IOVS Journal of Clinical Investigation
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(Investigative Ophthalmology and Visual Science. 2001;42:1581-1585.)
© 2001 by The Association for Research in Vision and Ophthalmology, Inc.

Evaluation of Potentiating Effect of a Drop of Lignocaine on Tropicamide-Induced Mydriasis

Supriyo Ghose1, Vinay Kumar Garodia1, Mahipal Singh Sachdev1, Harsh Kumar1, Nihar Ranjan Biswas2 and Ravindra Mohan Pandey3

1 From the Dr. Rajendra Prasad Centre for Ophthalmic Sciences, and the 2 Division of Ocular Pharmacology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences (AIIMS); and the 3 Department of Biostatistics, AIIMS, Ansari Nagar, New Delhi, India.

PURPOSE. To analyze whether preinstillation of lignocaine potentiates mydriasis by tropicamide in dark eyes and to determine possible mechanisms for this effect.

METHODS. This investigation was conducted in two phases, the first being a double-masked, placebo-controlled, randomized clinical trial, enrolling 60 healthy dark brown eyes in 30 subjects aged 7 to 58 years. The control eye received a drop of (nonlignocaine) placebo before tropicamide 1%, and the contralateral study eye received a 4% lignocaine drop 3-minutes before the 1 drop of tropicamide was administered. A ruled pupillometer recorded pupil diameters every 10 minutes for 50 minutes. In phase II, to elucidate pathomechanisms after lignocaine, corneal and tear parameters were compared with baseline records in a further 60 such eyes.

RESULTS. Pupillary diameters in the study eyes increased by 3.62 ± 0.75 mm, significantly more than in the placebo (control) group (P = 0.000). Ninety percent of study eyes attained the clinically significant 6-mm size with preinstillation of lignocaine—many more than the 67% of control eyes (P = 0.016). The median time to achieve this critical 6-mm size was significantly faster in the study group (P = 0.005). In phase II, the 1 drop 4% lignocaine did not show corneal changes with slit lamp or fluorescein staining and did not reduce media clarity or induce a significant change in tear pH. It markedly decreased Schirmer values (P = 0.000), reduced tear break-up time (P = 0.003), and increased corneal thickness measured by optical pachymetry (P = 0.010).

CONCLUSIONS. The phase II findings indicate corneal microepithelial damage and reduced tearing. Both may enhance intraocular penetration and hence potentiation of tropicamide. This remarkable phenomenon could find use with many other important topical medications.






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