Association of Metformin With the Development of Age-Related Macular Degeneration

Importance

Age-related macular degeneration (AMD) is a leading cause of blindness with no treatment available for early stages. Retrospective studies have shown an association between metformin and reduced risk of AMD.

Objective

To investigate the association between metformin use and age-related macular degeneration (AMD).

Design, Setting, and Participants

The Diabetes Prevention Program Outcomes Study is a cross-sectional follow-up phase of a large multicenter randomized clinical trial, Diabetes Prevention Program (1996-2001), to investigate the association of treatment with metformin or an intensive lifestyle modification vs placebo with preventing the onset of type 2 diabetes in a population at high risk for developing diabetes. Participants with retinal imaging at a follow-up visit 16 years posttrial (2017-2019) were included. Analysis took place between October 2019 and May 2022.

Interventions

Participants were randomly distributed between 3 interventional arms: lifestyle, metformin, and placebo.

Main Outcomes and Measures

Prevalence of AMD in the treatment arms.

Results

Of 1592 participants, 514 (32.3%) were in the lifestyle arm, 549 (34.5%) were in the metformin arm, and 529 (33.2%) were in the placebo arm. All 3 arms were balanced for baseline characteristics including age (mean [SD] age at randomization, 49 [9] years), sex (1128 [71%] male), race and ethnicity (784 [49%] White), smoking habits, body mass index, and education level. AMD was identified in 479 participants (30.1%); 229 (14.4%) had early AMD, 218 (13.7%) had intermediate AMD, and 32 (2.0%) had advanced AMD. There was no significant difference in the presence of AMD between the 3 groups: 152 (29.6%) in the lifestyle arm, 165 (30.2%) in the metformin arm, and 162 (30.7%) in the placebo arm. There was also no difference in the distribution of early, intermediate, and advanced AMD between the intervention groups. Mean duration of metformin use was similar for those with and without AMD (mean [SD], 8.0 [9.3] vs 8.5 [9.3] years; P = .69). In the multivariate models, history of smoking was associated with increased risks of AMD (odds ratio, 1.30; 95% CI, 1.05-1.61; P = .02).

Conclusions and Relevance

These data suggest neither metformin nor lifestyle changes initiated for diabetes prevention were associated with the risk of any AMD, with similar results for AMD severity. Duration of metformin use was also not associated with AMD. This analysis does not address the association of metformin with incidence or progression of AMD.

Retrobulbar block for open-eye injuries: a report of 19 cases

In open-eye injuries, which are often emergency procedures where the patient may have a full stomach or be in precarious health, retrobulbar anesthesia offers definite advantages over general anesthesia. A "low-volume" technique is described which gives adequate anesthesia without dangerously increasing intraocular pressure. A table containing the salient description and outcome of 19 anesthetics given in this manner is included.

Reducing the need for intubation in plastic surgery

Many plastic surgery procedures that have traditionally been performed under general endotracheal anesthesia may safely be undertaken using a ketamine-based intravenous sedation technique. General endotracheal anesthesia has many drawbacks, including lack of patient acceptance. Ketamine-based intravenous sedation technique includes the following steps: 1. The patient is placed in a dissociated state using sedative and narcotic agents accompanied by a subanesthetic dose (0.5 mg/kg) of ketamine. 2. A dilute local anesthetic solution (0.25% lidocaine with 1:2,000,000 epinephrine) is infiltrated into the involved tissues to provide anesthesia and hemostasis. 3. The patient is maintained in a tranquil state throughout the procedure by periodic titration of additional doses of sedative and narcotic agents. Advantages of the technique include reducing the need for intubation and its associated hazards, dramatically decreased blood loss due to use of dilute epinephrine solution, reduced recovery time, ability of patients to respond to commands during surgery, avoidance of positioning injuries and increased rapport between patient, surgeon and anesthetist. Disadvantages include respiratory depression and potential for hypoxia. Dissociative intravenous sedation combined with dilute local anesthetic provides a useful addition to the anesthetist's armamentarium.

Retrobulbar block: a review for the clinician

Recent improvements in technique have made cataract surgery a popular procedure in the outpatient setting. One of those advances has been the use of retrobulbar block instead of general anesthesia. This article explains the anatomy, pharmacology, technique and complications of retrobulbar block.

