Effects of adrenergic drugs on accommodation and distant refraction in daylight and darkness. A laseroptometric study

Near point accommodation was measured using a RAF near point rule, and distant refraction in daylight and darkness were determined using a laseroptometer in a double-blind cross-over study on 10 healthy test subjects (19-31 years). Determinations were made before and 40 min after topical instillations of 3 X 10 microliters 10% phenylephrine, 0.5% thymoxamine, 1% adrenaline, 3% isoproterenol, 0.5% timolol and 0.5% betaxolol. Combinations of 3 X 10 microliters 0.5% thymoxamine + 10% phenylephrine, 0.5% timolol + 1% adrenaline and 0.5% betaxolol + 3% isoproterenol were also administered. The near point of accommodation decreased 0.8 +/- 0.3 diopter after instillations of the alpha 1 adrenoceptor agonist phenylephrine, while an increase of 0.6 +/- 0.2 diopter was determined after administration of the alpha adrenoceptor antagonist thymoxamine. Thymoxamine plus phenylephrine did not alter the pretreatment values. Beta adrenoceptor stimulation by isoproterenol or beta adrenoceptor inhibition by timolol or betaxolol had no effect on the near point accommodation. The difference between distant refraction in daylight and darkness, that is low-luminance myopia, amounted to -1.25 +/- 0.1 diopter. Phenylephrine caused a myopic shift in distant refraction in daylight and darkness of 0.32 +/- 0.1 and 0.9 +/- 0.2 diopter, respectively. This effect was due to the mydriatic action of phenylephrine.(ABSTRACT TRUNCATED AT 250 WORDS)