as time to re-epithelization was less than 14 days for all patients and no patients underwent tectonic keratoplasties. Further research is needed to compare it to the current standard of care.

The Antibacterial Efficacy of High-Fluence PACK Cross-Linking Can Be Accelerated.

Purpose: To determine whether high-fluence photoactivated chromophore for keratitis cross-linking (PACK-CXL) can be accelerated. Methods: Solutions of Staphylococcus aureus and Pseudomonas aeruginosa with 0.1% riboflavin were prepared and exposed to 365 nm ultraviolet (UV)-A irradiation of intensities and fluences from 9 to 30 mW/cm2 and from 5.4 to 15.0 J/cm2, respectively, representing nine different accelerated PACK-CXL protocols. Irradiated solutions and unirradiated controls were diluted, plated, and inoculated on agar plates so that the bacterial killing ratios (BKR) could be calculated. Additionally, strains of Achromobacter xylosoxidans, Staphylococcus epidermidis, and Stenotrophomonas maltophilia were exposed to a single accelerated PACK-CXL protocol (intensity: 30 mW/cm2, total fluence: 15.0 J/cm2). Results: With total fluences of 5.4, 10.0, and 15.0 J/cm2, the range of mean BKR for S. aureus was 45.78% to 50.91%, 84.13% to 88.16%, and 97.50% to 99.90%, respectively; the mean BKR for P. aeruginosa was 69.09% to 70.86%, 75.37% to 77.93%, and 82.27% to 91.44%, respectively. The mean BKR was 41.97% for A. xylosoxidans, 65.38% for S. epidermidis, and 78.04% for S. maltophilia for the accelerated PACK-CXL protocol (30 mW/cm2, 15 J/cm2). Conclusions: The BKR of high-fluence PACK-CXL protocols can be accelerated while maintaining a high, but species-dependent, BKR. The Bunsen to Roscoe law is respected in fluences up to 10 J/cm2 in S. aureus and P. aeruginosa, whereas fluences above 10 J/cm2 show strain dependence. Translational Relevance: The high-fluence PACK-CXL protocols can be accelerated in clinical practice while maintaining high levels of BKR.

Corneal Cross-Linking: Epi-On.

ABSTRACT: When treating corneal ectasias, successful corneal cross-linking (CXL) requires three factors: riboflavin saturation of the corneal stroma, ultraviolet (UV) light, and oxygen. Riboflavin is too large to pass through epithelial tight junctions, so traditionally epithelial debridement is performed before riboflavin is applied making this approach an epithelium-off (epi-off) technique. However, this can result in pain as the epithelium regrows, corneal haze, and an increased infection risk postoperatively, which needs careful management with pharmacotherapy. Epithelium-on (epi-on) CXL should reduce the extent of these issues. Riboflavin can be passed through the epithelium into the stroma either by iontophoresis or with penetration enhancers, however this alone results in suboptimal cross-linking effects, as the epithelium not only absorbs around 20% of incoming UV energy, it also acts as a barrier to oxygen diffusion into the stroma. While it is simple to adjust the UV fluence delivered to the stroma to compensate for the energy lost in the epithelium, compensating for the lack of stromal oxygen is less simple. Several approaches (including oxygen goggles) have been taken to achieve this. However, adding iontophoresis and supplemental oxygen through goggles in the operating theater adds complexities that could be engineered out. Accordingly, the technique has advanced in the laboratory to a point where penetration enhancers, optimized UV irradiation profiles, and atmospheric oxygen can now provide epi-on CXL with the same corneal strengthening efficacy as epi-off CXL, suggesting simple, effective epi-on CXL could soon be in clinical use.

Transepithelial Enhanced Fluence Pulsed Light M Accelerated Crosslinking for Early Progressive Keratoconus with Chemically Enhanced Riboflavin Solutions and Air Room Oxygen.

