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LARGEST STUDY ON CHINESE AMERICANS PUBLISHED

LARGEST STUDY ON CHINESE
AMERICANS PUBLISHED

USC Ophthalmology Researchers Find More
Effective Treatments For Blinding Eye Diseases

EDUCATION

Case Study: Clear as Mud

Haghighi Randleman
Presenter: Arezu Haghighi, MD Discussant: J. Bradley Randleman, MD
 

History

  • 33-year-old healthy female with history of LASIK OU in 2004 presented with blurred vision in both eyes for several months duration, left worse than right
  • Denies eye pain but complains of problems with glare at night

Exam Findings

  • Normal external exam
  • Refraction with high sphere and high astigmatism prescription
  • Corneal topography with high irregular astigmatism
Figure 1
Figure 1: Corneal topography showing a high degree of asymmetric astigmatism.

 

Differential Diagnosis

  • Post-LASIK ectasia
  • Forme Fruste Keratoconus
  • Pellucid Marginal Degeneration
  • Keratoglobus

Additional Clinic Photos

Figure 2
Figure 2: Representative slit lamp photos. A) Shows cross-sectional view of cornea with paracentral thinning and apical steepening. B) Downgaze reveals triangular distortion of the lower lid due to the ectatic cornea (Munson’s sign). C) Lateral corneal illumination produces a triangular focus of light (Ruzzuti’s sign).

 

Diagnosis

  • Post-LASIK ectasia

Pathophysiology

  • Incidence rate of 0.04 percent-0.6 percent occurring primarily after LASIK and usually developing within one-year post-procedure.
  • Histopathologic findings include interlamellar and interfibrillar slippage through disruption of lamellar bonds in the stroma isolated to ectatic regions only. Additional findings include breaks in Bowman’s layer and larger than normal interlamellar clefts.
  • LASIK flap no longer contributes to the tensile strength of the cornea so residual stromal bed thickness (RSB) is remaining load bearing tissue.
  • Ectasia risk criteria for predicting which patients are at greatest risk of developing post-LASIK ectasia based on: 1. abnormal pre-operative topography, 2. low RSB, 3. young age, 4. low pre-op corneal thickness, and 5. high myopia.
  • Percent tissue altered (PTA) takes into account many of these factors (corneal thickness, ablation depth from myopia, and flap thickness) to provide a more individualized screening metric.
Figure 3
Figure 3: Histological changes in the post-LASIK ectatic cornea with corneal epithelial thinning (arrowheads), breaks in Bowman’s (star), and larger than normal interlamellar clefts (arrows).

 

Treatment

  • Contact lenses (RGPs)
  • Intracorneal Ring Segments
  • Penetrating Keratoplasty (PKP)
  • Corneal Cross-linking (CXL)
Figure 4
Figure 4: Image of the cornea during CXL treatment. The green glow of the cornea results from the yellow riboflavin drops fluorescing under the blue ultraviolet light.

 

Prognosis and Future Directions

  • Corneal cross-linking using the standard protocol with epithelial removal and 30-minute treatment duration has been shown to halt the ectatic process in more than 95 percent of treated eyes. This treatment has been proven effective in post-LASIK ectasia as well as keratoconus, and long-term results show good stability over 10-year follow-up. The standard protocol is now FDA-approved for use in the US and is being offered at the USC Roski Eye Institute.

References

  • Rabinowitz YS, et al. Computer-Assisted Corneal Topography in Keratoconous. Refractive and Corneal Surgery (1989); 5(6):400-408.
  • Lopez A, Garcia R, Bernfeld E, Hernandez-Camarenda J. Ectasia Risk in Topography. Eyewiki.org.
  • Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk Assessment for Ectasia after Corneal Refractive Surgery. Ophthalmology. (2008); Jan 115(1):37-50.
  • Edelhauser et al. Corneal Ectasia After Excimer Laser Keratorefractive Surgery: Histopathology, Ultrastructure, and Pathophysiology. Ophthalmology (2008); 115(12):2181-2192.
  • Rabinowitz YS. Keratoconus. Survey of Ophthalmology 1998 Jan-Feb; 42(4):297-319.
  • Richoz O, Mavrakanas N, Pajic B, Hafezi F. Corneal Collagen Cross-Linking for Ectasia after LASIK and Photorefractive Keratectomy. Ophthalmology (2013); 120(7):1354-1359.
  • Raiskup F, Theuring A, Pillunat LE, Spoerl E. Corneal Collagen Crosslinking with Riboflavin and Ultraviolet- A Light in Progressive Keratoconus: Ten-Year Results. J Cataract Refract Surg. 2015 Jan; 41(1):41-46.

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Produced by: Monica Chavez, John Daniel, Joseph Yim and Dr. Vivek Patel
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