Comparison of the Effects of Bright Light, Phenylephrine 2.5%, Tropicamide 1%, and Pilocarpine 2% on Anterior Chamber Depth and IOL Power
Narrative Responses:
Purpose
To evaluate and compare the effect of bright light, phenylephrine, tropicamide and pilocarpine on the anterior chamber depth (ACD), and anterior chamber intraocular lens (ACIOL) and posterior chamber intraocular lens (PCIOL) power.
Methods
20 healthy volunteers with a mean age of 35.8 years participated in this single center, prospective and comparative study. The IOL Master was used to measure the ACD, and the Holladay formula was used to calculate the ACIOL and PCIOL power in all eyes. The Alcon Acrysof IQ SN60WF PCIOL and MTA 4UO ACIOL models were chosen for comparison of intraocular lens power in all subjects. The measurements were done in scotopic condition, in bright light, and 30 minutes following instillation of 2.5 % phenylephrine, 1 % tropicamide and 2 % pilocarpine drops in scotopic condition on separate days.
Results
40 eyes of 7 males and 13 females were analyzed. 16 eyes were emmetropic, 18 were myopic and 6 were hyperopic Bright light and pilocarpine decreased the ACD statistically significantly (P=0.004, P<1E-04 respectively), whereas phenylephrine and tropicamide increased the ACD statistically significantly (P=0.002, P<1E-04).
Compared to scotopic condition, PCIOL power did not change significantly in bright light (P=0.38), or following phenylephrine (P=0.29), and tropicamide (P=0.22), but changed statistically significantly following pilocarpine (P=0.01). ACIOL power calculated in bright light (P=0.16), or following phenylephrine (P=0.39), tropicamide (P=0.39) and pilocarpine (P=0.17) was not statistically different from ACIOL power in scotopic condition.
Conclusion
ACD changes significantly in bright light, and following 2.5% phenylephrine, 1% tropicamide and 2% pilocarpine. The selection of IOL power remains clinically unaffected for most models manufactured in incremental power of 0.50 diopters. Howeve, pilocarpine may affect the PCIOL power selection for models available in smaller increment of 0.25 diopters.