Management of myopic shift and central corneal steepening resulting from superficial corneal opacity in a patient with previous radial keratotomy: a case report

Abstract

Purpose

The purpose of this study was to report a patient who developed myopic shift and anterior corneal steepening many years following radial keratotomy (RK). The etiology of this myopic shift resulted from central corneal opacity and was successfully managed with supra-stromal keratectomy.

Case presentation

A 59-year-old woman with a history of radial keratotomy and cataract surgery presented with blurred vision and ocular irritation in both eyes for years. Poor visual acuity and myopic change to -7.0 D were noted upon initial evaluation. Further ophthalmic examination revealed central corneal opacity occupying the optical axis with steepening of the anterior corneal surface. Anterior segment optical coherence tomography (ASOCT) revealed superficial corneal opacity with minimal stromal scarring. The opacity was successfully removed via supra-stromal keratectomy. After surgery, the patient’s visual acuity improved, and refraction returned to nearly plano. Postoperative corneal topography revealed flattening of the central cornea in both eyes.

Conclusion

Late-onset central corneal steepening with myopic shift following RK may be a sign of corneal ectasia disorders such as keratoconus. It is important to recognize corneal opacity as a distinct etiology of central corneal steepening, which may mimic corneal ectasia. A comprehensive evaluation of patients with corneal topography and ASOCT may reveal the etiology of central corneal steepening and further guide treatment decisions.

Introduction

Radial keratotomy (RK) for myopia involves making deep, radial corneal stroma incisions to weaken the paracentral and peripheral cornea and flatten the central cornea. It has been associated with various complications and is therefore largely replaced by newer excimer laser procedures [1]. Central corneal steepening following RK has rarely been reported and typically results from keratoconus [2] Here, we report a patient who presented with central corneal steepening and myopic shift but not keratoconus. The cornea flattened following a certain procedure.

Method

Patient data was obtained from the medical records at our hospital, following confirmation of the patient’s written informed consent for the publication of this case report and associated images. A comprehensive literature review was conducted using PubMed, Medline and Embase. The objective of the literature search was to explore potential etiologies for late-onset myopic shift in patients who have undergone radial keratotomy, as well as to investigate the possible pathogenesis of corneal opacity. The search terms included: corneal steepening, corneal ectasia, myopia, myopic shift, myopic change, corneal opacity, deposition, dystrophy, keloid, radial keratotomy, refractive surgery, LASIK, photorefractive keratectomy, and phototherapeutic keratectomy.

Results

A 59-year-old woman who initially presented to our outpatient department with blurred vision and ocular irritation in both eyes for many years. She had undergone RK many years prior and cataract surgery 3 years prior. Her self-reported refractions before RK were approximately − 10.0 diopters in both eyes. She denied any previous medical history. The patient’s uncorrected visual acuity was 6/60 in the right eye and 6/30 in the left eye, whereas best-corrected visual acuity was 6/15 in the right eye and 6/20 in the left eye. The refractions of the patient were − 7.25–1.75 × 3 in the right eye and − 4.00–1.50 × 165 in the left eye. The intraocular pressures were 16 mm Hg and 14 mm Hg in the right and left eyes, respectively. Ophthalmic examination revealed round central corneal opacity occupying the optical axes of both eyes. (Fig. 1A, B) Corneal topography revealed central steepening of the anterior corneal surface, with mean keratometry at 44.8 diopters in the right eye and 42.7 diopters in the left eye. (Fig. 1C, D) The central corneal thickness was 632 micrometers in the right eye and 609 micrometers in the left eye. Anterior segment optical coherence tomography (ASOCT) revealed mound-shaped, hyperreflective materials, with minimal stromal scarring in both eyes. The lesion in the right eye had a thickness of 89 μm, a depth of 136 μm, and a width of 272 μm, whereas the lesion in the left eye had a thickness of 61 μm, a depth of 119 μm, and a width of 368 μm. (Fig. 1E, F) After application of 20% alcohol onto the cornea for 15 seconds, the corneal epithelium was removed exposing the underlying opacity. The corneal opacity was thereby pried away from the corneal stromal, by attacking the edge of the opacity using the tip of dry Weck-Cel sponge., instead of a blade. (Fig. 2A, B) No further cutting techniques were employed. Postoperative uncorrected and best-corrected visual acuity improved to 6/8.6 in both the right and left eyes. Refractions were + 1.75–2.00 × 4 in the right eye and − 1.50–2.00 × 72 in the left eye. Compared to the preoperative imaging, postoperative corneal topography confirmed flattening of the central cornea in both eyes (Fig. 2C, D), while the mound-shaped hyperreflective material was diminished on the postoperative ASOCT of both eyes. (Fig. 2E, F) The patient was satisfied with the postoperative outcome.

