1. A head mounted display, comprising:a casing fixed to a light guide portion, wherein
the casing includes a first casing portion and a second casing portion attached to the first casing portion,
the first casing portion comprises an inner side surface of the casing,
the inner side surface of the casing is a user side,
the second casing portion comprises an outer side surface of the casing, and
the first casing portion is removably attached to the second casing portion;
a heat source within the casing, wherein the heat source is supported by the first casing portion; and
a deformable heat-transfer member housed within the casing, wherein the deformable heat-transfer member comprises a first end and a second end, and wherein the first end is connected to the heat source and the second end is connected to an inner surface of the second casing portion.