Question

Enumerate a few tonometers. Which one is preferred in altered corneal surface conditions?

Hint:

In patients with altered corneal surfaces, the Tono-Pen or Rebound Tonometer can provide more accurate IOP measurements.

Answer 1

Step 1: Types of Tonometers.
There are several tonometers used to measure intraocular pressure (IOP), including:
1. Goldmann Applanation Tonometer: This is the most commonly used and considered the gold standard for measuring IOP. It works by flattening a small area of the cornea and measuring the force required to do so.
2. Non-Contact Tonometer (NCT): Also known as the "air puff" tonometer, it measures IOP by sending a puff of air onto the cornea and measuring the corneal response. It is non-invasive and does not require contact with the eye.
3. Tono-Pen: This is a handheld device that uses applanation to measure IOP. It is particularly useful for measuring IOP in patients with irregular corneal surfaces or when other tonometers are impractical.
4. Rebound Tonometer: A small probe is used to make brief contact with the cornea, and the IOP is estimated based on the rebound velocity of the probe.

Step 2: Preferred Tonometer in Altered Corneal Surface Conditions.
In patients with altered corneal surfaces (e.g., following surgery, corneal disease, or irregular corneas), the Tono-Pen or Rebound Tonometer is often preferred. These tonometers are more adaptable to irregular corneal surfaces and provide accurate IOP readings even when the cornea is not perfectly flat.

Step 3: Conclusion.
In cases of altered corneal surface conditions, tonometers that require less precise corneal alignment, such as the Tono-Pen or Rebound Tonometer, are preferred over the Goldmann Applanation Tonometer.