Corneal refractive power and symmetry changes following normalization of ectasias treated with partial topography-guided PTK combined with higher-fluence CXL (the Athens Protocol).

Abstract

PURPOSE:

To investigate preoperative and postoperative anterior and posterior keratometry and simulated corneal astigmatism in keratoconic eyes treated with collagen cross-linking combined with anterior surface normalization by partial topography-guided excimer ablation (the Athens Protocol).

METHODS:

Anterior and posterior corneal keratometry were measured by Scheimpflug imaging for 267 untreated keratoconic eyes. Following treatment, they were assessed 1 year postoperatively.

RESULTS:

Before treatment, average anterior keratometric value was 47.06 ± 6.02 diopters (D) for flat and 51.24 ± 6.75 D for steep. The posterior keratometric values were -6.70 ± 0.99 D (flat) and -7.67 ± 1.15 D (steep). Anterior astigmatism was on average with-the-rule (-1.97 ± 6.21 D), whereas posterior astigmatism was against-the-rule (+0.53 ± 1.02 D). The posterior and anterior astigmatism were highly correlated (r(2) = 0.839). After treatment, anterior keratometric values were 43.97 ± 5.81 D (flat) and 46.55 ± 6.82 D (steep). Posterior keratometric values were -6.58 ± 1.05 D (flat) and -7.69 ± 1.22 D (steep). Anterior astigmatism was on average with-the-rule (-1.56 ± 3.80 D), whereas posterior astigmatism was against-the-rule (+0.45 ± 1.29 D). The statistically significant (P < .05) keratometric changes indicated anterior surface flattening -3.09 ± 2.67 D (flat) and -4.19 ± 2.96 D (steep). The posterior keratometric changes were not statistically significant (P > .05).

CONCLUSIONS:

Before treatment, there was a strong correlation between posterior and anterior corneal astigmatism. After treatment, statistically significant anterior keratometric values flattened. The posterior surface keratometric values did not demonstrate statistically significant postoperative change: there was minimal posterior change, despite the significant anterior surface normalization.

• Authors: Anastasios John Kanellopoulos, George Asimellis
• Journal: Journal of refractive surgery (Thorofare, N.J. : 1995) (J Refract Surg) Vol. 30 Issue 5 Pg. 342-6 (May 2014) ISSN: 1081-597X [Print] United States
• PMID: 24893359 (Publication Type: Journal Article)
• Copyright: Copyright 2014, SLACK Incorporated.

Chemical References

• Cross-Linking Reagents
• Photosensitizing Agents
• Collagen
• Riboflavin

Topics

• Adult
• Astigmatism (physiopathology)
• Collagen (metabolism)
• Combined Modality Therapy
• Cornea (physiopathology)
• Corneal Stroma (metabolism)
• Corneal Topography
• Cross-Linking Reagents (therapeutic use)
• Female
• Humans
• Keratoconus (metabolism, physiopathology, therapy)
• Male
• Middle Aged
• Photorefractive Keratectomy
• Photosensitizing Agents (therapeutic use)
• Refraction, Ocular (physiology)
• Riboflavin (therapeutic use)
• Treatment Outcome
• Ultraviolet Rays
• Young Adult