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The effects of thymoxamine, phenylephrine and cyclopentolate on the accommodative process in man
Author(s) -
Zetterström Charlotta
Publication year - 1987
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.1987.tb07066.x
Subject(s) - cyclopentolate , phenylephrine , cycloplegia , medicine , dioptre , accommodation , ophthalmology , anesthesia , eye disease , psychology , blood pressure , visual acuity , neuroscience , refractive error
Accommodation of the eye was measured in a cross‐over study in 11 healthy volunteers (20–35 years). In 5 subjects the near point was determined before and after topical instillation of 5 μl of 0.1% and 0.5%, and 5 × 5 μl 0.5% thymoxamine, 5 μl of 2% and 10%, and 5 × 5 μl 10% phenylephrine and 5 μl of 0.04%, 0.2%, and 1% cyclopentolate. All concentrations of thymoxamine increased the accommodative amplitude by about 1.5 dioptres. Accommodation decreased by about 0.5 dioptre after instillation of 5 × 5 μl 10% phenylephrine. The cycloplegic effects of 0.2% and 1% cyclopentolate were similar. Accommodation was also determined after application of 5 μl 1% cyclopentolate followed by either 5 × 5 μl 0.5% thymoxamine or 10% phenylephrine. Addition of thymoxamine did not alter the cycloplegic response of cyclopentolate alone. Addition of phenylephrine caused a more prolonged but similar maximum response compared to that of cyclopentolate alone. In the 6 other test subjects, the accommodation was compared before and after topical instillation of 5 μl of 0.2% and 1% and 40 μl (one standard eye‐drop) of 1% cyclopentolate and followed during 6 h. There was no difference between the maximum value of 5 μl and 40 μl 1% cyclopentolate. We conclude from these data that alpha‐stimulation by phenylephrine decreases and alpha‐inhibition by thymoxamine increases the accommodative amplitude in man. Furthermore, the results indicate that a smaller drop volume or weaker solution of cyclopentolate than routinely used in clinical practice produces a similar cycloplegic effect.