Clear Zone Size Research Articles

Short communication: A multispecies bacterial-based direct-fed microbial alleviates Salmonella invasion and supports in vitro epithelial integrity.

Managing bacterial infections is of great importance in livestock production, particularly those caused by Salmonella enterica serovars Typhimurium or Dublin, which can impact both animal health and performance, as well as human food safety. Direct-fed microbials (DFM) can support gastrointestinal function and alleviate the potential negative effects of bacterial infections. In the present study, the capacity of a multispecies bacterial-based DFM containing Ligilactobacillus (formerly Lactobacillus) animalis 506, Propionibacterium freudenreichii 507, Bacillus licheniformis 809, and B. subtilis 597 to reduce S. Typhimurium ATCC14028 invasion was investigated using a co-incubation model with the HT29-MTX-E12 cell line (Exp. 1). Next, a possible antagonistic effect of the DFM against S. Dublin ATCC 41286 was evaluated using an in vitro agar well diffusion method following a co-incubation of 48h (Exp. 2). At last, a series of experiments were performed to evaluate how different doses (6.25 × 106, 2.50 × 107, or 1.00 × 108 CFU/well) of the DFM would support the integrity of intestinal epithelial cells challenged or not with S. Typhimurium ATCC14028 or hydrogen peroxide under a transepithelial electrical resistance (TEER) assay with Caco-2 cells (Exp. 3 and 4). In Exp. 1, BDP significantly (P < 0.001) reduced by 90.8% the invasion of S. Typhimurium into HT29-MTX-E12 cells, whereas viability of the potentially harmful bacteria was reduced by 21.0% (P < 0.0001). In Exp. 2, the antagonistic properties of BDP towards S. Dublin were confirmed by the detection of a clear inhibition zone (size = 8.6mm). Lastly, without challenge, the lowest dose of the DFM (6.25 × 106 CFU) provided the greatest support on the cells (treatment × hour; P < 0.0001). However, when the cells were challenged with S. Typhimurium, all doses alleviated the loss of integrity caused by the pathogen (treatment × hour; P < 0.0001). In cells challenged with hydrogen peroxide, the greater dose (1.00 × 108 CFU) supported the cells for a longer period of time (treatment × hour; P < 0.0001). These in vitro findings set the stage for exploring the potential benefits of using a novel DFM as a promising tool and strategy to mitigate Salmonella enterica infections in ruminants and improve animal health, food safety, and public health. Further in vivo confirmation needs to be developed to validate these preliminary in vitro results.

Analysis of Amylase Activity in Bacteria Isolated from Hot Spring of Pentadio Resort

The hot spring of Pentadio Resort is one of the geothermal areas likely to be the place of bacteria or microorganisms that can produce amylolytic enzymes. This research aims to analyze bacteria in the Pentadio Resort hot springs that possess the potential to produce amylase enzymes, analyze the characteristics of bacterial isolates that produce amylase enzymes in Pentadio Resort hot springs and determine the types of bacteria that produce amylase enzymes in Pentadio Resort hot springs. The research employs a qualitative and descriptive method. The research involved several methods, including sample collection, media preparation, isolation and selection of thermophilic bacterial isolates, purification of thermophilic bacterial isolates, selection of isolates producing amylase enzymes, identification of selected isolates (motility test, biochemical test, gram staining), and molecular identification. The research yielded seven isolates, and isolate code A6 demonstrated the potential to produce amylase enzymes with a clear zone size of 23,26 mm, bacillus, gram positive, and positive motility. Subsequently, molecular identifidation was carried out in which, based on the results of phylogenetic tree reconstractiopisalate A6 was related to the bacteria Bacillus cereus strain MD 152, which belongs to the Bacillus cereus bacteria

Effectiveness of Gel from Andaliman Fruit (Zanthoxylum acanthopodium DC.) Extract on Wound Inflammation.

