In most cases, patients who undergo cataract surgery regain their vision once the cataract is removed and an intraocular lens (IOL) is implanted in its place. With modern refractive cataract surgery, many patients are able to see 20/20 without glasses or contact lenses after surgery.

However, particularly among younger patients who undergo surgery for cataracts, blurred vision can return due to the development of what’s called a “secondary cataract.”

A secondary cataract is a clouding of the posterior portion of the natural lens capsule that is purposely left inside the eye during cataract surgery.

The posterior lens capsule is left in place during cataract surgery so the gel-like material (vitreous) that fills the posterior portion of the eye does not leak from the eye during the procedure. Loss of vitreous from the eye could cause serious cataract surgery complications, including a detached retina.

Usually, the posterior lens capsule remains clear after cataract surgery. But in some cases, the capsule becomes cloudy, affecting vision. The technical term for secondary cataract is posterior capsular opacification (PCO).

In most cases, secondary cataract can be successfully treated with a non-invasive procedure called a laser capsulotomy. A special type of infrared laser called a Nd:YAG laser is used for this procedure, which is sometimes called a YAG capsulotomy.

The laser creates a clear hole in the center of the cloudy lens capsule to restore clear vision. A YAG capsulotomy takes only a few minutes, and there are no restrictions after the procedure.

Recently, researchers in Sweden conducted a 10-year study to determine the long-term risk of secondary cataracts among patients younger than age 65 who underwent cataract surgery at a single surgical center (Norrlands University Hospital in Umea, Sweden).

A total of 116 patients were included in the study, and 94 percent of them received an acrylic IOL implant during the cataract removal procedure.

Results of the study showed that 10 years after cataract surgery, 37 percent of the patients who were younger than 65 years of age at the time of surgery later developed PCO or secondary cataract that required laser capsulotomy treatment to restore vision.

Though the study reveals a significant risk for the development of visually significant PCO among patients who have cataract surgery when they are younger than age 65 at the time of surgery, advances in cataract surgery technique and IOL design since the time of the cataract surgery performed in this long-term study may have reduced this risk.

SOURCE:  Ten-year longitudinal visual function and Nd:YAG laser capsulotomy rates in patients less than 65 years at cataract surgery. American Journal of Ophthalmology. February 2010.

Thin-flap LASIK (also called sub-Bowman keratomileusis or SBK) is similar to LASIK, but involves creating a significantly thinner flap on the eye to preserve more corneal thickness under the flap. In the thin-flap LASIK procedures evaluated in this study, the corneal flap was created with a femtosecond laser.

LASEK (laser subepithelial keratectomy or laser epithelial keratomileusis) is a modification of LASIK wherein a very thin flap consisting only of the outer epithelial tissue of the cornea is lifted from the eye after being loosened from the underlying tissue with an alcohol solution. Other commonly performed variations of LASIK include Epi-LASIK and Presby-LASIK.

In both thin-flap LASIK and LASEK, the corneal flap is less than 100 microns thick. In conventional LASIK, it is not unusual for the flap to be greater than 150 microns thick.

Thin-flap LASIK vs. LASEK: Study design

This study compared the visual and refractive outcomes of 1,072 eyes treated with thin-flap LASIK and 1,036 eyes treated with LASEK.

Prior to surgery, all eyes were nearsighted, with a mean of -3.93 diopters (D) of myopia in the thin-flap LASIK group and -3.87 D in the LASEK group.

Outcomes were measured one day, one week, one month and three months after surgery, and included:

• Uncorrected visual acuity (UCVA)
• Best spectacle-corrected visual acuity (BSCVA)
• Gain or loss of BSCVA after surgery compared to before surgery

Thin-flap LASIK vs. LASEK: Results

Analysis of the study data revealed:

• The day after surgery, mean UCVA was between 20/20 and 20/25 in thin-flap LASIK eyes and slightly worse than 20/30 in LASEK eyes.
• At one month after surgery, mean UCVA was nearly 20/20 in thin-flap LASIK eyes and between 20/20 and 20/25 in LASEK eyes.
• At three months after surgery, mean UCVA was slightly better than 20/20 in both groups.
• At three months after surgery, BSCVA also was better than 20/20 in both groups.

At three months after surgery, three eyes (0.28 percent) in the thin-flap LASIK group and ten eyes (0.96 percent) in the LASEK group gained two or more lines of BSCVA compared to pre-surgical levels.

Also at three months after surgery, 9 eyes (0.84 percent) in the thin-flap LASIK group and 20 eyes (1.93 percent) in the LASEK group lost two or more lines of BSCVA compared to pre-surgical levels.

Losses in best spectacle-corrected visual acuity diminished with time. At six months after surgery, only three eyes (0.28 percent) in the thin-flap LASIK group and two eyes (0.19 percent) in the LASEK group showed a loss of two or more lines of BSCVA.

Conclusions

The researchers concluded that both thin-flap LASIK and LASEK are safe and effective for the correction of low to moderate myopia, but all-laser thin-flap LASIK provides faster visual recovery and slightly better visual and refractive results in the three months following surgery.

SOURCE:  Comparison between femtosecond laser-assisted sub-Bowman keratomileusis vs laser subepithelial keratectomy to correct myopia. American Journal of Ophthalmology. Published online September 24, 2009.

Lasers and pacemakers: Study design and methods

Dr. Sher evaluated the effect of operating a number of lasers used in eye surgery, including a popular excimer laser used in LASIK and PRK, on popular cardiac pacing devices manufactured by Medtronic (Minneapolis) and St. Jude Medical (St. Paul).

