Ocular pulse amplitude in different types of glaucoma using dynamic contour tonometry: Diagnosis and follow-up of glaucoma

[Examination of patients with glaucoma during the COVID-19 pandemic]

PURPOSE

To evaluate the efficacy of the optimal examination technique for patients with glaucoma during the COVID-19 pandemic that includes one of the safest methods of tonometry [transpalpebral tonometry (TPT), contour dynamic tonometry (CDT) and Icare rebound tonometry (RBT)] in combination with spectral domain optical coherence tomography (SD-OCT) and optical coherence tomography angiography (OCTA).

MATERIAL AND METHODS

The study included 65 patients with primary open-angle glaucoma (POAG) who sought medical aid at the Ophthalmological Center of FMBA during the COVID-19 pandemic; they were examined using three tonometry methods: RBT, TPT and CDT. All patients underwent central corneal thickness measurement, perimetry, OCT and OCTA with assessment of vessel density (VD) of the superficial plexus in the macula (whole image macula) and peripapillary retina (PPR).

RESULTS

High correlation was found between the results obtained with RBT, TPT and CDT. None of the methods showed a correlation between IOP and corneal thickness. The correlations between IOP and OCTA parameters were obtained: IOP_TPT and VD_PPR in the inferior temporal sector (r= -0.386, p=0.027), IOP_RBT and VD whole image macula (r= -0.69, p=0.019), and in the macula inferior hemisphere (r= -0.75, p=0.008), as well as between the ocular pulse amplitude (OPA) and VD in the macular inferior hemisphere (r=0.380, p=0.039). The OCTA parameters had a moderate, but significant correlation with the perimetric indices.

CONCLUSIONS

Tonometry methods (TPB, CDT and RBT) exhibit high correlation with each other and no correlation with corneal thickness. IOP parameters measured by different methods, especially using the Icare tonometer, correlate with OCTA parameters, and the latter - with perimetric indices. The combination of these tonometry methods with SD-OCT and OCTA is optimal for examining patients during the pandemic.

Macular vessel density and foveal avascular zone parameters in patients after acute primary angle closure determined by OCT angiography

This study analyzed the optical coherence tomography angiography (OCTA) macular parameters in primary angle-closure glaucoma (PACG) patients after acute primary angle closure (APAC) episodes. Thirty-three patients with 33 APAC eyes and 33 primary angle closure suspect (PACS) eyes and 33 age-matched normal subjects (controls) were enrolled. Macular vessel density (VD) in central, inner, outer and full regions and foveal avascular zone (FAZ) parameters (area, perimeter and circularity index) were compared between APAC, PACS, and control eyes. For resolved APAC eyes, the VD in each macular region was significantly lower than that in control eyes, with less central and inner macular VD than PACS eyes. The central macular VD was significantly lower in PACS eyes than in controls. There was no difference in FAZ area and perimeter between APAC, PACS, and control eyes. FAZ circularity was highest in control eyes, followed by PACS eyes, and lowest in APAC eyes. The AUC, sensitivity and specificity of FAZ circularity were 0.944, 93.9% and 84.8%, respectively, in APAC eyes and 0.881, 84.8% and 81.8%, respectively, in PACS eyes. Therefore, FAZ circularity had the best discrimination capability for detecting both APAC and PACS eyes. Macular assessment with OCTA could provide an accurate early-stage diagnostic tool for PACG.

Effect of Changing Heart Rate on the Ocular Pulse and Dynamic Biomechanical Behavior of the Optic Nerve Head

Purpose

To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model.

Methods

In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates.

Results

With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate.

Conclusions

In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology.