Visual outcomes of acute bacterial endophthalmitis treated with adjuvant intravitreal dexamethasone: A meta-analysis and systematic review.

Adjunctive treatment of bacterial endophthalmitis with intravitreal steroids is a topic of controversy among many ophthalmologists. The objective of this study is to evaluate the effects of intravitreal dexamethasone on the visual outcomes of patients with acute bacterial endophthalmitis through a systematic review and meta-analysis. A literature search of PubMed, Scopus, and Cochrane Library databases was performed to include studies on the visual outcomes of adjuvant intravitreal dexamethasone in patients with acute bacterial endophthalmitis. The review is based on the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) protocol. A total of 1545 articles met our search criteria and after further review, two randomized controlled trials and three retrospective case series were included in the final analysis. A total of 126 eyes were treated with intravitreal dexamethasone combined with antibiotics, and another 139 eyes were treated with antibiotics alone. All cases of endophthalmitis were post-operative or post-intravitreal injection, with pooled results demonstrating no visual benefit with supplementation of intravitreal dexamethasone. Our meta-analysis does not show any visual benefit from steroid supplementation and yet, considering a relatively small number of patients included in each study, larger randomized controlled trials are required to further clarify the role of steroids in the treatment of acute bacterial endophthalmitis.

Comparison of Ocular Biometric Parameters Between Hispanic and Non-Hispanic Ethnicities in White Adults Undergoing Cataract Surgery.

OBJECTIVES: To compare ocular biometric parameters between Hispanic and non-Hispanic White adult patients undergoing cataract surgery. METHODS: We included 433 adult patients undergoing surgery for senile cataract. Only patients with race and ethnicities of Hispanic and non-Hispanic White were included. The following parameters measured by the IOLMaster 700 were compared between Hispanic and non-Hispanic patients: mean keratometry, corneal astigmatism, anterior chamber depth (ACD), lens thickness, vitreous length, axial length, white-to-white diameter, and emmetropic intraocular lens power. RESULTS: There were 219 Hispanic patients and 214 non-Hispanic patients with a mean age of 70.1±7.7 years (range, 50-88 years), and 66.7% were women. Although sex distribution was similar between the two groups, Hispanic patients had a lower age compared with non-Hispanic patients (69.3±8.3 vs. 70.9±6.9 years, P=0.02). In biometric values, ACD was significantly lower in Hispanic patients (3.07±0.40 mm) than in non-Hispanic patients (3.16±0.37 mm, P=0.01). Such statistically significant difference persisted after adjustment for age and sex (P=0.01). No other significant differences were found in other ocular parameters measured. CONCLUSIONS: Anterior chamber depth is significantly shorter in Hispanic patients compared with non-Hispanic patients. Such ethnic difference should be considered when performing cataract and corneal surgeries because this ethnic difference may be associated with a higher risk of corneal endothelial injury.

Occurrence of Occult Neoplasia in Pterygium Specimens Among Hispanic and Non-Hispanic Patients.

PURPOSE: To determine the role of race and ethnicity in the prevalence of occult ocular surface squamous neoplasia in pterygium specimens. METHODS: This retrospective study reviewed pathology reports and medical records of 504 patients who underwent pterygium surgery in South Texas. Those with clinical signs of ocular surface squamous neoplasia were excluded. Clinical data including age, sex, and self-reported race and ethnicity were analyzed to determine risk factors for presence of occult ocular surface squamous neoplasia in pterygium specimens. RESULTS: There were 504 specimens; 95.8% were from patients identified as White, 1.8% from African Americans, and 2.4% from Asians. Ethnicity included Hispanic in 70.8% and non-Hispanic in 29.2%. Among all specimens, 18 (3.6%) were positive for occult ocular surface squamous neoplasia. The prevalence of occult ocular surface squamous neoplasia in pterygium specimens was higher in Hispanics compared to non-Hispanics (4.8% vs. 0.7%, respectively, p = .025). The prevalence of occult ocular surface squamous neoplasia in different races included 8.3% for Asians, 3.5% for Whites, and 0% for African Americans. However, the racial difference did not reach statistical significance (p = .57). There were also no statistically significant differences between those with or without occult ocular surface squamous neoplasia regarding age or sex. CONCLUSIONS: A significant but low rate of occult ocular surface squamous neoplasia was found in pterygium specimens. The percentage of those with ocular surface squamous neoplasia in pterygium specimens was significantly greater in Hispanics compared to non-Hispanics. As treatment and prognosis of pterygium and ocular surface squamous neoplasia differ, histopathologic evaluation of all pterygium specimens is warranted.

