Influence of pupillary diameter, ciliary muscle tone, and ambient light on nerve fiber layer measurements with scanning laser polarimetry

PURPOSE

To evaluate the influence of the pupillary diameter, ciliary muscle tone, and room light on nerve fiber layer measurements with the scanning laser polarimeter (GDx).

METHODS

One randomly selected eye of ten normal volunteers was examined with the GDx in a two-day protocol under eight testing conditions (pilocarpine 1%, phenylephrine 10%, tropicamide 1%, or no drops with room lights on or off). The twelve parameters, obtained by the GDx, were compared under the eight testing conditions, using two way ANOVA for repeated measurements and Tukey HSD post hoc test.

RESULTS

Ten of the twelve parameters were statistically significantly different (P < 0.05) when measured under the three medication or no medication conditions, controlling for the ambient light status. There were no significant differences when measured with the light on or off, controlling for use of drops.

CONCLUSIONS

Nerve fiber layer measurements with the GDx were influenced by drugs affecting pupillary diameter, but not by the status of room light or ciliary muscle tone.

Quantifying effects of retinal illuminance on frequency doubling perimetry

PURPOSE

To measure and quantify effects of variation in retinal illuminance on frequency doubling technology (FDT) perimetry.

METHODS

A Zeiss-Humphrey/Welch Allyn FDT perimeter was used with the threshold N-30 strategy. Study 1, quantifying adaptation: 11 eyes of 11 subjects (24-46 years old) were tested with natural pupils, and then retested after stable pupillary dilation with neutral density filters of 0.0, 0.6, 1.2, and 1.6 log unit in front of the subject's eye. Study 2, predicting effect of reduced illuminance: 17 eyes of 17 subjects (26-61 years old) were tested with natural pupils, and then retested after stable pupillary miosis (assessed with an infrared camera). A quantitative adaptation model was fit to results of Study 1; the mean adaptation parameter was used to predict change in Study 2.

RESULTS

Study 1: Mean defect (MD) decreased by 10 dB over a 1.6 log unit range of retinal illuminances; model fits for all subjects had r2> 95%. Study 2: Change in MD (DeltaMD) ranged from -7.3 dB to +0.8 dB. The mean adaptation parameter from Study 1 accounted for 69% of the variance in DeltaMD (P <0.0005), and accuracy of the model was independent of the magnitude of DeltaMD (r2< 1%, P >0.75).

CONCLUSIONS

The results confirmed previous findings that FDT perimetry can be dramatically affected by variations in retinal illuminance. Application of a quantitative adaptation model provided guidelines for estimating effects of pupil diameter and lens density on FDT perimetry.

Accommodation measurements in a prepresbyopic and presbyopic population

PURPOSE

To study the efficacy of several subjective and objective methods of accommodation measurement in normal prepresbyopic and presbyopic populations to identify appropriate methods for measuring the outcome of accommodative restorative procedures.

SETTING

University of Houston, College of Optometry, Houston, Texas, USA.

METHODS

Thirty-one normal subjects with a mean age of 43.7 years (range 31 to 53 years) participated. Accommodation was measured monocularly using 3 subjective approaches--the push-up test, minus lenses to blur, and a focometer--and 2 approaches measured with a Hartinger coincidence refractometer, in which accommodation was stimulated with minus lenses to blur and topical pilocarpine 6%.

RESULTS

The push-up method overestimated accommodative amplitude relative to objective measures in 28 subjects. Two subjective methods, minus lenses to blur and the focometer, produced comparable results, but with lower amplitudes in younger subjects and higher amplitudes in older subjects compared with objective methods. Comparable results were obtained when accommodation was stimulated in 1 of 2 ways and measured with the Hartinger. Pilocarpine elicited stronger accommodative responses than distance blur for subjects with low accommodative amplitudes. Pilocarpine 6% produced stronger responses in subjects with light irides than in those with dark irides.

CONCLUSIONS

Hartinger-measured accommodation provides more realistic measurement of accommodative amplitude than the subjective methods tested, especially in the presbyopic population. In presbyopic subjects, the subjective tests resulted in accommodative amplitudes up to 4.0 diopters greater than those measured with objective tests. Measurements of accommodative amplitude are best achieved with objective methods to stimulate and measure accommodation.

