Corneal-Wavefront guided transepithelial photorefractive keratectomy after corneal collagen cross linking in keratoconus / Queratectomía fotorrefractiva transepitelial guiada por frente de onda corneal tras entrecruzamiento del colágeno corneal en pacientes con queratocono

Purpose: To evaluate the efficacy and safety of Corneal-Wavefront guided transepithelial photorefractive keratectomy (TransPRK) after corneal collagen cross linking (CXL) in keratoconic patients. Methods: In this retrospective, non-comparative, consecutive case series, 39 keratoconic eyes underwent Corneal-Wavefront guided TransPRK for the correction of aberrations at least 4 months after conventional CXL at SEKAL Rovigo Microsurgery Centre, Rovigo, Italy. Two eyes (5%) underwent a secondary laser retreatment for the improvement of post-operative visual acuity and were not included in this retrospective analysis. The mean age of the patients was 35 ± 12 years (19-64 years) at the time of the surgery. Keratron-Scout (Optikon) topographer was used for diagnostic tests and a flying-spot laser (AMARIS; SCHWIND eye-tech-solutions) was used for the refractive surgery. Complete ophthalmic examinations were performed before and after the surgery (4-36 months postoperatively with a mean follow up time of 10 ± 8 months). Results: Preoperatively, eyes showed irregular astigmatism up to 8D. At last postoperative follow-up, 21 eyes (57%) had UDVA better than 20/40, and six eyes (16%) had UDVA of 20/20. Twenty-three eyes (62%) were within 1.50D of attempted correction in spherical equivalent (mean deviation from target was +1.09 ± 2.36D, range −2.50 to +7.38D). No eye lost 2 Snellen lines of CDVA, and 15 eyes (41%) had an increase of more than 2 lines. Conclusions: Corneal-Wavefront guided transepithelial PRK ablation profiles after conventional CXL yields to good visual, optical, and refractive results. These treatments are safe and efficacious for the correction of refracto-therapeutic problems in keratoconic patients (AU)

Objetivo: Evaluar la eficacia y seguridad de la queratectomía fotorrefractiva transepitelial (TransPRK) guiada por frente de onda corneal tras entrecruzamiento del colágeno corneal (CXL) en pacientes con queratocono. Métodos: En esta serie de casos consecutiva, retrospectiva y no comparativa, se realizó queratectomía fotorrefractiva transepitelial (TransPRK) guiada por frente de onda corneal a 39 ojos con queratocono para la corrección de aberraciones transcurridos al menos 4 meses desde la realización de un CXL convencional en el SEKAL Rovigo Microsurgery Centre, de Rovigo, Italia. Dos ojos (5%) fueron sometidos a un re-tratamiento secundario de láser para mejorar la agudeza visual postoperatoria, y no fueron incluidos en este análisis retrospectivo. La edad media de los pacientes fue de 35 ± 12 años (de 19 a 64 años) en el momento de la intervención. Se utilizó el topógrafo Keratron-Scout (Optikon) en las pruebas diagnósticas, y un láser de punto flotante (AMARIS; SCHWIND eye-tech-solutions) para la cirugía refractiva. Se realizaron exámenes oftálmicos completos con anterioridad y posterioridad a la intervención (de 4 a 36 meses postoperatorios, con un tiempo de seguimiento medio de 10 ± 8 meses). Resultados: Preoperatoriamente, los ojos presentaban un astigmatismo irregular de hasta 8 D. Durante el último seguimiento postoperatorio, 21 ojos (57%) alcanzaron una agudeza visual de lejos sin corrección (UDVA) superior a 20/40, y seis ojos (16%) una UDVA de 20/20. Veintitrés ojos (62%) se mantuvieron en el rango de 1,50 D con respecto al equivalente esférico planeada (la desviación media fue de +1,09 ± 2,36 D, rango de -2,50 a +7,38 D). Ninguno de los ojos perdió dos líneas de Snellen de agudeza visual a distancia corregida (CDVA), y 15 ojos (41%) reflejaron un incremento de más de dos líneas. Conclusiones: Los perfiles de la ablación PRK transepitelial guiados por frente de onda corneal tras un CXL convencional proporcionan unos buenos resultados a nivel visual, óptico, y refractivo. Estos tratamientos son seguros y eficaces en la corrección de los problemas refractoterapéuticos en pacientes con queratocono (AU)

An Update on the Safety and Efficacy of Corneal Collagen Cross-Linking in Pediatric Keratoconus.

