Analysis of microbial keratitis incidence, isolates and in-vitro antimicrobial susceptibility in the East of England: a 6-year study.

BACKGROUND/OBJECTIVES: To report the incidence, microbiological profile and in-vitro antimicrobial susceptibilities of microbial keratitis (MK) in the East of England (EoE) over a 6-year period. SUBJECTS/METHODS: A retrospective study of patients diagnosed with MK who underwent corneal scraping at participating trusts, within the EoE, between 01/01/2015-01/07/2020. Analysis was performed on MK isolate profiles, in-vitro anti-microbial sensitivities and trends over time. RESULTS: The mean incidence of IK, in the EoE, was estimated at 6.96 per 100 000 population/year. 1071 corneal scrapes were analysed, 460 were culture positive (42.95%) of which 87.2% were bacteria (50.3% gram-positive and 49.7% gram-negative), 2.4% polymicrobial, 9.3% fungi and 1.1% acanthamoeba. The most common organisms were pseudomonas spp (29.57%). There was a non-statistically significant trend (NST) in increasing incidence of pseudomonas spp, staph aureus and serratia (p = 0.719, p = 0.615, and p = 0.099 respectively) and a declining NST in Fungi (p = 0.058). Susceptibilities in-vitro to, penicillin classes, fluoroquinolone and aminoglycosides were 76.7% and 89.4%, 79.2% and 97.2% and 95.4 and 96.1% to gram-positive and gram-negative bacteria respectively. Gram-negative organisms were increasingly resistant to cephalosporins with a 19.2% reduction in sensitivity over time. (p = 0.011). Ceftriaxone showed the greatest decrease in sensitivity of 41.67% (p = 0.006). CONCLUSION: In the EoE, MK is relatively prevalent though likely underestimated. Profiles are similar to other UK regions with the exception of a higher fungal and lower acanthamoeba incidence. Common first and second-line antimicrobial selection provides, on the whole, good coverage. Nevertheless, anti-microbial resistance, to cephalosporins, was observed so selection should be carefully considered when treating MK empirically.

Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements.

PURPOSE: The effect of ultraviolet (UV)-riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. METHODS: Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. RESULTS: For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P = 0.018, 2-tailed t-test). CONCLUSIONS: We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.

Donor cross-linking for keratoplasty: a laboratory evaluation.

PURPOSE: This laboratory-based investigation compares the topographic outcomes of conventional penetrating keratoplasty with that of a novel procedure in which donor corneas are cross-linked prior to keratoplasty. METHODS: Penetrating keratoplasty procedures with continuous running sutures were carried out in a porcine whole globe model. Sixty eyes were randomly paired as 'donor' and 'host' tissue before being assigned to one of two groups. In the cross-linked group, donor corneas underwent riboflavin/UVA cross-linking prior to being trephined and sutured to untreated hosts. In the conventional keratoplasty group, both host and donor corneas remained untreated prior to keratoplasty. Topographic and corneal wavefront measurements were performed following surgery, and technical aspects of the procedure evaluated. RESULTS: Mean keratometric astigmatism was significantly lower in the cross-linked donor group at 3.67D (SD 1.8 D), vs. 8.43 D (SD 2.4 D) in the conventional keratoplasty group (p < 0.005). Mean wavefront astigmatism was also significantly reduced in the cross-linked donor group 4.71 D (SD 2.1) vs. 8.29D (SD 3.6) in the conventional keratoplasty group (p < 0.005). Mean RMS higher order aberration was significantly lower in the cross-linked donor group at 1.79 um (SD 0.98), vs. 3.05 um (SD 1.9) in the conventional keratoplasty group (P = 0.02). Qualitative analysis revealed less tissue distortion at the graft-host junction in the cross-linked group. CONCLUSION: Cross-linking of donor corneas prior to keratoplasty reduces intraoperative induced astigmatism and aberrations in an animal model. Further studies are indicated to evaluate the implications of this potential modification of keratoplasty surgery.

Visual Outcomes and Graft Thickness in Microthin DSAEK--One-Year Results.