PURPOSE: To assess the 3-year clinical results of the 18 mW 7 J/cm2 transepithelial enhanced fluence pulsed light M accelerated crosslinking in the treatment of progressive keratoconus (KC) with chemically enhanced hyper-concentrated riboflavin solutions without iontophoresis and with air-room oxygenation. SETTING: Siena Crosslinking Center, Siena, Italy. METHODS: Prospective pilot, open non-randomized interventional study including 40 eyes of 30 young adult patients over 21 years old (10 simultaneous bilateral) with early (Stage I and II) progressive KC undergoing TE-EFPL 18 mW/7 J/cm2 ACXL (EFPL M TECXL). The 12 min and 58 s pulsed light (1 s on/1 s off) UV-A exposure treatments were performed with a biphasic corneal soaking using Paracel I 0.25% for 4 min and Paracel II 0.22% for 6 min riboflavin solutions and New KXL I UV-A emitter (Glaukos-Avedro, Waltham, USA) at an air room of 21% oxygenation. All patients completed the 3-year follow-up. RESULTS: CDVA showed a statistically significant improvement in the third postoperative month (Δ + 0.17 d. e.) with a final gain of +0.22 d. eq. AK showed a statistically significant decrease in the sixth postoperative month (Δ - 1.15 diopters). K itmax showed a statistically significant decrease at 1-year follow-up (Δ - 1.3 diopters). The coma value improved significantly by the sixth month (Δ - 0.54 µm). MCT remained stable during the entire follow-up. No adverse events were recorded. Corneal OCT revealed a mean demarcation line depth at 282.6 ± 23.6 µm. CONCLUSIONS: Transepithelial enhanced fluence pulsed light M accelerated crosslinking with chemically enhanced riboflavin solution halted KC progression in young adult patients without iontophoresis and no intraoperative oxygen supplementation addressing the importance of increased fluence.

PACK Cross-Linking as Adjuvant Therapy Improves Clinical Outcomes in Culture-Confirmed Bacterial Keratitis.

PURPOSE: We recently showed the positive clinical effects of combining accelerated corneal cross-linking (PACK-CXL) with antibiotic treatment in patients with presumed bacterial keratitis. In this study, we compare the impacts of a combined PACK-CXL/standard antibiotic treatment (PACK-ABX group) with standard antibiotic treatment alone (ABX group) in patients with culture-confirmed bacterial keratitis. METHODS: We reviewed patients with moderate and severe bacterial keratitis and confirmed bacterial cultures. Clinical outcomes were compared for standard antibiotic treatment alone, before the initiation of PACK-CXL, and after adjuvant use of PACK-CXL. RESULTS: A total of 47 eyes of 47 patients were included: 26 eyes in the PACK-ABX group and 21 eyes in the ABX group. Pathogens, baseline demographics (besides age), and clinical parameters were similar between the 2 groups. The PACK-ABX patients had better final uncorrected visual acuity [mean difference 0.57 Logarithm of the Minimum Angle of Resolution, 95% Confidence Interval (CI): 0.16-0.99, P = 0.07] and best-corrected visual acuity (mean difference 0.70 Logarithm of the Minimum Angle of Resolution, 95% CI: 0.23-1.16, P = 0.04), shorter reepithelialization time (mean difference 9.63 days, 95% CI: 3.14-16.12, P = 0.004), and reduced number of clinic visits (mean difference 4.8 meetings, 95% CI: 1.4-8.2, P = 0.007) and need for tectonic grafts (0 vs. 33.3%, P = 0.002). A multivariate analysis controlling for age, sex, ulcer size, and Gram stain showed that PACK-ABX treatment remained significantly associated with reepithelialization time (ß = 14.5, P = 0.001). CONCLUSIONS: In our study, PACK-CXLs addition to the standard of care in cases of culture-proven bacterial keratitis had a positive effect on the final visual acuity and time to resolution, compared with the standard-of-care treatment.

High-Fluence Accelerated Epithelium-Off Corneal Cross-Linking Protocol Provides Dresden Protocol-Like Corneal Strengthening.

