[Role of the lamina cribrosa in the pathogenesis of glaucoma. A review of the literature]. / Rôle de la lame criblée dans la pathogenèse du glaucome. Une revue de la littérature.

Located within the scleral canal, the lamina cribrosa is a sieve-like structure separating the intraocular and retrobulbar portions of the optic nerve. Identified as the main site of axonal damage in glaucomatous optic neuropathy, the study of the lamina cribrosa has been of great interest for many years. Numerous studies have explored the histological and morphological characteristics of the laminar region in healthy subjects as well as glaucoma patients. More recently, the development of adaptive optics systems and new generations of OCT has allowed great progress in the understanding of the pathogenesis of glaucoma and has opened new perspectives for the improvement of diagnostic procedures.

Cystic maculopathy of the inner nuclear layer in glaucoma patients.

PURPOSE: The study aimed to detect and describe glaucoma-related pseudocystic abnormalities at the internal nuclear layer (INL) of the macula using OCT, in relation with visual field defects and other clinical data. PATIENTS AND METHODS: Primary open-angle glaucoma patients presenting for a follow-up visit were consecutively included over 5 months and underwent clinical examination, OCT imaging, and central 10-2 visual field testing. OCT measures included the thickness of the peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC), together with an analysis of B-Scans and en-face images. All data provided by OCT were analyzed and compared with the visual field testing. RESULTS: Fourteen patients out of 216 showed pseudocysts in the INL of the macula. These cysts were hyporeflective, fusiform, and of variable size (15 to 25µm) and were always associated with a thinning of both the RNFL and GCC. En-face OCT showed evidence of a distribution of cysts in the macular region, based on the appearance of numerous, dense hyporeflective pits whose localization matched precisely with the vision loss as assessed by central 10-2 visual field testing. No other correlations were found. DISCUSSION: Pseudocysts of the internal nuclear layer of the macular region are found in some cases of chronic glaucoma. Their presence is always associated with a scotoma in the visual field and appear to constitute a marker for glaucoma progression. Glaucoma-related central pseudocysts could result from Müller cell changes, excitotoxicity, and/or trans-synaptic retrograde degeneration. The presence of pseudocysts could be a marker of a particular subpopulation whose features remain to be determined.

[New diagnosis approaches: iridocorneal angle in optical coherence tomography]. / L'angle irido-cornéen en tomographie de coherence optique.

Gonioscopy remains a standard technique to evaluate anterior segment and iridocorneal angle. However, new imaging techniques, particularly high resolution optical coherence tomography (OCT), permit to optimally visualize the anterior segment. Use of OCT in glaucoma diagnosis and follow-up will increase with technical progress and new high speed ultrahigh-resolution OCT.

[Application of anterior segment OCT to the study of glaucoma]. / Application de l'OCT de segment antérieur dans l'étude des glaucomes.

Anterior segment OCT is a noninvasive and simple imaging technique providing high-resolution images of the anterior segment of the eye. Glaucoma is a large domain of application for anterior segment OCT. In addition to the morphologic and morphometric analysis of anterior segment structures and of the iridocorneal angle in particular, numerous new applications such as the follow-up of filtering surgery have been developed.

[Failure of photocoagulation therapy for diabetic macular edema]. / Echec de la photocoagulation au cours des oedèmes maculaires diabétiques sévères.

PURPOSE: To analyse clinical and tomographic features of diabetic macular edemas (DME) unresponsive to laser photocoagulation. METHODS: Retrospective study of 43 consecutive eyes presenting with severe DME defined by a macular thickening 450 microm or more, involving the fovea, and associated with either cystoid spaces and/or hard exudates threatening the center of the macula. All 43 eyes underwent subthreshold grid laser therapy (a mean of 2.3 sessions). Mean follow-up was 21 months. RESULTS: Photocoagulation was beneficial in 39% of the eyes (n=17) and failed in 60% (n=26). Comparing these two groups, we found that some tomographic and clinical signs were strikingly more frequent in the unresponsive eyes than in the responsive ones. OCT findings reported foveal thickening greater than 700 microm (38%), subclinical serous foveal detachment (65%), subclinical vitreomacular interface abnormalities (19%) and as clinical signs, 44% of the unresponsive eyes exhibited rapid progression of retinal ischemia preceding ME constitution. CONCLUSION: Long-standing diffuse DME carries an unfavorable prognosis. In cases of unresponsive DME exhibiting these tomographic and clinical signs, alternative therapies such as intravitreal injections of steroids and/or vitrectomy with posterior hyaloid removal should be considered, instead of iatrogenic and useless iterative grid laser treatments.

[OCT3 exploration of anterior segment]. / Exploration du segment antérieur par OCT3.

PURPOSE: Posterior pole imaging with OCT3 provides macular scans with a very high resolution. Use of OCT1 has already been described for anterior segment imaging. This work presents the advantages of OCT3 in anterior segment imaging compared to UBM (50 MHz) and 20-MHz ultrasound imaging with long focal distance (patent pending PCT/FR98/02788). MATERIAL: and methods: We used an OCT3 unit dedicated to the posterior pole. By defocusing the laser beam we obtained high-resolution scans of the cornea, angle, lens and IOLs. Fifty-seven eyes (35 patients) were imaged by OCT3 and high-resolution ultrasound in cases of corneal dystrophy, corneal transplant, LASIK, narrow angle, iris bowing, etc. RESULTS: In all cases OCT3 provided high-resolution information with a limit of penetration at the posterior part of the iris. This limitation was not observed with ultrasound imaging. Nevertheless, OCT3 is a useful tool for corneal imaging in cases of opacities limiting biomicroscope imaging. OCT3 corneal scans at high resolution make it possible to identify the corneal interface in lamellar transplants or LASIK. With a narrow angle, a dynamic test of angle closure can be done. With iris bowing, OCT3 can differentiate iris cysts and iris tumors. Anterior chamber IOLs can be imaged with their relationships to anterior segment structures. CONCLUSION: OCT3 provides non-contact anterior segment imaging with high resolution but with a limit of penetration given by posterior part of the iris.