&lt;b&gt;Background and Objective:&lt;/b&gt; Pain is caused by damaged tissue on the outside or inside of an organ and it is regulated by chemicals. Synthetic drugs are used to ease pain because they are analgesics in the field of medicine. Traditional medicine is known to help people all over the world, in both rich and developing nations. The Andaliman fruit, or &lt;i&gt;Zanthoxylum acanthopodium&lt;/i&gt; DC., comes from a spice plant that grows naturally in Toba Regency, North Sumatra, Indonesia. This study aims to determine the formulation of the nanoherbal analgesic spray gel preparation of Andaliman fruit (&lt;i&gt;Zanthoxylum acanthopodium&lt;/i&gt; DC.) in terms of its effectiveness as a pain reliever. &lt;b&gt;Materials and Methods:&lt;/b&gt; There were three amounts of spray gel made, namely 5, 10 and 15% and tests were done to see how well they worked. &lt;i&gt;Staphylococcus aureus&lt;/i&gt; bacteria were used in the bacterial blocking test. To test how well painkillers worked, five groups of mice were used. Using a hot iron, tests for anti-inflammatory activity and wound healing were done. The tissue was then watched for 14 days and analysed using Hematoxylin and Eosin (H&E) stains. &lt;b&gt;Results:&lt;/b&gt; The 15% concentration reduces pain and the time it takes for the body to respond to it. The clear zone size is the same as (K&lt;sup&gt;+&lt;/sup&gt;) and it can lower the number of inflammatory cells and help wounds heal by adding fibroblast and collagen cells. These findings are supported by significant data results (p<0.05, p = 0.018). &lt;b&gt;Conclusion:&lt;/b&gt; Finally, analgesic gel spray made from the Andaliman fruit at a 15% concentration can help with pain and also be antibacterial, reduce inflammation and help wounds heal.&lt;/p&gt.

Antibacterial Activity and Molecular Identification of Soft Coral Sinularia sp. Symbiont Bacteria from Karimunjawa Island against Skin Pathogens Propionibacterium acnes and Staphylococcus epidermidis

Soft corals can produce bioactive compounds that act as antibacterials. Sinularia sp. is a soft coral that can produce antibacterial compounds. Symbion bacteria are bacteria that can produce bioactive compounds that tend to be the same as their host. The use of symbiont bacteria can be an alternative to exploit the potential of Sinularia sp. without harming marine life. This study aims to determine the antibacterial potential of the symbiont bacteria obtained from the soft coral Sinularia sp. in inhibiting the growth of Propionibacterium acnes and Staphylococcus epidermidis. The antibacterial activity test was carried out by the agar diffusion method using disc paper. Antibacterial activity was indicated by the formation of a clear zone around the disc paper. The results showed that LA7 isolate had the best antibacterial activity with an average clear zone size of 14.6 mm against Staphylococcus epidermidis and 16.6 mm against Propionibacterium acnes. LA7 isolates identified species based on the 16S rRNA gene with primers 27F and 1492R. Based on molecular species support, it was found that LA7 isolate is Bacillus aerius with a homology level of 98.17%.

Uji Potensi Antibakteri Ekstrak Kulit Jeruk Nipis Citrus aurantifolia (Christm) Swingle Terhadap Vibrio sp.

Lime (Citrus aurantifolia) is one of the herbal plants that is rich in benefits, especially as a herbal medicines. Besides of lime fruit, lime peel also has antibacterial properties such as essential oils which contain flavonoids which can inhibit bacterial growth. This research utilizes lime peel which will be extracted as a test material. The purpose of this research is to determine the antibacterial potential of lime peel extract against Vibrio sp. at various concentrations. This research used the well-diffusion method using MHA as a test medium to determine whether lime peel extract can inhibit the growth of Vibrio sp. Various concentrations and penicillin as a positive control used in this research to determine which concentration has a greatest potential for inhibiting the growth of Vibrio sp. Result of this study used qualitative analysis by comparing the clear zone size produced on the medium. The obtained result shown that 20%, 40%, 60%, 80% and 100% concentration of lime peel can forming a clear zone which mean they can inhibit the growth of Vibrio sp. The best concentration used to inhibit Vibrio sp. is 100% concentration which produce 23.7 mm clear zone on MHA medium. Lime peel extract can be used to inhibit Vibrio sp. growth based on the research result.

Karakterisasi Ekstrak Kurkumin dari Kunyit Putih (Kaemferia rotunda L.) dan Kunyit Kuning (Curcuma domestica Val.)

