The Relativistic Proton Spectrometer: A Review of Sensor Performance, Applications, and Science

The Relativistic Proton Spectrometer (RPS) on the Van Allen Probes spacecraft was a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ∼ 60 MeV to ∼ 2000 MeV . RPS provided new information about the inner Van Allen belt: a nearby region of space that had been relatively unexplored because of the difficulties of making charged particle measurements there and the associated hazards to satellite operations. We met the primary mission objective of providing accurate data for the AP9 radiation specification model at the high energies where there were little to no data prior to the Van Allen Probes mission. Along the way, we were able to demonstrate the long-term stability of parts of the Inner Belt by comparison with short-lived space science missions that operated decades prior to Van Allen Probes. The most significant surprises were the agreement between RPS and some of those historical measurements and the discovery of a trapped population of > 30 MeV leptons at the outer edge of the inner belt. This end-of-mission paper summarizes the instrument performance, calibration, data products, and specific science and engineering results, and includes suggestions for future investigations of intense radiation fields like those found within the inner belt.

Scheimpflug Corneal Densitometry Values and Severity of Guttae in Relation to Visual Acuity in Fuchs Endothelial Corneal Dystrophy

PURPOSE

The purpose of this study was to investigate the association between corneal densitometry (CD) values from Scheimpflug tomography imaging, severity of guttae, and visual acuity in eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

This was a retrospective, cross-sectional study. Patients with FECD were examined at the Bascom Palmer Eye Institute from January 2015 to September 2019. We extracted CD values at central annuli of 0-2, 2-6, 6-10 and 10-12 mm from Scheimpflug tomography images. We investigated the association of corrected distance visual acuity (CDVA) with CD values, severity of guttae, central corneal thickness (CCT), cataract grade, refractive error, corneal edema grade, age, and gender using multivariate generalized estimating equation regression models.

RESULTS

One hundred ninety-two eyes from 110 patients were included in this study. Increase in central CD values at the 0 to 2 mm zone (P < 0.001), severity of guttae (P = 0.046), age (P < 0.001), cataract grade (P < 0.001), corneal edema grade (P < 0.001), and type of refractive error (P = 0.008) were significantly associated with decreased CDVA. Central corneal thickness, sex, and the peripheral CD values (2-6, 6-10, and 10-12 mm) were not significantly associated with CDVA (P > 0.05) in the final multivariate regression model.

CONCLUSIONS

Our study demonstrates that central CD values at 0 to 2 mm and severity of guttae are each associated with decreased CDVA in FECD. These findings carry implications for patients with FECD considering surgical intervention for phacoemulsification alone, Descemet stripping only, or endothelial cell transplantation and provide a multifactorial perspective on vision loss in FECD.

Topical Ocular Povidone-Iodine as an Adjunctive Preventative Practice in the Era of COVID-19

ABSTRACT

Ophthalmologists and patients have an inherent increased risk for transmission of SARS-CoV-2. The human ocular surface expresses receptors and enzymes facilitating transmission of SARS-CoV-2. Personal protective equipment alone provides incomplete protection. Adjunctive topical ocular, nasal, and oral antisepsis with povidone iodine bolsters personal protective equipment in prevention of provider-patient transmission of SARS-CoV-2 in ophthalmology.

Multi-tiered screening and diagnosis strategy for COVID-19: a model for sustainable testing capacity in response to pandemic

Coronavirus disease 2019 (COVID-19), caused by novel enveloped single stranded RNA coronavirus (SARS-CoV-2), is responsible for an ongoing global pandemic. While other countries deployed widespread testing as an early mitigation strategy, the U.S. experienced delays in development and deployment of organism identification assays. As such, there is uncertainty surrounding disease burden and community spread, severely hampering containment efforts. COVID-19 illuminates the need for a tiered diagnostic approach to rapidly identify clinically significant infections and reduce disease spread. Without the ability to efficiently screen patients, hospitals are overwhelmed, potentially delaying treatment for other emergencies. A multi-tiered, diagnostic strategy incorporating a rapid host immune response assay as a screening test, molecular confirmatory testing and rapid IgM/IgG testing to assess benefit from quarantine/further testing and provide information on population exposure/herd immunity would efficiently evaluate potential COVID-19 patients. Triaging patients within minutes with a fingerstick rather than hours/days after an invasive swab is critical to pandemic response as reliance on the existing strategy is limited by assay accuracy, time to results, and testing capacity. Early screening and triage is achievable from the outset of a pandemic with point-of-care host immune response testing which will improve response time to clinical and public health actions.Key messagesDelayed testing deployment has led to uncertainty surrounding overall disease burden and community spread, severely hampering public health containment and healthcare system preparation efforts.A multi-tiered testing strategy incorporating rapid, host immune point-of-care tests can be used now and for future pandemic planning by effectively identifying patients at risk of disease thereby facilitating quarantine earlier in the progression of the outbreak during the weeks and months it can take for pathogen specific confirmatory tests to be developed, validated and manufactured in sufficient quantities.The ability to triage patients at the point of care and support the guidance of medical and therapeutic decisions, for viral isolation or confirmatory testing or for appropriate treatment of COVID-19 and/or bacterial infections, is a critical component to our national pandemic response and there is an urgent need to implement the proposed strategy to combat the current outbreak.

Empirically Estimated Electron Lifetimes in the Earth's Radiation Belts: Van Allen Probe Observations

We use measurements from NASA's Van Allen Probes to calculate the decay time constants for electrons over a wide range of energies (30 keV to 4 MeV) and L values ( L = 1.3-6.0) in the Earth's radiation belts. Using an automated routine to identify flux decay events, we construct a large database of lifetimes for near-equatorially mirroring electrons over a 5-year interval. We provide the first accurate estimates of the long decay timescales in the inner zone ( ∼ 100 days), which are highly resolved in energy and free from proton contamination. In the slot region and outer zone, we compare our lifetime calculations with prior empirical estimates and find good quantitative agreement (lifetimes ∼ 1-20 days). The comparisons suggest that some prior estimates may overestimate electron lifetimes between L ≈ 2.5-4.5 due to instrumental effects and/or background contamination. Previously reported two-stage decays are explicitly demonstrated to be a consequence of using integral fluxes.

