Prevention Of Haze Research Articles

Haze Management Competition and Industrial Green Transformation

To clarify the relationship between haze management competition and industrial green transformation, this paper is based on the theoretical perspectives of local government competition and environmental federalism, the specific form of haze governance competition is analyzed by applying the two-region spatial Durbin model, and then the impact of haze governance competition on industrial green transformation and its transmission mechanism is explored by constructing a spatial panel linkage model and adopting the generalized spatial three-stage least squares method. The empirical results show that, with the profound changes in the performance appraisal system since the 18th National Congress, the interaction of environmental governance strategies between geographically adjacent provinces is imitative. In contrast, that which is between economically adjacent provinces is a “race to the top”, and haze governance is conducive to promoting the development of industrial green transformation. Further research found that the competition of haze governance is heterogeneous, and smog control in the eastern region contributes to the green transformation of local industries, while smog control in the central and western regions inhibits their industrial green transformation, and haze governance mainly enhances industrial green transformation through the innovation compensation effect, the human capital effect, and the industrial structure optimization effect. Therefore, the central government should carry out overall planning for the industry, and local governments should strengthen the joint prevention and control of haze and promote technological innovation, to improve environmental quality and realize high-quality economic development.

Phenolic-Degrading Enzymes: Effect on Haze Active Phenols and Chill Haze in India Pale Ale Beer.

The development of green and sustainable biotechnological approaches for preventing chill haze formation is currently under investigation. In this preliminary study, laccase and tannase (pure or combined) were applied as phenolic-degrading enzymes during two crucial brewing steps (i. post-mashing and ii. before the yeast inoculum). In post-mashing and irrespective of the dosage applied (100 μL/L or 1 mL/L), tannase-based treatment ensured the complete removal of haze active (HA) phenols, which was proved by the full prevention of chill haze (about 1 EBC vs. 22 EBC in the control sample). Before yeast inoculum for the alcoholic fermentation, the removal of haze active phenols and the prevention of chill haze were both tannase-dosage-dependent (15 and 2 EBC for the lowest and the highest dosages, respectively) although they failed to completely break down the HA phenols. This biotechnological approach did not significantly affect the chromatic properties of treated beer.

Effect of Prophylactic Mitomycin C on Corneal Endothelium Following Transepithelial Photorefractive Keratectomy in Myopic Patients.

PurposeThis study investigated the effect of prophylactic mitomycin C (MMC) on corneal endothelium to inhibit corneal haze formation post transepithelial photorefractive keratectomy (T-PRK).MethodsA total of 120 eyes of 60 patients with low, moderate, and high myopia were subjected to T-PRK with intraoperative application of MMC (0.02%) for 30–50s. Patients’ files were categorized into three groups according to ablation depths (if ≥100 µm) during T-PRK as follows: (1) Group A – low myopia without MMC, (2) Group B – low myopia with MMC, and (3) Group C – moderate/high myopia with MMC. Preoperative/surgical parameters and refractive outcomes were documented. Cell density (CD), number of cells (NUM), coefficient of variation, central corneal thickness (CCT), hexagonality (HEX/6A), average cell area (AVG), and its standard deviation (SD) were evaluated using specular microscopy preoperatively and postoperatively.ResultsOverall, 119 out of 120 eyes showed significant prevention of corneal haze. Groups A and C showed no significant changes in endothelial CD and NUM. Group B showed a non-significant reduction in CD. However, all three groups showed significant variations in HEX/6A, CCT, AVG, and SD.ConclusionThe MMC application did not significantly affect corneal endothelial density or number and can be used safely and effectively to prevent corneal haze following T-PRK in myopia.

