Functional and Structural Changes of the Retinal Nerve Fiber Layer and Ganglion Cell Complex in Heavy Smokers

Alterations of the Ganglion Cell Complex in Age-Related Macular Degeneration: An Amish Eye Study Analysis

PURPOSE

To compare the ganglion cell complex (GCC) thickness in eyes with age-related macular degeneration (AMD) vs healthy controls in an elderly Amish population.

DESIGN

Prospective cross-sectional study.

METHODS

This is a post hoc analysis of the family-based prospective study of Amish subjects. Study subjects underwent imaging with the Cirrus HD-OCT (Carl Zeiss Meditec Inc) using a macular cube protocol of 512 × 128 scans (128 horizontal B-scans, each comprising 512 A-scans) over a 6 mm × 6 mm region centered on the fovea. The ganglion cell analysis algorithm calculated the GCC thickness by segmenting the outer boundaries of the retinal nerve fiber layer (RNFL) and inner plexiform layer (IPL) in all B-scans of the volume, with the region between these boundaries representing the combined thickness of the ganglion cell layer (GCL) and the IPL. A number of parameters were used to evaluate the GCC thickness: the average GCC thickness, minimum (lowest GCC thickness at a single meridian crossing the elliptical annulus), and sectoral (within each of 6 sectoral areas: superior, superotemporal, superonasal, inferior, inferonasal, and inferotemporal). The stage of AMD was graded on color fundus photographs in accordance with the Beckman Initiative for Macular Research classification system.

RESULTS

Of 1339 subjects enrolled in the Amish eye study, a total of 1294 eyes of 1294 subjects had all required imaging studies of sufficient quality and were included in the final analysis. Of these, 798 (62%) were female. Following age adjustment, the average GCC thickness was significantly (P < .001) thinner in AMD subjects (73.71 ± SD; 13.77 µm) compared to normals (77.97 ± 10.42 µm). An independent t test showed that the early AMD (75.03 ± 12.45 µm) and late AMD (61.64 ± 21.18 µm) groups (among which eyes with geographic atrophy [GA] had the lowest thickness, of 58.10 ± 20.27 µm) had a statistically significant lower GCC thickness compared to eyes without AMD. There was no significant differences in average GCC thickness between early AMD and intermediate AMD (76.36 ± 9.25 µm) eyes.

CONCLUSIONS

The GCC thickness in AMD eyes is reduced compared to normal eyes; however, the relationship is complex, with the greatest reduction in late AMD eyes (particularly eyes with GA) but no difference between early and intermediate AMD eyes.

Retinal nerve fiber layer and ganglion cell complex thickness in diabetic smokers without diabetic retinopathy

PURPOSE

To compare the thickness of the retinal nerve fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GC-IPL) in smoker and nonsmoker diabetics without diabetic retinopathy.

MATERIALS AND METHODS

Patients with diabetes were divided into two groups according to their smoking status: Group 1 consisted of 38 smoker diabetics who had chronically smoked more than 20 cigarettes per day for more than five years; Group 2 consisted of 38 nonsmoker diabetics. After a detailed ophthalmologic examination, the mean and regional (superior, supratemporal, inferior, inferotemporal, temporal, nasal, superonasal, and inferonasal) RNFL and GC-IPL thicknesses were measured with spectral-domain optic coherence tomography (SD-OCT) and compared between groups.

RESULTS

The mean age was 54.7 ± 10.5 and 51.2 ± 9.7 years in the smoker and nonsmoker groups, respectively (p = 0.14). Gender, duration of diabetes, and the mean axial length were similar between groups (p:0.43, p:0.54, p: 0.52, respectively). Mean RNFL thickness was 89.1 ± 8.0 µm in the smoker group and 93.4 ± 7.0 µm in the nonsmoker group, and it was significantly thinner in the smoker group (p = 0.01). The temporal RNFL thickness in the smoker group was thinner than in the nonsmoker group (p = 0.02). There was no difference in superior, inferior, and nasal RNFL thicknesses between the groups (p = 0.31, p = 0.12, p = 0.39, respectively). The mean macular GC-IPL thickness of the smoker and nonsmoker groups was 78.53 ± 15.74 µm and 83.08 ± 5.85 µm, respectively (p = 0.09). Superior, superonasal, inferonasal, inferior, inferotemporal, and superotemporal quadrant GC-IPL thicknesses were similar between the groups (p = 0.07, p = 0.60, p = 0.55, p = 0.77, p = 0.71, p = 0.08, respectively). The groups showed no difference in minimum GC-IPL thickness (p = 0.43). There was a significant negative correlation between smoking exposure and mean, inferior quadrant RNFL thicknesses in the smoker group (p = 0.04, r= -0.32, and p = 0.01, r= -0.39, respectively).

