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Predicting Vision Loss in Patients with Type 2 Diabetes 

Apr 21, 2020
 
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Chardae Whitner, 2020 PharmD. Candidate, Lake Erie College of Osteopathic Medicine

Could vision loss and the visual disturbances that diabetes patients experience be prevented?

Diabetes can be a complicated disease, with many compounding factors for patients diagnosed with the disease.  One of these many factors would be ocular complications, which are three times more likely to occur in patients with diabetes compared to those without. However, even with the evidence suggesting that patients with diabetes are at a high risk of developing ocular complications, there is limited data that explores the incidence of visual impairment and blindness in patients with diabetes.  Also, the predictors of vision loss have limited data. Research conducted by Drinkwater J. et al. aimed to assess the 4-year cumulative incidence of visual impairment and blindness and their determinants in well-characterized community-based people with type 2 diabetes.   

The Fremantle Diabetes Study Phase II (FDS2) recruited 1551 subjects to participate in a prospective, observational study.  Participants were selected from a zip code defined as an urban community surrounding the port of Fremantle in the state of Western Australia.  Also, individuals who participated in the Fremantle Diabetes Study Phase I (FDS1) were eligible to participate. 

During this 4-year study, participants were assessed at baseline and biennially with questionnaires covering health care utilization, medical condition, medication use, socioeconomic, demographic and lifestyle data, and physical examination.  Fasting blood glucose and urine samples were also obtained.  The visual acuity of the participants was measured using a Bailey Lovie chart at a distance of 3m in a well-lit room, with examiners using the best-corrected visual acuity measurement.  Visual acuity chart used was 6/48, parameters were set as follows: >6/19 and <6/48 was classified as visual impairment >6/48 and those who could only count fingers or worse was classified as blindness. This measurement was assessed at each biennial face-to-face visit.  The difference between the number of letters read by the best eye at baseline, and the year four visits was a way to determine if there was a change in vision.  This was defined as a difference in visual acuity of >10 letters (two lines of the visual acuity chart).  The presence and severity of retinopathy was assessed by using fundus photography; the severity of the diabetic retinopathy was classified as none, mild non-proliferative diabetic retinopathy, moderate non-proliferative diabetic retinopathy, or severe non-proliferative diabetic retinopathy.  Ascertainment of other ocular conditions was also accessed such as cataract or glaucoma. Researchers used The Hospital Morbidity Data Collection, which captures all hospitalizations within the state of Western Australia, to determine if participants of the study had intraocular lens implantation for a cataract before and during the follow-up to the year four visit.  Also, at each face-to-face visit subjects of the study were questioned as to if they had been told by a provider whether or not they had a cataract or glaucoma.  

From the results gathered from this 4-year prospective, observational study, 70 of the participants were excluded from the study due to missing visual acuity data at baseline or presence of visual impairment or blindness at baseline. Of the 1481 participants who had a normal or near-normal vision at baseline, 882 participants (58%) had their visual acuity measured at the Year 4 visit. For the participants included in the analysis, during the 4.1 years of follow-up the cumulative incidence of visual impairment was 0.9%, representing a crude incidence of 0.2% per year.  None of the participants who were evaluated with normal or near-normal vision at baseline were found to have developed blindness by the Year 4 visit. Of the visual acuity observed, a cumulative incidence of vision loss was 2.9% and 1.9% had improved visual acuity. 

The study also measured predictors of vision loss, and it was found that participants who had vision loss during follow up were more likely to be insulin-treated, have had a severe hypoglycemic event, have worse kidney function and be a current or ex-smoker at baseline compared to those without vision loss.  Those who had vision loss also were observed as having higher systolic blood pressure and worse kidney function than those without.  Those individuals who had improved visual acuity were likely to have had an intraocular lens inserted.   

This study found that modifiable risk factors were independently associated with vision loss in community-dwelling patients with type 2 diabetes, which were smoking, severe hypoglycemia and high uACR. Strategies that focus on smoking cessation, avoiding severe hypoglycemia, and persevering kidney function will be pivotal in preventing vision loss in patients with type 2 diabetes.  

Practice Pearls 

  • Avoiding hypoglycemia may prevent vision loss among individuals with type 2 diabetes. 
  • Preserving kidney function may prevent vision loss among individuals with type 2 diabetes.  
  • Smoking cessation may prevent vision loss among individuals with type 2 diabetes. 

Drinkwater, Jocelyn J., et al. “Incidence and Predictors of Vision Loss Complicating Type 2 Diabetes: The Fremantle Diabetes Study Phase II.” Journal of Diabetes and Its Complications, Elsevier, 22 Feb. 2020, www.sciencedirect.com/science/article/abs/pii/S1056872720300027?via=ihub. 

 

Chardae Whitner, 2020 PharmD. Candidate, Lake Erie College of Osteopathic Medicine