Axial length and pharmacologic pupillary dilation in highly myopic patients

PURPOSE

To determine how high myopia impacts pharmacological pupillary dilation, and to evaluate the relationship between the extent of pharmacologic pupillary dilation and axial length.

METHODS

Patients were grouped into high myopes, defined as one or both eyes having a refractive error greater than - 6 diopters, and controls (between - 2 and + 2 diopters). Dilation was achieved with 1 drop each of tropicamide 1% and phenylephrine 2.5%. Pupil size was measured at full and dim light prior to dilation, then 15 and 30 min after dilation. Biometry was measured for each patient. Statistical analyses were performed using the Mann-Whitney-Wilcoxon tests, two-sample Welch's t-tests, and linear mixed effect models and generalized estimating equations models accounting for inter-eye correlation.

RESULTS

Forty patients (20 high myopes and 20 controls, 80 eyes total) participated in the study. High myopes had larger pupils at baseline and achieved significantly greater pupillary size (7.08 mm, 95% CI: 6.97 to 7.19 mm) than controls (6.23 mm, 95% CI: 5.94 to 6.52 mm) after 30 min of dilation (P < .0005). Fully dilated pupil size at 30 min was significantly correlated with both refractive error (r =  - 0.57, P < .0005) and axial length (r = 0.47, P < .0005). Generalized estimating equations and linear mixed effect models identified other predictive variables of pupil size after dilation including age and white-to-white diameter.

CONCLUSIONS

Highly myopic patients dilate to a larger pupillary size compared to other patients. Predicting dilation based on extent of myopia could facilitate intraocular surgery planning and reduce clinic wait times for myopic patients.

Evaluation of a Pilot Protocol for Detecting Infant Hyperopia

SIGNIFICANCE

Highly hyperopic children are at greater risk for developing conditions such as strabismus, amblyopia, and early literacy and reading problems. High hyperopia is a common finding in infants in a pediatric medical practice, and early detection can be done effectively in that setting with tropicamide autorefraction.

PURPOSE

This study aimed to evaluate the effectiveness of a pilot screening program to detect high hyperopia in 2-month-old infants in a pediatric medical practice in Columbus, Ohio.

METHODS

Cycloplegic refractive error (1% tropicamide) was measured by retinoscopy and autorefraction with the Welch Allyn SureSight (Welch Allyn/Hillrom, Skaneateles Falls, NY) in 473 infants (55.4% female) who were undergoing their 2-month well-baby visit at their pediatrician's medical practice. Cycloplegic retinoscopy (1% cyclopentolate) was repeated at a subsequent visit in 35 infants with ≥+5.00 D hyperopia in the most hyperopic meridian during the screening.

RESULTS

Twenty-eight infants (5.9%) had high hyperopia (spherical equivalent, ≥+5.00 D), and 61 (12.9%) had high hyperopia (≥+5.00 D in at least one meridian of at least one eye) by retinoscopy with 1% tropicamide. The mean ± standard deviation spherical equivalent tropicamide cycloplegic refractive error measured with retinoscopy was +2.54 ± 1.54 D (range, -3.25 to +7.00 D) and with SureSight was +2.29 ± 1.64 D (range, -2.90 to +7.53 D). Retinoscopy done using 1% cyclopentolate was 0.44 ± 0.54 D more hyperopic in spherical equivalent than with 1% tropicamide ( P < .001).

CONCLUSIONS

High hyperopia was a common finding in 2-month-old infants in a pediatric medical setting that could be detected effectively by cycloplegic autorefraction using tropicamide. Greater cooperation between pediatric primary vision and medical care could lead to effective vision screenings designed to detect high hyperopia in infants.

[A prospective cohort study on refractive status of schoolchildren in Huangzhong District, Xining City, Qinghai Province]

