Technology closer to fulfilling wish list for micro incision cataract surgery

CATARACT surgeons have envisioned for decades cataract removal and refilling of the lens capsule through a tiny opening with restoration of visual clarity. Technological developments have been bringing us closer to these goals. Along the way, simultaneous correction of sphere, cylinder and higher order aberrations to optimise visual quality and function have been added to our wish list for cataract surgery.

So how near have we got to achieving these goals? Ultrasound phaco and laser photolysis systems have been developed with probes and tubing which allow us to remove cataracts more efficiently and safely through incisions as small as 1.0mm in width.

There already exist IOLs that can go through these incisions without enlargement or stretching of the wound. These are indeed significant advances.
Most conventional foldable IOLs and insertion devices available permit cataract wounds to be less than 3.0mm in diameter – already an important step in expediting visual rehabilitation and reducing induced astigmatism, wound leak and endopthalmitis.
Decreasing wound size further to 1.5mm or less increases those benefits further. Even more importantly, microincision cataract surgery decreases intraocular decompression and improves anterior chamber stability – particularly important when performing a lensectomy in a high myope.

Recent advances in the control of energy delivery, fluidics, surgical instruments and IOLs permit safer and easier lensectomy and IOL insertion. We are just now refining our techniques to take advantage of these advances. We are just now evaluating the safety and efficacy of these newer IOLs.

There was no point decreasing incision size if adequate access and excessive energy and fluid flow caused damage to the cornea and intraocular structures. There was little advantage in decreasing wound size if the wound needed to be enlarged for IOL insertion. There was no point implanting IOLs or injecting gels through 1.5mm incisions or less if the IOLs had poorer optical quality or capsular or uveal biocompatibility, either short or long-term, than IOLs inserted through 3.0mm incisions.

When considering ideal incision size, lensectomy procedure and crystalline lens replacement material, the potential for modification of refraction and accommodative amplitudes, as well as ease of IOL material removal, will also need to be considered.

The safety and efficacy of IOL materials and designs under all these conditions should be evaluated. Extensive analysis will be required to demonstrate the safety of possibly toxic monomers in IOL material, which is inserted partially unpolymerised to permit the post-implantation adjustment of sphere, cylinder and other aberrations. Studies will need to demonstrate no potential ocular damage from ultraviolet laser energy, which is used to accomplish the adjustments.

Novel approaches for preventing posterior capsule opacification (PCO) are being developed for microincision cataract surgery. In addition, preliminary results in studies using the same IOL indicate that laser photolysis may lead to less PCO than ultrasound phaco.

As for as some of the other items on a cataract surgeon’s wish list, some marketing promoters would have us believe that the restoration of accommodation and elimination of aberration are, and should be, the standards by which we evaluate the results of cataract surgery already today. Some of those promoters would have us believe that many ophthalmic device companies have already developed technology measuring up to those ‘standards’.

It is as foolish to claim those ‘standards’ already exist as it is to desire the elimination of all aberrations without yet knowing how and why some higher order aberrations enhance visual quality and function. We still need to increase our understanding and work on many new developments before we can hope to routinely offer lensectomy in non-cataractous eyes for the purposes of correcting presbyopia and refractive errors with improved visual quality and function.

It is well known that not all new technology will ultimately prove safe and effective. It is also well known that some new technologies are not useful until other new technologies are developed.

We must continue to dream, excite and progress. However, we must be careful not to confuse ourselves, our patients, or our colleagues as we strive for what we envision as ultimate goals. We must be careful not to raise expectations beyond realistic outcomes. Most importantly, we must carefully consider all safety issues before the clinical application of new technologies.

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