Purpose: To assess whether optimized technical settings for accelerated epithelium-off corneal cross-linking may lead to increases in biomechanical stiffness similar to the benchmark 30-minute epithelium-off Dresden protocol. Methods: Three-hundred porcine eyes were divided equally into six groups for analysis. All samples underwent epithelial debridement and soaking with 0.1% iso-osmolar riboflavin solution for 20 minutes. Corneal cross-linking (CXL) was performed using epithelium-off protocols varying in acceleration and total fluence (intensity in mW/cm² * time in minutes, total fluence in J/cm²): standard (S)-CXL (3*30, 5.4), accelerated (A)-CXL (9*10, 5.4), A-CXL (9*13'20″, 7.2), A-CXL (18*6'40″, 7.2), and A-CXL (18*9'15″, 10). Control corneas were not irradiated. The elastic modulus of 5-mm wide corneal strips was measured as an indicator of corneal stiffness. Results: All irradiated groups had significantly higher elastic modulus than controls (P < 0.05), with a stiffening effect of 133% S-CXL (3*30, 5.4), 122% A-CXL (9*10, 5.4), 120% A-CXL (9*13'20″, 7.2), 114% A-CXL (18*6'40″, 7.2) and 149% A-CXL (18*9'15″, 10). The high-fluence accelerated epithelium-off protocol (18*9'15″, 10) showed the highest stiffening effect. Elastic modulus at 5% strain (1%-5% strain) showed significant differences between A-CXL (18*9'15″, 7.2) and three other accelerated protocols: A-CXL (9*10, 5.4; P = 0.01), A-CXL (9*13'20″, 7.2; P = 0.003), and A-CXL (18*6'40″, 10; P = 0.0001). Conclusions: An accelerated high-fluence epithelium-off CXL protocol (18 mW/cm² for 9'15″) was identified to provide a significantly greater stiffening effect than any other accelerated protocols and is indistinguishable from the Dresden protocol, with accelerating irradiation times ranging from 30 to 9 minutes; by combining gentle acceleration with higher fluence, such a protocol does not require supplemental oxygen. Translational Relevance: This A-CXL (18*9'15″, 10) protocol has the potential to become a new standard in epithelium-off CXL, delivering Dresden protocol-like strengthening over a shorter period.

Corneal Cross-Linking: The Evolution of Treatment for Corneal Diseases.

Corneal cross-linking (CXL) using riboflavin and ultraviolet A (UVA) light has become a useful treatment option for not only corneal ectasias, such as keratoconus, but also a number of other corneal diseases. Riboflavin is a photoactivated chromophore that plays an integral role in facilitating collagen crosslinking. Modifications to its formulation and administration have been proposed to overcome shortcomings of the original epithelium-off Dresden CXL protocol and increase its applicability across various clinical scenarios. Hypoosmolar riboflavin formulations have been used to artificially thicken thin corneas prior to cross-linking to mitigate safety concerns regarding the corneal endothelium, whereas hyperosmolar formulations have been used to reduce corneal oedema when treating bullous keratopathy. Transepithelial protocols incorporate supplementary topical medications such as tetracaine, benzalkonium chloride, ethylenediaminetetraacetic acid and trometamol to disrupt the corneal epithelium and improve corneal penetration of riboflavin. Further assistive techniques include use of iontophoresis and other wearable adjuncts to facilitate epithelium-on riboflavin administration. Recent advances include, Photoactivated Chromophore for Keratitis-Corneal Cross-linking (PACK-CXL) for treatment of infectious keratitis, customised protocols (CurV) utilising riboflavin coupled with customised UVA shapes to induce targeted stiffening have further induced interest in the field. This review aims to examine the latest advances in riboflavin and UVA administration, and their efficacy and safety in treating a range of corneal diseases. With such diverse riboflavin delivery options, CXL is well primed to complement the armamentarium of therapeutic options available for the treatment of a variety of corneal diseases.

Comparison of eye-rubbing effect in keratoconic eyes and healthy eyes using Scheimpflug analysis and a dynamic bidirectional applanation device.

