Influence Intraocular Pressure Research Articles

Pathological Eye Growth in Myopia: a Limited Review on Endocrine Physiology for Future Research

Purpose: Myopia or short-sightedness: first manifests in school-children (early-onset), and also in young adults (late-onset). Pathological myopia can lead to stretching of the eyeball to the point of blindness from a detached retina. This title presents a preliminary understanding of endocrine, juxtacrine, and paracrine factors: hoping to stimulate further research and enable early therapeutic intervention. Background: The optical stimulus for eye growth is a blurred image on the retina that results from under-focused accommodation of the internal crystalline lens. Neural signals and biochemical messaging from the retina and vascular choroid provide local impetus to alter collagen structure in the outer white sclera of the eye. In persons that develop highly myopic refractive error, additional factors from blood and tissue chemistry, might influence intra-ocular pressure (IOP), posited to influence eyeball elongation. New research shows that GABA and dopamine are involved, but other factors remain unexplored. Eye Physiology: Human sclera has developmental origination same as any other connective tissue derived from the neural crest and mesoderm. Bundles of collagen fibers exist in the white opaque sclera and are more stringently oriented in the dome of the clear, transparent cornea. “Deformation compliance” of the sclera is governed by complexity of the collagen architecture, and “reduced scleral rigidity” is a known factor for myopic elongation, but developmental physiology is not well understood. Muscular contraction is required for sustained eye focusing to objects located at normal working distances. Short-term contractions can reduce IOP but increased muscle density from sustained near accommodation can promote progression of myopia. This implicates nitric oxide and calcium channels, and a role for associated biochemical and nutritional agonists and antagonists. Endocrine Influences: In his 1954 lecture to the Royal College of Surgeons, Dr. Howard C. Naffziger pointed to all forms of “ocular protrusion,” not just “thyroid exophthalmos,” as being physiologically related. A 2016 review paper on autonomic nervous physiology, aside from sympathetic (adrenergic) and parasympathic (collinergic) control, also implicates Substance P (SP), Vasoactive Intestinal Peptide (VIP), and Phospholipase C (PC). These topics are further described in limited detail. SP is a neuropeptide of the tachykinin family, is released from the terminals of sensory nerves, and regulates emotion (hypothalamus, amygdala, and the periaqueductal gray). It is also a vasodilator dependent on release of nitric oxide. Experimental eye physiology and clinical research pertaining to these topics appears warranted. VIP regulates cardiac contractions, relaxes smooth muscle of the trachea, and affects prolactin secretion by the pituitary gland. Cardiac contractions lead to pulsations of eye pressure about three times in two seconds, and pulmonary effects on IOP occur once every five seconds. Research into these mechanisms requires cross-disciplinary collaborations. PC is a membrane-associated enzyme that cleaves dietary phospholipids and has downstream effects on calcium channels. Binding to blood platelets, of agonists such as thrombin, epinephrine, or collagen: activates PC to release arachidonic acid from cleavage of phosphatidylinositol and phosphatidyl choline. Behavioral effects include visual attention-span and memory: both of which also concern education of children, and effectiveness of adults at work. Conclusions: The author is pleased to report growing interest and evidence for endocrine influences upon the outer coat of the eye (cornea and sclera). A 2022 study on “keratoconus” from Texas and Oklahoma provides in-vitro as well as in-vivo data, suggesting the existence of what they call, the Hypothalamic-Pituitary-Adrenal-Corneal axis. Effective communication across university disciplines and clinic doctors appears necessary for further progress. Funding: The author received no funds from Federal or State granting mechanisms, and no wages from corporate employers. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Association of Urinary Sodium Excretion with Glaucoma and Related Traits in a Large United Kingdom Population

