Pupillary dilation and axial length measurement for preoperative assessment of intraocular lens power.

Cataract extraction is now routinely followed by insertion of an intraocular lens (IOL) which requires preoperative biometry to determine the most accurate implant power required. Biometry is generally performed just prior to surgery and may even require the patient to make a special hospital visit when day case surgery is contemplated. A prospective study was undertaken to determine the accuracy of axial length (AL) measurement through a dilated pupil. The AL of one eye of 64 patients admitted for cataract surgery was measured before and after dilation with a drop of tropicamide 1%. Our results show that there was no significant difference in the ALs before and after dilation (p = 0.10), and neither was there a difference in the average range of measurements (p = 0.70), with 78% of eyes having a difference of < +/- 0.3 mm between pre and post dilation ALs. We conclude that AL measurement performed on a dilated pupil can give an accurate result, and suggest that performing biometry on a dilated pupil following ocular assessment may be an efficient and time saving exercise.