Étude in vivo de l’accommodation naturelle chez un sujet albinos

Optical Coherence Tomography Reveals Sigmoidal Crystalline Lens Changes during Accommodation

This study aimed to quantify biometric modifications of the anterior segment (AS) during accommodation and to compare them against changes in both accommodative demand and response. Thirty adults, aged 18–25 years were rendered functionally emmetropic with contact lenses. AS optical coherence tomography (AS-OCT) images were captured along the 180° meridian (Visante, Zeiss Meditec, Jena, Germany) under stimulated accommodative demands (0–4 D). Images were analysed and lens thickness (LT) was measured, applying a refractive index correction of 1.00. Accommodative responses were also measured sequentially through a Badal optical system fitted to an autorefractor (Shin Nippon NVision-K 5001, Rexxam, Japan). Data were compared with Dubbelman schematic eye calculations. Significant changes occurred in LT, anterior chamber depth (ACD), lens centroid (i.e., ACD + LT/2), and AS length (ASL = ACD + LT) with accommodation (all p < 0.01). There was no significant change in CT with accommodation (p = 0.81). Measured CT, ACD, and lens centroid values were similar to Dubbelman modelled parameters, however AS-OCT overestimated LT and ASL. As expected, the accommodative response was less than the demand. Interestingly, up until approximately 1.5 D of response (2.0 D demand), the anterior crystalline lens surface appears to be the primary correlate. Beyond this point, the posterior lens surface moves posteriorly resulting in an over-all sigmoidal trajectory. he posterior crystalline lens surface demonstrates a sigmoidal response with increasing accommodative effort.

[Spectral-domain optical coherence tomography in anterior segment imaging: the 3rd dimension]

PURPOSE

Anterior segment imaging using optical coherence tomography (OCT) time domain technology has been used for many years. When it appeared, it was a promising technique in the analysis of the anterior segment, making it possible to reach a definition of the ocular structures comparable with histology. Now with new-generation OCT, it is possible to perform high-definition and three-dimensional imaging.

MATERIAL AND METHOD

A 3D OCT-1000 (Topcon, Tokyo, Japan) parameterized to obtain high-definition and 3D imaging of the iridocorneal structures.

RESULTS

We present a collection of images obtained using this technique.

DISCUSSION

Based on a very sophisticated tool for retinal and glaucoma imagery, it is now possible to obtain very-high-quality imaging of the anterior segment, which, with its great versatility, increases the value of acquiring this type of device.

CONCLUSIONS

The potential of 3D OCT-1000, already a very good exam for the posterior segment, and the only one to perform anterior segment three-dimensional imaging in a single acquisition, should not be neglected.

[OCT and neovascular glaucoma]

INTRODUCTION

Neovascular glaucoma is a chronic and sight-threatening disease. Four different grades have been described. Anterior chamber optical coherence tomography (OCT) is a new imaging technique allowing the visualization of the anterior segment. The purpose of our study was to describe the appearance of the different neovascular glaucoma grades with the OCT in order to refine the clinical analysis of this disease.

PATIENTS AND METHODS

Eleven patients (nine men and two women) with different grades of neovascular glaucoma were analyzed in this study. Neovascular glaucoma complicated central retinal vein occlusion in seven patients and diabetic retinopathy in four patients. All patients had bilateral biomicroscopical examination and OCT analysis. OCT images and clinical examination were then compared.

RESULTS

No modifications could be observed using OCT in patients with grade 1 neovascular glaucoma. For grade 2, a slightly hyper-reflective linear iris secondary to neovascularization was observed. For grade 3, OCT images showed a thickened hyper-reflective iridocorneal angle with possible iridocorneal synechiae. For grade 4, the iridocorneal angle was closed and associated with iris contraction and uveae ectropion.

CONCLUSION

OCT is a new promising technique for the precise analysis of different grades of neovascular glaucoma. It certainly helps in the management of such cases.

[Contribution of confocal microscopy and anterior chamber OCT to the study of corneal endothelial pathologies]

PURPOSE

To describe the appearance of various endothelial diseases with in vivo confocal microscopy and anterior chamber optical coherence tomography (AC OCT).

METHODS

In this study, ten patients with five different corneal endothelial pathologies were evaluated. Three patients had cornea guttata, three had corneal endothelial precipitates, two had irido-corneo-endothelial (ICE) syndrome, one had endothelial folds, and one had breaks in the Descemet membrane. All patients had bilateral ophthalmologic examinations, in vivo confocal microscopy, and AC OCT analysis.

RESULTS

In cases of cornea guttata, AC OCT showed a finely embossed line corresponding to the empty intercellular cavities found with in vivo confocal microscopy. Corneal endothelium precipitates had the aspect of round formations suspended with the endothelium. Iris atrophy and irido-corneal synechiae resulting from ICE syndrome were precisely visualized with the AC OCT.

CONCLUSION

High-resolution images of the anterior segment could be obtained using the AC OCT. Associated with in vivo confocal microscopy, these two new imaging techniques provide a precise evaluation of endothelial pathologies.

Cataracte congénitale

Cataract is a loss of lens transparency because of a protein alteration. Etiopathogenesis is poorly understood but new mutations of different developmental genes involved are found in 25% of cases. Frequency of onset, particularly when different ocular development anomalies occur, is related to the lens induction phenomena on the eye's anterior segment structure during embryologic development. Genetic transmission is often found on the dominant autosomal mode. Diagnosis is based on a complete and detailed examination of the eye, often with general anaesthesia. This condition predisposes children to later, sometimes serious amblyopia. Different clinical aspects can be observed: from cataract with ocular and/or systemic anomalies to polymalformative syndrome, skeletal, dermatological, neurological, metabolic, and genetic or chromosomal diseases. A general systematic pediatric examination is necessary. Congenital cataract requires first and foremost early diagnosis and a search for all etiologies. Surgical treatment is adapted case by case but it has progressed with the quality of today's intraocular lenses even if systematic implantation continues to be debated. Life-long monitoring is absolutely necessary.