Ocular rigidity and intraocular pressure in keratoconus.

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.