Short-term effects of cyclopentolate and tropicamide eye drops on macular choroidal thickness in myopic children.

BACKGROUND: To investigate the short-term effects of cyclopentolate and tropicamide eyedrops on choroidal thickness (ChT) in myopic children using placebo or low-dose atropine eyedrops. METHODS: The analysis included 242 myopic individuals (7-19 years) enrolled in two randomised placebo-controlled clinical trials of low-dose atropine eyedrops. Cycloplegia was induced using either one drop of 1% cyclopentolate (n = 161), two drops of 1% cyclopentolate (n = 32) or two drops of 1% tropicamide (n = 49). ChT measurements were taken using swept-source optical coherence tomography before and 30 min after administering the cycloplegic eye drops. A subset of 51 participants underwent test-retest measurements prior to cycloplegia. RESULTS: Mean changes in subfoveal ChT after two drops of tropicamide and one and two drops of cyclopentolate were -2.5 µm (p = 0.10), -4.3 µm (p < 0.001) and -9.6 µm (p < 0.001), respectively. Subfoveal ChT changes after one and two drops of cyclopentolate were significantly greater than the test-retest changes (test-retest mean change: -3.1 µm; p < 0.05), while the tropicamide group was not significantly different (p = 0.64). Choroidal thinning post-cyclopentolate was not significantly different between atropine and placebo treatment groups (p > 0.05 for all macular locations). The coefficient of repeatability (CoR) in the tropicamide group (range: 8.2-14.4 µm) was similar to test-retest (range: 7.5-12.2 µm), whereas greater CoR values were observed in the cyclopentolate groups (one drop: range: 10.8-15.3 µm; two drops: range: 12.2-24.6 µm). CONCLUSIONS: Cyclopentolate eye drops caused dose-dependent choroidal thinning and increased variation in pre- to post-cycloplegia measurements compared with test-retest variability, whereas tropicamide did not. These findings have practical implications for ChT measurements when cyclopentolate is used, particularly for successive measurements.

Effects of atropine and tropicamide on ocular biological parameters in children: a prospective observational study.

BACKGROUND: The effectiveness of cycloplegia in delaying the progression of myopia and its application in refractive examination in children have been extensively studied, but there are still few studies on the effects of atropine/tropicamide on ocular biological parameters. Therefore, the purpose of this study was to explore the effects of atropine/tropicamide on children's ocular biological parameters in different age groups and the differences between them. METHODS: This was a prospective observational study in which all school children were examined for dioptres and ocular biological parameters in the outpatient clinic, and 1% atropine or tropicamide was used for treatment. After examination, we enrolled the patients grouped by age (age from 2 to 12 years treated by atropine, 55 cases; age from 2 to 10 years treated by tropicamide, 70 cases; age from 14 to 17 years treated by tropicamide, 70 cases). The ocular biological parameters of each patient before and after cycloplegia were measured, and the difference and its absolute value were calculated for statistical analysis using an independent-samples t test. RESULTS: We compared the value and the absolute value of the differences in ocular biological parameters before and after cycloplegia in the same age group, and we found that the differences were not statistically significant (P > 0.05). There were significant differences in the corresponding values of AL, K1 and ACD among the different age groups (P < 0.05). Before cycloplegia, there were significant differences in AL, K, K1, K2 and ACD in different age groups (P < 0.05). However, the differences in AL, K, K1, K2 and ACD among different age groups disappeared after cycloplegia (P > 0.05). CONCLUSIONS: This study demonstrated that atropine/tropicamide have different effects on cycloplegia in children of different ages. The effects of atropine/tropicamide on ocular biological parameters should be fully considered when evaluating the refractive state before refractive surgery or mydriasis optometry for children of different ages.

Efficacy and safety of intraoperative use of tropicamide 0.02%/phenylephrine0.31%/lidocaine1% intracameral combination during pediatric cataract surgery.

