Relationship between lamina cribrosa displacement and trans-laminar pressure difference in papilledema

Optical Coherence Tomography Neuro-Toolbox for the Diagnosis and Management of Papilledema, Optic Disc Edema, and Pseudopapilledema

BACKGROUND

Distinguishing optic disc edema from pseudopapilledema is a common, sometimes challenging clinical problem. Advances in spectral-domain optical coherence tomography (SD-OCT) of the optic nerve head (ONH) has proven to be a cost effective, noninvasive, outpatient procedure that may help. At its core are tools that quantify the thickness of the retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL). The SD-OCT also provides a set of tools that may be qualitatively interpreted in the same way that we read an MRI. They include the transverse axial, en face, and circular tomogram. Our goal is to describe a practical office-based set of tools using SD-OCT in the diagnosis and monitoring of papilledema, optic disc edema, and pseudopapilledema.

EVIDENCE ACQUISITION

Searches on PubMed were performed using combinations of the following key words: OCT, papilledema, pseudopapilledema, optic disc drusen, retinal folds (RF), and choroidal folds (CF).

RESULTS

The principal elements of SD-OCT analysis of the ONH are the RNFL and GC-IPL thickness; however, these metrics have limitations when swelling is severe. Qualitative interpretation of the transverse axial SD-OCT aids in assessing peripapillary shape that may help distinguish papilledema from pseudopapilledema, evaluate atypical optic neuropathies, diagnose shunt failures, and identify outer RF and CF. There is a consensus that the SD-OCT is the most sensitive way of identifying buried optic disc drusen. En face SD-OCT is especially effective at detecting peripapillary wrinkles and outer retinal creases, both of which are common and distinctive signs of optic disc edema that rule out pseudopapilledema. Mechanically stressing the ONH in the adducted eye position, in patients with papilledema, may expose folds and peripapillary deformations that may not be evident in primary position. We also discuss how to optimize the acquisition and registration of SD-OCT images.

CONCLUSIONS

The SD-OCT is not a substitute for a complete history and a careful examination. It is, however, a convenient ancillary test that aids in the diagnosis and management of papilledema, optic disc edema, and pseudopapilledema. It is particularly helpful in monitoring changes over the course of time and distinguishing low-grade papilledema from buried drusen. The application of the SD-OCT toolbox depends on optimizing the acquisition of images, understanding its limitations, recognizing common artifacts, and accurately interpreting images in the context of both history and clinical findings.

Optical Coherence Tomography Imaging of the Lamina Cribrosa: Structural Biomarkers in Nonglaucomatous Diseases

The lamina cribrosa (LC) is an active structure that responds to the strain by changing its morphology. Abnormal changes in LC morphology are usually associated with, and indicative of, certain pathologies such as glaucoma, intraocular hypertension, and myopia. Recent developments in optical coherence tomography (OCT) have enabled detailed in vivo studies about the architectural characteristics of the LC. Structural characteristics of the LC have been widely explored in glaucoma management. However, information about which LC biomarkers could be useful for the diagnosis, and follow-up, of other diseases besides glaucoma is scarce. Hence, this literature review aims to summarize the role of the LC in nonophthalmic and ophthalmic diseases other than glaucoma. PubMed was used to perform a systematic review on the LC features that can be extracted from OCT images. All imaging features are presented and discussed in terms of their importance and applicability in clinical practice. A total of 56 studies were included in this review. Overall, LC depth (LCD) and thickness (LCT) have been the most studied features, appearing in 75% and 45% of the included studies, respectively. These biomarkers were followed by the prelaminar tissue thickness (21%), LC curvature index (5.4%), LC global shape index (3.6%), LC defects (3.6%), and LC strains/deformations (1.8%). Overall, the disease groups showed a thinner LC (smaller LCT) and a deeper ONH cup (larger LCD), with some exceptions. A large variability between approaches used to compute LC biomarkers has been observed, highlighting the importance of having automated and standardized methodologies in LC analysis. Moreover, further studies are needed to identify the pathologies where LC features have a diagnostic and/or prognostic value.

Morphological assessment of lamina cribrosa in idiopathic intracranial hypertension

Purpose:

Technological development of optic coherence tomography has enabled a detailed assessment of the optic nerve and deeper structures and in vivo measurements. The aim of this study was to compare the lamina cribrosa morphology of the optic nerve in idiopathic intracranial hypertension (IIH) and healthy individuals.

Methods:

The lamina cribrosa morphology of optic nerve in 15 eyes with IIH and 17 eyes of healthy individuals were compared. Four parameters such as Bruch membrane opening (BMO), lamina cribrosa thickness (LCT), prelaminar tissue thickness (PTT), and anterior lamina cribrosa surface depth (ALCSD) were retrospectively evaluated.

Results:

By enhanced depth imaging-optic coherence tomography (EDI-OCT), PTT and BMO were found to be significantly greater (574,35 ± 169,20 μm and 1787,40 ± 140,87 μm, respectively) in IIH patients than healthy individuals (187,18 ± 132,15 μm and 1632,65 ± 162,58 μm, respectively), whereas ALSCD was found to be significantly less in IIH patients (234,49 ± 49,31 μm) than healthy individuals (425,65 ± 65,23 μm). There was not a statistically significant difference regarding LCT between the IIH patients (238,59 ± 17,31 μm) and healthy individuals (244,96 ± 15,32 μm).

Conclusion:

Increased intracranial pressure causes morphological changes in lamina cribrosa. Assessment of lamina cribrosa with EDI-OCT is important for diagnosis and follow-up of patients with IIH. EDI-OCT is objective, reproducible, and cost-effective assistive imaging tool in IIH patients.

Intracranial and Intraocular Pressure at the Lamina Cribrosa: Gradient Effects

PURPOSE OF REVIEW

A pressure difference between the intraocular and intracranial compartments at the site of the lamina cribrosa has been hypothesized to have a pathophysiological role in several optic nerve head diseases. This paper reviews the current literature on the translamina cribrosa pressure difference (TLCPD), the associated pressure gradient, and its potential pathophysiological role, as well as the methodology to assess TLCPD.

RECENT FINDINGS

For normal-tension glaucoma (NTG), initial studies indicated low intracranial pressure (ICP) while recent findings indicate that a reduced ICP is not mandatory. Data from studies on the elevated TLCPD as a pathophysiological factor of NTG are equivocal. From the identification of potential postural effects on the cerebrospinal fluid (CSF) communication between the intracranial and retrolaminar space, we hypothesize that the missing link could be a dysfunction of an occlusion mechanism of the optic nerve sheath around the optic nerve. In upright posture, this could cause an elevated TLCPD even with normal ICP and we suggest that this should be investigated as a pathophysiological component in NTG patients.

Simultaneous evaluation of the lamina cribosa position and choroidal thickness changes following deep sclerectomy

PURPOSE:

To assess the changes in peripapillary and macular choroidal thickness, and in the lamina cribrosa position following deep sclerectomy.

METHODS:

Prospective study, including 39 eyes with open-angle glaucoma following deep sclerectomy. Choroidal thickness was automatically measured using swept-source optical coherence tomography at four peripapillary locations (superior, temporal, inferior, and nasal) and at the macular area in nine fields plotted with Early Treatment Diabetic Retinopathy Study grid. Optic nerve head was evaluated by Spectralis optical coherence tomography with enhanced depth imaging technology. All measurements were performed preoperatively and at 1 week and 2 months after surgery.

RESULTS:

The mean intraocular pressure significantly decreased 1 week and 2 months after surgery ( p < 0.001). A significant peripapillary choroidal thickening was observed at all locations 1 week postoperatively ( p ≤ 0.002) and in the temporal quadrant 2 months after surgery ( p = 0.027). There was a significant thickening in all macular choroidal thickness measurements at 1 week ( p < 0.001) and 2 months ( p < 0.05), except at subfoveal and inner nasal locations. The mean peripapillary and macular choroid thickness was 22.8% and 19.7% at 1 week and 6.2% and 7.8% at 2 months, respectively. A significant forward lamina cribrosa displacement occurred at every postoperative stage ( p < 0.001). Multivariate analysis showed a significant correlation between the magnitude of intraocular pressure reduction and the anterior lamina cribrosa movement (0.623, p = 0.000) and a negative correlation between the intraocular pressure change and the mean peripapillary and macular choroidal thickening (-0.527, p = 0.002; -0.568, p = 0.002, respectively).

CONCLUSION:

There was a significant reversal lamina cribrosa displacement measured from Bruch's membrane opening reference despite a significant peripapillary choroidal thickening following deep sclerectomy. Both findings were significantly correlated with the change in intraocular pressure.