Outcomes of complex Descemet Stripping Endothelial Keratoplasty performed by cornea fellows

BACKGROUND

A major obstacle that academic institutions face is the steep learning curve for cornea fellows initially learning to perform Descemet Stripping Endothelial Keratoplasty (DSEK). The purpose of this study is to evaluate the outcomes of complex DSEK performed by cornea fellow supervised by an attending surgeon at an academic institution.

METHODS

Patients who underwent a complex DSEK procedure performed by a cornea fellow during the years 2009-2013 were included. All the surgeries were supervised by the same cornea attending. All patients had a minimum follow-up of 6 months. Charts were reviewed for demographic data, intraoperative and postoperative complications and clinical outcomes. Corneal graft survival was calculated using the Kaplan-Meier analysis.

RESULTS

Fifty-seven eyes of 55 patients (mean age 77.5 ± 8.5 years) were included in the study with a mean follow-up time of 16.4 ± 15.6 months. Previous graft failure, presence of a tube and history of trabeculectomy were the leading diagnoses to define the surgery as complex. No intraoperative complications occurred. In 21.1% of cases a corneal graft detachment was documented in the first postoperative day. Mean visual acuity improved from 1.06 LogMAR (20/230) preoperatively to 0.39 LogMAR (20/50, p < 0.001) by the sixth postoperative month and to 0.52 LogMAR (20/65, p < 0.001) at the last follow-up visit. Graft failure rate was 29.8%. Kaplan-Meier analysis found a 67.2% graft survival rate at 20 months.

CONCLUSIONS

Complex DSEK can be performed successfully with an acceptable postoperative complication rate by cornea fellows during their training period when supervised by an experienced attending.

The Effect of NSAID Pretreatment on Aqueous Humor Prostaglandin E2 Concentration in Eyes Undergoing Femtosecond Laser-Assisted Capsulotomy

PURPOSE

To assess aqueous humor concentration of prostaglandin E2 (PGE2) after capsulotomy creation using a femtosecond laser (FLAC) in patients pretreated with short-term topical ketorolac versus patients without pretreatment.

METHODS

This prospective study comprised consecutive patients scheduled to undergo cataract surgery using a femtosecond laser platform to perform only capsulotomies. An identical protocol for preoperative mydriasis was used for all the eyes included in the study, while aqueous humor was extracted from the anterior chamber of all patients immediately after the initial side port incision. ELISA was performed to quantify aqueous humor PGE2. The patients were divided into 2 groups; in group 1, the patients received short-term topical ketorolac preoperatively, while the patients in group 2 did not receive NSAID pretreatment.

RESULTS

Twenty eyes of 20 patients were included in the study (10 eyes in each group). Mean concentration of aqueous humor PGE2 after FLAC was 392.16 ± 162.00 pg/ml and 622.63 ± 331.84 pg/ml for groups 1 and 2, respectively. A statistically significant difference in aqueous humor PGE2 concentration between the two groups (p < 0.05) was demonstrated, with the eyes that received ketorolac pretreatment demonstrating a lower concentration of PGE2.

CONCLUSION

Short-term topical use of ketorolac prior to FLAC seems to prevent excessive release of PGE2 in the anterior chamber of the eyes that received NSAID pretreatment when compared to the eyes that did not receive NSAIDs preoperatively.

Comparative activity of antimicrobials against Pseudomonas aeruginosa, Achromobacter xylosoxidans and Stenotrophomonas maltophilia keratitis isolates

BACKGROUND/AIMS

Achromobacter xylosoxidans and Stenotrophomonas maltophilia are emerging corneal pathogens, which are closely related to Pseudomonas aeruginosa, and have intrinsic resistance to many commonly available antimicrobials. The purpose of this study is to compare the in vitro efficacy of 12 antimicrobial agents against A. xylosoxidans, S. maltophilia and P. aeruginosa isolates recovered from clinical cases of keratitis.

METHODS

Recovered corneal isolates (n=58) were identified and extracted from the Microbiology Data Bank of the Bascom Palmer Eye Institute. Comparative in vitro minimum inhibitory concentration (MIC) susceptibility profiles for fluoroquinolones, aminoglycosides, beta-lactams and miscellaneous antibiotics were recorded using the E-test methodology. Pharmacodynamic indices (Cmax/MIC) were calculated.

RESULTS

A. xylosoxidans and S. maltophilia isolates were resistant to fluoroquinolones, aminoglycosides and ceftazidime (susceptibility rate ranging from 0% to 30%) while P. aeruginosa isolates showed a susceptibility rate of 95%-100% to these antimicrobials (P<0.00001 for the various antimicrobials). Exception was moxifloxacin with 80% of susceptibility rate to S. maltophilia isolates and Cmax/MIC=10.19. Ninety to 100% susceptibility rates were found for minocycline and trimethoprim/sulfamethoxazole for both A. xylosoxidans and S. maltophilia. One hundred per cent of the A. xylosoxidans isolates were susceptible to piperacillin/tazobactam and ticarcillin/clavulanic acid.

CONCLUSIONS

There is a significant difference in susceptibility patterns between A. xylosoxidans, S. maltophilia and P. aeruginosa. Fluoroquinolones and aminoglycosides may not be effective against A. xylosoxidans and S. maltophilia. Antibiotics that are not commercially available as eye drops, such as beta-lactams for A. xylosoxidans, and trimethoprim/sulfamethoxazole and minocycline for both A. xylosoxidans and S. maltophilia should be considered.

Effects of Femtosecond Laser-Assisted Cataract Pretreatment on Pupil Diameter: A Comparison Between Three Laser Platforms

PURPOSE

To assess pupil diameter before and after femtosecond laser-assisted cataract surgery (FLACS) pretreatment and compare the outcomes of three laser platforms.