Excessive dietary sodium intake has known adverse effects on intravascular fluid volume and systemic blood pressure, which may influence intraocular pressure (IOP) and glaucoma risk. This study aimed to assess the association of urinary sodium excretion, a biomarker of dietary intake, with glaucoma and related traits, and determine whether this relationship is modified by genetic susceptibility to disease. Cross-sectional observational and gene-environment interaction analyses in the population-based UK Biobank study. Up to 103 634 individuals (mean age: 57 years; 51% women) with complete urinary, ocular, and covariable data. Urine sodium:creatinine ratio (UNa:Cr; mmol:mmol) was calculated from a midstream urine sample. Ocular parameters were measured as part of a comprehensive eye examination, and glaucoma case ascertainment was through a combination of self-report and linked national hospital records. Genetic susceptibility to glaucoma was calculated based on a glaucoma polygenic risk score comprising 2673 common genetic variants. Multivariable linear and logistic regression, adjusted for key sociodemographic, medical, anthropometric, and lifestyle factors, were used to model associations and gene-environment interactions. Corneal-compensated IOP, OCT derived macular retinal nerve fiber layer and ganglion cell-inner plexiform layer (GCIPL) thickness, and prevalent glaucoma. In maximally adjusted regression models, a 1 standard deviation increase in UNa:Cr was associated with higher IOP (0.14 mmHg; 95% confidence interval [CI], 0.12-0.17; P<0.001) and greater prevalence of glaucoma (odds ratio, 1.11; 95% CI, 1.07-1.14; P<0.001) but not macular retinal nerve fiber layer or ganglion cell-inner plexiform layer thickness. Compared with those with UNa:Cr in the lowest quintile, those in the highest quintile had significantly higher IOP (0.45 mmHg; 95% CI, 0.36-0.53, P<0.001) and prevalence of glaucoma (odds ratio, 1.30; 95% CI, 1.17-1.45; P<0.001). Stronger associations with glaucoma (P interaction=0.001) were noted in participants with a higher glaucoma polygenic risk score. Urinary sodium excretion, a biomarker of dietary intake, may represent an important modifiable risk factor for glaucoma, especially in individuals at high underlying genetic risk. These findings warrant further investigation because they may have important clinical and public health implications. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Can Psychologic Stress Elevate Intraocular Pressure in Healthy Individuals?

To investigate if a stress event can influence intraocular pressure (IOP) in a group of healthy individuals. Case-control study. A total of 28 healthy subjects were included: 17 in the stress group and 11 in the control group. The Trier Social Stress Test (TSST) is a tool to evaluate cortisol response to psychologic stimulation based on the stress induced by public speaking. All participants underwent a modified diurnal tension curve (DTC) 1 week before the TSST, with 3 IOP measurements performed between 8:00 am and 2:00 pm. We evaluated the response to the TSST measuring the levels of salivary cortisol, IOP, and heart rate before, immediately after, and 40 minutes after TSST. The State Trait Anxiety Inventory (STAI) was applied to evaluate the levels of anxiety at the same time intervals. Changes in IOP (mmHg), salivary cortisol, heart rate, and STAI scores. At baseline, there were no significant differences between case and controls regarding age (52.2 ± 6.26 vs. 53.8 ± 8.4 years, P= 0.661), gender (52.94% male vs. 45.45% female, P= 0.669), and ethnicity. Salivary cortisol (6.8 nmol/l, P < 0.001) and heart rate (7.2 beats/min, P= 0.035) increased significantly after the TSST. We observed a mean IOP increase of 1.0 mmHg (right eye, P= 0.003) and 1.1 mmHg (left eye, P= 0.004) when comparing IOP measurements obtained during the DTC and immediately after TSST. In addition, 35% (6/17) of the subjects in the TSST group showed an IOP increase higher than 2 mmHg after the test compared with 18% (2/11) in the control group. The STAI state score significantly increased after the stress event compared with baseline (P= 0.026) and decreased from poststress to the recovery period (P= 0.006) in the TSST group. The control group did not show significant changes in IOP, heart rate, salivary cortisol levels, and STAI scores. Significant elevations of IOP, salivary cortisol, STAI scores, and heart rate occurred after inducing psychologic stress with TSST in a group of healthy individuals.

Acute Ocular Effects of Sphenopalatine Ganglion Nerve Block.

Aim and objectiveThe goal of this study was to measure acute ocular effects in patients undergoing routine sphenopalatine ganglion (SPG) nerve block for headache. Projections from the SPG influence blood flow to the eye which may influence intraocular pressure (IOP). There are limited animal and human studies investigating the relationship between the SPG and its effect on the eye.Materials and methodsThis was a single-site, investigator-initiated, single-visit, prospective study. Participants were aged 18–85 years old who had consented to SPG nerve block for headache. The primary outcome measures were change in near visual acuity (NVA) and IOP pre-procedure to immediately post-procedure. Additional data collected included pupil diameter and presence of any ocular or visual complaints.ResultsA total of 13 patients were enrolled in the study. Average pre-procedure IOP was 14.2 mm Hg [standard deviation (SD) 3.8] in the right eye and 13.7 mm Hg (SD 3.2) in the left eye. Average post-procedure IOP was 14.8 mm Hg (SD 3.8) in the right eye and 14.2 mm Hg (SD 2.9) in the left eye. Neither the right nor left eye experienced a statistically significant change in IOP after SPG block. There were no statistically significant changes in average NVA or pupil diameter in either eye. There were no adverse events.Conclusion and clinical significanceThis pilot study suggests no significant acute changes in IOP or other ocular parameters after SPG block for headache disorders and supports the fact that the procedure is safe as it relates to ocular health. The ocular effects of SPG blockade merit further study in a larger cohort of patients.How to cite this articleSiegel DT, Ertel MK, Patnaik JL, et al. Acute Ocular Effects of Sphenopalatine Ganglion Nerve Block. J Curr Glaucoma Pract 2020;14(2):57–60.

