We have located links that may give you full text access.
COMPARATIVE STUDY
JOURNAL ARTICLE
Measurement centration and zone diameter in anterior, posterior and total corneal astigmatism in keratoconus.
Acta Ophthalmologica 2017 December
PURPOSE: To investigate the central and paracentral astigmatism and the significance of centration and measurement zone diameter compared to a 3-mm pupil-centred measurement zone in keratoconus and in healthy eyes.
METHODS: Twenty-eight right eyes from 28 KC patients with an inferotemporal cone were selected according to specified criteria based on Oculus Pentacam HR® measurements and were matched with healthy control eyes. The flat (K1) and steep (K2) keratometry readings were registered from the 'Total Corneal Refractive Power' (TCRP) display as well as the anterior and posterior corneal astigmatism displays (ACA and PCA, respectively). Astigmatic power vectors KP0 and KP45 were calculated and analysed for a 6-mm and two 3-mm zones centred on the corneal apex and the pupil, and for 8 paracentral 3-mm zones.
RESULTS: The astigmatism was generally higher in KC. Many astigmatic values in KC differed between the 3-mm pupil-centred and the 3- and 6-mm apex-centred zones in KC. In the controls, no corresponding differences between measurement zones were seen, apart from PCA, which differed. The magnitude and direction of KP0 and KP45 varied greatly between the paracentral measurements in KC.
CONCLUSION: Centration and measurement zone diameter have great impacts on the astigmatic values in KC. A small pupil-centred measurement zone should be considered when evaluating the astigmatism in KC.
METHODS: Twenty-eight right eyes from 28 KC patients with an inferotemporal cone were selected according to specified criteria based on Oculus Pentacam HR® measurements and were matched with healthy control eyes. The flat (K1) and steep (K2) keratometry readings were registered from the 'Total Corneal Refractive Power' (TCRP) display as well as the anterior and posterior corneal astigmatism displays (ACA and PCA, respectively). Astigmatic power vectors KP0 and KP45 were calculated and analysed for a 6-mm and two 3-mm zones centred on the corneal apex and the pupil, and for 8 paracentral 3-mm zones.
RESULTS: The astigmatism was generally higher in KC. Many astigmatic values in KC differed between the 3-mm pupil-centred and the 3- and 6-mm apex-centred zones in KC. In the controls, no corresponding differences between measurement zones were seen, apart from PCA, which differed. The magnitude and direction of KP0 and KP45 varied greatly between the paracentral measurements in KC.
CONCLUSION: Centration and measurement zone diameter have great impacts on the astigmatic values in KC. A small pupil-centred measurement zone should be considered when evaluating the astigmatism in KC.
Full text links
Related Resources
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app