Measuring the axial length of the eye
A-scan and B-scan: These techniques can measure the distance between the anterior and posterior poles of the eye by using ultrasonic waves. After the eye is numbed with anaesthetic drops, the ultrasound wand (transducer) can be placed directly against the front surface of the eye or on the eyelid. A-scan is a part of the preoperative evaluation procedurein cataract, because before surgery the axial length of the eye should be identified carefully tocalculatethe parameters of needed intraocular lens.B-scan is done to look carefully at the inside part of the eye or the internal structure of the eye in cases where they are hidden from the ophthalmologist. This may occur when you have cataracts or other conditions such asvitreous haemorrhage or tumours that make it hard for the doctor to see into the back of the eye. These actions are performed by usingdevices such as Vumax. IOL- Masteris a new generation device which can measure the length of the eye, the curvature of the cornea, and anterior chamber depth in just 1 minute without contacting the eyes, therefore it doesn't need anaesthesia and also there is no risk of contact with ophthalmic devices.