Comparison of the effect of removing bandage contact lens on the days 3 and 5 following photorefractive keratectomy.

AIM: To compare the outcomes of removing bandage contact lens (BCL) on days 3 and 5 after photorefractive keratectomy (PRK). METHODS: One hundred patients who underwent PRK (a total of 200 eyes) were enrolled in the present study. The subjects were assigned to two groups. Group 1 consisted of the right eyes of subjects and bandage contact lenses removal were on the 3rd day; Group 2 consisted of the fellow eyes of same subjects and removed bandage contact lenses on the 5th day after PRK. Then, data obtained from both groups were compared. To evaluate complications, the subjects underwent a slit-lamp examination in all visits. RESULTS: Filamentary keratitis was observed in one eye in both groups. The frequency of haze was higher in group 1; however, it was not significant between the two groups. Using mixed model analysis, significant differences were observed in the rate of complications as well as pain and eye discomfort scores between the groups (P < 0.05). No major complication was reported. CONCLUSION: Majority of post-PRK corneal epithelial defect is healed on day 3. However, keeping BCL for 5 days postoperatively instead of the three days produces a slightly lower rate of total complication.

Safety and Efficacy of Oral Supplementation of Lentil (Lens culinaris Medic) in Dry Eye Patients.

OBJECTIVE: To evaluate the safety and efficacy of dietary lentil capsules in patients suffering from dry eye symptoms. METHODS: A randomized, triple-blind, interventional, placebo-controlled study was done. Sixty patients were randomized in two groups to receive either one capsule containing 500 mg of lentil powder or placebo daily for 3 months. UCVA, tear film breakup time (TBUT), Schirmer's test, tear film osmolarity, and OSDI score were recorded at baseline and 3 months after intervention. Data analysis was performed using IBM SPSS for Windows version 20 (SPSS, Chicago, IL, USA). RESULTS: In the lentil group, at baseline, the mean UCVA (LogMAR), OSDI, TBUT (S), tear film osmolarity (mOsm/L), and Schirmer (mm) scores were 0.104 (0.026), 22.66 (19.40), 10.31 (5.32), 301.07 (15.57), and 8.22 (6.87), respectively. These values were 0.101 (0.026), 20.85 (19.44), 13.04 (7.11), 299.81 (11.60), and 9.87 (10.11). In the placebo group, these values were 0.084 (0.027), 25.35 (20.08), 10.56 (4.95), 299.77 (15.09), and 9.35 (8.06) at baseline and 3 months later were 0.077 (0.027), 23.32 (22.90), 13.62 (6.30), 297.54 (12.08), and 8.64 (9.60), respectively. Three patients (one in the lentil group and two in the placebo group) experienced severe gastrointestinal symptoms. CONCLUSION: Although consumption of 500 mg of lentil is safe, this amount is not sufficient for reduction of dry eye syndrome in 3 months. For more validation, a clinical study with increased dosage of lentil is proposed.

An analytical enrichment-based review of structural genetic studies on keratoconus.

Keratoconus is a progressive bilateral corneal protrusion that leads to irregular astigmatism and impairment of vision. Keratoconus is an etiologically heterogeneous corneal dystrophy and both environmental and genetic factors play a role in its etiopathogenesis. In this analytical review, we have studied all the genes that are structurally associated with keratoconus and have tried to explain the function of each gene and its association with other eye disorders in a concise way. In addition, using gene set enrichment analysis, it was attempted to find the most important impaired metabolic pathways in keratoconus. Several genetic studies have been carried out on keratoconus and several genes have been identified as risk factors involved in the etiology of the disease. In the current study, 16 studies, including nine association studies, five genome-wide association studies, one linkage study, and one meta-analysis, were reviewed and based on the 19 genes found, enrichment was performed and the most important metabolic pathways involved in the disease were identified. The enrichment results indicated that the two pathways, interleukin 1 processing and assembly of collagen fibrils, are significantly associated with the disease. Obviously, the results of this study, in addition to providing information about the genes involved in the disease, can provide an integrated insight into the gene-based etiology of keratoconus and therapeutic opportunities thereof.

A Study of Corneal Biomechanics in Delayed-Onset Mustard Gas Keratopathy Compared to Cases With Corneal Scarring and Normal Corneas.

