An ophthalmic surgical system includes at least one light source. The light source is configured to output light towards a fluidics cassette so a first portion of the light reflects from a deflectable diaphragm of the fluidics cassette, and a second portion of the light reflects from a reference portion of the fluidics cassette. The diaphragm is configured to deflect relative to the reference portion in response to a pressure associated with a fluid within the fluidics cassette. At least one sensor is configured to receive the first portion of the light reflected from the diaphragm and the second portion of the light reflected from the reference portion. A computing device in communication with the sensor is configured to determine the pressure associated with the fluid within the fluidics cassette based on the received first and second portions of the light. Associated devices, systems, and methods are also disclosed.