Hepatic and peripheral insulin resistance: a common feature of type 2 (non-insulin-dependent) and type 1 (insulin-dependent) diabetes mellitus

Hepatic glucose production (3H-glucose technique) and insulin-mediated glucose uptake (insulin clamp technique) were measured in 38 Type 2 (non-insulin-dependent) and 11 Type 1 (insulin-dependent) diabetic patients. Fasting plasma glucose concentration was 8.3 +/- 0.5 mmol/l in the former, and 9.6 +/- 1.3 mmol/l in the latter group; the respective fasting plasma insulin levels were 19 +/- 2 mU/l (p less than 0.005 versus 13 +/- 1 mU/l in 33 age-matched control subjects), and 9 +/- mU/l (p less than 0.01 versus 14 +/- 1 mU/l in 36 younger control subjects). In the fasting state, hepatic glucose production was slightly increased (15%, 0.1 greater than p greater than 0.05) in the Type 2 diabetic patients and markedly elevated (65%, p less than 0.001) in the Type 1 patients compared with their respective control groups. In both groups of diabetic subjects, the rates of hepatic glucose production were inappropriately high for the prevailing plasma glucose and insulin levels, indicating the presence of hepatic resistance to insulin. Basal plasma glucose clearance was also significantly reduced in both the Type 2 (34%) and the Type 1 (14%) diabetic subjects. The fasting plasma glucose concentration correlated directly with hepatic glucose production, and inversely with plasma glucose clearance. During the insulin clamp, plasma insulin was maintained at approximately 100 mU/l in all groups, while plasma glucose was maintained constant at the respective fasting levels. Total glucose uptake was reduced in both the Type 2 (4.57 +/- 0.31 versus 6.39 +/- 0.25 mg . min -1 . kg -1 in the control subjects, p less than 0.01) and the Type 1 (4.77 +/- 0.48 versus 7.03 +/- 0.22 mg . min -1 . kg -1, p less than 0.01)diabetic patients. Insulin-stimulated glucose clearance was reduced to a similar extent in Type 2 (54%) and Type 1 (61%) diabetic subjects, and correlated directly with fasting glucose clearance. These results show that insulin resistance is a common feature of both types of diabetes and can be demonstrated in the basal as well as the insulin-stimulated state. Both hepatic and peripheral resistance to the action of insulin contribute to diabetic hyperglycaemia.

Insulin resistance is a prominent feature of insulin-dependent diabetes

Tissue sensitivity to insulin was examined in 36 control subjects and 19 insulin-dependent diabetics with diabetes of long-standing duration (mean = 10 ± 3 yr) employing the insulin clamp technique (Δ plasma insulin concentration ∼100 βU/ml). Eleven of the diabetics (group I) were studied at their fasting hyperglycemic level (173 mg/dl); the remaining 8 diabetics (group II) were studied after lowering their plasma glucose concentration to euglycemic levels (90 mg/dl). Despite plasma glucose levels that were almost twice as great in the diabetics (group 1,173 versus 91 mg/dl, P < 0.001), insulin-mediated glucose metabolism, 4.77 ± 0.18 mg/kg · min, was reduced by 32% versus controls, 7.03 ± 0.22 mg/kg · min (P < 0.01). When the control subjects were restudied at plasma glucose levels (166 ± 2 mg/dl) that were comparable to those of the diabetics, insulin-mediated glucose metabolism was 12.14 ± 0.96 mg/kg · min (P < 0.01). In diabetics studied at euglycemic levels (group II) insulin-mediated glucose metabolism, 3.39 ± 0.30 mg/kg · min, was reduced even further. The metabolic clearance rate in the 19 diabetics, 3.31 ± 0.23 mg/kg · min, was reduced by 58% compared with controls, 7.83 / 0.25 (P < 0.001). These results emphasize the severe degree of insulin resistance that exists in the insulin-dependent diabetics. Basal hepatic glucose production in the diabetic group, 2.96 ± 0.24 mg/kg · min, was 26% greater than in the controls, 2.35 ± 0.04 (P < 0.001). The fasting plasma glucose concentration displayed a strong positive correlation (r = 0.857, P < 0.001) with basal hepatic glucose production and was weakly and inversely correlated (r = −0.413, P = 0.07) with the basal glucose clearance. Following hyperinsulinemia, however, suppression of hepatic glucose production was ∼ 9 5% in both diabetics and controls, suggesting that peripheral tissues are primarily responsible for the observed impairment in insulin-mediated glucose uptake. The present results indicate that impaired insulin action is a common feature of insulin-dependent diabetics, despite daily insulin requirements (35 ± 2 U/day) that would not clinically characterize them as being insulin resistant.