METHODS

This prospective observational case series included consecutive patients scheduled to undergo cataract extraction using FLACS between August 2013 and February 2015. All eyes received FLACS pretreatment using three laser platforms: LenSx (Alcon Laboratories, Inc., Fort Worth, TX), Catalys (Abbott Medical Optics Inc., Santa Ana, CA), and Victus (Bausch & Lomb, Inc., Rochester, NY). The same protocol for preoperative medical mydriasis was used for all patients, and pupil diameter was assessed immediately before and 3 minutes after FLACS using a surgical ruler.

RESULTS

A total of 198 eyes of 161 patients were included in the study. Mean pupillary miosis was 1.42 ± 1.26 mm for the LenSx, 0.66 ± 0.89 mm for the Catalys, and 0.14 ± 0.34 mm for the Victus groups. Furthermore, 8 of the 198 eyes (4.0%) demonstrated a pupil diameter of less than 5 mm after FLACS and 48 eyes (24.24%) demonstrated a pupil diameter of 6 mm or less. There was a statistically significant decrease in pupil diameter for all groups individually (P < .05). There was also a statistically significant difference among the three groups (P < .05), with LenSx inducing the highest degree of miosis, followed by Catalys, and finally Victus. A correlation between the pupil diameter before FLACS and degree of FLACS-induced miosis was demonstrated (P < .05), with larger pupil diameter before FLACS associated with greater miosis.

CONCLUSIONS

FLACS pretreatment seems to induce significant pupillary miosis with all laser platforms assessed in this study. The decrease in pupil diameter after FLACS reached clinical significance for cataract extraction (< 5 mm) in 4.0% of cases, whereas 20.2% of eyes demonstrated small pupil diameter (≤ 6 mm) after FLACS pretreatment.

Spontaneous Scleral Perforation of an Anterior Chamber Intraocular Lens

A routine eye examination of a 69-year-old man revealed a scleral perforation of one of the haptics of the anterior chamber intraocular lens (AC IOL) which had been implanted many years ago. The patient was asymptomatic with good visual acuity. His history was negative for any trauma, eye rubbing, topical corticosteroid use, or autoimmune disease. The horizontal and vertical white-to-white diameters of the cornea in the right eye were 11.5 and 10.5 mm, respectively. Anterior segment optical coherence tomography showed the anterior chamber length to be 12.28 mm horizontally and 10.63 mm vertically. The patient underwent an IOL exchange, and the length of the explanted AC IOL was measured to be 12 mm. We speculate that the AC IOL, which was vertically aligned, was oversized. This case demonstrates the need for proper sizing and positioning of an AC IOL. In complex cases where AC IOL may be used, measuring the horizontal and vertical lengths of the anterior chamber by anterior segment optical coherence tomography prior to surgery may be useful.

Allergic conjunctivitis: an update on diagnosis and management

PURPOSE OF REVIEW

The focus of this review is to provide a logical paradigm for the diagnosis and treatment of ocular allergies, with a focus on seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC).

RECENT FINDINGS

Several classes of topical medications are currently available for the management of ocular allergies, including: lubricating agents, vasoconstrictors, antihistamines, mast cell stabilizers, and topical corticosteroids.

SUMMARY

SAC and PAC make up the vast majority of ocular allergy cases. A proactive approach to these diseases, anticipating the regional spring and fall allergen spikes, is needed for optimally managing these disorders. A multifaceted treatment regimen comprising patient education, lifestyle modification, and topical medications (such as antihistamines and/or mast cell stabilizers and corticosteroids) may be required in order to manage ocular allergies effectively. The appropriate treatment paradigm is based on the severity of the patients' signs and symptoms. For moderate-to-severe cases, especially chronic vernal keratoconjunctivitis, atopic keratoconjunctivitis, and giant papillary conjunctivitis, comanagement with an ophthalmologist is recommended.

Management of seasonal allergic conjunctivitis: guide to therapy

Seasonal allergic conjunctivitis (SAC) is an inflammatory response of the conjunctiva triggered by exposure to seasonal allergens. Treatment options for SAC include artificial tears, antihistamines, decongestants, mast cell stabilizers, nonsteroidal anti-inflammatory drugs, dual antihistamine/mast cell stabilizers, immunotherapy and corticosteroids. Topical, intranasal and systemic formulations of corticosteroids have traditionally provided the most effective relief of the inflammation and signs and symptoms associated with severe, acute exacerbations of SAC. However, steroid-induced ocular and systemic side-effects have limited the prescribing of these agents. This limitation of traditional corticosteroids led to the development of modified corticosteroids that retain the anti-inflammatory mechanism of action of traditional corticosteroids with a much-improved safety profile because of their rapid breakdown to inactive metabolites after exerting their activity. The development of one such novel corticosteroid, loteprednol etabonate (LE), led to the insertion of an ester (instead of a ketone) group at the carbon-20 (C-20) position of the basic corticosteroid structure. Clinical trials assessing this C-20 ester corticosteroid have demonstrated similar efficacy to C-20 ketone corticosteroids in the prevention or treatment of the signs and symptoms of SAC but with a greatly improved safety profile, as the C-20 ester corticosteroid is less likely to elevate intraocular pressure. In addition, the ketone at the C-20 position has been implicated in the formation of cataract, while nonketolic corticosteroids do not form Schiff base intermediates with lens proteins, which is a common first step in cataractogenesis. The clinical relevance of the C-20 ester corticosteroid class, as modelled by LE, is that they provide both effective and safe treatment of the inflammation associated with SAC and relief of its signs and symptoms. Loteprednol etabonate offers a well-tolerated treatment option for patients with debilitating acute exacerbations as well as chronic forms of the disease.

Experimental model for analyzing cutting resistance by various knives for cataract surgery

BACKGROUND

The trend in current cataract surgery towards clear corneal incision and sutureless procedures makes us realize the importance of wound construction. For optimal surgical outcomes, we need good surgical instruments. In this study, we employed a resistance recording system to analyze the characteristics of seven commercially available disposable cataract knives and to find clues for the future development of 'good' cataract knives.

METHODS

The cutting resistance was recorded during perpendicular penetrations of porcine scleral tissues by cataract knives. This data was processed and analysed mathematically with MATLAB software (The MathWorks, Inc, Natick, MA, USA) to see the resistance wave shapes and their derivatives to show the products' differing characteristics.