Evaluation of the Effect of Body Position on Intraocular Pressure Measured with Rebound Tonometer

Objectives:It is important to determine variables that influence intraocular pressure (IOP) measurement. This study aimed to evaluate the effect of body position on IOP.Materials and Methods:The study included 52 right eyes of 52 patients who presented to the ophthalmology department of our hospital and had no ocular disease except refractive errors. IOP was measured with an Icare PRO tonometer while patients were in sitting, standing, and supine positions, with intervals of 10 minutes between the positions. Correlations between the results were evaluated using Spearman’s correlation analysis and Wilcoxon tests.Results:Thirty-six of the 52 patients were female, 16 were male. Mean age was 31.65±6.30 (23-47) years. Mean IOP values in the sitting, standing, and lying positions were 17.76±3.41 (12.70-25.60) mmHg, 17.10±3.27 (11.50-25.20) mmHg, and 18.46±4.67 (10.50-29.40) mmHg, respectively. There were no statistically significant differences between measurements taken in the different positions (p=0.112, p=0.472, p=0.071). We observed that there was no relationship between age and body position (p>0.45, p>0.79, p>0.77) or between gender and position (p>0.59, p>0.69, p>0.54).Conclusion:Gender and age had no effect on IOP measured in different body positions. There were also no significant differences between IOP values measured in the different positions. Therefore, we believe the portable Icare PRO tonometer can be used for patients who are confined to bed and will provide IOP measurements that are concordant with values obtained while sitting.

Clinical assessment of intraocular pressure: a whole-eye dynamic model

The aim of this work is to provide a quantitative description of how geometrical and material properties of ocular tissues and fluids influence intraocular pressure (IOP).

The Eyes Have It: Factors that Influence Intraocular Pressure (IOP).

The Eyes Have It: Factors that Influence Intraocular Pressure (IOP).

Oxindole-based intraocular pressure reducing agents

The study represents the new findings at the crossroads of chemistry and medicine, particularly between medicinal and organic chemistry and ophthalmology. In this work we describe how the chemical reactivity of indolinone scaffold may be used to create small molecule ligands with strong biological response comparable with and larger than that of endogenous hormone. The synthesis of oxindole-based melatonin and 5-methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT) analogues was proposed and their ability to influence intraocular pressure (IOP) was studied in vivo. Time-dependent study revealed the prolonged effect (more than 6h) of the lead-compound. This effect in combination with high IOP reducing effect (41±6%) in low concentrations of the active compound (0.1wt%) and with high water solubility represents a great potential of low-cost oxindole derivatives as potent antiglaucoma agents.

Corneal properties and glaucoma: a review of the literature and meta-analysis.

Studies have suggested that corneal biomechanical properties influence intraocular pressure (IOP) measurements, namely central corneal thickness (CCT) and corneal hysteresis (CH). The present study aimed to investigate the associations of CH and CCT with glaucoma development. We performed a review of the literature and meta-analysis of observational studies (2006-2016) that included both adult glaucoma patients and controls and reported CCT and CH as outcomes. Nineteen studies were conside red eligible, and the mean difference (MD) between groups (patient and control) for both variables was used for statistical analyses. A total of 1,213 glaucoma and 1,055 healthy eyes were studied. Quan titative analysis suggested that CH was significantly lower in the glaucoma group than in the control group (MD=-1.54 mmHg, 95% CI [-1.68, -1.41], P<0.0001). Additionally, CCT was significantly lower in the glaucoma group than in the control group (MD=-8.49 µm, 95% CI [-11.36, -5.62], P<0.001). Corneal properties appear to differ between glaucoma patients and healthy controls. Our results emphasize the importance of corneal biomechanical properties in IOP interpretation and should support further studies on the influence of CH and CCT in glaucoma screening and diagnosis.

