Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 37 records · Page 2Linked to original sources

PubMed2005

Application of probability circles analysis to the construction of calibration curves for infra red spectroscopy.

A new method, based on the presentation of initial data in the form of probability circles (PC), has been developed for constructing a calibration curve, which shows a monotonic dependence with respect to the given concentration. The centre of the reference probability circle is defined by its mean value and the radius of the circle is calculated as the value of the standard deviation of the sampling considered. The comparative probability circle is defined by the same corresponding parameters but rotated, relative to the initial reference circle, by an angle, which is related to the Pearson's correlation coefficient (PCC). The two parameters of the PCC and the statistical proximity factor (PCF), which defines the positions of the centres of the circles relative to each other, can be chosen as statistical parameters for the construction of the desired calibration curve. Experiments realized with the mixture of two liquids (chloroform serves as the basic matrix) and acetone (serves as an additive) confirm the efficiency of this new analytical method and demonstrate a possible increase sensitivity for the detection of lower concentration limit by approximately one order of magnitude. This new approach, which is free from model assumptions, and having very clear geometrical meaning, can be applied for different types of spectra and has many potential applications in the construction of calibration curves for different additives embedded within different matrices.

Calibration↗

PubMed2005

Nitrogen and phosphorus removal from plant nursery runoff in vegetated and unvegetated subsurface flow wetlands.

Subsurface horizontal flow reed beds are being evaluated for Nitrogen (N) and Phosphorus (P) removal from plant nursery runoff water in New South Wales Australia. The need to include plants (Phragmites australis), the effect of reaction time (3.5 v 7.0 d) and dissolved organic carbon (DOC) on N and P removal in batch fed gravel wetland tubs (55 L) was studied over 19 months. Simulated nursery runoff water containing N (10.1 mg L(-1), 74% as NO3) and P (0.58 mg L(-1), 88% as PO4) and DOC (2-5 mg L(-1)) was used. The planted wetland tubs removed >96% TN and TP over most of the 19-month study period while unplanted tubs were inefficient (<16% N and <45% P removal) and occasionally discharged nutrients. Doubling the reaction time to 7.0 days had no effect on nutrient removal. Plant nutrient uptake accounted for most of the N (76%) and P (86%) removed while roots and rhizomes were the dominant sink (N 58%, P 67%). The addition of methanol (C:N-3:1) to unplanted tubs achieved 81-98% N removal. In Carbon limited low nutrient nursery runoff, plants were essential to a gravel-based wetland to achieve efficient nutrient removal with effluent TN and TP concentrations of <1 mg L(-1) and 0.05 mg L(-1), respectively with a 3.5 day reaction time.

Agriculture↗

PubMed2005

Dietary exposure to chemical migrants from food contact materials: a probabilistic approach.

A two-dimensional probabilistic model has been developed to estimate the short-term dietary exposure of UK consumers to migrants from food packaging materials. The current EU approach uses a default scenario of assuming that all individuals are 60 kg weight and consume 1 kg of food packaged in the material of interest per day. Using four UK National Dietary and Nutrition Surveys comprising 4-7 day dietary records for different age groups and survey years, a sample representative of the UK population has been obtained consuming around 4200 different food items. Each survey provides records for around 2000 individuals and supplies detailed information on the consumption of food and data on sex, height and socio-economic status which may be used to analyse the exposure of selected groups within the community. As a result we are able to address the variation in consumption of food amongst individuals, and account for actual body weights providing a more accurate representation of the 'true' exposure. The migrants bisphenol A diglycidyl ether (BADGE), di-2-ethylhexyl adipate (DEHA) and styrene were considered as specimen compounds although the methodology employed has the flexibility to adapt to other migrants and packaging types and indeed other food contaminants. Exposure for each individual is estimated by calculating and summing the individual exposure from each item in their diet, and is repeated for all individuals in each survey to produce a distribution of exposures for the population. The packaging type of each food item is assigned by utilizing known packaging types from the database or, by sampling from a distribution based upon market share information. The parameters contributing towards the exposure from a packaged dietary item are migrant concentration and item weight. Distributions are used to represent the inherent variation and uncertainty affecting these parameters. Where data on concentrations for a particular type of food are lacking, expert judgement is used to extrapolate from available data for other food types. The model can also be run using only migration data for food simulants. In this case, concentrations expected for each of the food items are assigned based on the data for the relevant food simulant. The primary outputs of the model are distributions of estimated daily intakes for the selected population. Each distribution gives the variation across the population subject to the uncertain parameters sampled in that iteration of the model. Analysing the ensemble of distributions allows us to obtain the confidence limits around estimates for percentiles due to the uncertainties. The probabilistic approach allows sensitivity analysis to evaluate the relative importance of the input parameters and places confidence bounds on the outputs to show the effect of the uncertainties and the contribution of each food type toward the overall exposure.