RESULTS

The wave shapes demonstrated product-dependent characteristics. The average maximum penetration resistance varied from 86.4 to 233 mN. The first order time derivatives also showed distinctive wave shapes.

CONCLUSION

We used an experimental model to analyze one aspect of a knife's character. This model can help give clues for future developments, although this is the initial step.

Szt2, a novel gene for seizure threshold in mice

In a chemical mutagenesis screen we identified Szt2 (seizure threshold 2) as a gene that confers low seizure threshold to mice and may also enhance epileptogenesis. The semidominant phenotype was mapped to Chromosome 4 and narrowed further to a critical interval of approximately 650 kb. A novel large (> 10 kb) transcript in the critical interval was found to have fourfold increased steady-state expression at the RNA level in Szt2 homozygous mutant brain. The corresponding 72 exon gene encodes a 378-kD protein with no significant or suggestive sequence similarities to any other protein. The mutant allele of Szt2 contains a splice donor mutation after exon 32, predicting transcriptional read-through, translational frameshift and premature stop. A second Szt2 allele, containing a gene-trap mutation in exon 21, also conferred a low seizure threshold and increased RNA expression, but unlike the original allele, some gene-trap homozygotes died embryonically. Szt2 is transcribed in many tissues, with the highest expression in brain, and it is also expressed during embryonic development. Szt2 is highly conserved in evolution, with a clear, single orthologue found in all land vertebrates and in many invertebrates. Interestingly, in mammals the Szt2 gene resides in a highly conserved head-to-head configuration with Med8 (which encodes a Mediator complex subunit), separated by only 91 nt. While the biological function of Szt2 remains unknown, its high conservation, unique structure and effect on seizure threshold suggest that it serves an important role in the central nervous system.

Kill rates of preserved and preservative-free topical 8-methoxy fluoroquinolones against various strains of Staphylococcus

PURPOSE

To assess the kill rates of preserved and preservative-free 8-methoxy fluoroquinolones and benzalkonium chloride (BAC) against isolates of Staphylococcus aureus and coagulase-negative Staphylococcus (CNS) species.

SETTING

Bascom Palmer Eye Institute, Miami, Florida, USA.

METHODS

Ocular and standard isolates of S aureus and CNS were inoculated with saline, 0.005% BAC, gatifloxacin 0.3% containing 0.005% BAC (Zymar), or BAC-free moxifloxacin 0.5% (Vigamox) at 37 degrees C. Bacterial viability was assessed after 15 minutes, 30 minutes, and 60 minutes.

RESULTS

Thirteen isolates of S. aureus and 5 isolates of CNS were used. The mean initial load of bacterial inoculum was 5.45 log colony-forming units (CFU)/mL +/- 0.37 (SD). Saline did not affect the density of staphylococci; BAC significantly decreased the staphylococci count to a mean of 3.80 +/- 0.32 log CFU/mL at 60 minutes (P<.05). Gatifloxacin 0.3% reduced the number of staphylococci significantly more than moxifloxacin 0.5% at 15 minutes (mean 0.47 +/- 1.12 log CFU/mL versus 4.55 +/- 0.60 log CFU/mL), 30 minutes (mean 0.07 +/- 0.31 log CFU/mL versus 3.82 +/- 1.07 log CFU/mL), and 60 minutes (mean 0.00 +/- 0.00 log CFU/mL versus 2.75 +/- 1.29 log CFU/mL) (P<.005). Gatifloxacin 0.3% completely eradicated most S. aureus (10/13) and CNS (3/5) isolates at 15 minutes; moxifloxacin 0.5% did not achieve complete kill in any S. aureus isolate (13/13) or in most CNS isolates (4/5) at 60 minutes.

CONCLUSION

The commercial formulation of gatifloxacin 0.3% containing BAC 0.005% completely eradicated staphylococcal isolates more rapidly than the BAC-free formulation of moxifloxacin 0.5% or BAC 0.005% alone.

Acute conjunctivitis: truth and misconceptions

OBJECTIVE

Acute conjunctivitis is an extremely common condition and can be associated with significant morbidity and economic burden. Despite this, considerable controversy exists pertaining to the prevalence, diagnosis, management, and treatment of the condition. A panel of ophthalmology experts was assembled to review and discuss the current evidence based literature as it pertains to each of these persistent controversies.

METHODS AND SCOPE

An acute conjunctivitis round table symposium was convened at the American Academy of Ophthalmology meeting in Atlanta, November 2008. The expert panelists consisted of four academic ophthalmologists in the field of cornea and external disease, whose discussion was informed by an English language literature survey carried out on the PubMed database for the period of January 1972 to October 2008. A narrative summary was generated from the literature review and direct transcription of this event, from which this Review article was developed.

FINDINGS AND CONCLUSIONS

Considerable light has been shed on acute microbial conjunctivitis and especially those cases caused by adenovirus. Many of the myths that have perpetuated for years have been debunked by emerging evidence. The advent and the implementation of better diagnostic tools and anti-viral medications will help clinicians to improve their diagnostic accuracy, improve management and treatment decisions, and ultimately benefit patients while saving overall healthcare costs.

Ocular toxicity of intravitreal trovafloxacin in the pigmented rabbit

PURPOSE

Trovafloxacin is an expanded spectrum, newer-generation fluoroquinolone antibiotic with improved Gram-positive and anaerobic activity compared with existing quinolones, while maintaining Gram-negative activity comparable to ciprofloxacin. Given its broad spectrum of activity, trovafloxacin may have potential use for treatment of acute bacterial endophthalmitis. This study examined the toxicity of intravitreally administered trovafloxacin in the pigmented rabbit eye.

METHODS

Doses of trovafloxacin ranging from 12.5 microg to 1000 microg were injected into the mid-vitreous of Dutch Belted rabbit eyes. Clinical examination was performed at 1, 3, and 14 days following injection. Animals were sacrificed and eyes were enucleated 14 days following injection. Light microscopy (LM) and transmission electron microscopy (TEM) studies of the optic nerve head, medullary ray, and inferior retina were performed to determine toxicity.

