Static and Dynamic Pupillary Responses in Patients with Different Stages of Diabetic Retinopathy

Basics, benefits, and pitfalls of pupillometers assessing visual function

Numerous commercially and non-commercially available pupillometers are nowadays able to assess various biological functions in humans, by evaluating pupils' dynamics in response to specific stimuli. However, the use of pupillometers for ophthalmic afferent evaluations (i.e., photoreceptoral responses) in real-world settings is relatively limited. Recent scientific and technological advances, coupled with artificial intelligence methods have improved the performance of such devices to objectively detect, quantify, and classify functional disturbances of the retina and the optic nerve. This review aims to summarize the scientific principles, indications, outcomes, and current limitations of pupillometry used for evaluation of afferent pathways in ophthalmic clinical settings.

The Severity of Diabetic Retinopathy Corresponds with Corneal Nerve Alterations and Ocular Discomfort of the Patient

Diabetic retinopathy (DR) remains the leading cause of blindness in the working-age population. Its progression causes gradual damage to corneal nerves, resulting in decreased corneal sensitivity (CS) and disruption of anterior-eye-surface homeostasis, which is clinically manifested by increased ocular discomfort and dry eye disease (DED). This study included 52 DR patients and 52 sex- and age-matched controls. Ocular Surface Disease Index (OSDI) survey, tear film-related parameters, CS, and in vivo corneal confocal microscopy (IVCM) of the subbasal plexus were performed. Furthermore, all patients underwent tear sampling for neurotrophin and cytokine analysis. OSDI scores were greater in DR patients than in controls (p = 0.00020). No differences in the Schirmer test score, noninvasive tear film-break-up time (NIBUT), tear meniscus or interferometry values, bulbar redness, severity of blepharitis or meibomian gland loss were found. In the DR group, both the CS (p < 0.001), and the scotopic pupil diameter (p = 0.00008) decreased. IVCM revealed reduced corneal nerve parameters in DR patients. The stage of DR was positively correlated with the OSDI (Rs = +0.51, 95% CI: + 0.35-+0.64, p < 0.001) and negatively correlated with IVCM corneal nerve parameters and scotopic pupillometry (Rs = -0.26, 95% CI: -0.44--0.06, p = 0.0097). We found negative correlations between the OSDI and IVCM corneal innervation parameters. The DR group showed lower tear film-brain-derived neurotrophic factor (BDNF) levels (p = 0.0001) and no differences in nerve growth factor (NGF)-β, neurotrophin (NT)-4, vascular endothelial growth factor (VEGF), interleukin (IL)-1β, IL-4, IL-5, IL-6, or IL-12 concentrations. Tumor necrosis factor (TNF)-α, IL-2, IL-8, IL-10, granulocyte macrophage colony-stimulating factor (GM-CSF), and interferon (IFN)-γ levels were decreased among patients with DR. Corneal innervation defects have a direct impact on patients' subjective feelings. The evolution of DR appears to be associated with corneal nerve alterations, emphasizing the importance of IVCM.

Early diabetic eye damage: Comparing detection methods using diagnostic power

It is now clear that retinal neuropathy precedes classical microvascular retinopathy in diabetes. Therefore, tests that underpin useful new endpoints must provide high diagnostic power well before the onset of moderate diabetic retinopathy. Hence, we compare detection methods of early diabetic eye damage. We reviewed data from a range of functional and structural studies of early diabetic eye disease and computed standardized effect size as a measure of diagnostic power, allowing the studies to be compared quantitatively. We then derived minimum performance criteria for tests to provide useful clinical endpoints. This included the criteria that tests should be rapid and easy so that children with type 1 diabetes can be followed into adulthood with the same tests. We also defined attributes that lend test data to further improve performance using Machine/Deep Learning. Data from a new form of objective perimetry suggested that the criteria are achievable.

Multimodal imaging analysis for the impact of retinal peripheral lesions on central neurovascular structure and retinal function in type 2 diabetes with diabetic retinopathy

OBJECTIVES

To explore the possible role of peripheral lesions (PLs) detected by ultrawide field (UWF) imaging system on central neurovascular structure and retinal function.

