Investigations in BCS. (a) Ocular optical coherence tomography (OCT) and pachymetry of a 32 year old patient with homozygous mutation in PRDM5 (deletion of exons 11–16; IV:4 of family BCS-001, Burkitt Wright et al. ). Note extreme thinning, particularly of the central cornea (300 μm) but even the maximum thickness at the periphery is only 330–380 μm. (b) Ocular OCT and pachymetry of a 31 year old patient with heterozygous mutation in PRDM5 (IV:8, BCS-001). Note only mild corneal thinning on OCT, with mean CCT measurement of 480 μm, increasing to 580–620 μm at the periphery. (c) Ocular OCT and pachymetry of a normal eye for comparison with a) and b), showing CCT of 580 μm and peripheral thickness of 650–750 μm. (d) Tympanogram of BCS patient (IV:4, BCS-001): a Type Ad curve is observed, demonstrating normal middle ear pressure but hypercompliance of the tympanic membrane. The volume by which the eardrum is displaced when a pulse of pressure is delivered to it is represented by the curve (~3.5 cm3), whilst the marker on the left demonstrates the degree of compliance observed (~1 cm3) for a normal tympanic membrane.