Mathematical modeling of aqueous humor flow and intraocular pressure under uncertainty: towards individualized glaucoma management

Purpose: The aim of the proposed analysis is to provide both a qualitative description and a quantitative assessment of how variations in aqueous humor (AH) flow parameters influence intraocular pressure (IOP) and the outcome of IOP-lowering medications.Methods: We developed a mathematical model that describes the steady-state value of IOP as the result of the balance between AH production and drainage. We performed stochastic simulations to assess the influence of different factors on the IOP distribution in ocular normotensive and ocular hypertensive subjects and on the IOP reduction following medications.Results: The distribution of the relative frequency of a given IOP value for ocular normotensive subjects fits a right-skewed Gaussian curve with a frequency peak of 25% at 15.13 mmHg and a skewness of 0.2, in very good agreement with the results from a population-based study on approximately 12,000 individuals. The model also shows that the outcomes of IOP-lowering treatments depend on the levels of pre-treatment IOP and blood pressure. The model predicts mean IOP reductions of 2.55 mmHg and 4.31 mmHg when the pre-treatment IOP mean values are 15.13 mmHg and 20.12 mmHg, respectively; these predictions are in qualitative and quantitative agreement with clinical findings.Conclusion: These findings may help identify patient-specific factors that influence the efficacy of IOP-lowering medications and aid the development of novel, effective, and individualized therapeutic approaches to glaucoma management.

Increased Intraocular Pressure and Hyperglycemic Level in Diabetic Patients.

PurposeTo determine whether hyperglycemic levels as determined from high hemoglobin A1c (HbA1c) levels influence intraocular pressure (IOP) in patients with non-proliferative diabetic retinopathy (NPDR).MethodsA retrospective chart review was performed on subjects with a diagnosis of NPDR and a corresponding HbA1c level measured within 90 days before or after an IOP measurement over a two-year period. Exclusion criteria included a diagnosis of glaucoma or treatment with IOP lowering medications or oral or topical steroids.ResultsUsing 14.5mmHg as a baseline mean value for IOP, 42 subjects had an IOP < 14.5mmHg and mean HbA1c of 8.1±1.1, while 72 subjects had an IOP ≥ 14.5mmHg and a mean HbA1c of 9.0±2.1. Although there was an overlap in the confidence intervals, a significant difference (P = 0.01) in the mean HbA1c level was observed in regression analysis between the two groups. Importantly, diabetic subjects with elevated HbA1c levels rarely (<1%) exhibited reduced IOP levels.ConclusionsDiabetic subjects with elevated HbA1c levels exhibited significantly higher IOPs compared to those with lower HbA1c levels. Findings from this study indicate an association between hyperglycemia and elevated IOP and that poor glycemic control may contribute to increased IOP levels in long-term diabetic patients.

Modern disposable hydrogel contact lens removal has a minimal effect on intraocular pressure

To determine whether the removal of modern disposable hydrogel contact lenses may influence intraocular pressure (IOP) measurement, and if so, how long the effect may last. Twenty-five healthy experienced contact lens wearers aged 19-25 inserted their lenses at least 30min prior to the study. Each participant was asked to remove a contact lens from one eye (control eye, selected at random) upon commencement of the study, and then to remove the lens in the other eye (lens-wearing eye) after a 30min washout period. IOP was measured immediately in both eyes using non-contact tonometry, then repeated every 3min for 12min. To determine the change in IOP due to lens removal, the IOP in the lens-wearing eye was compared to the control eye using paired t-tests at each time point. The IOP was significantly higher in the lens-wearing eye immediately following lens removal (0.7±1.0mmHg, t(24)=3.46, p<0.01), but was within baseline values at 3min (0.2±1.0mmHg, t(24)=0.84, p=0.41), 6min (0.3±1.1mmHg, t(24)=1.39, p=0.18), 9min (0.3±1.2mmHg, t(24)= 1.14, p=0.27) and 12min (-0.1±0.9mmHg, t(24)=-0.49, p=0.63, paired t-test). There was a slight statistically significant increase in IOP following contact lens removal, with a maximum duration of 3min. Given the small magnitude of the change in IOP, and its transient nature, there appears to be no clinical reason to delay IOP measurements following the removal of modern disposable hydrogel contact lenses.