RESULTS

At intravitreal doses of 500 microg and less, no toxicity was observed at the ophthalmoscopic or light microscopic level. By TEM, a dose-dependent increase in injury to retinal pigment epithelium, photoreceptors, and nerve fibers in the optic nerve head and medullary ray was observed from 50 microg to 500 microg. No toxicity was noted at doses of 12.5 microg and 25 microg. At doses of 750 microg and above, edema of the medullary ray was noted on ophthalmoscopy. Swelling of the peripapillary medullary ray and necrosis of the inferior retina were evident on LM.

CONCLUSION

Intravitreal trovafloxacin doses of 50 microg and higher in the pigmented rabbit eye cause retinal and nerve fiber injury. Intravitreal doses 25 microg and lower appear to be safe, with no evidence of ocular toxicity.

Conjunctival tissue pharmacokinetic properties of topical azithromycin 1% and moxifloxacin 0.5% ophthalmic solutions: a single-dose, randomized, open-label, active-controlled trial in healthy adult volunteers

BACKGROUND

Effective ocular tissue concentrations and prolonged residence times of antibacterial agents are important in treating both acute and chronic diseases. Conjunctival biopsy allows the determination of specific tissue concentration data for topical ophthalmic agents. Drug concentration analysis at various time points following instillation allows interpretation of the residence time and a rationale for dosing frequency.

OBJECTIVE

This study compared the pharmacokinetic parameters of 2 currently available topical ocular antibiotics-azithromycin ophthalmic solution 1% and moxifloxacin ophthalmic solution 0.5%-in the conjunctiva of healthy volunteers after a single topical administration.

METHODS

This single-dose, randomized, open-label, active-controlled clinical trial was conducted at ORA Clinical Research and Development, North Andover, Massachusetts. Subjects were randomly assigned to receive a single dose of azithromycin or moxifloxacin and to undergo biopsy sampling at 30 minutes or 2, 12, or 24 hours after administration. Concentrations of azithromycin and moxifloxacin were determined using liquid chromatography tandem mass spectrometry. Adverse events (AEs) were assessed at all visits using visual acuity measurements, slit-lamp biomicroscopy, and direct questioning.

RESULTS

Forty-eight subjects (mean age, 40.0 years; 48% female; 96% white, 2% black, and 2% Asian) underwent conjunctival biopsy. Mean (SD) concentrations of azithromycin in conjunctival tissue (lower limit of quantitation [LLOQ], 1 microg/g for 1-mg biopsy specimen) were 131 (89), 59 (19), 48 (24), and 32 (20) microg/g at 30 minutes and 2, 12, and 24 hours, respectively (median values, 117, 69, 46, and 30 microg/g). Mean concentrations concentrations of moxifloxacin in conjunctival tissue (LLOQ, 0.05 microg/g for 1-mg biopsy sample) were 1.92 (2.03), 3.77 (8.98), 0.02 (0.04), and 0.01 (0.02) microg/g at 30 minutes and 2, 12, and 24 hours, respectively (median values, 1.12, 0.12, <0.05, and <0.05 microg/g). Thirteen subjects (6 in the azithromycin group and 7 in the moxifloxacin group) experienced 20 AEs, 11 of which were considered possibly related to study treatment, and 15 of which were ocular (most commonly conjunctival hemorrhage).

CONCLUSIONS

In this single-dose study of 2 currently available topical ocular antibiotics in healthy volunteers, therapeutic concentrations were achieved with both agents. Both treatments were well tolerated in the population studied. Clinical Trials Identification Number: NCT00564447.

The Use of Polarization Filters to Detect the Edge of the Descemet's Stripping Automated Endothelial Keratoplasty(DSAEK) Graft

PURPOSE

To report the technique of combining the two different polarization filters to detect the flap edge of the corneoscleral tissue before trephining the Descemet's stripping automated endothelial keratoplasty (DSAEK) tissue.

METHODS

A human DSAEK donor tissue was prepared with mechanical microkeratome and the tissue on the cutting block was brought under the microscope. The liner, circular, or the combination of these two polarization filters was placed between the tissue and the microscope. The tissue images were taken with digital camera under either of 3 settings.

RESULTS

The combination of circular and linear polarization filters enabled us to recognize the edge of the flap more easily than others.

CONCLUSION

This simple system with polarization filters was effective in clear visualization of the flap edge during DSAEK tissue preparation. These features may significantly enhance safety of various surgical procedures, in addition to DSAEK tissue preparation.

Subconjunctival Air Leakage After Descemet's Stripping Automated Endothelial Keratoplasty(DSAEK) in a Post-Trabeculectomy Eye

Purpose:

To report a case of subconjunctival air leakage from the anterior chamber (AC) into a trabeculectomy bleb after Descemet's stripping automated endothelial keratoplasty (DSAEK).

Methods:

An 89 year-old woman with a previous history of primary open angle glaucoma in her left eye and previous trabeculectomy with mitomycin C had DSAEK on the patient’s left eye in order to treat her endothelial disease. During the DSAEK procedure, air was injected into the AC to aid in graft adherence.

Results:

The day after the surgery, subconjunctival air leakage from the AC into a trabeculectomy bleb was observed.

Conclusions:

Although our patient did not have any complications from this leak, there exists the potential for hypotony, bleb-related infections, and dislocations of the DSAEK graft. Given the potential consequences, these patients should be monitored closely.

Impact of contact lens group on antifungal efficacy of multipurpose disinfecting contact lens solutions

PURPOSE

To evaluate and compare the in vitro effectiveness of multipurpose contact lens solutions (MPDS) to inhibit fungal colonization of Food and Drug Administration (FDA) contact lens groups.

