Relationships among Ocular Blood Flow Shown by Laser Speckle Flowgraphy, Retinal Arteriosclerotic Change, and Chorioretinal Circulation Time Obtained by Fluorescein Angiography

Association between the arm-to-choroidal circulation time and clinical profile in patients with polypoidal choroidal vasculopathy

PURPOSE

To investigate the association between the arm-to-choroidal circulation time (ACT) on indocyanine green angiography (IA) and clinical profile in patients with polypoidal choroidal vasculopathy (PCV).

STUDY DESIGN

Single-center retrospective study.

METHODS

We included 38 eyes of 38 patients with PCV diagnosed using multimodal imaging and did not undergo previous treatment. All patients were treated with monthly aflibercept injections for 3 months and treat-and-extend regimens for the subsequent 12 months. Posterior vortex vein ACT was assessed on the first visit using Heidelberg IA. The patients were divided into two groups: ACT ≥20 s (L group; eight eyes) and ACT <20 s (S group; 30 eyes). The clinical profiles before and after treatment were analyzed to assess associations with ACT.

RESULTS

The mean ACT was 16.39±3.3 s (L group: 21.25±1.49 s, women:men=2:6, mean age: 77.3±6.5 years; S group: 15.10±2.17 s, women:men=7:23, mean age: 75.5±6.9 years). No significant difference was observed in the mean subfoveal choroidal thickness between the L and the S groups (176±75 μm vs. 230±79 μm, P=0.10). However, there were significant differences between the L and S groups in retinal fluid accumulation and hemorrhage recurrence (eight/eight eyes, 100% vs. 13/30 eyes, 43%, P<0.001), mean aflibercept injections (8.8±1.6 vs. 7.0±1.6, P<0.01) during the 12-month period, and the number of polypoidal lesions (1.8±0.7 vs. 1.3±0.5, P<0.05).

CONCLUSION

Patients with PCV and ACT >20 s are more likely to experience exudative change recurrence in the retina during treatment because they have more polypoidal lesions.

Retinal circulation time/arm-to-retina time ratio in the fluorescein angiography to evaluate retina-specific hemodynamics

To evaluate dynamic circulatory flow in the retinal or choroidal circulatory disease, we retrospectively reviewed medical charts of 128 eyes of 128 patients who underwent video recorded fluorescein angiography (FA), at Department of Ophthalmology, St Luke's International Hospital, between April and September 2020. Mean age was 64.2 ± 14.0 (range 37-93) years, and 87 (67.9%) patients were men. Mean arm-to-retina (AR) time was 16.2 ± 4.1 s, and mean retinal circulation (RC) time was 10.9 ± 3.3 s. Mean RC time/AR time (RC/AR) ratio was 0.69 ± 0.22. AR time was correlated with age, whereas RC time was not. RC time was positively correlated with AR time (R = 0.360, P = 0.017). Moreover, mean RC time was significantly longer, and RC/AR ratio was greater, in the retinal-disease group after adjusting for age and sex. Patients who had an RC/AR ratio ≥ 0.8 more frequently presented with retinal diseases. RC time and RC/AR ratio were negatively correlated with systolic blood pressure only in the retinal-disease group. Given that AR time reflects systemic hemodynamics, RC time, which reflects local circulatory fluency, was influenced by the systemic circulatory condition. Moreover, RC/AR ratio revealed that circulatory changes peculiar to the retina may also be involved in retinal-disease pathogenesis. This study may help elucidate the mechanisms of retinal diseases and assist in diagnosis, although further studies are required.

Arm-to-retina time predicts visual outcome of anti-vascular endothelial growth factor treatment for macular edema due to central retinal vein occlusion

To explore the factors associated with best-corrected visual acuity (BCVA) after anti-vascular endothelial growth factor (anti-VEGF) treatment for macular edema secondary to central retinal vein occlusion (CRVO). We retrospectively reviewed the medical charts of 22 eyes of 22 treatment-naïve patients with CRVO diagnosed between September 2014 and December 2020. They received anti-VEGF treatment and follow-up for > 12 months. Mean patient age was 64.3 years; 13 (59.1%) were men. Eyes with baseline arm-to-retina (AR) time ≥ 16 s had better BCVA at 12 months (adjusted for baseline BCVA and age; B, − 0.658; 95% confidence interval − 1.058 to − 0.257; P = 0.003), greater mean BCVA change (P = 0.006), lower frequency of residual macular edema at 12 months (P = 0.026) and recurrent and/or unresolved macular edema during 12 months (P = 0.046), and higher frequency of reduction in central retinal thickness ≥ 150 μm at 1 and 12 months (both P = 0.046). Delayed AR time was associated with a better visual outcome and macular edema improvement in CRVO after anti-VEGF treatment regardless of initial BCVA and age. Our results may help understand the pathogenesis and predict the visual prognosis of patients before anti-VEGF therapy initiation.

Relative Retinal Blood Flow: A Novel and Informative Measure of Unilateral Retinal Vein Occlusion Severity

Purpose

This study quantifies retinal vascular blood flow affected by unilateral central or branch retinal vein occlusion (CRVO or BRVO). We created a new, unitless metric for the severity of these diseases—relative blood flow (RBF)—and contextualized it with subject demographics, ocular presentation, and systemic conditions. Finally, we explored its efficacy as a predictor of future outcomes.