PURPOSE: This study compares the corneal biomechanical properties, as measured with Corvis ST, in three groups of cases with delayed-onset mustard gas keratopathy (DMGK), chronic corneal scarring (CCS), and those with normal corneas. METHODS: Forty-five eyes were enrolled in the DMGK, CCS, and normal groups (15 eyes each). All patients were examined with the slitlamp and Corvis ST. Extracted corneal biomechanical parameters included first and second applanation time (AT1, AT2), first and second applanation length (AL1, AL2), first and second applanation velocity (AV1, AV2), deformation amplitude (DA), highest concavity time, peak distance, highest concavity radius (HCR), central corneal thickness, corrected intraocular pressure (IOP), and noncorrected IOP. RESULTS: The mean age of the participants in the DMGK, CCS, and normal groups was 49.20±5.16, 60.40±22.92, and 44.60±8.32 years, respectively. Comparison between DMGK and CCS groups showed significant differences in AT1, AT2, corrected IOP, and noncorrected IOP. There were also significant differences in AT1, AT2, HCR, DA, and noncorrected IOP between the DMGK and normal groups. None of the parameters were significantly different between the CCS and normal groups. CONCLUSION: There seems to be reduced corneal rigidity and stiffness in cases exposed to mustard gas, which causes the cornea in the DMGK group to become applanated more easily and take longer to rebound compared with the other two groups. Also, IOP was lower than normal in the DMGK group, and thus, misdiagnosis of glaucoma is likely for these patients.

Efficacy of systemic diclofenac sodium on intravitreal concentration.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs), as an alternative, are replacing corticosteroids in ocular inflammatory diseases. Diclofenac has been used mainly topically, and recent focus has been on intravitreal delivery. Both of these methods have been shown to have complications in long-term application. PURPOSE: To assess the efficacy of slow release oral diclofenac sodium on intravitreal concentration in experimental model of chemically injured eyes. METHODS: In an experimental double-masked clinical trial, right eyes of 24 albino rabbits were chemically injured by 1 N NaOH. One hour after chemical injury, 10 cc suspension gavage containing 100 mg slow release diclofenac sodium was administered in all cases. 2, 4, 6, 12, 24, 48 h after gavage, vitreous samples were obtained in all cases. Intravitreal concentration of diclofenac sodium was evaluated in all samples using high-performance liquid chromatography (HPLC) method. RESULTS: Intravitreal diclofenac levels by oral intake were enhanced by the inflammation in all the measurements. In inflamed eyes, diclofenac concentration was ten times more than control eye (2.658 ± 0.344 vs. 0.242 ± 0.0279 and 1.617 ± 0.527 vs. 0.148 ± 0.095; in 2 and 4 h, respectively). After 6 h, diclofenac concentration was statistically different, although it reduced below 1 µg/ml. CONCLUSION: Diclofenac is delivered to the inflamed eye more than healthy eye. It seems that by oral diclofenac consumption, it is possible to make a significant intravitreal concentration.

Proteomic features of delayed ocular symptoms caused by exposure to sulfur mustard: As studied by protein profiling of corneal epithelium.

Exposure to mustard gas can lead to variations in the proteome of corneal epithelium cells and after a latency period produces delayed symptoms in the eyes of chemical victims. Hence, a comparative proteome analysis was conducted between the corneal epithelial cells of chemical victims from Iran-Iraq war (1980-1988) and healthy donors. To this end, corneal epithelium samples from victims and healthy individuals were collected, and the proteome of these samples were prepared for two-dimensional electrophoresis and the analysis of spots by statistical software. Selected spots were further analyzed by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry. Twenty four proteins were identified of which eighteen proteins showed downregulation while six proteins were upregulated in the victims in comparison to the normal individuals. Also, six protein spots were confirmed by western-blot analysis. In conclusion, all the twenty-four identified proteins are involved in pathways which their up- or down-regulation leads to the accumulation of undesired substrates, cell death and apoptosis. Bioinformatics' tools indicated that these identified proteins were involved in various metabolic processes, DNA damage response, immune response and etc. The present study provides a suitable platform for further clinical studies.

Increasing proteome coverage for gel-based human tear proteome maps: towards a more comprehensive profiling.

