Refractive surgeons desire a microkeratome that is capable of creating predictable flap thicknesses with few potential risks. The Rondo microkeratome (WaveLight AG, Erlangen, Germany) enhances refractive surgery outcomes with its ability to vary hinge position and hinge size. Surgeons can create flap thicknesses of 100, 130, and 150 µm with flap diameters ranging from 8 to 10 mm (Table 1).

Recently, I evaluated the predictability of the resultant flaps and subsequent visual outcomes with the Rondo in a prospective, open-label case series of 95 eyes (75 myopic and 20 hyperopic) conducted at the Wellington Eye Clinic in Dublin, Ireland. I performed all LASIK cases, most of which were bilateral, over 5 days in October and November 2007.

METHODOLOGY AND EQUIPMENT
Prior to the microkeratome pass, I lubricated the corneal surface with Vismed (TRB Chemedica International SA, Geneva, Switzerland), a primarily methylcellulose viscous tear solution, or sterile water. Directly after making the flap cut, I measured the flap thickness (Sonomed Micropach P200+ ultrasound pachymeter; Sonomed, Inc., Lake Success, New York) by deducting the thickness of the remaining stromal bed from the preoperative measurement. Pachymetry measurements were taken until three readings were within 10 µm of one another; the average of these three measurements was recorded.

Patients were evaluated preoperatively, on day 1, and at 6 weeks postoperatively. The UCVA, BCVA, and manifest refraction were evaluated, and biomicroscopy was performed. Patients were questioned about dry eye symptoms, including foreign body sensation, itching, redness, excessive watering, and an actual feeling of dryness.

RESULTS
I created 84 flaps using the 130-µm head (Figure 1). When performing bilateral LASIK, I cut the right eye flap first and used the same blade on the left eye. The average flap thickness of the first and second flap cuts and the entire group was 128 µm (standard deviation [SD], 23.9 µm; range, 73-170 µm), 104 µm (SD, 16.1 µm; range, 73–136 µm), and 116 µm (SD, 23.8 µm), respectively.

Preoperative pachymetry readings can significantly influence the subsequent flap thickness; if the reading was between 500 and 640 µm, the average flap thickness for the first flap was 140 µm (range, 112–157 µm). For the second flap, the thickness ranged from 93 to 123 µm (Figure 2).

I also evaluated the 100-µm head, which I used to create 11 flaps. The average flap thickness of the first and second flap cut was 104 µm (SD, 17 µm; range 73–119) and 85 µm (SD, 10 µm; range, 72–100 µm), respectively.

The difference in flap diameter between flaps made with the 130- and 100-µm head was not statistically significant. The average resultant flap diameter was 9.3 mm (SD, 0.2 mm; range, 8.9–9.7 mm), and the average hinge size was 4.9 mm (range, 3–5.6 mm), depending on the intended hinge size and the achieved flap diameter.

At 6 weeks postoperative, BCVA slightly improved from the preoperative level (20/13 vs 20/17, respectively) when Vismed was used (Figure 3); however pre- and postoperative BCVA levels were similar in the sterile water group (20/17 vs 20/18, respectively). The average postoperative UCVA in both groups was approximately the same as it was preoperatively (Figure 4).

At 6-week follow-up, 19.1% of myopic and 18.2% of hyperopic patients in whom Vismed was used complained of symptoms of dryness. In contrast, 14.8% of myopes and 87.5% of hyperopes treated with sterile water reported dryness. No case of superficial punctate keratitis was higher than grade 2 in severity.

CORNEAL FINDINGS
The Rondo microkeratome created a smooth stromal bed with well-delineated flap edges (Figure 5). I observed very fine microstriae in the periphery near the flap edges, which is possibly a result of the smooth stromal bed. At 6 weeks, microstriae were detected in 13 of 74 myopic eyes, two of which gained two lines of BCVA, one of which lost one line of BCVA, and one of which lost two lines of BCVA. Microstriae were also observed in 4 of 19 hyperopic eyes. Of these cases, one lost one line of BCVA, one lost two lines of BCVA, and two remained unchanged from preoperative levels. Although I was concerned by the development of the microstriae, I was impressed with the excellent visual outcomes of these patients. No adverse events, including aborted procedures, epithelial defects, or buttonhole flaps were encountered with the use of this device.

Microstriae were graded on a scale of 1 to 4, with grade 1 demonstrating visibility on only retroillumination and grade 4 being sufficiently severe to require the flap to be refloated. All microstriae observed were grade 2 or less.

DISTINCTIONS
The Rondo microkeratome has precise centration. Once locked onto the cornea, it is unlikely to move, facilitating precise and centered flaps. If the surgeon wants a decentered flap (eg, during topography-guided ablation), this device is unlikely to drift from its placement.

Once the suction ring is in place, the microkeratome is the only surface that touches the eye because of the ring's elevated surface and active vacuum adjustment. This setup contrasts to other units that may allow extraneous objects, such as the draping, tape, speculum, lids, and lashes to interfere with the function of the microkeratome.

The Rondo can fit into tighter orbital structures, such as in patients with tight eyelids. It also operates quietly, making the procedure more comfortable for the patient and surgeon. Perhaps most important, however, is that the blade of the injector is inserted and removed using the same device; in other systems, manual insertion of the blade may result in inadvertent blade damage. Surgeons never need to physically touch the blade, and the injector is easy to handle.

Additionally, this microkeratome is preassembled for faster application onto the eye. With other microkeratomes, one must place the suction ring on the eye before dropping the microkeratome onto the suction ring.

CONCLUSION
The predictably of flap thickness is an important factor in achieving an adequate post-LASIK residual bed. It is also imperative to avoid creating a flap that is too superficial, which may result in a buttonhole, or too thick, which may weaken corneal tectonic stability. In cases in which a thinner flap is required, the precise oscillating cutter can cut an ultrathin flap.

This device, more than any other microkeratome that I have used, accomplishes what it was intended to do. Although I observed a slightly higher incidence of microstriae than with other microkeratomes, they were minimal and did not appear to affect visual outcomes. In my view, the presence of microstriae outside the visual axis was a small price to pay for outstanding quality of vision, improved safety, consistent flap thickness, and a low incidence of dry eye. Safety, quietness, and accuracy were the salient features making this microkeratome, in my opinion, a stellar product.

Arthur Cummings, FRCS(Ed), is the Medical Director of the Wellington Eye Clinic, Dublin, Ireland. Mr. Cummings states that he is an investigator and member of the beta-site group for WaveLight AG. He is a member of the CRST Europe Editorial Board. Mr. Cummings may be reached at tel: +353 1 2930470; E-mail: abc@wellingtoneyeclinic.com.