Choroidal Thickness in Acute Non-arteritic Anterior Ischemic Optic Neuropathy

Subfoveal choroidal thickness increases after excimer laser-assisted penetrating keratoplasty but not after excimer laser-assisted deep anterior lamellar keratoplasty

To evaluate the impact of excimer laser-assisted deep anterior lamellar keratoplasty (Exc-DALK) and excimer laser-assisted penetrating keratoplasty (Exc-PKP) on subfoveal choroidal thickness (SFCT) in eyes with advanced keratoconus. A retrospective comparative clinical study, which compares the outcomes of 24 eyes treated with Exc-DALK (G1) against matched group of 43 eyes treated with Exc-PKP (G2) at both 2 months (T1) and 2 years (T2) postoperatively. Main outcomes included best-corrected visual acuity (BCVA), central macular thickness (CMT), and SFCT. Preoperatively, there were no significant differences between both groups regarding BCVA, CMT or SFCT (p > 0.05). There were no significant differences between both groups regarding BCVA at both follow-ups (p > 0.05). There were no significant differences between both groups regarding CMT at both follow-ups (p > 0.05). SFCT was higher in G2 than G1 at both follow-ups (p < 0.01). Compared to preoperative SFCT, there were no significant changes in SFCT in G1 at both follow-ups (p > 0.05). In G2, SFCT increased significantly at T1 (p < 0.01) and did not differ significantly at T2 (p = 0.17). SFCT increased significantly after Exc-PKP but not after Exc-DALK, which might indicate that Exc-DALK affects the choroid less and thus could represent a less traumatic approach to ocular tissue than Exc-PKP.

Regional hemodynamics characteristics in patients with non-arteritic anterior ischemic optic neuropathy

BACKGROUND: Non-arteritic anterior ischemic optic neuropathy (NAION) takes the first place in the total amount of acute vascular optic neuropathy cases. There is no common understanding of pathogenetic mechanisms of disease. This is largely due to the absence of direct optic nerve head blood flow registration method in ophthalmology. AIM: The aim of this work is to evaluate ocular hemodynamics using different methods in patients with non-arteritic anterior ischemic optic neuropathy (NAION). MATERIALS AND METHODS: 73 patients were enrolled in the study. 46 patients (46 eyes) with NAION were included in the first group. Control group was composed of 27 patients (50 eyes) with systemic risk factors of NAION without any retinal and optic nerve diseases. Regional hemodynamics parameters were evaluated with ophthalmosphigmography, ophthalmoplethysmography, ophthalmoreography, OCT-angiography and EDI-OCT. RESULTS: Blood flow values in different parts of the choroid did not statistically differ between groups when using ophthalmosphigmography, ophthalmoplethysmography, ophthalmoreography methods. Radial peripapillary capillaries in optic nerve head area were evaluated, and statistically significant difference was found in all sectors. CONCLUSION: The main component of NAION pathogenesis is a decreasing perfusion pressure in paraoptic short posterior ciliary arteries. Blood flow in choroid does not play an important role in the disease pathogenesis.

A Potential Role of Acute Choroidal Expansion in Nonarteritic Anterior Ischemic Optic Neuropathy

Purpose

Nonarteritic anterior ischemic optic neuropathy (NAION) has been associated with a thickened choroid at the optic nerve head (ONH). Here, we use computational modeling to better understand how choroidal expansion and choroidal geometry influence tissue deformation within the ONH relative to intraocular pressure (IOP) and intracranial pressure (ICP) effects.

Methods

Using a model of the posterior eye that included the sclera, peripapillary sclera, annular ring, pia mater, dura mater, neural tissues, Bruch's membrane, choroid, and lamina cribrosa, we examined how varying material properties of ocular tissues influenced ONH deformations under physiological and supra-physiological, or “pathological,” conditions. We considered choroidal expansion (c. 35 µL of expansion), elevated IOP (30 mm Hg), and elevated ICP (20 mm Hg), and calculated peak strains in the ONH relative to a baseline condition representing an individual in the upright position.

Results

Supra-physiological choroidal expansion had the largest impact on strains in the prelaminar neural tissue. In addition, compared to a tapered choroid, a “blunt” choroid insertion at the ONH resulted in higher strains. Elevated IOP and ICP caused the highest strains within the lamina cribrosa and retrolaminar neural tissue, respectively.

