Intraoperative collagen imaging of sutured cornea: A way towards managing post-penetrating keratoplasty astigmatism.

The birefringent nature of the human cornea plays an important role in comprehending its structural behavior in both diseased and surgical conditions. During corneal transplantation, irregular astigmatism is a common post-surgical complication that depends on the characteristics of suturing. Four human cadaver corneas are subjected to an in-vitro model of a typical full-thickness penetrating keratoplasty (PK) procedure using 16 simple interrupted 10-0 vicyrl sutures. The birefringence of these four corneas is analyzed using digital photoelasticity and compared with the control cornea (without PK). It is found that the sutures and their mutual interaction influence the morphology of the peripheral birefringence of the cornea. The findings of the present investigation are pertinent to intraoperative suture management during PK. Results suggest conserving the typical diamond-shaped morphology of peripheral birefringence would ensure uniform distribution of sutures. Therefore, birefringence imaging could be useful in suture management to ensure proper apposition of the graft-host junction, thus minimizing the risk of irregular astigmatism.

Effect of Upper Lid Blepharoplasty Surgery on Corneal Topography and Corneal High-Order Aberrations.

The objective of this study was to prospectively investigate the effect of upper eyelid blepharoplasty surgery for dermatochalasis on corneal topographic data and high-order aberrations (HOAs). Fifty eyelids of 50 patients with dermatochalasis who underwent upper lid blepharoplasty surgery were prospectively studied. A Pentacam (Scheimpflug camera, Oculus) device was used to measure corneal topographic values, astigmatism degree, and HOAs before and at 2 months after upper eyelid blepharoplasty. The mean age of the patients included in the study was 55.96 ± 12.4 years, 40 (80%) were female and 10 (20%) were male. We found no statistically significant difference in the pre-and postoperative values of corneal topographic parameters (p > 0.05 for all). In addition, we observed no significant postoperative change in the root mean square values of low, high, and total aberration values. In HOAs, we detected no significant change in spherical aberration, horizontal and vertical coma, and vertical trefoil; we only found a statistically significant increase in horizontal trefoil values after surgery (p < 0.05). In our study, we found that upper eyelid blepharoplasty did not cause significant changes in corneal topography, astigmatism, and ocular HOAs. However, studies are reporting different results in the literature. For this reason, it is important for patients considering upper eyelid surgery to be warned about visual changes that may occur after surgery.

Understanding Corneal Epithelial Thickness Mapping.

Corneal epithelial thickness (CET) and the regional variations in response to changes in corneal architecture and biomechanics have recently drawn the interest of corneal surgeons. Corneal epithelium possesses the tremendous capability of remodeling and changing its thickness. This remodeling of corneal epithelium takes place in response to underlying stromal irregularities which can result from a variety of corneal disorders including corneal ectasia. Measurement of CET can reveal the underlying stromal abnormalities and supplement in early diagnosis of corneal disorders especially corneal ectasia which has been one of the leading challenges in planning corneal refractive surgery. A significant number of patients ends up in ectasia after refractive surgery and the most common cause of this complication is the presence of preoperative subclinical keratoconus. Furthermore, postoperative complications of corneal refractive surgery are partly masked by epithelial remodeling and make the diagnosis and management difficult and extremely challenging. This leads not only to unpredictable visual and refractive outcome but also the need of multiple interventions to treat these complications. Although corneal tomography is considered as gold standard in the detection and diagnosis of corneal ectasia, a small number of subclinical cases may still go undetected. In this review, we have highlighted the underlying mechanism of epithelial remodeling, the devices and imaging modalities used to measure CET, and application of epithelial mapping in the diagnosis and management of various corneal disorders.

Corrección del queratocono con microlentes de alta excentricidad / Correction of keratoconus with highly eccentric microlenses

La adaptación de lentes de contacto en queratocono avanzado se torna compleja por la gran excentricidad de la zona apical. El lente de contacto rígido de diámetro pequeño con curva posterior parabólica o hiperbólica (diseño de alta excentricidad) es una excelente opción para el queratocono con ectasias de diámetro pequeño y alta elevación. Permite proteger la zona apical del cono y hace confortable la adaptación del lente en pacientes que aún no justifican una queratoplastia. El objetivo de este trabajo es mostrar cómo una adecuada adaptación permite retrasar o evitar una cirugía de alta complejidad para el paciente(AU)

The adaptation of contact lenses to treat advanced keratoconus is complex due to the great eccentricity of the apical area. The small diameter rigid contact lenses with parabolic or hyperbolic posterior curve (high eccentricity design) are an excellent choice for keratoconus with small diameter and highly elevated ectasias. It allows protecting the apical area of the cone and makes the adaptation of the lens more comfortable in those patients who do not require keratoplasty yet. The objective of this work is to show how an appropriate adaptation allows to retard or to avoid a surgery of high complexity for the patient(AU)

Alteraciones corneales en pacientes diabéticos / Corneal alterations in diabetic patients

La diabetes mellitus, afección frecuente a nivel mundial, tiene gran impacto en la sociedad no solo por su alta prevalencia, sino por sus complicaciones crónicas y su alta mortalidad. Afecta a unos 180 millones de personas en el mundo. La prevalencia de la diabetes (tipos I y II) se estima en el 13 % en pacientes mayores de 60 años. La estructura corneal sufre modificaciones en los pacientes diabéticos; la hiperglucemia afecta la hidratación de la córnea, y con esto varía el espesor corneal y aparecen cambios queratométricos visibles mediante topografía corneal. Las córneas de los pacientes con diabetes presentan alteraciones epiteliales, estromales y endoteliales. Además, existe una disminución de la permeabilidad endotelial durante la fase de hipoxia, que relacionan estos efectos de la diabetes en las células endoteliales. El objetivo de nuestro estudio es abordar las diferentes alteraciones corneales en los pacientes diabéticos(AU)