Objective: To determine the characteristics and progress of the visual acuity and refractive state of schoolchildren in Huangzhong District, Xining City, Qinghai Province in China. Methods: Cohort study. Department of Ophthalmology, Beijing Children's Hospital carried out a cohort study by collecting the visual acuity and refractive state of Grade 1-5 schoolchildren among 16 primary schools in Huangzhong District, Xining City, Qinghai Province in September 2020 and July 2021. Cycloplegic retinoscopy with eye drop which contained tropicamide (0.5%) and phenylephrine hydrochloride (0.5%) was performed in children with low vision(<1.0). Myopia was defined as the spherical equivalent (SE) ≤-0.5 D after cycloplegic retinoscopy. Measurement data was analyzed by t-test and enumeration data was analyzed by χ² test. Multiple linear regression was used to analyze the influencing factors. Results: The 2 489 individuals with repeated tests in two years were included in the follow-up study, among whom the prevalence of myopia was 26.24%(653/2 489) in 2020, while 32.94% (820/2 489)respectively in 2021. The incidence of myopia in one school year from grades 1 to 5 was 11.19%(47/420), 5.44%(21/386), 6.39%(25/391), 11.52%(44/382) and 11.67%(30/257). The average SE of children in all grades in 2021 increased negatively from the previous year (Grade 1 to Grade 5 increased respectively: 0.40 D, 0.69 D, 0.62 D, 0.52 D and 0.37 D). Conclusions: The prevalence of myopia among schoolchildren in Huangzhong District, Xining City, Qinghai Province was relatively high. There were two peaks of myopia incidence in the first, fourth and fifth grades. Female, age, and the baseline of SE were the related influencing factors for myopia progression.

[Determining the time of intoxication due to non-drug use of tropicamide]

The study objective is to develop approaches to the retrospective assay of tropicamide in biological fluids and hair. The study was performed using the substance of tropicamide. Sample preparation included hydrolysis with the following enzymes: papain, chymotrypsin, trypsin, chymopsin, and hyaluronidase. Extracts were analyzed using a gas chromatograph with mass selective detection Technologies (USA) 7890 A/5977 MSD. When modeling long-term use of tropicamide, male rats of white and brown natural color, about 6 months old and weighing 200-250 g, were used. Animals were injected with a tropicamide solution in the tail vein for 28 days at a dose of 40 mg/kg of body weight. After 28 days of administration of the tropicamide solution, daily urine and blood were collected, and hair was cut from the back and sides of the animal's body. After another 28 days, hair samples were taken again. Within the first 6 hours after the last tropicamide dose, its blood concentration reached the maximum (191.6 μg/ml) and within 4 days decreased by 10 times; in the urine, within the first 24 hours, tropicamide level decreased from 627.7 to 489.9 μg/ml, then for 2-3 days it remained approximately at the same level. From day 4, the tropicamide concentration significantly decreased, and on days 11-12, it was not detected in the urine. After 4 weeks, the tropicamide content in the hair was at the level of quantification (1.25-2.20 ng/mg) and could be detected only by sample preparation by enzymatic hydrolysis with papain. Thus, the developed and validated methods for the enzymatic hydrolysis of biological fluids and hair allowed retrospective studies of biological fluids and hair with high reliability.

Quantifying the cost of single-use minims and multidose bottles for eye drops in routine ophthalmic practice: a multicentre study

OBJECTIVE

To compare costs between two different eye drop delivery modalities: multidose bottles and single-use minims.

DESIGN

Retrospective cohort study.

METHODS

Monthly dilating eye drop costs and quantities (tropicamide 1%, phenylephrine 2.5%, cyclopentolate 1%) were studied over a 2-year period between April 2013 and March 2015 at 2 tertiary ophthalmic centres (Royal Alexandra Hospital [RAH, Edmonton] and Rockyview General Hospital [RGH, Calgary]). In April 2014, RAH switched its dilating eye drop practice from predominantly multidose bottles to single-use minims, whereas RGH continued using predominantly multidose bottles. Eye drop volume and total and per-patient eye drop costs were quantified at RAH before switching (pre-intervention) and after (post-intervention) using an interrupted time-series analysis with RGH as a control. A counterfactual analysis was also performed. Significance was obtained using independent t-testing.

RESULTS

After switching to single-use minims, RAH experienced changes in the following: an increase in single-use minims as a proportion of total eye drop utilization (from 5.6% to 89.1%; p = 0.001), an increase in total eye drop cost by $2117 per month (95% confidence interval [CI], $1354-$2880; p < 0.001), an increase in per-patient costs by $984 per 1000 patients per month (95% CI, $674-$1293). Contrastingly, RGH did not experience similar changes. Ultimately, the cost of switching to single-use minims was $22 481 (95% CI, $7830-$31 336) over a 12-month period.

CONCLUSIONS

If safe eye drop practices are enforced via proper protocols, the use of multidose bottles may be a more cost-effective option than single-use minims for routine clinical practice.

Brightness perception changes related to pupil size

Dilating the pupils allow more quanta of light to impact the retina. Consequently, if one pupil is dilated with a pharmacological agent (Tropicamide), the brightness of a surface under observation should increase proportionally to the pupil dilation. Little is known about causal effects of changes in pupil size on perception of an object's brightness. In a psychophysical procedure of brightness adjustment and matching, we presented to one eye geometrical patterns with a central square (the reference pattern) that differed in physical brightness within backgrounds of constant luminance. Subsequently, with the other eye, participants (n = 30) adjusted to the same luminance a similar pattern (target) whose central square luminance was randomly set higher or lower in brightness than the reference. As only one eye was treated with Tropicamide, we assessed whether the subjective brightness of the target square shifted in a consistent direction when viewed with the dilated pupil compared to the untreated (control) eye. We found that, as the pupil increased post drug administration, so significantly did the sense of brightness of the pattern (i.e., higher brightness adjustments followed viewing the reference pattern with the treated (Tropicamide) eye). A reversed effect was observed when the control eye viewed the reference pattern first. The results confirm that even slight pupil dilations can result in an enhanced perceptual experience of brightness of the attended object, corresponding to an average increase of 2.09 cd/m² for each 1 mm increase in pupil diameter.

Alternative mydriasis techniques for retinopathy of prematurity screening

PURPOSE

There is a large variation in mydriatic regimens used in screening for retinopathy in preterm infants. Except for the standard instillation of mydriatic drops in their commercial formulation, other techniques for pupil dilation have also been described. This study aimed to review all techniques that have been used for mydriasis in retinopathy of prematurity eye examination (ROPEE) screening.

METHODS

A comprehensive literature search was performed in PubMed, Cochrane library, Trip database, and Scopus, using the key words: "mydriasis", "techniques", "mydriatics", "dilating drops", "retinopathy of prematurity", "ROP", "phenylephrine", "cyclopentolate", "tropicamide", "smaller mydriatic drops", "reduction in drop size" to February 2019.

RESULTS

Five primary studies were included, assessing the techniques of microdrops, lower conjunctival fornix (LCF) packing and Mydriasert® ophthalmic insert. Reported efficacy was similar to commercial eyedrops instillation. Microdrops appeared to have a superior safety profile. LCF packing and Mydriasert lead to increased blood pressure, without serious complications, necessitating further safety studies.

CONCLUSIONS

Of all alternative mydriasis techniques for ROPEE screening that have been described, microdrops appear to be the safest yet still effective technique in the fragile population of premature infants in risk of ROP.

Role of various subtypes of muscarinic cholinergic receptors in the development of posthemorrhagic abnormalities in systemic and portal circulation in rats

The experiments employing high-frequency ultrasonic technique and selective blockers of M1, M3, and M4 muscarinic cholinergic receptors pirenzepine, 4-DAMP, and tropicamide, respectively, revealed individual roles of these receptors in the development of severe posthemorrhagic hypotension in rats with low or high individual resistance to circulatory hypoxia. The study showed that M1 and M4 muscarinic receptors are involved in shock-limiting and shock-activating processes, respectively, while M3 receptors exert no effect on the course of posthemorrhagic abnormalities in systemic and hepatic portal circulation and on the posthemorrhagic lifespan. Poor resistance of the cardiovascular system to circulatory hypoxia during shock development is considered to be dysregulatory pathology.

[The pupillary response test as a method to differentiate various types of dementia]

AIM

Pupillometry is a non-invasive measurement technique based on the pupillary response to specific sensoric, mental and emotional variables. After topical application of a cholinergic antagonist (tropicamide) an increased pupillary dilatation response in Alzheimers s disease patients was described ("receptor test"). The aim of the present study was to evaluate the usefulness of the 0.01% tropicamide receptor test in differentiating types of dementia.

METHOD

425 patients (159 men, 266 women, mean age 75 years) of the Memory Clinic of the SMZ Ost Vienna, Austria were included in the study. 195 patients suffered from a dementia in Alzheimer's disease with late onset (ICD-10: F00.1), 42 from dementia in Alzheimer's disease with early onset (F00.0), 71 from vascular dementia (F01), 34 from Lewy-Body dementia (F03) and 83 from mixed dementia (F00.2). All patients were investigated by means of a computer-assisted pupillometer. The pupillary diameter of the left eye was measured 4 times (baseline=0 minutes, after 20, 40 and 60 minutes). 4 minutes after baseline one drop of 0.01% tropicamide solution was installed onto the left eye of the patients.