This study was aimed to identify the chemical characteristics of white and yellow turmeric powder, and to investigate the influence of both types with three different solvents on yield, total phenolic content, curcuminoid, antioxidant, and antibacterial activity of curcumin crude extract. The curcumin extraction was performed by maceration using N-hexane, ethyl acetate, and ethanol solvents. The results showed that the proximate analysis excluding carbohydrate content of white turmeric powder were lower compared to the yellow type. Curcumin crude extract of white turmeric powder had lower yield, total phenolic content, curcuminoid, antioxidant, and antibacterial activity compared to yellow turmeric extract. Moreover, turmeric extracted with ethyl acetate had higher total phenolic, curcuminoid, antioxidant, and antibacterial activity compared to turmeric extracted using N-hexane and ethanol. Based on the highest total phenolic (193.26 mg GAE/kg) and curcuminoid content (8.13 mg/L), the best treatment was yellow turmeric extract using ethyl acetate solvent. This treatment had the lowest IC50 (63.38 μg/ mL), and the highest clear zone size of S. aureus (6.59 mm) and E. coli (6.29 mm) at concentration of 2000 ppm.

Improvement of polyhydroxybutyrate (PHB) plate-based screening method for PHB degrading bacteria using cell-grown amorphous PHB and recovered by sodium dodecyl sulfate (SDS)

Poly(3-hydroxybutyrate) (PHB) is a biobased and biodegradable plastic. Considering the environmental issues of petroleum-based plastics, PHB is promising as it can be degraded in a relatively short time by bacteria to water and carbon dioxide. Substantial efforts have been made to identify PHB-degrading bacteria. To identify PHB-degrading bacteria, solid-based growth or clear zone assays using PHB as the sole carbon source are the easiest methods; however, PHB is difficult to dissolve and distribute evenly, and bacteria grow slowly on PHB plates. Here, we suggest an improved PHB plate assay using cell-grown PHB produced by Halomonas sp. and recovered by sodium dodecyl sulfate (SDS). Preparation using SDS resulted in evenly distributed PHB plates that could be used for sensitive depolymerase activity screening in less time compared with solvent-melted pellet or cell-grown PHB. With this method, we identified 15 new strains. One strain, Cutibacterium sp. SOL05 (98.4% 16S rRNA similarity to Cutibacterium acne), showed high PHB depolymerase activity in solid and liquid conditions. PHB degradation was confirmed by clear zone size, liquid culture, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results indicate this method can be used to easily identify PHB-degrading bacteria from various sources to strengthen the benefits of bioplastics.

Effect of Sanitizers and Disinfectants in Staphylococcus Saprophyticus

Background/Objectives: In the dental environment, handpiece or ultrasonic scaler used in treatment causes aerosols and various pathogenic microorganisms. Many types of pathogens cause infectious diseases. This study is to identify surface disinfectants suitable for the management of Staphylococcus saprophyticus bacterial species, one of the causes of infection in medical institutions to use them as standardized surface management resources for infection control in dental clinic.Method/Statistical Analysis: Commonly used 7 types of disinfectants were classified to select commercialized disinfectants. Samples were taken by rubbing the surface of the unit chair with a sterile swab. In order to check the bacterial species cultured in the medium, a single colony was purely separated by streaking. To identify the bacterial species, DNA was extracted from the bacteria and PCR was performed. the mean and standard deviation of each group. One-way ANOVA and Scheffe’s post-test were carried out to identify the clear zone of paper discs and significant differences between groups.Findings: The test for bacterial identification was carried out for the surface flora of the unit chair. As a result, S. saprophyticus was identified on the surface. According to the result of comparative analysis of the clear zone size of each disinfectant, sodium hypochlorite (NaOCl), a chlorine disinfectant was found to have the highest disinfection effect (8.52mm), followed by Distell, an ammonium compound disinfectant (2.72).Improvements/Applications: The result of the analysis of the clear zone of the disinfectant showed excellent antibacterial activity in 0.3% NaOCl and 0.5% Distel, indicating that they are disinfectants suitable for S. saprophyticus used in the study.

