Management of Stromal Corneal Dystrophies; Review of the Literature with a Focus on Phototherapeutic Keratectomy and Keratoplasty.

Corneal dystrophies are a group of non-inflammatory inherited disorders of the cornea. This review considers treatment options for epithelial-stromal and stromal corneal dystrophies: namely Reis-Bücklers, Thiel-Behnke, lattice, Avellino, granular, macular and Schnyder corneal dystrophies. Where there is visual reduction, treatment options may include either phototherapeutic keratectomy (PTK) or corneal transplantation. Due to the anterior location of the deposits in Reis-Bücklers and Thiel-Behnke dystrophies, PTK is considered the treatment of choice. For lattice, Avellino, granular and macular corneal dystrophies, PTK provides temporary visual improvement; however, with recurrences, repeat PTK or a corneal transplant would be needed. For Schnyder dystrophy, should treatment be required, PTK may be the preferred option due to the potential for recurrence of the disease in corneal transplantation. This review discusses the literature and evidence base for the treatment of corneal dystrophies in terms of visual outcomes and recurrence rate.

The pre-Descemet's layer (Dua's layer, also known as the Dua-Fine layer and the pre-posterior limiting lamina layer): Discovery, characterisation, clinical and surgical applications, and the controversy.

The pre-Descemet's layer/Dua's layer, also termed the Dua-Fine layer and the pre-posterior limiting lamina layer, lies anterior to the Descemet's membrane in the cornea, is 10 µm (range 6-16) thick, made predominantly of type I and some type VI collagen with abundant elastin, more than any other layer of the cornea. It has high tensile strength (bursting pressure up to 700 mm of Hg), is impervious to air and almost acellular. At the periphery it demonstrates fenestrations and ramifies to become the core of the trabecular meshwork, with implications for intraocular pressure and glaucoma. It has been demonstrated in some species of animals. The layer has assumed considerable importance in anterior and posterior lamellar corneal transplant surgery by improving our understanding of the behaviour of corneal tissue during these procedures, improved techniques and made the surgery safer with better outcomes. It has led to the innovation of new surgical procedures namely, pre-Descemet's endothelial keratoplasty, suture management of acute hydrops, DALK-triple and Fogla's mini DALK. The discovery and knowledge of the layer has introduced paradigm shifts in our age old concepts of Descemet's membrane detachment, acute corneal hydrops in keratoconus and Descemetoceles, with impact on management approaches. It has been shown to contribute to the pathology and clinical signs observed in corneal infections and some corneal dystrophies. Early evidence suggests that it may have a role in the pathogenesis of keratoconus in relation to its elastin content. Its contribution to corneal biomechanics and glaucoma are subjects of current investigations.

Femtosecond laser deep lamellar keratoplasty.

We aimed to develop a novel and effective technique for creating a smooth deep lamellar dissection of the cornea using a femtosecond (FS) laser for deep anterior lamellar keratoplasty (DALK), we conducted a retrospective eye bank study. Thirteen fresh human corneas were mounted on an artificial anterior chamber, and deep lamellar cuts were made with a 500-kHz VisuMax FS laser at a level of 50-80 µm anterior to the Descemet's membrane (DM). A posterior diameter of 8 mm with a side cut angle of 110° was used for the anterior penetrating side cut. The anterior lamellar tissue was bluntly dissected. The residual posterior stromal beds and side cuts were examined with microscopy and intraoperative optical coherence tomography (OCT) and post-cut endothelial cell evaluations. All corneas revealed a smooth residual posterior stromal bed without any visible irregularities or ridges by microscopy and OCT imaging. Six corneas were suitable for post-cut endothelial cell evaluation 2 days after laser cut, with no significant endothelial cell loss post-laser and blunt dissection of the posterior stroma. FS laser deep lamellar keratoplasty utilizing an ultrafast laser to produce a smooth deep stromal dissection followed by blunt dissection and removal of the anterior stromal tissue yields a consistent and smooth residual stromal bed. The creation of a smooth lamellar dissection in the deep posterior cornea may result in more consistent DALK without the need for air bubble or manual baring of DM that has the risk for DM perforation.

A New Pre-descemetic Corneal Ring (Neoring) in Deep Anterior Lamellar Keratoplasty for Moderate-Advanced Keratoconus: A Pilot 2-Year Long-Term Follow-Up Study.

