An ophthalmic apparatus comprising: a housing defining a cassette receptacle; a sensor arrangement in operative communication with the cassette receptacle; and a cassette configured to operatively engage the cassette receptacle for establishing operative communication between the cassette and the sensor arrangement, the cassette comprising: a cassette body configured to engage the cassette receptacle, wherein the cassette body defines a storage receptacle (112/114); a manifold defining an inlet port in fluid flow communication with a fluid pathway (120/122); and a storage chamber (116/118) in selective fluid flow communication with the fluid pathway (120/122) when the storage chamber (116/118) is engaged to the storage receptacle (112/114) of the cassette body; characterised in that the sensor arrangement is operatively associated with t cassette engaged to the cassette receptacle for transmitting a detection signal (129/131) to detect: a first state wherein the storage chamber (116/118) is detached from the storage receptacle (112/114), a second state wherein the storage chamber (116/118) is attached to the storage receptacle (112/114) and the sensor arrangement detects only air in the storage chamber (116/118), and a third state wherein a liquid fills the storage chamber (116/118) attached to the storage receptacle (112/114) above a predetermined level. a housing defining a cassette receptacle; a sensor arrangement in operative communication with the cassette receptacle; and a cassette configured to operatively engage the cassette receptacle for establishing operative communication between the cassette and the sensor arrangement, the cassette comprising: a cassette body configured to engage the cassette receptacle, wherein the cassette body defines a storage receptacle (112/114); a manifold defining an inlet port in fluid flow communication with a fluid pathway (120/122); and a storage chamber (116/118) in selective fluid flow communication with the fluid pathway (120/122) when the storage chamber (116/118) is engaged to the storage receptacle (112/114) of the cassette body; a cassette body configured to engage the cassette receptacle, wherein the cassette body defines a storage receptacle (112/114); a manifold defining an inlet port in fluid flow communication with a fluid pathway (120/122); and a storage chamber (116/118) in selective fluid flow communication with the fluid pathway (120/122) when the storage chamber (116/118) is engaged to the storage receptacle (112/114) of the cassette body; characterised in that the sensor arrangement is operatively associated with t cassette engaged to the cassette receptacle for transmitting a detection signal (129/131) to detect: a first state wherein the storage chamber (116/118) is detached from the storage receptacle (112/114), a second state wherein the storage chamber (116/118) is attached to the storage receptacle (112/114) and the sensor arrangement detects only air in the storage chamber (116/118), and a third state wherein a liquid fills the storage chamber (116/118) attached to the storage receptacle (112/114) above a predetermined level. a first state wherein the storage chamber (116/118) is detached from the storage receptacle (112/114), a second state wherein the storage chamber (116/118) is attached to the storage receptacle (112/114) and the sensor arrangement detects only air in the storage chamber (116/118), and a third state wherein a liquid fills the storage chamber (116/118) attached to the storage receptacle (112/114) above a predetermined level.