Keratoconus is a degenerative disease that affects adolescents and young adults and presents with variable thinning and conical deformation of the corneal apex. The resultant irregular astigmatism can progress to levels that can significantly affect everyday activities and overall quality of life. Therefore, stopping the progression of the disease is an essential part in managing patients with keratoconus. Corneal collagen cross-linking is a minimally invasive procedure that stiffens the anterior corneal stroma by creating strong covalent bonds between collagen fibrils. Over the past decade, many studies have proved its safety and efficacy in halting keratoconus progression in adults. This review of the literature highlights the growing trend towards using this treatment in pediatric keratoconic patients. In children, keratoconus tends to be more severe and fast progression is often encountered requiring closer follow-up intervals. Standard cross-linking shows comparable results in children with a good safety-efficacy profile during follow-up periods of up to three years. Further research is needed to standardize and evaluate transepithelial and accelerated cross-linking protocols as these could be of tremendous help in a population where cooperation and compliance are major issues.

Estudio comparativo en queratoplastia para queratocono entre las técnicas lamelar profunda de Anwar (big bubble) y penetrante procedente de conversión / Comparative study of keratoconus between Anwar's deep anterior lamellar keratoplasty versus converted penetrating keratoplasty

OBJETIVO: El propósito de este grupo de estudio fue comparar los resultados entre los procedimientos de queratoplastia lamelar profunda anterior (deep anterior lamellar keratoplasty [DALK]) y queratoplastia penetrante (penetrating keratoplasty [PK]) en pacientes con queratocono. DISEÑO: Estudio de cohorte retrospectivo. MÉTODO: Se analizaron los resultados de 90 DALK y 49 PK procedentes de reconversión en pacientes con queratocono. Todos los procedimientos fueron realizados por el mismo cirujano (R.D.) desde 2006 hasta 2011. Entre ambos grupos se comparó la agudeza visual a distancia corregida (AVCC), el astigmatismo, el tiempo de la primera refracción, la paquimetría, el recuento de células endoteliales y las complicaciones postoperatorias. RESULTADOS: La media de edad fue de 28,2 años para DALK y de 31,7 años para PK (p = 0,17). El seguimiento medio fue de 14,7 meses para DALK y 19,4 meses para PK (p = 0,13). No hubo diferencia significativa alguna entre los grupos de PK y DALK en la media postoperatoria de AVCC (LogMAR) (0,17 frente a 0,17; p = 0,59), astigmatismo refractivo (-3,19 frente a -3,01 dioptrías; p = 0,65) ni en el tiempo de la primera refracción subjetiva (60,5 frente a 68 días; p = 0,50). Las principales complicaciones postoperatorias fueron 8% de rechazo endotelial en el grupo PK y 10% de vascularización de la interfaz en el grupo DALK. CONCLUSIONES: La única diferencia entre ambos grupos fue la neovascularización estromal profunda en DALK y el rechazo endotelial en PK, por lo que el procedimiento DALK debe ser considerado como primera opción en el tratamiento de pacientes con queratocono