Purpose: To assess the outcomes of implanting a new polymethylmethacrylate (PMMA) ring (Neoring; AJL Ophthalmic) in pre-descemet deep anterior lamellar keratoplasty (PD-DALK) procedure for moderate-advanced keratoconus. Methods: This prospective study included 10 eyes of 10 patients with moderate-advanced keratoconus who underwent PD-DALK with Neoring implantation. Neoring was implanted in a pre-descemetic pocket. The post-operative examination included refraction, corrected distance visual acuity (CDVA), corneal tomography, and endothelial cell density (ECD). The root mean squares (RMSs) for coma-like aberrations and spherical aberration were evaluated for a pupil size of 4.5 mm. The junctional graft (Tg) and host (Th) thicknesses were measured. The post-operative follow-up was 24 months. Results: Post-operative CDVA was 0.82 ± 0.14 (decimal scale), 100% of the eyes achieved a CDVA of 0.7 (decimal scale). The refractive cylinder was -2.86 ± 1.65 2-years after surgery. No eyes had a post-operative refractive cylinder ≥5.00 D and in five eyes (50%), it was ≤2.50 D. At the last visit, the mean keratometry was 45.64 ± 1.96 D, the RMS for coma-like aberrations was 0.30 ± 0.15 µm and spherical aberration was 0.22 ± 0.09. The mean ECD remains without changes over the follow-up (P = 0.07). At the last visit, Tg and Th were 679.9 ± 39.0 and 634.8 ± 41.2 µm, respectively. The thickness of the complex (host-Neoring) was 740.6 ± 35.6 µm. In all cases, this thickness was thicker than Tg. Conclusion: The results of this study suggest that PD-DALK along Neoring implantation is a viable, effective, and safe option to optimize the post-operative results for moderate-severe keratoconus.

Burr-Assisted Anterior Lamellar Keratoplasty (DALK) in Patients with Corneal Stromal Scarring: A Case Series.

PURPOSE: To describe a modified technique of deep anterior lamellar keratoplasty (DALK) assisted by diamond ophthalmic burr (DOB) in two patients with corneal stromal scarring. METHODS: Two patients with corneal stromal scarring underwent a modified DALK technique with corneal stromal polishing assisted by a DOB until the level of the Descemet membrane. RESULTS: There were no intra- or postoperative complications. Six months postoperatively, the corneal graft was clear, while corrected distance visual acuity improved in both cases. CONCLUSIONS: Burr-assisted DALK seems to represent an alternative surgical technique in patients with corneal stromal scarring.

Assessments of tear meniscus height, tear film thickness, and corneal epithelial thickness after deep anterior lamellar keratoplasty.

OBJECTIVE: To assess the lower tear meniscus height (LTMH), central tear film thickness (CTFT), and central corneal epithelial thickness (CCET) after deep anterior lamellar keratoplasty (DALK). METHODS: This was a retrospective cross-sectional study of 20 patients who had DALK in one eye over a three-month period. LTMH, CTFT, and CCET of the operated eyes and the unoperated fellow eyes were measured using high-definition optical coherence tomography (HD-OCT). Correlations between three OCT assessments and age, time following surgery, graft size, bed size, and the number of residual sutures were analyzed. RESULTS: Compared to patients with keratoconus, patients with other corneal conditions had significantly higher CCET in the fellow eye (P=0.024). For all patients, CCET in the operated eye was significantly negatively correlated with the number of residual sutures (R=-0.579, P=0.008), and was significantly positively correlated with time following surgery (R=0.636, P=0.003). In the fellow eye, a significant positive correlation was found between age and CCET (R=0.551, P=0.012), and a significant negative correlation between age and CTFT (R=-0.491, P=0.028). LTMH was found to be significantly correlated between operated and fellow eyes (R=0.554, P=0.011). There was no significant correlation between LTMH and age, bed/graft size, time following surgery, or residual sutures (all possible correlations, P>0.05). CONCLUSIONS: Patients with keratoconus tend to have a thinner central corneal epithelium. Corneal epithelium keeps regenerating over time after DALK. DALK did not induce a significant change in tear volume compared with the fellow eye. Postoperative tear function might depend on an individual's general condition, rather than on age, gender, bed/graft size, time following surgery, or residual sutures.

Efecto Hipotensor de la Trabeculoplastia Láser / Hypotensive Eff ect of Laser Trabeculoplasty

