Using the rebound tonometer to measure intraocular pressure in an anesthetized patient.

Dear Editor,

iCare tonometer, a rebound tonometer, is designed to measure intraocular pressure (“IOP”) with minimal need for topical anesthesia.[1] The iCare tonometer has been used in children and home screening.[2] However, because the probe of the tonometer is gravity-dependent, it cannot be used validly in an individual who is in a supine position, as the probe, due to gravity, falls and does not rebound [Fig. 1a and b]. We describe a technique to measure IOP with the iCare tonometer in the supine position. This would be helpful in examination under anesthesia children and patients who can sit upright.

Figure 1

(a and b) Shows the fall of probe from the tonometer because of gravity. (c) The tonometer can be used easily since the probe is horizontal and would not fall due to gravity

The Technique

Placing an anesthetized person in an upright position carries the risk of the tongue blocking the airway, causing hypoxia. This particular risk can be avoided when patients are placed on their side. The technique is as follows: The patient is laid on one side, and the tonometer appropriately tilted to that side (as shown in the [Video 1] and Fig. 1c). The pressure can then be measured. The particular modification is safe for children taken for examination under anesthesia and gives a quick and reliable multiple readings. A similar technique has been used for ND YAG capsulotomy in children under general anesthesia.[3] It also doesn’t require a higher end equipment (the iCare pro), which is expensive compared to the I care model.