RESULTS

At baseline the pupillary diameter was largest in Lewy-Body dementia, smallest in vascular dementia. Significant differences were observed between vascular dementia and early-onset dementia in Alzheimer's disease as well as between Lewy-Body dementia and all other dementia syndromes (except dementia in Alzheimer's disease with early onset). The 0.01% tropicamide receptor test made it possible to differentiate early-onset dementia in Alzheimer's disease from vascular and mixed dementia.

CONCLUSION

Utilizing pupillometry in combination with the 0.01% tropicamide receptor test allows to discriminate between different dementia types of, as demonstrated in our study.

Technical Note: Comparison of the wavefront aberrations between natural and pharmacological pupil dilations

Ocular wavefront aberrations were tested with the wavefront-supported corneal ablation (WASCA) aberrometer when the pupil was dilated naturally under scotopic illumination levels, and pharmacologically using tropicamide. Wavefront aberrations were measured across a 5-mm pupil in one eye of each of 58 subjects. There was a significant difference in the pupil diameter between the scotopic and cycloplegic conditions (p < 0.001). For higher order aberrations (HOAs), no significant difference was found in Zernike coefficients between the scotopic and cycloplegic conditions. There was no significant difference in the spherical equivalent refraction. Accommodation can be neglected during the wavefront aberration measurement with the WASCA aberrometer. In view of the shift of the pupil centre caused by pharmacological pupil dilation, obtaining measurements under natural conditions rather than using mydriatics is recommended for customized laser in situ keratomileusis (LASIK) surgery.

Re-evaluation of tropicamide in the pupillary response test for Alzheimer's disease

In 1994, a pupillary response test using very dilute (0.01%) tropicamide, a cholinergic antagonist, evoked remarkable pupil dilation in subjects with Alzheimer's disease (AD) and has since been considered a diagnostic tool for AD. However, since this test was first reported, there have been studies suggesting it cannot provide a differential diagnosis of AD. Thus, the present study re-evaluated the pupillary dilation of AD (n=17) and non-AD (n=20) subjects at a 0.01% concentration of tropicamide and found that non-AD subjects, including young subjects, showed the same extent of pupil dilation as AD subjects. Furthermore, there was no significant difference between the average dilation rate of the two groups (P>0.05). When the tropicamide concentration was diluted to half of the initial concentration and performed for AD (n=14), vascular dementia (VD) (n=14), and young (n=16) subjects, the AD subjects showed a large dilation (mean pupil dilation rate: 133.8+/-15%) while the non-AD subjects did not show hypersensitivity to the new concentration of eye drops (105.4+/-9%). These differences in pupillary dilation between AD and non-AD patients were statistically significant (P<0.001). Based on these results, the most effective cutoff point of 0.005% tropicamide for differential diagnosis was 114.5% of the average pupil dilation rate for 60 min.

The effectiveness of screening for diabetic retinopathy by digital imaging photography and technician ophthalmoscopy

AIMS

To evaluate the introduction of a community-based non-mydriatic and mydriatic digital photographic screening programme by measuring the sensitivity and specificity compared with a reference standard and assessing the added value of technician direct ophthalmoscopy.

METHODS

Study patients had one-field, non-mydriatic, 45 degrees digital imaging photography prior to mydriatic two-field digital imaging photography followed by technician ophthalmoscopy. Of these patients, 1549 were then examined by an experienced ophthalmologist using slit lamp biomicroscopy as a reference standard. The setting was general practices in Gloucestershire. Patients were selected by randomizing groups of patients (from within individual general practices) and 3611 patients were included in the study. Patients for reference standard examination were recruited from groups of patients on days when the ophthalmologist was able to attend. The main outcome measure was detection of referable diabetic retinopathy (DR) as defined by the Gloucestershire adaptation of the European Working Party guidelines.

RESULTS

For mydriatic digital photography, the sensitivity was 87.8%, specificity was 86.1% and technical failure rate was 3.7%. Technician ophthalmoscopy did not alter these figures. For non-mydriatic photography, the sensitivity was 86.0%, specificity was 76.7% and technical failure rate was 19.7%.