Fig. 1

External corneal photography, axial map and ASOCT of the preoperative corneal condition. Figure 1A and B present preoperative photographs of the right and left eyes, respectively, with a whitish central opacity obscuring the visual axis in both eyes. Figure 1C and D display preoperative axial maps of the right and left eyes, respectively. Central steepening of the anterior corneal surface is observed in both eyes, with mean keratometry values of 44.8 diopters in the right eye and 42.7 diopters in the left eye. Preoperative ASOCT images of the right eye (1E) and the left eye (1 F) revealed mound-shaped hyperreflective material in the subepithelial space, with minimal stromal scarring. The lesion in the right eye measured 89 μm in thickness, 136 μm in depth, and 272 μm in width, while the lesion in the left eye measured 61 μm in thickness, 119 μm in depth, and 368 μm in width

Fig. 2

External corneal photography, axial map and ASOCT of the postoperative corneal condition. Figure 2A and B present postoperative photographs of the right and left eyes, respectively, demonstrating the successful removal of the whitish opacities previously noted in both eyes. These findings are further corroborated by postoperative ASOCT images of the right eye (2E) and left eye (2F), which reveal the complete removal of the supra-stromal deposits in both eyes, with a hyperreflective band outlining the surgical depth of the debridement. Figure 2C and D show postoperative axial maps of the right and left eyes, respectively. The central cornea in both eyes was flattened, with mean keratometry values decreasing to 40.5 D in the right eye and 36.2 D in the left eye

Discussion

Central corneal steepening is a rarely reported complication following RK, as RK typically results in long-term hyperopic shift according to the PERK study [1]. Biomechanical studies from the RK recipient cohort demonstrated long-term flattening of the central cornea and steepening of the mid-periphery following RK [3]. Transient central corneal steepening may occur transiently soon after RK and is thought to occur owing to local swelling at the mid-periphery [3, 4].

Late-onset central corneal steepening has rarely been reported after RK. The commonly reported etiologies for central corneal steepening include keratoconus and postrefractive surgery ectasia [2, 5]. Post-RK ectasia usually results from steepening from weakening previous radial incisions at the mid-periphery and contributes to steepening at the mid-peripheral cornea and a hyperopic shift [5]. Post-RK keratoconus with myopic shift and central steepening has also been reported, but its incidence is far lower than that of hyperopic-shift corneal ectasia [2, 6]. Our patient demonstrated progressive steepening of the central cornea, yet the central corneal thickness remained within the normal range. There were also no other characteristic signs of keratoconus, including inferior steepening, which makes the diagnosis unlikely [7]. Although the area of the opacity is limited, it steepens the anterior corneal curvature, resulting in myopic changes in this patient. Corneal flattening and resolution of the myopic change in this patient after suprastromal keratectomy suggest that opacity may be the cause of the myopic change.

The exact pathology of this opacity remains unknown. Possible etiologies include corneal scarring, corneal dystrophy, fibrovascular pannus, Salzmann nodular degeneration, and corneal keloid [8]. Most reported corneal opacity is associated with deep stromal scarring and is eventually treated with anterior lamellar keratoplasty (ALK) or penetrating keratoplasty [8, 9]. ASOCT revealed minimal stromal scarring in our patient, which made the patient suitable for removing the opacity with suprastromal keratectomy. Based on our literature review, this approach for managing superficial corneal opacity following RK has not been previously described in the literature. Successful removal of the opacity with such surgical technique implies that the pathology was located superficial to corneal stroma.

In our case report, we reported a rare etiology of central corneal steepening following RK and also provide an unreported surgical technique in managing such complication. Our case illustrates the resolution of central steepening and myopic shifts following suprastromal keratectomy, suggesting that the opacity may be the primary cause of these refractive changes. This finding supports the hypothesis that central corneal steepening, in the absence of other signs of ectasia, such as corneal thinning, may indicate an alternative etiology rather than a corneal ectasia disorder. However, the management of superficial corneal opacity depends not only on findings from ASOCT and corneal topography but also on the clinical history, in order to determine the nature of the opacity. Reported treatment modalities for superficial corneal keratectomy include anterior lamellar keratectomy, phototherapeutic keratectomy, and superficial keratectomy [10]. Riedl et al. demonstrated improvements in total refractive error and corneal astigmatism in patients with peripheral hypertrophic subepithelial corneal opacifications following superficial keratectomy [11]. It is prudent to tailor treatment planning for superficial corneal opacities according to the findings of clinical history, ASOCT, and corneal topography.

Although RK is an obsolete surgery and is largely replaced by laser refractive surgery, complications following surgery still occur. In this case report, we describe a rare etiology causing corneal steepening and myopic change, distinct from corneal ectasia, and yet to be reported in previous literature. A thorough evaluation of ASOCT and corneal topography can aid in refining the surgical approach for the management of various superficial corneal opacities.