OBJECTIVE: To compare outcomes between penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) in patients with keratoconus. DESIGN: Retrospective cohort study. METHODS: Data of 90 DALK and 49 procedures from conversion to PK, performed by a single surgeon (R.D.) from 2006 to 2011 were analysed. Outcomes on corrected distance visual acuity (BCVA), astigmatism, time to first refraction, pachymetry, endothelial count cell, and postoperative complications were compared between these groups. RESULTS: The mean age of the patients who underwent DALK and PK was 28.2 and 31.7 years, respectively (P=.17). The mean follow up for DALK and for the PK group was 14.7 and 19.4 months, respectively (P=.13). There was no significant difference between PK and DALK groups in the mean postoperative for: BCVA (LogMAR) (0.17 vs. 0.17; P=.59); refractive astigmatism (-3.19 vs.-3.01 diopters; P=.65), and time for the first subjective refraction (60.5 versus 68 days; P=.50). Main postoperative complications were 8% of endothelial rejection in PK group and 10% of deep stromal vascularization in DALK group. CONCLUSIONS: The only differences in postoperative results between groups were stromal neovascularization in DALK group and endothelial rejection in PK group. DALK should be considered as the first option when keratoplasty is indicated in keratoconus

Patterned corneal collagen crosslinking for astigmatism: computational modeling study.

PURPOSE: To test the hypothesis that spatially selective corneal stromal stiffening can alter corneal astigmatism and assess the effects of treatment orientation, pattern, and material model complexity in computational models using patient-specific geometries. SETTING: Cornea and Refractive Surgery Service, Academic Eye Institute, Cleveland, Ohio, USA. DESIGN: Computational modeling study. METHODS: Three-dimensional corneal geometries from 10 patients with corneal astigmatism were exported from a clinical tomography system (Pentacam). Corneoscleral finite element models of each eye were generated. Four candidate treatment patterns were simulated, and the effects of treatment orientation and magnitude of stiffening on anterior curvature and aberrations were studied. The effect of material model complexity on simulated outcomes was also assessed. RESULTS: Pretreatment anterior corneal astigmatism ranged from 1.22 to 3.92 diopters (D) in a series that included regular and irregular astigmatic patterns. All simulated treatment patterns oriented on the flat axis resulted in mean reductions in corneal astigmatism and depended on the pattern geometry. The linear bow-tie pattern produced a greater mean reduction in astigmatism (1.08 D ± 0.13 [SD]; range 0.74 to 1.23 D) than other patterns tested under an assumed 2-times increase in corneal stiffness, and it had a nonlinear relationship to the degree of stiffening. The mean astigmatic effect did not change significantly with a fiber- or depth-dependent model, but it did affect the coupling ratio. CONCLUSIONS: In silico simulations based on patient-specific geometries suggest that clinically significant reductions in astigmatism are possible with patterned collagen crosslinking. Effect magnitude was dependent on patient-specific geometry, effective stiffening pattern, and treatment orientation. FINANCIAL DISCLOSURES: Proprietary or commercial disclosures are listed after the references.

Very high fluence collagen cross-linking as a refractive enhancement of a regressed previous astigmatic keratotomy.

PURPOSE: To report a novel application of collagen cross-linking (CXL) in refractive astigmatic enhancement of previously performed astigmatic keratotomy. METHODS: A 28-year-old woman with prior history of bioptics correction of high myopic astigmatism with femtosecond laser-assisted astigmatic keratotomy followed by topography-guided LASIK showed long-term regression of the astigmatism 4 years later. A novel CXL application was employed in an attempt to reverse the regression of the astigmatic keratotomy. RESULTS: The high fluence CXL intervention resulted in correction of 2 diopters of topographic and refractive cylinder. Uncorrected distance visual acuity changed from 20/50 to 20/20 and refraction from -0.50 -2.00 @ 90 to +0.25 -0.25 @ 90 at the 7-month follow-up. CONCLUSIONS: A possible novel application of high fluence CXL with refractive cornea effect is introduced. It may offer rapid and simple rehabilitation and its effect may be tapered.