Adipates↗

PubMed2005

Selective operative cholangiography in the performance of laparoscopic cholecystectomy.

The objective of this prospective study was to evaluate the role of intraoperative cholangiography (IOC) for patients undergoing laparoscopic cholecystectomy (LC) to determine whether it could be safely omitted for all patients who fit standard criteria, namely normal liver function tests, no history of gallstone pancreatitis, common bile duct (CBD) diameter less than 10 mm or previous history of jaundice. Data were collected prospectively from 194 consecutive patients who had LC for symptomatic gall bladder disease. IOC was not performed in any patient. The conversion rate was 6.1% and one CBD injury occurred. Our experience demonstrates that LC performed without routine IOC does not result in an increased incidence of retained stones in selected patients who have no history of pancreatitis, normal liver function tests and CBD less than 10 mm diameter.

Adolescent↗

PubMed2005

Factors associated with infection by Pseudomonas aeruginosa in adult cystic fibrosis.

Cross-infection with Pseudomonas aeruginosa is an emerging issue in the care of patients with cystic fibrosis (CF). This study sought to determine the extent of, and patient factors associated with, cross-infection in a tertiary referral adult CF centre. P. aeruginosa isolates were genotyped into two groups between November 2001 and February 2003, using pulsed-field gel electrophoresis after DNA digestion by the SpeI endonuclease, and identified as clustered if there was >80% homology in the macrorestriction profiles. Patient factors and measures of disease severity were identified a priori. In total, 157 out of 227 patients had a P. aeruginosa isolate genotyped. Of these, 94 patients (60%) were infected with clustered genotypes and 47 (30%) were infected with the newly described "Midlands 1" (Md1) genotype. A further 18 patients were infected with the previously identified "Liverpool" genotype and two with the "Manchester" genotype. Logistic regression analysis revealed that the predominant predictor of infection with Md1 was age at the time of referral to the centre, suggesting that infection may have occurred prior to referral in some patients. Md1 demonstrated a relatively benign anti-biogram and did not appear to be associated with more severe disease. In conclusion, the present study provides further evidence of the emerging importance of Pseudomonas aeruginosa cross-infection in cystic fibrosis.

Adult↗

PubMed2005

Early results of autologous chondrocyte implantation in the talus.

Autologous chondrocyte implantation (ACI) has been used most commonly as a treatment for cartilage defects in the knee and there are few studies of its use in other joints. We describe ten patients with an osteochondral lesion of the talus who underwent ACI using cartilage taken from the knee and were prospectively reviewed with a mean follow-up of 23 months. In nine patients the satisfaction score was 'pleased' or 'extremely pleased', which was sustained at four years. The mean Mazur ankle score increased by 23 points at a mean follow-up of 23 months. The Lysholm knee score returned to the pre-operative level at one year in three patients, with the remaining seven showing a reduction of 15% at 12 months, suggesting donor-site morbidity. Nine patients underwent arthroscopic examination at one year and all were shown to have filled defects and stable cartilage. Biopsies taken from graft sites showed mostly fibrocartilage with some hyaline cartilage. The short-term results of ACI for osteochondral lesions of the talus are good despite some morbidity at the donor site.