Objetivo: Reportar el desenlace luego de 12 meses de seguimiento, en pacientes en los que se realizó una queratoplastia lamelar anterior profunda (DALK) asistida con láser de femtosegundo. Metodología: Se realizó un estudio descriptivo, retrospectivo, mediante revisión de historias clínicas de pacientes sometidos a DALK asistida con láser de femtosegundo (Wavelight FS-200 ® Alcon. Forth Worth, Texas), utilizando la configuración de zig-zag. Las indicaciones de DALK incluyeron queratocono, ectasia post LASIK y leucoma como secuela de queratitis infecciosa. Las variables estudiadas fueron agudeza visual mejor corregida, cilindro queratométrico, refracción final y complicaciones intra y post operatoria. Resultados: En total se incluyeron 10 ojos de 10 pacientes, en todos los ojos se llevó a cabo con éxito femto-DALK y no hubo ninguna complicación intra operatoria. En el postoperatorio se presentó un caso de rechazo estromal, un caso de hipertensión ocular secundario a esteroides y un caso de retraso en la cicatrización. El seguimiento promedio fue de 13, 1 meses (R= 12 ­ 15 meses). La Agudeza Visual Mejor Corregida (AVMC) preoperatoria promedio fue LogMAR 0,96 (R= 0,54 ­ 1,60). La AVMC postoperatoria promedio a los 12 meses fue 0,10 (R= 0,00 ­ 0,17). El equivalente esférico preoperatorio medio fue -12,6 Dioptrias (D) (R= -5,0 a -15,0D) y el postoperatorio fue -2,57 D (R= -0,50 a -6,25 D). El astigmatismo queratométrico preoperatorio medio de -11.5D (R= -7.0 a -23D) y el postoperatorio -2,4 D (R= -0,75 a -3,75 D). Conclusión: La femto-DALK en configuración Zig-Zag es un procedimiento confiable, con baja tasa de complicaciones intra y postoperatorias. El resultado refractivo es comparable con la queratoplastia penetrante, y ofrece beneficios sobre factores de estabilidad biomecánica y recuperación del paciente en el primer año postoperatorio.

Objective: The aim was to report the surgical outcomes of twelve months follow-up after femtosecond laser assisted Zig-zag confi guration combined with Deep Anterior Lamellar Keratoplasty (Femto-DALK). Methods: A descriptive, retrospective study, which evaluated and assisted medical records of patients who had undergone deep anterior lamellar keratoplasty (DALK) femtosecond laser assisted. Ten eyes of ten consecutive patients underwent femtosecond (Wavelight FS-200 ® Alcon. Forth Worth, Texas) laser-assisted zig-zag configuration combined with Anwar´s big-bubble technique DALK, from April 2012 to December 2013. The diagnosis of the patients were keratoconus, corneal ectasia and scarring following infectious keratitis. Variables measured were: Best corrected visual acuity, keratometric corneal cylinder, final refraction and intraand postoperative complications were analyzed. Results: The procedure was performed without any complications in all patients. There was only a single case of stromal graft rejection, a case of corticosteroid induced ocular hypertension and a case of delayed corneal epithelial healing. Mean follow-up period was 13.1 months (R= 12­15 months). The mean preoperative BCVA was LogMAR 0,96 (R= 0,54 ­ 1,60). The mean postoperative BCVA at 12th month was 0,054 (R= 0,00 ­0,09). The mean preoperative spherical equivalent (SE) was -12,6 Diopter (D) (R= -5,0 to -24,0D) and postoperative SE was -2,50 D (R=-0,50 to -6,25 D). The measurements of keratometric corneal cylinder preoperative was -11.5D (R= -7.0 a -23D) and postoperative refractive cylinder was -2,4 D (R=-0,75 to -4,00 D). Conclusion: Laser-assisted zig-zag configuration combined with Anwar´s big-bubble technique DALK is a safe procedure. The rate of intra and postoperative complications is low. The refractive outcomes are comparable to penetrating keratoplasty, but better biomechanical stability of the cornea and a faster visual recovery with femtoDALK procedure.

Queratoplastia Lamelar Anterior Profunda asistida con láser de femtosegundo configuración Zig-Zag: Resultados a un año de seguimiento / Deep Anterior Lamellar Keratoplasty in a Zig-Zag Pattern Assisted by Femtosecond Laser: 1 year follow up

Objetivo: Reportar el desenlace luego de 12 meses de seguimiento, en pacientes en los que se realizó una queratoplastia lamelar anterior profunda (DALK) asistida con láser de femtosegundo. Metodología: Se realizó un estudio descriptivo, retrospectivo, mediante revisión de historias clínicas de pacientes sometidos a DALK asistida con láser de femtosegundo (Wavelight FS-200 ® Alcon. Forth Worth, Texas), utilizando la configuración de zig-zag. Las indicaciones de DALK incluyeron queratocono, ectasia post LASIK y leucoma como secuela de queratitis infecciosa. Las variables estudiadas fueron agudeza visual mejor corregida, cilindro queratométrico, refracción final y complicaciones intra y post operatoria. Resultados: En total se incluyeron 10 ojos de 10 pacientes, en todos los ojos se llevó a cabo con éxito femto-DALK y no hubo ninguna complicación intra operatoria. En el postoperatorio se presentó un caso de rechazo estromal, un caso de hipertensión ocular secundario a esteroides y un caso de retraso en la cicatrización. El seguimiento promedio fue de 13, 1 meses (R= 12 ­ 15 meses). La Agudeza Visual Mejor Corregida (AVMC) preoperatoria promedio fue LogMAR 0,96 (R= 0,54 ­ 1,60). La AVMC postoperatoria promedio a los 12 meses fue 0,10 (R= 0,00 ­ 0,17). El equivalente esférico preoperatorio medio fue -12,6 Dioptrias (D) (R= -5,0 a -15,0D) y el postoperatorio fue -2,57 D (R= -0,50 a -6,25 D). El astigmatismo queratométrico preoperatorio medio de -11.5D (R= -7.0 a -23D) y el postoperatorio -2,4 D (R= -0,75 a -3,75 D). Conclusión: La femto-DALK en confi guración Zig-Zag es un procedimiento confiable, con baja tasa de complicaciones intra y postoperatorias. El resultado refractivo es comparable con la queratoplastia penetrante, y ofrece beneficios sobre factores de estabilidad biomecánica y recuperación del paciente en el primer año postoperatorio.