CONCLUSIONS

Two-field mydriatic digital photography is an effective method of screening for referable diabetic retinopathy. Non-mydriatic digital photography has an unacceptable technical failure rate and low specificity.

Cholinergic dysfunction in cognitive impairments after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Although cognitive impairments have been observed after subarachnoid hemorrhage (SAH), little is known about their neurobiological bases. To examine cholinergic function in such patients, we used a known test for Alzheimer's disease based on an exaggerated pupil dilation response to a cholinergic antagonist, tropicamide (the tropicamide drop test).

METHODS

Seventeen patients who were treated surgically after aneurysmal SAH were divided into two groups on the basis of their scores on the Mini-Mental State Examination (MMSE): Group A (MMSE > or =28) and Group B (MMSE < or =27). The mean interval of time between surgery and administration of the MMSE was 4.7 +/- 2.1 years for Group A and 4.2 +/- 1.3 years for Group B. The tropicamide drop test was performed within 1 month after the MMSE for each patient. After measurement of the baseline pupil diameter (R1, right pupil size: L1, left pupil size), one drop of 0.01% tropicamide was applied to the right eye and physiological saline to the left eye. Pupil diameter (R2, right pupil size; L2, left pupil size) was then remeasured. Data were represented as the dilation ratio of the right pupil (R2/R1) and as the relative dilation ratio of the right pupil to that of the left pupil (R2L1/R1L2).

RESULTS

The mean dilation ratio of the right pupil (R2/R1) was higher in Group B (1.13 +/- 0.09) than in Group A (1.07 +/- 0.11), although the difference did not reach statistical significance (P = 0.18). The relative dilation ratio (R2L1/R1L2) was significantly higher in Group B (1.41 +/- 0.36) than in Group A (1.06 +/- 0.20) (P < 0.05).

CONCLUSION

We determined cholinergic dysfunction in patients with cognitive impairment after SAH on the basis of the pupillary response to tropicamide. The results provide an insight into the pathophysiology of cognitive impairments after SAH, which might lead to future treatment strategies.

Enhanced miotic response to topical dilute pilocarpine in patients with Alzheimer's disease

To determine whether miotic response to dilute (0.0625%, two drops) topical pilocarpine could be useful in detecting Alzheimer's disease (AD), we assessed the response in 14 AD patients and 10 control subjects. The miotic response to pilocarpine was significantly greater in AD patients than in control subjects (p < 0.001). In contrast, mydriatic response to the anticholinergic tropicamide (0.01%, one drop) failed to show a difference between the groups (p = 0.54). There was no significant correlation between the miotic and mydriatic responses in individuals. We conclude that dilute pilocarpine could be useful as a diagnostic tool in early AD.

A novel system for the objective classification of iris colour and its correlation with response to 1% tropicamide

Iris colour can provide an enormous amount of information about an individual. In addition to changes with pathological conditions, the colour of the iris can be a particularly useful indicator of how well a person will respond to a topically applied ocular drug. Until recently, classification of iris colour has been subjective, ranging from a basic description ('light' and 'dark') to more detailed grading systems, such as a comparison with preset photographic standards. However, variability within observers and differences in the interpretation between observers can influence the results. Objective techniques, in this respect, possess several advantages. They are able to detect differences in colour that subjective techniques are incapable of and they provide continuous data rather than discrete categories, thus improving the accuracy of drug response predictions. This study assessed iris colour by objective means. Slit-lamp photographs of various coloured irides were taken under standardised conditions. The slides were then scanned into a computer and the colour analysed using a calibrated software package. To establish the optimum colour parameter to be used for predictions of drug response, several parameters were calculated and compared with the subject response to 1% tropicamide (maximum change in pupil size, time to maximum change and total duration of effect). Many parameters had strong correlations with drug response, but the parameters 'z', 'b' (the proportion of blue in the image) and 'y' (the proportion of yellow in the image) were found to exhibit the highest correlations. They also showed better correlations with drug response than did a current iris colour grading system.

Is videopupillography useful in the diagnosis of Alzheimer's disease?

