Accuracy of Goldmann tonometry after refractive surgery

Area of Science:

• Ophthalmology
• Refractive Surgery
• Ocular Biomechanics

Background:

• Goldmann tonometry is a standard method for measuring intraocular pressure (IOP).
• Refractive surgeries like radial keratotomy (RK) and photorefractive keratectomy (PRK) alter corneal biomechanics.
• The impact of these corneal changes on Goldmann tonometer accuracy is not fully understood.

Purpose of the Study:

• To evaluate the accuracy of Goldmann tonometry in measuring intraocular pressure (IOP) after refractive surgery.
• To determine if refractive surgery techniques (RK and PRK) affect IOP measurements obtained by Goldmann tonometry.

Main Methods:

• Retrospective chart review of 824 radial keratotomy (RK) and 415 photorefractive keratectomy (PRK) patients.
• Analysis included 306 RK and 168 PRK patients with at least 4 weeks of discontinued steroid use post-surgery.
• Preoperative and postoperative intraocular pressure (IOP) measurements were compared using Goldmann tonometry.

Main Results:

• Goldmann tonometer measurements showed a statistically significant decrease in IOP after both RK (mean decrease 1.0 mm Hg) and PRK (mean decrease 2.4 mm Hg).
• Older age and male gender were associated with a greater reduction in measured IOP post-surgery.
• No correlation was found between IOP changes and specific corneal parameters or operative details.

Conclusions:

• Refractive surgery significantly impacts the accuracy of Goldmann tonometry, causing it to underestimate intraocular pressure (IOP).
• The underestimation of IOP is more pronounced in older male patients who have undergone photorefractive keratectomy (PRK).
• These findings highlight the need for caution when interpreting Goldmann tonometer readings in patients with a history of refractive surgery.