Refractive treatment shows stable results in well-selected patients at 2 years

Approximately 80% of patients could read without spectacles after treatment.

A refractive treatment shows good, stable results at 2 years, according to a surgeon.

IntraCor intrastromal femtosecond laser (Technolas Perfect Vision) is a corneal refractive procedure with the unique feature of being totally intrastromal. No incision is required: The femtosecond laser is focused on the stroma and performs five consecutive concentric cylindrical cuts from the center to the periphery. The inner cut diameter is approximately 1.8 mm. The depth of the intrastromal cuts is based on preoperative pachymetry.

“The effect is a gentle change in corneal curvature, with the central cornea becoming slightly steeper. It is a safe and easy procedure that only lasts 15 to 20 seconds. It is minimally invasive, and 24 months postoperatively it is really difficult to see those rings in the cornea,” Mike P. Holzer, MD, said at the winter meeting of the European Society of Cataract and Refractive Surgeons in Istanbul.

The procedure is performed only in the nondominant eye to improve near vision.

“We have treated more than 200 eyes in our center, and we are looking now at the 25 patients with 2-year follow-up data,” Prof. Holzer said.

A mean gain of five to six lines of uncorrected near vision and four to five lines of distance-corrected near vision was reported, with stability at 2 years. Approximately 80% of patients were able to read without spectacles. Reading acuity significantly improved and reading speed was unchanged, but for reading a much smaller letter size.

Intermediate vision at 80 cm, the average distance for computer work, also improved significantly. At 2 years, the treated eye had a median acuity of 20/25 compared to 20/40 in the untreated eye.

At distance, all patients achieved 20/30 or better, but some patients lost lines, usually one line.

“This is a little compromise that needs to be discussed with patients preoperatively,” Prof. Holzer said.

Pentacam (Oculus) measurements showed corneal asphericity changes, with a slightly more negative Q value. Wavefront measurements showed reduction of spherical aberration and some changes in coma.

“Straylight measurements were also performed, because we induce changes in the cornea, and the rings might cause some halo effect,” Prof. Holzer said. “We did not find any significant difference between preoperative and postoperative values, and this is a very important finding. Some patients report seeing little rings around light sources sometimes, but they don’t seem to be disturbed and this effect diminishes over time.”

No changes in endothelial cell count were seen over the 2-year period.

No refractive surprises

If IntraCor patients need cataract surgery later in life, no problems should arise with IOL power calculation.

“We were wondering whether we should expect refractive surprises in case of cataract surgery, and whether we might need some adjusting factor for IOL power calculation in these patients, as we need after LASIK and other refractive laser procedures,” Prof. Holzer said.

IOLMaster (Carl Zeiss Meditec) biometry was performed preoperatively and 1 year postoperatively in the study’s 25 patients. Results were compared with those obtained via clinical history.

“For the clinical history method, we need stable postop outcomes and we need the [keratometry] values preop and postop as well as the spherical equivalent. By looking back at our data, we found that after IntraCor, we had a change in spherical equivalent by roughly 0.5 D and significant changes in the keratometry reading. That was important to know, as we concluded that we can’t use the IOLMaster preop as a valid parameter,” Prof. Holzer said.

“But if you look at the IOLMaster postop and at the clinical history method, there is no significant difference. With all different formulas — Haigis, Hoffer Q, Holladay and SRKT — the difference was roughly 0.25 D. This allows us to conclude that biometry should be performed postop and that we do not need adjusting factors for IOL calculation,” he said.

In practice, this was seen in one patient who developed subcapsular cataract in the 9 months after IntraCor. IOL power calculation was performed using IOLMaster biometry and the clinical history method. A monofocal IOL was implanted and perfect emmetropia was achieved at 1 month postop.

Patient selection

Chair time and careful patient selection are crucial to the success of IntraCor, Prof. Holzer said.

Good candidates have at least +1.5 D of near add and are slightly hyperopic, between +0.5 and +1.25 D of spherical equivalent. The subjective astigmatism should not be more than 0.5 D, increasing to 1.5 D on topography. Corneal pachymetry should be at least 480 µm.

Patients should be told what to expect.

“Using reading charts, we show patients preoperatively what they can expect. Of course, if they have a very low near acuity, the four to five lines improvement will not be sufficient to achieve reading size without spectacles, and they should know this in advance,” Prof. Holzer said. “They should also know that there will be a slight loss of about one line of distance vision. Again, we test them on this preoperatively so that they can decide whether they can accept it or not.”

Prof. Holzer said he tries to choose patients who have uncorrected distance vision around 20/30 or lower and exclude patients with 20/20 because they are used to sharp vision and would be disappointed with the loss they would experience after surgery.

“No other method offers the same results in a similarly nontraumatic, minimally invasive way, with practically no risk of infection and a fast and painless recovery time,” Prof. Holzer said. – by Michela Cimberle

• Mike P. Holzer, MD, can be reached at International Vision Correction Research Centre, University of Heidelberg, Department of Ophthalmology, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany; +49-6221-566695; fax: +49-6221-565308; email: mike.holzer@med.uni-heidelberg.de.
• Disclosure: Prof. Holzer receives consulting fees from Technolas Perfect Vision.