Efficacy of mitomycin C 0.02% for prevention of haze after transepithelial photorefractive keratectomy for mild and moderate myopia

Objective: To investigate the efficacy of mitomycin C (MMC) 0.02% for prevention of haze after transepithelial photorefractive keratectomy (Trans-PRK) for mild and moderate myopia. Methods: Retrospective cohort study. We reviewed medical records of 295 patients (588 eyes) who underwent Trans-PRK with or without use of MMC. There were 45 patients (90 eyes) in the mild myopia group (aged between 18 and 41 years; 37 males and 8 females; myopia diopter <3.00 D) and 250 patients (498 eyes) in the moderate myopia group (aged between 18 and 46 years; 168 males and 82 females; myopia diopter: 3.00 to 6.00 D). The two groups were divided into subgroups with MMC 0.02% and without MMC, respectively. The time of intraoperative application of MMC, if there was, was 15 s and 30 s in the mild myopia group and the moderate myopia group, respectively. The mean follow-up time was 6 months. Postoperative best corrected visual acuity (BCVA), spherical equivalent (SE) and haze were analyzed and compared using an independent Student t-test or Mann-Whitney U test between subgroups. Haze variables were compared using chi-square statistics. Results: Haze was quantified with Fantes from grade 0.5 to 4. In the mild myopia group, all haze grades were 0.5 within 3 months. The incidence of haze was 6.25% (2/32) in eyes treated with MMC and 8.62% (5/58) in eyes treated without MMC; there was no statistical significance (χ²=0.00, P>0.999). In the moderate myopia group, the incidence of haze was 9.19% (24/261) in eyes treated with MMC within 3 months; the grade was 0.5 in 91.67% (22/24) of eyes with haze and 1 in 8.33% (2/24). The incidence of haze was 29.53% (70/237) in eyes treated without MMC; the grade was 0.5 in 60.00% (42/70) of eyes with haze, 1 in 18.57% (13/70), and 2 in 5.71% (4/70) within 3 months, and 0.5 in 15.71% (11/70) after 3 months (χ²=12.36, P=0.002). In the mild myopia group, BCVA was 5.0(5.0, 5.1) versus 5.0(5.0, 5.1) in the subgroups with MMC and without MMC (Z=-0.34, P=0.733). In the moderate myopia group, BCVA was 5.0(5.0, 5.1) versus 5.0(5.0, 5.1) in the subgroups with and without MMC (Z=-2.05, P=0.040). In the mild myopia group, SE was (0.33±1.07) D versus (0.32±0.57) D in the subgroups with and without MMC (t=0.25, P=0.805). In the moderate myopia group, SE was (0.66±0.85) D versus (0.53±0.67) D in the subgroups with and without MMC (t=2.97, P=0.003). Conclusions: MMC 0.02% was effective in preventing haze after Trans-PRK in the treatment of moderate myopia. However, it was not effective in mild myopia.

Relationship between the Formation of PM2.5 and Meteorological Factors in Northern China: The Periodic Characteristics of Wavelet Analysis

China’s rapid urbanisation and industrialisation have led to frequent haze in China in recent years. Although many measures to control haze have been implemented, no significant improvement has been observed, and haze still exists. In this study, we used wavelet transform to investigate the changes in PM2.5 on the time scale, the relationship amongst meteorological factors, and the causes and changes in haze formation and take measures to prevent haze. Results indicated the following: (1) The peak of PM2.5 changes in winter in the past three years primarily occurred in the range from 11:00 to 13:00 and 20:00 to 22:00. (2) Multiple cycles of daily average PM2.5 concentrations existed in 3–5 d, 6–14 d, 6–21 d, and 16–27 d, with a significant oscillation in 6–14 d and stable cycle characteristics. (3) The meteorological factors promoted the formation of haze to a certain extent. When haze occurred, the near-surface wind speed was only 1 m/s, which was not conducive to the spread of pollutants. (4) The formation of haze was affected by the interaction of various factors; the photochemical reactions of NO2 and O3 also exacerbated the formation of pollutants. This study provided a clear direction for the prevention and prediction of haze. Furthermore, the government must take relevant measures to reduce pollutant emissions and ensure the air quality of cities in winter.

Effect of Autologous Serum Eye Drops on Corneal Haze after Corneal Cross-linking.

Corneal haze remains a frequent post-operative finding in patients undergoing corneal cross-linking. It has been shown that autologous serum tears promote epithelial healing and reduce post-operative pain; however, the role in the prevention of corneal haze has not been reported. This study aimed to compare the effect of autologous serum tears versus preservative-free artificial tears on the prevention and resolution of post-cross-linking corneal haze. A retrospective cohort study was conducted in a sample population from one surgeon at a tertiary eye center from 2016 to 2019. Seventy-six eyes of consecutive patients who underwent cross-linking were included. Records were reviewed for corneal Scheimpflug densitometry values and maximum keratometry, epithelial healing time, and the use of either autologous serum tears or preservative-free artificial tears. Corneal densitometry values, expressed in standardized grayscale units (GSU), were recorded for the anterior 150-μm corneal stroma and in the 0.0 to 2.0 mm and 2.0 to 6.0 mm zones. Forty-four eyes received autologous serum tears, whereas 32 eyes received preservative-free artificial tears. The baseline GSU of the anterior stromal 0 to 2 mm annulus and the 2 to 6 mm annulus did not significantly differ between groups (P = .50 and P = .40, respectively). There was a statistically significant increase in mean GSU for both anterior 0 to 2 mm and 2 to 6 mm zones between baseline and 1 month (P < .001) and 3 months (P < .001). When comparing the two groups, no statistically significant difference was found post-operatively between the mean GSU at 1 month for the anterior 0 to 2 mm (P = .38) nor the 2 to 6 mm zone (P = .12), or for the third month (P = .60 and P = .44, respectively). Using Scheimpflug densitometry, we did not find a significant difference in the post-cross-linking corneal haze at 1 and 3 post-operative months between patients who use autologous serum tears and those who use preservative-free artificial tears.

The Dilemma and Countermeasures of Legal Control of Atmospheric Haze and Smoke Dust Pollution

Smoke dust is an important factor leading to haze pollution. There is no doubt about the serious impact of smoke dust pollution on public health, life and economic development. A consensus has been reached on the use of legal means to control smoke dust pollution. However, the existing laws still have too many problems to deal with the increasingly complex smoke dust pollution. It is a must to change the regulatory objects of the current “Air Pollution Prevention and Control Law (APPC Law)”, speed up the establishment of a regional joint prevention and control legal system, and establish local characteristic legislation in accordance with local conditions. We need establish a “three-in-one” legal system for the prevention and control of atmospheric haze and smoke dust pollution with “APPC Law” at the top, local legislations at the bottom and regional joint prevention and control law in the middle.

Mitomycin C for the prevention of corneal haze in photorefractive keratectomy: a meta-analysis and trial sequential analysis.

To evaluate the anti-haze effect and visual outcome after intraoperative mitomycin C (MMC) use during photorefractive keratectomy (PRK) in myopia or myopic astigmatism patients. We searched in PubMed, EMBASE, Cochrane Library and Google Scholar comprehensively to obtain studies comparing the clinical effects after PRK with and without MMC published until February 2020. Meta-analysis of primary outcome (corneal haze rate) and secondary outcomes [predictability, efficacy, safety and corneal endothelial cell density (ECD)] were conducted. We used trial sequential analysis (TSA) in an effort to collect firm evidence supporting our conclusion. Of the included 11 randomized controlled trials, five cohort and one case-control studies, 3536 eyes (2232 and 1304 in the MMC and control groups, respectively) were enrolled for meta-analysis. The TSA disclosed strong evidence of decline in corneal haze rate in the MMC group compared with that of the control group. In the subgroup analysis of duration, MMC seemed to reduce corneal haze rate in early-onset and late-onset haze. Predictability of refraction and visual acuity were greater in the MMC groups, not significantly though. The proportion of patients losing at least two lines of best corrected visual acuity postoperatively in the MMC groups was lower than that in the control groups. The corneal postoperative ECD showed no significant difference between the MMC and control groups. Our meta-analysis revealed that MMC is an important anti-haze agent in PRK for reducing both early- and late-onset haze and can also help improving predictability of refraction and subjective postoperative visual acuity.