Isolation and Identification of Cellulolytic Bacteria from Soil Sample and Their Antibiogram

This investigation was focused to isolate and identify the effective cellulolytic soil inhabiting bacteria from the soil of waste disposal site of Noakhali Science and Technology University (NSTU) campus and Maijdee, Noakhali with evaluating their cellulase production ability. Eight cellulolytic bacteria were isolated and identified as potentially effective strain from thirty isolates of twenty samples and their antibiogram was also performed. In this investigation, the maximum carboxymethylcellulose hydrolysis capacities (HC value), for all the isolates, ranged from 1.40 to 2.18 mm whereas maximum clear zone size around the colony ranged from 4.0 mm to 10.0 mm. It was the indication of the highest cellulase production ability of these eight species by degrading cellulose where two isolates sample 2 (10-3) and sample 15 (10-3) displayed the maximum zone of clearance around the colony. The results also revealed that soil of the investigated area can be used, in near future, to produce cellulase enzyme which will be useful for industrial purposes, plant growth promotion and research. Antibiotic sensitivity test was used in the work to determine the sensitivity and resistance pattern of the isolates. The result reported several isolates resistance to commercially used antibiotics. The main reason of this bacterial resistance is the indiscriminate use of the antibiotics. From the microscopic examination, morphological characteristics and various biochemical tests, the isolates were identified as Bacillus spp, Bacillus cereus, Bacillus megaterium, Clostridium spp, Staphylococcus aureus, Actinomycetes spp, Pseudomonas aeruginosa, Acinetobacter spp.

Isolation and Characterization of Protease Producing Bacteria from Soil, in Arba Minch University, Abaya Campus

Microbes are ubiquitous and live in familiar settings such as soil, water, food and animal intestines as well as in more extreme setting such as rocks, glaciers, hot springs and deep-sea vents. They are essential component of the biodiversity as they account for 50% of the living biomass of this planet. The aim of this work was isolation and screening of protease producing bacteria from soil collected from the study area. Isolation of protease producing bacteria was performed by the serial dilution and spread plate technique using skim milk agar medium. Accordingly, 131 isolates were positive on skim milk agar and of which 13 (10%) of them are protease producer. Four best isolates were selected on the basis of their clear zone size, one from each site for further study. IS-4 has larger clear zone size with 10.5mm followed by IS-2 (6mm). All potential isolates have circular in shape of colony and flat in height of colony except IS-1 which is irregular and raised respectively. Most of potential isolates have opaque in their colonial optical density. All isolates were found to be Gram positive and spore producers. Morphological and biochemical results have revealed that three of four active enzyme producing bacteria are identified as Bacillus spp. Members of the genus Bacillus produce a large variety of extracellular enzymes (proteases) particularly significant for industrial application.

The influence of clear zone size and roadside vegetation on driver behavior

IntroductionRoadside vegetation provides numerous environmental and psychological benefits to drivers. Previous studies have shown that natural landscapes can effectively lower crash rates and cause less frustration and stress to the driver. However, run-off-the-road crashes resulting in a collision with a tree are twice as likely to result in a fatality, reinforcing the need to examine the placement of vegetation within the clear zone. MethodThis study explores the relationship between the size of the clear zone and the presence of roadside vegetation on vehicle speed and lateral position. A static evaluation, distributed electronically to 100 licensed drivers, was utilized to gather speed selections for both real and virtual roads containing four combinations of clear zone sizes and roadside vegetation densities. A case study was included in the static evaluation to investigate the presence of utility poles near the edge of the road on speed selection. Validation of the static evaluation was performed by a field data collection on the same roadways shown to participants in the evaluation. ResultsThe speeds observed in the field for roadways with medium clear zone/dense vegetation or large clear zone/spare vegetation correlated with the speeds chosen by static evaluation participants. Further field data were obtained on vehicle speeds and lateral positions for additional roads demonstrating the same clear zone size/vegetation density combinations. Practical applicationThis study successfully demonstrates the relationship between clear zone design and driver behavior, which could improve clear zone design practices and thus roadway safety.