Diabetes Mellitus, a frequent disease worldwide, has a great impact on the society, not only for their high prevalence, but for their chronic complications and high mortality. It has an effect on 180 million people approximately in the world. The prevalence of diabetes (type I and II) is estimated to be 13 % in patients older than 60 years. The corneal structure undergoes changes in diabetic patients; the hyperglycemia affects the corneal hydration and causes variations in the corneal thickness, with occurrence of visible keratometric changes detected in the corneal topography. The corneas of diabetic patients show epithelial, stromal and endothelial alterations. Additionally, there is decrease in endothelial permeability during the phase of hypoxia that relate these effects of diabetes in the endothelial cells. The objective of our study was to deal with the different corneal alterations in diabetic patients(AU)

One-step transepithelial topography-guided ablation in the treatment of myopic astigmatism.

PURPOSE: To evaluate one-step topography-guided transepithelial ablation in the treatment of low to moderate myopic astigmatism using a 1KHz excimer laser. METHODS: Retrospective study of 117 consecutive eyes available for evaluation 12 months after surgery. Pre- and post-operative visual and refractive data as well as post-operative pain and haze were analyzed. A novel technique integrating custom refractive- and epithelial- ablation in a single uninterrupted procedure was used. RESULTS: The mean pre-operative spherical equivalent (SE) and the mean cylinder were: -3.22 diopters (D) ±1.54 (SD) (range -0.63 to -7.25 D) and -0.77 D ±0.65 (range 0 to -4.50 D), respectively. At 12 months after surgery: no eyes lost ≥2 lines of corrected distant visual acuity (CDVA). Safety and efficacy indexes were 1.27 and 1.09, respectively. Uncorrected distant visual acuity (UDVA) was ≥20/20 in 96.6% of the eyes. Manifest refraction spherical equivalent was within ±0.5 D of the desired refraction in 93.2% of the eyes. Average root mean square (RMS) wavefront error measured at central 6 mm, increased from 0.38 pre-operatively to 0.47 µm post-operatively. Refractive stability was achieved and sustained 1 month after surgery. No visually significant haze was registered during the observation period. Post-operative pain was reported in 4.5% of patients. CONCLUSIONS: One-step transepithelial topography-guided treatment for low to moderate myopia and astigmatism performed with a 1 KHz laser, provided safe, effective, predictable and stable results with low pain and no visually significant haze.

Transferring wavefront measurements into corneal ablations: an overview of related topics.

We give an overview of possible side effects that are specific for, or of particular relevance in, customized treatments. Certain processes involved in customized ablations have the potential to alter the quality of the optical correction. Professionals associated with customized treatment should be informed and trained with respect to possible sources of error.

Pterígio e alterações da curvatura corneana / Pterygium and corneal curvature changes

Objetivo: Avaliar as mudanças de curvatura corneana ocorridas após a exérese do pterígio (Pt). Métodos: Foi realizado estudo prospectivo em 49 olhos com Pt primário avaliando-se idade, sexo, tamanho [grau (G)1, GII, GIII e GIV] e a morfologia da lesão (atrófica ou carnosa) à biomicroscopia. Todos os pacientes foram submetidos ao exame de videoceratoscopia computadorizada e ceratometria no pré-operatório (pré-op), e no 30e 60 dias após a cirurgia. Os dados foram submetidos à análise estatística. Resultados: 63 por cento dos indivíduos avaliados eram do sexo masculino e 80 por cento tinham mais de 41 anos. Houve predomínio dos Pt atróficos (77 por cento), GII e GIII (39 por cento e 28 por cento, respectivamente). Observou-se manutenção do astigmatismo (Astg) presente no pré-operatório no Segundo mês pós-operatório (PO), principalmente nos portadores de Pt GI e GIL A variação no valor de K do primeiro mês para o segundo mês de PO foi pequena. As variações observadas estiveram mais relacionadas com o tamanho do pterígio, do que com a idade do paciente, ou com as suas características morfológicas. Conclusões: A avaliação ceratométrica e topográfica da córnea em portadores de pterígio no pré e no pós-operatório mostrou, que os Pt menores, (GI e GII) estão associados com graus menores dé astigmátismo e no pós-operatório a córnea sofre menos mudanças que nos GIII e GIV+ Após 2 meses da cirurgia, o padrão da curvatura corneana é semelhante ao do pré-operatório, na maioria dos pacientes.

Intraocular lens power calculations using corneal topography after photorefractive keratectomy.

PURPOSE: To report two patients (two eyes) with previous photorefractive keratectomy, who subsequently underwent cataract extraction years later. DESIGN: Case reports. METHODS: Corneal topography was used to determine corneal power used in intraocular lens power calculations. RESULTS: In two eyes of two patients, intraocular lens calculations after photorefractive keratectomy were inadequate, which resulted in a hyperopic postoperative refractive error requiring implantation of a piggyback intraocular lens. CONCLUSION: Corneal topography to determine corneal power in patients with previous photorefractive keratectomy may result in unpredictable intraocular lens power calculations. The clinical history method is the standard to determine corneal power and should be considered in intraocular lens calculations before cataract surgery. We recommend supplying refractive patients with preoperative data for use in future formulas for intraocular lens selection.