CONCLUSION

Mean RNFL thickness was significantly thinner in smoker diabetics. Although not statistically significant, especially mean, superior, and superotemporal GC-IPL was thinner in smoker diabetics. The results suggest a potential association between the coexistence of diabetes and smoking with alterations in RNFL and GC-IPL thickness.

Evaluation of peripapillary choroidal vascularity index in young smokers

Purpose: This retrospective study aimed to compare the peripapillary choroidal vascularity index (CVI) between young smokers who smoked less than 5 packs/year and non-smokers.Methods: The study included 52 smokers and 67 non-smokers, and comprehensive eye examinations were performed on all participants. Axial lengths (AL) were measured, and peripapillary enhanced depth imaging optical coherence tomography (EDI-OCT) images were obtained and evaluated using the Open Source ImageJ software. The CVI, total choroidal area (TCA), luminal area (LA), stromal area (SA), and retinal nerve fibre layer (RNFL) quadrants were compared between the two groups.Results: The mean age of the smokers was 23.76 ± 1.84 years, and for non-smokers, it was 23.98 ± 2.18 years. The mean peripapillary CVI for smokers was 0.65 ± 0.08, and for non-smokers, it was 0.67 ± 0.03. No statistically significant difference in CVI was observed between the two groups. However, statistically significant differences were found in the temporal inferior (TI), temporal superior (TS), nasal inferior (NI), and nasal superior (NS) quadrants of the RNFL between the two groups (p < 0.05). There was no correlation between the number of packs/year and CVI values in the smoking group (r = 0.031, p = 0.826).Conclusion: The study revealed no significant difference in CVI among young smokers who smoked less than 5 packs/year compared to non-smokers. However, there was a statistically significant decrease in the TI, TS, NI, and NS quadrants of the RNFL in early-age smokers.

Optical coherence tomography angiography in diabetic retinopathy

There remain many unanswered questions on how to assess and treat the pathology and complications that arise from diabetic retinopathy (DR). Optical coherence tomography angiography (OCTA) is a novel and non-invasive three-dimensional imaging method that can visualize capillaries in all retinal layers. Numerous studies have confirmed that OCTA can identify early evidence of microvascular changes and provide quantitative assessment of the extent of diseases such as DR and its complications. A number of informative OCTA metrics could be used to assess DR in clinical trials, including measurements of the foveal avascular zone (FAZ; area, acircularity, 3D para-FAZ vessel density), vessel density, extrafoveal avascular zones, and neovascularization. Assessing patients with DR using a full-retinal slab OCTA image can limit segmentation errors and confounding factors such as those related to center-involved diabetic macular edema. Given emerging data suggesting the importance of the peripheral retinal vasculature in assessing and predicting DR progression, wide-field OCTA imaging should also be used. Finally, the use of automated methods and algorithms for OCTA image analysis, such as those that can distinguish between areas of true and false signals, reconstruct images, and produce quantitative metrics, such as FAZ area, will greatly improve the efficiency and standardization of results between studies. Most importantly, clinical trial protocols should account for the relatively high frequency of poor-quality data related to sub-optimal imaging conditions in DR and should incorporate time for assessing OCTA image quality and re-imaging patients where necessary.

Effects of chewing tobacco on corneal endothelium in patients with diabetes mellitus

OBJECTIVE

To determine the impact of tobacco chewing on corneal endothelial structure in patients with diabetes mellitus (DM).

METHODS

Corneal endothelial parameters (endothelial cell count, ECD; coefficient of variation, CV; hexagonality, Hex, and central corneal thickness, CCT) were analysed in 1234 eyes of 1234 patients using non-contact specular microscopy (EM 4000 Tomey Nishi-Ku, Nagoya, Aichi, Japan). The study group (with a present history of tobacco chewing) comprising of 948 subjects, with 473 having DM was compared with age and gender-matched control group comprising of 286 subjects (139 having DM) with no history of tobacco use in any form.

RESULTS

Tobacco chewers had a significantly reduced ECD (P = 0.024) and Hex (P = 0.009) as compared with non-chewers. Similar results were noted in ECD (P = 0.004) and Hex (P = 0.005) in patients with DM. Tobacco chewers had a significantly decreased ECD values among males, HbA1C ≤ 7.5% and duration of DM ≤ 20 years, and significantly decreased Hex among those with >50 years of age, females, and duration of DM > 20 years. The CV and CCT values were comparable between the study and the control groups. Tobacco chewers showed a significant association of ECD with age, HbA1C, and duration of DM; CV with HbA1C; Hex with age and duration of DM; and CCT with gender, age, HbA1C and duration of DM.

CONCLUSIONS

Tobacco chewing may negatively impact corneal health, especially confounded by additional factors like age and DM. These factors must be accounted for in the pre-operative evaluation of such patients prior to any intra-ocular surgery.

