to report the effect of wavefront - guided photorefractive keratectomy and corneal collagen cross - linking ( cxl ) on visual problems after ferrara ring segment placement . a 32-year - old male patient was treated with a ferrara ring segment for keratoconus . after 6 months , wavefront - guided photorefractive keratectomy and cxl were applied simultaneously to correct high order aberration and refractive error . six months after the wavefront - guided photorefractive keratectomy and cxl , the uncorrected distance visual acuity was 20/25 , and there was a 30% decrease in coma aberrations . wavefront - guided surface ablation and cxl may reduce high order aberrations and glare complaints after intrastromal corneal ring implantation . intrastromal corneal ring segments ( icrs ) , which were initially designed to correct mild to moderate myopia , have been demonstrated as a surgical option to manage keratoconus.13 its therapeutic effects are based on the induction of remodeling of the corneal anterior and posterior surface s topography , which improves the optical quality of the cornea and reduces the optical aberrations , with consequent improvement in visual acuity.4,5 currently there are many types of commercially available icrss , such as intacs ( addition technologies , des plaines , il , usa ) , keraring ( mediphacos , belo horizonte , brazil ) , and ferrara ring ( ferrara ophthalmics , belo horizonte , brazil ) . the ferrara intrastromal ring segment used in this study has a small radius of curvature and a triangular anterior surface.6 the unique triangular shape with a flat posterior surface is purported to induce a prismatic effect on the cornea which reduces glare and halo.7 however these complaints were reported in 10% of the ferrara cases followed over a 5-year period.8 although these symptoms may disappear over time , pilocarpine or brimonidine tartrate drops are recommended for persistent cases . in addition , increase in high order aberrations ( hoas ) after icrs implantation is another problem that may affect visual quality.9,10 the photorefractive keratectomy ( prk ) plus corneal collagen cross - linking ( cxl ) procedure is an effective treatment option for progressive keratoconus . this procedure was found to be associated with stable refractive and topographic outcomes and with a reduction in corneal aberrations.11 herein , we describe a case of visual complaint after ferrara ring segment placement , which was treated successfully with wavefront - guided prk and cxl procedures after the ring was extracted . a 32-year - old male patient was referred to our department from an ophthalmology clinic , with bilateral keratoconus . he worked with heavy metals and could not use contact lenses or eyeglasses on the job . his uncorrected distance visual acuity was 20/200 and corrected distance visual acuity was 20/100 with 5.00 2.50  30 in the right eye . the uncorrected distance visual acuity was 20/70 and corrected distance visual acuity was 20/40 with 2.50 2.00  175 in the left eye . corneal topographical findings measured with pentacam corneal topography system ( oculus opticgerate gmbh , wetzlar , germany ) revealed a keratoconus pattern in both eyes ( figure 1a ) . in the corneal wavefront map , measured with the wavescan wavefront system ( abbott medical optics , santa ana , ca , usa ) , primary and secondary vertical coma dominance was observed ( figure 1b ) . the aberrometry analyses under scotopic condition were based on a pupil diameter of 6 mm . the scotopic pupil diameter , measured with the colvard pupilometer ( oasis medical inc , san dimas , ca , usa ) , was 6 mm . in an attempt to improve vision , ferrara icrs implantation was planned for the correction of the corneal steepening and irregularity . two ferrara ring segments with 250 m thickness and 160 arch - length were to be placed temporally and nasally using a 30 khz femtosecond laser ( intralase fs laser , abbott medical optics , ) in compliance with the ferrara nomogram in the right eye . after ferrara ring segment implantation , the corrected distance visual acuity was 20/40 with optimal centralization of the ring segments ( figure 2a and b ) . however the patient had severe light glare complaints under photopic conditions in his right eye . corneal topography revealed diminishing keratometric values ( figure 2c ) , and the zernike analysis with pentacam ( oculus opticgerate gmbh ) showed an increase in vertical coma and trefoil ( figure 2d ) . the aberrometric measurements taken from the right eye by wavescan demonstrated that hoa root mean square error was 0.75 m and coma domination was 0.404 m ( figure 3a ) . based on these results , wavefront - guided prk along with cxl was planned to correct refractive errors and aberrations of the right eye . the wavefront - guided ablation pattern was prepared using a wavescan aberrometer and transferred to a visx s4 ir device ( abbott medical optics , santa ana , california , usa ) . , istanbul , turkey ) at 0.02% was applied for 20 seconds to impede haze and regression . following prk , cxl was applied in compliance with the dresden protocol.12 a 6.5 mm optical zone was used with a transition zone of 8.5 mm . six months after wavefront - guided prk and cxl procedures , the uncorrected distance visual acuity was 20/25 . the high order root mean square score was drawn back to 0.39 m , and coma aberration was reduced to 0.277 m ( figure 3b ) . at the 12 month visit , refractive status , visual acuity , wavefront analyses , and topograpgical measurements were unchanged ( figure 3c and d ) . visual problems such as glare and halo are two of the expected complications after icrs implantation , and it may adversely affect daily activities . although no comprehensive studies have been conducted on glare and halo after icrs implantation , one study showed that 10% of the ferrara cases had halo complaint after surgery , and it has been associated with pupil size.8 in our case , glare complaint could not be explained by pupil size , which was 6 mm . we hypothesized that the cause of glare might be hoas , and studies have shown increases in hoas after icrs implantation.9,10 hoas can also have a significant impact on one s quality of vision and are often linked to visual glare and halos . glare symptom tends to get better over time . in severe cases , nighttime application of pilocarpine or brimonidine tartrate drops also torquetti et al developed segments with a yellow filter in the matrix to avoid blue light at night , which can significantly decrease the incidence of glare and halos.8 in our study , after icrs had been extracted , a combination treatment including wave - front guided prk and cxl was applied to the patient . a few studies have reported the use of cxl along with topography - guided prk in order to provide better visual rehabilitation in patients with keratoconus.1317 moreover , only one study , carried out by kremer et al , has reported the use of wavefront - guided prk along with cxl in keratoconic eyes.18 as we considered that our patient s glare symptom was associated with hoas , we performed wavefront - guided prk . in summary , this report contributes new information to the literature . first , a severe glare complaint that is resistant to medical therapy may present after icrs implantation . lastly , wavefront guided prk and cxl treatment may yield a reduction in hoa and an improvement of glare symptom in a keratoconic eye that has undergone icrs extraction .
purposeto report the effect of wavefront - guided photorefractive keratectomy and corneal collagen cross - linking ( cxl ) on visual problems after ferrara ring segment placement.materials and methodsa 32-year - old male patient was treated with a ferrara ring segment for keratoconus . 
 one year later , the ring was removed due to severe glare complaints . 
 after 6 months , wavefront - guided photorefractive keratectomy and cxl were applied simultaneously to correct high order aberration and refractive error.resultssix months after the wavefront - guided photorefractive keratectomy and cxl , the uncorrected distance visual acuity was 20/25 , and there was a 30% decrease in coma aberrations . 
 the glare complaint regressed.conclusionwavefront-guided surface ablation and cxl may reduce high order aberrations and glare complaints after intrastromal corneal ring implantation .