In situations where the molecular mechanism of many ocular disorders is unknown, owing to the difficulties associated with sampling from ocular tissues, human tear film can be a promising medium in ophthalmic research. The present study demonstrates an in-depth gel-based proteome optimization survey to approach more appropriate and efficient systems in various situations such as normal and dry-eye syndromes. Therefore, systematic and statistical evaluations were performed on different preparation methods, including acetone, acetone-methanol, chloroform-methanol-water, trichloroacetic acid (TCA)-acetone, tri-n-butylphosphate-acetone-methanol precipitations and ammonium sulfate fractionation at three different percentages of saturations (50, 70 and 90%). Methods were compared quantitatively on both one- and two-dimensional patterns. Some important parameters such as total protein recovery yield, densitometric analysis of some protein contaminants, banding patterns and total spot numbers along with statistical models for proper clustering were considered. Findings revealed noticeable impacts of preparation methods on all aspects of gel-based separations as well as recovery yield (ranging from 5.29 ± 0.96 to 22.56 ± 1.77 µg/mm) and banding and pattern resolution. In addition to all these, the most important point is that the total protein spot number on the final two-dimensional patterns (varied from 528.00 ± 19.00 to 657.00 ± 21.52 for different methods) were also noticeably increased in comparison with previously published reports (maximum of 250 spots), which is essential for a more comprehensive analysis. Increasing the proteome coverage in the present study is supposed to originate from improved solubility and effective rehydration during the sample application and isoelectric focusing (IEF) procedure along with proper sample preparation.

Enhanced reproducibility of the human gel-based tear proteome maps in the presence of di-(2-hydroxyethyl) disulfide.

Patterns obtained in two-dimensional gel electrophoresis (2-DE) in the previously published articles suggest a varying number of proteins. To seek the cause of this variation, we investigated the effect of reduction power on the overall tear proteome maps. To this end, the buffers of two reducing agents, dithiothreitol (DTT) at nine different concentrations and di-(2-hydroxyethyl) disulfide (HED), were examined. The assay showed that HED clearly improved 2-DE resolution, increased the number of detectable protein spots, and offered well-resolved chain regions in comparison with those treated with DTT. Furthermore, this study introduced increasing the reduction power as a remedy to increase the reproducibility of two-dimensional human tear proteome maps. In addition, the results of our assessment showed that improved reduction efficiency was accompanied by increased procedure reproducibility from 42% to 89%.

Possible long term effects of chemical warfare using visual evoked potentials.

Some studies have already addressed the effects of occupational organic solvent exposure on the visually evoked potentials (VEPs). Visual system is an important target for Sulphur Mustard (SM) toxicity. A number of Iranian victims of Sulphur Mustard (SM) agent were apprehensive about the delay effect of SM on their vision and a possible delay effect of SM on their visual cortex. This investigation was performed on 34 individuals with a history of chemical exposure and a control group of 15 normal people. The Toennies electro-diagnosis device was used and its signals were saved as the latencies. The mean of N75, N140 and P100 of victims of chemical warfare (VCWs) and control group indicated no significant results (P>0.05). The VCWs did not show any visual symptoms and there was no clear deficit in their VEPs.

Systemic complications of trinitrotoluene (TNT) in exposed workers.

INTRODUCTION: 2,4,6-trinitrotoluene (TNT) has been widely used as an explosive. TNT can induce some well-recognized toxic impacts comprising toxic hepatitis, aplastic anemia and cataract. The aim of study was evaluation of TNT exposed workers for systemic complication. METHODS: In a cross-sectional study, we carried out Liver Function Test (LFT), complete blood count (CBC) and slit lamp biomicroscopy to compare the prevalence and severity of these 3 complications between 47 male TNT exposed workers (with at least one year continuous experience of TNT exposure) and 43 unexposed male hospital worker who hadn't had any previous contacts with TNT. We also performed Pulmonary Function Test (PFT) to assess the probable obstructive/restrictive abnormalities, caused by TNT. RESULTS: Mean alkaline phosphatase (ALP) level of TNT exposed group was significantly higher than the unexposed group (p = 0.023) Forced Expiratory Volume in one second to Forced Vital Capacity (FEV1/FVC) ratios of both groups were in the range of restrictive pattern (82.03% and 81.42% for the exposed and unexposed group, respectively) with no meaningful difference. We didn't find out any specific TNT induced cataract and general cortical cataract (CC) and nuclear sclerotic cataract (NSC) prevalence was not significantly different. DISCUSSION: we haven't found TNT as a chemical, causing toxic hepatitis or aplastic anemia; neither did we find it as a compound, responsible for a meaningful increase in cataract prevalence. However, due to the increased ALP serum levels and FEV1/FVC ratios among TNT workers, safety precautions are advised.