Topical cyclosporine A for postoperative photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To compare the stability and predictability of the refractive outcomes in eyes treated with photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) with and without postoperative use of topical cyclosporine A emulsion. SETTING: Naval Medical Center San Diego Refractive Surgery Center, San Diego, California, USA. DESIGN: Randomized clinical trial. METHODS: Patients had PRK or LASIK and were randomized, pairwise, to a standard postoperative treatment regimen with or without the addition of topical cyclosporine A 0.05% emulsion twice daily for 3 months postoperatively. Visual acuity, mesopic contrast acuity, refractions, and ocular symptoms were assessed through the 3-month examination. Tear-film samples (cytokines and chemokines) were analyzed preoperatively and 1 week and 1 and 3 months postoperatively. RESULTS: The PRK group comprised 70 patients and the LASIK group, 54 patients. The addition of topical cyclosporine A twice a day after PRK or LASIK did not confer special benefits in terms of achievement of target refraction, final uncorrected distance visual acuity (UDVA), or rate of visual recovery (all P>.05, multivariate analysis of variance [MANOVA]). There was no significant difference in tear-film composition based on measurement of matrix metalloproteinase-9, interleukin (IL)-6, or IL-8 recovery (all P>.05, MANOVA). CONCLUSION: The addition of topical cyclosporine A twice daily for 3 months after PRK or LASIK did not provide a significant benefit in the rate of visual recovery, final UDVA, or patient symptoms, nor did it significantly change measured inflammatory mediators (cytokines) present in the tear film.

Collagen crosslinking and toric iris-claw phakic intraocular lens for myopic astigmatism in progressive mild to moderate keratoconus.

PURPOSE: To report the long-term results of combined collagen crosslinking (CXL) and toric phakic intraocular lens (pIOL) implantation to correct myopic astigmatism in patients with progressive mild to moderate keratoconus. SETTING: Instituto de Microcirugia Ocular, Barcelona, Spain. DESIGN: Case series. METHODS: From November 2006 to July 2009, CXL was performed in eyes with proven progressive keratoconus. Once refraction and topography stabilized, toric Artiflex/Artisan pIOL implantation was performed to correct residual myopic astigmatism. A complete ophthalmologic examination, including manifest refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, biomicroscopy, tonometry, fundoscopy, keratometry, corneal tomography, and central endothelial cell count (ECC), was performed before each procedure and postoperatively at 3 months and at yearly intervals up to 5 years. Main outcome measures were accuracy and stability of the spherical equivalent (SE) and cylinder, keratometry, UDVA (efficacy), CDVA (safety), central ECC, and complications. RESULTS: The median follow-up in the 9 patients (17 eyes) was 36.9 months ± 15.0 (SD). The median interval between CXL and pIOL implantation was 3.9 ± 0.7 months. Fourteen eyes (82%) were within ± 0.50 diopter (D) of the attempted SE correction and 13 eyes (76%) were within ± 1.00 D of the attempted cylinder correction. The mean difference in simulated keratometry between preoperatively and the last follow-up was 0.17 ± 0.45 D (range -0.55 to 1.45 D). The postoperative UDVA was 20/40 or better in 16 eyes (94%). No eye lost lines of CDVA. No significant decrease in central ECC occurred (P>.05). CONCLUSION: Combined CXL and toric iris-claw pIOL implantation effectively and safely corrected myopic astigmatism in progressive mild to moderate keratoconus. FINANCIAL DISCLOSURE: Dr. Güell is a consultant to Ophtec. No other author has a financial or proprietary interest in any material or methods mentioned.

Tear secretion following excimer laser in situ keratomileusis.