Micellar solutions of triblock copolymer surfactants with pilocarpine

Solutions of surface active triblock copolymer Pluronic F127 in the vicinity of the critical micellar concentration (cmc) were prepared with or without pilocarpine (either as the hydrochloride salt or the free base) in water and phosphate buffer. The characteristics parameters of the surface activity (cmc, Gamma and a) were determined for F127 solutions. Additionally, it was found that the pilocarpine solutions without F127 in water exhibits a certain surface activity. The solutions containing F127 (2 wt.%) well above the cmc and pilocarpine (2 wt.% for the salt, or equimolar 1.7 wt.% for the base) were further tested in vivo (miotic response) on rabbit eye. Though the entrapment efficiency of the drug in the micelles was rather low (maximal 1.9%) the pharmacokinetic parameters (duration of miotic response and the area under miotic curve) were improved when compared to the standard pilocarpine solutions. The best results were obtained for the micellar pilocarpine base solution which exhibits significant prolongation of miotic activity and an increase of AUC for 64%.

Effect of intracameral injection of lidocaine and carbachol on the rabbit corneal endothelium

PURPOSE

To determine the effect of intracameral injection of preservative-free lidocaine 1% and carbachol 0.01% on corneal endothelial cells of rabbits.

SETTING

Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.

METHODS

Forty eyes of 20 New Zealand White rabbits were divided into 2 equal groups. In the first group, 1 eye was injected with 0.02 mL of preservative-free lidocaine 1% and the fellow eye was injected with 0.02 mL of normal saline as a control. In the second group, 1 eye was injected with 0.02 mL of carbachol 0.01% and the fellow eye was injected with 0.02 mL of normal saline. Specular microscopy was used to evaluate corneal endothelial cell loss and corneal thickness 1 week and 1 month postinjection. For morphologic studies, corneal buttons were excised and stained with alizarin red with trypan blue. Scanning electron microscopy (SEM) examination was performed.

RESULTS

Specular microscopy revealed no significant endothelial cell loss and normal endothelial thickness with the intracameral injection of preservative-free lidocaine 1% and carbachol 0.01% compared with the control eye. Alizarin red with trypan blue stain and SEM examinations revealed smooth, distinct, and intact intercellular borders and normal viability of corneal endothelial cells in both groups.

CONCLUSIONS

Intracameral injections of preservative-free lidocaine 1% and carbachol 0.01% do not produce morphologic and functional changes in the corneal endothelial cells of rabbits.

Role of calcitonin gene-related peptide in the phenol-induced neurogenic hypertension in rats

Previous investigations have demonstrated that capsaicin-sensitive sensory nerves are involved in the development of hypertension in some rat models of hypertension. To determine the role played by calcitonin gene-related peptide (CGRP; the predominant neurotransmitter in capsaicin-sensitive sensory nerves) in a rat model of neurogenic hypertension, in which hypertension was induced by injecting 50 microl of 10% phenol in the lower pole of the left kidney, systolic blood pressure (SBP) was monitored by the tail-cuff method throughout the experiment. Fifteen days after injection of phenol, mean arterial pressure (MAP), concentrations of CGRP in the plasma, the expression of CGRP mRNA in dorsal root ganglia (DRG) and CGRP content in laminae I and II of the spinal cord were measured. SBP was significantly increased 5 days after the intrarenal injection of phenol (164+/-7 mm Hg, p<0.01). At the end of experiment, blood pressure (BP) was significantly elevated in the phenol-injected rats compared with the controls (SBP: 187+/-6 vs. 122+/-4 mm Hg, p<0.01; MAP: 157.56+/-3.02 vs. 103.80+/-2.04 mm Hg, p<0.01). Treatment with capsaicin, which selectively depletes neurotransmitters from the capsaicin-sensitive nerves, failed to enhance the development of hypertensive responses to the intrarenal injection of phenol. Intravenous administration of CGRP(8-37), the specific CGRP receptor antagonist, also failed to increase the already elevated MAP. The expression of CGRP mRNA (both alpha- and beta-CGRP isoforms), the content of CGRP in laminae I and II of the dorsal horn of the spinal cord and the concentration of CGRP in the plasma was decreased in the rats treated with phenol. These results suggest that CGRP does not play a counterregulatory role in the phenol-induced hypertensive rats, and support the hypothesis that reduction of CGRP (alpha and beta isoforms) could contribute to a blood pressure elevation in this setting.