Adolescent↗

PubMed2004

Rosuvastatin upregulates the antioxidant defense protein heme oxygenase-1.

Cholesterol-independent, pleiotropic actions of HMG-CoA reductase inhibitors (statins) lead to anti-inflammatory and antioxidant actions by as yet unidentified mechanisms. This study explores the role of heme oxygenase-1 (HO-1) as target and potential mediator of rosuvastatin. In cultured human endothelial cells (ECV 304), rosuvastatin increased HO-1 mRNA and protein levels in a concentration-dependent fashion. HO-1 induction by rosuvastatin remained unaffected by mevalonate and N-nitro-L-arginine-methylester, showing that isoprenoid- and NO-dependent pathways were not involved. Pretreatment of endothelial cells with rosuvastatin reduced NADPH-dependent production of oxygen radicals. The HO-1 metabolite bilirubin, when added exogenously to the cells, virtually abolished NADPH-dependent oxidative stress. Rosuvastatin-induced inhibition of free radical formation was rescued in the presence of the HO inhibitor, tin protoporphyrin-IX. Our results demonstrate that HO-1 is a target site and antioxidant mediator of rosuvastatin in endothelial cells. This novel pathway may contribute to and partially explain the pleiotropic antiatherogenic actions of rosuvastatin.

Antioxidants↗

PubMed2004

First results from the Cryogenic Dark Matter Search in the Soudan Underground Laboratory.

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg d of Ge net exposure after cuts for recoil energies between 10 and 100 keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. Using the standard dark-matter halo and nuclear-physics WIMP model, these data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross section for all WIMP masses above 15 GeV/c2, ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4 x 10(-43) cm2 at a WIMP mass of 60 GeV/c2.

Journal Article↗

PubMed2004

National symptom surveillance using calls to a telephone health advice service--United Kingdom, December 2001-February 2003.

INTRODUCTION: Recent terrorist activity has highlighted the need to improve surveillance systems for the early detection of chemical or biologic attacks. A new national surveillance system in the United Kingdom (UK) examines symptoms reported to NHS Direct, a telephone health advice service. OBJECTIVES: The aim of the surveillance system is to identify an increase in symptoms indicative of early stages of illness caused either by a deliberate release of a biologic or chemical agent or by common infections. METHODS: Data relating to 10 key syndromes (primarily respiratory and gastrointestinal) are received electronically from 23 call centers covering England and Wales. Data are analyzed daily and statistically significant excesses, termed exceedances, in calls are automatically highlighted and assessed by a multidisciplinary team. RESULTS: During December 2001-February 2003, a total of 1,811 exceedances occurred, of which 126 required further investigation and 16 resulted in alerts to local or national health-protection teams. Examples of these investigations are described. CONCLUSION: Surveillance of call-center data has detected substantial levels of specific syndromes at both national and regional levels. Although no deliberate release of a biologic or chemical agent has been detected thus far by this or any other surveillance system in the UK, the NHS Direct surveillance system continues to be refined.

Bioterrorism↗

PubMed2004

Early analgesic effects of parecoxib versus ketorolac following laparoscopic sterilization: a randomized controlled trial.

BACKGROUND: The aim of this prospective double blind randomized controlled trial was to compare the effects of ketorolac and parecoxib on early postoperative pain. METHOD: We studied 36 ASA I/II patients who received a standardized general anaesthetic for laparoscopic sterilization. Patients were allocated randomly to receive either parecoxib 40 mg i.v. or ketorolac 30 mg i.v., at induction. After surgery, patients were assessed on awakening and then at 1, 2, and 3 h. Abdominal pain at rest and on inspiration, in addition to nausea and sedation were assessed on a 100 mm visual analogue scale. RESULTS: Of 36 patients, one was excluded from analysis. In the remaining patients, pain scores at rest and on inspiration were significantly lower in patients given ketorolac compared with those given parecoxib. This difference was attributable to the higher pain scores on awakening and at 1 h postoperatively in the parecoxib group compared with the ketorolac group. Despite this initial difference, there was no significant difference between the two groups in the number of patients receiving rescue analgesia. The median (interquartile range) time to consumption of rescue cocodamol of 60 (46-74) min in the parecoxib group was not significantly shorter than that of 100 (70-130) min in the ketorolac group. The amount of cyclizine given, nausea and sedation did not differ significantly between the groups. CONCLUSION: We found that parecoxib 40 mg i.v. given at induction of anaesthesia was less effective than or ketorolac 30 mg i.v., in the first hour after laparoscopic sterilization.

