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Repeatability of corneal elevation maps in keratoconus patients using the tomography matching method
YaRu Zheng1, LiFang Huang1,2, YiPing Zhao1
1Eye Hospital, Wenzhou Medical University, Wenzhou, 325027, China.
Keratoconus (KC) corneas show greater misalignment and lower repeatability in successive tomography scans compared to healthy eyes. These errors, particularly affecting astigmatism measurements, correlate with keratoconus progression.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Corneal Imaging
Background:
- Corneal tomography is crucial for diagnosing and monitoring keratoconus (KC).
- Assessing the repeatability of successive measurements is vital for reliable clinical assessment.
- The Iterative Closest Point (ICP) algorithm offers a method to quantify measurement alignment and repeatability.
Purpose of the Study:
- To evaluate the repeatability of successive Pentacam corneal tomography measurements in keratoconus (KC) and normal eyes.
- To quantify measurement misalignment using the ICP algorithm and assess its impact on corneal curvature parameters.
- To investigate the correlation between measurement errors and keratoconus severity.
Main Methods:
- The study included 143 KC eyes and 143 matched normal eyes.
- The ICP algorithm was employed to calculate misalignment parameters, including pre- (PreICP-RMS) and post-tomography matching (PosICP-RMS) elevation data differences.
- Power vector analysis (M, J0, J45) was used to assess the effect of misalignment on keratometry and astigmatism.
Main Results:
- Both PreICP-RMS and PosICP-RMS were significantly higher in KC eyes compared to normal eyes (P < 0.01).
- Combined misalignment (CM) increased significantly more in KC eyes (16.76 ± 20.88 μm) than in normal eyes (5.43 ± 4.08 μm).
- Misalignment parameters (PreICP-RMS, PosICP-RMS, CM) correlated with keratoconus grade (P < 0.05), and astigmatism (J0) measurements were significantly affected by misalignment.
Conclusions:
- Keratoconus corneas exhibit greater misalignment and reduced repeatability in serial tomography measurements compared to healthy eyes.
- Measurement misalignment significantly influences the accuracy of astigmatism estimation, more so than spherical curvature.
- Increased measurement errors in KC eyes appear to be associated with disease progression, highlighting the importance of considering alignment in KC monitoring.
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