METHODS

Contact lenses from FDA groups I (low water content, nonionic), II (high water content, nonionic), III (low water content, ionic), and IV (high water content, ionic) were placed in sterile contact lens cases with 2 mL of ReNu MultiPlus, ReNu with MoistureLoc, or OPTI-FREE RepleniSH. Each contact lens-multipurpose solution combination was challenged with 0.1 mL of 10(6) colony-forming units/mL of Fusarium oxysporum and incubated at room temperature. Contact lenses and aliquots from phosphate-buffered saline rinse solutions, multipurpose solutions in cases, and lens cases were sampled at 24, 48, and 72 hours, plated on Sabouraud's agar, incubated at room temperature, and observed for growth (i.e., adhesion) for 1 to 7 days.

RESULTS

Used multipurpose contact lens solutions met or exceeded the 1-log reduction requirement of the FDA stand-alone test. Viable fungal colonies were recovered from group II lenses after 24 hours of storage in all three multipurpose solutions. Colonization was also detected with at least one contact lens-multipurpose solution pairing from groups I, III, and IV. Fungi were not recovered from lens-solution combinations after 24 hours or from phosphate-buffered saline solutions or lens cases at any period.

CONCLUSIONS

Antifungal activity of contaminated multipurpose solutions may be insufficient to prevent fungal colonization of contact lens materials despite meeting or exceeding the FDA stand-alone test criteria. Colonized lens may increase the risk of fungal keratitis.

Subconjunctival emphysema after descemet's stripping automated endothelial keratoplasty (DSAEK)

DSAEK has recently evolved as a preferred method in place of PKP. After DSAEK, we experienced subconjunctival emphysema, decreased air bubble in the AC and low IOP. This could lead to complications, higher rate of dislocation or infection. We should control the wound closure with suture when in doubt.

Corneal tattoo with tea infusion

Except in animal models of cataractogenesis, the literature on the effects of tea infusion on ocular tissue is scant. In our patient, prolonged exposure to tea infusion may have led to a hypesthetic cornea with secondary limbal stem cell loss. In turn, the eye developed keratinization and corneal neovascularization.

Photorefractive keratectomy for refractory laser in situ keratomileusis flap striae

Photorefractive keratectomy (PRK) with mitomycin-C (MMC) was performed in 2 patients with visually significant, complicated laser in situ keratomileusis flap striae. These striae had been resistant to multiple treatments, including stretching, suturing, and PRK. The visual symptoms in both patients resolved after PRK with MMC, and both patients were stable 1 year later. Wavefront-guided PRK with MMC may be a viable treatment for patients who have complicated flap striae resistant to standard measures.

Descemet-Stripping Automated Endothelial Keratoplasty

PURPOSE

To qualitatively assess the extent and pattern of endothelial trauma on corneal donor Descemet-stripping automated endothelial keratoplasty (DSAEK) buttons resulting from DSAEK insertion forceps.

METHODS

An in vitro model was used with corneoscleral rims, DSAEK quality corneal donor tissue, and DSAEK insertion forceps. After insertion of the donor button through the corneoscleral rim, a vital dye assay was used to identify devitalized and necrotic endothelial cells (with alizarin red S and typan blue).

RESULTS

Corneal buttons evaluated with the forceps delivery model showed that, for each arm of the forceps, there were 2 parallel bands of purple/red staining. In addition, orthogonal wrinkles of scattered blue devitalized nuclei were seen in a parallel arrangement.

CONCLUSIONS

The DSAEK insertion forceps resulted in a reproducible pattern of endothelial damage. A thorough understanding of iatrogenic endothelial trauma could result in improved forceps design and perhaps help mitigate the high rate of donor dislocation and graft failure in the future.

Perspectives on antibiotics for postoperative endophthalmitis prophylaxis: Potential role of moxifloxacin

To aid the cataract surgeon's understanding of rational approaches to antimicrobial prophylaxis and place the European Society of Cataract & Refractive Surgeons (ESCRS) postoperative endophthalmitis study in perspective, a review was conducted of published and unpublished data on intracameral antibiotic use during cataract surgery and the antimicrobial efficacy, pharmacodynamics, ocular penetration, and safety of moxifloxacin. The ESCRS-sponsored study of postoperative endophthalmitis prophylaxis reported rates of presumed infectious postoperative endophthalmitis of 0.07% with intracameral cefuroxime treatment and 0.34% in control groups. Postoperative endophthalmitis after cefuroxime use was mostly due to cefuroxime-resistant gram-positive bacteria. Intracameral cefuroxime also requires extemporaneous compounding, has short-term stability, and carries a risk for hypersensitivity. Moxifloxacin, a fourth-generation fluoroquinolone, has potent and rapid bactericidal activity against the most common gram-positive postoperative endophthalmitis pathogens, has excellent ocular penetration after topical administration, and is available in a self-preserved ophthalmic formulation that has been shown safe and effective in preventing endophthalmitis when administered intracamerally in an animal model. Available data suggest that the optimum antibiotic regimen and route of delivery for cataract surgery antimicrobial prophylaxis require further study. Moxifloxacin offers many theoretical advantages that make it an attractive first-line choice for topical use and of interest for intracameral administration.

Surgical Feasibility Study of a Novel Polytetrafluoroethylene Graft Design for the Treatment of Peripheral Arterial Disease

Disturbed flow patterns, material mismatch, and surgical injury are often cited as being significant contributors to failure at the distal end of femoropopliteal bypass grafts. The objective of this research is to propose a novel bypass graft design concept which seeks to reduce the incidence of disturbed flow in the bypass junction and to establish the surgical feasibility of the proposed device. A preliminary evaluation of the hemodynamic benefit associated with the proposed device was made using computational fluid dynamics. A prototype of the device was then constructed from commercially available materials, and it was prepared for implantation into the aorta of a pig. The computational model of the proposed device showed that significant flow correction was occurring in the in vitro model due to the geometric configuration of the design. The magnitude of the peak wall shear stress in the recirculation region was noted to decrease by 78%. Surgical feasibility of the proposed device was verified by successful implantation into the aorta of the pig. The pig was sacrificed after 7 weeks, the graft and host artery were excised, and histological examination downstream from the distal junction showed that intimal hyperplasia had developed in the host artery. The proposed device is surgically feasible and may offer a significant hemodynamic advantage over current graft designs.