PURPOSE: To evaluate visual outcomes, endothelial graft thickness, and complications in microthin Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS: A prospective interventional cohort of 130 eyes of 114 consecutive patients underwent microthin DSAEK. Endothelial graft preparation included pachymetry-controlled stromal dehydration to reduce donor thickness between 550 and 530 µm by a custom airflow device, before a single-pass microkeratome dissection with a uniform cutting head of 350 µm to achieve microthin endothelial grafts (<130 µm). Data on visual acuity, graft thickness, endothelial cell loss, and complication rates were analyzed. RESULTS: Pachymetry-controlled donor preconditioning reduced donor thickness on average by 67 µm (range 0-186, SD 44.7) from 590 µm (range 485-806, SD 53) to 528 µm (range 480-620, SD 23), P < 0.01, and allowed graft preparation without any case of intraoperative graft loss or perforation. The resultant mean graft thickness was 94 µm (SD 25) intraoperatively, 94 µm (SD 26) at 1 month, and 90 µm (SD 19) at 12 months. Of note, 98.2% of eyes without significant visual comorbidity achieved best-corrected Snellen acuity of 6/9 or more at 12 months. There was a 35.8% and 41% reduction in endothelial cell density at 3 and 12 months, respectively. Postoperative graft detachment occurred in 5% of cases (1.7% in uncomplicated eyes). There was no graft loss during preparation, and none developed immune rejection during the study period. CONCLUSIONS: The microthin DSAEK procedure offers a simple and safe technique to prepare thin endothelial grafts with a low risk of graft wastage, low risk of postoperative detachment, and visual results that are comparable to those of other thin endothelial keratoplasty procedures.

Comparative evaluation of Comfilcon A and Senofilcon A bandage contact lenses after transepithelial photorefractive keratectomy.

PURPOSE: To evaluate and compare Comfilcon A and Senofilcon A silicone hydrogel contact lenses used as a therapeutic bandage following transepithelial excimer laser photorefractive keratectomy (PRK). METHODS: Patients undergoing transepithelial PRK for myopia were prospectively recruited. Included patients had a Comfilcon A silicone hydrogel lens inserted in one eye, with a Senofilcon A lens in the contralateral eye. Postoperative assessment of subjective pain, epithelial healing and visual recovery was at day 1, 3 and 7. Contact lens factors including centration, movement and deposits were assessed. RESULTS: 48 eyes of 24 patients were included in the study. Mean age was 31 years (SD 11) and mean refractive error -4.5 D (SD 1.8). Mean pain score at day 1 was significantly higher in the Comfilcon group at 4.6 (SD 2.7) vs. 1.5 (SD2.5) in the Senofilcon group (P<0.005). Mean time to healing was 3.17 days (SD 0.37) in the Comfilcon group, and 3.21 days (SD 0.4) in the Senofilcon group, with no difference in defect size. There was a pronounced central raphe in 1 eye in the Comfilcon group vs. 5 eyes in the Senofilcon group (P=0.19). Significantly more eyes demonstrated no lens movement in the Senofilcon group (18 vs. 4, P=0.0001). CONCLUSION: The variation in material characteristics and lens geometry of different silicone hydrogel lenses affects their clinical characteristics in therapeutic roles. Other factors than oxygen permeability may affect pain and epithelial healing, with superior pain relief from the less permeable Senofilcon lens in this study.

Single-step transepithelial ASLA (SCHWIND) with mitomycin-C for the correction of high myopia: long term follow-up.

PURPOSE: We wanted to compare the outcomes of single-step modified transepithelial photorefractive keratectomy (tPRK) termed a SCHWIND all surface laser ablation (ASLA) versus conventional alcohol-assisted photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) for the correction of higher myopia of 6.00 diopters (D) or more, in an area with high risk of haze due to high intensity of sunlight. METHODS: We used a prospective interventional cohort with matched retrospective control groups. Patients with >6 D myopia and <3.5 D of astigmatism were included. All treatments were performed with the SCHWIND Amaris system using aspheric ablation profiles. Mitomycin C was used in all PRK and ASLA cases. Outcomes were postoperative refraction, visual acuity, stability, and complications. The follow-up period was up to 12 months. RESULTS: In total, 101 eyes were included after exclusions. Mean preoperative spherical equivalent refraction was -7.9 D, -8.2 D, and -7.4 D in the ASLA (n=41), PRK (n=29), and LASIK (n=31) groups. Mean postoperative spherical equivalent at 12 months postoperatively was -0.1 (standard deviation [SD]: 0.34), -0.2 (SD: 0.59), and -0.08 (SD: 0.36) in the ASLA, PRK, and LASIK groups, with 91.4%, 85.7%, and 83.9% within 0.5 D of target, respectively. Refractive outcomes and regression at 12 months did not vary among groups (P>0.05). Mean logMAR (logarithm of the minimum angle of resolution) uncorrected distance visual acuity at 12 months was 0.00 (SD: 0.05), 0.06 (SD: 0.1), and 0.05 (SD: 0.09) in the ASLA, PRK, and LASIK groups, with significantly better vision in the tPRK group versus LASIK (P=0.01) and PRK (P=0.01) groups. CONCLUSION: ASLA (SCHWIND) tPRK with mitomycin C for high myopia demonstrates comparable refractive outcomes to LASIK and PRK, with relatively favorable visual acuity outcomes. There was no increased incidence of haze in the ASLA group.