The Effect of Amniotic Membrane Extracted Eye Drop on Repairing The Corneal Epithelial in Patients after Trans-Epithelial Photorefractive Keratectomy: An Interventional and Historical Study.

OBJECTIVE: Recent studies imply extensive applications for the human amniotic membrane (hAM) and its extract in medicine and ophthalmology. The content of hAM meets many requirements in eye surgeries, such as refractive surgery as the most important and commonly used method for treating the dramatically increasing refractive errors. However, they are associated with complications such as corneal haziness and corneal ulcer. This study was designed to evaluate the impact of amniotic membrane extracted eye drop (AMEED) on Trans-PRK surgery complications. MATERIALS AND METHODS: This randomized controlled trial was performed during two years (July 1, 2019-September 1, 2020). Thirty-two patients (64 eyes), including 17 females and 15 males, aged 20 to 50 years (mean age of 29.59 ± 6.51) with spherical equivalent between -5 to -1.5 underwent Trans Epithelial Photorefractive Keratectomy (Trans-PRK) surgery. One eye was selected per case (case group) and the other eye was considered as control. Randomization was done using the random allocation rule. The case group was treated with AMEED, and the artificial tear drop every 4 hours. The control eyes received artificial tear drops instilled every 4 hours. The evaluation continued for three days after the Trans-PRK surgery. RESULTS: A significant decrease in CED size was found in the AMEED group on the second day after surgery (P=0.046). Also, this group had a substantial reduction in pain, hyperemia, and haziness. CONCLUSION: This study showed that AMEED drop can increase the healing rate of corneal epithelial lesions after Trans- PRK surgery and reduce the early and late complications of Trans-PRK surgery. Researchers and Ophthalmologists should consider AMEED as a selection in patients with persistent corneal epithelial defects and patients who have difficulty in corneal epithelial healing. We understood AMEED has a different effect on the cornea after surgery; therefore, the researcher must know AMEED's exact ingredients and help expand AMEED uses (registration number: TCTR20230306001).

Tear total protein analysis in patients with late sulfur mustard-induced ocular complications: a cross-sectional study.

BACKGROUND: Eyes are the most sensitive organs to sulfur mustard (SM). Late ocular complications have been reported even 15-20 years post-exposure. To date, no study has investigated the composition of tear proteins in tear samples of SM-intoxicated patients. METHODS: Total protein content as well as concentrations of vascular endothelial growth factor (VEGF), calcitonin gene related peptide (CGRP) and substance P were measured in unstimulated tears of chemically-injured patients who suffer from late ocular complications of SM. These levels were compared to corresponding values obtained from tears of healthy control subjects. The concentration of total proteins was measured using the Bradford method and those of VEGF, CGRP and substance P by ELISA. RESULTS: Total protein concentration was significantly lower in tears of the SM compared to control group (p<0.01). In contrast, tear samples of the SM group had significantly higher VEGF and VEGF/total protein compared to control group (p<0.01). Tear CGRP concentration was found to be lower in the SM vs. control group (p<0.05) but no significant difference in CGRP/total protein was observed (p>0.05). Finally, tear substance P concentrations were not found to be significantly different between the two groups (p>0.05). CONCLUSION: The results of this investigation indicated decreased total protein and CGRP, and elevated VEGF concentration in tears of SM-intoxicated patients who suffer from chronic ocular complications.

Long-term results of MyoRing implantation in patients with keratoconus.

