Abstract
Purpose::
To quantify the diffusion of albumin across human sclera and to assess topographical and age-related variation.
Methods::
Equatorial superotemporal scleral tissue from 15 donor eyes (mean age 60 years, range 39-84 years) were mounted in a modified Ussing chamber. Additional tissue was taken from the anterior and posterior superotemporal regions of 6 eyes, and equatorial superonasal, and inferotemporal regions of a further 6 eyes. Fluorescein isothiocyanate (FITC) labeled, 0.412 mMol, bovine albumin was placed in one hemi-chamber facing the internal scleral surface, and the rate of trans-scleral diffusion was determined over 24 hours, at 25oC, with a spectrophotometer.
Results::
Mean diffusion for equatorial superotemporal scleral tissue +/- 1SD was 12.35 +/- 7.12 pmoles/hour/mm2. There was no significant difference in diffusion over the different topographical regions tested. The effect of donor age was assessed for the fifteen equatorial superotemporal samples. Regression analysis showed a significant decline in scleral diffusion of albumin with increasing donor age (p=0.0166).
Conclusions::
The study of normal scleral physiology may guide strategies for trans-scleral drug delivery and help understand disease states characterised by abnormal trans-scleral diffusion. The above results quantify trans-scleral diffusion of albumin and assesses its relationship with topographical location and donor age. The decrease in albumin permeability with increasing donor age may have pharmacokinetic implications.
Keywords: sclera • aging • anatomy