Diazepam induced sleep spindle increase correlates with cognitive recovery in a child with epileptic encephalopathy.

BACKGROUND: Continuous spike and wave of sleep with encephalopathy (CSWS) is a rare and severe developmental electroclinical epileptic encephalopathy characterized by seizures, abundant sleep activated interictal epileptiform discharges, and cognitive regression or deceleration of expected cognitive growth. The cause of the cognitive symptoms is unknown, and efforts to link epileptiform activity to cognitive function have been unrevealing. Converging lines of evidence implicate thalamocortical circuits in these disorders. Sleep spindles are generated and propagated by the same thalamocortical circuits that can generate spikes and, in healthy sleep, support memory consolidation. As such, sleep spindle deficits may provide a physiologically relevant mechanistic biomarker for cognitive dysfunction in epileptic encephalopathies. CASE PRESENTATION: We describe the longitudinal course of a child with CSWS with initial cognitive regression followed by dramatic cognitive improvement after treatment. Using validated automated detection algorithms, we analyzed electroencephalograms for epileptiform discharges and sleep spindles alongside contemporaneous neuropsychological evaluations over the course of the patient's disease. We found that sleep spindles increased dramatically with high-dose diazepam treatment, corresponding with marked improvements in cognitive performance. We also found that the sleep spindle rate was anticorrelated to spike rate, consistent with a competitively shared underlying thalamocortical circuitry. CONCLUSIONS: Epileptic encephalopathies are challenging electroclinical syndromes characterized by combined seizures and a deceleration or regression in cognitive skills over childhood. This report identifies thalamocortical circuit dysfunction in a case of epileptic encephalopathy and motivates future investigations of sleep spindles as a biomarker of cognitive function and a potential therapeutic target in this challenging disease.

Psychotropic medications use and side effects of individuals with intellectual and developmental disabilities.

BACKGROUND: Many people with intellectual and developmental disabilities (IDD) are treated with psychotropic medications, and polypharmacy is common. Although few studies address psychotropic side effects in the population, people with IDD have been found more likely to experience side effects than others who do not have IDD. Because many individuals with IDD may not report side effects reliably, there is risk that side effects may be missed. METHODS: Psychotropic use and side effects of 71 adults with IDD admitted for a 30-day crisis stay to a Systemic, Therapeutic, Assessment, Resources, and Treatment (START) Resource Center were reviewed. START is a specialised behavioural health outreach, training and crisis programme for individuals with IDD. During crisis stays, centre nurses administer the Matson Evaluation of Drug Side Effects screen, a psychometrically established psychotropic medication side effects screen developed for use with people with IDD. Data reviewed were de-identified data used to inform day-to-day practices and assess outcomes for individuals START served. RESULTS: The average age was 28 years, and 56% of the sample was male. All individuals were taking at least one psychotropic, while 79% were taking three or more. The average number of psychotropics used was 3.94. Antipsychotics were the most commonly prescribed medications taken by 85% of the sample; 49% of whom were not reported to have psychosis. Although the overall number of psychotropics did not correlate with Matson Evaluation of Drug Side Effects scores, the average scale scores for all participants was high in contrast to prior studies of people with IDD not taking psychotropics, with central nervous system side effects being the most commonly reported. CONCLUSION: In the present study, data for individuals experiencing a crisis were reviewed and indicated high rates of psychotropic polypharmacy and side effects rates higher than previously reported for people with IDD not taking psychotropics. Prospective study in larger samples is needed to determine if missed or under-appreciated psychotropic side effects may play a role in behavioural health challenges of some people with IDD.

Management of thyroid eye disease in the United Kingdom: A multi-centre thyroid eye disease audit.

This article aims to provide baseline data and highlight any major deficiencies in the current level of care provided for adult patients with thyroid eye disease (TED). We undertook a prospective, nonrandomized cross-sectional multicenter observational study. During a 3-month period June-August 2014, consecutive adult patients with TED who presented to nominated specialist eye clinics in the United Kingdom, completed a standardized questionnaire. Main outcome measures were: demographics, time from diagnosis to referral to tertiary centre, time from referral to review in specialist eye clinic, management of thyroid dysfunction, radioiodine and provision of steroid prophylaxis, smoking, and TED classification. 91 patients (mean age 47.88 years) were included. Female-to-male ratio was 6:1. Mean time since first symptoms of TED = 27.92 (73.71) months; from first visit to any doctor with symptoms to diagnosis = 9.37 (26.03) months; from hyperthyroidism diagnosis to euthyroidism 12.45 (16.81) months. First, 13% had received radioiodine. All those with active TED received prophylactic steroids. Seven patients who received radioiodine and did not have TED at the time went on to develop it. Then, 60% patients were current or ex-smokers. 63% current smokers had been offered smoking cessation advice. 65% patients had active TED; 4% had sight-threatening TED. A large proportion of patients (54%) were unaware of their thyroid status. Not enough patients are being provided with smoking cessation advice and information on the impact of smoking on TED and control of thyroid function.