PURPOSE: To evaluate the effect of laser in situ keratomileusis (LASIK) on tear secretion. METHODS: A non-consecutive series of 42 eyes of 42 patients had LASIK for the correction of myopia and myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent refraction was -5.25 +/- 1.00 D (range, -1.75 to -11.00 D). Attempted correction aimed at emmetropia. Schirmer I and II, and tear break-up time (BUT) tests were performed preoperatively and at 1, 3, and 6 months postoperatively. All tests were correlated to the amount of the attempted correction. RESULTS: Preoperatively, mean values were Schirmer I: 16.2 mm, Schirmer II: 11.6 mm, and BUT: 16.3 sec. One month after LASIK, mean values were Schirmer I: 12.8 mm, Schirmer II: 9.2 mm, and BUT: 13.3 sec. At 3 months, mean values were Schirmer I: 15.76 mm, Schirmer II: 11.3 mm, and BUT: 14.15 sec. At 6 months, mean values were Schirmer I: 15.96 mm, Schirmer II: 11.66 mm, and BUT: 16.3 sec. No correlation to the amount of attempted correction was found. Fellow eye tests were not affected at any interval. CONCLUSIONS: Tear secretion following LASIK was decreased during 3 months after surgery and was normalized by 6 months.

Gender- and age-related differences in corneal topography.

PURPOSE: To investigate gender- and age-related differences in the corneal topography of a normal population. METHODS: One hundred thirty-two topographic examinations were collected from 100 patients ranging in age from 23 to 83 years (average, 57.35+/-17.38 years). Data were segregated by gender and further divided into younger (less than 50 years) and older (50 years or more) age groups. The topographic indices of Surface Regularity Index, Surface Asymmetry Index, Irregular Astigmatism Index, Standard Deviation of Corneal Power, Corneal Eccentricity Index, Coefficient of Variation of Corneal Power, Simulated Keratometry 1 and 2, and Average Corneal Power were examined. The astigmatism pattern and corneal irregularity were determined and compared with respect to gender and age. RESULTS: The corneas of older men were flatter than those of older women (p < 0.001). The vertical corneal meridian, but not the horizontal meridian, showed statistically significant gender-related changes with aging (p < 0.001). Older men had a significantly higher potential for against-the-rule astigmatism than women (p < 0.001). Corneal irregularity (measured in terms of the Surface Regularity Index and Irregular Astigmatism Index) increased with age (p < 0.001 and p < 0.001, respectively), although there was no gender-related difference. In the younger group, no gender-related differences in corneal curvature or astigmatism pattern were found. CONCLUSION: Aging influences changes in patterns of astigmatism differently in men and women. Decreases in levels of sex hormones may play a role in gender-related changes in corneal structure with age.

Tear secretion following spherical and astigmatic excimer laser photorefractive keratectomy.

PURPOSE: To evaluate the effect of spherical and astigmatic excimer laser photorefractive keratectomy (PRK and PARK, respectively) on tear secretion. SETTING: The Vlemma Eye Center, Athens, Greece. METHODS: Forty-eight eyes of 48 patients had PRK (28 eyes) or PARK (20 eyes) for the correction of myopia and combined myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent was -3.96 diopters (D) +/- 1.00 (SD) in the PRK eyes (range -2.00 to -6.50 D) and -3.45 +/- 0.50 D in the PARK eyes (range -1.75 to -6.00 D). Attempted correction aimed at emmetropia. Schirmer I and II and tear film breakup time (BUT) tests were performed preoperatively and 1, 3, and 6 months postoperatively. All tests were correlated to the amount of attempted correction. RESULTS: In the PRK group, the preoperative mean values were Schirmer I, 16.20 mm; Schirmer II, 12.73 mm; and BUT, 16.46 sec. At 1 month, they were 12.23 mm, 8.46 mm, and 13.33 sec, respectively; at 3 months, 13.86 mm, 10.64 mm, and 14.42 sec, respectively; at 6 months, 14.32 mm, 11.32 mm, and 15.36 sec, respectively. In the PARK group, the mean Schirmer I, II, and BUT values were preoperatively 18.52 mm, 14.86 mm, and 17.42 sec, respectively; at 1 month, 14.5 mm, 10.4 mm, and 14.36 sec, respectively; at 3 months, 15.36 mm, 11.81 mm, and 14.72 sec, respectively; and at 6 months, 16.5 mm, 12.15 mm, 16.5 sec, respectively. No correlation to the amount of attempted correction was found. Fellow-eye tests were not affected at any interval. CONCLUSIONS: In the first 6 months after PRK and PARK, tear secretion test values decreased.