A review of filamentary keratitis.

Filamentary keratitis (FK) is characterized by the presence of filaments on the corneal surface that are often associated with symptoms of foreign body sensation, irritation, and eye pain. FK is associated with a variety of ocular and systemic conditions, most notably dry eye disease. These filaments are composed primarily of epithelium, mucus, and cellular debris; however, their pathogenesis remains an area of debate. Aggravating factors for FK include desiccation, inflammatory mediators, as well as eyelid mechanical forces. Management consists of addressing associated conditions, especially dry eye disease, and providing medical and procedural treatments to alleviate symptoms and restore the ocular surface. Mainstay treatments include filament removal, increased lubrication with artificial tears and punctal occlusion, hypertonic saline, antiinflammatory and mucolytic medications, and autologous serum eye drops, as well as bandage contact lenses. A stepwise approach is required to manage patients with acute or chronic FK. Prolonged therapy is often necessary to prevent recurrence of this bothersome condition.

The Effects of Hyperbaric Oxygen Therapy in Patients with Central Retinal Artery Occlusion: A Retrospective Study, Systematic Review, and Meta-analysis.

PURPOSE: Central retinal artery occlusion (CRAO) is a vision-threatening condition with a potentially poor visual prognosis. Many different treatment modalities are suggested but controversy remains regarding effectiveness of these treatments. The purpose of this study is to perform a systematic review and meta-analysis in addition to analyzing retrospective data at our own tertiary care center regarding effectiveness of hyperbaric oxygen therapy (HBOT) in treatment of CRAO. METHODS: The PubMed, Scopus, and the Cochrane Library are searched from the date of database inception to September 2021 to conduct a review based on the PRISMA (preferred reporting items for systematic review and meta-analysis), evaluating the role of HBOT in visual recovery of CRAO patients. In addition, a retrospective chart review of patients clinically diagnosed with CRAO at our university-based hospital (University of Texas Health, San Antonio, TX, USA) from year 2011 to 2021 was conducted. RESULTS: After a review of 376 articles, three articles met the inclusion criteria for meta-analysis, where a total of 207 patients received HBOT versus 89 patients that did not receive any form of oxygen therapy. Analysis of these results demonstrate that HBOT in CRAO patients does not enhance the final visual outcome (p = 0.83). Similar conclusion was also drawn from retrospective analysis of 48 patients (15 HBOT versus 33 controls) at our tertiary care center, where no visual benefit was observed in the HBOT group. CONCLUSIONS: HBOT does not appear to improve final visual outcome and concerns remain regarding adverse reactions such as barotrauma and generalized seizures. Large, randomized studies are required for further understanding of the role of HBOT in treatment of CRAO.

Superior limbic keratoconjunctivitis: a comprehensive review.

Superior limbic keratoconjunctivitis (SLK) is characterized by chronic inflammation of the superior limbus and superior bulbar and tarsal conjunctivae. Patients also often have fine punctate staining of the limbus and adjacent area, superior limbic proliferation seen as thickening of the limbal epithelium and surrounding conjunctiva, and occasionally filaments at the superior limbus and upper cornea. SLK frequently presents with ocular irritation, foreign body sensation, and photophobia. SLK can be associated with other ocular and non-ocular conditions, such as thyroid disease. Although the pathogenesis of SLK is still unknown, it is thought to be related to mechanical injury, tear film instability, or an autoimmune/inflammatory etiology. Many patients with SLK can be asymptomatic or have symptoms that resolve or remit spontaneously. For symptomatic SLK, patients are managed medically with treatments such as lubricants, topical anti-inflammatory or immunomodulatory medications, punctal occlusion, and bandage contact lenses. Patients with symptoms refractory to medical management may need surgical interventions. We detail the current literature on the epidemiology, clinical manifestations, associated conditions, histopathology, pathogenesis, and treatment of SLK.

Moraxella Keratitis: A Case Series.