A biodegradable antibiotic-impregnated scaffold to prevent osteomyelitis in a contaminated in vivo bone defect model.

Open fractures are at risk of serious infection and, if infected, require several surgical interventions and courses of systemic antibiotics. We investigated a new injectable formulation that simultaneously hardens in vivo to form a porous scaffold for bone repair and delivers antibiotics at high concentrations to the local site of infection. Duration of antimicrobial activity against Staphylococcus aureus was determined using the serial plate transfer test. Ultimate compressive strength and porosity of the material was measured with and without antibiotics. The material was evaluated in vivo in an ovine medial femoral condyle defect model contaminated with S. aureus. Sheep were sacrificed at either 2 or 13 weeks and the defect and surrounding bone assessed using micro-computed tomography and histology. Antimicrobial activity in vitro persisted for 19-21 days. Sheep with antibiotic-free material and bacteria became infected, while those with antibiotic-containing material and bacteria did not. Similarly, new bone growth was seen in uninoculated animals with plain polymer, and in those with antibiotic polymer with bacteria, but not in sheep with plain polymer and bacteria. The antibiotic-impregnated scaffolds were effective in preventing S. aureus infections whilst supporting bone growth and repair. If translated into clinical practice, this approach might reduce the need for systemic antibiotics.

Is Clostridium difficile associated with the '4C' antibiotics? A retrospective observational study in diabetic foot ulcer patients.

AIMS: Clostridium difficile is an anaerobic cytotoxin-producing bacterium that can cause infectious diarrhoea, pseudomembranous colitis and toxic megacolon. The major risk factors for developing C. difficile infection include recent or current antimicrobial use, diabetes, age over 65, proton pump inhibitor use, immunosuppression and previous infection with C. difficile. Most diabetic foot ulcers are polymicrobial. METHODS: As a result guidelines advise treatment with broad spectrum antibiotics which include the '4C's' (clindamycin, cephalosporins, co-amoxiclav and ciprofloxacin) which are associated with a higher risk of C. difficile infection. Retrospective observational data (June 2008 to January 2012) for the diabetes foot ulcers were gathered from the Diabetes/Podiatry Clinic database in NHS Ayrshire and Arran and cross-matched with the NHS Ayrshire and Arran Microbiology database. There were 111 patients with mean age 59 years (range 24-94 years), 33 type 1 patients, 78 type 2 patients, mean duration of diabetes 16 years (6 months-37 years) and mean HbA1c 67 mmol/mol (54-108 mmol/mol) [8.3% (7.1-12%)]. RESULTS: The total number of days antimicrobials prescribed for all patients was 7938 (mean number of antimicrobial days per patient = 71.5 days). There was one case of C. difficile infection of 111 patients giving an incidence of 1.25 cases per 10,000 patient-days of antibiotics/1 case per 209 foot ulcers. CONCLUSIONS: Large doses, numbers and greater duration of antibiotic therapy all result in a greater degree of normal gut flora depletion. It is possible that the alterations in gut flora in diabetic foot ulcer patients protect them from antibiotic-induced C. difficile overgrowth.

Mucositis, conjunctivitis but no rash - the "Atypical Stevens - Johnson syndrome".

The Stevens-Johnson syndrome (SJS) classically involves a rash, conjunctivitis and mucositis. We describe the case of a young adult male with isolated mucositis and conjunctivitis . Previous rare reports of severe SJS like syndromes without a rash are confined to children, usually with mycoplasma pnemoniae infection.(1) Terminology for this syndrome includes - "Stevens-Johnson Syndrome without skin lesions", or "Atypical Stevens - Johnson Syndrome".(2) This case highlights the importance of maintaining an open mind when a "full house" of clinical features is absent. It also illustrates the use of a rapid electronic literature review as a clinical tool. The importance of updating records when a drug has been cleared of causing harm is highlighted.

