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Astigmatic Keratotomy for the Correction of Astigmatism Workup

  • Author: James Hays, MD, MHA, MBA; Chief Editor: Hampton Roy, Sr, MD  more...
 
Updated: Dec 02, 2014
 

Imaging Studies

In order to produce accurate arcuate incisions, the use of corneal topographers and/or corneal tomographers is essential when visualizing the corneal landscape. Elevation maps can identify regular versus irregular astigmatism, the magnitude of the astigmatism, and its relationship with the overall contour of the anterior corneal surface. Fortunately, over the past ten years, both topographers and tomographers have become commonplace in ophthalmic practices, allowing for better preoperative and postoperative assessment of corneal contour.

Combined elevation and thickness measurements can be obtained from machines such as the Orbscan and Pentacam. Both technologies offer an added advantage over standard topographers: mapping the posterior corneal curvature, an area whose relevance had been overlooked for many years. Recently, some ophthalmic investigators have attributed improved refractive results when considering the contribution of the posterior corneal curvature to total corneal power.[18]

Since traditional astigmatic keratotomy (AK) nomograms are based on ultrasonic pachymetry measurements, one must correlate corneal thickness values measured with the Orbscan or Pentacam with those obtained from a standard ultrasonic pachymeter. Statistical differences between thickness readings from these machines have been reported.[19]

 
 
Contributor Information and Disclosures
Author

James Hays, MD, MHA, MBA Consulting Staff, Department of Corneal Transplantation and Refractive Surgery, Atlanta Eye Surgery Center

Disclosure: Received salary from Alimera Sciences for consulting.

Coauthor(s)

Debra M Stone, OD, MS Consultative Optometrist and Outcomes Analyst, Woolfson Eye Institute

Debra M Stone, OD, MS is a member of the following medical societies: American Academy of Optometry, Georgia Optometric Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Simon K Law, MD, PharmD Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology, Association for Research in Vision and Ophthalmology, American Glaucoma Society

Disclosure: Nothing to disclose.

Louis E Probst, MD, MD Medical Director, TLC Laser Eye Centers

Louis E Probst, MD, MD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, International Society of Refractive Surgery

Disclosure: Nothing to disclose.

Chief Editor

Hampton Roy, Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Hampton Roy, Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

Additional Contributors

Daniel S Durrie, MD Director, Department of Ophthalmology, Division of Refractive Surgery, University of Kansas Medical Center

Daniel S Durrie, MD is a member of the following medical societies: American Academy of Ophthalmology, Association for Research in Vision and Ophthalmology

Disclosure: Received grant/research funds from Alcon Labs for independent contractor; Received grant/research funds from Abbott Medical Optics for independent contractor; Received ownership interest from Acufocus for consulting; Received ownership interest from WaveTec for consulting; Received grant/research funds from Topcon for independent contractor; Received grant/research funds from Avedro for independent contractor; Received grant/research funds from ReVitalVision for independent contractor.

Acknowledgements

Mauro Fioretto, MD Professor of Ophthalmology, University Eye Clinic of Genova; Head of Ophthalmology Department, Hospital of Casale Monferrato, Italy

Disclosure: Nothing to disclose.

Vincenzo Orfeo, MD Head, Operating Unit, Clinica Mediterranea, Naples, Italy

Vincenzo Orfeo, MD is a member of the following medical societies: American Academy of Ophthalmology

Disclosure: Nothing to disclose.

Antonio Pascotto, MD Consulting Ophthalmologist, Pascotto, Istituto per la Salute degli Occhi, Clinica Mediterranea, Italy

Disclosure: Nothing to disclose.

Sergio Claudio Saccà, PhD Professor of Ophthalmology, Department of Neurological and Visual Sciences, Ospedale San Martino, Italy

Disclosure: Nothing to disclose.

Spencer Thornton, MD Medical Director, Thornton Eye Center

Spencer Thornton, MD is a member of the following medical societies: American Academy of Ophthalmology and American College of Surgeons

Disclosure: Nothing to disclose.

References
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Thornton astigmatic keratotomy ruler.
Close-up view of Thornton astigmatic keratotomy ruler.
Example 2. Routine astigmatic keratotomy. In this image, a nasal astigmatic keratotomy is shown. This image was taken minutes after performing the incision. Note that the area around the cut stains lightly with fluorescein.
Example 3. Preoperative topography in a patient about to undergo astigmatic keratotomy (AK) following corneal transplantation. This 30-year-old woman underwent corneal transplantation for keratoconus 6 years ago. She presented with a clear graft but with excessive astigmatism. Based on this pre-AK topography and prior surgical experience, an incision was placed just inside the donor-recipient interface from 250° to 300°. A second incision was placed between 30° and 70°. Incisions were not paired at 180° apart, but were localized based on topography. Refraction improved from +0.75 + 3.00 X 58° to +0.50 + 1.50 X 130°. Best-corrected vision remained 20/20.
Example 3. Postoperative topography following astigmatic keratotomy for the 30-year-old woman with penetrating keratoplasty for keratoconus.
Example 4. Topography shows preoperative and postoperative readings with differential analysis in a corneal transplant recipient (performed for Fuchs dystrophy) who underwent astigmatic keratotomy (AK). After all sutures were removed, she had approximately 6.5 D of keratometric astigmatism. The previous sutures seemed to have been tighter temporally than nasally. She underwent AK with a 50° incision temporally and a 30° incision nasally. The alteration in arcuate size values was related to surgeon preference. Following AK, residual astigmatism was slightly less than 1 D. The 5.5 D of astigmatism alteration from an 80° relaxing incision in a normal cornea is not expected. Posttransplant corneas are variable, and individual results can vary widely. Monitor the results as best as possible intraoperatively and be willing to go back and suture an overcorrection if one should occur.
 
 
 
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