Related Experiment Video
Updated: Oct 17, 2025
05:14
Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter
Published on: September 16, 2025
168
Correlation Between Keratometric and Refractive Astigmatism in Pseudophakes.
Shavini Athukorala1, Neal Kansara2, Erik Lehman3
1Department of Ophthalmology, Penn State College of Medicine, Hershey, PA, USA.
Clinical Ophthalmology (Auckland, N.Z.)
|October 6, 2021
Summary
Total keratometric astigmatism (TK) measured by swept-source optical coherence tomography (SS-OCT) best predicts post-operative refractive astigmatism after cataract surgery. Posterior corneal astigmatism does not fully explain refractive astigmatism differences.
Area of Science:
- Ophthalmology
- Corneal Physiology
- Refractive Surgery
Background:
- Accurate prediction of post-operative refractive astigmatism is crucial for successful cataract surgery outcomes.
- Keratometric astigmatism measurements are commonly used, but their correlation with actual refractive outcomes can vary.
Purpose of the Study:
- To evaluate the relationship between different measures of keratometric astigmatism (anterior, posterior, total) and post-operative refractive astigmatism (RA) following cataract surgery.
- To determine which keratometric measurement method most accurately predicts refractive astigmatism after surgery.
Main Methods:
- Retrospective analysis of 118 eyes undergoing cataract surgery with monofocal intraocular lens implantation.
- Pre-operative keratometric astigmatism was measured using swept-source optical coherence tomography (SS-OCT) and a dual-Scheimpflug/Placido disc topographer.
- Differences between post-operative refractive astigmatism and various keratometric measurements (K, SimK, TK, TCP) were calculated.
Main Results:
- Total Keratometry (TK) showed a significantly smaller vector difference with post-operative refractive astigmatism (0.08 @ 151) compared to Total Corneal Power (TCP) (0.30 @ 174) and Simulated Keratometry (SimK) (0.52 @ 177).
- The vector difference between TK and refractive astigmatism varied based on anterior corneal astigmatism orientation (ATR, oblique, WTR), with p < 0.0006.
- Posterior corneal astigmatism did not significantly correlate with the orientation of anterior corneal astigmatism (p = 0.58).
Conclusions:
- Total keratometric astigmatism (TK) derived from SS-OCT is the most reliable predictor of post-operative refractive astigmatism after cataract surgery.
- The discrepancy between anterior corneal astigmatism and refractive astigmatism is not solely due to posterior corneal contributions.
- Other factors like lens tilt or neuro-adaptation may influence the final refractive outcome.
Related Concept Videos
01:16Focusing of Light in the Eye
3.5K
Light rays enter the eye through the cornea, a transparent dome-shaped tissue that is the eye's outermost layer. The cornea bends or refracts, light rays traveling to the pupil. The shape of the cornea determines how much of the light is bent and whether the image will be focused correctly on the retina at the back of the eye. Once the light has passed through both refraction layers, it converges into a single focal point onto a small area. This is where photoreceptors start transforming...
3.5K
01:26Influence of Earth's Curvature and Atmospheric Refraction on Leveling
351
During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference. When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:This relationship shows that the deviation increases quadratically with distance.
351