Artificial cornea transplantation and visual rehabilitation: an integrative review / Transplante de córnea artificial e reabilitação visual: uma revisão integrativa

ABSTRACT Due to the development of complications and the biocompatibility and scarcity of transplant donor tissues, artificial corneas, which can be used for the rehabilitation of optical functions, have been developed. The current study aimed to analyze the visual rehabilitation effects of the Boston type I keratoprosthesis, Boston type II keratoprosthesis, Aurolab keratoprosthesis, osteo-odonto-keratoprosthesis, and tibial bone keratoprosthesis. Results showed that the Boston type I keratoprosthesis was the most effective for visual rehabilitation in patients with moist ocular surfaces. The Aurolab keratoprosthesis had a lower efficacy for visual rehabilitation. Nevertheless, it is still a viable option for individuals in economically restricted countries. In patients with dry eyes, the Boston type II keratoprosthesis was associated with the best visual rehabilitation. However, the final visual acuity of patients who received osteo-odonto-keratoprosthesis and tibial bone keratoprosthesis implantation was not evaluated as the necessary information was not available.

RESUMO Em decorrência de complicações, da biocompatibilidade e da escassez de tecido doador para transplantes de córnea natural, foram elaboradas córneas artificiais que são potenciais para reabilitar funções ópticas. Nessa perspectiva, objetivou-se a análise da eficácia da reabilitação visual entre os implantes: Boston tipo I, Boston tipo II, Aurolab, osteo-odonto-ceratoprótese e ceratoprótese de Osso Tibial. De modo geral, a princípio observou-se uma tendência de melhoria da Best-corrected visual acuity em todos os tipos de lentes, mas considerável queda durante acompanhamento a longo prazo. O dispositivo com melhor reabilitação visual em pacientes com superfícies oculares úmidas é a Boston tipo I, seguida pela Aurolab, que é economicamente viável em países emergentes. Ao considerar pacientes com olhos secos, o implante de Boston tipo II apresenta maior reabilitação visual. Por fim, em virtude de não apresentarem dados equiparáveis, as lentes osteo-odonto-ceratoprótese e de osso tibial não puderam ser analisadas.

Argus Ⅱ retinal prosthesis system:an update / 中华实验眼科杂志

Argus Ⅱ retinal prosthesis system (Argus Ⅱ;Second Sight Medical products,Sylmar,CA) is the first prosthetic retinal device approved for humanitarian use by both FDA in America and CE in Europe.It is a potential treatment for patients with end-stage outer retinal diseases.The system contains several parts,the camera first captures image and transfers it into electrical stimulating parameters conveying spatial-temporal information.The microelectrode epiretinal array then stimulate underlying bipolar cells and retinal ganglion cells.Patients present significant increases on levels of discrimination,target localization,motion detection and navigation.Possible adverse events include conjunctival erosion,hypotony and culture-negative presumed endophthalmitis.Future developments of the Argus Ⅱ system will not only comprise upgrading of image processing software and hardware,but also further disclosing retinal and visual signal processing mechanism.

Anterior segment optical coherence tomography findings in type I Boston keratoprosthesis / Achados de tomografia de coerência óptica do seguimento anterior em ceratoprótese de Boston tipo I

ABSTRACT Purpose: To report the results of high-resolution anterior segment optical coherence tomography of patients implanted with a type 1 Boston keratoprosthesis (KPro). Methods: The retrospective study cohort included 11 eyes of 11 patients (average age, 58.4 years; range, 34-83 years). All subjects underwent anterior segment optical coherence tomography at a single posteoperative time point. The main outcome measures were retro-backplate and retro-optic membrane formation, thinning and gap formation of the corneal carrier graft (melting), and degree of angle closure. Results: Preoperative diagnoses included chemical burn (55%), failed corneal transplant (36%), and Stevens-Johnson syndrome (9%). The mean postoperative follow-up duration was 38.5 (range, 12-72) months. The most frequent findings of anterior segment optical coherence tomography were retroprosthetic membrane formation (63%, 7/11), thinning of the corneal carrier graft (melting; 55%, 6/11), and a narrow or closed angle (91%, 10/11). Other less common findings were epithelial growth over the optic surface and periprosthetic cyst formation. Retroprosthetic membrane formation was observed in all patients with melting (6/11). Conclusions: Detailed postoperative examination and visualization of subtle changes of keratoprosthesis implanted eyes by slit lamp biomicroscopy are often difficult. Anterior segment optical coherence tomography is a useful, noninvasive, and quantitative imaging technique that provides useful information to postoperatively monitor the anatomic stability of an implanted keratoprosthesis.

RESUMO Objetivos: Reportar os resultados das imagens de pacientes com Ceratoprótese de Boston tipo I (KPro) usando tomografia de coerência óptica de alta resolução do seguimento anterior (AS-OCT). Métodos: Nós realizamos um estudo retrospectivo de pacientes submetidos à KPro. Um total de 11 olhos de 11 pacientes foram incluídos. As imagens de AS-OCT foram realizadas em um único tempo de pós-operatório. Os principais resultados incluem formação de membrana retroprostética atrás do prato posterior e atrás do cilindro ótico, afinamento e lacunas na córnea doadora (melt) e graus de ângulo fechado. Resultados: Os diagnósticos pré-operatórios inclui queimadura química (55%), falência pós transplante de córnea (36%) e síndrome de Stevens Johnson (9%). A idade média foi de 58.4 anos (escala, 34-83 anos). A média de tempo de pós-operatório foi de 38.5 meses (escala, 12-72 meses). Os achados mais frequentes de AS-OCT foram: membrana retroprostética, 63% (7/11); afinamento da córnea doadora (melting), 55% (6/11); angulo estreito ou fechado, 91% (10/11). Outros achados menos comuns foram crescimento epitelial sobre a superfície ótica e cistos periprostéticos. Todos os pacientes com melting (6/11) apresentaram membrana retroprostética. Conclusões: O exame pós-operatório e a visualização detalhada das mudanças em olhos com KPro pela lâmpada de fenda pode ser difícil. AS-OCT é uma técnica de imagem útil, não invasiva e quantitativa que permite o monitoramento da estabilidade anatômica no seguimento de KPro implantadas.

A new method for extracting visual saliency map for visual prosthesis / 国际生物医学工程杂志

Objective Salient regions may express the main content (salient objects) in an image or scene.Since the number of implanted electrodes for visual prosthesis is limited,only the low-resolution image is used.Extraction of the salient regions may help capture salient objects in the scenes of visual prosthesis.Methods Salient regions detected by Itti model,one of salient detection models,have some differences with human visual perceptions and its salient objects boundary are also unclear.The Itti model was optimized by removing the orientation and the color characteristics,and converting the RGB image in an image or scene into the HSI color space with three new feature components of hue,saturation and intensity.In saliency map,the ratio of the salient point area in salient objects regions and the total salient point area was defined as salient accuracy and computed,which was used to compare the effects of the two methods of extracting salient map.Results Compared with the Itti method for extracting saliency map,the salient accuracy of the improved method was increased by about 20％,and the time for detecting the same salient regions by our method was shorter by nearly 50％.Conclusions The proposed algorithm can be an alternative method to extract salient map from a complex image or scene for retinal prosthesis with higher salient accuracy and less running time.