Clinical relevance: This study was conducted to evaluate five-year outcomes of MyoRing implantation in patients with keratoconus. The results showed that MyoRing implantation is a minimally invasive procedure and is safe and effective for improving visual acuity and refraction in most patients with keratoconus.Background: The long-term effects of MyoRing implantation on corneal features were studied.Methods: A total of 48 keratoconic eyes of 43 consecutive patients who had undergone MyoRing implantation using the Pocket Maker microkeratome (Dioptex, gmbh, Linz, Austria) and who had completed five years of follow­ups were included in this retrospective study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction and keratometry (K) readings were measured and assessed pre-operation, and five years post-operatively. As well, post-operation satisfaction was assessed using a validated questionnaire.Results: Five years post-operatively, there was a significant improvement in UDVA, CDVA, K readings, spherical equivalent (SE), and manifest sphere and cylinder (p < 0.001). Mean UDVA was 1.20 logMAR before the surgery and 0.42 after the surgery (p < 0.001). Mean CDVA was 0.63 logMAR before the surgery and 0.20 logMAR after the surgery (p < 0.001). SE was improved from -6.53 dioptres (D) before the surgery to -2.23 D after the surgery (p < 0.001). Moreover, the results show that the mean K was reduced by 2.82 D after the surgery (p = 0.001). Overall, 81% of patients were moderately to highly satisfied five years after surgery.Conclusion: MyoRing implantation was found to be a minimally invasive procedure, and is safe and effective for improving visual acuity and refraction in most patients with keratoconus.

Long-term pulmonary complications of chemical warfare agent exposure in Iraqi Kurdish civilians.

The Iraqi government used a range of chemical weapons, including blistering and nerve agents, against Iraqi Kurdish civilians in the 1980s. Few data exist about the long-term respiratory consequences of this exposure. In this study, Kurdish subjects with a history of exposure to chemical weapons were invited to attend a clinical assessment, including a review of their history, physical examination, and a high-resolution computed tomography (CT) of the thorax. Blistering at the time of exposure was used to define significant exposure to mustard gas. Results were compared between two groups of blistering and nonblistering. Four hundred seventy-nine subjects were studied; 45.7% male and 54.3% female. The mean age and standard deviation (mean +/- SD) of the cases was 43.1 +/- 13.7. Spirometry was abnormal in 15.2% of subjects and air trapping was present on CT scan in 46.6% and did not differ between patients with (n = 278) or without a history of blistering. Respiratory symptoms, including dyspnea, cough, and sputum production, were more common in subjects with a history of blistering (all p < .005) and blistering was also associated with a lower forced expiratory volume in one second (FEV(1)) (p < .0001). Severe complications were most common in subjects from Halabja who also made up the majority of participants. These results show that objective abnormalities are common in people with symptoms attributed to prior exposure to chemical agent. Blistering at the time of exposure was associated with more respiratory symptoms and worse lung function, but not with CT appearances. The high proportion of severe cases in comparison to reports from Iran may reflect the historical absence of effective early treatment, including strategies to reduce prolonged early exposure in this population.

The effect of sulfur mustard and nitrogen mustard on corneal collagen degradation induced by the enzyme collagenase.

OBJECTIVE: Sulfur mustard (SM) is an alkylating agent that can affect cornea and induce various complications. With regard to the role of the enzyme collagenase in dermatologic complications induced by sm and its role in other ocular disorders, we studied the effect of SM and nitrogen mustard (NM) on collagen degradation by collagenase. MATERIALS AND METHODS: This study included 7 groups of samples: The negative control group contained collagen without collagenase and toxins, the control group contained collagen and collagenase without any toxin, the positive control groups of NM and SM contained collagen and NM or SM without collagenase, the experimental groups of NM and SM contained collagen that was affected by NM or SM and collagenase, and the control group of collagenase contained only collagenase without containing collagen or receiving toxins. After incubation for 3.5 hours, the amount of hydroxyproline and the protein content of the samples were measured. Data were analyzed by analysis of variance (ANOVA). RESULTS: The protein concentrations of the negative control group and the positive control groups of SM and NM were significantly lower than those for all other groups of the study. There was a significant difference in hydroxyproline concentration of control group and negative control group; however, there was no significant difference between experimental group of SM and the positive control group of SM. There was no significant difference between the negative control group and the positive control group of SM in the hydroxyproline concentration of sediment samples. CONCLUSION: According to the results of this study, SM can affect the corneal collagen in a way in which collagenase cannot degrade it. In addition, it can be hypothesized that ineffective activity of this enzyme can result in increasing concentration of collagenase, which can lead to the destruction of the normal collagen of the cornea. The main result of this study confirms the hypothesis that SM inhibits the effect of collagenase on corneal collagen.