Evaluation and sensitivity analysis of the ecosystem service functions of haze absorption by green space based on its quality in China

Evaluation of the ecosystem service functions of haze absorption by green space is important for controlling haze. In this study, the ecosystem service functions of haze absorption by green space in China in 2001, 2004, 2007, 2010, 2013, 2016 and 2018 are analyzed based on green space quality and sensitivity using a geographic information system (GIS) and Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. The results showed that the benchmark ecosystem service functions of haze absorption by green space when considering only the area of green space showed a trend that increases first and then decreases in 2001–2018, with 9000458.55 million Kg, 9145110.75 million Kg and 7734526.75 million Kg in 2001, 2013 and 2018, respectively. However, the corrected functions based on green space quality were 7724215.34 million Kg, 8320301.79 million Kg and 6510132.55 million Kg in the corresponding years. This indicated large differences between ecosystem service functions of haze absorption based on the quality and area of green space; only considering the area of green space to evaluate ecosystem service functions will result in overestimation. In terms of the spatial distribution of the ecosystem service functions of haze absorption by green space, there were greater differences in the benchmark and corrected functions, and the spatial distributions of the maximum, intermediate and minimum ecosystem service functions were notably different. However, the benchmark and corrected functions all showed a consistent trend in the rank of their contribution rates and ecosystem service functions as well as consistent distribution trends: the spatial distribution of ecosystem service functions of haze absorption by green space was very different in the same year, but there was little difference among different years. The change coefficients for the ecosystem service functions of haze absorption by arable land and grass land remained stable, whereas the coefficient of sensitivity for forest cover was elastic. Patch density (PD) and the ecosystem service functions of SO2 absorption, NOx absorption, dust retention and total ecosystem services showed a significant negative correlation, with correlation coefficients of -0.407, -0.511, -.330 and -0.332, respectively. In contrast, the area-weighted mean shape index (SAPE_AM) and ecosystem service functions exhibited significant positive relationships with correlation coefficients of 0.650, 0.634, 0.568 and 0.570, respectively. The results provide an improved method for evaluating the ecosystem service functions of haze absorption by green space as well as a reference for the prevention and control of haze and the coordinated development of regional societies, the economy and the environment.

Association of the Haze and Diabetes in China

China, as the largest developing country in the world, has experienced rapid economic development during the past decades. As a side effect of the rapid growth of Chinese economy, air pollution in the form of haze is harmful to human health. China is also one of the countries with the highest prevalence of diabetes in Asia and has the largest burden of diabetes in the world. Recent evidence suggests a positive correlation between air pollution and the increased risk of diabetes. However, the association of haze with diabetes is still unclear. Based upon literature searching with PubMed, the information on haze and prevalence of diabetes in different cities or provinces of China is summarized. The possible association of haze with diabetes and the perspectives of haze research particularly in the prevention of haze in China are then discussed. The exposure of long-term air pollution such as haze reduces insulin-dependent glucose uptake, leading to insulin resistance; damages beta cell function, leading to decreased insulin secretion, and promotes subcutaneous fat accumulation. Pathophysiological effects of particulate matters in diabetes through inflammation and oxidative stress were evidenced by several epidemiological and experimental studies. A better understanding of the incidence of diabetes caused by haze exposure may facilitate policy development in air pollution prevention and intervention design in diabetes prevention. Continuous improvement in air quality may help to reduce diabetes prevalence in China.

