Findings from a study undertaken at Dr Lovisolo’s practice indicate that in carefully-selected patients, a triple procedure, comprising Keraring implantation followed by accelerated CXL and topo-guided ablation can provide significant functional improvement in cases of progressive keratoconus.
Take-home message: Findings from a study undertaken at Dr Lovisolo’s practice indicate that in carefully-selected patients, a triple procedure, comprising Keraring implantation followed by accelerated CXL and topo-guided ablation can provide significant functional improvement in cases of progressive keratoconus.
By Dr Carlo F. Lovisolo
Keratoconus, a condition characterised by thinning and steepening of the central cornea, visual distortions and gradual loss of corrected distance visual acuity (CVDA), requires careful management in order to halt progression and improve the patient’s vision. Fortunately, in addition to spectacles and contact lenses, surgeons now have access to a plethora of treatments that can delay or even eliminate the need for a corneal transplant; dramatically improve both corrected and unaided vision; and boost patients’ quality of life. Such treatments include femtosecond laser surgery, corneal collagen cross-linking (CXL) using riboflavin and ultraviolet light, phakic intraocular lenses (IOL), intrastromal corneal ring segments (ICRs) and tomography-guided surface excimer laser ablations (phototherapeutic keratectomy – PTK).1,2
Treatments such as implantation of an ICR may be offered as a sole treatment, for example, in patients with loss of CDVA and evidence of corneal surface irregularity. In this instance, use of an ICR helps to reduce corneal steepening by re-centring the corneal apex and correcting both lower and higher order secondary aberrations; ICR implantation may also delay or even eliminate the need for keratoplasty.3,4 Corneal collagen cross-linking may also be used as a sole treatment in patients with initial keratoconus in whom there is no or limited evidence of corneal surface irregularity or loss of CDVA. However, in many cases, it is necessary to provide step-wise, synergistic treatments in order to provide maximum benefit. For example, in patients with evidence of disease progression, corneal surface irregularity and loss of CDVA, performing CXL post-ICR will also help to improve the biomechanical properties of the cornea.5 In selected cases, the surgeon may then decide to perform topography-guided surface photokeratectomy (PTK) and/or add a phakic IOL. Clearly then, the ability to combine different treatment modalities allows us to customise treatment according to each patient’s needs.
Next: Applying the triple procedure
Since 2008, I have been using what is often referred to as the “triple procedure”. It begins with the implantation of an ICR. For more than 15 years, I have been using the Keraring (Mediphacos Ltda, Belo Horizonte, Brazil), which was specifically designed to treat corneal ectatic disorders and reduce associated refractive errors.
Keraring ICRs are made of medical-grade polymethyl methacrylate and are characterised by a unique prismatic design that reduces the incidence of glare and halos. The Keraring “remodels” the cornea through the addition of tissue, thus helping to preserve corneal integrity. By conserving the natural prolate shape of the cornea, it reduces optical aberrations (mainly third order, comatic), improves visual acuity and increases tolerance to rigid gas-permeable contact lenses. The Keraring is available in different thicknesses (from 150 to 450 microns), optical zones (5.0, 5.5 and 6.0 mm) and arc lengths (90°, 120°, 150°, 210°, 340° and 355°), thus allowing the treatment to be fully customised to patient need and surgical preferences.6
Three to six months post-ICR implantation, when the outcome (corneal regularisation, uncorrected visual acuity and symptoms secondary to residual aberropia) is satisfying, I perform epi-off (epithelium removed with excimer laser) accelerated CXL (UV-A light irradiance: 45 mW/cm2 for 2 minutes and 40 seconds, 7.2 J/cm2 pulsed modality soaking time: 10 minutes) with the Avedro KXL system. Although there is little published evidence to suggest that accelerated CXL improves efficacy compared with standard CXL, the shorter treatment time increases patient comfort, improves practice efficiency and may also reduce the risk of corneal dehydration.7 Moreover, our preliminary data suggest an improved predictability in terms of managing the postoperative excessive flattening (hyperopic shift) and overoblate corneal shape.
When significant residual visual errors or cornea irregularities remain after ICR implantation, I usually combine a trans-epithelial photokeratectomy guided by tomography and pachymetry data to CXL. Published evidence suggests the latter procedure helps to improve coma and irregular astigmatism. For example, in a 117-eye study of patients with low to moderate myopic astigmatism, uncorrected distant visual acuity was ≥20/20 in 96.6% of the eyes, and manifest refraction spherical equivalent was within ±0.5 D of the desired refraction in 93.2% of eyes at 12 months post-treatment.8 Trans-epithelial topo-guided ablation also helps to overcome a lack of predictability associated with keratoconus treatment caused by excessive corneal flattening (hyperopic shift), ablation rate of the stroma, epithelial compensation, lack of information about the posterior corneal surface (which may lead to inaccurate correction of astigmatism), and tilt compensation.
Next: Clinical findings
Before performing ablation it is necessary to undertake a comprehensive high-resolution analysis of all the corneal layers, the epithelium in particular, with very high frequency echography (Artemis A2) and anterior segment optical coherence tomography (Casia or Optovue). It is also important to select the “right” patient. Although trans-epithelial topo-guided ablation can be used to correct both low- and high-order aberrations, it is not suitable treatment for all keratoconus patients due to the excessive stromal tissue that is sacrificed during a complete ablation. In order to guarantee the safety of the procedure, I only perform ablation in patients with moderate ectasia or nipple cone keratoconus.
I recently conducted a prospective clinical study to evaluate the safety and efficacy of the triple procedure. The study included 150 eyes with keratoconus divided into three groups: Group A received the Keraring and accelerated CXL, Group B received topo-guided ablation and accelerated CXL, and Group C received all three treatments. The average follow-up time was 21 months (range, 14-26 months). All tomographic indices, mean uncorrected visual acuity, mean best spectacle-corrected visual acuity and coma improved in all groups, with slight (but not statistically significant) difference between Groups A and B. In contrast, Group C showed a statistically significant (p<0.05) improvement in all functional parameters when compared to Groups A and B.
In patients with significant residual ammetropia it may be necessary to add a further treatment step, i.e., apply a “quadruple procedure”. I have found that implanting a toric phakic IOL provides safe and very effective outcomes in such patients with stable keratoconus. Efekan Coskunseven, MD, also reported that topo-guided transepithelial PRK followed by toric phakic IOL Implantation after Keraring implantation followed by CXL helped to stop disease progression and improved vision and refraction in a case series of seven patients (11 eyes) with keratoconus.9
Clearly, as with any treatment, correct patient selection is a key factor in achieving optimal outcomes. As noted previously, only I perform ablation in patients with moderate ectasia or nipple cone keratoconus. Additionally, the triple procedure is unsuitable for patients under 18 years of age and should not be used in individuals with hydrops, corneal opacities or dystrophies, herpetic keratitis or in patients with autoimmune or systemic diseases. However, findings from the study undertaken at my centre indicate that in carefully-selected patients, a triple procedure, comprising Keraring implantation followed by accelerated CXL and topo-guided ablation can provide significant functional improvement in cases of progressive keratoconus.
Dr Carlo F. Lovisolo
Dr Carlo F. Lovisolo is an ophthalmologist in practice at Quattroelle Custom Eye Centers, Milan, Italy.
Dr Lovisolo has no financial interests in Mediphacos Ltda.