January 2016

 

COVER FEATURE

 

Management of the irregular cornea

Eyeing more precise treatment for irregular corneas


by Vanessa Caceres EyeWorld Contributing Writer

 
   

S/P herpes, deep and excavated corneal scar corrected with VISX laser in PRK mode Source: Arun Gulani, MD

iDesign targets more accurate image capture for better outcomes

Patients with irregular corneas may be a relatively small group, but their treatment during refractive surgery can be challenging.

One key to better treatment is getting the best measurements possible before excimer laser use. Any technology that helps surgeons detect or measure each level of refractive aberration will make their treatment outcome that much more superior, said Arun C. Gulani, MD, Jacksonville, Fla.

One new technical advance assisting surgeons in the treatment of irregular corneas is the iDesign Advanced WaveScan aberrometer (Abbott Medical Optics, Abbott Park, Ill.), which was approved by the U.S. Food and Drug Administration (FDA) in May 2015.

The iDesign has a number of advantages that make the technology particularly useful for irregular corneas.13

The iDesign has significantly greater resolutionabout 5 timescompared to the WaveScan [Abbott Medical Optics], said Edward E. Manche, MD, professor of ophthalmology, Stanford University School of Medicine, and director of cornea and refractive surgery, Stanford Eye Laser Center, Stanford, Calif. The increased resolution leads to improved spot quality of the Hartmann-Shack raw data with less spot crossover effect. The increased resolution allows for more precise imaging of normal as well as highly aberrated eyes and more precise measurement of higher-order aberrations. The iDesign also has a greater dynamic range than previous technology and can measure 16 D to +12 D with up to 8 D of astigmatism, Dr. Manche said. The aberrometer captures information about the eye more accurately, said Steven C. Schallhorn, MD, San Diego. That more accurate capture ultimately leads to better refractive outcomes. Use of a stronger aberrometer does not help only with irregular corneas, Dr. Gulani said. He thinks that use of an effective excimer laser along with a trusted aberrometer will ultimately lead to better results in virgin eyes, complex eyes including irregular corneas, and eyes with complications from laser surgery. As aberrometer technology becomes more sophisticated, it gives surgeons a better plan for patient treatment. Its going from cookie- cutter LASIK or refractive surgery to picking the abnormality of the vision system of each patient and approaching it with a customized plan toward designing vision with their individual goals, Dr. Gulani said. Refractive outcomes with the technology have been favorable so far, Dr. Manche said. A study published in August 2015 that involved use of the iDesign reported that a monocular uncorrected distance visual acuity of 20/16, 20/20, and 20/25 was reached in 76.6%, 94.4%, and 96.6% of eyes, respectively.4 That study included 100 eyes of 50 consecutively treated patients. A study led by Dr. Schallhorn that included 621 eyes found that the mean manifest spherical equivalent decreased from 7.28 D to 0.09 D at 3 months after surgery. In the study, 82.4% of eyes achieved uncorrected distance visual acuity of 20/20 or better monocularly, and 92.5% achieved this binocularly.5

Finding ideal patients

In the big picture of ophthalmic surgery, its rare to find a patient with a significantly irregular cornea, which is why Dr. Schallhorn thinks its important to consider the use of technological advances like the aberrometer with all patients. That said, this doesnt mean everyone will qualify for surgery with use of the iDesign.

You have to make sure the patient is an otherwise good candidate for laser treatment and that he or she will likely achieve visual gain, he said. There are patients with irregular corneas that cant take advantage of excimer laser treatment, he said. This may include very irregular corneas that still cannot be captured with the new aberrometer. In the U.S., the system is approved to treat patients 18 and older with myopia and compound myopic astigmatism, Dr. Manche said. The system is approved to treat up to 5 D of astigmatism, an increase from the WaveScan, which was approved for 3 D. I also use the platform for patients with myopia and compound myopic astigmatism who are undergoing photorefractive keratectomy, Dr. Manche said. We have begun using iDesign to perform LASIK and PRK retreatments. These are off-label uses of the technology. In the short-term future, surgeons anticipate FDA approval for mixed astigmatism and hyperopia and compound hyperopic astigmatism, Dr. Manche said.

Keratoconus treatment?

Although some patients with keratoconus benefit from dual treatment with corneal crosslinking (CXL) and excimer laser treatment, this is not possible in the U.S. right now because CXL is not approved by the FDA. However, surgeons familiar with the iDesign platform are hopeful that it can one day be used in the U.S. for this purpose. Outside the U.S., the iDesign has been used to treat eyes with stable keratoconus using a surface ablation technique combined with collagen crosslinking, Dr. Manche said.

Dr. Schallhorn is looking forward to incorporating full corneal curvature into the wavefront profile.

References

1. Gulani AC. Corneoplastique: art of vision surgery. Indian J Ophthalmol. 2014;62:311.

2. Gulani AC. Using excimer laser PRKnot PTKfor corneal scars: Straight to 20/20 vision. Advanced Ocular Care. 2012;Sept/Oct: 13.

3. Gulani AC. Corneoplastique. Video Journal of Ophthalmology. 2007;22(3).

4. Smadja D, et al. Safety and efficacy of wavefront-guided myopic laser in situ keratomileusis using a new wavefront sensor technology: First 100 cases. J Cataract Refract Surg. 2015;41:15881593.

5. Schallhorn SC, et al. Outcomes of wavefront-guided laser in situ keratomileusis using a new-generation Hartmann-Shack aberrometer in patients with high myopia. J Cataract Refract Surg. 2015;41:18101819.

Editors note: Dr. Manche has financial interests with Abbott Medical Optics. Dr. Schallhorn has financial interests with Optical Express and Abbott Medical Optics. Dr. Gulani has no financial interests related to this article.

Contact information

Gulani: gulanivision@gulani.com
Manche: Edward.manche@stanford.edu
Schallhorn: scschallhorn@yahoo.com

Eyeing more precise treatment for irregular corneas Eyeing more precise treatment for irregular corneas
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