Pupil location under mesopic, photopic, and pharmacologically dilated conditions.
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PURPOSE: To determine whether there are systematic changes in pupil location with changes in the state of pupil size and with other ocular variables. METHODS: High-resolution images of the pupil of the eyes of 70 subjects were taken using an infrared-sensitive camera. Images were obtained under mesopic, photopic, and pharmacologically dilated conditions. From the images, the center and diameter of the corneal limbus and the pupil were computed. In addition, the location of the first Purkinje image was calculated. RESULTS: The pupil center shifted consistently temporally as the pupil dilated. The total motion was relatively small, with a mean distance of 0.133 mm motion between the mesopic and photopic conditions, with the pupil diameter changing from 6.3 to 4.1 mm. Ninety percent of the subjects had a motion of less than 0.3 mm. One patient showed a motion of almost 0.6 mm. The change in location of the pupil center was not significantly related to refractive error, age, or the change of pupil diameter. CONCLUSIONS: Changes in the location of the pupil center with changes in the dilation of the pupil are typically slight, but can be significant in a few subjects, especially in pharmacologically dilated pupils. (+info)
Changes in intraocular pressure following diagnostic mydriasis with cyclopentolate 1%.
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PURPOSE: To assess the effect of diagnostic mydriasis with 1% cyclopentolate on the intraocular pressure (IOP) of patients attending glaucoma, medical retina and cataract clinics. METHODS: Levels of agreement for IOP assessment were determined and 95% of repeated readings found to be within +/-2 mmHg. The IOP of 83 cataract, 87 medical retinal and 100 glaucoma patients was measured with Goldmann applanation tonometry before and 45 min after dilatation with 1% cyclopentolate. Those showing a substantial (>10 mmHg) increase in IOP underwent gonioscopy to determine if their angles remained open and were medically treated to lower their IOP. RESULTS: An approximately normal distribution of change in IOP following dilatation was seen in all three groups (mean change 0.4 mmHg (95% CI 0.1-0.8)). The proportion of patients with a rise of 5 mmHg or more in the right eye was 7% (95% CI 4-10%). Logistic regression using all right eyes, looking at age, sex, diagnosis, ethnicity, ocular medication, iris colour and lens status (phakic/pseudophakic/aphakic) as risk factors for a rise of IOP of 5 mmHg or more did not reveal any significant contribution. Correlation between results obtained for right and left eyes in the glaucoma group was lower (0.43) than for the other groups (0.66 and 0.72), but the extent to which the direction of change in one eye predicted that in the other was shown to be high. Two glaucoma patients with open angles developed a clinically important (>10 mmHg) sustained rise in IOP requiring treatment. CONCLUSIONS: Individual variability in the effects of cyclopentolate on aqueous dynamics may account for the approximately normal distribution of IOP seen following dilatation in all three groups. This variation was in excess of that due to observation error alone. It is recommended that the IOP be rechecked after dilation in glaucoma patients with significantly damaged optic nerve heads. In medical retina and cataract patients, sustained clinically important rises in intraocular pressure following dilation seem rarer. (+info)
Dilating dangerous pupils.
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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%. (+info)
Cholinergic innervation of the mouse isolated vas deferens.