OBJECTIVE: To report the ocular and systemic risk factors, clinical manifestations, and management outcomes of Moraxella keratitis. METHODS: This retrospective study included patients with culture-proven Moraxella keratitis in South Texas between 2012 and 2018. Clinical data including demographics, ocular and systemic risk factors, clinical presentation, speciation, and treatment course were collected. RESULTS: Fourteen eyes of 14 patients had culture-proven Moraxella keratitis which made up 8.1% of cases of culture-proven bacterial keratitis in the period studied. These included 10 men and 4 women with a mean age of 52.7±11.3 years. Ten patients (71.4%) had different ocular risk factors such as ocular trauma, corneal foreign body, contact lens use, preceding viral keratitis, neurotrophic cornea, and recent corneal transplant on topical steroids. Systemic risk factors included diabetes mellitus, systemic immunosuppressive therapy, cancer chemotherapy, and AIDS. There was no specific clinical manifestation. The size of stromal infiltration on initial presentation varied among the cases, with 71.4% stromal infiltrations of 4 mm or less. The patients were managed with fortified tobramycin, fortified vancomycin, and moxifloxacin eye drops. No eyes required surgical intervention during treatment for the active infection, except for one eye with pre-existing no light perception that was enucleated because of chronic pain. CONCLUSIONS: Moraxella keratitis is a less frequent form of bacterial keratitis that appears more prevalent in patients with previous ocular conditions. Early diagnosis of this infection and medical treatment with a conventional corneal ulcer regimen can result in good clinical outcomes without the need for a surgical intervention.

Protective Role of 360° Laser Retinopexy in Patients with Rhegmatogenous Retinal Detachment: a Systematic Review and Meta-analysis.

PURPOSE: Visual impairment from retinal re-detachment could be debilitating. The aim of this review is to evaluate the role of 360° laser retinopexy on success rate of rhegmatogenous retinal detachment (RRD) repair by a meta-analysis study. METHODS: The PubMed, Scopus, and the Cochrane Library databases were searched comprehensively from the date of database inception to January 2021, evaluating the role of 360° laser retinopexy in visual and anatomical success rate of RRD repair. This review was conducted based on the preferred reporting items for systematic review and meta-analysis (PRISMA) protocols. RESULTS: Among 202 articles screened for eligibility, six studies were found to be eligible for inclusion in our final analysis. Our meta-analysis demonstrates that prophylactic treatment with circumferential laser photocoagulation has no significant effect on the initial rate of retinal re-detachment or final best-corrected visual acuity following pars plana vitrectomy repair of RRD. Subgroup analysis of studies (n = 3) with 23-gauge pars plana vitrectomy, however, favors attachment rate in patients undergoing 360° prophylactic laser treatment. CONCLUSIONS: Three hundred and sixty degree laser retinopexy appears to have favorable outcomes in patients undergoing 23-gauge retinal detachment repair. This protective effect, however, is not apparent with inclusion of 20-gauge vitrectomy studies.

Giant papillary conjunctivitis: A review.

Giant papillary conjunctivitis (GPC), which is characterized by the development of "giant" papillae on the superior tarsal conjunctiva, is a common complication in contact lens wearers. This condition can be associated with excessive mucus production, itching, blurry vision, and diminished contact lens tolerance. Risk factors for GPC include non-disposable lenses, infrequent lens replacement, long wearing time, inadequate lens hygiene, and atopy. Although the exact pathophysiology of GPC remains incompletely understood, it likely develops from the combination of mechanical trauma to the superior tarsal conjunctiva and an immunologic response by the conjunctiva to deposits on the anterior surface of the contact lens. With proper management, GPC has an excellent prognosis. In mild cases, prompt contact lens cessation is sufficient for the resolution of signs and symptoms. For more severe cases, the use of topical anti-histaminic agents is indicated. Uncommonly, topical steroids, non-steroidal anti-inflammatory agents, immunomodulatory medications, or very rarely surgery may be needed. In this review article, we provide a comprehensive review of the available literature on GPC, with an emphasis on recent findings and treatment advances for this common condition.

Etiology and Risk Factors for Infectious Keratitis in South Texas.