PURPOSE: To compare the effect of eye rubbing on Scheimpflug imaging parameters and corneal biomechanics in eyes with keratoconus and healthy eyes. SETTING: Oftalmosalud Instituto de Ojos, Lima, Peru. DESIGN: Prospective cohort study. METHODS: The study included healthy and keratoconus patients who attended the institution between January 2017 and July 2017. Eye rubbing was performed for 1 minute followed by a 5-second break, followed by further rubbing for 1 minute. Baseline tests were performed before rubbing; post-rubbing tests were performed immediately after (0 minutes), and then again at 7 minutes and 14 minutes. Parameters related to anterior and posterior curvature and elevation, pachymetry, and corneal biomechanics obtained from tomography with a rotating Scheimpflug camera (Pentacam HR) and a dynamic bidirectional applanation device (Ocular Response Analyzer) were measured and compared between healthy and keratoconic eyes. RESULTS: The study included 30 healthy eyes and 31 keratoconic eyes. In the healthy group, the immediate mean changes in steeper anterior keratometry, posterior astigmatism, anterior chamber volume (ACV), flattest posterior keratometry, and Goldmann-correlated intraocular pressure (IOPg) after eye rubbing were 0.07 diopters (D) ± 0.15 (SD), -0.01 ± 0.08 D, 0.03 ± 7.06 mm3, -0.001 ± 0.04 mm, and -1.21 ± 1.99 mm Hg, respectively, whereas the mean changes in the keratoconus group were -0.03 ± 0.32 D, 0.14 ± 0.50 D, -5.09 ± 8.45 mm3, 0.03 ± 0.06 mm, and -1.61 ± 1.41 mm Hg, respectively. There were statistically significant differences between the preoperative and postoperative eye-rubbing values of posterior astigmatism, ACV, and IOPg in the keratoconus group (P = .03, P = .0003, and P = .001, respectively) but not in the healthy group (P = .65, P = .85, and P = .23, respectively). CONCLUSIONS: Unlike the healthy eyes group, the keratoconus group experienced significant changes in ACV, IOP, and corneal posterior astigmatism after eye rubbing.

Collagen cross-linking with photoactivated riboflavin (PACK-CXL) for the treatment of advanced infectious keratitis with corneal melting.

PURPOSE: To investigate the efficacy and safety of corneal collagen cross-linking (CXL) with photoactivated riboflavin (photoactivated chromophore for infectious keratitis [PACK]-CXL) in the management of infectious keratitis with corneal melting. DESIGN: Prospective clinical trial. PARTICIPANTS: Forty eyes from 40 patients with advanced infectious keratitis and coexisting corneal melting. METHODS: Twenty-one patients (21 eyes) underwent PACK-CXL treatment in addition to antimicrobial therapy. The control group consisted of 19 patients (19 eyes) who received only antimicrobial therapy. MAIN OUTCOME MEASURES: The slit-lamp characteristics of the corneal ulceration, corrected distance visual acuity, duration until healing, and complications were documented in each group. The Mann-Whitney U test was used for statistical analysis. P values less than 0.05 were considered statistically significant. RESULTS: The average time until healing was 39.76 ± 18.22 days in the PACK-CXL group and 46.05 ± 27.44 days in the control group (P = 0.68). After treatment and healing, corrected distance visual acuity was 1.64 ± 0.62 in the PACK-CXL group and 1.67 ± 0.48 in the control group (P = 0.68). The corneal ulceration's width and length was significantly bigger in the PACK-CXL group (P = 0.004 and P = 0.007). Three patients in the control group demonstrated corneal perforation; infection recurred in 1 of them. No serious complications occurred in the PACK-CXL group. CONCLUSIONS: Corneal CXL with photoactivated riboflavin did not shorten the time to corneal healing; however, the complication rate was 21% in the control group, whereas there was no incidence of corneal perforation or recurrence of the infection in the PACK-CXL group. These results indicate that PACK-CXL may be an effective adjuvant therapy in the management of severe infectious keratitis associated with corneal melting.

The Biomechanical Effect of Corneal Collagen Cross-Linking (CXL) With Riboflavin and UV-A is Oxygen Dependent.