Changes in the shape of the anterior and posterior corneal surfaces caused by mydriasis and miosis

PURPOSE

To evaluate changes in the anterior and posterior corneal shape, corneal thickness, and anterior chamber depth (ACD) caused by mydriasis or miosis using scanning-slit corneal topography.

SETTING

Department of Ophthalmology, Iwate Medical University School of Medicine, Iwate, Morioka, Japan.

METHODS

Twenty-eight eyes of 28 healthy volunteers with refractive errors of -6.00 to +0.25 diopters were studied. One eye of each subject had instillation of tropicamide-phenylephrine hydrochloride (Mydrin P) to obtain mydriasis and of pilocarpine hydrochloride 2% (Sanpilo) to obtain miosis. To assess the corneal shape, the best-fit sphere (BFS), axial power, and tangential power were measured for the anterior and posterior corneal surfaces before and after mydriasis and before and after miosis using scanning-slit corneal topography (Orbscan version 3.0, Orbtek, Inc.). The pupil size, corneal thickness, and ACD were also examined before and after mydriasis and before and after miosis.

RESULTS

The mean age of the patients was 31.1 years +/- 5.6 (SD) (range 20 to 46 years). The anterior BFS changed from a mean of 8.04 +/- 0.3 mm at the time of mydriasis to a mean of 8.00 +/- 0.3 mm at the time of miosis. The posterior BFS changed from 6.53 +/- 0.3 mm to 6.46 +/- 0.3 mm, respectively. Thus, the anterior and posterior cornea became significantly steeper after miosis (P<.01). The ACD was significantly more shallow after miosis than after mydriasis. However, there was no significant difference in corneal thickness after mydriasis or miosis.

CONCLUSIONS

The anterior and posterior corneal shapes changed as a result of mydriasis and miosis, and the refractive power of the cornea significantly increased after miosis. To date, changes in refractive power from changes in pupil size have been attributed to a change in the refractive power of the crystalline lens; however, it is now thought that changes in corneal refractive power also occur.

Calcitonin gene-related peptide and substance P induce pronounced motor effects in the female rat urethra in vivo

OBJECTIVE

This study was performed to investigate the influence of calcitonin gene-related peptide (CGRP) and substance P (SP) on the intra-urethral pressure in female rats, as both these neuropeptides have been demonstrated to occur in nerve fibres throughout all layers of the intrinsic external urethral sphincter of the rat.

MATERIAL AND METHODS

Both CGRP and SP were administered intra-arterially relatively close to the bladder in ketamine-anaesthetized female rats. The maximum urethral pressure (MUP) was recorded continuously using a 4 F microtip single-transducer catheter.

RESULTS

Pronounced effects on the intra-urethral pressure were found with both CGRP and SP. CGRP at the maximum dose given (10 micrograms) induced an immediate, pronounced, long-lasting decrease in pressure from 28 +/- 4 to 10 +/- 2 cmH(2)O, amounting to 65% of the MUP. SP (10 micrograms) instead induced a forceful, phasic, peak-like contractile response with a 170% increase in urethral pressure from 33 +/- 6 to 87 +/- 6 cmH(2)O of the initial control level of MUP. Antagonists to CGRP and SP did not induce any pressure changes per se.

CONCLUSION

These results indicate that both CGRP and SP are of importance for the peripheral motor regulation of the external urethral sphincter, and hence possibly also of physiological importance for lower urinary tract function during essential parts of the micturition cycle.

Effect of accommodation and pupil size on the movement of a posterior chamber lens in the phakic eye

PURPOSE

Although a posterior chamber phakic intraocular lens provides effective refractive correction of high myopia and hyperopia, mechanical contact between the implantable contact lens (ICL) and the crystalline lens and inadequate aqueous circulation in the prelenticular space could cause subcapsular opacification. To assess whether and to what extent such mechanical contact occurs, changes in the distance between the STAAR Collamer ICL and the crystalline lens under various conditions were investigated.

DESIGN

Open pilot study.

PARTICIPANTS

Thirteen eyes of 11 myopic and 2 hyperopic patients with a mean age of 38 years (range, 19-53 years) were examined at least 6 months after ICL implantation.

METHODS

A noninvasive, high-resolution biometry technique, partial coherence interferometry, was used to measure distance changes between the ICL and the crystalline lens during subjective accommodation, after instillation of pilocarpine, and under changing light conditions.

MAIN OUTCOME MEASURES

Mean distance changes from the posterior corneal surface to the ICL, from the posterior corneal surface to the anterior surface of the crystalline lens, and the distance between the ICL and the crystalline lens.