The pursuit of the magic pill: the overuse of psychotropic medications in children with intellectual and developmental disabilities in the USA.

Children with intellectual and developmental disabilities (IDD) are likely to receive high-risk prescribing practices, such as polypharmacy, long-term use of psychotropic medications, and overuse of antipsychotics. Behavioural interventions, such as applied behavioural analysis, are evidence-based practices for children with IDD and should be the first-line treatment. Short-term use of psychotropic medications may be helpful in reducing the severity and frequency of challenging behaviours while evidence-based behavioural interventions are pursued. In this essay, we offer practical guidelines for better care.

Regulation of cyclin D2 and the cyclin D2 promoter by protein kinase A and CREB in lymphocytes.

Lymphocyte proliferation is key to the regulation of the immune system. Cyclin D2 is the first cell cycle protein induced following stimulation through the T-cell receptor, the B-cell receptor or cytokines. The promoter of this cyclin integrates a diverse range of signals. Through investigating the regulation of this promoter by interleukin-2 and phosphatidylinositol 3-kinase, we have identified a role for the transcription factor CREB, cAMP response element-binding protein. Mutation of the CREB-binding site reduced cyclin D2 promoter activity 5-10-fold. CREB-1 is phosphorylated at serine 133, a critical site for activity, in both T cells and Epstein-Barr virus immortalized B cells. The introduction of an S133A mutant of CREB-1 reduces IL-2 induction of cyclin D2 promoter activity, demonstrating a role for this phosphorylation site in promoter activity. Two inhibitors of protein kinase A reduce lymphocyte proliferation and CREB-1 phosphorylation. This study demonstrates that the cyclin D2 promoter is capable of being regulated by PI3K and CREB and identifies CREB-1 and protein kinase A as potential targets for altering lymphocyte proliferation.

Vascular endothelial growth factor is produced by peritoneal fluid macrophages in endometriosis and is regulated by ovarian steroids.

Angiogenesis is important in the pathophysiology of endometriosis, a condition characterized by implantation of ectopic endometrium in the peritoneal cavity. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor involved in physiological and pathological angiogenesis, and elevated levels of VEGF are found in peritoneal fluid of patients with endometriosis. Our aim was to investigate the site of expression and regulation of VEGF in endometriosis. VEGF immunoreactivity was found in tissue macrophages present in ectopic endometrium and in activated peritoneal fluid macrophages. Macrophage activation was highest in women with endometriosis, and media conditioned by peritoneal fluid macrophages from these women caused a VEGF-dependent increase in endothelial cell proliferation above that seen from normal women. Peritoneal fluid macrophages secreted VEGF in response to ovarian steroids, and this secretion was enhanced after activation with lipopolysaccharide. Peritoneal fluid macrophages expressed receptors for steroid hormones. VEGF receptors flt and KDR (kinase domain receptor) were also detected, suggesting autocrine regulation. During the menstrual cycle, expression of flt was constant but that of KDR was increased in the luteal phase, at which time the cells migrated in response to VEGF. KDR expression and the migratory response were significantly higher in patients with endometriosis. This study demonstrates that activated macrophages are a major source of VEGF in endometriosis and that this expression is regulated directly by ovarian steroids.

Expression of vascular endothelial growth factor and its receptors flt and KDR in ovarian carcinoma.

