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Sir,

The complications of a laser in situ keratomileusis (LASIK) were reported (5.2%) to include the following: flap irregularities, free cap formation, diffuse lamellar keratitis, epithelial ingrowth, induced astigmatism, regression, and overcorrection.1, 2 Progression of a visual field defect is also reported after LASIK.3, 4, 5, 6 Here, I report a case of progression in a visual field defect after LASIK.

Case report

A 34-year-old man visited a local facility of a laser visual correction centre in February of 2001. Preoperative evaluation revealed that his best-corrected visual acuity was 20/12.5 in both eyes, with −9.00 −0.75 × 5 in the right eye and –8.50 –0.75 × 180 in the left. The corneal curvatures were 42.25/43.25 D in both eyes. The central corneal thickness was 577 μm and 578 μm in the right and left eye, respectively. The intraocular pressure measured by Goldmann applanation tonometry was 13 and 11 mmHg in the right and left eye, respectively. The vertical cup/disc ratio was 0.7 in both eyes. The Humphrey visual field study (30-2 SITA-Fast program) disclosed a superior nasal step defect in both eyes (Figure 1). The mean deviation was −4.97 and −3.20 dB in the right and left eye, respectively. Bilateral normal-tension glaucoma was diagnosed at that time. He went ahead with a bilateral LASIK procedure using the EC-5000 excimer laser (Nidek, Japan) with an MK-2000 microkeratome (Nidek, Japan). A 9.0-mm-diameter corneal flap, 112 μm thick, was fashioned, and a 6.5-mm ablation zone of 127 μm in central depth in the right eye and 114 μm in the left was performed. At 13 months after LASIK, the intraocular pressure was 5 and 4 mmHg in the right and left eye, respectively. The mean deviation of the Humphrey visual field study was –11.27 and –5.87 dB in the right and left eye, respectively. He was referred to us at the glaucoma centre of Inouye Eye Hospital due to a progression in his visual field defect in both eyes.

Figure 1
figure 1

Humphrey 30-2 visual field of each eye before LASIK. The Japanese terms in this figure are equivalent to the English terms in Figure 2.

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Uncorrected visual acuity of the right and left eyes, at that time, was 20/16 and 20/20. The intraocular pressure measured by Goldmann applanation tonometry was 6 and 7 mmHg in the right and left eye, respectively. The corneal curvatures were 36.00/37.00D in both eyes. The corneal thickness was 466 and 465 μm in the right and left eye, respectively. Corneas were clear. A fundoscopic examination revealed a vertical cup/disc ratio of 0.8 in both eyes. The Humphrey visual field study (30-2 SITA-Fast program) revealed a worsening of glaucomatous changes in both eyes (Figure 2). The mean deviation was –11.78 and –8.77 dB in the right and left eye, respectively. At 22 months after LASIK, the intraocular pressure was increased to 12 and 8 mmHg in the right and left eye, respectively. The mean deviation of the Humphrey visual field study was –10.35 and –5.61 dB in the right and left eye, respectively. Topical latanoprost once daily was started in both eyes. Computed tomography of the head was within a normal limit.

Figure 2
figure 2

Humphrey 30-2 visual field of each eye 19 months after LASIK.

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Comment

As for glaucoma development associated with LASIK, there are several reports of secondary steroid-induced glaucoma.3, 4 However, it is thought that the risk factor for progression of a visual field defect is not only due to long-term corticosteroid use, but also related to family history and the presence of ocular hypertension preoperatively.5, 6 For example, Bushley et al5 report that a woman with a family history of normal-tension glaucoma developed a visual field defect after LASIK. Weiss et al6 report that a woman with ocular hypertension and a family history of glaucoma developed a scotoma in a superior temporal of the visual field after LASIK. To date, there are no reports of progression of a visual field defect in pre-existing normal-tension glaucoma after LASIK without any evidence of a long-term treatment with corticosteroid. The reason why the man experienced progression of glaucoma may be associated with a procedure performed during LASIK and/or natural progression of normal-tension glaucoma. There is a step where a large pressure at a minimum of 65 mmHg is exerted during corneal flap formation.1 Although the results of the Humphrey visual field study were variable, those after LASIK were worsen than those before LASIK. LASIK should be carefully performed in patients with glaucoma, especially for those with normal-tension glaucoma, since their optic nerve head may be more vulnerable against increase of intraocular pressure.