RESULTS

In the nonaccommodated state, the mean distance between the ICL and the crystalline lens was 457 microm (range, 123-924 microm). During subjective accommodation, a significant (P<0.01) decrease and, after topical application of pilocarpine, a nonsignificant (P=0.35) decrease of anterior chamber depth was accompanied by a nonsignificant (P = 0.71) reduction of the ICL-crystalline lens distance. Under photopic conditions, a significant mean reduction (P<0.01) of the ICL-crystalline lens distance of -28 microm (range, -16 to -188 microm) was observed.

CONCLUSIONS

Partial coherence interferometry biometry enabled noninvasive high-precision investigation of ICL dynamics. No significant changes between the ICL and the crystalline lens were detected during subjective accommodation and after application of pilocarpine. However, under photopic conditions, with constriction of the pupil, the distance between the ICL and the crystalline lens was significantly reduced. This mechanism might cause inadequate aqueous circulation in the prelenticular space and might be one of the causes of subcapsular opacification in some of the eyes after ICL implantation.

Oral pilocarpine for the treatment of ocular symptoms in patients with Sjögren's syndrome: a randomised 12 week controlled study

OBJECTIVE

To evaluate the efficacy and side effects of oral pilocarpine for the treatment of ocular symptoms in patients with primary Sjögren's syndrome (SS).

METHODS

A 12 week, single centre, randomised controlled study was performed. Twenty nine patients were randomly assigned to receive oral pilocarpine (5 mg twice a day), 28 only artificial tears, and 28 inferior puncta occlusion. Patients receiving oral pilocarpine and those with inferior puncta occlusion also received artificial tears. Patients were evaluated at baseline and throughout the study for their subjective global assessment of dry eyes and for their objective assessment of dry eyes (Schirmer's-I test, rose bengal test, and imprint test).

RESULTS

Patients taking oral pilocarpine had significant improvement in subjective global assessment of dry eyes, as was evaluated by improvement of >55 mm on a visual analogue scale (VAS) for responses to the eye questionnaire, compared with patients treated with artificial tears (p<0.001) and those with inferior puncta occlusion (p<0.05). Furthermore, patients receiving oral pilocarpine also showed greater objective improvement, as measured by the rose bengal test (p<0.05), while Schirmer's-I test showed no differences between the treated groups. Commonly reported adverse events were headache, increased sweating, nausea, and vomiting in the pilocarpine group, while one patient in the inferior puncta occlusion group had blepharitis and was withdrawn from the study.

CONCLUSION

10 mg of pilocarpine daily given to patients with SS for 12 weeks had a beneficial effect on subjective eye symptoms, as evaluated by improvement >55 mm on a VAS. Additionally, an improvement of rose bengal staining was noted, but an increase in tear production, as measured by the Schirmer-I test, was not substantiated.

Subjective and objective measurement of human accommodative amplitude

PURPOSE

To assess objective and subjective methods to measure accommodation in a young human population.

SETTING

Research laboratory, University of Houston, College of Optometry, Houston, Texas, USA.

METHODS

Accommodation was measured in the right eye of 15 young subjects (9 women and 6 men) whose ages ranged from 23 to 28 years and 1 36-year-old subject. The mean age of all subjects was 26 years. Accommodation was stimulated and measured with 4 techniques. Two subjective measures (focometer and minus-lens procedures) were used. Accommodation was also stimulated with minus-lens-induced blur and with pilocarpine 6% and measured objectively with a Hartinger coincidence refractometer.

RESULTS

Accommodative amplitudes measured with the 2 subjective methods agreed with each other but differed from the objectively measured amplitudes. Objectively measured accommodative amplitudes were similar in all subjects, with a mean of about 7.0 diopters. Accommodation stimulated with pilocarpine reached a maximum 33 minutes after administration. Individuals with light irides showed a stronger accommodative response to pilocarpine than subjects with dark irides.

CONCLUSIONS

Subjective measures of accommodation tend to overestimate true accommodative amplitude. Methods exist to measure accommodation objectively. These include stimulating accommodation with trial lenses or pilocarpine 6% and measuring the accommodative response with an objective optometer such as a Hartinger coincidence refractometer. Objective measures of accommodation should be used to determine whether accommodation can be restored in presbyopes.