Development and testing of the reliability and validity of the adolescent haze related knowledge awareness assessment scale (AHRKAAS)

BackgroundHaze leads to many direct serious public health impacts. Understanding haze related knowledge can not only help adolescents organize health protection awareness to prevent the harmful effects that haze has on the body, but also promote their normal growth and development.MethodsBy considering, as the theoretical basis, the reasons behind the formation of haze and the underlying mechanisms of the diseases that it causes, in addition to also investigating extensive literature references, our research team developed the Adolescent Haze Related Knowledge Awareness Assessment Scale (AHRKAAS-I). After 6 experts reviewed AHRKAAS-I, and 6 adolescents tested the scale, the research team further revised and improved AHRKAAS-I to form AHRKAAS-II. After which, researchers randomly selected 2 districts from the 20 districts of Baoding, and subsequently randomly selected 2 middle schools from these 2 districts. Conducting a stratified cluster sampling method, considering class as a unit, the research team randomly selected 22 classes. Finally, a total of 1100 adolescents were investigated and 1034 valid questionnaires were recovered. By analyzing the data of 1034 valid questionnaires, the researchers tested the reliability and validity of the scale and obtained the final scale (AHRKAAS).ResultsAHRKAAS Cronbach’s α=0.923, content validity = 0.940, criterion validity = 0.444, and factor cumulative contribution rate = 66.178% by exploratory factor analysis. Using confirmatory factor analysis, Chi square value = 662.780, degrees of freedom = 242, Chi square value/degrees of freedom = 2.739, root-mean-square error of approximation = 0.049, goodness of fit index = 0.929, adjusted goodness of fit index = 0.905, comparative fit index = 0.964, normed fit index = 0.944, and Tueker-Lewis index = 0.955. AHRKAAS consisted of 25 items and 4 dimensions.ConclusionAHRKAAS with a good reliability and validity can be used to assess the cognition level of haze related knowledge among the adolescents, help medical workers and coordinators in schools when conducting targeted behavior interventions. Furthermore, it can be used for health guidance for adolescents relating to the health prevention of haze.

Mitomycin C for prevention of postoperative haze following excimer laser surface ablation in moderate to high myopia

Reason for withdrawal from publication The protocol is out of date and does not meet the current methodological standards of Cochrane.

Progress in corneal wound healing.

Corneal wound healing is a complex process involving cell death, migration, proliferation, differentiation, and extracellular matrix remodeling. Many similarities are observed in the healing processes of corneal epithelial, stromal and endothelial cells, as well as cell-specific differences. Corneal epithelial healing largely depends on limbal stem cells and remodeling of the basement membrane. During stromal healing, keratocytes get transformed to motile and contractile myofibroblasts largely due to activation of transforming growth factor-β (TGF-β) system. Endothelial cells heal mostly by migration and spreading, with cell proliferation playing a secondary role. In the last decade, many aspects of wound healing process in different parts of the cornea have been elucidated, and some new therapeutic approaches have emerged. The concept of limbal stem cells received rigorous experimental corroboration, with new markers uncovered and new treatment options including gene and microRNA therapy tested in experimental systems. Transplantation of limbal stem cell-enriched cultures for efficient re-epithelialization in stem cell deficiency and corneal injuries has become reality in clinical setting. Mediators and course of events during stromal healing have been detailed, and new treatment regimens including gene (decorin) and stem cell therapy for excessive healing have been designed. This is a very important advance given the popularity of various refractive surgeries entailing stromal wound healing. Successful surgical ways of replacing the diseased endothelium have been clinically tested, and new approaches to accelerate endothelial healing and suppress endothelial-mesenchymal transformation have been proposed including Rho kinase (ROCK) inhibitor eye drops and gene therapy to activate TGF-β inhibitor SMAD7. Promising new technologies with potential for corneal wound healing manipulation including microRNA, induced pluripotent stem cells to generate corneal epithelium, and nanocarriers for corneal drug delivery are discussed. Attention is also paid to problems in wound healing understanding and treatment, such as lack of specific epithelial stem cell markers, reliable identification of stem cells, efficient prevention of haze and stromal scar formation, lack of data on wound regulating microRNAs in keratocytes and endothelial cells, as well as virtual lack of targeted systems for drug and gene delivery to select corneal cells.

