Short-term stability in refractive status despite large fluctuations in glucose levels in diabetes mellitus type 1 and 2

Eye Axial Length: Is There a Protective Link to Diabetic Retinopathy?

Diabetic retinopathy (DR) is a leading cause of vision impairment and blindness globally, particularly among working-age adults. As the prevalence of diabetes continues to rise, understanding factors that influence DR development and progression is increasingly important. Recent studies suggest a protective association between a longer axial length (AL) of the eye and the risk of DR, particularly in myopic individuals. This review explores the potential mechanisms underlying this relationship, including reduced retinal vascular density, altered retinal blood flow, and ocular biomechanics, which may collectively reduce the susceptibility of retinal tissues to hyperglycemic damage. However, limitations such as confounding factors, ethnic and genetic differences, and methodological challenges highlight the need for further research. This review aims to explore the relationship between AL and DR, examining the biological mechanisms that may underpin this association, summarizing the epidemiological evidence, discussing the clinical implications, and identifying directions for future research. Understanding the protective role of AL could have significant clinical suggestions, including more tailored screening intervals and personalized treatment approaches for DR. Future studies should focus on longitudinal analyses, mechanistic insights, and diverse populations to establish a clearer understanding of this relationship and its potential for novel therapeutic strategies.

Modelling ocular ageing in adults with well-controlled type I diabetes

Purpose

To develop a paraxial eye model based on a previously collected cohort of adults with well-controlled type 1 diabetes mellitus (DM1) and a limited range of refractive errors.

Methods

The study used the previously published biometric data of 72 participants (Age: 41.5 ​± ​12.4 years) with DM1. Measurements included objective refraction, anterior and posterior corneal radii of curvatures, and internal distances. Moreover, phakometry was used to determine the lens radii of curvature and lens equivalent indices, from which the lens powers were calculated. A multivariate linear regression was performed for each biometric parameter with respect to current age (Age), the time since the onset of diabetes (Tdb), and current levels of glycated hemoglobin (HbA1c). The vitreous chamber depth was determined from other distances, and lens equivalent index was chosen to balance the models. These were compared with an existing model for non-diabetic eyes.

Results

Some dependent parameters were not affected by the independent variables (spherical equivalent, anterior corneal radius of curvature, central corneal thickness), some were affected by time since onset (the lens radii of curvatures, anterior chamber depth) and others were affected by both age and time since onset (posterior corneal radius of curvature, lens thickness, axial length). None of the dependent parameters were affected by current levels of HbA1c.

Conclusions

The proposed model accurately describes the age-related changes in the eyes of people with DM1. In this description the age of diabetes onset plays an important role, especially if the diabetes onset occurred during childhood.

Eye disorders other than diabetic retinopathy in patients with diabetes

AIM

While diabetic retinopathy is the most specific complication of chronic hyperglycaemia, numerous other ocular conditions also can involve the eyes of people with diabetes. Cataract, glaucoma, age-related macular degeneration, retinal vascular occlusion, and acute ischaemic optic neuropathy combine to impair vision in people with diabetes, especially when they are old. This report provides a critical analysis and an overview of the current knowledge of the main ocular disorders (excluding diabetic retinopathy) and their association in patients with diabetes.

METHODS

A literature search strategy was conducted for all English-language literature with a systematic review of key references until 2021.

RESULTS

Patients with diabetes have a high-to-moderate increased risk for most of the usual ocular disorders we reviewed with the exception of age-related macular degeneration. Exposure to chronic hyperglycaemia promotes the development of many eye disorders while acute glucose changes are involved in refractive disorders, diabetic papillopathy and acute cataract.

CONCLUSION

Diabetes, beyond diabetic retinopathy, increases the risk of numerous eye disorders leading to low vision with implications for daily diabetes management. Even in the absence of clearly demonstrated benefit from glucose control in all eye conditions, achieving good glycaemic control and adherence to diabetes treatment will likely help avoid an additional risk of visual impairment in people with diabetes. In perspective, interesting findings suggesting a preventive effect of metformin use on age-related macular degeneration occurrence justify further studies.

Refractive Changes Associated with Diabetes Mellitus

BACKGROUND AND METHODS

Diabetes mellitus is the most prevalent endocrinedisease in developed countries. In people with diabetes in addition to visionloss caused by diabetic retinopathy transient visual disturbances may occurfrequently caused by refractive changes. These changes in refraction are associated with variations in blood glucose levelsbut the underlying mechanism is still not fully understood. A systematic reviewwith a comprehensive literature search was performed in order to clarify the underlyingmechanisms regarding the connection of glycaemic control and refractive shift.

RESULTS

Some studies have shown that increasedblood sugar leads to a myopic shift whilst others demonstrated that this changeis in a hyperopic direction. Changes in visual acuity in patients with diabetescould be an indicator of inadequate metabolic control or even the first sign ofdiabetes mellitus.

CONCLUSION

This reviewgives a brief overview of current research regarding potential mechanisms ofglycemic control influence on refractive error. The aim isto emphasizethe importance ofunderstanding the relationship ofblood glucose concentration and refractive changes as one of thecommon but overlooked diabetic complications.

Visual complications in diabetes mellitus: beyond retinopathy

Diabetic retinopathy is the most common cause of vision loss in people with diabetes mellitus; however, other causes of visual impairment/loss include other retinal and non-retinal visual problems, including glaucoma, age-related macular degeneration, non-arteritic anterior ischaemic optic neuropathy and cataracts. Additionally, when a person with diabetes complains of visual disturbance despite a visual acuity of 6/6, abnormalities in refraction, contrast sensitivity, straylight and amplitude of accommodation should be considered. We review and highlight these visual problems for physicians who manage people with diabetes to ensure timely referral and treatment to limit visual disability, which can have a significant impact on daily living, especially for those participating in sports and driving.

Transient Ocular Wavefront Data in Type 1 Diabetes Mellitus

PURPOSE

We report transient ocular wavefront and blood glucose data for one patient with acute type 1 diabetes mellitus after the treatment with insulin has been initiated.

CASE REPORT

The wavefront data for both eyes of a 34-year-old male patient were examined by a Hartmann-Shack wavefront sensor. Refraction data and higher-order aberrations were recorded during 130 days for eyes in natural conditions, without cycloplegia. At the beginning, we sampled data every 3 to 4 days and enlarged the intervals, when values settled. In total, we report 20 measurements and 1 baseline entry. Blood glucose levels were recorded at least six times a day during the complete period. For the equivalent sphere, we recorded a bilateral hyperopic shift of 5 D from -2.75 DS to +2.25 DS, followed by a reverse myopic shift of the same amount. The equivalent sphere peaked about 15 to 18 days after the treatment with insulin had begun. Cylinder values kept remarkably stable. Higher-order aberrations are dominated by the spherical aberration. The Zernike coefficient c12 for both eyes changed substantially from OD 0.036 μm and OS 0.062 μm to OD 0.24 μm and OS 0.22 μm (5 mm pupil diameter) following the time pattern of the equivalent sphere. About 60 days after they had reached their peak, all refraction values and higher-order aberrations stabilized at their baseline levels. The baseline was defined by records taken 4 years before the treatment with insulin was commenced.

CONCLUSIONS

Wavefront aberrometry gives quantitative insights in the transient alteration and recovering of the eye's optics whilst the therapy of acute type 1 diabetes mellitus is being initiated. The data of this case support the assumption that variations in the crystalline lens, most probably the modification of its refractive gradient index, as a cause for the transient behavior. An explanation is still missing.