RESUMEN
PURPOSE: As suggested by findings of abnormal responses to posture in patients with normal-tension glaucoma (NTG), cardiovascular autoregulation may also be defective in primary open-angle glaucoma (POAG). PATIENTS AND METHODS: Both 24-hour ambulatory blood pressure monitoring and the head-up tilt test were performed in 17 subjects with NTG and in 13 subjects with high-tension POAG (ht-POAG). These groups were compared with 17 age-matched healthy individuals. Subjects undergoing cardiovascular therapy were excluded. RESULTS: No significant differences in diurnal and nocturnal blood pressure and heart rate were found between the groups. A significant reduction in diurnal heart rate variability was found in NTG (12.1 +/- 2.8 bpm) compared with the ht-POAG (15.0 +/- 2.4 bpm, P < 0.01) and control groups (15.8 +/- 3.0 bpm, P = 0.01]). Nocturnal diastolic blood pressure variability was also reduced in NTG (6.9 +/- 2.2 mm Hg) compared with controls (8.6 +/- 2.3 mm Hg, P < 0.05]) as was heart rate variability (6.3 +/- 1.4 vs 8.3 +/- 2.6 in ht-POAG, P < 0.05), suggesting blunted blood pressure and heart rate modulation in NTG subjects. Spectral analysis of short-term heart rate variability showed a significant reduction of total power in the supine position (1064 +/- 600 in NTG vs 1688 +/- 889 ms2 in controls, P < 0.05]). This was not accompanied either by a physiological reduction in total power or in a high-frequency component during the passive orthostatic stimulus. These differences tend to become more prominent in the clinically more severe forms of NTG (as identified by scores based on the extent of optic disk excavation, visual field damage, and progression of disease). This would suggest a correlation between the extent of autonomic disorder and severity of glaucoma. The alpha index (root-square of low-frequency heart rate to low-frequency blood pressure ratio) was lower in the supine position in NTG subjects (8.1 +/- 3.1 vs 10.6 +/- 3.3 ms/mm Hg in controls, P < 0.05), confirming the reduced baroreflex sensitivity. CONCLUSIONS: The results confirm the hypothesis that dysfunction of autonomic control of the cardiovascular response may be a contributing pathogenetic factor in NTG, inducing a chronic ischemia of the optic nerve.
Asunto(s)
Sistema Nervioso Autónomo/fisiología , Presión Sanguínea/fisiología , Ritmo Circadiano/fisiología , Glaucoma de Ángulo Abierto/fisiopatología , Monitoreo Ambulatorio de la Presión Arterial , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Presión Intraocular , Masculino , Persona de Mediana Edad , Posición Supina , Pruebas de Mesa InclinadaRESUMEN
PURPOSE: To assess in normal and glaucomatous eyes the effect of the dopaminergic drug 2% ibopamine on visual acuity, IOP, pupil size and anterior segment geometry, compared with 10% phenylephrine and 1% tropicamide. METHODS: Fifteen healthy subjects and 15 patients with primary open-angle glaucoma, aged from 40 to 70 years (mean age: 54.8 +/- 9.6), were recruited into this open prospective study. After instillation of 2% ibopamine, refraction, visual acuity, pupil diameter, IOP, five A-scan ultrasonographic parameters, and 15 ultrasound biomicroscopy parameters were evaluated. The study was repeated with assessment of the same parameters 20 to 30 days later in 10 subjects (5 normal and 5 with glaucoma), using first 10% phenylephrine and then 1% tropicamide. A second group of 15 healthy subjects, aged from 45 to 70 years (mean age: 53.5 +/- 8.6) was examined to evaluate the dose-response effect and time course on pupil diameter, of ibopamine, phenylephrine, and tropicamide. RESULTS: After 40 minutes 2% ibopamine induced a marked mydriatic effect (from 5 to 9.1 mm; P < 0.0001) greater than that produced by 10% phenylephrine (from 4.7 to 7.9 mm; P < 0.0001) or 1% tropicamide (from 4.6 to 6.9 mm; P < 0.0001), with no changes in refraction or visual acuity. IOP was significantly increased only in patients with glaucoma after instillation of either 2% ibopamine (from 22.2 to 24.8 mm Hg; P < 0.0001) or 1% tropicamide (from 21.2 to 23.6 mm Hg; P = 0.004), whereas 10% phenylephrine induced no statistically significant changes. Ibopamine (2%) caused a significant increase in iris thickness with a reduction of the sulcus ciliaris and posterior chamber depth. The anterior chamber angle (ACA) showed a mean 5 degrees widening with an increase in scleral-iris angle (SIA) and sclera-ciliary process angle. In 11 (37%) of 30 cases, separation of the pupil border and lens surface occurred, whereas contact was maintained only with the zonule in the other 19 (63%) of 30. The changes after 10% phenylephrine instillation were similar, although only the increase in iris thickness and SIA was statistically significant. Tropicamide (1%) induced a slight but significant increase in SIA. CONCLUSIONS: The results confirm the potent mydriatic effect of 2% ibopamine, which is greater than that of either 10% phenylephrine or 1% tropicamide, as well as its ability to induce an increase in intraocular pressure when used in patients with glaucoma alone. These data support the hypothesis that the widening of the ACA induced by 2% ibopamine is due to posterior rotation of the iris plane and ciliary processes. These changes are quantitatively greater than those induced by 10% phenylephrine and 1% tropicamide and are related to the greater mydriatic effect of the drug.
