Topography-guided photorefractive keratectomy (PRK) combined with corneal cross-linking is one way to partially correct irregular astigmatism in patients with keratoconus and with acceptable outcomes.1 However, some complications may occur.2,3 We describe a case of deep, stromal scarring with loss of visual acuity that has persisted for 2 years despite intensive topical steroid therapy.
A 22-year-old man expressed interest in undergoing refractive surgery. Uncorrected visual acuity was 20/30 for the right eye and corrected distance visual acuity was 20/20 with −1.00 × 105° −0.5 diopters (D). The uncorrected visual acuity was 20/40 (corrected: 20/20 with 1.25 × 80° −0.25 D) for the left eye.
During initial ophthalmological examination, a clear cornea was observed. However, there was also a discreet thinning of the cornea center. The Orbscan Corneal Topographer (Orbtek, Inc., Salt Lake City, UT) showed an altered keratometric map and a decrease in pachymetric central thickness in both eyes (right eye: 492 μm; left eye: 501 μm); this led to diagnosis of forme fruste keratoconus (Figure 1A).
(A) Preoperative Orbscan corneal topography (Orbtek, Inc., Salt Lake City, UT) showed an altered keratometric map and a decrease in pachymetric central thickness in the right eye (492 μm); this led to a diagnosis of forme fruste keratoconus. (B) Five-month postoperative Orbscan corneal topography.
To treat this condition, it was decided to correct the refractive error without inducing biomechanical destabilization. Therefore, both PRK and corneal cross-linking were performed during the same surgery. The patient signed the proper consent form.
This technique consists of performing PRK after corneal de-epithelization with a topography-guided excimer laser (Zeiss MEL 80; Carl Zeiss Meditec, Inc., Jena, Germany) and subsequently performing corneal cross-linking with the Vega X Linker (Oftaltech, Madrid, Spain). Equipment was calibrated with power between 2.75 and 3.00 mW/cm2. Riboflavin 0.1% (10 mg riboflavin-5-phosphate plus 20% dextrane-T-500 in 10 mL) eye drops were applied for 20 minutes until the cornea was completely impregnated. Five 5-minute cycles of ultraviolet radiation were applied and one drop of riboflavin solution was instilled every 5 minutes. Postoperatively, a therapeutic contact lens was placed on the eye and tobramycin drops and preservative-free artificial tears were prescribed. The left eye was operated on 2 weeks after operating on the right eye. No complications occurred.
One week after surgery, the therapeutic contact lens was removed and tobramycin and dexamethasone four times per day, artificial tears, and dexamethasone ointment were initiated at night for 3 weeks. One month after surgery, uncorrected visual acuity was 20/20 in both eyes and the cornea was clear and did not present signs of inflammation. Fluorometholone (in decreasing dosages) was prescribed for 6 weeks.
At the 5-month follow-up, the patient reported poor vision in the right eye; uncorrected visual acuity was 20/25 and did not improve with correction. A circumscribed and dense, deep posterior stromal haze with no keratic precipitates was observed (Figure 2). Fluorometholone eye drops were prescribed every other day for 3 weeks and corneal alteration uncorrected visual acuity improved to 20/20.
Five-month postoperative anterior segment of the right eye with a circumscribed, dense, posterior, deep stromal haze in the cornea. No keratic precipitates are observed.
Four months after surgery, uncorrected visual acuity in the right eye decreased to 20/80 and corrected distance visual acuity with +2.00 was 20/25. A deep, stromal focal plaque with mild stromal edema and central flattening was observed. Using anterior segment optical coherence tomography (Cirrus OCT Zeiss; Carl Zeiss Meditec, Inc.), we observed a hyperrefringent line in the deep stroma in contact with the endothelium (Figure 3). No altered morphology or endothelial count (2,488 cells/mm2) was observed with corneal topography (K 43.9) or specular microscopy (Konan Noncon ROBO; Konan Medical, Inc., Tokyo, Japan) of the right eye (Figure 1B).
Nine-month postoperative anterior segment optical coherence tomography (Cirrus OCT Zeiss; Carl Zeiss Meditec, Inc., Jena, Germany) of the right eye where a hyperrefringent line in the deep stroma is in contact with the endothelium.
Prednisolone acetate eye drops 1% were initiated five times per day for 1 week with a progressive reduction for the following 5 weeks. Clinical progression was not satisfactory and periodic follow-up examinations were added because visual acuity and corneal alteration did not improve significantly. During this 2-year follow-up period, corneal opacification was stable without refractive or visual variations.