Complications of sequential keratorefractive and vitreoretinal surgery

We describe 2 complications of sequential keratorefractive and vitreoretinal surgery not previously reported. Epithelial ingrowth occurred in 1 patient who experienced laser in situ keratomileusis flap dehiscence and replacement during vitreoretinal surgery. In the second patient, a flap could not be created with a microkeratome or a femtosecond laser because of anatomical changes from previous vitreoretinal surgery. Anatomic repair of the vitreoretinal pathology and completion of keratorefractive surgery with good visual outcomes were achieved in both patients. Flap stability should be an important operative consideration for vitreoretinal surgeons; patients may have to be informed of the risk for and possible subsequent complications of iatrogenic flap dehiscence. Refractive surgeons operating on patients after vitreoretinal surgery may encounter difficulty creating a LASIK flap even with a femtosecond laser and may need to consider other keratorefractive options.

Dysfunctional Tear Syndrome

PURPOSE

To develop current treatment recommendations for dry eye disease from consensus of expert advice.

METHODS

Of 25 preselected international specialists on dry eye, 17 agreed to participate in a modified, 2-round Delphi panel approach. Based on available literature and standards of care, a survey was presented to each panelist. A two-thirds majority was used for consensus building from responses obtained. Treatment algorithms were created. Treatment recommendations for different types and severity levels of dry eye disease were the main outcome.

RESULTS

A new term for dry eye disease was proposed: dysfunctional tear syndrome (DTS). Treatment recommendations were based primarily on patient symptoms and signs. Available diagnostic tests were considered of secondary importance in guiding therapy. Development of algorithms was based on the presence or absence of lid margin disease and disturbances of tear distribution and clearance. Disease severity was considered the most important factor for treatment decision-making and was categorized into 4 levels. Severity was assessed on the basis of tear substitute requirements, symptoms of ocular discomfort, and visual disturbance. Clinical signs present in lids, tear film, conjunctiva, and cornea were also used for categorization of severity. Consensus was reached on treatment algorithms for DTS with and without concurrent lid disease.

CONCLUSION

Panelist opinion relied on symptoms and signs (not tests) for selection of treatment strategies. Therapy is chosen to match disease severity and presence versus absence of lid margin disease or tear distribution and clearance disturbances.

Insurgence of Fusarium Keratitis Associated With Contact Lens Wear

OBJECTIVE

To describe the clinical presentation and course of patients who developed keratitis due to Fusarium while wearing nontherapeutic soft contact lenses.

METHODS

A retrospective review of microbiologic records from January 1, 2004, through April 15, 2006, was performed, identifying all patients with corneal ulceration and a culture positive for Fusarium species. Medical records of 34 patients were reviewed for clinical characteristics, treatment regimens, and microbiologic features.

RESULTS

The most common antimicrobial medications administered prior to Fusarium diagnosis were antibacterials in 31 of 34 patients. No distinct preponderance of any one brand of either contact lens or solution was identified. The microbiologic corneal cultures found Fusarium oxysporum in 20 cases, Fusarium solani in 3 cases, Fusarium species not further identifiable in 10 cases, and no growth in 1 case. Patients with a delayed onset of treatment had a tendency for prolonged treatment until cure.

CONCLUSIONS

Fusarium has previously been an unusual organism in the etiology of infectious keratitis in the setting of nontherapeutic soft contact lens wear. A delay in proper diagnosis and intervention may contribute to a prolonged treatment course. The microbial spectrum of contact lens-related keratitis may be evolving with higher participation of Fusarium species compared with prior reports.

Excimer laser surgery for correction of ametropia after cataract surgery

PURPOSE

To review the cases of patients who had excimer laser refractive surgery to correct unintentional or undesired ametropia after cataract extraction with intraocular lens (IOL) implantation.

SETTING

Wilmer Laser Vision Correction Center, Wilmer Eye Institute, Baltimore, Maryland, USA.

METHODS

In this retrospective noncomparative review of consecutive cases, the Wilmer Laser Vision Correction Center's database was searched for patients who had laser in situ keratomileusis or photorefractive keratectomy to correct ametropia after cataract extraction with IOL implantation.

RESULTS

Using the Visx Star excimer laser system (Visx, Inc.), 11 procedures were performed in 11 eyes of 10 patients a mean of 47 months (range 2 to 216 months) after cataract extraction with IOL implantation. Except for 1 patient with a silicone plate lens, all patients received 3-piece poly(methyl methacrylate) lenses. The mean age at time of excimer treatment was 75 years (range 70 to 81 years). Before laser surgery, the mean spherical equivalent of patient eyes was -3.76 diopters (D) +/- 2.50 (SD) (range -6.50 to +0.75 D), spherical refraction ranged from -9.00 D to plano, and the highest cylindrical refraction was +5.50 D. At last follow-up (mean 12.2 months; range 1 to 38 months), the mean manifest spherical equivalent was -0.88 +/- 1.43 D (range -2.75 to +2.13 D). Changes in mean manifest spherical equivalent were highly significant (P = .03, Wilcoxon signed rank test for paired values). There was no difference between targeted and achieved postoperative refraction (P = .34, Wilcoxon test). Increasing age was correlated with a hyperopic shift (r = 0.525, P = .05). All patients were satisfied with their final uncorrected visual acuity (UCVA), which improved in every case. Except for 1 patient in whom an epiretinal membrane developed, best spectacle-corrected visual acuity remained unchanged or improved.

CONCLUSIONS

In this series of patients, who were a few decades older than the typical excimer laser candidate, laser refractive surgery was a safe, effective, and predictable method to correct ametropia after cataract extraction with IOL implantation. It may be a viable, noninvasive alternative to intraocular surgery, which has potential complications. Although satisfactory for all patients, final UCVA was not as high as that reported in laser refractive surgery patients in general, and this result may be because of prior cataract extraction with IOL implantation or increased age.

Aqueous Penetration and Biological Activity of Moxifloxacin 0.5% Ophthalmic Solution and Gatifloxacin 0.3% Solution in Cataract Surgery Patients

PURPOSE

To measure the achievable perioperative aqueous concentration of the commercially available topically administered fourth generation fluoroquinolones, moxifloxacin 0.5% ophthalmic solution, and gatifloxacin 0.3% ophthalmic solution, and to correlate this concentration with the agents' biological efficacy in the aqueous humor of patients undergoing routine cataract surgery.