PURPOSE: To determine the causative organisms and associated risk factors for infectious keratitis in South Texas. METHODS: This retrospective study was performed at a tertiary teaching hospital system in South Texas. Medical records of all patients who presented with infectious keratitis from 2012 to 2018 were reviewed. Only patients with culture-proven bacterial, fungal, and Acanthamoeba keratitis were included. RESULTS: In total, 182 eyes of 181 patients had culture-proven bacterial, fungal, or Acanthamoeba keratitis. The age of patients ranged from 3 to 93 years, with a mean of 48.3 ± 20.8 years. The most common etiologic agent was bacteria, with 173 bacterial cultures (95.1%) recovered, followed by 13 fungal cultures (7.1%), and 3 Acanthamoeba cultures (1.6%). Of the 218 bacterial isolates, coagulase-negative Staphylococcus was the most common (25.7%), followed by Pseudomonas aeruginosa (23.4%), Staphylococcus aureus (11.0%), and Moraxella (7.8%). Fusarium was the most common fungal isolate (46.2%). The most common risk factors for infectious keratitis included contact lens wear (32.4%), underlying corneal disease (17.6%), trauma (14.3%), and ocular surface disease (13.7%). CONCLUSIONS: Bacteria are the most common cause of infectious keratitis in this patient population, with coagulase-negative Staphylococcus and Pseudomonas as the most common isolates. The prevalence of culture-positive fungal keratitis is significantly lower than that of bacterial keratitis. Contact lens wear is the most common risk factor associated with infectious keratitis in South Texas.

Floppy eyelid syndrome: A comprehensive review.

Floppy eyelid syndrome (FES) is defined as eyelid hyperlaxity with reactive palpebral conjunctivitis. It is a common condition that can be associated with significant ocular irritation. FES presents with easily everted eyelids and chronic papillary conjunctivitis in the upper eyelids. It is frequently associated with ocular and systemic diseases, notably keratoconus and obstructive sleep apnea, respectively. This comprehensive review describes the epidemiology, pathological changes, proposed pathogenesis, clinical manifestations, and a variety of treatment options for this condition. Conservative treatment of FES includes aggressive lubrication, nighttime eye shield, and avoiding sleeping on the affected eye. Patients with FES and obstructive sleep apnea may have an improvement in their ocular signs and symptoms after long-term therapy with continuous positive airway pressure. In refractory cases, a corrective surgery that addresses the eyelid laxity can result in significant improvement. All patients with ocular irritation should be evaluated for the presence of FES.

Ocular Injuries Associated With Air-Powered Salt Guns.

This report discusses the potential ocular injuries associated with an air-powered salt gun, a new product that may appeal to children. The authors hope to inform both providers and patients of the potential risks and treatment considerations if an injury of this type is sustained. [J Pediatr Ophthalmol Strabismus. 2019;56:e65-e67.].

The science behind codes and standards for safe walkways: changes in level, stairways, stair handrails and slip resistance.

Walkway codes and standards are often created through consensus by committees based on a number of factors, including historical precedence, common practice, cost, and empirical data. The authors maintain that in the formulation of codes and standards that impact pedestrian safety, the results of pertinent scientific research should be given significant weight. This article examines many elements of common walkway codes and standards related to changes in level, stairways, stair handrails, and slip resistance. It identifies which portions are based on or supported by empirical data; and which could benefit from additional scientific research. This article identifies areas in which additional research, codes, and standards may be beneficial to enhance pedestrian safety.

Interplay effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc quality assurance.