METHODS

Ninety-seven diabetic patients were included in this cross-sectional study using UWF pseudocolour colour imaging with Optos Daytona (Optos, PLC). UWF images were graded as with predominantly peripheral lesions (PPLs) and without PPL. Macular neurovascular alterations and retinal function were measured by optical coherence tomography angiography (OCTA) and RETeval device, respectively. Central microcirculation and retinal function were compared between eyes with and without PPL.

RESULTS

The study evaluated 186 eyes (97 patients; 43 females (44.3%)), including 92 eyes without PPL and 94 eyes with PPL. Central retinal vessel density was comparable between eyes with and without PPL. Delayed implicit time and decreased pupil area ratio were found in the PPL group compared with eyes without PPL, and this difference remained unchanged after adjusting for systemic factors (all p＜0.01).

CONCLUSIONS

Our study suggests that retinal function is worse in diabetic eyes with PPL. These findings challenged the conventional ETDRS protocols which ignored peripheral retina in determining DR severity. Furthermore, combining UWF imaging with RETeval system to detect more retinal abnormalities may be helpful in DR management.

Dynamic and Static Pupil Changes After Near Work: Comparison Between Reading a Book and Using a Smartphone

Objectives

Decreased static pupil size due to accommodation is a common clinical finding; however, changes in pupillary dynamic responses after near-work activities such as reading a book and using a smartphone are not well understood.

Methods

The present study was performed on 76 right eyes of 76 volunteers (mean age: 20.95±2.34 years) who had ocular near activity more than 4 h per day. The participants were divided into two groups based on the dominant activity, reading a book (Group 1) or using a smartphone (Group 2). Evaluation of dynamic and static parameters of the pupil was performed before and after 1 h of continuous routine eye activity in both groups and compared.

Results

Near work reduced pupil diameter (PD) in all static components (p<0.001) and the amount of change in the min PD (p=0.039) and mesopic PD (p=0.043) were different between two groups and were higher in Group 1 (both, p<0.05). Dynamic elements showed a decrease in initial diameter, amplitude and velocity of contraction and dilation, and an increase in other components so that the changes after using smartphone were significant in all dynamic parameters (all, p<0.05), but reading the book only made a significant difference in the initial diameter, amplitude, and velocity of contraction and duration of dilation (all, p<0.05); the changes were only different in the initial diameter between the two studied groups, which was higher in Group 1 (p=0.047).

Conclusion

The present study showed that reading a book and using smartphone cause changes in the pupil components, which were decreasing in diameter components and velocity of changes and increasing in latency of changes; the type of ocular work may affect the changes.

Retinal neural dysfunction in diabetes revealed with handheld chromatic pupillometry

BACKGROUND

To evaluate the ability of handheld chromatic pupillometry to reveal and localise retinal neural dysfunction in diabetic patients with and without diabetic retinopathy (DR).

METHODS

This cross-sectional study included 82 diabetics (DM) and 93 controls (60.4 ± 8.4 years, 44.1% males). DM patients included those without (n = 25, 64.7 ± 6.3 years, 44.0% males) and with DR (n = 57, 60.3 ± 8.5 years, 64.9% males). Changes in horizontal pupil radius in response to blue (469 nm) and red (640 nm) light stimuli were assessed monocularly, in clinics, using a custom-built handheld pupillometer. Pupillometric parameters (phasic constriction amplitudes [predominantly from the outer retina], maximal constriction amplitudes [from the inner and outer retina] and post-illumination pupillary responses [PIPRs; predominantly from the inner retina]) were extracted from baseline-adjusted pupillary light response traces and compared between controls, DM without DR, and DR. Net PIPR was defined as the difference between blue and red PIPRs.

RESULTS

Phasic constriction amplitudes to blue and red lights were decreased in DR compared to controls (p < 0.001; p < 0.001). Maximal constriction amplitudes to blue and red lights were decreased in DR compared to DM without DR (p < 0.001; p = 0.02), and in DM without DR compared to controls (p < 0.001; p = 0.005). Net PIPR was decreased in both DR and DM without DR compared to controls (p = 0.02; p = 0.03), suggesting a wavelength-dependent (and hence retinal) pupillometric dysfunction in diabetic patients with or without DR.

CONCLUSIONS

Handheld chromatic pupillometry can reveal retinal neural dysfunction in diabetes, even without DR. Patients with DM but no DR displayed primarily inner retinal dysfunction, while patients with DR showed both inner and outer retinal dysfunction.