BACKGROUND: To demonstrate the safety and efficacy of the intracameral use of tropicamide 0.02%/phenylephrine 0.31%/lidocaine 1% in pediatric cataract surgery, a combination widely used in adult patients but still off-label in children. METHODS: Design: two-center, prospective, observational study. SETTING: San Giuseppe Hospital, Milan and Meyer Children's Hospital, Florence. STUDY POPULATION: children from 0 to 4 years of age undergoing cataract surgery with or without intraocular IOL implantation, in the absence of clinically significant systemic conditions, history of ocular surgery, concurrent ocular medication, hypersensitivity to any of the substances and post-traumatic cataracts. During the surgery, patients received the combination drug after the primary access to the anterior chamber. Efficacy was evaluated by achieving an adequate mydriasis in order to perform capsulorhexis, while safety was assessed by recording vital signs (heart rate, blood pressure, respiratory rate, temperature) pre- and post-administration of the substance. RESULTS: This study included 53 surgical procedures of 36 patients: 41 eyes were left aphakic, while 12 eyes received primary IOL implantation. The pupil size was adequate to safely perform capsulorhexis in 52 procedures of 53. The difference in pupil enlargement was significant (6.0 ± 1.14 mm, P = < 0.001). There were no notable changes in vital parameters. CONCLUSIONS: The administration of intracameral tropicamide 0.02%/phenylephrine 0.31%/lidocaine 1% in pediatric cataract surgery is effective for obtaining an adequate mydriasis without any vital parameters changes throughout the procedure.

Comparison study between pilocarpine and tropicamide drops on corneal topography and their effect on IL-6 and TNF-α levels in tear.

Corneal stability is essential for contact lenses and refractive surgery. It seems that paralyzing eye drops or expansion of the ciliary muscle affect the radius of curvature and the strength of the cornea, and this effect is to increase the strength of the cornea during muscle spasm and decrease it in the relaxed state of the muscle. On the other hand, different factors (such as contact lens wear, ocular surface disorders, trauma, dry eye, and immunosuppression) could alter the immune defense mechanisms of the outer eye and permit microorganisms to invade the cornea. Therefore, the present study compared Pilocarpine and tropicamide drop on corneal topography and their effect on IL-6 and TNF-α levels in tear. This prospective study was performed on sixty normal and healthy eyes of sixty volunteers with a mean age of 38.19 years and without any ocular pathology. Volunteers were divided into two groups of thirty. In the first group, corneal topography of both eyes was measured before and 30 minutes after instillation of topical tropicamide 1% in only one eye. The other eye was the control eye, and no drop was given. The same routine was performed in the second group, except that subject received one drop of Pilocarpine 2% in one eye. Statistical comparison between groups for the central corneal power, corneal radius, and corneal astigmatism was performed using paired t-test. IL-6 and TNF-α levels in tear were analyzed using two Luminex commercial assays with Bio-Plex 200TM System (Bio-Rad, Hercules, California, USA). In group 1, no significant changes were found in corneal radius, power, and astigmatism. However, in group 2 subjects who received pilocarpine eye drops, the mean corneal radius value decreased significantly by 0.05 mm. The mean corneal power increased by +0.32 D. There was no significant difference change in corneal astigmatism in both groups. Evaluation of IL-6 levels in tears showed a significant difference between the control and treatment groups (P = 0.041). But no significant difference was observed between the Pilocarpine and the Tropicamide groups (P = 0.761). Evaluation of TNF-α level in tears also showed no significant difference between these groups (P = 0.088). Pilocarpine induced ciliary muscle contraction, which may cause pressure on the corneal limbus and scleral spur, resulting in changes in corneal curvature. But tropicamide eye drop did not affect corneal radius and other corneal parameters, and corneal topography can be carried out after the installation of tropicamide eye drop.

Early phase of pupil dilation is mediated by the peripheral parasympathetic pathway.