Screening of xylanase activity of Streptomyces albidoflavus PSM-3n isolated from Uttarakhand

Background: Awareness towards the environmental pollution had made the evolution of green technology by which enzymes got special attention in industries. The enzymes replaced chemical catalysts in manufacturing various chemicals, agricultural and pharmaceutical products. Material and Methods: Actinomycetes were isolated and screened for their ability to produce xylanase. For the most promising isolate, selection of media, effect of pH, temperature, metal ions, and detergents on enzyme production and activity was studied. Results: Out of 29 isolates, 22 isolates showed xylanase activity. Out of 22 xylanase producing isolate, 05 isolates were selected for secondary screening on the basis of their clear zone size. The most promising isolate PSM-3n was identified as Streptomyces albidoflavus. It produces maximum enzyme (xylanase) in media Horikoshi and Ikura having carbon and nitrogen sources as oat meal and urea respectively. The optimum pH and temperature for the enzyme production was 4.0 and 45oC respectively. The enzyme activity was found maximum at temperature 50oC and enhanced in the presence of Fe3+ ions. There was a reduction in the enzyme activity in the presence of detergents like SDS, tween-20 and tween-80. The enzyme was fairly stable at 50°C for 1 h. Conclusions: The enzyme produced by the isolate PSM-3n is fairly heat stable and highly acid stable. The activity of the enzyme was increased in presence of Fe3+ ions while decreased in presence of SDS. Therefore, further studies are required for purification of xylanase for its application potential in pulp bioleaching processes and in the functional food industry.

Antagonistic effect of two isolates of Trichoderma harzianum against postharvest pathogens of tomato (Lycopersicon esculentum)

Pathogenicity test of all fungi (14 different isolates) isolated from both infected tomato fruits and the surface wash of other healthy fruits had different pathogenicity rates. The genus Rhizopus sp. was the most pathogenic one followed by Fusarium sp. Trichoderma harzianum isolates (T3 and T4) had a different pattern of antagonism against the tested pathogens. In dual plate test of the antagonistic action of T3 and T24 against the postharvest pathogens, clear zone size ranged between 1 and 4 and 3 and 6 mm by T3 and T24, respectively. The antagonists (T3 and T24) didn't show inhibition zone against Rhizopus sp., but they could overgrow it by 100% after 9 days of incubation. Mostly, all the other postharvest isolates showed high degree of overgrowth by T3 than T24. The two antagonists failed to overgrow Aspergillus species except for A. niger (3) which was overgrown by T3. Volatile and non-volatile metabolite tests indicated that mycelial growth of Penicillium stekii was significantly inhibited by T3 and T24 more than the other tested pathogens. The inhibition of A. niger (1) was 12% by non-volatile metabolites of T24 produced after 1 day incubation, and reached to 97% inhibition by the metabolites of 3 days. Interestingly, inhibition of Aspergillus sp. by volatile compounds of T3 and T24 was 2% and 20%, respectively, whereas the inhibition of the same pathogen by non-volatile compounds reached 75% and 87%, respectively. The results of slice assay clearly indicate that T. harzianum (T3 and T24) could provide a complete protection to tomato slices from the infection of the tested pathogens. After 3 days of incubation, Trichoderma suppressed the linear growth of these pathogens on tomato slices and the percentage of suppression was significant and ranged between 80 and 100%, except with Rhizopus sp. the suppression reached 33% only.

