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Automated refraction. A comparative study of automated refraction with the Nidek AR-1000 autorefractor and retinoscopy.

A prospective study was performed on 46 eyes to compare results of different methods of objective refraction, namely automated refraction with the Nidek AR-1000 autorefractometer and retinoscopy in cycloplegia. We found that automated refraction in cyclopentolate cycloplegia gave results that differed little from results of retinoscopy in atropine cycloplegia both with respect to sphere and cylinder. Axis determination was even better with automated refraction. Dry automated refraction gave inaccurate results for the spheric component presumably because of suboptimal control of accommodation in this group of young patients. We recommend automated refraction in cyclopentolate cycloplegia as an easy, rapid, accurate and convenient method for obtaining an objective refraction where accommodative disorders are suspected.

Accommodation, Ocular

Dilating dangerous pupils.

Altogether 85 eyes from patients at risk to the development of closed-angle glaucoma were dilated with either parasympatholytic or sympathomimetic drugs. Of 21 eyes dilated with cyclopentolate 1/2%, 9 developed angle closure and a significantly raised pressure at some stage during dilatation and subsequent miosis. Of 58 eyes dilated with tropicamide 1/2%, 19 developed angle closure and a significantly raised pressure during dilatation. Treatment with intravenous acetazolamide and pilocarpine rapidly returned pressure to normal levels. Six eyes that had previously had a positive provocative test with simultaneous pilocarpine and phenylephrine were safely dilated with phenylephrine alone. Subsequent miosis with pilocarpine produced closed-angle glaucoma in all eyes. The significance of these observations is explained and discussed, and it is suggested that high-risk eyes should never be dilated with cyclopentolate. Tropicamide is safe if elementary precautions are observed. Safest of all, however, is phenylephrine-induced mydriasis and subsequent miosis with thymoxamine drops 1/2%.

Acetazolamide

In vivo observation of the axial movement of intraocular lenses through an anterior eye segment analysis system.

The small axial movement of the anterior surface of implanted intraocular lenses (IOLs) were examined in pseudophakic eyes with one-piece and three-piece IOLs using an anterior eye segment analysis system. The movement was calculated as the distance between the posterior surface of the cornea and the anterior surface of an IOL under a normal pupil size, following the instillation of 1% pilocarpine and 1% cyclopentolate solutions, respectively. The axial movement including movement after instillation of pilocarpine and cyclopentolate was 0.17 +/- 0.06, 0.05 +/- 0.07 and 0.13 +/- 0.06 mm, in phakic eyes and eyes with one-piece and three-piece IOLs, respectively. Image analysis techniques using Scheimpflug images proved its usefulness in the research field of IOL implantation.

Adolescent

Review: systemic absorption of topically applied ocular drugs in humans.

Literature on human plasma concentrations after instillation of ocular timolol, levobunolol, atropine, cyclopentolate, scopolamine, phenylephrine, betamethasone and technetium Tc 99m and theories of lacrimal drainage were reviewed. In all studies the eyedrops absorbed rapidly into the systemic circulation. Like the kinetics of the tracer substances in lacrimal scintigraphy, the plasma drug levels showed interindividual variations. Plasma levels of ocular drugs were lower when punctal occlusion was applied, the mechanism, however, could not be explained. Since an early and a late plasma peak was occasionally registered in some subjects in timolol and cyclopentolate studies, it is suggested that systemic absorption of ocular drugs is low during the nasolacrimal passage but occurs during conjunctival and nasal contact.

Absorption

Pseudophakic accommodation? A study of the stability of capsular bag supported, one piece, rigid tripod, or soft flexible implants.

A group of pseudophakic patients was investigated to determine whether their implants shift along an anteroposterior axis under different conditions of ciliary muscle stimulation. There was no statistically significant change in refraction after either pilocarpine or cyclopentolate administration. A change in anterior chamber depth between the position after pilocarpine and that after cyclopentolate was found. It appears that rigid posterior chamber implants do move backwards on ciliary muscle relaxation, but by a maximum 0.25 mm. This is not thought to represent a mechanical threat to ocular health. It is also not enough to account for the apparent accommodative ability of some pseudophakic patients. The possible causes for this phenomenon are discussed.

Accommodation, Ocular

The refractive status of Hong Kong Chinese infants.

One hundred and fifty-eight full-term Hong Kong Chinese infants were examined, at the age of approximately 10 weeks, using retinoscopy. Fifty of the subjects were re-examined at the ages of 20, 30 and 40 weeks. Cyclopentolate 1% was used to produce cycloplegia. Photographic methods were used to assess the straightness of the eyes of 122 infants. While the mean spherical equivalent of the refractive error at 10 weeks was within the limits reported in studies of Caucasian infants, a rapid decrease, not previously reported, occurred between the ages of 10 and 40 weeks. The amounts of astigmatism found were in line with results from Caucasian eyes but the direction was overwhelmingly with-the-rule. The prevalence of anisometropia decreased with age and anisometropia was not prevalent at the age of 37 weeks. Two exotropes (1.6%) and no esotropes were identified although this may have been confounded by the use of cyclopentolate.