Conclusions

Acute choroidal expansion caused large deformations of the ONH and these deformations were impacted by choroid geometry. These results are consistent with the concept that compartment syndrome due to the choroid geometry and/or expansion at the ONH contributes to NAION. Prolonged deformations due to supra-physiological loading may induce a mechanobiological response or ischemia, highlighting the potential impact of choroidal expansion on biomechanical strains in the ONH.

Peripapillary Choroidal Vascularity and Visual Correlates in Non-Arteritic Anterior Ischemic Optic Neuropathy Using Swept-Source Optical Coherence Tomography

Introduction

The peripapillary choroid shares a blood supply with and is directly apposed to the optic nerve, and therefore may contribute to the pathogenesis of non-arteritic anterior ischemic optic neuropathy (NAION). Prior studies evaluating peripapillary choroidal thickness (PCT) or choroidal vascularity index (CVI; the ratio of the perfused area to total choroid area) have produced mixed results. None investigated the relationship between PCT and CVI or demonstrated functional correlates. We hypothesized that greater PCT and lower CVI would correlate with visual function in patients presenting with NAION.

Methods

Seventeen eyes with NAION (9 acute, 8 non-acute) and 6 unaffected "fellow" eyes in 13 patients, and 18 eyes in 18 age-matched control subjects were imaged using swept-source optical coherence tomography (SS-OCT) prospectively between 2017-2018. Mean PCT and CVI measurements were compared across groups and with respect to corresponding automated perimetric performance at the same visit.

Results

Analysis of variance showed significantly greater PCT (NAION: 278 ± 65 μm, Fellow: 221 ± 50 μm, Control: 158 ± 27 μm, p<0.001) and lower CVI (NAION: 0.35 ± 0.03, Fellow: 0.35 ± 0.04, Control: 0.38 ± 0.02, p<0.005) in patients with NAION compared to control subjects. Bonferroni-corrected pairwise comparisons showed greater PCT and lower CVI in NAION-affected eyes compared to control eyes (p values<0.008), and no significant differences in PCT or CVI between NAION and fellow eyes (p values>0.06). PCT was negatively correlated with CVI among unaffected fellow eyes (r=-0.8, p<0.05), but not among acute NAION eyes (r=-0.1, p>0.7), non-acute NAION eyes (r=0.1, p>0.7), or controls (r=-0.3, p>0.2). Nasal CVI was positively correlated with mean deviation scores in non-acute NAION (r=0.8, p<0.02), but not among fellow unaffected eyes (r=0.8, p>0.05) or acutely affected NAION eyes (r=-0.3, p>0.4). Mean and temporal PCT correlated with pattern standard deviation scores among unaffected fellow eyes (r=0.8, p<0.04; r=0.9, p<0.03), but not among acute NAION eyes (r=-0.2, p>0.5; r=-0.1, p>0.7) or non-acute NAION eyes (r=0.1, p>0.7; r=0.05, p>0.9).

Conclusion

NAION and unaffected fellow eyes demonstrate increased choroidal thicknesses and reduced vascular density. Perimetric performance is directly associated with vascular density among non-acutely affected eyes with NAION. Ongoing work will provide further insights into these structure-function relationships with pathogenic and pathophysiologic relevance.

Alterations in retinal and choroidal thickness following nonarteritic anterior ischemic optic neuropathy

PURPOSE

To show alterations of retinal arteriolar caliber (RAC), retinal venular caliber (RVC), retinal nerve fiber layer thickness (RNFLT), peripapillary choroidal thickness (ppCT), and central macular thickness (CMT) in acute and chronic phases of nonarteritic anterior ischemic optic neuropathy (NAION).

METHODS

Forty-one eyes of 41 patients with NAION were included in this retrospective study. RAC, RVC, RNFLT, ppCT, and CMT measurements were performed via spectral-domain optical coherence tomography in the acute and chronic phases of NAION.

RESULTS

RVC, RNFLT, ppCT, and CMT were significantly thinner in the chronic phase compared to the acute phase (p < 0.001), whereas RAC remained similar throughout the visits (p = 0.26). The visual acuity difference between the acute and chronic phases was not correlated with the changes of RAC, RVC, RNFLT, ppCT, or CMT.

CONCLUSIONS

RVC, RNFLT, ppCT, and CMT decreases in the chronic phase when compared to the acute phase of NAION, whereas RAC does not change significantly.