If you have had problems with vision correction surgery elsewhere, we would be happy to try to help you. We see many patients with such problems. A complete evaluation usually will diagnose your problem and we then can formulate a plan to improve your situation.
There are a variety of techniques which may help you. For instance, we are experienced in the wide variety of LASIK flap management procedures (including corneal smoothing and suturing), laser retreatments (including topography-guided LASIK and PRK treatments), as well as other procedures, such as CK and Intacs, to treat particular LASIK complications. Certainly, we usually can define your problem and give you a good recommendation as to how best to proceed.
State-of-the-art diagnostic tools include:
Corneal topography instruments to assess your cornea’s optical surface and architecture. This includes the new Pentacam HR, Topolyzer, EyeSys, Keratron, HD Analyzer, and PAR units. Each of these maps the cornea in slightly different ways, giving information useful to your care.
Wavefront analysis of the eye’s optical system and assessment of aberration profile
New Reichert Optical Response Analyzer: It measures the biomechanics (eg elasticity, rigidity, and flexibility) of the cornea. This may allow for better analysis of LASIK safety in your case and may also aid in planning treatment based on your specific corneal structure.
Corneal thickness (ultrasonic pachymentry)
Specular microscopy to determine the quantity and quality of the cornea’s endothelial cell layer
The goal of this comprehensive evaluation is multifold. First, we want to fully assess and define your problem in order to give you the proper diagnosis. Second, this testing will allow us to best recommend a course of treatment (whether optical or surgical) to optimize your visual function.
If surgery is recommended, you may rest assured that we have the experience to handle the many kinds of difficult problems with which patients are referred to us. Surgical options may include various forms of LASIK, surface laser procedures, CK, Intacs, corneal suturing, partial thickness and penetrating keratoplasty, and combinations of these procedures.
Management of Corneal Ectasia after LASIK
At the CLEI Center for Keratoconus, we are particularly interested in the management of corneal ectasia, a condition like a keratoconus in which the cornea weakens and distorts over time. Specific risk factors for ectasia after LASIK and PRK include high myopia, thin residual stromal bed, and forme fruste keratoconus on preoperative topography. Currently, the pathogenesis of ectasia after laser refractive surgery remains unclear. In many cases, it is likely that the eventually ectatic cornea harbored a predisposition to keratoconus preoperatively, either with undiagnosed frank keratoconus, forme fruste keratoconus, or an otherwise seemingly normal cornea. In others remains the possibility that removal of tissue during LASIK or PRK thinned the cornea enough to destabilize the corneal biomechanics to cause frank ectasia.
An understanding of corneal biomechanics also may help to elucidate the mechanism of postoperative corneal ectasia. Similar to keratoconus, it appears that there is a loss and/or slippage of collagen fibrils and changes to the extracellular matrix in the ectatic corneal stroma. These changes are thought to cause biomechanical instability of the cornea with consequent changes in both the cornea’s anatomic and topographic architecture. In ectasia, these changes are concentrated in the residual stromal bed.
To treat ectasia, corneal collagen crosslinking is generally suggested. The goal of the collagen crosslinking procedure is to strengthen the ectatic cornea to prevent further distortion of the corneal topography over time. During the procedure, riboflavin (Vitamin B2) is administered in conjunction with ultraviolet A (UVA – 365nm) irradiation. Riboflavin acts as a photosensitizer which causes a crosslinking effect within the cornea (like putting extra wires on a bridge) which results in mechanical stiffening of the cornea. Whether the actual “crosslinks” are between or within collagen molecules or involve corneal proteoglycans, remains unclear. Dr. Hersh and Dr. Greenstein can assess to see if other procedures may be a viable option for you, such as topography-guided PRK (TGPRK).
In corneal ectasia, CXL appears to stabilize corneal topography and vision and in some cases offer a modest improvement. One year results from our single-center of patients enrolled in a U.S. multicenter clinical trial of crosslinking revealed a significant improvement of best-corrected visual acuity of about 0.5 Snellen lines, and a flattening of maximum keratometry by 1D; however, this change was not statistically significant. Individually, best-corrected visual acuity improved by two or more lines in 23% (5/22) of post LASIK ectasia patients and worsened by 2 or more lines in 4.5% (1/22) of patients. With regards to topography, 23% (5/22) of patients flattened by 2D or more, and 9% (2/22) of patients steepened by 2D or more. Postoperatively, most patient’s vision and topography remained stable at one year.
Click above for Dr. Hersh’s clinical study which led to U.S. FDA approval of corneal collagen crosslinking for keratoconus
Crosslinking can be used adjunctively with other treatments such as Intacs intracorneal ring segments, laser treatments (topography-guided PRK), and other treatments to stabilize the cornea and give you the best vision possible.