채소류 모잘록병균에 길항하는 Bacillus ehimensis YJ-37의 대량배양 최적조건

본 연구는 채소류 모잘록병균인 R. solani AG4에 길항하는 미생물 B. ehimensis YJ-37의 500<TEX>$m\ell$</TEX> 플라스크 배양, 5 <TEX>$\ell$</TEX> jar fermentor 배양, 2,000 <TEX>$\ell$</TEX> 대형탱크의 배양 조건 및 길항물질 생성능을 조사하였다. 500<TEX>$m\ell$</TEX> 플라스크 배양에서의 길항물질 최적생산조건은 1.5% starch, 0.6% peptone, 0.3% <TEX>$Na_2$</TEX>HP <TEX>$O_4$</TEX>, 0.15% MgC1<TEX>$_2$</TEX>, pH 8.0, 배양온도 32<TEX>$^{\circ}C$</TEX>, 배양시간 54시간으로 나타났고, 이때 미생물의 수는 1.42<TEX>$\times$</TEX><TEX>$10^{ 8}$</TEX> cfu/<TEX>$m\ell$</TEX>21g-DCW/<TEX>$\ell$</TEX>), 항진균 활성은 13.9mm로 나타났다. 5<TEX>$\ell$</TEX> jar fermenter 배양에서의 길항물질 최적생산조건은 플라스크배양에서의 최적 생산조건에서 공기주입량과 교반속도를 변화시켜 조사한 결과, 공기주입량 2 vvm, 교반속도 200 rpm, 배양시간 48시간 이후 미생물의 수와 균체의 량은 2.06 <TEX>$\times$</TEX> <TEX>$10^{8}$</TEX> cfu/<TEX>$m\ell$</TEX> 및 30g-DCW/<TEX>$\ell$</TEX>, 항진균 활성은 13.4 mm로 나타났다. 2,000 <TEX>$\ell$</TEX> 대형탱크 배양에서는 교반속도 200 rpm, 산소주입량 30 vvm으로 고정하고 10일간 배양하여 미생물의 생육 및 길항물질 생성능을 조사한 결과는 미생물의 수와 균체의 량은 0.81 <TEX>$\times$</TEX> <TEX>$10^{8}$</TEX> cfu/<TEX>$m\ell$</TEX>와 12g-DCW/<TEX>$\ell$</TEX>, 항진균 활성은 8.6mm로 나타나 5<TEX>$\ell$</TEX> jar fermenter 배양에 배해 균의 수는 1/10로 줄었으며 항진균 활성도 64%로 낮게 나타났다.다. The optimal culture conditions in 500<TEX>$m\ell$</TEX> flask suture, 5<TEX>$\ell$</TEX> jar fermenter and 2,000 <TEX>$\ell$</TEX> large stale culture were investigated to maximize the production of antibiotic on Rhizoctonia solani AC4, the causal agent of vegetables damping-off, by the strain Bacillus ehimensis YJ-37. Starch (1.5%) as a carbon source, peptone (0.6%) as a nitrogen source and MgC1<TEX>$_2$</TEX>(0.15%) as a metal ion in the medium containing N <TEX>$a_2$</TEX>HP <TEX>$O_4$</TEX>(0.3%) showed the highest production of the antibiotic(s) in a rotary shake (200 rpm). Optimal initial pH of the culture medium, culture temperature and culture time for the antibiotic(s) production were pH 8.0, 32<TEX>$^{\circ}C$</TEX> and 54hrs, respertively. Under the optimal renditions in flask culture, cell growth and antifungal activity (clear zone size) were 1.42 <TEX>$\times$</TEX> 10<TEX>$^{8}$</TEX> cfu/<TEX>$m\ell$</TEX> (21g-DCW/ <TEX>$\ell$</TEX>) and 13.9 mm, respectively. In 5 <TEX>$\ell$</TEX> jar fermenter (medium 3 <TEX>$\ell$</TEX>), optimal air flow, agitation speed and culture time for the antibiotic(s) production were 2 vvm, 200 rpm and 48hrs, respectively. Under the optimal conditions in 5 <TEX>$\ell$</TEX> jar fermenter, tell growth and antifungal activity were 2.06 <TEX>$\times$</TEX> 10<TEX>$^{8}$</TEX> cfu/<TEX>$m\ell$</TEX> (30g-DCW/ <TEX>$\ell$</TEX>) and 13.4 mm, respectively. Under the culture conditions of air flow (30 vvm) and agitation speed (200 rpm) at 32<TEX>$^{\circ}C$</TEX> for 10 days in 2,000 <TEX>$\ell$</TEX> large scale culture (medium 1,800 <TEX>$\ell$</TEX>, pH 8.0), cell growth and antifungal activity were 0.81<TEX>$\times$</TEX>10<TEX>$^{8}$</TEX> cfu/<TEX>$m\ell$</TEX> (12g-DCW/ <TEX>$\ell$</TEX>) and 8.6 mm, respectively.

Detection of extracellular bound proteinase in EPS-producing lactic acid bacteria cultures on skim milk agar.

Skim milk agar was developed to investigate extracellular cell-bound proteinase in yogurt cultures, Streptococcus thermophilus and Lactobacillus bulgaricus. The Lact. bulgaricus cultures produced more extracellular cell-bound proteinase than did Strep. thermophilus cultures. Strong positive correlations between the size of the exopolysaccharide (EPS) layer and extracellular cell-bound proteinase were found for both Streptococcus and Lactobacillus cultures. Strong positive linear relationships existed between the EPS size and colony size and the diameter of clear zone and colony size for Streptococcus cultures, whereas weak positive linear relationships were observed for Lactobacillus cultures. These data are useful to validate the relationship between extracellular proteinase and the EPS size of LAB. Also, a convenient medium to detect the presence of extracellular cell-bound proteinase of LAB is valuable for dairy industries.