Patients with Alzheimer's disease (AD) reportedly exhibit greater pupillary dilation than healthy subjects in response to tropicamide. By means of videopupillography, we have found that the average basal pupillary diameter was greater in AD patients than in normal controls and that there is an inverse relationship between the average pupillary diameter and the maximal dilation obtained following tropicamide application in both groups. Pupillary response to tropicamide and videopupillography do not distinguish between Alzheimer's patients and controls.

Pupil dilation to tropicamide is not specific for Alzheimer disease

BACKGROUND

The extent of pupil dilation after instillation of a dilute tropicamide solution was proposed as a noninvasive neurobiological diagnostic test for Alzheimer disease (AD). Pupils in patients with AD dilated 23% vs only 5% in control subjects.

OBJECTIVE

To determine whether pupil dilation in response to tropicamide distinguishes patients with AD from control subjects without dementia.

METHODS

There were 50 patients with AD and 51 control subjects; no participant had primarily ocular pathological conditions or took drugs that affected cholinergic tone. All participants received 1 drop of 0.01% tropicamide in 1 eye and 1 drop of 0.9% saline solution in the other eye in random order. Pupil measurements were obtained using a pupil and corneal reflection tracking system (RK-426 PC system, ISCAN Inc, Burlington, Mass) that illuminated the eye with a low-level infrared source and measured pupil diameters, fixation, and light level every 16.7 milliseconds during each 30-second-measurement. Pupil measurements were obtained from each eye at baseline and 5, 10, 15, and 30 minutes after drop instillation.

RESULTS

The increase in pupil size after tropicamide instillation was equal between patients with AD and control subjects. The mean (+/- SD) pupil diameter increased from 4.5 +/- 1.1 to 5.5 +/- 1.1 mm after 30 minutes in patients with AD and from 4.7 +/- 0.9 to 5.8 +/- 0.9 mm in control subjects. Anisocoria and the mean rate of dilation did not differ between patients with AD and control subjects. Eye color and corneal moisture did not affect these results. The extent of pupil dilation in patients with AD was not related to clinical estimates of dementia severity.

CONCLUSION

Pupil dilation in response to instillation of 0.01% tropicamide is not useful as an antemortem diagnostic test for AD.

Pupil dilation response to tropicamide: a biological test for Alzheimer's disease?

The pupil dilation response to tropicamide has been proposed as a simple test for demonstrating the central cholinergic deficit present in Alzheimer's disease (AD). We examined this response in 20 patients with clinically diagnosed mild probable AD and in 20 unrelated, cognitively intact, age-matched controls. A marked increase in pupil diameter was observed within 30 minutes in both groups. Differences between the groups did not attain statistical significance. The ability of the proposed test to discriminate between AD patients and healthy controls may be influenced by experimental procedures and by the ethnic background of the subjects under study. At present the pupil dilation response to tropicamide cannot be considered a useful diagnostic aid.

Biological markers for the clinical diagnosis of Alzheimer's disease

There is a compelling need to develop biological marker(s) to confirm a clinical diagnosis of Alzheimer's disease (AD) during life in order to unequivocally identify AD patients for emerging therapeutic interventions. This review describes recent advances in the development of diagnostic marker(s) for AD. They include polymorphism of apolipoprotein E (ApoE) and alpha 1-antichymotrypsin as well as cerebrospinal fluid (CSF) tau and CSF-amyloid beta-protein levels, skin biopsy, and pupil dilatation assay by anti-cholinergic agent. In conclusion, ApoE genotyping should not be used as a sole diagnostic test for AD, and that monitoring of CSF-tau appeared to be most promising and reliable diagnostic aid.

The simultaneous interocular brightness sense test. A test of optic nerve function

OBJECTIVE

To describe and establish control data from controls for a simultaneous interocular brightness sense test in which the apparent brightness of two independently viewed light patches was compared.

DESIGN

Dichoptic viewing was achieved by dissociation of right and left eyes using a septum and cross-polarization. Brightness matches were obtained by using adjustments to the illumination of the left retina while the illumination of the right retina was kept constant. OBSERVERS: Ninety-one control observers (age range, 20 to 91 years) participated in the study to provide normal brightness-matching data.

RESULTS

Effects from ocular dominance, age, and long- and short-term adaptation were negligible, but the test was sensitive to anisocoria. Just noticeable differences in dichoptic brightness matching were proportional to retinal illuminance; this finding was consistent with the Weber-Fechner law.

