Pupil response to tropicamide following laser in situ keratomileusis.
OBJECTIVE
To investigate the effect of corneal thinning after laser in situ keratomileusis (LASIK) on the corneal penetration of topical eye medication.


METHODS
Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.


METHODS
Laser in situ keratomileusis surgery was performed in 19 eyes of 10 patients enrolled in this prospective study. Measurements were made before surgery and 3 months postoperatively. After instillation of tropicamide 1%, the change in pupil size over time was measured with a Colvard pupillometer. Central corneal thickness (CCT) was measured with ultrasonic pachymetry before and 3 months after LASIK. The corneal epithelial condition was also examined by fluorescein dye staining.


RESULTS
The mean CCT decreased significantly from 564 microm +/- 33 (SD) before LASIK surgery to 514 +/- 48 microm 3 months postoperatively (P<.0001). Pupil diameter 10, 15, and 20 minutes after tropicamide 1% instillation was significantly larger 3 months after surgery than preoperatively (P=.0083, P=.0043, and P=.0144, respectively). The mean time to reach a pupil diameter of 6.0 mm decreased significantly from 14.4 +/- 4.3 minutes in preoperative eyes to 11.5 +/- 2.3 minutes in postoperative eyes (P=.0281). Mild punctate corneal epithelial staining (fewer than 5 spots) were observed in 4 eyes at the 3-month postoperative examination.


CONCLUSIONS
Pupil dilation after tropicamide 1% instillation was significantly faster after LASIK surgery. Corneal thinning that resulted from LASIK enhanced corneal penetration of tropicamide 1%.
Chung
Hak Sung
HS
Department of Ophthalmology, Feinberg School of Medicine/Northwestern University, Chicago, Illinois 60611, USA.
Feder
Robert S
RS
D000328:Adult; D001837:Body Weights and Measures; D003315:Cornea / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D003319:Corneal Stroma / Q000378:metabolism / Q000473:pathology; D019573:Epithelium, Corneal / Q000378:metabolism / Q000473:pathology; D005260:Female; D015590:Fluorophotometry; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D009184:Mydriatics / Q000493:pharmacokinetics*; D010539:Permeability; D011446:Prospective Studies; D011680:Pupil / Q000187:drug effects / Q000502:physiology*; D014331:Tropicamide / Q000493:pharmacokinetics*
D009184:Mydriatics; D014331:Tropicamide