Pupil diameter fluctuates in association with changes in brain states induced by the neuromodulator systems. However, it remains unclear how the neuromodulator systems control the activity of the iris sphincter (constrictor) and dilator muscles to change the pupil size. The present study compared temporal patterns of pupil dilation during movement when each muscle was pharmacologically manipulated in the human eye. When the iris sphincter muscle was blocked with tropicamide, the latency of pupil dilation was delayed and the magnitude of pupil dilation was reduced during movement. In contrast, when the iris dilator muscle was continuously stimulated with phenylephrine, the latency and magnitude of rapid pupil dilation did not differ from the untreated control eye, but sustained pupil dilation was reduced until the end of movement. These results suggest that the iris sphincter muscle, which is under the control of the parasympathetic pathway, is quickly modulated by the neuromodulator system and plays a major role in rapid pupil dilation. However, the iris dilator muscle receives signals from the neuromodulator system with a slow latency and is involved in maintaining sustained pupil dilation.NEW & NOTEWORTHY By pharmacologically manipulating the pupil dilator and constrictor muscles of human eye separately, we found that the pupil constrictor muscle is a primary controller of rapid pupil dilation upon brain arousal. However, the pupil dilator muscle, which is innervated by the sympathetic nervous system and is generally considered as a major regulator of pupil dilation, is not involved in rapid pupil dilation, but was involved in long-lasting pupil dilation.

Iris stromal cell nuclei deform to more elongated shapes during pharmacologically-induced miosis and mydriasis.

Nuclear shape alteration in ocular tissues, which can be used as a metric for overall cell deformation, may also lead to changes in gene expression and protein synthesis that could affect the biomechanics of the tissue extracellular matrix. The biomechanics of iris tissue is of particular interest in the study of primary angle-closure glaucoma. As the first step towards understanding the mutual role of the biomechanics and deformation of the iris on the activity of its constituent stromal cells, we conducted an ex-vivo study in freshly excised porcine eyes. Iris deformation was achieved by activating the constituent smooth muscles of the iris. Pupillary responses were initiated by inducing miosis and mydriasis, and the irides were placed in a fixative, bisected, and sliced into thin sections in a nasal and temporal horizontal orientation. The tissue sections were stained with DAPI for nucleus, and z-stacks were acquired using confocal microscopy. Images were analyzed to determine the nuclear aspect ratio (NAR) using both three-dimensional (3D) reconstructions of the nuclear surfaces as well as projections of the same 3D reconstruction into flat two-dimensional (2D) shapes. We observed that regardless of the calculation method (i.e., one that employed 3D surface reconstructions versus one that employed 2D projected images) the NAR increased in both the miosis group and the mydriasis group. Three-dimensional quantifications showed that NAR increased from 2.52 ± 0.96 in control group to 2.80 ± 0.81 and 2.74 ± 0.94 in the mydriasis and miosis groups, respectively. Notwithstanding the relative convenience in calculating the NAR using the 2D projected images, the 3D reconstructions were found to generate more physiologically realistic values and, thus, can be used in the development of future computational models to study primary angle-closure glaucoma. Since the iris undergoes large deformations in response to ambient light, this study suggests that the iris stromal cells are subjected to a biomechanically active micro-environment during their in-vivo physiological function.

Moderate oxidative stress promotes epithelial-mesenchymal transition in the lens epithelial cells via the TGF-ß/Smad and Wnt/ß-catenin pathways.

The epithelial-mesenchymal transition (EMT) plays a significant role in fibrosis and migration of lens epithelial cells (LECs), and eventually induces posterior capsule opacification (PCO). In the past, it was generally believed that the TGF-ß/Smad pathway regulates lens EMT. A recent study found that attenuated glutathione level promotes LECs EMT via the Wnt/ß-catenin pathway, which suggests a more complex pathogenesis of PCO. To test the hypothesis, we used the mouse cataract surgery PCO model and tested both canonical Wnt/ß-catenin and TGF-ß/Smad signaling pathways. The results showed that both TGF-ß/Smad and Wnt/ß-catenin pathways were activated during the lens capsule fibrosis. Compared with the freshly isolated posterior capsule, the expression level of phosphorylated Smad2 was highest at day3 and then slightly decreased, but the expression level of Wnt10a gradually increased from day0 to day7. It shows that these two pathways are involved in the lens epithelium's fibrotic process and may play different roles in different periods. Subsequently, we established oxidative stress-induced EMT model in primary porcine lens epithelial cells and found that both the TGF-ß/Smad and Wnt/ß-catenin pathways were activated. Further study suggests that block Wnt/ß-catenin pathway using XAV939 alone or block TGF-ß/Smad pathway using LY2109761 could partially block pLECs fibrosis, but blocking Wnt/ß-catenin and TGF-ß/Smad pathway using combined XAV939 and LY2109761 could completely block pLECs fibrosis. In conclusion, this study demonstrates that both TGF-ß/Smad and canonical Wnt/ß-catenin pathways play a significant role in regulating epithelial-mesenchymal transformation of lens epithelial cells but might be in a different stage.

