An ophthalmic surgical system, comprising: at least one light source (252, 253) configured to output light towards a fluidics cassette in a manner that a first portion of the light reflects from a deflectable diaphragm of the fluidics cassette, and in a manner that a second portion of the light reflects from a reference portion (350, 314) of the fluidics cassette, wherein the diaphragm is configured to deflect relative to the reference portion in response to a pressure associated with a first fluid within the fluidics cassette; at least one sensor (254, 255) 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 (314, 350); and a computing device in communication with the at least one sensor, the computing device configured to determine the pressure associated with the first fluid within the fluidics cassette based on the received first and second portions of the light, and characterized in that: the at least one light source (252, 253) is configured to output light towards the fluidics cassette such that a third portion of the light reflects from a second diaphragm of the fluidics cassette and a fourth portion of the light reflects from a second reference portion (314, 350) of the fluidics cassette, wherein the second diaphragm is configured to be deflected in response to a pressure associated with a second fluid within the fluidics cassette; the at least one sensor (254, 255) further configured to receive the third portion of the light reflected from the second diaphragm and the fourth portion of the light reflected from the second reference portion; and the computing device is configured to determine the pressure associated with the second fluid within the fluidics cassette based on the received third and fourth portions of the light. at least one light source (252, 253) configured to output light towards a fluidics cassette in a manner that a first portion of the light reflects from a deflectable diaphragm of the fluidics cassette, and in a manner that a second portion of the light reflects from a reference portion (350, 314) of the fluidics cassette, wherein the diaphragm is configured to deflect relative to the reference portion in response to a pressure associated with a first fluid within the fluidics cassette; at least one sensor (254, 255) 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 (314, 350); and a computing device in communication with the at least one sensor, the computing device configured to determine the pressure associated with the first fluid within the fluidics cassette based on the received first and second portions of the light, and characterized in that: the at least one light source (252, 253) is configured to output light towards the fluidics cassette such that a third portion of the light reflects from a second diaphragm of the fluidics cassette and a fourth portion of the light reflects from a second reference portion (314, 350) of the fluidics cassette, wherein the second diaphragm is configured to be deflected in response to a pressure associated with a second fluid within the fluidics cassette; the at least one sensor (254, 255) further configured to receive the third portion of the light reflected from the second diaphragm and the fourth portion of the light reflected from the second reference portion; and the computing device is configured to determine the pressure associated with the second fluid within the fluidics cassette based on the received third and fourth portions of the light. the at least one light source (252, 253) is configured to output light towards the fluidics cassette such that a third portion of the light reflects from a second diaphragm of the fluidics cassette and a fourth portion of the light reflects from a second reference portion (314, 350) of the fluidics cassette, wherein the second diaphragm is configured to be deflected in response to a pressure associated with a second fluid within the fluidics cassette; the at least one sensor (254, 255) further configured to receive the third portion of the light reflected from the second diaphragm and the fourth portion of the light reflected from the second reference portion; and the computing device is configured to determine the pressure associated with the second fluid within the fluidics cassette based on the received third and fourth portions of the light.