Keratoconus is a corneal disease characterized by bilateral, noninflammatory, and progressive corneal ectasia.1 The keratoconic corneal apex is mostly central or inferior in location.2 Superior keratoconus is one of the rare entities of corneal ectasia compromising <1% of cases of keratoconus. It can be diagnosed by clinical examination or corneal topographic examination.3 Only a few reports described this rare type of corneal ectasia.4,5 Combined accelerated corneal crosslinking (CXL) and intrastromal KeraRings implantation by the femtosecond laser were performed for a case of advanced superior keratoconus as a modality for treating such rare type of corneal ectasia.6 As 1 line of management, CXL is efficient in halting the ectatic pathological process in most patients with progressive keratoconus.7 Accelerated CXL was developed to maintain total irradiance with accelerated treatment time by a total irradiation increase.8
In this case report, we present the 3-year outcomes of accelerated epithelium-off CXL for a case of superior keratoconus.
A 26-year-old man was referred to the Sohag Center for LASIK and Corneal Surgeries with progressive loss of vision in both eyes. The patient was prescribed spectacles, which he was not getting comfortable with wearing. The uncorrected distance visual acuity (UDVA) in the right eye was 0.1 in decimal notion corrected to 0.4 by a refraction of −1.00 diopter sphere −3.50 diopter cylinder @ 107, whereas the UDVA in the left eye was 0.01 corrected to 0.3 by a refraction of +2.00 diopter sphere −5.50 diopter cylinder @ 31.
Asking for risk factors, the patient reported vigorous eye rubbing over the years. Yet, there was no family history of a similar condition. Slitlamp examination of both eyes revealed a superior corneal protrusion without associated scarring or vascularization. Corneal thinning in the protruded area was noticed. There were no signs of advanced keratoconus as Fleischer rings or Vogt's striae. Yet, no signs of active allergic manifestations were reported. There were no associated signs of an endothelial abnormality, for example, increased stromal thickness or Descemet membrane guttae or folds.
There was no associated localized corneal edema, keratic precipitate, or anterior segment reaction. There were no associated lenses or posterior segment abnormality.
Corneal tomography of both eyes was performed by Sirius Scheimpflug Corneal Tomographer (Costruzione Strumenti Oftalmici). It revealed grade 1 keratoconus with a superior cone location. In the right eye corneal tomography, Kmax was 54.9 diopters (D) at the steepest point of the cone with corresponding high anterior and posterior elevation (39 μm and 81 μm), whereas in the left eye corneal tomography, Kmax was 57.76 D at the steepest point of the cone with corresponding high anterior and posterior elevation (35 μm and 55 μm). The apex of the cone in both eyes was 3 mm superiotemporal from the corneal apex; x location and y location for the thinnest point was (−1.38 mm, −0.24 mm) in the right eye and (1.2 mm, −0.09 mm) in the left eye. Preoperative pachymetry in the right eye was 465 μm and in the left eye was 452 μm. There was no superior marginal thinning.
Specular examination (Topcon SP-2000P) of both eyes revealed normal corneal endothelium. Informed written consent was obtained from the patient after the explanation of the treatment plan.
This case report adhered to the tenets of the Helsinki Declaration, and the study was approved by the ethical committee of the center.
The decision was to do accelerated epithelium-off CXL for 1 eye per session. Then, visual rehabilitation was planned to be by a trial of rigid gas-permeable contact lens fitting after keratometric stability.
The corneal epithelium was mechanically removed to a 9.0 mm corneal diameter. The corneal surface was treated first by VibeX Rapid (isotonic riboflavin 0.1% with hydroxypropyl methylcellulose) for 15 minutes. It was applied every 90 seconds during the soak time. The treated corneal stroma and anterior chamber saturation were confirmed by slitlamp examination. Then, the cornea was treated by the KXL System Accelerated CXL (Avedro, Inc.) for 3 minutes using the pulsed mode with 30 mW/cm2 power and a total dose intensity of 5.4 J/cm2. A soft contact lens bandage was applied at the end of the surgery. The postoperative medication included topical antibiotic eyedrops (eg, moxifloxacin hydrochloride 0.5% 5 times a day for 1 week), topical steroid eyedrops (eg, prednisolone acetate 1% 5 times a day for 1 week), lubricant eyedrops, and systemic nonsteroidal anti-inflammatory drugs. The soft contact lens bandage was removed after 1 week.
The patient was followed for 1 year (every 3 months). The follow-up showed improvement in the UDVA and corrected distance visual acuity with corneal tomographic parameter improvement, as summarized in Table 1 and Figure 1. No postoperative complications were found. The cornea in both eyes remained clear as shown by corneal optical densitometry measurement using Pentacam (Oculus Surgical, Inc.) with all readings <20 standardized grayscale units (Figure 2).9
Table 1. -
Three-Year Follow-up of Visual and Corneal Tomographic Parameters of Both Eyes.