Mitomycin C application in refractive surgery

Over the years, mitomycin C has been used by refractive surgeons to prophylactically decrease haze after surface ablation procedures and therapeutically in the treatment of preexisting haze. Development of mitomycin C treatments has had a significant role in the revival of surface ablation techniques. We reviewed the literature regarding mechanism of action of mitomycin C, its role in modulating wound healing after refractive surgery, and its safety and efficacy as adjuvant therapy applied after primary photorefractive keratectomy surgery or after photorefractive keratectomy re-treatment after laser in situ keratomileusis and other corneal surgeries and disorders. The drug is a potent mitotic inhibitor that effectively blocks keratocyte activation, proliferation, and myofibroblast differentiation. Many studies have suggested that mitomycin C is safe and effective in doses used by anterior surface surgeons, although there continue to be concerns regarding long-term safety. After initial depletion of anterior keratocytes, keratocyte density seems to return to normal 6 to12 months after the use of mitomycin C when corneas are examined with the confocal microscope. Most clinical studies found no difference between preoperative and postoperative corneal endothelial cell densities when mitomycin C 0.02% was applied during refractive surgery,with exposure time of 2 minutes or less. After approximately 14 years of use, mitomycin C has been found to be effective when used for prevention and treatment of corneal haze.

Mitomycin C: Biological Effects and Use in Refractive Surgery

To provide an overview of the safety and efficacy of mitomycin C (MMC) as adjuvant therapy after refractive surgery procedures. Literature review. Over the past 10 years, MMC has been used by refractive surgeons to prophylactically decrease haze after surface ablation procedures and therapeutically in the treatment of preexisting haze. Development of MMC treatments has had a significant role in the revival of surface ablation techniques. We reviewed the literature regarding mechanism of action of MMC, its role in modulating wound healing after refractive surgery, and its safety and efficacy as adjuvant therapy applied after primary photorefractive keratectomy surgery or after photorefractive keratectomy re-treatment after laser in situ keratomileusis and other corneal surgeries and disorders. The drug is a potent mitotic inhibitor that effectively blocks keratocyte activation, proliferation, and myofibroblast differentiation. Many studies have suggested that MMC is safe and effective in doses used by anterior surface surgeons, although there continue to be concerns regarding long-term safety. After initial depletion of anterior keratocytes, keratocyte density seems to return to normal 6 to 12 months after the use of MMC when corneas are examined with the confocal microscope. Most clinical studies found no difference between preoperative and postoperative corneal endothelial cell densities when MMC 0.02% was applied during refractive surgery, with exposure time of 2 minutes or less. After more than 10 years of use, MMC has been found to be effective when used for prevention and treatment of corneal haze. Questions remain regarding optimal treatment parameters and long-term safety.

Новый метод профилактики и лечения субэпителиального флера роговой оболочки после эксимерлазерной коррекции миопии: 1 год наблюдения

Новый метод профилактики и лечения субэпителиального флера роговой оболочки после эксимерлазерной коррекции миопии: 1 год наблюдения

Mitomycin C in Photorefractive Keratectomy

To evaluate the outcome of primary or retreatment photorefractive keratectomy (PRK) or phototherapeutic keratectomy (PTK) with mitomycin C (MMC) 0.02% applied prophylactically intraoperatively for the prevention of haze and regression in cases of significant haze and regression after primary PRK, due to previous radial keratotomy (RK), in primary PRK eyes with high myopia, and in comeas with a previous superficial foreign body scar. This was a retrospective evaluation of 34 eyes treated with PRK or PTK and intraoperative MMC. Mitomycin C was applied immediately after laser ablation. Postoperative examinations were conducted 3 and 7 days after surgery and monthly for 6 months. Haze was graded on a standard 0+ (clear cornea) to 4+ (total opacity) scale. Visual acuity was measured as a general baseline indicator. Postoperatively, uncorrected visual acuity (UCVA) was 20/20 or better in 21 eyes and 20/25 in 5 eyes with best spectacle-corrected visual acuity (BSCVA) of 20/20 or better. Three eyes achieved UCVA of 20/30 with BSCVA of 20/20 or better; and 5 eyes had UCVA of 20/40 with BSCVA of 20/20 or better. Nineteen (56%) eyes had grade 0+ haze and 15 (44%) eyes had grade 0.5+ haze (trace haze) at 6-month follow-up. Mitomycin C 0.02% used prophylactically during PRK or PTK retreatment was effective in preventing significant recurrent haze from developing. In eyes with high myopia or previous RK or scarring, MMC was effective in preventing significant haze formation.