Factors that Influence Intraocular Pressure Changes after Myopic and Hyperopic LASIK and Photorefractive Keratectomy: A Large Population Study

To describe the factors that influence the measured intraocular pressure (IOP) change and to develop a predictive model after myopic and hyperopic LASIK and photorefractive keratectomy (PRK) in a large population. Retrospective, observational case series. Patients undergoing primary PRK or LASIK with a refractive target of emmetropia between January 1, 2008, and October 5, 2011. The Optical Express database was queried for all subjects. Data were extracted on procedure specifics, preoperative central corneal thickness (CCT), IOP (using noncontact tonometry), manifest refraction, average keratometry, age, gender, and postoperative IOP at 1 week, 1 month, and 3 months. A linear mixed methods model was used for data analysis. Change in IOP from preoperatively to 1 month postoperatively. A total of 174 666 eyes of 91 204 patients were analyzed. Hyperopic corrections experienced a smaller IOP decrease than myopic corrections for both PRK and LASIK (P<0.0001). Patients who underwent LASIK had a 0.94 mmHg (95% confidence interval [CI], 0.89-0.98) greater IOP decrease than patients who underwent PRK (P<0.0001), reflecting the effect of the lamellar flap. The decrease in IOP was linearly related to preoperative manifest spherical equivalent (MSE) for myopic PRK and LASIK (P<0.0001), weakly correlated with preoperative MSE after hyperopic LASIK, and not related to preoperative MSE after hyperopic PRK. The single greatest predictor of IOP change was preoperative IOP across all corrections. By using the available data, a model was constructed to predict postoperative IOP change at 1 month; this was able to explain 42% of the IOP change after myopic LASIK, 34% of the change after myopic PRK, 25% of the change after hyperopic LASIK, and 16% of the change after hyperopic PRK. Myopic procedures lower measured IOP more than hyperopic procedures; this decrease was proportional to the amount of refractive error corrected. Independent of the refractive correction, the creation of the lamellar LASIK flap decreased measured IOP by 0.94 mmHg. A best-fit model for IOP change was developed that may allow better interpretation of post-laser vision correction IOP values.

Factors Influencing Intermethod Agreement Between Goldmann Applanation, Pascal Dynamic Contour, and Ocular Response Analyzer Tonometry

To examine factors that influence intraocular pressure (IOP) measurement agreement between Goldmann applanation (GAT), Ocular Response Analyzer (ORA), and Pascal Dynamic Contour tonometers (DCT). In subjects who were diagnosed with primary open-angle glaucoma, ocular hypertension, glaucoma suspect, and normal, we used ORA, DCT, and GAT to obtain corneal hysteresis (CH), corneal resistance factor (CRF), ocular pulse amplitude, and 4 IOP values (ORA-IOPcc; ORA-IOPg; DCT-IOP; and GAT-IOP.) We also obtained corneal curvature, corneal thickness, axial length, retinal nerve fiber layer thickness, visual field parameters, diabetes diagnostic status, and topical IOP-lowering treatment data. Analysis of variance, Bland-Altman, and regression analyses were used to examine IOP agreement and associated factors. In 243 eyes of the 243 subjects, mean DCT-IOP (18.73±4.92) was not different from mean ORA-IOPcc (18.96±5.41) but both were significantly higher than ORA-IOPg (16.97±5.49) and GAT-IOP (16.37±4.97). In multivariate regression models, intermethod differences between IOPg, IOPcc, and DCT-IOP were explained almost completely by variations in CH, CRF, and level of IOP (r(2)=0.98 to 0.99); conversely, intermethod variability between GAT-IOP and the other 3 IOP metrics was only partially explained by the factors evaluated in this study (r(2)=0.31 to 0.65). Consistent with other studies, we found that the 4 IOP variables examined in this study are not interchangeable. The most consistent confounders of IOP measurement agreement were the ORA-measured corneal parameters, CH and CRF. Thus, accounting for these factors may be important in efforts to obtain accurate transcorneal estimates of IOP.

Correlation of Endothelin-1 Concentration in Aqueous Humor with Intraocular Pressure in Primary Open Angle and Pseudoexfoliation Glaucoma