The purpose of this study is to investigate an effect of angular dependence and calibration field size of MapCHECK 2 on RapidArc QA for 6, 8, 10, and 15 MV. The angular dependence was investigated by comparing MapCHECK 2 measurements in MapPHAN-MC2 to the corresponding Eclipse calculations every 10° using 10× 10 cm2 and 3 × 3 cm2 fields. Fourteen patients were selected to make RapidArc plans using the four energies, and verification plans were delivered to two phantom setups: MapCHECK 2/MapPHAN phantom (MapPHAN QA) and MapCHECK 2 on an isocentric mounting fixture (IMF QA). Migration of MapCHECK 2 on IMF was simulated by splitting arcs every 10° and displacing an isocenter of each partial arc in the Eclipse system (IMFACTUAL QA). To investigate the effect of calibration field size, MapCHECK 2 was calibrated by two field sizes (10 × 10 cm2 and 3 × 3 cm2) and applied to all QA measurements. The γ test was implemented using criteria of 1%/1 mm, 2%/2 mm, and 3%/3 mm. A mean dose of all compared points for each plan was compared with respect to a mean effective field size of the RapidArc plan. The angular dependence was considerably high at gantry angles of 90° ± 10° and 270° ± 10° (for 10 × 10/3 × 3 cm2 at 90°, 30.6% ± 6.6%/33.4%± 5.8% (6 MV), 17.3% ± 5.3%/15.0% ± 6.8% (8 MV), 8.9%± 2.9%/7.8% ± 3.2% (10 MV), and 2.2% ± 2.3%/-1.3% ± 2.6% (15 MV)). For 6 MV, the angular dependence significantly deteriorated the γ passing rate for plans of large field size in MapPHAN QA (< 90% using 3%/3 mm); however, these plans passed the γ test in IMFACTUAL QA (> 95%). The different calibration field sizes did not make any significant dose difference for both MapPHAN QA and IMFACTUAL QA. For 8, 10, and 15 MV, the angular dependence does not make any clinically meaningful impact on MapPHAN QA. Both MapPHAN QA and IMFACTUAL QA presented clinically acceptable γ passing rates using 3%/3 mm. MapPHAN QA showed better passing rates than IMFACTUAL QA for the tighter criteria. The 10 × 10 cm2 calibration showed better agreement for plans of small effective field size (< 5 × 5 cm2) in MapPHAN QA. There was no statistical difference between IMF QA and IMFACTUAL QA. In conclusion, MapPHAN QA is not recommended for plans of large field size, especially for 6 MV, and MapCHECK2 should be calibrated using a field size similar to a mean effective field size of a RapidArc plan for better agreement for IMF QA.

Choroidal blood flow decreases with age: an MRI study.

PURPOSE: To verify that a visual fixation protocol with cued eye blinks achieves sufficient stability for magnetic resonance imaging (MRI) blood-flow measurements and to determine if choroidal blood flow (ChBF) changes with age in humans. METHODS: The visual fixation stability achievable during an MRI scan was measured in five normal subjects using an eye-tracking camera outside the MRI scanner. Subjects were instructed to blink immediately after recorded MRI sound cues but to otherwise maintain stable visual fixation on a small target. Using this fixation protocol, ChBF was measured with MRI using a 3 Tesla clinical scanner in 17 normal subjects (24-68 years old). Arterial and intraocular pressures (IOP) were measured to calculate perfusion pressure in the same subjects. RESULTS: The mean temporal fluctuations (standard deviation) of the horizontal and vertical displacements were 29 ± 9 µm and 38 ± 11 µm within individual fixation periods, and 50 ± 34 µm and 48 ± 19 µm across different fixation periods. The absolute displacements were 67 ± 31 µm and 81 ± 26 µm. ChBF was negatively correlated with age (R = -0.7, p = 0.003), declining 2.7 ml/100 ml/min per year. There were no significant correlations between ChBF versus perfusion pressure, arterial pressure, or IOP. There were also no significant correlations between age versus perfusion pressure, arterial pressure, or IOP. Multiple regression analysis indicated that age was the only measured independent variable that was significantly correlated with ChBF (p = 0.03). CONCLUSIONS: The visual fixation protocol with cued eye blinks was effective in achieving sufficient stability for MRI measurements. ChBF had a significant negative correlation with age.

Impact of DNA damaging agents on genome-wide transcriptional profiles in two marine Synechococcus species.

Marine microorganisms, particularly those residing in coastal areas, may come in contact with any number of chemicals of environmental or xenobiotic origin. The sensitivity and response of marine cyanobacteria to such chemicals is, at present, poorly understood. We have looked at the transcriptional response of well characterized Synechococcus open ocean (WH8102) and coastal (CC9311) isolates to two DNA damaging agents, mitomycin C and ethidium bromide, using whole-genome expression microarrays. The coastal strain showed differential regulation of a larger proportion of its genome following "shock" treatment with each agent. Many of the orthologous genes in these strains, including those encoding sensor kinases, showed different transcriptional responses, with the CC9311 genes more likely to show significant changes in both treatments. While the overall response of each strain was considerably different, there were distinct transcriptional responses common to both strains observed for each DNA damaging agent, linked to the mode of action of each chemical. In both CC9311 and WH8102 there was evidence of SOS response induction under mitomycin C treatment, with genes recA, lexA and umuC significantly upregulated in this experiment but not under ethidium bromide treatment. Conversely, ethidium bromide treatment tended to result in upregulation of the DNA-directed RNA polymerase genes, not observed following mitomycin C treatment. Interestingly, a large number of genes residing on putative genomic island regions of each genome also showed significant upregulation under one or both chemical treatments.