Transepithelial photorefractive keratectomy with crosslinking for keratoconus.

PURPOSE: To analyse visual, refractive and topographic outcomes of combining transepithelial photorefractive keratectomy (tPRK) with simultaneous corneal crosslinking for the visual rehabilitation of contact lens intolerant keratoconus patients. METHODS: Patients with topographically significant keratoconus, limited corrected vision and intolerant of contact lenses were prospectively recruited, subject to ethical approval and consent. All patients underwent single step aspheric tPRK and sequential crosslinking. Preoperative vision, refraction, corneal topography and wavefront were assessed, with postoperative assessment at 1, 3, 6, and 12 months. RESULTS: 22 eyes of 14 patients were included in the pilot study. Mean age was 32 years (SD 6.8, range 24 to 43). Mean preoperative unaided vision was 1.39 LogMAR (SD 0.5) best corrected 0.31 LogMAR (SD 0.2). Mean preoperative spherical equivalent was -2.74 Diopters (D) (SD 4.1 range -12.25 to +7.75), and mean cylinder -2.9 D (SD 1.2, range 0 to -5.5). Mean central corneal thickness was 461um (SD 29, range 411 to 516). Vision improved postoperatively; unaided 0.32 LogMAR (SD 0.4), best corrected 0.11 (SD 0.13) (P=<0.005). Mean postoperative cylinder was -1.4D (SD1.2), significantly reduced (p<0.005). Maximum keratometry (Kmax) was stable throughout postoperative follow up. (p<0.05). CONCLUSIONS: Non topographic transepithelial PRK with simultaneous crosslinking improves vision, and may offer an alternative to keratoplasty in contact lens intolerant keratoconus. Further comparative studies to topographic PRK techniques are indicated.

Preconditioned donor corneal thickness for microthin endothelial keratoplasty.

PURPOSE: To describe a novel surgical technique to produce thin endothelial grafts for Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS: Thirteen human cadaveric corneas in organ culture were randomized into conventional (n = 7) and microthin (n = 6) DSAEK groups. Grafts in the conventional DSAEK group were prepared using the conventional DSAEK technique of a single microkeratome pass with a 350-µm cutting head. Corneas in the microthin group were preconditioned to achieve a target central thickness of 530 µm before graft dissection with a 350-µm microkeratome head. Preconditioning involved stromal dehydration under pachymetric control using sterile airflow for 15-second increments. Donor and graft thicknesses were assessed with optical coherence tomography, and endothelial viability with trypan blue and alizarin red staining. RESULTS: Mean endothelial graft thickness obtained using the microthin DSAEK technique was 106 µm (SD, 32 µm) compared with 177 µm (SD, 33 µm) obtained using conventional DSAEK technique (P = 0.0024). Donor preconditioning yielded a predicted reduction of 100 µm in graft stromal thickness at a rate of 1.5 µm/s and mean duration of 72 seconds. The average anterior lamella thickness (cut depth) obtained in microthin and conventional DSAEK groups were 424 and 431 µm, respectively (P = 0.84). There was no difference in endothelial viability between the 2 groups. There were no corneal perforations during graft preparation in this study. CONCLUSIONS: Donor preconditioning by pachymetry-controlled stromal dehydration achieved significantly thinner endothelial grafts compared with the conventional DSAEK technique without compromise to endothelial viability or graft wastage.

Adjuvant corneal crosslinking to prevent hyperopic LASIK regression.

