The invention concerns an observation device such as cell culture wells comprising an optical element such as a lens or a filter, or even combinations thereof, for compensating an optical effect induced on a sample contained in the observation device and illuminated by a light beam traversing a meniscus. The interaction of a light beam with a meniscus interposed between said light beam and a sample to be visualized, alters the image readout of the sample so that the image thereof results negatively affected. By aligning the optical axis of the optical element with that of the meniscus, an optical effect such as non-uniform light distribution of illumination of the sample can be conveniently compensated. The invention further discloses the optical elements, characterising the observation device, per se.