BACKGROUND: Two thirds of patients with ovarian carcinoma have advanced disease at diagnosis and have poor prognoses because of the presence of highly invasive carcinoma cells and rapidly accumulating ascitic fluid. Vascular endothelial growth factor (VEGF), a potent mitogen of endothelial cells, is produced in elevated amounts by many tumors, including ovarian carcinomas. The known human receptors for VEGF, flt and KDR, are both cell surface tyrosine kinases and are expressed predominantly on endothelial cells. Acting through these receptors, VEGF may stimulate angiogenesis and promote tumor progression. PURPOSE: We aimed to clarify the function of VEGF in tumor development by identifying the cells in ovarian carcinoma tissue that express VEGF and its receptors. METHODS: VEGF, flt, and KDR expression was localized by in situ hybridization and immunohistochemistry in frozen sections of primary tumors from five patients with ovarian carcinoma and from metastases of ovarian carcinoma from three different patients. Reverse transcription followed by polymerase chain reaction (RT-PCR) and an enzyme-linked immunosorbent assay were used to analyze VEGF, flt, and KDR expression in six epithelial cell lines derived from ovarian carcinoma ascites from five additional patients. RESULTS: Messenger RNAs (mRNAs) encoding VEGF, flt, and KDR were detected in primary ascitic cells and in three of four ovarian carcinoma cell lines examined by RT-PCR. Two novel complementary DNAs that may encode truncated, soluble forms of flt were cloned from one primary source. VEGF levels of 20-120 pM were found in culture media conditioned by the cell lines. Elevated expression of VEGF mRNA was found in all primary tumors and metastases, especially at the margins of tumor acini. VEGF immunoreactivity was concentrated in clusters of tumor cells and patches of stromal matrix. flt immunoreactivity was confined to tumor blood vessels, but flt mRNA was not detected by in situ hybridization. In contrast, KDR mRNA was detected not only in vascular endothelial cells but also in tumor cells at primary malignant sites. CONCLUSIONS: VEGF is expressed by tumor cells in primary and metastatic ovarian carcinoma and accumulates in the stromal matrix. Its receptors, flt and KDR, are expressed by some tumor cells that coexpress VEGF. This is the first localization of KDR expression in nonendothelial cells. IMPLICATIONS: Coexpression of VEGF and KDR by tumor cells in ovarian carcinoma raises the possibility of autocrine stimulation and of therapeutic strategies targeting this receptor-ligand interaction.

Incorporation of hypoxanthine into adenine and guanine nucleotides by human platelets.

1. Incubation (1-4 h) of normal human washed platelets (5-11-10-8 per ml) with [8-14C] hypoxanthine at a concentration of 10-5 M resulted in a linear incorporation of radioactivity into adenine and guanine nucleotides. 2. Washed platelets from patients with Lesch-Nyhan syndrome, deficient in hypoxanthine: guanine phosphoribosyltransferase, failed to demonstrate any significant incorporation of [8-14C] hypoxanthine but did incorporate [8-14C] adenine like normal platelets under the same incubation condition. 3. These findings are taken to indicate that normal platelets have the enzymes necessary for salvage of hypoxanthine and that hypoxanthine: guanine phosphoribosyltransferase is the obligatory first step in this pathway.

The impact of communicating information about air pollution events on public health.

Short-term exposure to air pollution has been associated with exacerbation of asthma and chronic obstructive pulmonary disease (COPD). This study investigated the relationship between emergency hospital admissions for asthma, COPD and episodes of poor air quality in an English city (Southampton) from 2008-2013. The city's council provides a forecasting service for poor air quality to individuals with respiratory disease to reduce preventable admissions to hospital and this has been evaluated. Trends in nitrogen dioxide, ozone and particulate matter concentrations were related to hospital admissions data using regression analysis. The impacts of air quality on emergency admissions were quantified using the relative risks associated with each pollutant. Seasonal and weekly trends were apparent for both air pollution and hospital admissions, although there was a weak relationship between the two. The air quality forecasting service proved ineffective at reducing hospital admissions. Improvements to the health forecasting service are necessary to protect the health of susceptible individuals, as there is likely to be an increasing need for such services in the future.

Effect of long-term cold exposure on antioxidant enzyme activities in a small mammal.

Aerobic organisms continually face exposure to reactive oxygen species (ROS) and many have evolved sophisticated antioxidant systems to effectively remove them. Any increase in ROS production or weakening in this defense system may ultimately lead to oxidative stress and cellular damage. We investigated whether long-term cold exposure, which is known to lead to an elevation in metabolic rate, increased the activities of the ROS-scavenging enzymes, catalase (CAT), selenium-dependent glutathione peroxidase (GPx), and total superoxide dismutase (Total-SOD) in liver, cardiac muscle, kidney, skeletal muscle (vastus lateralis), and duodenum of short-tailed field voles (Microtus agrestis), born and maintained at either 8 +/- 3 degrees C or 22 +/- 3 degrees C. CAT, GPx, and Total-SOD activities were determined at age 61 +/- 1.9 days. An increase in CAT activity in voles maintained at 8 +/- 3 degrees C was observed in skeletal muscle (71%) and kidney (20%), with both CAT and GPx activities significantly elevated (by 40 and 43%, respectively) in cardiac muscle, when compared to voles at 22 +/- 3 degrees C. Total-SOD activity and protein content did not differ significantly between groups in any tissue. We suggest that the compensatory increases in CAT (skeletal muscle, cardiac muscle, kidney) and GPx (cardiac muscle), but not Total-SOD activities, resulting from long-term cold exposure may reflect the elevated metabolic rate, and possibly also increased ROS production, at this time.