Visual and subjective outcomes following trifocal intraocular lens implantation in Iranian cataractous patients.

BACKGROUND: The aim of this study was to evaluate visual and refractive outcomes and quality of vision after implantation of the AT LISA tri 839MP intraocular lens (IOL). PATIENTS AND METHODS: This interventional clinical trial comprised 46 cataractous eyes of patients who underwent phacoemulsification with IOL implantation (mean age of 58.08 ± 11.01 years; range: 36-76 years old). Spherical equivalent (SE), uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), uncorrected intermediate visual acuity (UIVA), corrected intermediate visual acuity (CIVA), uncorrected near visual acuity (UNVA), and corrected near visual acuity (CNVA) were measured 1, 3, and 6 months after surgery. Contrast sensitivity (CS) was measured at 6 months. Subjective quality of vision and presence of dysphotopsia by a short questionnaire were evaluated postoperatively. RESULTS: At 6 months, the mean visual acuity was 0.08 ± 0.11, 0.03 ± 0.08, 0.07 ± 0.09, 0.02 ± 0.08, 0.05 ± 0.09, and 0.02 ± 0.08 LogMAR for UDVA, CDVA, UIVA, CIVA, UNVA, and CNVA, respectively. The mean values of SE were - 0.4728 ± 0.32D. These variables improved over time, yet significant changes were detected in UDVA (P = 0.009) and SE (P = 0.0001). The mean CS value was 1.74 ± 0.08. The mean scores (0% = no symptoms; 100% = strong symptoms/unable to perform activities) for glare and halos were 7.07 ± 0.22% and 8.70 ± 0.23%, respectively. These items were reduced over time. Patients' level of satisfaction mean score for performing activities was 96.66%. CONCLUSIONS: The AT LISA tri 839MP IOL provides excellent uncorrected distance, intermediate and near vision, and CS. This IOL showed a minimal level of photic phenomena and a high level of patient satisfaction.

Long-term ocular consequences of sulfur mustard in seriously eye-injured war veterans.

INTRODUCTION: Sulfur mustard (SM) has been used as a dangerous chemical warfare agent since the early 20th century. Although many descriptive studies about SM-induced ocular injuries are present in the medical literature, few of them have been conducted over a large group with serious ocular involvement. MATERIALS AND METHODS: This descriptive study was conducted on 149 severe SM-intoxicated war veterans. Ocular history, anterior and posterior segment findings using a slit lamp, and direct and indirect ophthalmoscopic findings were recorded. Severity of the disease was also recorded based on a chart of the Foundation of Martyrs and Veterans Affairs. RESULTS: Ocular complains included photophobia (73.2%), sense of decreased vision (72.5%), dry eye sensation (66.4%), foreign body sensation (61.1%), tearing (46.3%), and pain (43.0%). Slit lamp findings were meibomian gland dysfunction (MGD; 96%), blepharitis, punctal closure, trichiasis, tear break-up time, and tear meniscus layer abnormality (80% to 90%). Conjunctival disturbances included vascular abnormality, ischemia, hyperemia, subconjunctival fibrosis, and pterygium. Limbal changes were abnormal vessels, limbal tissue loss and pigment loss, and pannus formation. Corneal problems included epithelial and stromal disturbances, calcium deposition, and melting. The most frequent previous surgeries were punctal closure, lamellar keratoplasty (LK), and stem cell allograft. Severity of intoxication included mild (17%), moderate (25%), and severe (57%). CONCLUSION: Chronic blepharitis and decreased tear secretion are the 2 most important and influencing factors in progression of ocular problems in SM injuries. The more severe the initial exposure, percentage of disability, and duration of ocular involvement, the higher the likelihood of mustard gas keratopathy.

Estimating confined aquifer parameters using a simple derivative-based method.

