The Evolution of Bioptics

Operating on patients who are outside of the acceptable limits of refractive procedures (ie, LASIK, PRK) may increase the rate of complications including ectasia, haze, and glare. While we continue to fine-tune our current refractive solutions and develop entirely new techniques, we must consider the technological limitations of both today and tomorrow.

ADDRESSING THE PRESENT, PREPARING FOR THE FUTURE
It is important that surgeons streamline their procedures to be more compatible with lens surgery, because as our LASIK patients age and become presbyopic, they will return to us for a solution. Therefore, we should work toward refractive surgeries that are complementary and transitory with a future intraocular procedure. We need to devise successful ways to address our patients' current vision problems, without preventing ourselves from meeting their future visual needs.

Currently, the two most important transitional technologies are the excimer laser and the phakic IOL. I cannot stress enough that corneal surgery must be seen as a complement to future intraocular surgery. If we look ahead, we have an opportunity to prepare the cornea with the most accurate profile and potentially reduce higher-order aberrations or prolate asphericity of the cornea—both of which may complicate a future intraocular surgery.

EVOLUTION OF BIOPTICS
Bioptics is a surgical procedure that addresses refractive error by combining the use of corneal and lenticular techniques. The procedure was originally developed for high and extreme refractive errors with LASIK 1 month after phakic IOL implantation.

In 1995, we began performing LASIK over the Visian Implantable Contact Lens (ICL; STAAR Surgical, Monrovia, California). One year postoperatively, we performed planned LASIK over the ICL to distribute the total power in two planos: one over the cornea with LASIK and prelenticular with the ICL. Performing LASIK surgery that planned for future IOL implantation avoided many postoperative complications including poor vision, halos, increased cataract, and risk of ectasia—especially in patients with high IOL power implants (ie, more than 15.50 D).

In 2001, we began performing wavefront-guided LASIK over ICLs to address residual error. This was discontinued because LASIK was performed prior to ICL implantation—preventing us from calculating the total aberrations.

In 2005, we began performing concurrent astigmatism correction with LASIK plus ICL implantation. We coined this new technique simultaneous bioptics. This procedure required us to move our patients from the operation room to the laser, which would prove to be our largest obstacle. Therefore, we created a 12-hour window between ICL implantation and laser treatment; we called this sequential bioptics. Currently, we use sequential bioptics as our routine procedure for patients with moderate-to-high astigmatism (1.50 D or greater).

Recently, we extended this procedure to patients with cataracts for the correction of astigmatism greater than -2.00 D. We also found that this technique termed pseudophakic sequential bioptics implied a total correction of topographic astigmatism.

The advantage is that this procedure not only corrects the spherical defects, but the cylindrial defects as well. In addition to the cataract extraction, this technique allows the patient to recover BSCVA extremely quickly. Patients with multifocal IOLs present with extremely low tolerance to the astigmatic residual defect. By correcting the astigmatism preoperatively, we avoid this complication and increase the number of patients who can tolerate the procedure.

WHAT WE HAVE LEARNED
As we moved from incision techniques like radial keratotomy and penetrating keratoplasty to laser technologies such as PRK and LASIK, we discovered that high-power ablation correction induced more glare and halos and decreased postoperative BCVA. Simultaneously, we found that low-power IOLs produced fewer complications and had larger optical zones for better night vision. It was also at this time that we decided to place limits on ICLs and LASIK. In 1998, we discovered that higher-diopter lenses (which are thicker) created a higher risk of posterior capsular opacification. Because of this, we placed the following limits on the surgery: the ICL should be less than -15.50 D, and the myopic LASIK treatment should be less than 6.00 D.

FINE-TUNING IOLs
It is important to note that ICL and LASIK power calculations are more challenging with the sequential bioptics method; we would have to use an estimated keratometric value and the theoretical refractive power post-LASIK. Factors to consider include the distance of the vertex, astigmatic induction from a clear corneal incision, and any internal astigmatic modifications of the ICL. As we improve our techniques in preparing the perfect cornea to match the IOL we implant, we will see an improvement in the quality of vision.

CONCLUSION
We have performed sequential bioptics on hundreds of eyes at the Instituto Zaldivar, in Argentina. We found that it dramatically improves vision quality after IOL implantation. Additionally, pseudophakic sequential bioptics has helped us to perform surgery in patients who would never be candidates for multifocal IOLs. Our goal has always been to give the patient as much immediate and maximum comfort as possible, and to date, we have been highly satisfied with our results.

Roberto Zaldivar, MD, is the Scientific Director of the Instituto Zaldivar, in Mendoza, Argentina. Dr. Zaldivar states that he has no financial interest in the products or companies mentioned. He may be reached at +54 261 441 9999; zaldivar@zaldivar.com.