Corneal collagen cross-linking is meant to stop progression of keratoconus or corneal ectasia. It is important that pachymetric values for central thickness are greater than 400 μm to avoid cytotoxic damages.1
Irregular astigmatism and average values of spheres and cylinders in keratoconus can be treated with laser ablations. Topography-guided laser use is described in cases of stable or subclinical keratoconus with promising visual results.4,5 Nevertheless, these ablative procedures may remove and destabilize the corneal biomechanics and cause progression of the ectasic alterations. Therefore, in agreement with other authors, it is important to combine PRK and corneal cross-linking for these types of eyes.6,7
Advantages of performing these two procedures in the same surgery are that the ablation of PRK does not interfere with the cornea where corneal cross-linking takes place and corneal cross-linking of the ablated stroma depletes keratocytes of the anterior cornea, thus reducing the possibility of haze formation.8 Patients undergoing this dual procedure experience an increase in uncorrected visual acuity and improved corneal irregularity and resistance.7,8
Several complications can occur after surgery, including diffuse lamellar keratitis,2 early or late haze (11% of cases),3 early corneal edema, vision loss of 2 lines or fewer, herpetic keratitis with iritis and endotheliitis (even in patients without a history of herpes),9 and corneal infections.10
There are still concerns about combining PRK and corneal cross-linking. This combination has been used in several cases for eyes with low correction (less than 2.0 D spherical equivalent) without observing any complications (except the one described).6–8 A longer follow-up study that includes data from more cases is necessary to determine whether this combination should be a standard approach.
In our case, PRK and corneal cross-linking were used to improve uncorrected visual acuity, remove astigmatism, and stabilize the incipient and fruste keratoconus. Uncorrected visual acuity of 20/20 was obtained in both eyes, ophthalmological exploration was normal, and corneal topography was stabilized. However, a late deep, stromal haze alteration in contact with the endothelium was observed in the right eye. This was possibly due to previous surgery. It was a dense, deep, localized, and focal haze that improved with a corticoid-based treatment; however, the haze clearly affected visual acuity. This uncommon posterior keratocyte reaction (to the riboflavin or ultraviolet light exposure) was the etiology of the posterior haze. It was not an endotheliitis because there were no keratic precipitates and affectation was focal, maintaining normal characteristics under specular microscopy.
The sterile infiltrate (where haze affects the deeper stroma of the cornea) is similar to our findings, except that visual complaints for a significant period of time were sensitive to topical steroid treatment. This complication has never been described after use of these treatments. It is difficult to resolve because it only subsides partially and initially using corticoids and affects visual acuity.
Performing PRK and corneal cross-linking in one surgery is an efficient way to stop progression of forme fruste keratoconus and to improve uncorrected visual acuity. However, it is not free from complications, some of which have not yet been described or discussed fully in other studies. Forme fruste keratoconus should remain a contraindication for laser refractive surgery even with the use of corneal cross-linking.
- Raiskup-Wolf F, Hoyer A, Spoerl E, Pillunat LE. Collagen cross-linking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg. 2008;34:796–801. doi:10.1016/j.jcrs.2007.12.039 [CrossRef]
- Kymionis GD, Bouzoukis DI, Diakonis VF, Portaliou DM, Pallikaris AI, Yoo SH. Diffuse lamellar keratitis after corneal cross-linking in a patient with post-laser in situ keratomileusis corneal ectasia. J Cataract Refract Surg. 2007;33:2135–2137. doi:10.1016/j.jcrs.2007.06.070 [CrossRef]
- Koller T, Mrochen M, Seiler T. Complication and failure rates after corneal crosslinking. J Cataract Refract Surg. 2009;35:1358–1362. doi:10.1016/j.jcrs.2009.03.035 [CrossRef]
- Alpins N, Stamatelatos G. Customized photoastigmatic refractive keratectomy using combined topographic and refractive data for myopia and astigmatism in eyes with forme fruste and mild keratoconus. J Cataract Refract Surg. 2007;33:591–602. doi:10.1016/j.jcrs.2006.12.014 [CrossRef]
- Cennamo G, Intravaja A, Boccuzzi D, Marotta G, Cennamo G. Treatment of keratoconus by topography-guided customized photorefractive keratectomy: two-year follow-up study. J Refract Surg. 2008;24:145–149.
- Kanellopoulos AJ, Binder PS. Collagen cross-linking (CCL) with sequential topography-guided PRK: a temporizing alternative for keratoconus to penetrating keratoplasty. Cornea. 2007;26:891–895. doi:10.1097/ICO.0b013e318074e424 [CrossRef]
- Kymionis GD, Kontadakis GA, Kounis GA, et al. Simultaneous topography-guided PRK followed by corneal collagen cross-linking for keratoconus. J Refract Surg. 2009;25:S807–S811. doi:10.3928/1081597X-20090813-09 [CrossRef]
- Krueger RR, Kanellopoulos AJ. Stability of simultaneous topography-guided photorefractive keratectomy and riboflavin/UVA cross-linking for progressive keratoconus: case reports. J Refract Surg. 2010;26:S827–S832. doi:10.3928/1081597X-20100921-11 [CrossRef]
- Kymionis GD, Portaliou DM, Bouzoukis DI, et al. Herpetic keratitis with iritis after corneal crosslinking with riboflavin and ultraviolet A for keratoconus. J Cataract Refract Surg. 2007;33:1982–1984. doi:10.1016/j.jcrs.2007.06.036 [CrossRef]
- Pollhammer M, Cursiefen C. Bacterial keratitis early after corneal crosslinking with riboflavin and ultraviolet-A. J Cataract Refract Surg. 2009;35:588–589. doi:10.1016/j.jcrs.2008.09.029 [CrossRef]