PURPOSE: To report the long term outcomes, safety, stability, and efficacy in a pilot series of simultaneous hyperopic laser assisted in situ keratomileusis (LASIK) and corneal crosslinking (CXL). METHOD: A small cohort series of five eyes, with clinically suboptimal topography and/or thickness, underwent LASIK surgery with immediate riboflavin application under the flap, followed by UV light irradiation. Postoperative assessment was performed at 1, 3, 6, and 12 months, with late follow up at 4 years, and results were compared with a matched cohort that received LASIK only. RESULTS: The average age of the LASIK-CXL group was 39 years (26-46), and the average spherical equivalent hyperopic refractive error was +3.45 diopters (standard deviation 0.76; range 2.5 to 4.5). All eyes maintained refractive stability over the 4 years. There were no complications related to CXL, and topographic and clinical outcomes were as expected for standard LASIK. CONCLUSION: This limited series suggests that simultaneous LASIK and CXL for hyperopia is safe. Outcomes of the small cohort suggest that this technique may be promising for ameliorating hyperopic regression, presumed to be biomechanical in origin, and may also address ectasia risk.

Acute transient corneal endothelial changes following selective laser trabeculoplasty.

BACKGROUND: To report for the first time acute transient corneal endothelial changes following selective laser trabeculoplasty. DESIGN: Observational case series at a tertiary referral ophthalmological centre in the United Kingdom (Addenbrooke's Hospital, Cambridge) PARTICIPANTS: Ten consecutive routinely treated patients. METHODS: Baseline measurements of corneal specular microscopy, endothelial cell counts and in vivo confocal microscopy were performed prior to routine selective laser trabeculoplasty treatment. Repeat measurements were made approximately 1 h later and at a 6-week follow up. MAIN OUTCOME MEASURES: Endothelial in vitro laser confocal microscopy, specular microscopic endothelial cell count, endothelial morphology, visual acuity and intraocular pressure. RESULTS: All patients had normal corneal endothelia prior to routine selective laser trabeculoplasty treatment, where 180 degrees of angle was treated. Approximately an hour afterwards, nearly all patients still had normal specular microscopy and cell counts (2237 ± 211 cells/mm(2) ) but had subtle endothelial changes on slit-lamp examination. These changes were found diffusely across the cornea. The changes were not present at the 6-week follow up and cell counts remained unchanged (2278 ± 242 cells/mm(2) ). Acuity remained unchanged throughout and the patients were not aware of these changes subjectively. CONCLUSIONS: Selective laser trabeculoplasty appears to cause transient corneal endothelial changes in most patients that have no impact on cell count or visual acuity. Further work is required to elucidate the mechanism of this phenomenon and any long-term impact.

Comparison of single-step reverse transepithelial all-surface laser ablation (ASLA) to alcohol-assisted photorefractive keratectomy.

PURPOSE: To evaluate postoperative pain, corneal epithelial healing, development of corneal haze, refractive outcomes, and corneal aberrations in a novel one-step, modified transepithelial photorefractive keratectomy (PRK), termed All-surface laser ablation (ASLA), compared to conventional, alcohol-assisted PRK. MATERIALS AND METHODS: Sixty eyes of 30 myopic patients were prospectively recruited to a randomized fellow eye study. Patients underwent conventional alcohol-assisted PRK in one eye (control group) and ASLA-modified transepithelial PRK in the other (30 eyes in each treatment arm). Primary endpoints were postoperative pain and haze scores at 1 day, 3 days, 1 week, and 1, 3, 6, and 12 months. Secondary endpoints included visual acuity at 1, 3, 6, and 12 months, corneal aberrations at 3, 6, and 12 months, and early and late onset haze. Refractive predictability, safety, and efficacy of the two methods were considered. RESULTS: The average age of the cohort was 29 years (standard deviation [SD]: 9; range: 18-46), and the average spherical equivalent refractive error was -4.18 diopters (SD: 1.9). At 3 days after surgery, the average pain score was 64% lower in the ASLA group (P < 0.0005). At this point, 96% of ASLA eyes had no epithelial defect, whereas 43% in the alcohol-assisted group did not achieve complete epithelial healing, and required replacement of bandage contact lens. The haze level was consistently lower in the ASLA group at all time points from 1 to 6 months. CONCLUSION: This study shows that the ASLA technique may have a future role in refractive surgery, due to the fact that it offers faster epithelial healing, lower pain scores, and significantly less haze formation.

Congenital unilateral corneal anaesthesia with microphthalmos: a case report.