Methods

Data were collected from 20 control subjects and 32 clinically diagnosed CRVO (n = 15) or BRVO (n = 17) patients. We used laser speckle flowgraphy to quantify blood flow as mean blur rate and present RBF as the ratio between the blood flow in a subject's diseased and undiseased eyes. Because of our demonstration that blood flow has high intrapatient (between eyes and over time) but low interpatient correlation in eyes of healthy subjects, any differences between eyes can be attributed to the disease. These data were correlated with subject demographics and disease characteristics.

Results

In CRVO and BRVO eyes, average blood flow decreased by 26% and 7%, respectively. In CRVO, occlusion duration, central macular thickness, intraocular pressure, diabetes, previous laser and injection treatments, and injection within three months after measurement were significantly associated with RBF. In BRVO, no significant associations with RBF were found.

Conclusions

Blood flow in CRVO and BRVO was reduced compared to the unaffected fellow eye in most patients. RBF was useful in determining the severity of RVOs and predicting future treatment needs.

Translational Relevance

RBF is a promising new and informative metric for quantifying the severity of unilateral RVOs.

Hallucal thenar index: A new index to detect peripheral arterial disease using laser speckle flowgraphy

OBJECTIVES

Laser speckle flowgraphy is a technology using reflected scattered light for visualization of blood distribution, which can be used to measure relative velocity of blood flow easily without contact with the skin within a short time. It was hypothesized that laser speckle flowgraphy may be able to identify foot ischemia. This study was performed to determine whether laser speckle flowgraphy could distinguish between subjects with and without peripheral arterial disease.

MATERIALS AND METHODS

All subjects were classified based on clinical observations using the Rutherford classification: non-peripheral arterial disease, class 0; peripheral arterial disease group, class 2-5. Rutherford class 6 was one of the exclusion criteria. Laser speckle flowgraphy measured the beat strength of skin perfusion as an indicator of average dynamic cutaneous blood flow change synchronized with the heartbeat. The beat strength of skin perfusion indicates the strength of the heartbeat on the skin, and the heartbeat strength calculator in laser speckle flowgraphy uses the blood flow data to perform a Fourier transform to convert the temporal changes in blood flow to a power spectrum. A total of 33 subjects with peripheral arterial disease and 40 subjects without peripheral arterial disease at a single center were prospectively examined. Laser speckle flowgraphy was used to measure hallucal and thenar cutaneous blood flow, and the measurements were repeated three times. The hallucal and thenar index was defined as the ratio of beat strength of skin perfusion value on hallux/beat strength of skin perfusion value on ipsilateral thenar eminence. The Mann-Whitney U-test was used to compare the median values of hallucal and thenar index and ankle brachial index between the two groups. A receiver operating characteristic curve for hallucal and thenar index of beat strength of skin perfusion was plotted, and a cutoff point was set. The correlation between hallucal and thenar index of beat strength of skin perfusion and ankle brachial index was explored in all subjects, the hemodialysis group, and the non-hemodialysis (non-hemodialysis) group.

RESULTS

The median value of the hallucal and thenar index of beat strength of skin perfusion was significantly different between subjects with and without peripheral arterial disease (0.27 vs. 0.87, respectively; P < 0.001). The median value of ankle brachial index was significantly different between subjects with and without peripheral arterial disease (0.8 vs. 1.1, respectively; P < 0.001). Based on the receiver operating characteristic of hallucal and thenar index, the cutoff was 0.4416 and the sensitivity, specificity, positive predictive value, and negative predictive value were 68.7%, 95%, 91.7%, and 77.6%, respectively. The correlation coefficients of all subjects, the hemodialysis group, and the non-hemodialysis group were 0.486, 0.102, and 0.743, respectively.

CONCLUSIONS

Laser speckle flowgraphy is a noninvasive, rapid, and widely applicable method. Laser speckle flowgraphy using hallucal and thenar index would be helpful to determine the differences between subjects with and without peripheral arterial disease. The correlation between hallucal and thenar index of beat strength of skin perfusion and ankle brachial index indicated that this index was especially useful in the non-hemodialysis group.

Ocular blood flow as a clinical observation: Value, limitations and data analysis

Alterations in ocular blood flow have been identified as important risk factors for the onset and progression of numerous diseases of the eye. In particular, several population-based and longitudinal-based studies have provided compelling evidence of hemodynamic biomarkers as independent risk factors for ocular disease throughout several different geographic regions. Despite this evidence, the relative contribution of blood flow to ocular physiology and pathology in synergy with other risk factors and comorbidities (e.g., age, gender, race, diabetes and hypertension) remains uncertain. There is currently no gold standard for assessing all relevant vascular beds in the eye, and the heterogeneous vascular biomarkers derived from multiple ocular imaging technologies are non-interchangeable and difficult to interpret as a whole. As a result of these disease complexities and imaging limitations, standard statistical methods often yield inconsistent results across studies and are unable to quantify or explain a patient's overall risk for ocular disease. Combining mathematical modeling with artificial intelligence holds great promise for advancing data analysis in ophthalmology and enabling individualized risk assessment from diverse, multi-input clinical and demographic biomarkers. Mechanism-driven mathematical modeling makes virtual laboratories available to investigate pathogenic mechanisms, advance diagnostic ability and improve disease management. Artificial intelligence provides a novel method for utilizing a vast amount of data from a wide range of patient types to diagnose and monitor ocular disease. This article reviews the state of the art and major unanswered questions related to ocular vascular anatomy and physiology, ocular imaging techniques, clinical findings in glaucoma and other eye diseases, and mechanistic modeling predictions, while laying a path for integrating clinical observations with mathematical models and artificial intelligence. Viable alternatives for integrated data analysis are proposed that aim to overcome the limitations of standard statistical approaches and enable individually tailored precision medicine in ophthalmology.