Response of the pupil to tropicamide is not a reliable test for Alzheimer disease.

OBJECTIVE: To confirm the putative hypersensitivity of the pupil to a weak mydriatic in persons with Alzheimer dementia. DESIGN: Twenty patients with Alzheimer dementia and 20 control subjects were examined. Automated binocular infrared pupillography was performed in the dark after instillation of 0.01% tropicamide or placebo. Ocular penetration of eye drops was assessed simultaneously using 2% fluorescein sodium as a tracer. SETTING: Rochester, Minn. SUBJECTS: Twenty patients and 20 cognitively normal control subjects from the Alzheimer's Disease Patient Registry of the Mayo Clinic, Rochester, Minn. MAIN OUTCOME MEASURE: Percent change in the diameter of the pupil following topical ocular instillation of a diluted concentration of the mydriatic drug tropicamide and penetration of topically applied fluorescein into the aqueous humor. RESULTS: No statistically significant difference was found between patients with Alzheimer disease and control subjects in either the mydriatic response of the pupil or in the rate of penetration of topically applied fluorescein. CONCLUSION: No evidence of pupillary hypersensitivity to an anticholinergic mydriatic drug was found in patients with Alzheimer disease or any evidence that this putative hypersensitivity could be used as an early, simple diagnostic test for Alzheimer disease.

Iron content correlates with peroxidase activity in cysteamine-induced astroglial organelles.

A subpopulation of astrocytes in periventricular brain regions and in cysteamine-treated neuroglial cultures contains cytoplasmic granules that exhibit an affinity for Gomori stains, orange-red autofluorescence, and non-enzymatic peroxidase activity. The autofluorescence and pseudoperoxidase activity are consistent with the presence of porphyrins and heme iron, respectively. In the present study, we employed diaminobenzidine cytochemistry, transmission electron microscopy, and energy-dispersive X-ray microanalysis (electron microprobe) in an attempt to correlate fine structure with the peroxidase activity and elemental composition of the cysteamine-induced inclusions in cultured astrocytes. In osmicated preparations, these membrane-bound inclusions varied greatly in size, were round or ovoid in shape, and exhibited an intensely electron-dense granular matrix. In non-osmicated preparations, many inclusions exhibited internal membranous partitions producing complex subcompartmentalization. Diaminobenzidine reaction product, indicative of endogenous peroxidase activity, was occasionally observed distributed diffusely throughout the granule matrix. More commonly, peroxidase activity was restricted to specific intraorganellar compartments. Elemental iron was detected in the inclusions by electron microprobe analysis. The presence and concentration of iron in these organelles correlated closely with the presence and intensity of diaminobenzidine staining, suggesting that redox-active iron mediates the pseudoperoxidase reactions in these cells. Cysteamine-induced derangements of porphyrin-heme biosynthesis may be responsible for the proliferation of iron-containing gliosomes in these astrocytes.

Measurement of fluorescein and fluorescein monoglucuronide in the living human eye.

Fluorescein monoglucuronide is a fluorescent metabolite of fluorescein, and is 1/3 to 1/34 as fluorescent as fluorescein, depending on the wavelength of excitation. After systemic administration, fluorescein glucuronide reaches concentrations many times greater than fluorescein. In order to study the effect of fluorescein glucuronide on the measurement of ocular dynamics, we devised a technique to measure fluorescein and fluorescein glucuronide in the anterior segment of the living human eye. Concentrations of each fluorophore were determined by differential spectrofluorophotometry from measurements at excitation wavelengths of 457.9 nm and 488.0 nm. Measurements were made on normal volunteers after oral and intravenous administration of fluorescein. Fluorescein was the dominant fluorophore during the first hour, while fluorescein glucuronide became dominant after 3 hours. By 6 hours there was 10 to 30 times more fluorescein glucuronide than fluorescein in the anterior chamber after oral administration, and three to ten times more after intravenous administration. The blood aqueous diffusion coefficient kd estimated from the apparent concentration of fluorescein measured at 457.9 nm was consistently greater than kd estimated from measurements at 488.0 nm. Estimates of kd, which were made on the basis of concentrations of fluorescein determined from measurements at both wavelengths, were lower than estimates based on measurements at either wavelength. These results indicate that wavelength of excitation may influence the determination of ocular parameters when systemic fluorescein is used. Care must be taken in the interpretation of measurements when metabolites of a fluorophore can interfere with measurement of the fluorophore itself.

