Clinical Techniques
Goldmann Tonometry
Unlock FRCOphth Part 1 Study Notes to access this content.
Get accessSummary Table: causes of erroneous IOP readings on Goldmann
| Falsely low | Falsely high |
| Corneal oedema | High CCT |
| Low CCT | Digital pressure |
| Previous refractive surgery | Corneal scar |
| Too little fluorescein | Too much fluorescein |
| >3D with-the-rule astigmatism | >3D against-the-rule astigmatism |
| High myopia |
Principles
- Based on Imbert-Fick principle
- P=F/A
Force of application is directly proportional to the intraocular pressure when the area of applanation equals 3.06mm
- This area of contact occurs when the mires are aligned at their inner margins
At this area, the additional forces of corneal rigidity and surface tension are balanced
The tonometer scale is in “dynes” so is multiplied by ten to give an IOP in mmHg
Prisms are used in the tonometer head to split the operator’s view of the tear meniscus stained with fluorescein, to allow precise adjustment
Hot Topic
Hot topic: Goldmann relies on the false assumption that there is little variability between human eyes in terms of corneal thickness and rigidity