To simulate the devices being implanted in a human subject, the pacemakers and defibrillators were submerged in salt water in a waterproof container to simulate resistance around the heart.

The lasers were then fired in close proximity to the devices to see if electromagnetic fields generated by the lasers would cause the pacemakers and defibrillators to malfunction.

Lasers and pacemakers: Study results

The study revealed that operation of the ophthalmic lasers caused no malfunction in any of the cardiac pacing devices tested.

The experiment was repeated several times without the occurrence of a single adverse event.

Conclusions

Dr. Sher concluded that the results of the testing suggest laser vision correction and other forms of laser eye surgery pose little cardiac risk to patients who have an implanted pacemaker or defibrillator.

He noted that the worst-case scenario was used in the study, with the use of the highest laser energy, the most pulses, the widest laser beams, and the most sensitive settings on the cardiac devices.

Dr. Sher recommends surgery centers reconsider the posting of warning signs about lasers and pacemakers on the doors of their laser suites, and he believes lasers commonly used in eye surgery pose no risk to the normal operation of cardiac pacing devices.

SOURCE:  A beat beyond: pacemakers and lasers. EyeWorld. June 2009.

Study design and methods

Steven C. Schallhorn, MD, global medical director for Optical Express, and colleagues reviewed the records of 49,011 eyes of 24,505 consecutive patients who recently had laser vision correction at Optical Express. The company is Europe’s largest provider of LASIK surgery and has over 200 locations.

All patients had laser vision correction treatments performed with the STAR S4IR excimer laser system (Abbott Medical Optics, Santa Ana, Calif.). Corneal flaps were created with either an IntraLase FS-60 femtosecond laser (Abott Medical Optics) or a Moria single-use microkeratome (Moria, Antony, France).

Refractive errors prior to surgery ranged from -12.00 D of nearsightedness to +6.00 D of farsightedness, with a mean astigmatism correction of -0.76 D. The mean amounts of myopia and hyperopia prior to surgery were -2.97 D and +2.34 D, respectively.

Results and conclusions

Analysis of the study data revealed:

• 91 percent of patients undergoing laser vision correction were treated with LASIK; nine percent were treated with LASEK.
• Most patients (80 percent) chose wavefront-guided LASIK over conventional LASIK.
• 70 percent chose all-laser LASIK, with the corneal flap created with a femtosecond laser rather than a bladed microkeratome.
• One month after surgery, the mean spherical equivalent (MSE) refraction of all patients was -0.08 D, and 85 percent of eyes were within 0.50 D of their intended correction.
• One month after surgery, 86 percent of eyes treated for myopia and 61 percent of eyes treated for hyperopia attained uncorrected visual acuity (UCVA) of 20/20 or better.
• Among patients who had laser vision correction (LASIK or LASEK) performed on both eyes, 93 percent achieved binocular UCVA of 20/20 or better.
• The overall rate of LASIK complications was very low (0.8 percent), and most complications (dry eye, keratitis, transient light sensitivity, etc.) were successfully treated without long-term adverse effects.
• Flap complications were rare, and there were fewer flap problems among patients who had all-laser LASIK with the corneal flap created with a femtosecond laser.

Dr. Schallhorn noted that the patients’ preference for all-laser LASIK shows the public’s acceptance of this advanced technology despite its higher cost. He also said the results of the study suggest femtosecond lasers have a safety advantage over bladed microkeratomes when creating LASIK flaps.

SOURCE:  Large-scale study validates positive LASIK results. EyeWorld. May 2009. (Supplement: Premium Clinical Options for Cataract and Refractive Surgery, sponsored by Abbott Medical Optics.)

In the study, 998 eyes with nearsightedness ranging from -1.00 to -8.00 diopters (D) were treated at the university eye center using one of the following laser eye surgery procedures: LASEK, Epi-LASIK, PRK and Epi-PRK.

LASEK, Epi-LASIK and PRK: Study design

In the LASEK and PRK groups, the corneal epithelium was first loosened from the underlying corneal tissue with a 20 percent alcohol solution for 20 seconds. In the LASEK group, the flap was reapplied to the eye after the wavefront-guided excimer laser treatment; in the PRK group, the flap was removed and discarded.

In the Epi-LASIK and Epi-PRK groups, a hand-held surgical tool called a MicronEdge Separator, (Gebauer Ophthalmic Instruments, North Palm Beach, Fla.) was used to create the epithelial flap. In the Epi-LASIK group, the flap was reapplied to the cornea after the laser treatment; in the Epi-PRK (also called flap-off Epi-LASIK) group, the flap was removed and discarded.

In all procedures, the wavefront-guided laser ablation was performed with a VISX Star S4 IR excimer laser (Abbott Medical Optics, Santa Ana, Calif.).

All eyes were evaluated for a period of one year after surgery, and measures of uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) were taken before surgery and throughout the post-operative period.

Results

Analysis of the data one year after surgery revealed that there was no statistically significant difference in proportion of eyes achieving UCVA of 20/20 or better and BSCVA of 20/20 or better among the four surgical groups.

Refractive results were found to be very stable in all surgery groups, and outcomes were within 0.50 D of the intended correction in at least 96 percent of eyes in all groups.

Sadhana Kulkarni, MD, presented the results of the study at the annual meeting of the American Society of Cataract and Refractive Surgery (ASCRS) this week in San Francisco.

SOURCE:  Large retrospective study explores best technique for wavefront-guided surface ablation. Ophthalmology Times. Published online April 5, 2009.