Adult↗

PubMed2004

Measurement of the electric form factor of the neutron at Q2=0.5 and 1.0 GeV2/c2.

The electric form factor of the neutron was determined from measurements of the d-->(e-->,e'n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (15ND3) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G(n)(E)=0.0526+/-0.0033(stat)+/-0.0026(sys) and 0.0454+/-0.0054+/-0.0037 at Q(2)=0.5 and 1.0 (GeV/c)(2), respectively.

Journal Article↗

PubMed2004

Ultrasound diagnosis of severe thrombotic placental damage in the second trimester: an observational study.

OBJECTIVES: To screen women with uteroplacental insufficiency between 18 and 26 weeks' gestation for sonographic evidence of destructive placental lesions, to observe the effect of low molecular-weight heparin (LMWH) in these cases, and to compare the outcome with similar but untreated controls. METHODS: We screened 180 women at high risk for placental damage using 16-week maternal serum screening (alpha-fetoprotein and human chorionic gonadotropin), placental shape and texture, and uterine artery Doppler waveforms at the 18-20-week level II examination. Serial gray-scale examinations of placental texture were performed at 22, 24 and 26 weeks. LMWH was offered to women with ultrasound evidence of destructive placental lesions in the absence of intrauterine growth restriction and/or pre-eclampsia. RESULTS: We prospectively identified six women (3.3%) with abnormal maternal serum screening and uterine artery Doppler in whom abnormal placental texture (echogenic cystic lesions) suggestive of destructive lesions in the placental parenchyma was found either at the 18-20-week ultrasound examination (n = 4), or by 26 weeks of gestation (n = 2). All six received LMWH and had live births (gestational age at delivery, 33-37 weeks; birth weight, 1000-3200 g). A further 14 women were referred with similar multiparameter evidence of placental damage at or after 26 weeks, outside the screening study. All had significant fetal growth restriction and were therefore not offered heparin. In 9/14 cases there was a perinatal death. Ischemic and/or thrombotic placental pathology was confirmed in each case, but no maternal thrombophilia disorders were identified in the 20 women. CONCLUSIONS: Integrated biochemical and ultrasound testing of placental function at 16-20 weeks of gestation, followed by serial placental gray-scale ultrasound, may be an effective method of identifying a subset of pregnancies at high risk of adverse pregnancy outcome due to destructive lesions in the placental parenchyma. This strategy of identifying thrombo-occlusive placental lesions before the development of pregnancy complications may prove useful in the design of trials to study the effectiveness of LMWH in the prevention of clinical complications resulting from thrombo-occlusive placental disease.

Anticoagulants↗

PubMed2004

Implementation of ALARA radiation protection on the ISS through polyethylene shielding augmentation of the Service Module Crew Quarters.

With 5-7 month long duration missions at 51.6 degrees inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the "as low as reasonably achievable" (ALARA) precept requires that radiological risks be minimized when possible through a dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (CnHn) is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in equivalent dose to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry.

Astronauts↗

PubMed2004

Is continuous spinal analgesia via an epidural catheter appropriate after accidental subarachnoid administration of 15 mL of bupivacaine 0.1% containing fentanyl 2 micrograms/mL?