PURPOSE: In an attempt to reduce treatment time in corneal collagen cross-linking (CXL) with riboflavin and ultraviolet-A (UV-A), recent protocol modifications include shorter irradiation times at higher fluence, while maintaining constant total applied energy (Bunsen-Roscoe law of reciprocity). While such parameter changes might produce similar biological results within a certain range, the limits of reciprocity are unknown. Limitations in the corneal oxygen diffusion capacity and its potential impact on the efficacy of CXL, raise concerns regarding the efficiency of high-fluence CXL, and also of transepithelial CXL. METHODS: Porcine corneas were treated with an epithelium-off CXL at a fluence of 9 mW/cm2 under two different atmospheres: one with a regular oxygen content (21%) and another in a helium-supplemented, low-oxygen environment (<0.1%). Untreated corneas served as controls (n = 20 each). Five-millimeter corneal stripes were prepared and biomechanical stiffness was measured using an extensometer. RESULTS: Corneas cross-linked under normal oxygen levels showed a significant increase in biomechanical stability (14.36 MPa ± 2.69 SD), whereas corneas treated similarly, but in a low-oxygen atmosphere showed a Young's modulus similar to untreated controls (11.72 MPa ± 2.77 SD). CONCLUSIONS: The biomechanical effect of CXL seems to be oxygen dependent. This dependency will be of particular importance in high-fluence and transepithelial CXL and will most likely require major protocol modifications to maintain the efficiency of the method. TRANSLATIONAL RELEVANCE: The oxygen dependency of CXL shown here raises concerns about the effectiveness of high-fluence and transepithelial CXL. Both methods were introduced to clinical ophthalmology without thorough validation.

Actinidia deliciosa (kiwifruit), a new drug for enzymatic debridement of acute burn wounds.

BACKGROUND: Actinidia deliciosa (kiwifruit) is used as a meat tenderizer. It acts rapidly and efficiently to soften meat, liquefying it if allowed to work for more than a few hours. Observing this effect and the lack of studies addressing this subject in the literature, the authors sought to investigate the use of this natural remedy in an animal model for eschar separation and debridement. METHODS: Thirty-five male rats were divided randomly into three groups. Under general anaesthesia, a limited standard full-thickness burn was produced on the back of each rat. For the intervention group (G1, 15 rats), the wounds were covered with fresh kiwifruit; for control groups 2 and 3 (G2, 15 rats; G3, five rats), the dressing was a neutral ointment (Emulsifier 1220). Weekly wound observations were documented for all the groups. G1 and G2 were sacrificed on Day 20, and group 3 was kept alive until complete eschar separation. The wounds of the rats in groups 1 and 2 were excised and subjected to microscopic evaluation. RESULTS: On Day 20, all eschars had detached and fallen off in the intervention group (G1), whereas in groups G2 and G3 the eschars were still firmly attached to the base of the wounds (except in two rats of G2); this finding was statistically significant (p<0.001). The average wound surface area in group G1 was 212 mm(2) (SD=88.80938) whereas in G2 it was 388 mm(2) (SD=140.6967). Thus, the wound surface area was significantly (p<0.001) smaller in the intervention group. The eschars in G3 separated spontaneously between days 30 and 42, while in all the rats of the kiwi-treated group, this phenomenon occurred before Day 20. The pathological study revealed no considerable differences between G1 and G2 (p<0.05). CONCLUSIONS: Debridement and scar contraction occurred faster in the kiwi-treated group than in the untreated group. Following rapid enzymatic debridement, healing appeared to progress normally, with no evidence of damage to adjacent healthy tissue.