Asunto(s)
Segmento Anterior del Ojo/efectos de los fármacos , Desoxiepinefrina/análogos & derivados , Desoxiepinefrina/farmacología , Midriáticos/farmacología , Fenilefrina/farmacología , Pupila/efectos de los fármacos , Tropicamida/farmacología , Adulto , Anciano , Segmento Anterior del Ojo/diagnóstico por imagen , Desoxiepinefrina/administración & dosificación , Relación Dosis-Respuesta a Droga , Femenino , Glaucoma de Ángulo Abierto/complicaciones , Humanos , Presión Intraocular/efectos de los fármacos , Iris/diagnóstico por imagen , Iris/efectos de los fármacos , Masculino , Persona de Mediana Edad , Midriáticos/administración & dosificación , Soluciones Oftálmicas , Fenilefrina/administración & dosificación , Estudios Prospectivos , Refracción Ocular/efectos de los fármacos , Factores de Tiempo , Tropicamida/administración & dosificación , Ultrasonografía , Agudeza Visual/efectos de los fármacosRESUMEN
PURPOSE: To evaluate the intra- and interobserver variability of the Ocuton S tonometer, its correlation with Goldmann tonometry, the reliability of self-tonometry and the safety of the instrument. METHODS: Thirty-five healthy subjects and 45 patients with primary open-angle glaucoma (POAG), aged from 38 to 80 years (mean age: 64.6 +/- 12.2 years), underwent tonometry with the Ocuton S tonometer in one eye chosen at random. The intra- and interobserver variability between two operators (kappa coefficient), the Ocuton S/Goldmann correlation and the reliability of self-tonometry were evaluated by performing two tonometries on each patient in subgroups. Each tonometry was considered as the mean of three consecutive measurements. Central ultrasonic pachymetry, keratometry and corneal biomicroscopy were also evaluated. RESULTS: The intra- and interobserver variability ranged from 0.38 to 0.66. The difference between the means of intraocular pressure (IOP) with the Ocuton S (24.4 +/- 4.7 mmHg) and the Goldmann tonometer (18.1 +/- 4.7 mmHg) was statistically significant (p < 0.0001). Linear regression analysis revealed a good Ocuton S/Goldmann correspondence (r = 0.88, p = 0.0001). However, IOP values detected with the Ocuton were consistently overestimated, compared to those detected with the Goldmann tonometer. The correlation between corneal thickness and IOP was statistically significant both for the Goldmann (r = 0.510, p = 0.021) and for the Ocuton S tonometer (r = 0.520, p = 0.019). No correlation was found between keratometry and IOP. The mean measurement obtained by self-tonometry (21.9 +/- 3.6 mmHg) showed no statistically significant difference when compared to the mean measurement obtained by an expert operator (21.3 +/- 3.4 mmHg). CONCLUSION: The Ocuton S tonometer is a safe instrument that can be used easily by the patient. However, in comparison to the Goldmann tonometer, it overestimates IOP and requires further technical and methodological refinements in order to ensure greater reliability.