Endothelin-1 (ET-1) has been found in elevated concentrations in the aqueous humor of glaucoma patients. Indirect evidence from animal studies suggests that ET-1 might directly influence intraocular pressure (IOP). The aim of this study was to determine whether ET-1 concentrations in aqueous humor of cataract and glaucoma patients correlate with IOP. Aqueous humor and blood samples from patients with either cataract (control, n = 38), primary open angle glaucoma (POAG, n = 35), or pseudoexfoliation glaucoma (PEXG, n = 21), without other ocular or systemic disease, were collected during routine cataract surgery or trabeculectomy. ET-1 concentration was determined by an ET-1 ELISA kit. IOP was measured preoperatively by standard Goldmann applanation tonometry. All statistical analysis was performed using commercial predictive analytics software. Both IOP and ET-1 concentration in aqueous humor were significantly increased in POAG (23.4 ± 6.8 mm Hg, 5.9 ± 2.9 pg/mL) and PEXG (24.3 ± 8.8 mm Hg, 7.7 ± 2.1 pg/mL) compared with control (15.0 ± 2.9 mm Hg, 4.3 ± 2.4 pg/mL). No difference was detected for plasma ET-1 concentrations. IOP and ET-1 in the aqueous humor were significantly correlated (R = 0.394, R² = 0.155, P < 0.001), although no correlation was found between IOP and ET-1 in blood plasma or between ET-1 in aqueous humor and ET-1 in plasma. In this study, a small but highly significant correlation between IOP and the ET-1 concentration in the aqueous humor was found. Although no causative relationship can be deduced from this, ocular ET-1 effects on IOP control may merit further investigation.

How Might Corneal Elasticity Help Us Understand Diabetes and Intraocular Pressure?

To determine how changes in corneal elasticity/stiffness might influence intraocular pressure (IOP) readings in diabetic patients. A systematic review of the literature was performed to understand the conflicting relationship between diabetes, elevated IOP, and glaucoma progression. Diabetic patients have been found to have statistically significant higher IOP readings in some population-based studies compared to non-diabetics. Insulin resistance states, hyperglycemia and glycosylated hemoglobin have been correlated with higher IOP (1 mmHg) measurements in diabetic patients. In the Ocular Hypertension Treatment Study (OHTS), a self reported history of diabetes was found to be protective against the progression of primary open-angle glaucoma. Small differences in IOP measurements in diabetic patients may be due to corneal stiffening, as demonstrated by the protective effect of glucose-mediated collagen cross-linking against the manifestation and keratometric progression of keratoconus. Different collagen cross-linking agents may induce different degrees of corneal stiffening, which can result in differences in measured IOP. Glucose-mediated corneal stiffening due to collagen cross-linking might be responsible for IOP overestimation in diabetic patients. Corneal stiffening might explain why diabetic eyes tend to have higher IOP readings in large population-based studies and why those with ocular hypertension have a reduced risk for glaucoma progression.

A Comparison of the Effects of Propofol and Sevoflurane Anesthesias on Intraocular Pressure during Laparoscopic Hysterectomy

Background: Laparoscopic surgery in the Trendelenburg position affects the cardiopulmonary system and may also influence intraocular pressure (IOP). The purpose of this study was to compare the effects of propofol and sevoflurane anesthesias on IOP change during laparoscopic hysterectomy. Methods: Thirty-one women were randomly allocated to either a propofol (P-group, n = 15) intravenous anesthesia group or a sevoflurane (S-group, n = 16) inhaled anesthesia group with fentanyl-O/-vecuronium. Heart rate, mean arterial pressure, plateau airway pressure, ETC, and IOP were measured before induction (T1), 10 min after induction (T2), 10 min after pneumoperitoneum in the Trendelenburg position (T3), and 5 min after pneumoperitoneum deflation in the horizontal position (T4). Results: IOP was significantly decreased in both groups after induction. IOP was increased in both groups after pneumoperitoneum in the Trendelenburg position, but IOP in the sevoflurane group was significantly higher than that in the propofol group. Conclusions: Propofol intravenenous anesthesia may be a better choice for IOP control during laparoscopic surgery.

Isolation and evaluation of target cells in glaucoma research: Hormone receptors and drug responses

To investigate the actions of drugs and hormones which influence intraocular pressure (IOP), we have been measuring receptor binding characteristics and dose-response effects using individual target cells from the anterior segment. Similar methods have also permitted us to develop sensitive radio-receptor assays for glucocorticoids and beta adrenergic antagonists. These methods provide a means to obtain new and potentially useful information regarding the efficacy and specificity of ocular drug therapy.

Aqueous humour turnover and intraocular pressure during menstruation.

Both intraocular pressure and aqueous humour turnover rate were determined at intervals over three months in three females in order to investigate whether a correlation existed between these variables and the menstrual cycle. Not only was there a lack of correlation between intraocular pressure or aqueous humour flow rate and menses but intraocular pressure and aqueous humour flow rate were also not related to each other. If pharmacologically administered doses of progesterone or oestrogen influence intraocular pressure, the present data indicate that the effect is probably mediated through effects on the aqueous outflow pathways.