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Recently, a population of nerves has been described in the aganglionic mouse vas deferens, in which electrically evoked contractions were insensitive to high concentrations of the adrenergic neurone blocker, bretylium. In this paper, the pharmacology of this nerve-evoked contraction has been examined in more detail. Bretylium (20 microM) revealed, after 5 h exposure, a new residual neurogenic contraction (20 stimuli at 10 Hz) that was tetrodotoxin-sensitive. The muscarinic antagonist, cyclopentolate (0.1 and 1 microM), reduced this residual component and the inhibition was reversed by the acetylcholinesterase inhibitor, neostigmine (1 and 10 microM). Nicotine (30 microM) enhanced the residual component revealed by bretylium, suggesting that there are prejunctional nicotinic receptors (nAchRs) influencing acetylcholine (Ach) release. In the presence of prazosin (0.1 microM), a selective alpha(1)-adrenoceptor antagonist, and alpha,beta-methylene ATP (1 microM), a purinergic agonist that desensitise P2X receptors, neostigmine increased the hump component of contraction and yohimbine (0.3 microM), an alpha(2)-adrenoceptor antagonist, enhanced both components of the electrically evoked stimulation. The contraction was blocked by cyclopentolate (1 microM). In the absence of bretylium, neostigmine alone increased the hump component of contraction in a frequency-dependent manner. This increase was reversed by atropine (1 microM) and cyclopentolate (1 microM) to control levels. However, in control experiments, atropine or cyclopentolate did not detectably influence the delayed neurogenic contraction. Ach (10 microM) induced a contraction in the mouse vas deferens, either when applied alone or in the presence of neostigmine.Thus, it has been demonstrated unequivocally that the mouse vas deferens is innervated by functional cholinergic nerves, whose action is terminated by cholinesterase. Furthermore, Ach release can be enhanced by activation of prejunctional nAchRs presumably located on the cholinergic nerve terminals. (+info)
Cost-effectiveness of cycloplegic agents: results of a randomized controlled trial in nigerian children.
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PURPOSE: To compare the cost and effectiveness of three cycloplegic agents among Nigerian children. METHODS: Two hundred thirty-three children aged 4 to 15 years attending outpatient eye clinics in Nigeria were randomized to (1) 1% cyclopentolate, (2) 1% cyclopentolate and 0.5% tropicamide, or (3) 1% atropine drops in each eye (instilled at home over 3 days). Ten children were lost to follow-up, nine from the atropine group. An optometrist measured the residual accommodation (primary outcome), dilated pupil size, pupil response to light, and self-reported side effects (secondary outcomes). Caregivers were interviewed about costs incurred due to cycloplegia (primary outcome). The incremental cost effectiveness ratios (ICERs) were calculated as the difference in cost divided by the difference in effectiveness comparing two agents. The 95% confidence intervals (CI) for ICERs were estimated through bootstrapping. RESULTS: The atropine group had significantly lower mean residual accommodation (0.04 +/- 0.01 D [SE]), than the combined regimen (0.36 +/- 0.05 D) and cyclopentolate (0.63 +/- 0.06 D) groups (P < 0.001). Atropine and the combined regimen produced better results for negative response to light and dilated pupil size than cyclopentolate. Atropine was more expensive, but also more effective, than the other agents. The ICER comparing atropine to the combined regimen was 1.81 (95% CI = -6.31-15.35) and compared to cyclopentolate was 0.59 (95% CI = -3.47-5.47). The combined regimen was both more effective and less expensive than cyclopentolate alone. CONCLUSIONS: A combination of cyclopentolate and tropicamide should become the recommended agent for routine cycloplegic refraction in African children. The combined regimen was more effective than cyclopentolate, but not more expensive, and was preferable to atropine, since it incurred fewer losses to follow-up. (+info)
Is age relevant for the success of treatment of anisometropic amblyopia?
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A prospective cohort study of 200 anisometropic amblyopes was conducted. The patients were classified into two groups. Group A: Patients less than 12 years of age. This consisted of 144 (72%) patients, the average age being 7.77 years (+/-2.34, range 1 to 12). Group B: Patients more than 12 years of age. This comprised 56 (28%) patients, the average age being 19.8 years (+/-5.47, range 12 to 30). Criterion for success was defined as best corrected visual acuity of 20/40 (0.5 logMAR equivalent) or better. The Chi-square test was used to compare baseline characteristics and success rates. There were no significant differences in the baseline characteristics between the two groups ( P =0.07). The treatment was successful in 108 (75%) in Group A and in 34 (60.7%) in Group B ( P = 0.07). There was no statistically significant change in the success rate of treatment of anisometropic amblyopia, even beyond 12 years of age. (+info)
Heidelberg retinal tomography of optic disc and nerve fiber layer in singapore children: variations with disc tilt and refractive error.