The effect of topical tropicamide and phenylephrine on macular and peripapillary microvasculature: an optical coherence tomography angiography study.

PURPOSE: To evaluate the effect of topical tropicamide 1% and phenylephrine 2.5% instillation on macular and peripapillary microvasculature measurements with optical coherence tomography angiography (OCTA). METHODS: Forty eyes of 40 consecutive healthy adults with no known systemic or ocular disease were recruited for this prospective consecutive case study. After complete ophthalmological examination, all patients underwent OCTA measurements (OptoVue Inc, Freemont, CA, USA) to assess foveal avascular zone (FAZ) area, FAZ perimeter, acircularity index of FAZ, foveal density, vessel density of superficial and deep capillary plexus and peripapillary capillary plexus. 6 × 6 mm macular and 4.5 × 4.5 mm peripapillary OCTA images were undertaken before and 30 min after instillation of tropicamide (20 eyes) or phenylephrine (20 eyes) instillation to the right eye, and these were compared to each other and to fellow control eye. RESULTS: 15 male and 25 female patients with a mean age of 43.3 (18-60) years were recruited for the study. Superficial, deep and peripapillary capillary plexus measurements of tropicamide 1% and phenylephrine 2.5% instilled right eyes and left control eyes were similar before and 30 min after instillation (P > 0.05 for all). FAZ assessment tool variables were also similar before and after instillation (P > 0.05 for all) for both eyes. CONCLUSION: Topical pupillary dilatation with tropicamide 1% and phenylephrine 2.5% did not affect macular and peripapillary OCTA measurements. Follow-up OCTA images in retina and glaucoma patients can be captured with a dilated or undilated pupil which seems not to be affected by tropicamide or phenylephrine.

Evaluation of the Effect of Cycloplegia on Anterior Chamber Depth in Cataract Patients Using Optical Low-Coherence Reflectometry.

PURPOSE: The study was performed to study the effect of cycloplegia on anterior chamber depth (ACD) in cataract eyes. One instrument (Lenstar) was used for all measurements. METHODS: Anterior chamber depth calculations were taken with the Lenstar in cataract eyes with a mean age of 71.9±8.8 years before instilling cycloplegic drops. Two drops of Tropicamide were then instilled in each eye and measurements were retaken between 30 to 45 min later. RESULTS: Cycloplegia with a mild agent used routinely in this practice location showed a statically significant effect on increasing ACD by 0.0647±0.01 in the OD and 0.0758±0.02 in the OS. CONCLUSIONS: Anterior chamber depth can be important in the final refractive result postcataract surgery. The results of a change in effective lens position would be most significant in higher intraocular lens powers.

Higher-Order Aberrations After Cyclopentolate, Tropicamide, and Artificial Tear Drops Application in Normal Eyes.

PURPOSE: To determine the effect of cyclopentolate, tropicamide, and artificial tear drops on higher-order aberrations (HOAs) in normal eyes with OPD-Scan III (Nidek Inc., Tokyo, Japan). METHODS: In this study, 189 eyes of individuals aged 20 to 35 years were selected as samples. Inclusion criteria were a corrected visual acuity of 20/20 or better, a minimum size of about 5 mm for the pupil in the dark, hyperopia and myopia less than 5 D, and astigmatism less than 2 D. Moreover, participants with pathological eye problems, a history of intraocular surgery, and ocular diseases affecting the accommodation, pupil size, and corneal surface were excluded. Higher-order aberrations of the participants were assessed by the OPD-Scan III before and after cyclopentolate (Colircuss), tropicamide (Mydrax 0.5%), and artificial tears (Tearlose) drop instillation. RESULTS: After instilling cyclopentolate drops, the mean of the total root mean square (RMS) increased from 4.580 to 6.335 D, total spherical aberration increased from 0.155 to 0.381 D, and total coma increased from 0.195 to 0.369 D; the increases were significant for total RMS and total spherical aberration, but a significant relationship was not seen with total coma. After tropicamide, the mean aberrations of total RMS increased from 4.301 to 4.568 D, total spherical aberration increased from 0.146 to 0.160 D, and total coma increased from 0.213 to 0.230 D; the increase was only significant for total coma. On the other hand, after artificial tears, the average of all aberrations decreased in a nonsignificant manner. CONCLUSION: Most changes of mean aberrations were related to cyclopentolate drops. Tropicamide and artificial tears had the second and third rank according to their effect on mean errors. As a result, it seems that ocular accommodation is the most important impact on HOA than pupil size. However, the pupil size is the second factor for HOAs.