DESIGN

Prospective, randomized, parallel, double-masked, clinical trial.

PARTICIPANTS

Fifty patients undergoing cataract extraction.

METHODS

Patients (n = 25) were given perioperative topical moxifloxacin 0.5% or topical gatifloxacin 0.3% (n = 25). One drop of antibiotic was administered every 10 minutes for 4 doses beginning 1 hour prior to surgery. Aqueous humor was sampled via paracentesis and antibiotic concentrations were determined using validated high performance liquid chromatography (HPLC) procedures. Dilution analyses were performed to determine the biological efficacy of the agents in the aqueous against Staphylococcus epidermidis, the most common cause of postcataract endophthalmitis.

MAIN OUTCOME MEASURES

Aqueous humor antibiotic concentrations were measured using HPLC and microdilution bioassay techniques. Biological activity was measured as minimal inhibitory dilution and minimal bactericidal dilution.

RESULTS

Aqueous humor concentrations for moxifloxacin via HPLC analysis were 1.80 (+/-1.21) microg/ml, whereas those for gatifloxacin were 0.48 (+/-0.34) microg/ml. This 3.8-fold difference in aqueous humor antibiotic concentrations was statistically significant (P = 0.00003). Similarly, the biological dilution analysis of the aqueous humor samples showed that moxifloxacin attained an estimated activity of 2.1 microg/ml, whereas the gatifloxacin activity was approximately 0.4 mug/ml, which represented a 4.9-fold difference.

CONCLUSIONS

This study demonstrated that after topically administered perioperative antibiotics with cataract surgery, moxifloxacin 0.5% ophthalmic solution achieved a statistically significantly higher concentration in aqueous humor compared with gatifloxacin (P = 0.00003). Results from the broth dilution analysis showed that moxifloxacin 0.5% was biologically more active against S. epidermidis than gatifloxacin 0.3% in aqueous humor after topical application. There were no adverse events reported, and incision wounds healed quickly and as expected.

Patients with prion disease: planning for eye surgery

Human prion diseases are characterized by rapidly progressive fatal neurodegenerative symptoms. In prion diseases, neural tissues have the greatest potential for infectivity, and ocular tissues are included in the category of high infection risk. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have published specific infection control guidelines for prion diseases. Standard Precautions are utilized for all patient care. Additional and more stringent measures are indicated when patients with known or suspected prion disease require ocular surgery. Measures include: notification of infection control, operating room, and decontamination personnel; use of disposable instruments whenever possible; special processing for non-disposable instruments; identification of tissue and laboratory specimens; and incineration or other appropriate treatment of infectious waste. Clumsiness, vision changes, and myoclonus in association with prion disease may predispose patients to traumatic ocular emergencies. Proactively, procedure areas should utilize a multidisciplinary approach to do the following: identify urgent surgical procedures that are likely to be required by these patients; evaluate cleaning procedures that will result in effective tissue removal; identify critical, non-disposable equipment for which there are no disposable alternatives; identify decontamination methods available to the specific facility as well as to identify which recommended decontamination procedures may not be appropriate for ocular instrumentation; and develop precautionary procedures specifically for decontamination of equipment and instruments.

Emerging guidelines for use of NSAID therapy to optimize cataract surgery patient care

This analysis provides guidelines for the proper use of topical ophthalmic nonsteroidal anti-inflammatory drugs (NSAIDs), discusses their effect on inflammation, and their role in the prevention of cystoid macular edema (CME). A novel treatment strategy is presented for recommended topical ophthalmic NSAID dosing in patient populations based on risk factors for CME. The article reviews current topical ophthalmic NSAIDs, as well as a newest generation of pro-drug NSAIDs. In addition, combination therapy of NSAIDs and corticosteroids are discussed, along with a general review of therapeutic guidelines for dosing regimens, and benefits and risks of therapy. The goal of this analysis is to provide a suggested therapeutic regimen with topical NSAIDs to assist in achieving optimal clinical and functional outcomes.

High Interocular Corneal Symmetry in Average Simulated Keratometry, Central Corneal Thickness, and Posterior Elevation

PURPOSE

The purpose of this study was to assess interocular corneal symmetry in average simulated keratometry, corneal thickness, and posterior corneal elevation.

METHODS

This retrospective analysis included data from scanning slit topography (Orbscan II; Bausch and Lomb, Rochester, NY) on 242 eyes from 121 consecutive patients undergoing standard evaluation for consideration of elective laser vision correction. The symmetry between the right and left eye in average simulated keratometry, minimum central corneal thickness, and posterior corneal elevation was assessed by comparative data analysis.

RESULTS

Simulated keratometry ranged from 39.9 to 48.6 D. The interocular difference in average simulated keratometry was 0.47 D (standard deviation [SD] 0.43). The interocular Pearson correlation coefficient for average simulated keratometry was 0.90 (p < 0.001). The range of minimum corneal thickness was 432 to 628 microm. The interocular Pearson correlation coefficient for minimum central corneal thickness was 0.95 (p < 0.001). Right and left eye minimum corneal thickness differed by an average 8 microm (SD 7). The range of posterior elevation was -4 to 54 microm. The average difference in posterior corneal elevation between the right and left eye was 6 microm (SD 5). The interocular Pearson correlation coefficient for posterior corneal elevation was 0.72 (p < 0.001). The average posterior elevation was 19 microm (SD 11).

CONCLUSIONS

Although a wide range of values exists in simulated keratometry, minimum corneal thickness, and posterior corneal elevation, interocular symmetry in all these parameters was very high in this group of consecutive patients. Asymmetry of these interocular parameters may warrant repeat clinical testing for accuracy and may predict corneal abnormalities. Normative data on posterior cornea elevation is presented. This study points out potentially clinically important high interocular corneal symmetry data in simulated keratometry, corneal thickness, and posterior corneal elevation.