From the Department of Ophthalmology (SKC, JHK, DL), Ilsan Paik Hospital, Inje University, Kyunggyi-do; and Chung Ang University (NJM), Seoul, Korea.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Doh Lee, MD, PhD, Department of Ophthalmology, Ilsan Paik Hospital, Inje University Medical College, 2240 Dae Wha-dong, Ilsan-ku, Koyang, Kyunggyi-do, 411-706, Korea. E-mail: firstname.lastname@example.org
Superficial corneal irregularities induced by superficial corneal pathologies impair corneal surface smoothness and tear film stability, which in turn affects visual acuity and quality. Corneal surface smoothness is particularly important for visual function in patients undergoing cataract surgery because the intraocular lens (IOL) power is determined using stable keratometric values. Several surgical procedures such as phototherapeutic keratectomy and lamellar keratectomy using a microkeratome have been used to remove superficial corneal irregularities and restore cornea surface smoothness.1–4 Although these methods can repair irregularities, changes in the corneal profile can result in refractive error changes, which can make IOL power calculations difficult.5,6
Femtosecond lasers (IntraLase; AMO, Irvine, CA) can produce corneal flaps of a planar rather than meniscus shape.7 We hypothesized that a planar flap would not alter the corneal profile and that using femtosecond lasers to repair corneal irregularities could result in both corneal clarity and a stable keratometric value.
We describe the successful treatment of a superficial corneal irregularity using a femtosecond laser and the acquisition of a stable keratometric value for cataract surgery by stabilizing the smoothness of the corneal surface.
A 62-year-old man was referred due to decreased visual acuity in the left eye for several decades. His visual acuity was 20/80 (20/80 × uncorrectable) in the left eye and 20/32 (20/20 × +2.0 Ds = −1.5 Dcyl 90°) in the right eye. The left eye had undergone a pterygium excision 1 year prior. Slit-lamp biomicroscopic examination showed cataract opacity and cirrus-like corneal opacity located superficially from the center to the nasal cornea with a 5-mm width. The corneal opacity appeared to originate from a fibrous proliferation associated with the remaining pterygial tissue (Fig. 1A). Cataract surgery and treatment for corneal irregularity was necessary to improve visual acuity. Although autokeratometer (Canon RK-F1 autorefractor; Canon, Inc., Tokyo, Japan) measurement was not possible, corneal topography (Orbscan IIz; Bausch & Lomb, Rochester, NY) showed K1 43.9 D/K2 48.4 D with a skew-deviated oblique axis and severe peripheral irregularity (Fig. 2A).
Figure 1. Case Photographs. (A) Preoperative Photograph Showing Cirrus-Like Cloudy Anterior Corneal Opacity Involving the Pupil Center. (B) When Lifting the Flap, Mild Resistance Was Encountered Beneath the Opaque Area. After Removal of the Corneal Flap, a Slightly Irregular Stromal Surface Was Observed (black Arrows). (C) A Stable and Smooth Corneal Surface Was Observed 2 Months After Lamellar Keratectomy Using a Femtosecond Laser.
Figure 2. Corneal Topography and Histopathology Photograph of the Left Eye. (A) Prior to Femtosecond Laser Flap Creation, the Corneal Topograph Showed a High Level of Corneal Astigmatism and the Inferior Area of the Cornea Was not Assessable Due to Superficial Irregularity in the Eye. (B) Histopathology of the Eye. A Focal Increase in Stromal Fibrosis with Epithelial Atrophy Was Observed. The Thickness of the Resected Cornea Was Uniform Except for the Areas Showing Stromal Fibrosis (hematoxylin–Eosin Stain, Original Magnification × 100). (C and D) Corneal Topography Showed Decreased Peripheral Irregularity and the Difference-Keratoaxial Map Showed the Astigmatism Improved More than 4 Diopters.
The patient underwent diagnostic and therapeutic keratectomy using a femtosecond laser. The surgical procedure was approved by the Institutional Review Board of Inje University and prior informed consent was obtained. The central corneal thickness was 624 mm according to ultrasound pachymetry (Advent; Mentor, Norwell, MA). The planned flap thickness was 100 μm. The surgical parameters for flap creation were: spiral method, 8.3-mm flap diameter, 0.8-mJ bed energy, and 7/7 spot/line separation. Laser emission progressed uneventfully and flap lifting was completed without any major problems, although mild resistance was encountered beneath the opaque area during lifting. After corneal flap removal, the surface of the lamellar cut appeared slightly irregular yet smooth (Fig. 1B). Bandage contact lenses were applied.
Postoperatively, the patient was treated with levofloxacin 0.5% w/v (Cravit; Santen, Osaka, Japan) before epithelial healing. After healing was evident, the patient was prescribed a topical solution of prednisolone 1% w/v (Predforte; Allergan, Inc., Irvine, CA) and levofloxacin 0.5% w/v for 2 weeks. Epithelial healing was complete 7 days after surgery. Slit-lamp biomicroscopic examination at 2 months postoperatively showed a transparent and smooth corneal surface (Fig. 1C). Visual acuity was 20/80 (20/50 × −1.5 Ds = −1.25 Dcyl 180°). The corneal thickness was 544 mm according to ultrasound pachymetry. Histopathological examination of removed corneal disc showed stromal fibrosis with epithelial atrophy (Fig. 2B).