Anterior chamber perfusion versus posterior chamber perfusion does not influence measurement of aqueous outflow facility in living mice by constant flow infusion.

Mice are now routinely utilized in studies of aqueous humor outflow dynamics. In particular, conventional aqueous outflow facility (C) is routinely measured via perfusion of the aqueous chamber by a number of laboratories. However, in mouse eyes perfused ex-vivo, values for C are variable depending upon whether the perfusate is introduced into the posterior chamber (PC) versus the anterior chamber (AC). Perfusion via the AC leads to posterior bowing of the iris, and traction on the iris root/scleral spur, which may increase C. Perfusion via the PC does not yield this effect. But the equivalent situation in living mice has not been investigated. We sought to determine whether AC versus PC perfusion of the living mouse eye may lead to different values for C. All experiments were conducted in C57BL/6J mice (all ♀) between the ages of 20 and 30 weeks. Mice were divided into groups of 3-4 animals each. In all groups, both eyes were perfused. C was measured in groups 1 and 2 by constant flow infusion (from a 50 µL microsyringe) via needle placement in the AC, and in the PC, respectively. To investigate the effect of ciliary muscle (CM) tone on C, groups 3 and 4 were perfused live via the AC or PC with tropicamide (muscarinic receptor antagonist) added to the perfusate at a concentration of 100 µM. To investigate immediate effect of euthanasia, groups 5 and 6 were perfused 15-30 min after death via the AC or PC. To investigate the effect of CM tone on C immediately following euthanasia, groups 7 and 8 were perfused 15-30 min after death via the AC or PC with tropicamide added to the perfusate at a concentration of 100 µM. C in Groups 1 (AC perfusion) and 2 (PC perfusion) was computed to be 19.5 ± 0.8 versus 21.0 ± 2.1 nL/min/mmHg, respectively (mean ± SEM, p > 0.4, not significantly different). In live animals in which tropicamide was present in the perfusate, C in Group 3 (AC perfusion) was significantly greater than C in Group 4 (PC perfusion) (22.0 ± 4.0 versus 14.0 ± 2.0 nL/min/mmHg, respectively, p = 0.0021). In animals immediately following death, C in groups 5 (AC perfusion) and 6 (PC perfusion) was computed to be 21.2 ± 2.0 versus 22.8 ± 1.4 nL/min/mmHg, respectively (mean ± SEM, p = 0.1196, not significantly different). In dead animals in which tropicamide was present in the perfusate, C in group 7 (AC perfusion) was greater than C in group 8 (PC perfusion) (20.6 ± 1.4 versus 14.2 ± 2.6 nL/min/mmHg, respectively, p < 0.0001). C in eyes in situ in living mice or euthanized animals within 15-30 min post mortem is not significantly different when measured via AC perfusion or PC perfusion. In eyes of live or freshly euthanized mice, C is greater when measured via AC versus PC perfusion when tropicamide (a mydriatic and cycloplegic agent) is present in the perfusate.

Mydriatics release from solid and semi-solid ophthalmic formulations using different in vitro methods.

The aim of the present paper was the development of semi-solid (hydrogels) and solid (film) ophthalmic formulations for the controlled release of two mydriatics: phenylephrine and tropicamide. The formulations - based on polyvinylalcohol and hyaluronic acid - were characterized, and release studies were performed with three different in vitro set-ups, i.e. Franz-type diffusion cell, vial method and inclined plane; for comparison, a solution and a commercial insert, both clinically used to induce mydriasis, were evaluated. Both gels and film allowed for a controlled release of drugs, appearing a useful alternative for mydriatics administration. However, the release kinetic was significantly influenced by the method used, highlighting the need for optimization and standardization of in vitro models for the evaluation of drug release from ophthalmic dosage forms.