Objective: The aim was to report the surgical outcomes of twelve months follow-up aft er femtosecond laser assisted Zig-zag configuration combined with Deep Anterior Lamellar Keratoplasty (Femto-DALK). Methods: A descriptive, retrospective study, which evaluated and assisted medical records of patients who had undergone deep anterior lamellar keratoplasty (DALK) femtosecond laser assisted. Ten eyes of ten consecutive patients underwent femtosecond (Wavelight FS-200 ® Alcon. Forth Worth, Texas) laser-assisted zig-zag configuration combined with Anwar´s big-bubble technique DALK, from April 2012 to December 2013. The diagnosis of the patients were keratoconus, corneal ectasia and scarring following infectious keratitis. Variables measured were: Best corrected visual acuity, keratometric corneal cylinder, final refraction and intraand postoperative complications were analyzed. Results: The procedure was performed without any complications in all patients. There was only a single case of stromal graft rejection, a case of corticosteroidinduced ocular hypertension and a case of delayed corneal epithelial healing. Mean follow-up period was 13.1 months (R= 12­15 months). The mean preoperative BCVA was LogMAR 0,96 (R= 0,54 ­ 1,60). Th e mean postoperative BCVA at 12th month was 0,054 (R= 0,00 ­0,09). The mean preoperative spherical equivalent (SE) was -12,6 Diopter (D)(R= -5,0 to -24,0D) and postoperative SE was -2,50 D (R=-0,50 to -6,25 D). The measurements of keratometric corneal cylinder preoperative was -11.5D (R= -7.0 a -23D) and postoperative refractive cylinder was -2,4 D (R=-0,75 to -4,00 D). Conclusion: Laser-assisted zig-zag configuration combined with Anwar´s big-bubble technique DALK is a safe procedure. The rate of intra and postoperative complications is low. The refractive outcomes are comparable to penetrating keratoplasty, but better biomechanical stability of the cornea and a faster visual recovery with femtoDALK procedure.

Peripheral deep anterior lamellar keratoplasty using a cryopreserved donor cornea for Terrien's marginal degeneration.

OBJECTIVE: To evaluate the clinical efficacy of peripheral deep anterior lamellar keratoplasty (DALK) using a cryopreserved donor cornea for Terrien's marginal degeneration (TMD). METHODS: Thirty-one eyes of 27 patients with TMD underwent peripheral DALK using cryopreserved donor corneas. According to the distance between the inner edge of the lesion and the limbus, a ring-shaped or D-shaped DALK was performed. All grafts were stored at -20 °C. Cryopreserved corneoscleral rims were prepared for ring-shaped grafts and cryopreserved whole eyeballs were prepared for D-shaped grafts. The general conditions, intraoperative performance, postoperative corneal reconstruction, astigmatism, best corrected visual acuity (BCVA), and various complications were analyzed. RESULTS: Ring-shaped DALK was performed in 28 eyes and D-shaped DALK was performed in 3 eyes. Postoperative follow-up time was (28.4±24.8) months. There was evidence of inflammation before surgery in 12 eyes (38.7%) and intraoperative perforation occurred in 13 eyes (41.9%). The corneal structures of all eyes were reconstructed. Postoperative astigmatism and BCVA showed improvement (both P=0.00) except for cases that underwent D-shaped DALK. Ten eyes (32.2%) developed transient ocular hypertension and one eye (3.2%) developed secondary glaucoma. No primary disease recurrence or corneal allograft rejection was observed. CONCLUSIONS: Peripheral DALK for TMD using cryopreserved donor tissue is an effective technique that eliminates rejection and extends the use of donor eyes. Inflammatory history or intraoperative perforation has no adverse effect on graft recovery. However, D-shaped DALK did not achieve good visual outcomes.