Astigmatism

Topical phenylephrine for mydriasis affects rabbit retinal pigment epithelial transport.

Rabbit retinal pigment epithelium (RPE) has an alpha-1 adrenoreceptor that substantially reduces RPE short circuit current (Isc) when stimulated. Since phenylephrine is a potent alpha adrenergic agonist frequently used to obtain pupil dilation, we examined the effect of topically applied phenylephrine for pupil dilation on RPE transport. Naive black dutch-belted rabbits received either one drop of 10% phenylephrine applied at t = 0 and t = 30 min or one drop of 1% cyclopentolate applied at t = 30 min. At t = 50 min, RPE-choroid-sclera explants from these animals were sealed in an Ussing chamber. At t = 60-70 min, 1.4 X 10(-4) M epinephrine was introduced into both sides of the Ussing chamber. The change in Isc produced by epinephrine was measured. The Isc reduction in rabbits receiving phenylephrine was 26% (+/- 5% SD, n = 6). The Isc reduction in rabbits receiving cyclopentolate was 39% (+/- 6% SD, n = 5). These values are significantly different (P less than 0.02, student two-tail t-test). These results indicate that topical phenylephrine reached the RPE in vivo and prestimulated the alpha-1 adrenoreceptors.

Administration, Topical

Evaluation of drugs in ointment for mydriasis and cycloplegia.

Ointment preparations of cyclopentolate hydrochloride and tropicamide were compared with aqueous drops of these medications for the production of mydriasis and/or cycloplegia in clinic patients. Mydriasis and/or cycloplegia could be accomplished by the single application of a minute volume (around 0.005 ml) of ointment containing these drugs. With the use of ointment preparation, ocular irritation was minimal, and there was no interference with subsequent ocular examination. A delivery system was devised with a piece of silicone-rubber tubing that was filled with an ointment preparation. By squeezing the tubing, a minute volume (about 0.005 ml) of ointment preparation was expressed.

Accommodation, Ocular

Feeding intolerance following ophthalmologic examination.

Reports of isolated cases of necrotizing enterocolitis following administration of mydriatric medication and ophthalmologic examination prompted a comparison of the incidence of feeding difficulties 24 hours before and 24 hours after the ophthalmologic examination of 50 newborns. All infants had received cyclopentolate hydrochloride and phenylephrine hydrochloride before the examination. A critical review of the nursing notes showed more abdominal distention and gastric aspirates in the period following the examination than in the period preceding the examination. One infant developed necrotizing enterocolitis during the 24-hour postexamination period. This study demonstrates the risk of feeding intolerance following the ophthalmologic examination of neonates. These risks may be due to the known side effects of the mydriatics, to the physical stress of the examination, or to a combination of both factors.

Animals

Pupillary dilatation with single eyedrop mydriatic combinations.

We studied the mydiatic effect of three solutions containing a combination of two mydriatic drugs in 80 adult patients. The solutions tested were cyclopentolate HCl 0.5% with phenylephrine 2.5%, tropicamide 0.5% with phenylephrine 2.5%, and tropicamide 1.0% with phenylephrine 2.5%. We evaluated the effect of prior instillation of proparacaine 0.5% eyedrops. All three mydriatic combination solutions evaluated produced pupillary dilatation of about 7 mm within 60 minutes. Additional pupillary dilatation of 1 mm occurred when proparacaine was instilled before the mydriatic combination eyedrop. Mydriasis was resistant to bright light during indirect ophthalmoscopy in all patients. Pupils of younger patients dilated better than those of older patients, but sex and iris color were factors in the amount of pupillary dilatation obtained. Wide and sustained pupillary dilatation can be obtained for satisfactory indirect ophthalmoscopy by the instillation of one drop of proparacaine solution followed by a single drop of any of the three mydriatic combination solutions evaluated. By eliminating the need for multiple instillations of drugs, the use of a single eyedrop mydriatic combination is convenient in terms of time saved and also lessens the change of systemic drug toxicity.

Adolescent

The oval pupil.

The dynamics of pupillary dilation induced by Phenylephrine 10% and Cyclopentolate 1% have been examined by flash photography. A correlation between anterior chamber depth and the pupil shape on dilation with Phenylephrine Hydrochloride 10% is described. It is postulated that these pupillary dilation dynamics support a sympathetic abnormality as a trigger for acute primary angle closure glaucoma.

Adolescent

Can retinoscopy be used to screen infants for amblyopia? A longitudinal study of refraction in the first year of life.

