Luis E. Vazquez

Optical Coherence Tomography Angiography Macular and Peripapillary Vessel Perfusion Density in Healthy Subjects, Glaucoma Suspects, and Glaucoma Patients

Purpose To evaluate macular and peripapillary vessel perfusion density (VD) in glaucoma suspects (GS) and glaucoma patients; to correlate ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) thicknesses with macular and peripapillary VD; and to evaluate the diagnostic accuracy of the structural and vascular parameters. Methods A consecutive series of GS, glaucoma patients, and healthy subjects was prospectively recruited from July 1, 2016, to January 31, 2017. All subjects underwent standard automated perimetry, spectral-domain optical coherence tomography (OCT), and 6 × 6-mm optical coherence tomography angiography (OCT-A) centered on the fovea and optic nerve. Results Forty controls, 40 GS, and 40 glaucoma patients were enrolled. Peripapillary RNFL, GCIPL, and macular RNFL thicknesses significantly decreased in the glaucoma group compared to controls and GS (P < 0.01). Peripapillary VD in average and in the superior and inferior quadrants decreased in the glaucoma group (P ≤ 0.001); conversely, macular VD was not statistically different across groups (P > 0.05). At the peripapillary area, a correlation between RNFL thickness and VD was found; conversely, no statistically significant correlation was found between GCIPL thicknesses and macular VD (all P > 0.05) in all groups. Peripapillary RNFL and GCIPL showed higher diagnostic capacity compared to peripapillary and macular VDs. Conclusions Structural damage is evident both in the peripapillary and in macular areas. Vascular damage seems to be less prominent, as it was seen only for the glaucoma group and at the radial peripapillary plexus. Diagnostic abilities are excellent for structural variables, less so but still good for peripapillary VD, and poor for macular VD.

Genomic and Proteomic Pathophysiology of Pseudoexfoliation Glaucoma

PEX stems from a pathologic elastotic process involving the cross-linking gene lysyl oxidase-like-1 (LOXL1), and is associated with abnormal formation of elastic extracellular matrix. We previously described a protein sink model to explain PEX material deposition on the lens capsule and other intraocular surfaces. Recent research findings not only provide evidence to support this hypothesis, but also further our understanding of the fundamental disease process. A key aspect of the pathogenic process is the compromise of blood-aqueous barrier integrity in PEXG. Decreased level of LOXL1 is associated with decreased elastin incorporation into elastic tissues, including the elastic lamina of blood vessels. This results in unincorporated elastin that is released as soluble elastin, and leakage of serum proteins, inflammatory cytokines, and extracellular matrix components into aqueous humor. This ultimately leads to aggregation and precipitation of large protein complexes, or PEX material, throughout intraocular surfaces as described in the protein sink model. The pathologic PEX process also affects the biomechanical properties of elastic tissues, such as the trabecular meshwork, lens zonules, and lamina cribrosa. This may be part of the primary pathologic process with intrinsically altered extracellular matrix proteins. This fundamental change in the structural composition of these tissues may alter their rigidity, elasticity, and other biomechanical properties. This likely contributes to increased trabecular meshwork outflow resistance and high intraocular pressure, and mechanical injury to retinal ganglion cell axons at the lamina cribrosa, which are conducive to glaucoma. These pathophysiologic processes combined may underlie some of the clinical hallmarks observed in PEXG.

Head-down Posture in Glaucoma Suspects Induces Changes in IOP, Systemic Pressure, and PERG That Predict Future Loss of Optic Nerve Tissue

Purpose: To obtain pilot data on posture-induced changes of intraocular pressure (IOP), systemic pressure, and pattern electroretinogram (PERG) predictive of future optic nerve tissue loss glaucoma suspects (GSs). Methods: Mean peripapillary retinal fiber layer thickness (RNFLT) was measured with optical coherence tomography 2 times/year in 28 GS aged 58±8.9 years over 5.0±0.73 years. All patients had a baseline PERG, IOP, and brachial blood pressure measurements in the seated and −10 degrees head-down-body-tilt (HDT) position. Outcome measures were seated/HDT PERG amplitude and phase, IOP, mean arterial blood pressure, and estimated ocular perfusion pressure. An additional group of 11 similarly aged controls aged 56.9±13 years was tested for comparison. Results: Although all GS had initial RNFLT in the normal range, 9/28 of them developed significant (P<0.05) loss of mean RNFLT [thinners (T)] over the follow-up period as opposed to 19/28 who did not [nonthinners (NT)]. Significant (P<0.05) differences between similarly aged controls, NT, and T were found in PERG amplitude, PERG phase, mean arterial blood pressure, IOP, and ocular perfusion pressure. A nominal logistic regression using baseline PERG and hemodynamic variables was able to distinguish T from NT with an area under receiving operator characteristic of 0.89 (SE, 0.07). Conclusions: Baseline PERG, IOP, and systemic blood pressure, together with their changes upon HDT, may have predictive value for future loss of optic nerve tissue in GS. This study supports the rationale for a full-scale clinical trial to identify patients at high risk of development of glaucoma.

The Modified Schocket Procedure

Glaucoma is not infrequently encountered after retinal detachment surgery. Surgical management of glaucoma in eyes with preexisting scleral buckles can be challenging. Trabeculectomy has a high failure rate because poor conjunctival health limits bleb survival, and glaucoma drainage devices have large-sized plates and their implantation is often difficult if a scleral buckle is present. The modification to the original Schocket procedure described by Sidoti and colleagues in which a silicone tube is inserted into the capsule of a preexisting scleral buckle is a good surgical option. This anterior chamber tube shunt to an encircling band (ACTSEB) is a safe and effective option to control intraocular pressure (IOP) in these cases. Reported success in lowering IOP ranges between 80 and 90 % in published retrospective case series. Reported complications include immediate postoperative hypotony, serous choroidal detachments, conjunctival wound leak, hyphema, and tube obstruction. The use of current glaucoma drainage devices in eyes with preexisting scleral buckles has also been described with comparable outcome and complication rates. The modified Schocket procedure is particularly useful when significant conjunctival and subconjunctival scarring is present in eyes with preexisting scleral buckles.