CONCLUSION

The test is quick and simple to complete and appears to offer considerable scope for the assessment of visual function when differences in the functional integrity of the optic nerves of the right and left eyes are suspected.

The Canadian Optometry Survey: report on the utilization of diagnostic pharmaceutical agents by Canadian optometrists

This study represents the first national survey of optometrists in Canada. A mailed questionnaire was designed and implemented in order to discover how optometrists have reacted to the introduction of diagnostic pharmaceutical agent (DPA) legislation in Canada and to determine what variables are important predictors of DPA use. The data collected were also used to test the null hypothesis that DPA legislation does not affect the use of mydriatic/cycloplegic agents by optometrists. A stratified random sampling procedure was used to select 230 optometrists (roughly 10% of the practicing profession) for inclusion in the study. Over 90% of the subjects completed and returned the questionnaire. A statistically significant and important association was found between mydriatic/cycloplegic drug use and legislation (p less than 0.05 and odds ratio = 2.18). Legislation, type of practice, age, and optometry school attended were all found to be associated with DPA use.

People with Down's syndrome can be distinguished on the basis of cholinergic dysfunction

The mydriatic response to eyedrops of the anticholinergic agent tropicamide at very low concentration (0.01%) has been studied in people with Down's syndrome. By comparison with healthy subjects people with Down's syndrome had responses approximately three times greater, suggesting a peripheral imbalance between cholinergic and adrenergic autonomic influences.

Potential visual acuity measured with and without pupil dilation

Potential visual acuities were measured with the Randwal IRAS portable interferometer, with and without pupil dilation, on a sample of predominately elderly patients with mild to moderate cataract. No clinically significant difference was found between interferometer potential acuities before and after pupil dilation.

Noncycloplegic vs cycloplegic retinoscopy in pre-school children

Refractive errors in 311 children between the ages of 18 and 48 months were assessed utilizing standard cycloplegic retinoscopy and a noncycloplegic near retinoscopy technique as promulgated by Mohindra. Results from this study indicate little agreement between the two objective refraction methods.

Evaluation of laser iridectomy in angle-closure glaucoma: provocative tests

An argon laser iridectomy was performed on 18 eyes of 14 patients with closed-angle glaucoma. The intraocular pressure (IOP) was controlled in all but one eye within normal limits. Variable amounts of pigment were found on gonioscopy in all cases. The mydriasis test was positive in one eye (5.5%) after homatropine and in 5 eyes (28%) after tropicamide drops. 80% of the positive results occurred in lightly pigmented irides. The dark-prone position test was positive in 7 eyes (38%), 71% of the positive results occurring in heavily pigmented irides. Tomography was also performed; the possibility of trabecular damage is discussed.

Mydriatic solution for outpatient indirect ophthalmoscopy

A mydriatic used for outpatient indirect ophthalmoscopy should produce prompt, maximal, transient mydrasis after a single instillation. Cycloplegia or systemic side effects should be minimal. A solution of tropicamide with phenylephrine hydrochloride seems to achieve this most effectively. In a general retina clinic population, the percentage of pupils dilated, the degree of dilation, and the resistence of the dilation to intense illumination were used to evaluate various concentrations of the drugs. Eight-tenths percent tropicamide with 5% phenylephrine adequately dilated 98.8% of the eyes, among which 25% had dark irides and 9% were receiving miotic therapy. Reduction of the concentration of either component produced less adequate mydriasis; an increase of the tropicamide concentration resulted in a saturated solution with drug precipitate forming on storage and a less adequate dilation. With the optimal combination, 1 drop adequately dilates the general population; 2 drops appear on more effective than 1.

A new low-concentration preparation for mydriasis and cycloplegia

This study was designed to evaluate a low-concentration, cycloplegic-mydriatic mixture of phenylephrine and tropicamide in a routine office examination. No clinically significant difference in pupillary dilation was found between the usual instillation of the standard, commercially available phenylephrine 10% and tropicamide 1% drops and the prepared, low-concentration solution. Pupillary dilation was well maintained during direct and indirect ophthalmoscopy and retinoscopy. This solution is easily prepared from readily available drugs, and is simply delivered to the eye using a standard eye dropper. The safety and effectiveness of this low-concentration mixture of phenylephrine and tropicamide make it strongly recommended for routine use.