Purpose: Dry eye disease (DED) is a highly prevalent ocular condition with a significant burden on affected patients. Regardless of the underlying etiology, DED is associated with increased ocular surface inflammation. We investigated the safety and efficacy of a shortterm treatment with topical low dose hydrocortisone in patients with chronic DED and ocular surface inflammation. Methods: A total of 60 patients (mean age 51 ± 14 years) with chronic DED and conjunctival hyperemia greater than grade 2 on the Efron scale were included. Patients were randomized to receive either preservative-free hydrocortisone 0.335% (Softacort, Laboratories Thea, France) for 12 days four times daily followed by 2 days twice daily instillation (intense treatment group) or 8 days three times daily followed by 3 days twice daily treatment (standard treatment group). Ocular redness was assessed at baseline, day 14, and day 28. Measurement of intraocular pressure (IOP) and clinical tests to assess signs and symptoms of DED were performed. Results: Conjunctival hyperemia and Ocular Surface Disease Index (OSDI) significantly decreased in both treatment groups (p \ 0.001 each) after hydrocortisone treatment. A significant increase in tear film thickness was seen 4 weeks after treatment start (p = 0.03 and p = 0.04, respectively). IOP did not change in either of the two treatment groups (p = 0.45). Conclusion: Treatment with low dose hydrocortisone 0.335% reduced ocular inflammation and decreased OSDI score. No change in IOP was observed in either of the two treatment schedules. Because of its good safety profile, low dose The original version of this article was revised due to retrospective open access.

To investigate the repeatability and reproducibility of total retinal blood flow measurements using a custom-built dual-beam bidirectional Doppler optical coherence tomography (OCT) system in healthy subjects. Methods: Repeatability and reproducibility were analyzed in 10 and 34 healthy subjects, respectively. For repeatability, measurements were taken twice within 30 minutes, for reproducibility, twice within two to five weeks. Two analysis approaches were compared for calculation of absolute blood velocities: a previously published approach resulting in values for total arterial (Q A,abs) and total venous blood flow (Q V,abs) and a novel approach taking into account that there is a fixed relation between the phase shift in the two OCT channels (Q A,new, Q V,new). Repeatability and reproducibility were quantified using intraclass correlation coefficients (ICCs). Results: For Q A,abs and Q V,abs , ICC values between 0.78 and 0.84 were obtained. Q A,new and Q V,new values revealed better repeatability and reproducibility as compared to the convential appoach. Repeatability ICCs for Q A,new and Q V,new were between 0.91 and 0.93, and reproducibility ICCs were between 0.87 and 0.91 indicating excellent reproducibility. Good agreement was observed between total retinal blood flow values as measured from retinal arteries and retinal veins. Conclusions: Measurement of total retinal blood flow using dual-beam Doppler OCT shows excellent reproducibility, which can further be improved by using a novel algorithm for calculating blood velocities in retinal vessels. Translational Relevance: Our data indicate that dual-beam Doppler OCT can be used for longitudinal studies. Hence, quantitative retinal blood flow may be established as a biomarker for progression vascular eye diseases.

Citation: Puchner S, Schmidl D, Ginner L, et al. Changes in retinal blood flow in response to an experimental increase in IOP in healthy participants as assessed with Doppler optical coherence tomography. Invest Ophthalmol Vis Sci. 2020;61(2):33. https://doi.org/10.1167/iovs.61.2.33 PURPOSE.Blood flow autoregulation is an intrinsic mechanism of the healthy retinal vasculature to keep blood flow constant when ocular perfusion pressure (OPP) is changed. In the present study, we set out to investigate retinal blood flow in response to an experimental decrease in OPP in healthy participants using Doppler optical coherence tomography. METHODS.Fifteen healthy participants aged between 22 and 31 years (mean, 27 ± 3 years) were included in the present open study. IOP was increased stepwise via the suction cup method to induce a decrease in OPP. Retinal blood flow in arteries and veins was assessed using a custom-built Doppler optical coherence tomography system and pressure-flow relationships were calculated to assess autoregulation. RESULTS.Suction cup application induced a pronounced increase in IOP with a maximum value of 50.5 ± 8.0 mm Hg at the highest level of suction. Pressure-flow relationships revealed that blood flow was autoregulated until the OPP was decreased by approximately 21 mm Hg and started to decrease significantly when the OPP was reduced by 30 mm Hg. Retinal blood flow at the last suction period decreased at a maximum of -57.0 ± 22.3% and 65.2 ± 15.4% in retinal arteries and retinal veins, respectively. These changes in retinal blood flow were less pronounced than the decrease in OPP (-75.2 ± 19.2%), indicating retinal autoregulation. CONCLUSIONS.The results of the present study confirm that retinal blood flow is autoregulated in response to changes in the OPP. Doppler optical coherence tomography has the potential to become a clinical tool for the investigation of retinal blood flow autoregulation in the future, because of its ability to assess the blood velocities and diameter of the retinal vessels parallel and therefore also their blood flow in absolute values. (Clinicaltrials.gov number NCT03398616)

To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer.Methods: Twenty-four healthy volunteers participated in this randomized, double-masked, crossover study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusiondensity wascalculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of the gas mixtures. Retinal vessel calibres in major retinal vessels were measured using a dynamic vessel analyzer.Results: During 100% oxygen breathing, a significant decrease in DCP perfusion density from 41.7 AE 2.4 a.u to 35.6 AE 3.1 a.u. (p < 0.001) was observed, which was accompanied by a significant decrease in vessel diameters in majorretinal arteries and veins(p < 0.001 each). No significant change in perfusion density in the SVP occurred (p = 0.33). In contrast, during hypoxia, perfusion density in the SVP significantly increased from 34.4 AE 3.0a.u.to 37.1 AE 2.2 a.u. (p < 0.001), while it remained stable in the DCP (p = 0.25). A significant increase in retinal vessel diameters was found (p < 0.01). Systemic oxygen saturation correlated negatively with perfusion density in the SVP and the DCP and retinal vessel diameters (p < 0.005 each). Conclusion:Our results show that systemic hyperoxia induces a significant decrease in vessel density in the DCP, while hypoxia leads to increased vessel density limited to the SVP. These results indicate that the retinal circulation shows the ability to adapt its blood flow to metabolic changes with high local resolution dependent on the capillary plexus.

We present vessel density alterations in response to flicker stimulation using optical coherence tomography angiography and identified the superficial capillary plexus as the layer with the most pronounced effect. This points out the physiological importance of the microvasculature in mediating functional hyperemia and suggests a fine-tuned plexus-specific mechanism to meet cellular metabolic demands.