Interaction with therapeutic soft contact lenses affects the intraocular efficacy of tropicamide and latanoprost in dogs.

Therapeutic soft contact lenses (TSCLs) are frequently used to support or protect the cornea during healing. Our aim was to quantitatively evaluate the efficacy of topical medications in TSCL-fitted dogs and determine whether it is affected by the presence of TSCLs. In Phase I, pupil diameter was measured in eyes treated with tropicamide and in eyes covered with TSCLs and then treated with tropicamide, with 1-week intervals between sessions. In Phase II, intraocular pressure (IOP) was measured in uncovered and TSCL-covered eyes treated with latanoprost, with 1-week intervals between sessions. Tropicamide caused significant mydriasis in both uncovered and TSCL-covered eyes (P = 0.005). On the other hand, latanoprost caused a significant decrease in IOP when applied to uncovered eyes (P = 0.002), but had no significant effect on IOP when applied to TSCL-covered eyes (P = 0.7). As we used the same dogs and identical TSCLs throughout the study, we conclude that the different outcomes of the two drugs are due to properties of the drugs themselves, or their formulations, affecting their interaction with the TSCLs. The clinical efficacy of topical drugs applied to TSCL-covered eyes may have to be determined for each drug and/or formulation.

Effect of mydriasis induced by topical 0.5% tropicamide instillation on the corneal biomechanical properties in healthy individuals measured by ocular response analyzer.

PURPOSE: This observational study aims to investigate the effects of tropicamide (0.5%) on corneal biomechanical properties, with the ocular response analyzer (ORA), in healthy individuals. METHODS: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc) measurements of 38 (21 female and 17 male) healthy individuals, before and after 30 min of 0.5% tropicamide instillation, were performed by using the ORA. RESULTS: The mean CH, CRF, IOPg and IOPcc measurements of the eyes were 10.2 ± 1.9 mmHg, 10.3 ± 2.1 mmHg, 15.7 ± 3.4 mmHg, 16.4 ± 3.3 mmHg pre-tropicamide, and 10.4 ± 1.7 mmHg, 10.3 ± 2.1 mmHg, 15.3 ± 3.4 mmHg, 15.8 ± 2.7 mmHg post-tropicamide, respectively. The differences between the pre- and post-tropicamide measurements of the eyes were insignificant (p = 0.184, p = 0.659, p = 0.294, p = 0.150, respectively; paired t-test). CONCLUSIONS: A tropicamide instillation does not lead to significant changes in the corneal biomechanical properties. Therefore, it can be used safely in disease, i.e. in the diagnosis and follow-up ORA as it does not cause any change.

The change in intraocular pressure after pupillary dilation in eyes with pseudoexfoliation glaucoma, primary open angle glaucoma, and eyes of normal subjects.

To evaluate the change in intraocular pressure (IOP) after pharmacologic dilation in eyes with primary open angle glaucoma (POAG), pseudoexfoliation glaucoma (PXG), and eyes of normal subjects. This cross-sectional study was conducted in a university hospital-based setting. Patients with PXG, POAG, and normal subjects were consecutively selected and included in the study. Of the 125 eyes of 125 subjects; 46 (25 female) had PXG, 42 (29 female) had POAG, and 37 (20 female) belonged to the control group. Pharmacologic dilation procedure consisted of instillation of topical phenylephrine HCL 10 % followed 5 min by tropicamide 1 %. Studied variables were pre- and post-dilation IOP and also baseline measurements of anterior chamber angle, central corneal thickness, and pupillary diameter by Pentacam HR (Oculus, Wetzlar, Germany). Clinically significant IOP change was defined as a change of ≥2 mmHg from baseline. Randomly selected single eye of each patient was included in the analysis. The mean pre:post-dilation IOP of eyes with PXG and POAG was 17.39 ± 3.89:17.54 ± 3.98 and 15.92 ± 2.37:16.07 ± 2.89 mmHg, respectively. The difference between the pre- and post-dilation IOP of eyes with PXG and POAG was not statistically significant. The eyes of control subjects, however, had a statistically significant reduction of IOP from 14.24 ± 2.88 to 13.54 ± 2.94 mmHg (P = 0.005). 28.3 % (13/46) of eyes with PXG, 16.7 % (7/42) of eyes with POAG, and 2.7 % (1/37) of control eyes showed a clinically significant IOP elevation from baseline after the dilation. In this study, glaucoma patients proportionally experienced a higher rate of clinically significant IOP elevation after pupillary dilation, when compared to normal subjects.