Optical Modeling of Radial Keratotomy Incision Patterns

To determine the optical effects of higher-order corneal shape variations resulting from radial keratotomy. Videokeratoscopic height data were obtained postoperatively from several patients who had undergone radial keratotomy. For each of clear central zone sizes 3.00 mm, 4.00 mm, and 4.75 mm, two patients were chosen randomly from the larger study group. Data obtained 2 weeks postoperatively from these six patients were decomposed into the Zernike polynomials, and the low-order expansion terms were removed to disclose corneal height variations (the radial keratotomy artifact). The artifact was applied to a schematic eye model, and exact ray-tracing was used to evaluate visual performance, which was defined as a function of pupil diameter, optical zone (central clear zone) size, and radial keratotomy artifact centration. The radial keratotomy artifact degrades visual performance at midspatial frequencies more than it does at high spatial frequencies. This effect is most pronounced for smaller optical zones and for a pupil diameter of 4 mm. Visual performance remains nearly constant for small decentration (0.5 mm or less) of the radial keratotomy optical zone from the corneal apex. Residual refractive error, corneal asphericity, and the radial keratotomy artifact all affect visual performance after radial keratotomy. Isolated effects of the radial keratotomy artifact degrade visual performance, with the level of degradation dependent on pupil size, optical zone size, and centration of the procedure. More research is necessary to combine the radial keratotomy artifact with changes in corneal asphericity and to further quantify the optical effects of radial keratotomy.

Complications of Small Clear-zone Radial Keratotomy

To review the postoperative outcome of patients with radial keratotomy who have clear-zone diameters below 2.75 mm. A retrospective review was performed of all patients with radial keratotomy who have clear-zone diameters less than 2.75 mm presenting for consultation from August 1993-September 1995. Preoperative records and surgical reports were reviewed, and a thorough ophthalmic examination was performed. A total of 37 eyes had a clear-zone size below 2.25 mm. Six eyes were excluded from subsequent analysis due to keratoconus. The remaining 31 eyes had an average clear-zone size of 1.5 mm (standard deviation, 0.4 mm; range, 0.9-2.2 mm). Postoperative morbidity included severe disabling glare in 31 (100%) of 31 eyes, contact lens intolerance in 19 (100%) of the 19 eyes fitted, Snellen visual acuity loss (> 2 lines) in 25 (81%) of 31 eyes, inability to drive at night in 11 (69%) of 16 patients, moderate to severe diurnal visual fluctuation in 21 (68%) of 31 eyes, refractive undercorrection by greater than 1 diopter in 16 (52%) of 31 eyes, loss of employment in 4 (25%) of 16 patients, polyopia in 5 (16%) of 31 eyes, refractive overcorrection by greater than 1 diopter in 3 (10%) of 31 eyes, and a retinal detachment attributable to pilocarpine use in 1 (3%) of 31 eyes. Using radial keratotomy clear-zone diameters smaller than 2.25 mm has a high complication rate and is unsafe. Small clear-zone radial keratotomy should be abandoned. Although this study was limited to clear zones less than 2.25 mm, the authors endorse current recommendations that the clear zone should be at least 3.0 mm in diameter.

