Abstract
Purpose :
Topical anaesthesia has many potential benefits over subcutaneous infiltration of local anaesthetics for surgery on human skin. Commercial preparations providing local anaesthesia following application to the skin are available but none are routinely used on the eyelid despite a clear clinical need and it is not known whether they can provide sufficient delivery of the anaesthetic agent for surgical procedures such as blepharoplasty. Eyelid skin is commonly believed to be more permeable than skin from other body regions though published evidence supporting this assumption is limited. This work aimed to assess the permeability of lidocaine through human eyelid skin and compare this to published results for abdominal skin to provide insight into the potential of developing a topical anaesthetic product suitable for use in eyelid surgery.
Methods :
Superficial corneocyte area and stratum corneum (SC) thickness were measured using a light microscope to provide understanding of the barrier properties of eyelid skin. Saturated suspensions of lidocaine at pH 7.0 and pH 5.5 were used to evaluate the permeability of eyelid skin in vitro using Franz diffusion cells.
Results :
Steady-state fluxes of lidocaine at pH 7.0 (283.9±116.4 μg/cm2/h) and pH5.5 (64.7±28.1 μg/cm2/h) were 2.4 and 3.1 times respectively greater than literature values for abdominal skin obtained at the same pH. Superficial eyelid corneocyte area (800.47±13.7 μm2) was 35 % smaller and the eyelid SC thickness (14.86±2.93 μm) was 31 % thinner than reported abdominal skin values.
Conclusions :
The increased lidocaine permeation across eyelid skin may be associated with a shorter diffusional pathlength across eyelid stratum corneum. Our results highlight the potential of achieving strong local anaesthetic effects at the eyelid following topical application and possible increases in absorption of other drug molecules applied to the eyelid in the management of conditions such as atopic dermatitis and rosacea.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.