[Evaluation of astigmatism and blood-aqueous barrier breakdown following procedures in the anterior eye segment]. / Ocena astygmatyzmu oraz zmian przepuszczalnosci bariery krew-ciecz wodnista po operacjach przedniego odcinka galki ocznej.

PURPOSE: The aim of this study was to evaluate the disruption of the blood-aqueous barrier (BAB) and the induced astigmatism following phacoemulsification, trabeculectomy and phacotrabeculectomy. MATERIAL AND METHODS: 141 eyes of patients who underwent different surgical procedures of the anterior segment were examined with the use of computer-assisted videokeratography. All maps were recorded preoperatively, and one and five days after surgery. We also applied a laser flare-meter in 41 eyes in order to quantify aqueous flare following these procedures. RESULTS: The mean surgically-induced astigmatism following conventional trabeculectomy was 2.1 D and 1.4 D one and five days postoperatively, phacoemulsification with sutures 2.7 D and 1.9 D and phacotrabeculectomy 3.0 D and 2.4 D, respectively. Lower values of astigmatism obtained after sutureless phacoemulsification were 0.6 D and 0.3 D one and five days postoperatively, respectively (p < 0.05 vs Phaco+IOL+Trab. group, p < 0.01 vs other groups). It was found that aqueous flare values following phacotrabeculectomy were 58.0 photon counts/milisec.--one day, 39.3--3 days, 24.4--7 days, 20.4--10 days postoperatively. Significantly reduced values were observed after phacoemulsification--27.6 one day after surgery and 17.6--3 days later (p < 0.01 vs Phaco+IOL+Trab.group). CONCLUSIONS: It could be concluded that induced astigmatism and the amount of inflammation were the highest after triple procedure and the lowest after phacoemulsification.

Ultrastructural and immunohistochemical findings after linear excimer laser keratectomy.

BACKGROUND: One human pathology specimen has been studied previously following the use of the excimer laser for the correction of astigmatism. We report histopathologic findings following linear corneal excisions with the excimer laser. METHODS: A 193 nm excimer laser was used to create symmetrical, transverse excisions in a human eye to correct astigmatism. Three months later, a full-thickness corneal transplant was performed due to unsatisfactory refractive results. The excised corneal button was examined with light microscopy, transmission electron microscopy and immunohistochemistry. RESULTS: An area 10 to 20-micron wide was observed between the epithelial cells within the keratectomy and the sharply dissected stromal lamellae. This area stained positive for laminin and pro-collagen type III. Some epithelial cells showed processes reaching into this area. Descemet's membrane, immediately underneath the area of the keratectomy, contained atypically striated collagen fibers. CONCLUSIONS: These findings demonstrate wound healing changes similar to those reported following diamond knife keratotomy and photorefractive keratectomy for myopia. The changes in the posterior cornea are similar to those previously reported when an excimer laser beam approached Descemet's membrane.

Suture to limbus distances in eyes with a posterior chamber intraocular lens implanted by scleral fixation.

This study used linear regression to analyze the correlation between the location of transscleral sutures and the postoperative visual acuity, refraction, and anterior chamber depth in eyes with posterior chamber intraocular lenses implanted by scleral fixation. The suture-to-limbus distance at the 12 o'clock and 6 o'clock positions averaged 2.4 mm and 1.7 mm, respectively. Suture location had no statistically significant relationship with postoperative acuity, spherical equivalent, astigmatism, or anterior chamber depth.

Variations in the local refractive correction of the eye across its entrance pupil.

We show that normally a spherocylindrical lens will correct the local refractive error of any small area of the pupil. In general, however, the correction varies with position across the pupil. Plots are given to illustrate this variation for 2 typical individual eyes and for the average of 11 eyes, as calculated from the corresponding wavefront aberrations. The implications of these results for the design and use of objective optometers are briefly considered.