Areas of refractive and cataract surgery have begun to collide, or so it seems. Research presented at this years Association for Research in Vision and Ophthalmology (ARVO) showed that optimal vision can be maintained by a wavefront-corrected IOL, and that refractive technology used in non-refractive procedures can improve vision and involve little pain. Other abstracts discussed improvements to IOLs, the best time to take wavefront measurements on pre-LASIK patients, the role of tear film in the quality of vision and more.

Medicated IOLs
Our clinical experience has shown us that cataract surgery patients, particularly elderly patients, often have difficulty instilling anti-inflammatory eye drops after intraocular lens (IOL) implantation. But, the use of eye drops may soon become a thing of the past for our cataract patients, say researchers from France.

They showed that IOLs dipped in diclofenac, a nonsteroidal anti-inflammatory drug, were as effective as diclofenac drops in quelling post-operative inflammation in patients who had senile cataracts.⁷⁸⁶ Also, patients achieved four to five lines in postoperative best-corrected visual acuity, regardless of whether they used drops or received the medicated lens.

All About Aberrations
Because the capsular bag slightly rotates IOLs, practitioners have been particularly concerned about the concept of wavefront-guided IOLs, as the registration of this lens and the aberrations must be exact in order to attain optimal vision. But, Texas researchers say that its still possible to maintain optimal vision with a wavefront-corrected IOL. They used a wavefront-corrected IOL and simulated implantation in 127 eyes (89 patients). Then, they rotated the IOLs up to 40 degrees.⁷⁰³ Results showed that 95% of the participants who received a wavefront-guided IOL had residual higher-order aberrations, but still had a lower amount of aberrations than normal untreated eyes. This majority had a torsional misalignment up to 7 degrees.

Some cataract patients who have pseudoexfoliation syndrome or trauma that results in cataract formation have zonular weakness, which makes them susceptible to capsular bag rupture. But, the insertion of a capsular tension ring during cataract surgery can provide a well-centered stable posterior chamber IOL for the majority of these patients, a study from the United Kingdom found. In fact, only 1% of the participants experienced IOL complication with vitreous loss.⁷⁴⁷

Pediatric Pseudophakia
IOL implantation has been the standard course of action for pseudophakic children. Researchers from Chicago decided to examine the refractive changes, best-corrected visual acuity, stereopsis and occurrences of amblyopia after primary IOL implantation in these children.⁷⁷³ Out of 42 eyes (32 patients), 83% achieved 20/70 best-corrected visual acuity, indicating that the procedure is very effective in achieving emmetropia. However, 56% of the patients developed amblyopia. This finding suggests that perhaps the surgeons did not accurately calculate the IOL to reach emmetropia in these patients  or that blur lingered despite implantation.

Finally, pediatric patients who underwent bilateral cataract surgery achieved better stereo acuity and vision than those who underwent a unilateral procedure. This finding raises the question of whether both lenses should be removed, even if the patient has unilateral pseudo-phakia. I look forward to an answer to this question.

New Techniques In Vitreous Removal
Researchers from Mexico discovered that diabetic patients who did not have a cataract at the time of vitrectomy but developed cataract during the postoperative period were more likely to have better outcomes from cataract surgery and were less likely to have postoperative complications than those who underwent combined cataract surgery and vitrectomy.³⁴⁵ So, if your proliferative diabetic retinopathy patient requires cataract surgery, consider sending him to a retinal specialist instead of a cataract surgeon.

Because nuclear sclerosis tends to progress rapidly after a vitrectomy, researchers from Italy examined the effectiveness of a non-vitrectomizing (TSV-25) vitreous surgery on patients who had idiopathic epiretinal membrane.⁵⁴³⁹ After 33 eyes underwent the procedure, cataract progression was seen in only one patient upon follow-up, and no patients developed retinal detachment. Some 92% of the participants experienced improvements in their visual acuity.

Refractive Technology, Non-Refractive Procedures
Until now, a manual keratectomy has been used to perform deep lamellar endothelial keratoplasty (DLEK). While the procedure has been successful, it often reduces visual acuity, despite decreasing astigmatism, when compared to a conventional penetrating keratoplasty.

But, researchers from Iowa discovered that the use of an automated microkeratome in DLEK might allow for faster visual rehabilitation than use of a manual one.²⁶⁹¹ Eighteen patients who underwent DLEK with an automated microkeratome had a mean best-corrected Snellen acuity of 20/35 and 20/32 at three and six months, respectively, and a corneal topographic cylinder of 3.06D and 0.875D. Those in the manual group (12) had a mean best-corrected Snellen acuity of 20/55 and 20/51 at three and six months, respectively, and a corneal topographic cylinder of 3.50D and 1.42D. Still, three buttonhole flaps were noted in the automated group, while there were no intraoperative complications in the manual group.

Researchers from Germany wanted to find out if modified PTK using an EpiLASIK epithelial flap would be as effective as traditional PTK but less painful.⁸⁹⁰ Using a keratome, they created an epithelial flap similar to EpiLASIK in 10 consecutive patients who had recurrent erosion. Best-corrected visual acuity returned to preoperative values within two weeks in all patients. Also, only two out of the 10 participants complained of moderate postoperative pain.

Quality of Vision
For those patients who do not achieve a pupil size of 6mm or larger prior to LASIK, mydriatic and miotic drops are required. But, these drops cause pupil center decentration, which can significantly distort wavefront measurements.

Researchers from Bausch & Lomb, however, discovered that accurate wavefront measurements can be taken by waiting 20 minutes after the instillation of mydriatic and miotic drops, as the pupil center was found to stabilize at this time.⁴³⁵⁷ They also discovered that mydriatic reversal drops should not be used to perform same-day refractive surgery, as centration from the drops will not match with the manifest pupil center location.

If a patient lacks adequate quality of vision after he or she has undergone refractive surgery, we often conclude that a wavefront correction or an enhancement is needed. But, a study from New Yorks University of Rochester revealed that treating the tear film may actually be the best course of action.⁸⁴⁸ The Shack-Hartmann wavefront sensor validated correlations between retinal image qualities and tear film break-up.

Therefore, since the only current application of wavefront technology is refractive surgery, in order to obtain optimal wavefront measurements, we must make sure that refractive surgery candidates have a good tear film.
 
Dr. Karpecki is director of research at Moyes Eye Center in Kansas City, Mo., He is a paid consultant to Bausch & Lomb.

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786. Weber M, Vabres B, Albouy C, et al. Control of inflammation with a diclofenac impregnated IOL following senile cataract surgery: results of a pilot study.
848. Li KY, Yoon G, Pan G. Variability in retinal image quality with tear film behavior after blink.
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2691. Goins KM, Sjoberg S, Gonzales M, Sutphin JE. Comparison of the visual outcome after manual and automated donor keratectomy in deep lamellar endothelial keratoplasty (DLEK). 
4357. Merchea MM, Lagana M, Cox I. Effects of dilation and dilation reversal agents on pupil center decentration in refractive surgery candidates.
5439. Viti F, Mariotti C, Amato G, et al. Peeling of idiopathic epiretinal membranes without vitrectomy prevents nuclear sclerosis progression.