We report a case of accidental insertion of an epidural catheter into the subarachnoid space and accidental administration of 15 mL of bupivacaine 0.1% with fentanyl 2 micrograms/mL, in the sitting position, during labour. Within 5 min, the patient was unable to move her lower limbs. Although the upper level of the sensory block using ethyl chloride was found to be T5, there was no cardiovascular depression. The catheter was left in situ and used for continuous spinal analgesia. Further administration of the bupivacaine-fentanyl solution was not required until after 315 min. The patient was given five further 2- to 3-mL top-up doses of bupivacaine-fentanyl at intervals of 105 to 145 min. After 16 h, caesarean section was performed for failure to progress in the first stage of labour. This was conducted under spinal anaesthesia using 2 mL of hyperbaric bupivacaine 0.5% with fentanyl 20 micrograms. A healthy baby was delivered with Apgar scores of 10 and 10, at 1 and 5 min, respectively. There was no postdural puncture headache or any neurological complications.

Adult↗

PubMed2004

Is intraperitoneal levobupivacaine with epinephrine useful for analgesia following laparoscopic cholecystectomy? A randomized controlled trial.

BACKGROUND AND OBJECTIVE: A randomized controlled trial of patients undergoing laparoscopic cholecystectomy. To evaluate whether the instillation of levobupivacaine, with epinephrine, intraperitoneally, reduces morphine consumption; further, to consider the degree of abdominal and shoulder pain in the presence of local anaesthetic at the site of surgical incision. METHODS: Patients received a standardized procedure and were allocated randomly to receive either (a) 2.5 mg mL(-1) levobupivacaine 30 mL, with epinephrine 5 microg mL(-1), or (b) normal saline 30 mL, with epinephrine 5 microg mL(-1), to the bed of the gall bladder and above the liver, immediately before wound closure. RESULTS: Median (interquartile range) total abdominal pain during inspiration in the levobupivacaine group was significantly (P = 0.041) lower (71 (21-129) mm) than that in the placebo group (123 (71-179) mm). However, there was no significant difference between the two groups with respect to total abdominal pain at rest, right shoulder pain or the consumption of rescue morphine and rescue dihydrocodeine. There were no differences between the two groups with respect to the administration of cyclizine, total nausea and total sedation scores. In addition, the number of episodes of vomiting was not significantly different. CONCLUSIONS: Intraperitoneal administration of levobupivacaine with epinephrine is associated with modest analgesia following laparoscopic cholecystectomy.

Adult↗

PubMed2004

Albuminuria predicts cardiovascular events independently of left ventricular mass in hypertension: a LIFE substudy.

We wanted to investigate whether urine albumin/creatinine ratio (UACR) and left ventricular (LV) mass, both being associated with diabetes and increased blood pressure, predicted cardiovascular events in patients with hypertension independently. After 2 weeks of placebo treatment, clinical, laboratory and echocardiographic variables were assessed in 960 hypertensive patients from the LIFE Echo substudy with electrocardiographic LV hypertrophy. Morning urine albumin and creatinine were measured to calculate UACR. The patients were followed for 60+/-4 months and the composite end point (CEP) of cardiovascular (CV) death, nonfatal stroke or nonfatal myocardial infarction was recorded. The incidence of CEP increased with increasing LV mass (below the lower quartile of 194 g to above the upper quartile of 263 g) in patients with UACR below (6.7, 5.0, 9.1%) and above the median value of 1.406 mg/mmol (9.7, 17.0, 19.0%(***)). Also the incidence of CV death increased with LV mass in patients with UACR below (0, 1.4, 1.3%) and above 1.406 mg/mmol (2.2, 6.4, 8.0%(**)). The incidence of CEP was predicted by logUACR (hazard ratio (HR)=1.44(**) for every 10-fold increase in UACR) after adjustment for Framingham risk score (HR=1.05(***)), history of peripheral vascular disease (HR=2.3(*)) and cerebrovascular disease (HR=2.1(*)). LV mass did not enter the model. LogUACR predicted CV death (HR=2.4(**)) independently of LV mass (HR=1.01(*) per gram) after adjustment for Framingham risk score (HR=1.05(*)), history of diabetes mellitus (HR=2.4(*)) and cerebrovascular disease (HR=3.2(*)). (*)P<0.05, (**)P<0.01, (***)P<0.001. In conclusion, UACR predicted CEP and CV death independently of LV mass. CV death was predicted by UACR and LV mass in an additive manner after adjustment for Framingham risk score and history of CV disease.