Ultra B2 - Promoção de ligações covalentes do colágeno corneal (Corneal cross-linking) no tratamento de ceratocone: resultados preliminares / Corneal Cross-linking for the treatment of keratoconus: preliminary results

OBJETIVO: Apresentar os resultados visuais e ceratométricos, seis meses após tratamento foto-terapêutico com luz ultravioleta (UV) e vitamina B2 (Ultra B2), em pacientes com ceratocone progressivo. MÉTODOS: Vinte e cinco olhos de 20 pacientes (15 homens e 5 mulheres) com ceratocone progressivo, determinado pelo aumento de curvatura em exames seriados de topografia corneal, nos últimos seis meses foram avaliados. Acuidade visual não corrigida (UVA), acuidade visual melhor corrigida com óculos (BSCVA), equivalente esférico (SEQ), cilindro refrativo manifesto e a curvatura máxima (max K) pré e pós-operatórios (1, 3 e 6 meses) foram determinadas. Todos os pacientes foram submetidos ao tratamento Ultra B2 usando riboflavina (vitamina B2) e a luz ultravioleta (UV, 370 nm). O epitélio corneal foi removido após assepsia, colocação de blefarostato e anestesia tópica com proparacaína, por meio de solução de álcool hidratado (20 por cento) utilizada por 30 segundos. A córnea foi saturada com vitamina B2 por 15 minutos; em seguida, foi irradiada por luz UV por 30 minutos. Ao final do procedimento, foi colocada lente de contato terapêutica (LCT), mantida até a epitelização total. RESULTADOS: Houve melhora na UVA após o primeiro mês (de 0,15 ± 0,15 para 0,23 ± 0,20), com contínua mudança no terceiro e sexto mês pós-operatório, atingindo a diferença estatisticamente significante nesse período (p=0,025 e p=0,037 respectivamente). BSCVA melhorou de 0,41 ± 0,27 para 0,49 ± 0,29 no sexto mês, sem atingir a diferença estatisticamente significante. A progressão do ceratocone após o procedimento não foi notada em nenhum paciente, em comparação com o avanço topográfico nos 6 meses precedentes. Após 6 meses do procedimento, max K diminuiu em mais que 2,00 D (de 53,02 ± 8,42 para 50,88 ± 6,05 D), SEQ em menos que 1 D (de -3,27 ± 4,08 para -2,68 ± 3,02 D) e o cilindro refrativo em menos que 0,5 D (de -2,29 ± 1,77 para -1,86 ± 0,92), sem atingir diferença estatisticamente...

PURPOSE: To present early visual and keratometric results for corneal cross-linking with riboflavin and UV irradiation in patients with progressive keratoconus. METHODS: Twenty-five eyes of twenty patients (15 males and 5 females) with a progressive keratoconus in the previous 6 months were followed. Unaided visual acuity (UVA), best spectacle corrected visual acuity (BSCVA), spherical equivalent (SEQ), manifest cylinder, and maximal corneal curvature (max K) values were followed at 1, 3 and 6 months. All patients were submitted to corneal cross-linking using riboflavin (vitamin B2) as the photosensitizer and ultraviolet light (UV, wavelength 370 nm). Epithelium was removed with 20 percent alcohol, cornea was soaked with vitamin B2 for 15 min, and then irradiated with UV light for 30 min, after which a bandage contact lens (BCL) was placed. RESULTS: UVA increased after one month (from 0.15 ± 0.15 to 0.23 ± 0.20), and went on increasing at 3 and 6 months, reaching statistical significance (p=0.025 e p=0.037, respectively). BSCVA increased from 0.41 ± 0.27 to 0.49 ± 0.29 at month six, without reaching statistical significance at any time point. Progression of keratoconus stopped in all patients, in contrast with progression in all of them in the six-month period prior to the surgery. Max K decreased by more than 2 D (from 53.02 ± 8.42 to 50.88 ± 6.05 D), SEQ less that 1 D (from -3.27 ± 4.08 to -2.68 ± 3.02 D), while refractive cylinder decreased less than 0.5 D (from -2.29 ± 1.77 to -1.86 ± 0.92 D), without reaching a statistically significant difference. None of the eyes lost any line of BSCVA, 12 maintained the preoperative BSCVA, 7 gained one line, 5 gained two lines, and 1 patient gained three lines of BSCVA. CONCLUSIONS: Corneal cross-linking with riboflavin and UV light seems to be a safe (no loss of BSCVA) and effective (anatomical and optical properties maintained) procedure, which has shown to stop the progression of the keratoconus...