One hundred normal babies were refracted by two observers in a double-masked study within 24 hours of delivery and 30 minutes after instillation of 1% cyclopentolate. The procedure was repeated at 6 weeks, 3 months, 6 months and 1 year. At birth agreement between the two refractionists to within 1 dioptre spherical equivalent was 82%, rising to 94% at 1 year. Astigmatism of greater than 1 dioptre increased from 10% at birth to 42% at 6 months but decreased to 15% at 1 year. Myopia was uncommon (4%) but 80% of eyes were hypermetropic more than +2 dioptres and 25% more than +4 dioptres at birth, although these percentages decreased to 5% and 3% at 1 year. Anisometropia of more than 1 dioptre between the two eyes was uncommon but in the two cases where it persisted in the presence of high hypermetropia, reversible amblyopia was encountered in both cases.

Aging

The effect of mydriasis on the pupillary centration of the human eye.

The change in pupil centration occurring as the human eye pupil dilates, both naturally in darkness and following the use of a mydriatic drug (cyclopentolate HCl, 1%), has been measured photographically. In both cases, changes in centration of up to 0.4 mm have been found. Using available ocular wavefront aberration data, modulation transfer curves have been derived for two eyes for centration changes of 0.2 mm. The importance of these changes in the formation of the retinal image, and hence on visual performance, is discussed.

Adult

Myopia prevention and therapy. The role of pharmaceutical agents. Japanese studies.

In order to normalize the condition of pseudomyopia, the following can be summarized: One percent cyclopentolate was effective in 63%, and 0.4% tropicamide was effective in 59% of the cases. With a value of 68% after labetalol eye drops there were no significant differences in efficacy between this drug and the above cycloplegics. In subjects treated only with placebo, 4 out of 16 eyes, i.e. 25% were relieved. A significant difference (P less than 0.01) was found between the results with the above 3 drugs and placebo. On the other hand, the efficacy of 0.25% timolol (effect in 28%) and chemical X (effect in 37%) were not significantly different from the effect of placebo, though the results with chemical X encourage further trials. It can be postulated that by releasing an abnormal tension cycloplegics reduce the myopic condition. Regarding the hypotensive action of beta-adrenergic blockers on intraocular pressure, it presumably depends mainly on inhibition of secretion in the ciliary body. The fact that labetalol appeared effective, and timolol not, in treatment trials of slight myopia might imply that the mechanism behind an effect of labetalol on slight myopia is not merely a beta-adrenergic blocking action.

Adolescent

Systemic response to mydriatic eyedrops in neonates: mydriatics in neonates.

During routine dilation of 48 newborns, systemic responses and pupil dilation were monitored. Both 10 percent aqueous and viscous phenylephrine caused blanching around the eyes and produced considerable rise in blood pressure. Dilatation average 4.7 mm. In a double blind study, a 2.5 percent solution caused no skin blanching and no change in pressure or heart rate. Average dilation was 4.5 mm. No blood pressure changes were observed with either one percent cyclopentolate or one percent tropicamide. Average dilatations were 5.0 mm and 5.3 mm respectively. The above agents, used individually for a total dosage of three drops in each eye did not provide adequate dilation for a thorough funduscopic examination. Our protocol at United Hospitals Medical Center is a safe combination of drugs and provides excellent dilatation averaging greater th an 7 mm. No skin blanching or change in heart rate was observed.

Birth Weight

Cycloplegic refraction after echothiophate iodide.

Retinoscopy under cycloplegia using cyclopentolate (Cyclogyl) hydrochloride was performed on 18 patients (36 eyes) with partial or complete accommodative esodeviation, during and after treatment with echothiophate (Phospholine) iodide. Measurements were clinically comparable on both occasions, regardless of concentration of echothiophate, duration of administration, or interval from discontinuance until refraction. It appears to be unnecessary to discontinue echothiophate iodide in order to obtain reliable cycloplegic retinoscopic measurements.

Accommodation, Ocular

Abolition of feeding intolerance following ophthalmologic examination of neonates.

Administration of mydriatic medication and ophthalmologic examination have previously been associated with feeding intolerance, characterized by large retained gastric aspirates and abdominal distention. In an attempt to eliminate this problem, we instituted a policy of withholding feedings for four hours following ophthalmologic examination. A prospective series of 50 consecutive patients was then followed to determine the incidence of feeding intolerance 24 hours prior to and 24 hours following the examination. All infants had received cyclopentolate hydrochloride and phenylephrine hydrochloride prior to the examination. A critical review of the nursing notes revealed no increased incidence in feeding intolerance during the 24-hour period following examination. There were no cases of necrotizing enterocolitis during either period. This study provides evidence that the incidence of feeding intolerance following ophthalmologic examinations might be reduced by withholding feeding for four hours after the examinations.

Cyclopentolate