The effect of 1% tropicamide-induced mydriasis and cycloplegia on spherical refraction of the adult horse.

OBJECTIVES: To determine the effects of tropicamide 1% on the refractive state of the adult equine globe and identify the most appropriate time period (in relation to mydriasis) to perform streak retinoscopy. ANIMALS STUDIED: Eight university-owned mares of various ages and breeds. PROCEDURES: Topical tropicamide 1% was applied to one randomly selected eye from each of the horses to induce mydriasis and cycloplegia. The contralateral eyes served as controls. Streak retinoscopy and pupillometry were performed prior to, and every 5 min after tropicamide 1% installation for 90 min. RESULTS: All values are expressed as mean ± SD. Both horizontal (2.8 ± 0.74 mm) and vertical (7.3 ± 1.29 mm) mean pupil diameters increased significantly (P < 0.04) in the treatment eyes compared with the control eyes (horizontal [0.48 ± 0.85 mm] and vertical [1.06 ± 1.31 mm] pupil diameter). No significant differences in the refractive states of the treatment (horizontal: +0.25 ± 0.43 D and vertical: +0.41 ± 0.37 D) or control (horizontal: +0.34 ± 0.39 D and vertical: +0.41 ± 0.37 D) eyes were identified at any time point. Three of the eight treatment eyes demonstrated blurry or reversing streak reflexes during streak retinoscopy evaluation following the application of topical tropicamide 1%. CONCLUSIONS: While these reflexes did not significantly influence streak retinoscopy results, their presence may subjectively influence a novice retinoscopist's ability to obtain accurate results. Therefore, optimal streak retinoscopy results may be obtained prior to, or 40- to 45-min following the application of topical tropicamide 1%, once near-maximal dilation has been achieved.

Effect of selective blockade of M4 cholinoreceptors by tropicamide on blood supply in brain, splanchnic azygous organs, and hindlimbs in intact rats.

Experiments on anesthetized rats carried out with a high-frequency ultrasonic system and tropicamide, a highly selective blocker of M4 cholinoreceptors, showed that the vasodilator effects observed after selective blockade of M4 cholinoreceptors are not organ-specific. Intravenous tropicamide (0.1 µg/kg body weight) transiently decreased systemic BP, elevated the linear and volume fl ow rates, and diminished vascular resistance in common carotid, superior mesenteric, and femoral arteries. At the same time, in most rats (76%) the fl ow rate in the portal vein did not change, while in 25% rats it insignificantly and temporarily increased. The hypothesis on possible involvement of M4 cholinoreceptor structures in cholinergic vasoconstriction is discussed.

The Short-Term Effect of 1% Tropicamide Drop on Pupillary Diameter and Intraocular Pressure Change in Patients With Pseudoexfoliation Material.

PRCIS: In this study, in patients with pseudoexfoliation syndrome (PXS) or glaucoma, changes in intraocular pressure (IOP) and pupil size after 1% tropicamide used for pupil dilation, compared with healthy patients were quantitatively demonstrated up to 4 hours after dilation. PURPOSE: The purpose of this study was to evaluate pharmacological dilatation with one drop of 1% tropicamide on pupillary diameter and IOP changes in patients with PXS and glaucoma (PXG). MATERIALS AND METHODS: Eighty-two patients with PXS, 78 Patients with PXG, and 35 healthy subjects were included in the study. PXG and PXS were diagnosed based on IOP assessment, corneal pachymetry, optic disc examination, visual field testing, and peripapillary retinal nerve fiber analysis. IOP and the diameter of pupil size were measured before dilatation and at postdilatation first, second, and fourth hours. RESULTS: The mean pupillary diameter values at postdilatation second and fourth hours were statistically significantly different between the patients with PXS and PXG ( P <0.001, for each). Also, there were significant differences between the PXS group and the control group in terms of the mean pupillary diameter values at predilatation and postdilatation at the first hour and postdilatation second hour ( P =0.007, <0.001, respectively). The mean pupillary diameter at all times was statistically significantly different between PXG and control groups ( P <0.001 for each). Significant IOP increases were observed in all groups after dilatation. The mean IOP at predilatation and postdilatation fourth hour was statistically significantly different between PXG and PXS groups ( P =0.042, <0.001, respectively). Whereas the mean IOP at predilatation, postdilatation first hour, postdilatation second hour, and postdilatation fourth hour were statistically significantly different between PXG and control group ( P <0.001 for each). CONCLUSIONS: Significant IOP increases have been observed in our study with 1% tropicamide in the PXG and PXS groups, with the peak effect at the second hour in the postdilatation period. Furthermore, the mean pupil diameter was found to be significantly lower in PXG patients compared with the control group.

