Presbyopic LASIK procedure corrects distance and near vision simultaneously

Dan Z. Reinstein

Presbyopic LASIK using a new nonlinear aspheric ablation profile that increases the depth of field of the eye allows micro-monovision to safely and effectively treat presbyopia in combination with myopia, hyperopia and emmetropia, a surgeon said.

Dan Z. Reinstein, MD, MA(Cantab), FRCSC, FRCOphth, presented results of a study on nonlinear aspheric presbyopic micro-monovision LASIK at a symposium sponsored by Carl Zeiss Meditec during the American Society of Cataract and Refractive Surgery meeting in San Francisco.

Nonlinear aspheric ablation profile

“The treatment represents a form of ‘laser-blended vision’ that uses a specialized nonlinear aspheric ablation profile incorporated into the refractive correction to increase depth of field for simultaneous correction of distance and near vision,” Prof. Reinstein told Ocular Surgery News.

The dominant eye is targeted for exactly plano, and the nondominant eye is targeted for slight myopia, with an ideal target of –1.5 D, he said.

“Nonlinear aspheric micro-monovision LASIK is a versatile presbyopic procedure because it can be performed for patients with refractions ranging from +5.75 D to –8.5 D,” Prof. Reinstein said. “In contrast to conventional monovision, it is well-tolerated since very little anisometropia is required. Based on these features and the outcomes we’ve achieved, almost all presbyopes who come into our clinic who are candidates for laser vision correction are now receiving this treatment.”

Near, distance and binocular vision

The series that Prof. Reinstein reported included 136 myopes (median age, 49 years), 111 hyperopes (median age, 56 years) and 119 emmetropes (median age, 54 years). He and colleagues treated myopia of up to –8.5 D and hyperopia of up to +5.75 D, and they have published the results of the myopic and hyperopic population in the Journal of Refractive Surgery.

LASIK was performed in all eyes using the Hansatome zero-compression microkeratome (Bausch & Lomb) and the MEL80 excimer laser with customized ablation programming using the CRS-Master software (Carl Zeiss Meditec). Results were analyzed based on 1-year data with more than 90% follow-up.

In monocular visual acuity testing with data pooled for all patients (+5.75 D to –8.5 D), distance uncorrected visual acuity was 20/20 or better in 92% of eyes treated for distance and 20/63 or better in 80% of eyes treated for near. In binocular testing, at least 95% of patients in each of the three subgroups achieved distance UCVA of 20/20 or better, and 100% achieved 20/32 or better.

“Even with the addition of considerably blurrier distance vision in the near eye, distance UCVA showed a boost in binocular testing compared with the vision achieved in the distance eye alone,” Prof. Reinstein said.

After surgery, UCVA was the same, better than or no worse than one line less than the preoperative best corrected visual acuity in 94% of eyes, based on data pooled for all patients.

“This is an important endpoint to consider because the satisfaction of refractive surgery patients is generally related to how well their postoperative vision compares to their preoperative vision with glasses,” he said.

Binocular near vision results were good in all subgroups, with 81% to 96% of patients seeing J2 or better, 94% to 99% seeing J3 or better, and all achieving J5 or better near vision.

Consistent with the distance vision outcomes, the procedure demonstrated good refractive accuracy. The safety profile was also favorable. No eye lost two or more lines of BCVA, whereas rates of one-line loss in the myopic, hyperopic and emmetropic subgroups were 8%, 17% and 13%, respectively. Contrast sensitivity was either unchanged from the preoperative level or significantly increased at some spatial frequencies, Prof. Reinstein said.

Neurologic selection of images

This procedure is also differentiated from other forms of presbyLASIK and multifocal IOLs because it does not result in multiple images within the same eye, Prof. Reinstein said. Instead, it takes advantage of the innate binocular neuroadaptation system in which neuronal gates, when presented with two visual fields from fellow eyes, instantaneously select the better image or elements of each to obtain the most effective single percept.

However, in contrast to traditional monovision, this laser-blended vision procedure results in an overlapping blend zone of vision in the intermediate range, in which both eyes have similar visual acuity that can be fused by the brain. With the laser-blended vision procedure, there is no dissociation between the eyes and much less suppression by the brain is required.

“The ablation profile increases depth of field so that the dominant eye sees best in the mid- to far distance range, and the slightly myopic nondominant eye sees best from near to mid-distance,” he said. “The overlapping blend zone of clear vision and lesser amount of anisometropia distinguish this micro-monovision approach from traditional monovision, in which the depth of field is small, a significant amount of myopia is needed in the nondominant eye and the patient ends up with a middle blur zone.”

The differences also translate into a significant difference in tolerability.

“According to reports in the published literature, between 45% and 60% of patients (at most) are able to tolerate traditional monovision because of the significant anisometropia. In contrast, as we reported in the Journal of Refractive Surgery, we found a tolerance rate of 97% for the micro-monovision procedure in preoperative screening of a series of presbyopic hyperopes,” Prof. Reinstein said.

The ultimate goal is to refine the ablation profile to increase depth of field enough in both eyes so that each achieves clear vision at all distances, he said.

“The current ablation is based on nonlinear aspheric profiles that while effective for increasing depth of field, do not provide clear vision at all distances from far to near. We are not sure that this is achievable without compromising visual quality,” Prof. Reinstein said. “In the meantime, the level of satisfaction among our patients makes us feel like we are on the doorstep of presbyopic patient nirvana.” – by Matt Hasson

References:

• Reinstein DZ, Couch DG, Archer TJ. LASIK for hyperopic astigmatism and presbyopia using micro-monovision with the Carl Zeiss Meditec MEL80 platform. J Refract Surg. 2009;25(1):37-58.
• Reinstein DZ, Archer TJ, Gobbe M. LASIK for the correction of myopic astigmatism and presbyopia using aspheric ablation profiles and a micro-monovision protocol with the Carl Zeiss Meditec MEL80. J Refract Surg. [in press].

• Dan Z. Reinstein, MD, MA(Cantab), FRCSC, FRCOphth, can be reached at London Vision Clinic, 8 Devonshire Place, London W1G 6HP, United Kingdom; 44-20-7224-1005; fax: 44-20-7224-1055; e-mail: dzr@londonvisionclinic.com. Prof. Reinstein is a consultant for Carl Zeiss Meditec.