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PURPOSE: To evaluate the relationships in Singapore school children between optic nerve head parameters and retinal nerve fiber layer thickness images by using the Heidelberg Retinal Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) and determining optic disc tilt and refractive error. METHODS: This was a cross-sectional study involving 316 children 11 and 12 years of age (163 girls and 153 boys) selected randomly from one of the three schools in the Singapore Cohort study of Myopia. A total of 13 optic disc parameters were obtained from HRT images acquired before cycloplegia. Refractive errors were measured by cycloplegic autorefraction. The presence of optic disc tilt or otherwise was determined by two independent assessors using stereoscopic viewing of retinal photographs. RESULTS: Of the 316 children, 142 had tilted discs. The tilting of optic discs was associated with a smaller disc, rim or cup area measurements, cup-to-disc area ratios, cup volumes or cup depths, but with a larger measured rim volume, rim-to-disc area ratios, height variation of the contour, retinal nerve fiber layer thicknesses or volumes, and a more negative cup shape measure (all P < 0.001). Decreased maximum cup depths were significantly associated with longer axial lengths (P < 0.001), but were not associated with spherical equivalent (P = 0.693). These associations remained only in children without tilted discs, but were no longer significant in those with tilted discs. Other HRT parameters were not associated with axial lengths or myopic status. CONCLUSIONS: Optic nerve head parameters and retinal nerve fiber layer thickness measured by the current HRT algorithms are strongly influenced by the tilting of the optic nerve head, but not by refractive errors or axial length. (+info)
Cholinergic innervation of the guinea-pig isolated vas deferens.
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Recently, a cholinergic neurogenic component of contraction has been characterised in the aganglionic mouse vas deferens. In this paper, a cholinergic component of contraction in the guinea-pig vas deferens is characterised pharmacologically. A residual, tetrodotoxin-sensitive (TTX, 0.3 microM), neurogenic contraction was revealed after prolonged exposure (5 h) to the adrenergic neurone blocker bretylium (20 microM) or in the presence of prazosin (100 nM) and alpha,beta-methylene ATP (1 microM), a purinergic agonist which desensitizes P2X receptors. The bretylium-resistant component was potentiated by the acetylcholinesterase (AChE) inhibitor neostigmine (10 microM) and inhibited by the muscarinic-receptor (mAChR) antagonist cyclopentolate (1 microM). Nicotine (30 microM) enhanced the bretylium-resistant component. Neostigmine increased the second component of contraction in the presence of prazosin and alpha,beta-methylene ATP, whilst yohimbine (1 microM), an alpha(2) adrenergic receptor antagonist, enhanced both the first and second components of the electrically evoked contraction. These enhanced contractions were blocked by cyclopentolate in both cases. Nicotine enhanced the cholinergic component of contraction revealed by neostigmine but failed to have any detectable effects in the presence of cyclopentolate. Neostigmine alone increased the slow component of contraction which was reversed by cyclopentolate to control levels. The M(3) receptor-antagonist 4-DAMP (10 nM) markedly inhibited the cholinergic component of contraction to a level comparable with cyclopentolate. Laser microscopy has shown that neostigmine also increased the frequency of spontaneous Ca(2+) transients remaining in smooth muscle cells after perfusion with prazosin and alpha,beta-methylene ATP, an effect blocked by 4-DAMP. These experimental data show that there is a functional cholinergic innervation in the guinea-pig vas deferens whose action is limited by acetylcholinesterase, blocked by cyclopentolate and mediated through M3 receptors. Moreover, by blocking the cholinesterase, the increased amount of ACh generates spontaneous Ca(2+) transients in smooth muscle cells. (+info)