Theoretical and Measured Pseudophakic Accommodation After Implantation of a New Accommodative Posterior Chamber Intraocular Lens

OBJECTIVE

To analyze different techniques of measuring accommodation after implantation of a new accommodative posterior chamber intraocular lens (PCIOL).

METHODS

In this comparative, nonrandomized interventional study, we analyzed 15 eyes of 15 patients (aged 44-84 years) at 6 months after cataract surgery and PCIOL implantation (Akkommodative 1CU; HumanOptics AG, Erlangen, Germany) and compared these results with those of an age-matched control group (n = 15). We used the following methods to measure accommodation: dynamic measurement with objective (videorefractometry [PowerRefractor; PlusOptix, Erlangen] and streak retinoscopy) and subjective (subjective near point [push-up test and accommodometer] and defocusing) techniques, as well as static measurement of the change in anterior chamber depth (ACD) using the IOLMaster (Zeiss, Jena, Germany) after pharmacological stimulation using 2% pilocarpine eye drops.

MAIN OUTCOME MEASURES

Theoretical accommodation calculated from the forward shift of the lens optics (decrease of ACD) using paraxial geometrical optics and measured accommodation amplitude.

RESULTS

Accommodation amplitude (mean +/- SD; range; median) results after 6 months in the study and control groups were as follows: 1.00 +/- 0.44; 0.75-2.13; 1 diopter (D); and 0.35 +/- 0.26; 0.10-0.65; 0.25 D, respectively, using the PowerRefractor; 0.99 +/- 0.48; 0.13-2.00; 0.88 D; and 0.24 +/- 0.21; -0.13-0.75; 0.25 D, respectively, using retinoscopy; 1.6 +/- 0.55; 0.50-2.56; 1.7 D; and 0.42 +/- 0.25; 0.00-0.75; 0.50 D, respectively, using subjective near point; and 1.46 +/- 0.53; 1.00-2.50; 1.75 D; and 0.55 +/- 0.33; 0.25-0.87; 0.50 D, respectively, using defocusing. Anterior chamber depth decreased in the study and control groups as follows: 0.78 +/- 0.12; 0.49-1.91; 0.65 mm; and 0.16 +/- 0.09; 0.00-0.34; 0.18 mm, respectively, after applying 2% pilocarpine eyedrops, indicating an accommodation of 1.16 +/- 0.22; 0.72-1.88; 1.05 D vs 0.22 +/- 0.13; 0.00-0.47; 0.23 D (P =.001).

CONCLUSIONS

Accommodation after implantation of a presumably accommodative PCIOL can be measured with clinical methods or derived from the biometric data of the eye and the measured ACD decrease using geometrical optics. For clinical purposes, pseudophakic accommodation should be assessed with a variety of different techniques, including subjective and objective measurements. The theoretical approach using geometrical optics may be an additional indicator for the accommodative response in patients with pseudophakic eyes and may allow a subdivision of the measured accommodation into true pseudophakic accommodation and pseudoaccommodation.

A study of replacement of timolol-pilocarpine with latanoprost in pseudoexfoliation glaucoma

The aim of the study was to evaluate the efficacy of replacing current dual local therapy (timolol and pilocarpine) with latanoprost 0.005% in 71 pseudoexfoliation glaucoma patients with controlled intraocular pressure (IOP). 39 patients switched to latanoprost 0.005%) and 32 patients continued timolol-pilocarpine therapy. Mean diurnal (IOP) was measured at baseline, after 0.5, 1, 3 and 6 months of treatment. After 6 months 38 patients with latanoprost and 30 patients with timolol-pilocarpine had completed the study. At baseline the mean diurnal IOP was 20.4 +/- 2.0 mmHg for patients in latanoprost treatment group and 21.4 +/- 2.1 mmHg for patients in timolol-pilocarpine group. At the end of the study, after 6 months of treatment, the mean diurnal IOP values were 16.6 +/- 2.4 and 17.9 +/- 2.0 mmHg respectively. IOP was statistically significantly reduced from baseline (p < 0.001). The mean diurnal IOP change from baseline was -3.3 +/- 0.5 mmHg (mean +/- SEM, ANCOVA) for the patients treated with latanoprost and -3.2 +/- 0.4 mmHg for the patients treated with timolol + pilocarpine. This difference in IOP reduction between groups was not statistically significant (z = 0.69; p = 0.49). This study showed that combination therapy (timolol plus pilocarpine) in pseudoexfoliation glaucoma can effectively be replaced by latanoprost monotherapy.

