Surgical Correction of a High Bilateral Primary Compound Astigmatism
A female patient was referred to us on Sept. 28 2004 for the surgical management of a very high primary compound astigmatism. Her subjective and manifest refraction was +5.50 -8.00 X 10º 20/40 OD and +6.25 -8.75 X 0º 20/50 OS. Low contrast sensitivity (10%) was 20/60 in both eyes, and her UCVA was 20/200 in both eyes. Ultrasound central pachymetry was performed, revealing 535 µm OD and 531 µm OS. Slit-lamp and fundus examination did not reveal any remarkable feature, other than a small optic nerve head (Figure 1).
Elevation topography (Orbscan; Bausch & Lomb, Rochester, NY) showed a perfectly symmetrical cornea with a high degree of toricity, but no presumptive sign of forme fruste keratoconus. Wavefront aberrometry (Zywave; Bausch & Lomb) showed that the mesopic pupil was 5.4 mm in both eyes (Figure 2).
A sequential approach using automated arcuate relaxing incisions followed by wavefront-guided LASIK was recommended to attempt a surgical correction of this unusually high degree of astigmatism. A pair of automated arcuate relaxing incisions using the Hanna arcuate keratome (Moria, Paris) were made on the left and right eyes, at 1 week interval using submaximum parameters: optical zone 6 mm, arcuate length 90º, incision depth 500 µm (day 0).
One week after the arcuate incisions were made, the patient's manifest refraction was -0.50 +3.00 X 95º 20/30 OD and +1.25 +2.50 X 85º 20/50 OS. Low contrast sensitivity (10%) was 20/60 in both eyes. UCVA was 20/50 OD and 20/60 OS.
Lasik Performed
Bilateral wavefront-based LASIK (Zywave) was then performed 6 weeks later, using a 180-µm, 9.5-mm Hansatome (Bausch & Lomb) microkeratome and a 217 Z Technolas Zytoptix System excimer laser (Bausch & Lomb). The optical zone was 6 mm; flap lifting was not difficult, except for a partial disjunction of the arcuate incisions.
At 1 week following wavefront-guided LASIK, the patient's manifest refraction was +1.00 +0.50 X 55º 20/25 OD and +1.00 +1.00 X 65º 20/25 OS. Low contrast sensitivity (10%) was 20/50 and UCVA was 20/50 in both eyes. The residual central pachymetry was 541 µm OD and 535 µm OS.
Progressive Recurrence
Progressive recurrence was observed over the follow-up. At 11 months after wavefront-guided LASIK, manifest refraction was +0.75 +2.25 X 100º 20/30 OD and +1.00 +2.75 X 85º 20/30 OS. Low contrast sensitivity (10%) was 20/50 in both eyes. UCVA was 20/60 in both eyes (Figures 3,4).
A wavefront-based LASIK enhancement was performed 12 months after the initial surgery on the left eye and right eye at 1-week intervals. We used the Zyoptix 100 excimer laser with iris-recognition alignment and multidimensional eye tracker. Flap lifting was more difficult and required a careful dissection of the arcuate incisions' scars.
At 1 week following wavefront-guided LASIK enhancement, the patient's manifest refraction was -0.25 -0.50 X 100º 20/30 OD and +0.00 -0.25 X 65º 20/30 OS. Low contrast sensitivity (10%) was 20/50 in both eyes. UCVA was 20/30 in both eyes. This patient's outcome was stable at 2 months, and manifest refraction was -0.25 -0.25 X 100º 20/30 OD and +0.00 -0.00 X 0º 20/30 OS. Low contrast sensitivity (10%) was 20/50 in both eyes. UCVA was 20/25 in both eyes (Figures 5,6).
Discussion
This case report may help demonstrate that a sequential approach — using synergic methods — can successfully correct unusually high degrees of compound astigmatism. Combining relaxing incisions and LASIK was previously reported for astigmatism up to 4.00 D,1 6.00 D2 and 8.00 D.3 Automated arcuate relaxing incisions can reduce total cylinder without affecting spherical equivalent due to a coupling effect. Their efficacy, however, is limited to 4.00 D to 5.00 D of cylinder, and they tend to induce a significant amount of trefoil (as in this case) or coma when not properly aligned (Figure 7).
We subsequently treated residual cylinder and induced trefoil by wavefront-guided LASIK (Figures 8,9). The first attempt was partially successful, and a near-perfect outcome was obtained after a wavefront-guided iris-recognition-aligned enhancement procedure in both eyes.
Proper iris registration, prior to wavefront-guided corneal ablation, is essential for proper correction of astigmatism and higher-order aberrations to achieve optimal visual outcomes. Alternate surgical management of a very high degree of compound astigmatism may comprise more complex and often less predictable methods such as wedge resection, toric phakic or aphakic IOLs.
Michael Assouline, MD, is in practice at the Clinique de La Vision, in Paris. Dr. Assouline is a consultant for Bausch & Lomb and has no direct financial interest in the company or products mentioned in this article. He is a member of the CRSToday Europe Editorial Board. He may be reached at ma@inclo.com or +33 1 45 56 92 92.
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