  This work presents a study of two Herbig Ae transitional discs, Oph IRS 48
and HD 169142; which both have reported rings in their dust density
distributions. We use Keck-II/NIRC2 adaptive optics imaging observations in the
L' filter (3.8 micron) to probe the regions of these discs inwards of ~20AU
from the star. We introduce our method for investigating these transitional
discs, which takes a forward modelling approach: making a model of the disc
(using the Monte Carlo radiative transfer code RADMC), convolving it with
point-spread functions of calibrator stars, and comparing the convolved models
with the observational data. The disc surface density parameters are explored
with a Monte Carlo Markov Chain technique. Our analysis recovers emission from
both of the discs interior to the well known optically thick walls, modelled as
a ring of emission at ~15AU in Oph IRS 48, and ~7AU for HD 169142, and
identifies asymmetries in both discs. Given the brightness of the
near-symmetric rings compared to the reported companion candidates, we suggest
that the reported companion candidates can be interpreted as slightly
asymmetric disc emission or illumination.