An electrophoretic method to deliver topical drugs to the eye

It is possible that many patients avoid complete ophthalmic exams because pupil dilation is slow, reversal sluggish, and vision blurred. Others experience incomplete dilation during exams or prior to surgery when good dilation is essential to successful outcome. Iontophoresis, the application of low-level electrical current to promote traversal of desired molecules across a boundary, has been used for many years and has recently become common in transdermal drug delivery. We now investigate iontophoresis as a method of accelerating drug absorption into the ocular anterior segment. In vivo rabbit studies assessed iontophoresis effects on the performance of dilators and constrictors. 1-mA and 4-mA direct current levels applied for 2-minute durations yielded dilation time-history measurements. Subsequent in vitro tests at a wide range of current densities showed minimal chemical modifications in ocular pharmaceuticals. Drug samples processed through high-performance liquid chromatography (HPLC) pinpointed minimal structural changes. Detailed in vivo rabbit testing is under way. Using 2 dilators and constrictors in crossed testing with 0.5-mA to 1.25-mA current levels and 20-sec to 60-sec durations, we recorded dilation progress by digital photography. Initial studies showed faster, larger dilations and quicker reversal using iontophoresis. Drug testing showed chemical structures remaining constant for clinically useful current levels, < or = 1 mA (< or = 1.25 mA/cm2 current density). Drug pH and HPLC retention times were constant within this range, and resistivity varied linearly as expected for increasing current. Rabbit testing will quantify improved drug speed and efficacy, validate the charge delivery electrode design, and indicate iontophoretic current and duration for further use. Tested ocular drugs showed no degradation when exposed to clinically useful iontophoretic currents. Preliminary results indicate significant time reductions for dilation and reversal, plus increases in maximum dilation. This procedure may aid clinicians by allowing more rapid complete examinations and surgical preparations for patients. Making dilation more convenient will also improve patient acceptance of exams, aiding earlier detection and treatment of ocular disease.

Effect of pupil size on multifocal pattern visual evoked potentials

The purpose of this study was to investigate the influence of pupil diameter on the amplitude and latency of multifocal visual evoked potentials (mfVEP). The multifocal objective perimeter (Accumap; Objectivision) was used to stimulate the visual field at 56 sites extending to 32 degrees using a pseudo-random pattern stimulus. The mfVEP were recorded using bipolar occipital electrodes, 7 min/eye. Ten normal subjects were recruited from the community and one eye was randomly selected for testing. The mfVEP were recorded at four different pupil diameters (2 mm, 4 mm, 6 mm, 8 mm), obtained by applying tropicamide (0.5%) or pilocarpine (2%) in different dilutions. Appropriate refractive correction was provided to overcome cycloplegia and achieve a visual acuity of 6/7.5 or better. Analysis revealed that at most pupil diameters the normalized full field amplitude did not show significant variation, except at the most miotic pupil diameter (2 mm), where the amplitude became reduced, based on 2-way anova and Tukey's T method. There was, however, significant correlation between latency and pupil area (correlation coefficient: upper field -0.63, lower field -0.76). The results suggest that even in the presence of mydriatics or miotics, the mfVEP test can be used to assess diseases that affect amplitude, provided near correction is used. The interpretation of latency, however, must be made with caution, as a borderline conduction defect with a dilated pupil may appear normal.

Influence of process parameters of high-pressure emulsification method on the properties of pilocarpine-loaded nanoparticles

Poly(lactide-co-glycolide) nanoparticles loaded with pilocarpine hydrochloride were prepared by the high-pressure emulsification-solvent evaporation method. The nanoparticles were produced using polyvinylalcohol (PVA), carbomer (Carbopol 980) or poloxamer (Lutrol F-68) as stabilizers during emulsification. The influence of pressure and number of cycles on the nanoparticle properties was investigated. For comparison, nanoparicles without high-pressure treatment of the emulsion were made. The nanoparticle size, drug loading and release properties depended strongly on the homogenization pressure and number of cycles applied. Nanoparticles obtained without high pressure homogenization showed larger size and high values of polydispersity index, especially when carbopol and poloxamer were used as emulsifiers. Drug loading and encapsulation efficiency of all samples also decreased with pressure. The low drug loading could be due to two reasons. First, the high pressure promoted drug diffusion out of protoparticles during emulsification either by size reduction or shear forces. Secondly, the characteristics of the outer water phase of the emulsion also influenced the nanoparticle drug loading. This was proven by the different drug loadings measured when nanoparticles were made with PVA, carbopol or poloxamer at equal pressures applied. The main factor influencing the release properties of nanoparticles was the pressure used during emulsification. Faster drug release was observed from nanoparticles obtained after high-pressure emulsification compared to those prepared without homogenization of the emulsion.