Cataract surgery and IOL (Tecnis ZA9003; AMO) implantation were performed 6 months postoperatively. The keratometric value obtained using an autokeratometer was K1 46.75/K2 47.25. Corneal topography showed K1 47.6 D/K2 48.6 D with decreased peripheral irregularity. A difference-keratoaxial map showed the astigmatism had improved more than 4 diopters (Figs. 2C and 2D). The postoperative visual acuity was 20/32 (20/25 × −1.0 Dcyl 180°).
The success of modern cataract surgery is measured in functional terms. The acquisition of the intended refraction is a critical requirement of successful surgery. However, there are many patients in whom it is difficult to determine IOL power prior to surgery. In patients with corneal surface irregularities who require cataract surgery, the determination of IOL power is extremely difficult due to the unreliability of keratometric values. Although phototherapeutic keratectomy, lamellar keratoplasty, and lamellar keratectomy can be used to repair corneal irregularities and acquire stable keratometric values,1–4 such procedures can result in higher or lower postoperative refractive error and increased difficulty in making IOL power calculations.5,6
Although phototherapeutic keratectomy using excimer lasers has been reported to be successful in treating superficial corneal pathologic conditions,1,3 unwanted refractive errors are often encountered postoperatively. The irregular astigmatism and hyperopic shift of the postoperative refraction has raised concerns due to the different ablation profiles on cornea irregularity.8,9 Recently, lamellar keratectomy using a microkeratome has been considered as an alternative to phototherapeutic keratectomy. However, such procedures have practical limitations due to the prefixed thickness of the keratectomy (160-μm head, Hansatome in our hospital) and biomechanical changes may have caused further thinning of the cornea.
We hypothesized that femtosecond laser-assisted planar-shaped keratectomy may be a successful surgical strategy for treating superficial corneal irregularity. An advantage of this approach is that a precise, uniform, and even-thickness lamellar graft can be created using a femtosecond laser. Furthermore, the surgeon can adjust the lamellar keratectomy depth to the thickness of the lesion. Finally, the contour of the original cornea can be preserved because the shape of the graft is planar rather than a meniscus.
The intended keratectomy thickness was achieved, resulting in total removal of the corneal lesion and a stable keratometric value for cataract surgery. Interestingly, postoperative refraction after lamellar keratectomy using the femtosecond laser was contrary to our expectations. Corneal flaps made using femtosecond lasers are known to have a uniform planar shape.7 Therefore, the effect of femtosecond laser keratectomy on postoperative refraction requires further evaluation. After applying corneal biometry for IOL power calculation, the intended postoperative refraction was achieved in our case.
To our knowledge, this is the first description of the successful use of a femtosecond laser for treating a superficial corneal pathology and acquiring a stable corneal power. The current findings may expand the indications for femtosecond laser use in corneal surgery.
- Moniz N, Fernandez T. Efficacy of phototherapeutic keratectomy in various superficial corneal pathologies. J Refract Surg. 2003;19:S243–S246.
- Alió JL, Javaloy J, Merayo J, Galal A. Automated superficial lamellar keratectomy augmented by excimer laser masked PTK in the management of severe superficial corneal opacities. Br J Ophthalmol. 2004;88:1289–1294. doi:10.1136/bjo.2004.045070 [CrossRef]
- Stewart OG, Morrell AJ. Management of band keratopathy with excimer phototherapeutic keratectomy: visual, refractive, and symptomatic outcome. Eye (Lond.). 2003;17:233–237.
- Dogru M, Katakami C, Miyashita M, et al. Ocular surface changes after excimer laser phototherapeutic keratectomy. Ophthalmology. 2000;107:1144–1152. doi:10.1016/S0161-6420(00)00113-5 [CrossRef]
- Ishikawa T, Hirano A, Inoue J, et al. Trial for new intraocular lens power calculation following phototherapeutic keratectomy. Jpn J Ophthalmol. 2000;44:400–406. doi:10.1016/S0021-5155(00)00170-2 [CrossRef]
- Lee SH, Tsai CY, Liou SW, Tsai RJ, Ho JD. Intraocular lens power calculation after automated lamellar keratoplasty for high myopia. Cornea. 2008;27:1086–1089. doi:10.1097/ICO.0b013e31817c41fc [CrossRef]
- Stahl JE, Durrie DS, Schwendeman FJ, Boghossian AJ. Anterior segment OCT analysis of thin IntraLase femtosecond flaps. J Refract Surg. 2007;23:555–558.
- Campos M, Nielsen S, Szerenyi K, Garbus JJ, McDonnell PJ. Clinical follow-up of phototherapeutic keratectomy for treatment of corneal opacities. Am J Ophthalmol. 1993;115:433–440.
- Gartry D, Kerr Muir M, Marshall J. Excimer laser treatment of corneal surface pathology: a laboratory and clinical study. Br J Ophthalmol. 1991;75:258–269. doi:10.1136/bjo.75.5.258 [CrossRef]