Prevention and Treatment of Haze in Refractive Surgery

Prevention and Treatment of Haze in Refractive Surgery

Comparison of Standard (0.02%) and Low Dose (0.002%) Mitomycin C in the Prevention of Corneal Haze Following Surface Ablation for Myopia

To retrospectively compare the safety and efficacy of lower dose mitomycin C (MMC) (0.002%) to that of the standard dose (0.02%) in eyes treated with photorefractive keratectomy (PRK) for myopia. The clinical efficacy of 95 eyes receiving myopic PRK with a standard concentration of MMC (0.02%) is sequentially compared to 126 eyes receiving low dose MMC (0.002%). The topical exposure times for MMC varied between 30 seconds and 2 minutes in both groups, and direct contralateral eye comparison of these two exposure times was analyzed in a prospective subset of 39 patients from among the low dose group. Patients were examined preoperatively and postoperatively at 1, 3, 6-9, and 9-12 months. Haze, visual acuity, and efficacy ratio outcomes were analyzed. The preoperative findings were overall statistically similar, except for higher spherical equivalent refractive error (P = .007) and best spectacle-corrected visual acuity (P = .007) in the standard MMC group. Postoperatively, haze levels ranged from 0 to 4+. With multivariable analysis, significantly less haze was noted among the standard dose MMC eyes for high myopia and higher ablation depth at all postoperative time points. In contrast, the haze levels were statistically similar for moderate myopia and lower ablation depths at the latter postoperative time points. The subset of contralateral eyes randomly receiving low dose MMC (0.002%) at either 30 seconds or 2 minutes exposure showed no significant difference in haze between these exposure times. The standard concentration of topical MMC (0.02%) is more effective than low dose MMC (0.002%) in preventing postoperative haze following surface ablation for myopia > or = -6.00 D and deeper ablation depth > or = 75 microm. However, for moderate myopia and shallow depth, low dosing appears to be equally effective. The duration of MMC exposure appears to be less important than its concentration.

Comparison of Laser Epithelial Keratomileusis With and Without Mitomycin C for Wavefront Customized Surface Ablations

To investigate the efficacy of mitomycin C (MMC) in preventing haze formation in surface wavefront customized ablations with successful refractive treatment (laser epithelial keratomileusis [LASEK]) and to evaluate the safety of this technique on corneal stroma and endothelium. This study was a prospective, double-masked, randomized clinical trial involving 52 eyes (30 placebo and 22 MMC) of 26 patients. The manifest refractive spherical equivalent (MRSE), best spectacle-corrected visual acuity, uncorrected visual acuity, corneal pachymetry, topography, aberrometry, endothelial specular microscopy, contrast sensitivity, corneal confocal microscopy, and complaints of pain via a subjective questionnaire were recorded preoperatively and 90 days postoperatively. The mean MRSE at 90 days postoperatively was -0.56 diopters (D) (-4.95 +/- 1.85 D, range: -8.00 to -1.62 D) for the MMC group and -0.49 D (-4.51 +/- 1.81 D, range: -7.75 to -2.25 D) for the placebo group. Higher order aberrations were similar between the placebo and MMC groups 90 days postoperatively (0.538 +/- 0.228 microm and 0.478 +/- 0.134 microm, respectively). Analysis of the endothelial cell count indicated a statistically significant decrease in endothelial cell density (P = .017) after LASEK, independent of MMC use. The predictability of the final target refraction, induction of high order aberrations, and improvement in contrast sensitivity proved that the use of MMC was equally safe when compared to procedures that did not use MMC. In addition, the procedure was efficient in the prevention of corneal haze.