Ultrasonographic biomicroscopy, Scheimpflug photography, and novel provocative tests in contralateral eyes of Chinese patients initially seen with acute angle closure

OBJECTIVES

To compare ocular biometry of the contralateral eyes of individuals seen with acute angle closure (AAC) with eyes of population-based control subjects, and to assess novel provocative tests to study the mechanism of AAC.

DESIGN

Prospective case-control study.

PARTICIPANTS

Chinese persons seen as incident cases of AAC and Chinese population-based controls.

METHODS

Slitlamp assessment, ultrasonographic biomicroscopy, Scheimpflug photography, and provocative testing were performed.

MAIN OUTCOME MEASURES

Ocular biometric parameters including anterior chamber depth, limbal anterior chamber depth, axial length, lens thickness, and radius of corneal curvature were obtained. Ultrasonographic biomicroscopy parameters that include the angle-opening distance at 500 micro m and the angle-recess area were noted. Scheimpflug photography produced a single measure of angle width.

RESULTS

Contralateral eyes of cases of AAC had shorter axial lengths, shallower anterior chamber depths, thicker lenses, and steeper radii of corneal curvature (P<.01). After adjusting for age and sex, cases had a mean adjusted axial length that was 1.2 mm shorter, an optical anterior chamber depth that was 0.63 mm shallower (24% shallower than controls), and lenses that were, on average, 0.35 mm thicker (P<.01). Furthermore, using multiple logistic regression to adjust for age and sex, patients with primary angle-closure glaucoma were 19 times as likely to have a shallower limbal anterior chamber depth (25%; 95% confidence interval, 8.3-45.2). Adjusting for age and sex, the mean angle-opening distance at 500 microm was 0.14 U less for cases, with a mean of 0.26 U in controls, making the angle-opening distance at 500 microm, on average, 54% less among cases. Scheimpflug photographs revealed an adjusted angle width of 21.6 degrees for controls and 15.1 degrees for cases (P<.05). Dynamic testing showed that the angle of control eyes tended to shallow less when going from light to dark and tended to open more when given 1 drop of pilocarpine hydrochloride.

CONCLUSIONS

Contralateral eyes of individuals having an AAC attack tend to be shorter and have more crowded anterior segments than those of healthy controls. These static measures of ocular biometry indicate why some individuals are predisposed to AAC. Dynamic measures of the response to luminance changes and pilocarpine therapy indicate that differential reactions to these stimuli are also associated with an AAC attack.

Changes in intraocular pressure and pupil size following intramuscular administration of hydromorphone hydrochloride and acepromazine in clinically normal dogs

OBJECTIVE

To investigate the effects of intramuscularly administered hydromorphone hydrochloride and acepromazine on intraocular pressure (IOP) and pupil size (PS).

ANIMALS STUDIED

Seventeen dogs free of clinically relevant ocular abnormalities.

PROCEDURE

Measurements of IOP and PS were obtained and the dogs were injected intramuscularly with hydromorphone (0.04-0.08 mg/kg) and acepromazine (0.04 mg/kg). Measurements of IOP and PS were repeated 10 min and 25 min later.

RESULTS

Though a decreasing trend in IOP values was demonstrated, no significant difference was noted in IOP from the initial examination to examination following intramuscular administration of hydromorphone and acepromazine. Significant miosis was present in 16 of 17 dogs at 10 min and 25 min following administration of hydromorphone and acepromazine.

CONCLUSION

Hydromorphone (0.04-0.08 mg/kg) and acepromazine (0.04 mg/kg) cause significant miosis in dogs at 10 and 25 min following intramuscular administration.

Pupillary response to four concentrations of pilocarpine in normal subjects: application to testing for Adie tonic pupil

PURPOSE

To determine the amount of pupillary constriction to four different concentrations of pilocarpine in normal human subjects and to determine if pupillary constriction correlates with bioavailability of the instilled concentrations. The amount of pupillary constriction to dilute pilocarpine is utilized as a diagnostic test for Adie tonic pupil as distinguished from a normal pupil response.