||Mean K (D)
||Thinnest location (μm)
| 2017 (preop)
||−1.00 DS −3.50 DC @ 107
| 2018 (1 y post-CXL)
||−1.50 DS −1.50 DC @ 110
| 2019 (2 y post-CXL)
||−1.00 DS −1.75 DC @ 115
| 2020 (3 y post-CXL)
||−1.00 DS −1.50 DC @ 111
| 2017 (preop)
||+2.00 DS −5.50 DC @ 31
| 2018 (1 y post-CXL)
||+0.75 DS −2.50 DC @ 17
| 2019 (2 y post-CXL)
||+0.75 DS −2.00 DC @ 13
| 2020 (3 y post-CXL)
||+0.75 DS −1.75 DC @ 15
CXL = corneal crosslinking; DC = diopter cylinder; DS = diopter sphere; preop = preoperative
The management of superior keratoconus, which is a rare type of corneal ectasia, is considered a challenge. The initial management of keratoconus with superior cone location by rigid gas-permeable contact lenses was reported in a study of Weed et al. with successful visual rehabilitation; however, it represented a particular challenge to the contact lens practitioner.10
In our case, no abnormality was detected in the corneal specular examination of both eyes, which excluded the liability of corneal endothelial dysfunction. Other diseases causing superior corneal thinning and protrusion were excluded on slitlamp examination by the absence of vascularization or lipid deposition. Also, the diagnosis of superior pellucid marginal degeneration was excluded by the absence of a peripheral band of thinning by clinical and topographic examination.
Crosslink introduced by Wollensak et al. in 2003 is a minimally invasive procedure to halt the progression of keratoconus.11 It is produced by increasing the biomechanical stiffness of the keratoconic cornea.12
The grade of keratoconus of our case was of grade 1 in both eyes according to Amsler-Krumeich classification with mean K <48 D.13 Thus, the decision was to do bilateral accelerated epithelium-off CXL for both eyes in 2 separate sessions.
We followed up the patient for an extended duration (3 years) with visual improvement as regards UDVA and corrected distance visual acuity and topographic improvement, especially Kmax and mean K with sequential flattening in the superior cone of both eyes. The corneal elevation of both anterior and posterior did not change over the years, as well.
No previous studies reported the results of CXL in such a rare type of corneal ectasia. Rogers et al. reported 2 cases of bilateral superior keratoconus, one of which was treated by CXL, but the results were not reported.14
We used corneal optical densitometric examination by Scheimpflug corneal tomography to ensure the corneal clarity at the early stages of diagnosis and to exclude any degree of corneal haze after CXL.
The 3-year follow-up of CXL for superior keratoconus was a good option for stabilizing progression in this uncommon case, which can broaden the spectrum in which CXL is used.
In conclusion, accelerated epithelium-off CXL was found to stabilize and halt the progression of superior keratoconus after long-term follow-up.
WHAT WAS KNOWN
- Superior keratoconus is one of the rare entities of corneal ectasia. It can be diagnosed by clinical examination or corneal topographic examination.
- Corneal crosslinking is a successful procedure in halting the ectatic pathological process in most patients with progressive inferior keratoconus. However, the outcome of this line of treatment was not studied in superior keratoconus, especially with long-term results.
WHAT THIS PAPER ADDS
- Accelerated epithelium-off corneal crosslinking showed a successful outcome as regards halting the progression of such a rare type of superior keratoconus after long-term follow-up.
1. Hofstetter HW. A keratoscopic survey of 13,395 eyes. Am J Optom Arch Am Acad Optom 1959;36:3–11
2. Smolek MK, Beekhuis WH. Collagen fibril orientation in the human corneal stroma and its implications in keratoconus. Invest Ophthalmol Vis Sci 1997;38:1289–1290
3. Prisant O, Legeais JM, Renard G. Superior keratoconus. Cornea 1997;16:693–694
4. Chiang CC, Lin JM, Tsai YY. Superior keratoconus with inferior paracentral corneal thinning and inferior peripheral pellucid marginal degeneration. Eye (Lond) 2007;21:266–268
5. Tananuvat N, Leeungurasatien P, Wiriyaluppa C. Superior keratoconus with hydrops. Int Ophthalmol 2009;29:419–421
6. Mounir A, Mostafa EM. Combined accelerated corneal collagen crosslinking and intrastromal Kerarings implantation for treatment of advanced superior keratoconus. GMS Ophthalmol Cases 2020;10:Doc10
7. Hersh PS, Stulting RD, Muller D, Durrie DS, Rajpal RK; United States Crosslinking Study Group. United States multicenter clinical trial of corneal collagen crosslinking for keratoconus treatment. Ophthalmology 2017;124:1259–1270
8. Santhiago MR. Accelerated corneal cross-linking: we must acquire knowledge as fast. J Refract Surg 2016;32:362–363
9. Wollensak G, Spörl E, Reber F, Pillunat L, Funk R. Corneal endothelial cytotoxicity of riboflavin/UVA treatment in vitro. Ophthalmic Res 2003;35:324–328
10. Weed KH, McGhee CN, MacEwen CJ. Atypical unilateral superior keratoconus in young males. Cont Lens Anterior Eye 2005;28:177–179
11. Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol 2003;135:620–627
12. Mazzotta C, Traversi C, Baiocchi S, Bagaglia S, Caporossi O, Villano A, Caporossi A. Corneal collagen cross-linking with riboflavin and ultraviolet a light for pediatric keratoconus: ten-year results. Cornea 2018;37:560–566
13. Krumeich JH, Daniel J, Knulle A. Live-epikeratophakia for keratoconus. J Cataract Refract Surg 1998;24:456–463
14. Rogers GJ, Attenborough M. Bilateral superior keratoconus: two case reports. Eye (Lond) 2014;28:1254–1257