The confined aquifer parameters, transmissivity and storage coefficient, are commonly determined using the pumping tests. Several methods have been developed to estimate confined aquifer parameters using pumping tests, but different methods suffer from different drawbacks. Those methods that use the truncated Theis well function w ( u ) , apply just early or late drawdowns, depending on the case, to estimate the aquifer parameters. Those methods, such as Theis (1935), that use non-truncated well function w ( u ) , can apply all drawdown data for aquifer parameter estimation but may still suffer from subjectivities such as personsal judgment in curve matching, time-consuming procedure and requiring values for Theis well function, w ( u ) , and its argument u ( u = r 2 S 4 T t ) . The aim of this study is to present a new method to overcome the aforementioned drawbacks and subjectivities involved in available published methods. In this paper, a simple derivative-based method is presented to estimate confined aquifer parameters applicable for entire drawdowns during the pumping period. The time derivative of drawdowns relate non-linearly with pumping time t , and therefore, aquifer parameters are estimated using developed equations based on the least squares optimization approach. The method is applied to three sets of synthetic, published and field data and results show that the estimation accuracy is acceptable. The drawdown time interval measurement has a marginal effect on parameters estimation due to the analytical basis of derivative calculations. The method does not require construction of graphs, and numerical calculations may be performed on a calculator to determine the aquifer parameters on site. It does not require curve matching, initial guess of the parameters and values of w ( u ) and u .

Pre-operative factors influencing post-operative outcomes from MyoRing implantation in keratoconus.

BACKGROUND: To identify pre-operative factors that influence post-operative performance of a full-ring intra-corneal implant (MyoRing) for the management of keratoconus. METHOD: In a retrospective study, medical records of 70 keratoconus eyes of 70 consecutive surgical patients with a mean age of 28.54 ± 6.52 years, who underwent MyoRing implantation using the PocketMaker microkeratome (Dioptex GmbH), were included and analysed before implantation and for visual outcome. Variables assessed included age, gender, keratoconus shape, uncorrected distance visual acuity, corrected distance visual acuity, spherical equivalent and keratometry reading. After the last follow-up, the eyes were graded for MyoRing implantation performance into worst, moderate and best subgroups. RESULTS: The mean values of uncorrected distance visual acuity, corrected distance visual acuity, spherical equivalent, manifest sphere and cylinder improved significantly post-operatively (p < 0.05). A statistically significant difference was found in the mean spherical equivalent (p = 0.046) and uncorrected distance visual acuity (p = 0.001) between moderate and best subgroups. No statistically significant correlation was found between age, sex, keratoconus shape, keratometric values, corrected distance visual acuity and visual outcome. CONCLUSIONS: According to this new grading system for MyoRing implantation performance, pre-operative uncorrected distance visual acuity and spherical equivalent are considered as the most important indicators for surgical performance in MyoRing treatment of keratoconus.

Evaluation of corneal biomechanical properties in mustard gas keratopathy.

BACKGROUND: Degenerative biomechanical factors and immunologic processes with effect on collagen and corneal reparative process are known as the main cause of ocular surface dysfunction in mustard gas keratopathy (MGK) and may cause changes in the corneal biomechanical values. Therefore, we evaluate corneal biomechanical properties of these patients. METHODS AND MATERIALS: This case-control study includes 61 chemical warfare victims with MGK. After omission according to our exclusion criteria, 88 eyes of patients with MGK were enrolled as the case group and also a group of 88 normal eyes, which were matched regarding their age and sex in the control group, were enrolled. Measurements of corneal biomechanical properties which reported by ORA and Corvis ST (CST) devices were compared. The SPSS software version 23.0 was used in the statistical analysis. For comparisons between groups, if the data had a normal distribution, were analyzed by Student's t-test and ANOVA, and if the data didn't have a normal distribution, Mann-Whitney U test, and Kruskal-Wallis were used. Furthermore, to identify a relationship between two groups of data Spearman's rank Correlation test was used. P value < 0.05 were considered statistically significant. RESULTS: In the MGK group, A1 length (A1L), A1 velocity (A1V), A2 velocity (A2V), deformation amplitude (DA) and peak distance (PD) were higher than the control group (P < 0.001). However, the corneal hysteresis (CH) (P = 0.003), corneal resistant factor (CRF), non-corrected IOP (IOPnct), corrected IOP based on corneal thickness (IOPpachy), and central corneal thickness (CCT) were lower than the control group (P < 0.001). The visual acuity according to the LogMAR scale and severity of MGK was positively associated with IOPpachy and negatively associated with CH, CRF, CCT and highest concavity radius (Radius). CONCLUSION: Measurement of corneal biomechanical properties may be, have a useful role in the classification, monitoring or diagnosis of MGK.