DESIGN

Twenty healthy volunteers had automated binocular infrared pupillography in the dark after instillation of four different concentrations of dilute pilocarpine. Ocular penetration of eye drops was also assessed using 2% fluorescein sodium as a tracer.

METHODS

Prospective institutional double-masked study of both eyes of twenty healthy volunteers, ten with brown irides, ten with blue irides, between the ages of 20-40 years.

RESULTS

A pilocarpine dose-dependent curve showed decreased pupil size within 15 minutes, peaking at 30-60 minutes. No difference was noted between right and left eyes, iris color, or corneal permeability.

CONCLUSIONS

Normal pupils constrict to dilute concentrations of pilocarpine (0.25% or 0.125%), but constrict insignificantly to concentrations of 0.0313% or 0.0625%. Pupil constriction with 0.0625% pilocarpine should distinguish an Adie pupil from normal. This confirms the utility of this simple office diagnostic procedure.

Efficacy and safety of immediate anterior chamber paracentesis in the treatment of acute primary angle-closure glaucoma: a pilot study

OBJECTIVE

To study the safety and effectiveness of immediate anterior chamber paracentesis, combined with antiglaucomatous medications, in the intraocular pressure control and relief of symptoms of acute primary angle-closure glaucoma (PACG).

DESIGN

Prospective noncomparative case series.

PARTICIPANTS

Eight consecutive patients with their first attack of acute PACG, with intraocular pressure > or =50 mmHg, were recruited into the study.

INTERVENTION

On presentation, each patient received topical pilocarpine (4%) and timolol (0.5%), immediate anterior chamber paracentesis, and systemic acetazolamide and mannitol as primary treatment. The intraocular pressures at 15 and 30 minutes, and then at 1, 2, 3, 12, and 24 hours, were documented by applanation tonometry.

MAIN OUTCOME MEASURES

Symptoms, visual acuity, intraocular pressure, corneal edema, angle status on gonioscopy, pupillary size, and reaction.

RESULTS

Ten eyes of eight patients seen with acute PACG were recruited. The mean intraocular pressure was reduced from 66.6 +/- 9.1 mmHg to 15.1 +/- 3.5 mmHg immediately after paracentesis, and then to 17.1 +/- 7.0 mmHg at 15 minutes, 21.7 +/- 10.2 mmHg at 30 minutes, 22.7 +/- 11.0 mmHg at 1 hour, and 20.1 +/- 14.6 mmHg at 2 hours after paracentesis. The mean intraocular pressure was less than 21 mmHg at 2 hours and beyond. There was instant symptomatic relief for all patients. No complications from the paracentesis were encountered.

CONCLUSIONS

From this preliminary study, immediate paracentesis seems to be safe and effective in controlling the intraocular pressure and eliminating symptoms in acute PACG.

In situ gelling xyloglucan formulations for sustained release ocular delivery of pilocarpine hydrochloride

Thermoreversible gels formed in situ by aqueous solutions of an enzyme-degraded xyloglucan polysaccharide were evaluated as sustained release vehicles for the ocular delivery of pilocarpine hydrochloride. In vitro release of pilocarpine from gels formed by warming xyloglucan sols (1.0, 1.5 and 2.0% w/w) to 34 degrees C followed root-time kinetics over a period of 6 h. The miotic responses in rabbit following administration of xyloglucan sols were compared with those from in situ gelling Pluronic F127 sols and from an aqueous buffer solution containing the same drug concentration. Sustained release of pilocarpine was observed with all gels, the duration of miotic response increasing with increase of xyloglucan concentration. The degree of enhancement of miotic response following sustained release of pilocarpine from the 1.5% w/w xyloglucan gel was similar to that from a 25% w/w Pluronic F127 gel.

[Pigment dispersion syndrome in a patient with megalocornea]

CASE REPORT

A case of a patient of 12 years old with megalocornea and bilateral pigment dispersion syndrome is reported. An ultrasound biomicroscopic study was performed with the UBM 840 (Zeiss-Humphrey, 50 MHz) and an iris concavity with an iridolenticular and iridozonular contact was observed. A new exam after pilocarpine instillation drops showed the resolution of the iris concavity, zonular and lenticular contact.

DISCUSSION

The anterior chamber configuration of this patient analyzed with ultrasound biomicroscopy allowed us to understand the mechanism of the pigment dispersion syndrome.