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Ocular rigidity and intraocular pressure in keratoconus
Australian Journal of Ophthalmology
|November 1, 1984
Summary
Keratoconus is linked to reduced ocular rigidity and corneal thinning, affecting intraocular pressure measurements. Mackay-Marg tonometry offers a more accurate pressure reading in these cases.
Area of Science:
- Ophthalmology
- Corneal biomechanics
- Ocular physiology
Background:
- Keratoconus is a progressive thinning of the cornea, leading to irregular astigmatism.
- Understanding ocular biomechanics is crucial for accurate intraocular pressure (IOP) assessment in keratoconus patients.
Purpose of the Study:
- To investigate the relationship between ocular rigidity, corneal biomechanics, and intraocular pressure measurements in keratoconus.
- To evaluate the accuracy of different tonometry methods in keratoconus.
Main Methods:
- Studied 85 keratoconus patients and 20 controls.
- Measured ocular rigidity using the Friedenwald nomogram.
- Assessed intraocular pressure with Schiøtz and Goldmann applanation tonometry, and Mackay-Marg tonometry.
Main Results:
- Ocular rigidity correlated significantly with corneal thinning (p < 0.001) and cone area (p = 0.05).
- Goldmann applanation pressures were falsely low over the cone apex, especially with reduced ocular rigidity and corneal thinning.
- Mackay-Marg tonometry provided more accurate IOP readings in keratoconus patients.
Conclusions:
- Abnormal corneal rigidity is the primary factor influencing ocular rigidity and tonometry results in keratoconus.
- Goldmann applanation tonometry is unreliable in keratoconus due to corneal thinning and altered rigidity.
- Mackay-Marg tonometry is a more reliable method for IOP measurement in keratoconus.
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