Tropicamide Versus Cyclopentolate for Cycloplegic Refraction in Pediatric Patients With Brown Irides: A Randomized Clinical Trial.

PURPOSE: To compare the final cycloplegic refraction of tropicamide 1% and cyclopentolate 1% in children 3-16 years of age with brown irides. DESIGN: Randomized, controlled, multicenter prospective clinical trial. METHODS: Included patients were randomized to either cyclopentolate 1% or tropicamide 1% in the first visit with autorefraction measurements. Each subject underwent a second cycloplegic refraction using the other agent on a separate visit with a minimum of 1-week interval and a maximum of 12 weeks. We measured the change in SE (ΔSE) for each eye by deducting the SE before cycloplegia from the SE after cycloplegia. RESULTS: A total of 185 eyes from 94 children aged 3-16 years (average= 8.79 ±3.11 years) were included. The average SE of both eyes before cycloplegia was -0.082 ± 4.8 diopters. The SE after instillation of cyclopentolate and tropicamide in both eyes was 1.07±5.2 and 0.96±5.1, respectively (P value < .001). The average ΔSE after cycloplegia was 1.15±1.2 for cyclopentolate and 1.04±1.2 for tropicamide (P value < .001). The difference between ΔSE of cyclopentolate and tropicamide was found statistically significant at 0.11±1.2 (P < .001), although clinically insignificant. The ΔSE between the 2 drops before and after cycloplegia in both eyes for all refractive error groups was clinically insignificant. The greatest effect of cyclopentolate and tropicamide was in hyperopic eyes with ΔSE of 1.54±1.4 and 1.39±1.4, respectively. CONCLUSIONS: Tropicamide might be an effective and safe replacement for cyclopentolate in the refracting nonstrabismic pediatric population 3-16 years of age regardless of their refractive error status.

The Ras-binding domain region of RGS14 regulates its functional interactions with heterotrimeric G proteins.

RGS14 is a 60 kDa protein that contains a regulator of G protein signaling (RGS) domain near its N-terminus, a central region containing a pair of tandem Ras-binding domains (RBD), and a GPSM (G protein signaling modulator) domain (a.k.a. Gi/o-Loco binding [GoLoco] motif) near its C-terminus. The RGS domain of RGS14 exhibits GTPase accelerating protein (GAP) activity toward Gαi/o proteins, while its GPSM domain acts as a guanine nucleotide dissociation inhibitor (GDI) on Gαi1 and Gαi3. In the current study, we investigate the contribution of different domains of RGS14 to its biochemical functions. Here we show that the full-length protein has a greater GTPase activating activity but a weaker inhibition of nucleotide dissociation relative to its isolated RGS and GPSM regions, respectively. Our data suggest that these differences may be attributable to an inter-domain interaction within RGS14 that promotes the activity of the RGS domain, but simultaneously inhibits the activity of the GPSM domain. The RBD region seems to play an essential role in this regulatory activity. Moreover, this region of RGS14 is also able to bind to members of the B/R4 subfamily of RGS proteins and enhance their effects on GPCR-activated Gi/o proteins. Overall, our results suggest a mechanism wherein the RBD region associates with the RGS domain region, producing an intramolecular interaction within RGS14 that enhances the GTPase activating function of its RGS domain while disfavoring the negative effect of its GPSM domain on nucleotide dissociation.