Aged↗

PubMed2004

Impact of age on left ventricular hypertrophy regression during antihypertensive treatment with losartan or atenolol (the LIFE study).

To assess the influence of age on changes in left ventricular (LV) mass and geometry during antihypertensive treatment, we related age to clinical and echocardiographic findings before and after 4 years of antihypertensive treatment in a subset of 560 hypertensive patients without known concurrent disease in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study, which randomized patients to blinded losartan- or atenolol-based treatment. Patients >/=65 years (older group) included more women and patients with isolated systolic hypertension or albuminuria (all P<0.05). Compared to patients <65 years, older patients had higher pulse pressure, LV mass, and prevalence of concentric hypertrophy at baseline (78 vs 69 mmHg, 234 vs 224 g, and 28 vs 16%, respectively, all P<0.01), while the mean blood pressure did not differ. Over 4 years, reductions in LV mass and the mean blood pressure were similar in both groups, but older patients more often had residual hypertrophy (31 vs 15%, P<0.001) with a preponderance of eccentric geometry. In multivariate analysis of 4-year change in LV mass controlling for baseline mass, larger hypertrophy reduction was associated with losartan treatment, while age, gender, body mass index, and 4-year change in pulse pressure and albuminuria did not enter (Multiple R (2)=0.40, P<0.001). Thus, in up-to-80-year-old hypertensive patients with left ventricular hypertrophy, age did not significantly attenuate hypertrophy reduction during antihypertensive treatment, although residual hypertrophy was more prevalent in older patients as a consequence of higher initial LV mass.

Age Factors↗

PubMed2004

A pilot study of a system for grading of drainage blebs after glaucoma surgery.

PURPOSE: To develop and evaluate a novel bleb grading scheme for clinical and photographic evaluation. METHOD: A system for grading bleb photographs using widely applicable parameters was designed, and reference color photographs printed. A prospective masked agreement study was undertaken comparing slit lamp examination with mono and stereo photographs; 36 eyes of 28 patients with previous glaucoma surgery were graded according to defined parameters on a 1 to 10 scale clinically at the slit lamp by four ophthalmologists and two optometrists. Standardized stereo and mono photographs of the blebs were taken on the same day. The photographs were graded at least one week later in a masked fashion by the same observers, with grading of mono and stereo photographs also separated by one week. Analysis was performed to determine the variability and agreement between slit lamp results and photographic results, and to identify the presence of systematic bias. RESULTS: High levels of agreement were found between slit lamp and both stereo and mono photographs for vascularity indices, bleb wall thickness, and bleb elevation. Lower levels of agreement were found for the relative components of demarcated versus diffuse areas of the bleb, and for the total width of the bleb. The interquartile range for the median difference between slit lamp and photograph grading was -1.0 to 1.0 for all criteria except diffuse component (-2.0 to 2.0), and the median difference for all scores was 0.0. The median interobserver difference for all criteria was 0.0; the quartile range for all scores was between -0.5 and 1.0 except for diffuse component and width assessments whose quartiles fell in the -1.75 to 1.0 range. Examiners agreed with photographic grading within +/- 1 in more than 80% of gradings for vascularity and bleb height, within +/- 1 in more than 75% of gradings for bleb wall thickness, within +/- 2 in 61% of bleb width assessments, and +/- 2 in 59% of diffuse component. CONCLUSION: This bleb grading system is reproducible clinically and photographically. High levels of agreement between scores for photographs versus slit lamp examination were found for most categories, with good interobserver agreement for both photograph and slit lamp grading. Further refinement of scoring and reference photographs is required for optimization, especially for grading of bleb morphology.

Drainage↗