Congenital corneal anaesthesia (CCA) is an uncommon condition difficult to diagnose. We report the case of a 20-month-old boy who presented with unilateral congenital corneal anaesthesia. The child was referred with a persistent corneal epithelial defect, unresponsive to symptomatic local treatment for over 10 months. Intensive topical treatment and strict corneal protection led to quick corneal healing. Congenital corneal anaesthesia occurs either alone or in association with neurological diseases or systemic congenital abnormalities. It is important to search for corneal anaesthesia in children with chronic ulcerations of the cornea and self-inflicted injuries. Early diagnosis and treatment are important due to the risk of poor visual prognosis. Management of CCA should aim for the prevention of epithelial defects and is a life-long process.

Clinical and experimental validation of a slit lamp modification to measure toric lens position.

AIM: A simple novel slit lamp beam angular scale modification is described to allow more accurate measurement of toric contact and intraocular lens position. METHODS: The modified slit lamp measuring technique was validated in both an experimental and a clinical setting, with two independent observers. The device was tested against a known reference source, and intraobserver variability in a clinical setting measuring toric intraocular lens (IOL) position was ascertained. RESULTS: In the experimental setting 80 paired observations were analysed. Mean variance was 0.19° (95% CI 0.01-0.37), with a typical measurement error of 0.49°. Intraobserver variation had variance of -0.03° (95% CI -0.2 to 0.15) with a typical error of 0.47°. Clinical assessment of toric IOL position was made in 21 eyes. For this group, intraobserver variation had variance of -0.1° (95% CI -0.281 to 0.62) with a typical error of 1.36°. Intraclass correlation coefficient for all measures was 1.0. CONCLUSION: This simple technique has sufficient precision to be valuable in the clinical setting where photographic techniques may not be available or practical.

Confident complete excision of lid-margin BCCs using a marginal strip: an alternative to Mohs' surgery.

AIMS: To report a new technique of tissue preparation, using a marginal strip, after the excision of eyelid basal cell carcinomas (BCCs) and to report the long-term results of BCCs excised using this technique. METHOD: After the excision of eyelid BCC with a safety margin of 4 mm, a 1 mm strip was excised along the whole perimeter from the margin of the freshly excised specimen. This marginal strip had intact conjunctival mucosa along one edge and skin along the other. The marginal strip and the central tumour mass were then fixed immediately in formal saline and subjected to conventional histopathology. RESULTS: Of the 61 patients who completed a 5 years follow-up, the results of 28 eye-lid BCCs that were within 4 mm of the lid margin are reported. The marginal strip was clear in 22 specimens and had the presence of residual tumour in its margin in 6 specimens. These six 6 cases were further managed by observation (n = 2), by further surgical excision using marginal strip (n = 2) and by Mohs' surgery (n = 2). CONCLUSION: Marginal strip examines the entire resection margins analogous to Mohs' technique and we recommend its use in lid margin where tarsus is present throughout the specimen and >4 mm from the lid margin.

Impact of retinopathy of prematurity screening examination on cardiorespiratory indices: a comparison of indirect ophthalmoscopy and retcam imaging.

PURPOSE: To compare the impact of retinopathy of prematurity (ROP) screening examination between a digital fundus camera and conventional binocular indirect ophthalmoscopy (BIO) using cardiorespiratory indices as a measure of distress. DESIGN: Prospective comparative (nonrandomized) interventional study. PARTICIPANTS: Eighty-six preterm infants with a birth weight of < or =1500 g or gestational age of < or =32 weeks and undergoing ROP screening were included. METHODS: Retinopathy of prematurity screening examination with BIO or the digital fundus camera was performed. Cardiovascular indices were recorded before, during, and 1 hour after examination. Race, birth weight, gender, twin status, duration of the examination, gestational age, and postconceptual age were recorded. MAIN OUTCOME MEASURES: Heart rate (HR), oxygen saturation, respiratory rate (RR), and mean blood pressure (BP). RESULTS: Thirty-four infants underwent indirect ophthalmoscopy, whereas 52 underwent digital fundus camera examination. The increase in HR and RR was significantly higher in the indirect ophthalmoscopy group than in the digital fundus camera group (P<0.05). There was a significant increase in HR and mean BP during examination in both groups (P<0.05). No clinically significant response persisted at 1 hour. Digital fundus camera examination took significantly longer (P<0.001). CONCLUSIONS: Screening for ROP with a digital fundus camera is associated with a significantly lower stress-related response than conventional indirect ophthalmoscopy.