Analysis of Astigmatic Keratotomy With a 5.0-mm Optical Clear Zone

To investigate the surgically induced refractive change after astigmatic keratotomy with a 5.0-mm optical clear zone in patients with severe naturally occurring astigmatism. We analyzed surgically induced refractive change in 40 consecutive eyes undergoing astigmatic keratotomy with a 5.0-mm optical clear zone. The surgically induced refractive change was calculated according to the method of Holladay, Cravy, and Koch with some modifications. Eyes were divided into two groups: Group I included eyes with mixed astigmatism and a maximum preoperative spherical equivalent of +1.25 diopters that underwent arcuate keratotomy, and Group II included eyes with compound myopic or simple myopic astigmatism (maximum preoperative spherical equivalent of -3.00 diopters) or mixed astigmatism with low minus spherical equivalent that underwent four-incision radial keratotomy and arcuate keratotomy. After refractive surgery, all eyes experienced a reduction of astigmatism when examined three months or more after surgery. Only one eye from each group was overcorrected. The magnitude of refractive astigmatism of surgically induced refractive change was 3.25 +/- 0.90 diopters for eyes in Group I and 3.25 +/- 0.80 diopters for eyes in Group II. There was minimal axis deviation. Eyes in Group I had more flattening with the wound than steepening against the wound, with a coupling ratio of -0.86 +/- 0.36, whereas in Group II, there was flattening both with the wound and against the wound. The net effect of surgery (sum of the primary and secondary effects) was more flattening than steepening in Group I eyes, and flattening of the circumference of the eye in Group II. A decrease of one line of best-corrected visual acuity was observed in one (6.6%) of 15 eyes in Group I and in two (8%) of 25 eyes in Group II. A 5.0-mm optical clear zone arcuate keratotomy is an effective method for correcting moderate to severe naturally occurring astigmatism. Further investigation of this optical clear zone size on glare and contrast sensitivity testing is necessary and is underway.

The Combined (Genesis) Technique of Radial Keratotomy: A Prospective, Multicenter Study

Purpose: A prospective, multicenter, clinical study to evaluate a standardized surgical (Genesis) protocol which includes combined-technique radial incisions in patients seeking reduction of their physiologic myopia. The combined incisions were designed to incorporate the safety of the centrifugal incision technique with the efficacy of the centripetal incision technique.Methods: A total of 375 eyes undergoing radial keratotomy procedures performed in six different clinical centers were analyzed. All procedures were performed in accordance with the Genesis nomograms. The Genesis protocol called for using preoperative screening pachymetry to guide central clear zone size selection, incising the thinnest corneal quadrant first, suturing corneal perforations, and discouraged more than one enhancement procedure, when indicated. Globe fixation technique served as a study variable.Results: Mean follow-up was 6.2 months (range, 1.5-12 months). Mean residual cycloplegic refraction was -0.48 ± 0.61 diopters (D) (range, -2.50 to +1.50 D); 92% of eyes were within 1 D of the planned goal of -0.50 D and 85% were within 1 D of emmetropia; 14% were myopic; and 1 % was hyperopic by more than 1 D. Uncorrected visual acuity was 20/40 or better in 95% of eyes; the remaining 5% retaining myopic refractive errors. A single procedure was performed in 73% of eyes, and 99% received less than two enhancements. Of eyes with no enhancements, 97% had uncorrected visual acuity of 20/40 or better. One study eye (0.3%) had a two-line loss of spectacle visual acuity. There were no invasions of the central clear zone. Globe fixation was a significant predictor for enhancement incidence (P < 0.001) but not for perforation incidence (P = 0.06). Incision sequence was predictive for perforation incidence (P < 0.0002).Conclusion: The combined-technique of radial keratotomy, coupled with the Genesis surgical protocol, affords centrifugal incision safety with centripetal incision efficacy. The Genesis nomograms, with a built in refractive outcome goal of -0.50 D provide an acceptable degree of accuracy and predictability while guarding against hyperopic over-correction.

Aspheric Photorefractive Keratectomy With Excimer Laser

Increased spherical aberration of the cornea is a common finding after excimer laser keratorefractive keratectomy. The shape of the paracentral cornea is probably related to the incidence of side effects like glare and halos at night depending on ablation zone size and pupil diameter. Aspheric curvature changes of the paracentral cornea at the edge of the ablation may decrease those side effects. Fifteen patients were treated with photorefractive keratectomy for myopia correction with a Summit excimer laser (Summit Technology, Waltham, Mass), one eye using a standard spherical algorithm and the fellow eye using a new aspherical algorithm. Eyes were followed for 6 to 18 months. None of 15 patients reported halos in the aspherically corrected eye stronger than in the fellow eye, whereas five patients claimed stronger halos in the spherically corrected eye. The effective clear zone size was 3.16 +/- 0.35 mm in the spherical cases compared to 3.43 +/- 0.31 in the aspherical cases, although the same ablation zone diameters of 5 mm were used. This difference is highly statistically significant. Effective spherical aberration based on raytracing analysis of the central 5 mm of the corneal topographic maps was significantly smaller in the corneas with aspheric correction than in those with spheric corrections. These results indicate better optical homogeneity in eyes after aspheric photorefractive keratectomy for myopia compared to standard spherical corrections.