HORNBILL: a phase I/IIa trial examining the safety, tolerability and early response of BI 764524 in patients with diabetic retinopathy and diabetic macular ischaemia-rationale, study design and protocol

Background

Diabetic macular ischaemia (DMI) is a complication of diabetic retinopathy that leads to irreversible vision loss. DMI is characterised by reduced retinal vessel density and enlargement of the foveal avascular zone (FAZ). Despite its clinical burden, there is no formal consensus on the definition of DMI, and no approved treatment. Semaphorin 3A (Sema3A) is an axonal guidance molecule that blocks revascularisation of the ischaemic retina. Sema3A modulation is therefore a promising mechanism of action for the treatment of ischaemic eye diseases. BI 764524 is an intravitreal anti-Sema3A ischaemia modulator agent.

Methods

HORNBILL (NCT04424290) is a phase I/IIa trial comprising a non-randomised, open-label, single rising dose (SRD) part and a randomised, masked, sham-controlled multiple dose (MD) part to investigate the safety, tolerability and early biological response of ischaemia modulator BI 764524 in adults (≥18 years) with DMI. DMI will be defined using optical coherence tomography angiography (OCTA) as either any degree of disruption in the retinal vascularity (SRD) or a FAZ of ≥0.5 mm² (MD). Subjects in the SRD part will receive 0.5, 1.0 or 2.5 mg of BI 764524; the maximum tolerated dose will then be used in the MD part. A minimum of 12 subjects will be enrolled into the SRD part; planned enrollment is 30 for the MD part. The primary endpoint of the SRD part is the number of subjects with dose-limiting adverse events (AEs) until day 8. The primary endpoint of the MD part is the number of subjects with drug-related AEs from baseline to end of study, and secondary endpoints include change from baseline in the size of the FAZ, best-corrected visual acuity and central retinal thickness.

Discussion

DMI is a poorly defined condition with no treatment options. HORNBILL is the first clinical trial to assess a treatment for DMI and to use OCTA as a means to define and examine DMI. The OCTA data generated in this trial could form the basis of formal diagnostic criteria for DMI. Furthermore, the novel mechanism of action (Sema3A modulation) explored in this trial has the potential to revolutionise the treatment landscape for patients with DMI.

Trial registration

ClinicalTrials.govNCT04424290; EudraCT 2019-004432-28. Registered on 9 June 2020

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06527-y.

Living Without a Diagnosis: A Patient's Perspective on Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy (DR) that can result in progressive and irreversible vision loss. DMI is associated with damage in the vessels that supply blood to the retina and the enlargement of the foveal avascular zone. Currently, there are no approved treatments specifically for DMI. Furthermore, there is limited published information about the prognosis, prevalence or outcomes of DMI, and there is no consensus regarding diagnostic criteria. It is vital to ensure that there is sufficient, accessible and accurate information available to support patients, caregivers and physicians. To lay the foundation for more research into DMI and its impact on patients, we (a patient with DMI and an expert ophthalmologist) have worked together to interweave our personal perspectives and clinical experiences with a review of currently available literature on DMI. The development of a set of confirmed diagnostic criteria for DMI would assist both patients and physicians, allowing patients to access validated information about their condition and supporting the development of clinical trials for treatments of DMI. Training for physicians must continue to emphasise the importance of treating a patient holistically, rather than only treating their symptoms. Most importantly, developing trust and a healthy rapport between a patient and their physician is important in managing health anxiety and ensuring adherence to beneficial treatments or lifestyle adjustments; physicians must cultivate an open and flexible management approach with their patients. Finally, holistic educational programmes for patients, physicians and the general public around DMI and how it can affect daily functioning would facilitate general understanding and disease awareness.

Diabetic macular ischemia (DMI) is a common problem for patients with diabetic retinopathy that can lead to sight loss. There is very little information available about DMI, particularly from a patient’s point of view. To address the lack of information about DMI, we (a person with DMI and her eye doctor) have worked together to examine what it is like to live with DMI. It is important to provide clear and accessible information about diseases to patients and carers. The lack of information about DMI may be upsetting for some people, and should be addressed with more research. Developing of a set of confirmed signs and symptoms for the diagnosis of DMI would allow people to be more confident in the information that they receive about their disease, and support the development of treatments for DMI. The support of others is central to the wellbeing of people with vision loss. Although people with vision loss may also lose independence, care from loved ones can help to improve quality of life. Most importantly, developing trust between a patient and their doctor is central to managing people’s fears about their eyesight, and making sure that they follow helpful advice. Doctors must use an open and flexible approach with their patients, providing information in an honest and understandable way.

Impact of tobacco use on corneal thickness and endothelial health: a systematic review with meta-analyses

PURPOSE

To investigate the impact of tobacco use on corneal thickness and corneal endothelial health.

