Tonometry after Intrastromal Corneal Ring Segments for Keratoconus

Area of Science:

• Ophthalmology
• Corneal Surgery
• Ophthalmic Diagnostics

Background:

• Intrastromal corneal ring segments (ICRS) alter corneal morphology, challenging reliable intraocular pressure (IOP) measurement.
• Accurate IOP assessment is vital for managing conditions like corneal ectasia post-ICRS implantation.

Purpose of the Study:

• To compare IOP measurements from different tonometers against Goldmann applanation tonometry (GAT) in patients with ICRS.
• To evaluate the influence of central corneal thickness (CCT), corneal curvature, and astigmatism on IOP readings after ICRS.

Main Methods:

• Cross-sectional study involving 91 eyes of 91 patients previously implanted with ICRS.
• IOP measured using TonoPen XL, Pascal dynamic contour tonometer (DCT), and iCare Pro, with GAT as the reference.
• Statistical analysis included Bland-Altman method, intraclass correlation coefficients, and multiple linear regression.

Main Results:

• Mean IOP differences (GAT vs. tonometer): TonoPen XL (-0.8 ± 3.07 mmHg), DCT (-1.0 ± 3.26 mmHg), iCare Pro (0.8 ± 2.92 mmHg).
• Central corneal thickness (CCT) was identified as a confounding factor for all tonometers except DCT.
• DCT-IOP measurements were not affected by corneal topographic factors.

Conclusions:

• The iCare Pro and TonoPen XL showed the highest agreement with GAT for IOP measurement in ICRS patients.
• The dynamic contour tonometer (DCT) provided IOP readings unaffected by corneal parameters but tended to overestimate GAT values.