A scanning ocular spectrofluorophotometer.

We describe an instrument called a scanning ocular spectrofluorophotometer (SOSF) that measures fluorescence in a two-dimensional cross-section through the anterior chamber and cornea and provides the ability to change excitation and emission wavelengths rapidly. The output of a xenon arc lamp is filtered by a diffraction grating monochromator which has a bandpass of 4 nm and a range of 400 to 800 nm. Light emitted from the fluorophore is filtered by a variable wavelength interference filter which has a bandpass of approximately 11 nm and a range of 400 to 700 nm. To demonstrate the versatility of the instrument, we measured the spectra of fluorescein, fluorescein glucuronide and rhodamine B in the anterior chambers and corneas of pigmented rabbits after topical administration. We also measured simultaneously and independently the redistribution and disappearance of a mixture of fluorescein-labeled dextran and rhodamine B after intracameral injection. Rhodamine B was very rapidly absorbed by the cornea and lens while fluorescein-dextran was not measurable in the cornea before 4 hr. The SOSF provides a means of carrying out spectrofluorophotometry in the living eye and carrying out kinetic experiments which would otherwise be awkward or impossible.

A new video pachometer.

PURPOSE: Many studies of the cornea would benefit from a simple, objective method to measure corneal thickness. In this study, a new optical pachometer based on video and computer technology was designed and tested. METHODS: The slit beam of a photographic slit lamp was monitored with a video camera through one half of the biomicroscope. When the slit was properly aligned with the cornea, the operator triggered a flash, and one video frame that included the flash was captured. A custom software package detected epithelial and endothelial edges. Corneal thickness was calculated from the median corneal image width and image widths from similar measurements of contact lenses with known thicknesses. Corneal thickness was measured in 25 subjects by using this new instrument and was compared to thickness measured by using a conventional Haag-Streit pachometer. RESULTS: Corneal thickness in the 25 subjects measured on the new instrument was 512+/-20 microm and 515-/+21 microm in the right and left eyes, respectively (mean+/-SD). Thickness of the same corneas measured on the Haag-Streit pachometer was 530+/-22 microm and 534+/-20 microm in right and left eyes, respectively. The average SD of 10 consecutive measurements was 6.6 microm and 6.7 microm on the video and Haag-Streit pachometers, respectively (n = 50 corneas). CONCLUSIONS: The video pachometer provides a fast, objective means of measuring corneal thickness. It is simple to use and provides precision equal to that of the Haag-Streit pachometer.

Intraocular pressure in rabbits by telemetry II: effects of animal handling and drugs.

PURPOSE: To measure under carefully controlled conditions the effects in the rabbit eye of commonly used therapeutic agents for glaucoma. METHODS: Rabbits were outfitted in one eye with an implantable telemetric pressure transducer and monitored for several months under controlled conditions of light/ dark and handling. Effects of tonometry, handling, water drinking, and instillation of topical ophthalmic medications on intraocular pressure were recorded during each 24-hour day/night cycle. RESULTS: Pneumatonometry, animal handling, and water drinking all had an effect on intraocular pressure that in many instances was of the same magnitude as the effects of pharmacologic agents. Dorzolamide and timolol caused a sustained reduction of intraocular pressure during the nocturnal period. Epinephrine had a biphasic effect, causing an immediate pressure elevation followed by a prolonged depression. Apraclonidine, latanoprost, and pilocarpine had no measurable effect. CONCLUSIONS: Continuous telemetric measurement of intraocular pressure in rabbits permits the measurement of uncontrollable artifacts that occur with tonometric measurements and animal handling. If environmental conditions are rigidly controlled, this method is very sensitive for detecting therapeutic effects of candidates for ocular hypotensive drugs. When healthy animals are used, the method appears to be more sensitive for drugs that affect aqueous humor formation than for drugs that affect aqueous humor outflow resistance.