METHODS

We searched the PubMed/MEDLINE, EMBASE, the Cochrane Central and all affiliated databases of the Web of Science on 20 July 2020. Two authors reviewed the studies and extracted the data in an independent fashion. Studies were reviewed qualitatively in the text, and central corneal thickness (CCT) and corneal endothelial characteristics (endothelial cell density, endothelial cell variability, average of endothelial cell size and endothelial cell hexagonality) were introduced for quantitative analyses.

RESULTS

Eighteen studies (2077 were smokers and 6429 non-smokers) were identified, of which 17 studies provided data eligible for one or more of the quantitative analyses. When compared to non-smokers, smokers had a higher CCT (+3.3 μm, 95% CI: +0.9 to +5.7 μm, p = 0.007) and a lower endothelial cell density (-140 cells/mm² , 95% CI: -30 to -250 cells/mm² , p = 0.01). Other corneal endothelial measures did not differ significantly.

CONCLUSION

Tobacco use is associated with a higher CCT and lower corneal endothelium cell density, but the clinical impact of these findings is small. Further studies are warranted on patients with a priori poor corneal health, where smoking may constitute an important risk of further progression, for example upon anterior segment surgery.

Evaluation of the retinal nerve fiber layer with optic coherence tomography in patients with alcohol use disorder

OBJECTIVE

This study aims to evaluate the retinal nerve fiber layer (RNFL) with optical coherence tomography (OCT) among patients with alcohol and tobacco use disorder.

METHODS

This study included 29 patients and 29 age and gender-matched healthy participants without alcohol dependency. The patients underwent full ophthalmologic examination including visual acuity, intraocular pressure, anterior segment and fundus examinations, and RNFL measurements taken with spectral-domain OCT. The RNFL values of the two groups were compared with each other.

RESULTS

In comparison to the control group, the RNFL was found to be thinner in all quadrants in the group with alcohol and tobacco dependency. The RNFL thinning in the superotemporal, temporal, and inferotemporal quadrants was found to be statistically significant (P-values 0.012, 0.040 and 0.005, respectively).

CONCLUSIONS

Chronic alcohol and tobacco use may cause RNFL thinning. Assessment of RNFL thinning by OCT among patients with alcohol and tobacco dependency might be used to identify visual morbidity.

Retinal dysfunctions in regular tobacco users: The retina as a window to the reward circuit in addictive disorders

The nicotine contained in tobacco is a neuromodulator which affects neurotransmission within the brain. The retina is an easy way to study central synaptic transmission dysfunctions in neuropsychiatric disorders. The purpose of this study is to assess the impact of regular tobacco use on retinal function using pattern (PERG), flash (fERG) and multifocal (mfERG) electroretinogram (ERG). We recorded PERG, fERG and mfERG for 24 regular tobacco users and 30 healthy non-smoking subjects. The protocol was compliant with International Society for Clinical Electrophysiology of Vision standards. The amplitudes and peak times (PT) of P50, N95 waves (PERG), a-, b- and oscillatory potentials (fERG), and N1, P1, N2 (mfERG) were evaluated. Compared to non-smokers, the results (Mann-Whitney U test, Bonferroni correction) for tobacco users suggested a significant increase of ~ 1 ms in the PT of light-adapted 3.0 fERG b-wave (p = 0.002). Using mfERG, we observed the following increases in tobacco users: in ring 3 for P1 PT of ~1,5 ms and in ring 5 for P1 PT of ~ 1 ms and for N2 PT of ~ 1 ms (p = 0.002, p = 0.002 and p = 0.006). It is our hypothesis that these results reflect the consequences of regular tobacco use on retinal synaptic transmission, and more specifically on dopaminergic and cholinergic transmission. We deduce that the retina may provide a crucial site of investigation for neurotransmission modulation of the reward circuit in regular tobacco users.

Looking Ahead: Visual and Anatomical Endpoints in Future Trials of Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy that can lead to progressive and irreversible visual loss. Despite substantial clinical burden, there are no treatments for DMI, no validated clinical trial endpoints, and few clinical trials focusing on DMI. Therefore, generating consensus on validated endpoints that can be used in DMI for the development of effective interventions is vital. In this review, we discuss potential endpoints appropriate for use in clinical trials of DMI, and consider the data required to establish acceptable and meaningful endpoints. A combination of anatomical, functional, and patient-reported outcome measures will provide the most complete picture of changes that occur during the progression of DMI. Potential endpoint measures include change in size of the foveal avascular zone measured by optical coherence tomography angiography and change over time in best-corrected visual acuity. However, these endpoints must be supported by further research. We also recommend studies to investigate the natural history and progression of DMI. In addition to improving understanding of how patient demographics and comorbidities such as diabetic macular edema affect clinical trial endpoints, these studies would help to build the consensus definition of DMI that is currently missing from clinical practice and research.