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Refractive surgical problem
consultation section edited by Thomas Kohnen, MD
refractive surgical problem
One and a half years ago, a now 41-year-old female medical technician had attempted bilateral hyperopic laser in situ keratomileusis (LASIK) for ⫹2.50 diopters (D) of symmetrical hyperopia performed elsewhere. Details of her treatment are not available. According to her history, surgery in the first (right) eye was uneventful; however, an incomplete flap was made with the microkeratome in the second (left) eye. No laser treatment was administered to the left eye. Postoperatively, the patient noted intractable glare in the treated right eye. She reports it is impossible to drive at night and she has great difficulty viewing bone-density scans, which is part of her daily work. Since the original surgery, she has worn contact lenses with difficulty in the untreated left eye and has tried several remedies, including pilocarpine, that have helped little or not at all. Uncorrected visual acuity (UCVA) is 20/20 in the right eye and in the left eye. Current refraction is plano and ⫹2.50 D, respectively. Examination of the anterior segments reveals a well-healed LASIK flap in the right eye and an incomplete flap in the left. The hinge is nasally positioned in both eyes, and the flap diameters are relatively small. Other findings are normal bilaterally. Corneal topography (Figure 1) shows evidence of a small treatment zone in the right eye and a normal corneal pattern in the left eye. The scotopic pupil size is 6.5 mm and 7.0 mm, respectively, and central pachymetry, 0.536 mm and 0.555 mm. The thinnest paracentral reading is 0.543 mm in the right eye and 0.586 mm in the left eye. Given the patient’s history and findings, how would you proceed?
f This patient had hyperopic LASIK with a correction of 3.00 to 4.00 D. Because of the ablation profile used, the epithelial healing processes, or both, the treated zone is reduced, leading to a refractive power profile across the pupil. The zone of full correction has a diameter of only 2.0 to 3.0 mm, which is the reason for the significant glare and halos, especially under mesopic conditions. This effect has been well known since the early days of photorefractive keratectomy (PRK), when ablation zones with diameters of 4.0 to 5.0 mm were used. Clearly, the ablation zone in the right eye must be enlarged to 6.0 or 7.0 mm. This would be best
achieved by computer-assisted ablation, either topography guided or wavefront guided. Although a wavefrontguided ablation would be the first choice because of the high spherical aberration and would lead to better reproducible results, I have doubts whether aberrometry will work reliably over a corneal area of 7.0 mm with refractive power differences of 5.00 D and more. Therefore, the surgery would probably have to be performed using a topography-guided ablation. The flap diameter is another concern. The flap must be at least as big as the intended ablation diameter. I recommend a recut rather than a relift LASIK procedure because of the small flap diameters. THEO SEILER, MD, PHD Zurich, Switzerland
f This case raises several questions and observations that must be addressed before proceeding. The first question is which laser and what optical and blend zones were used for the hyperopic LASIK surgery in the right eye? This might be relevant because the patient’s reports of difficulty performing night-related functions could be improved in the second eye if a larger optical zone treatment is performed. In patients with a similar pupil size and hyperopic refraction, we have performed LASIK using the LADARVision laser with a 6.0 mm optical zone and 1.5 mm blend zone to 9.0 mm, with patients reporting no notable night-vision symptoms. This patient’s complaints seem to be rather excessive in light of the well-centered treatment zone noted on corneal topography, which brings us back to the question of the laser delivery and optical zone size used. Second, what percentage of the flap was incomplete as it was being made, and did the blade stop at the very center of the cornea, leading to possible monocular diplopia or polyopia symptoms? If so, this could be the cause of the symptoms disturbing the patient’s overall vision, even with the use of a contact lens in the left eye. Our recommendation is based on the following observations: The patient has a well-centered topographic
J CATARACT REFRACT SURG—VOL 27, MAY 2001
653
refractive surgical problem
One and a half years ago, a now 41-year-old female medical technician had attempted bilateral hyperopic laser in situ keratomileusis (LASIK) for ⫹2.50 diopters (D) of symmetrical hyperopia performed elsewhere. Details of her treatment are not available. According to her history, surgery in the first (right) eye was uneventful; however, an incomplete flap was made with the microkeratome in the second (left) eye. No laser treatment was administered to the left eye. Postoperatively, the patient noted intractable glare in the treated right eye. She reports it is impossible to drive at night and she has great difficulty viewing bone-density scans, which is part of her daily work. Since the original surgery, she has worn contact lenses with difficulty in the untreated left eye and has tried several remedies, including pilocarpine, that have helped little or not at all. Uncorrected visual acuity (UCVA) is 20/20 in the right eye and in the left eye. Current refraction is plano and ⫹2.50 D, respectively. Examination of the anterior segments reveals a well-healed LASIK flap in the right eye and an incomplete flap in the left. The hinge is nasally positioned in both eyes, and the flap diameters are relatively small. Other findings are normal bilaterally. Corneal topography (Figure 1) shows evidence of a small treatment zone in the right eye and a normal corneal pattern in the left eye. The scotopic pupil size is 6.5 mm and 7.0 mm, respectively, and central pachymetry, 0.536 mm and 0.555 mm. The thinnest paracentral reading is 0.543 mm in the right eye and 0.586 mm in the left eye. Given the patient’s history and findings, how would you proceed?
f This patient had hyperopic LASIK with a correction of 3.00 to 4.00 D. Because of the ablation profile used, the epithelial healing processes, or both, the treated zone is reduced, leading to a refractive power profile across the pupil. The zone of full correction has a diameter of only 2.0 to 3.0 mm, which is the reason for the significant glare and halos, especially under mesopic conditions. This effect has been well known since the early days of photorefractive keratectomy (PRK), when ablation zones with diameters of 4.0 to 5.0 mm were used. Clearly, the ablation zone in the right eye must be enlarged to 6.0 or 7.0 mm. This would be best
achieved by computer-assisted ablation, either topography guided or wavefront guided. Although a wavefrontguided ablation would be the first choice because of the high spherical aberration and would lead to better reproducible results, I have doubts whether aberrometry will work reliably over a corneal area of 7.0 mm with refractive power differences of 5.00 D and more. Therefore, the surgery would probably have to be performed using a topography-guided ablation. The flap diameter is another concern. The flap must be at least as big as the intended ablation diameter. I recommend a recut rather than a relift LASIK procedure because of the small flap diameters. THEO SEILER, MD, PHD Zurich, Switzerland
f This case raises several questions and observations that must be addressed before proceeding. The first question is which laser and what optical and blend zones were used for the hyperopic LASIK surgery in the right eye? This might be relevant because the patient’s reports of difficulty performing night-related functions could be improved in the second eye if a larger optical zone treatment is performed. In patients with a similar pupil size and hyperopic refraction, we have performed LASIK using the LADARVision laser with a 6.0 mm optical zone and 1.5 mm blend zone to 9.0 mm, with patients reporting no notable night-vision symptoms. This patient’s complaints seem to be rather excessive in light of the well-centered treatment zone noted on corneal topography, which brings us back to the question of the laser delivery and optical zone size used. Second, what percentage of the flap was incomplete as it was being made, and did the blade stop at the very center of the cornea, leading to possible monocular diplopia or polyopia symptoms? If so, this could be the cause of the symptoms disturbing the patient’s overall vision, even with the use of a contact lens in the left eye. Our recommendation is based on the following observations: The patient has a well-centered topographic
J CATARACT REFRACT SURG—VOL 27, MAY 2001
653