Evolution and metabolic significance of the urea cycle in photosynthetic diatoms.

Diatoms dominate the biomass of phytoplankton in nutrient-rich conditions and form the basis of some of the world's most productive marine food webs. The diatom nuclear genome contains genes with bacterial and plastid origins as well as genes of the secondary endosymbiotic host (the exosymbiont), yet little is known about the relative contribution of each gene group to diatom metabolism. Here we show that the exosymbiont-derived ornithine-urea cycle, which is similar to that of metazoans but is absent in green algae and plants, facilitates rapid recovery from prolonged nitrogen limitation. RNA-interference-mediated knockdown of a mitochondrial carbamoyl phosphate synthase impairs the response of nitrogen-limited diatoms to nitrogen addition. Metabolomic analyses indicate that intermediates in the ornithine-urea cycle are particularly depleted and that both the tricarboxylic acid cycle and the glutamine synthetase/glutamate synthase cycles are linked directly with the ornithine-urea cycle. Several other depleted metabolites are generated from ornithine-urea cycle intermediates by the products of genes laterally acquired from bacteria. This metabolic coupling of bacterial- and exosymbiont-derived proteins seems to be fundamental to diatom physiology because the compounds affected include the major diatom osmolyte proline and the precursors for long-chain polyamines required for silica precipitation during cell wall formation. So far, the ornithine-urea cycle is only known for its essential role in the removal of fixed nitrogen in metazoans. In diatoms, this cycle serves as a distribution and repackaging hub for inorganic carbon and nitrogen and contributes significantly to the metabolic response of diatoms to episodic nitrogen availability. The diatom ornithine-urea cycle therefore represents a key pathway for anaplerotic carbon fixation into nitrogenous compounds that are essential for diatom growth and for the contribution of diatoms to marine productivity.

Cerebral microvascular rarefaction induced by whole brain radiation is reversible by systemic hypoxia in mice.

Whole brain radiation therapy (WBRT) leads to cognitive impairment in 40-50% of brain tumor survivors following treatment. Although the etiology of cognitive deficits post-WBRT remains unclear, vascular rarefaction appears to be an important component of these impairments. In this study, we assessed the effects of WBRT on the cerebrovasculature and the effects of systemic hypoxia as a potential mechanism to reverse the microvascular rarefaction. Transgenic mice expressing green fluorescent protein driven by the Acta2 (smooth muscle actin) promoter for blood vessel visualization were randomly assigned to control or radiated groups. Animals received a clinical series of 4.5 Gy WBRT two times weekly for 4 wk followed by 1 mo of recovery. Subsequently, mice were subjected to 11% (hypoxia) or 21% (normoxia) oxygen for 1 mo. Capillary density in subregions of the hippocampus revealed profound vascular rarefaction that persisted despite local tissue hypoxia. Nevertheless, systemic hypoxia was capable of completely restoring cerebrovascular density. Thus hippocampal microvascular rarefaction post-WBRT is not capable of stimulating angiogenesis and can be reversed by chronic systemic hypoxia. Our results indicate a potential shift in sensitivity to angiogenic stimuli and/or the existence of an independent pathway of regulating cerebral microvasculature.

Clinical implementation of an empirical method for electron output factor determination.

The objective of this work has been to develop and implement an empirical calculation method for the determination of clinical electron output factors. Electron beams with various energies, field sizes, and source to surface distances using cutouts of varying radii were used to measure dose output at the depth of maximum dose in water. A 30 cm x 30 cm x 17.8 cm water equivalent phantom with a 0.125 cc cylindrical ion-chamber (PTW Model 31010) was used. The calculation model predicted the output factor as a product of the cone factor, radius dependent cutout factor, the effective source to surface distance factor and the area dependent aspect ratio factor. A comparative analysis of clinical cutout output factors, determined through both empirical calculation and direct measurement was performed to evaluate the clinical viability of the calculation method before its implementation in our clinic. A total of 643 output factors for 294 different cutout shapes were determined through both traditional measurement and predictive calculation. Predictive calculation differed from definitive measurement by at most 3.5% for all cases, a majority of cases falling within 1%. The method developed successfully predicts electron output factors on the basis of cutout geometry with accuracy better than 96% for all cases and better then 98% for most cases. This ability holds true for all practical SSD, electron energy, cone, and irregular shape combinations. The method has been clinically implemented and in use at our center since 2007.