Acute effects of caffeine and glucose intake on retinal vessel calibres in healthy volunteers.

PURPOSE: To evaluate the acute effects of caffeine and glucose intake on retinal vascular calibre of healthy adults. METHODS: This prospective crossover study was conducted at the Centre for Eye Research Australia (Melbourne, Australia). Standardized doses of 300 mg caffeine (approximately 3 cups coffee), 30 g glucose or 300 ml of water, were each given to 19 healthy subjects on separate days. Retinal photographs and blood pressure measurements were taken at baseline, 30-, 60- and 120-min after ingestion of each solution. Central retinal artery and vein equivalents (CRAE, CRVE) and the arterio-venule ratio were measured using computer-assisted software. The mean retinal vascular calibre measurements were compared between pre- and post-ingestion images. RESULTS: After caffeine intake, significant reductions were observed in mean CRAE of - 9.3 µm, - 10.4 µm and - 8.5 µm and CRVE of - 16.9 µm, - 18.7 µm and - 16.1 µm at 30-, 60- and 120-min after intake when compared with baseline (p ≤ 0.002 for all; paired t test). No significant changes were observed in mean retinal vascular calibre measurements after intake of either glucose or water when compared to baseline (p ≥ 0.072 for all). When controlling for baseline characteristics and blood pressure measurements, only caffeine intake had a significant effect on reducing both CRAE and CRVE at all time points post ingestion (p ≤ 0.003 for all, multiple linear regression model). CONCLUSION: Caffeine is associated with an acute vasoconstrictive effect on retinal arterioles and venules in healthy subjects. Factors other than blood pressure-induced autoregulation play a significant role in caffeine-associated retinal vasoconstriction.

Response to correspondence from Koerner and colleagues concerning our paper entitled: The effect of diluting povidone-iodine on bacterial growth associated with speech.

Clinicians adopt varying strategies for antisepsis with PI, which to this day remains efficient, economical and effective. Clinicians should prudently consider effective PI application, and we thank Koerner and Grzybowski for encouraging debate and raising the profile of this issue.

The association between intravitreal ranibizumab therapy and serum cytokine concentrations in patients with diabetic macular edema.

Aim: To investigate the association between intravitreal ranibizumab therapy and serum cytokine concentrations in patients with diabetic macular edema (DME). Methods: Twenty-five patients with center-involved DME were recruited prospectively. Serum samples were collected from the patients before and 4 weeks after two ranibizumab injections. The levels of 32 cytokines at these two time points were assessed using a multiplex array assay. Results: Following two ranibizumab injections, there was a statistically significant decrease in the median [interquartile range] levels of Interleukin 1-1beta (IL-1ß) from 5.56 [3.6, 8.75] to 2.33 [1.51, 2.89], Interleukin 13 (IL-13) from 4.30 [1.84, 18.55] to 0.38 [0.38, 0.78], granulocyte-colony stimulating factor (G-CSF) from 64.65 [42.9, 108] to 37.8 [27.3, 46.37], Interferon gamma (IFN-γ) from 241 [103.33, 753.4] to 94.4626 [42.04, 118.58], Interferon gamma-induced protein 10 (IP-10) from 234.68 [144.16, 285.98] to 158.73 [94.71, 198.64], Macrophage Inflammatory Protein-1 alpha (MIP-1α) from 3.65 [2.62, 11.02] to 1.41 [0.94, 1.88], and Tumor necrosis factor- alpha (TNF-α) from 131.09 [100.68,28 240.27] to 45.19 [24.04, 68.55]. There was a statistically significant increase in the levels of Interleukin 9 (IL-9) from 0.76 [0.76, 7.03] to 19.67 [5.36 27.76], Macrophage Inflammatory Protein-1 beta (MIP-1ß) from 0.28 [0.28, 30 0.28] to 6.79 [I3.74, 14.16], Vascular endothelial growth factor (VEGF) from 2.55 [2.55, 2.55] to 25.24 [14.51, 41.73], and soluble vascular endothelial growth factor -1 (sVEGFR-1) from 333.92 [204.99, 440.43] to 500.12 [38.7, 786.91]. A Bonferroni-corrected p value of 0.00156 was considered statistically significant. Conclusions: In patients with DME, intravitreal ranibizumab therapy appears to influence the serum levels of a range of cytokines. After two injections, intravitreal ranibizumab therapy appears to be associated with a significant decrease in inflammatory mediators and a rise in VEGF and sVEGFR1.

The effect of diluting povidone-iodine on bacterial growth associated with speech.

BACKGROUND: Povidone-Iodine (PI) may be diluted when used as an antiseptic prior to an intravitreal injection in an attempt to decrease patient discomfort. This study aims to investigate the effect of diluting povidone-iodine (PI) on bacterial growth from bacterial droplet dispersal associated with speech. METHODS: Participants read a standardised script for 5 min over a blood agar plate positioned at 20 cm in a simulated position of an intravitreal injection procedure. The blood agar plates were subject to a randomised pre-application of 1% PI; 2.5% PI; 5% PI and no pre-application (control). The plates were incubated at 37 °C for 72 h and the number of Colony Forming Units (CFUs) was determined. CFUs were summarised as median and interquartile range (IQR). Wilcoxon rank sum test was used to assess pairwise comparisons of the various PI concentrations to the control group. Any trend across PI concentration was assessed using Kendall's tau rank correlation. RESULTS: Twenty-one subjects participated. Control plates had a median growth of 25 CFUs (interquartile range [IQR]:15-40), 1% PI plates had a median growth of 30 CFUs (IQR:15-82), 2.5% PI had a median growth of 18 CFUs (IQR:10-32) and 5% PI had a median growth of 2 CFUs (IQR:0-5). There was significantly less bacterial growth with 5% PI compared to control (P < 0.001). Bacterial growth at 2.5% PI and 1% PI did not differ significantly from control. There was a statistically significant trend for decreasing colony count as PI concentration increased (P < 0.001). CONCLUSIONS: PI concentrations less than 5% are not effective at reducing bacterial growth from bacterial droplet dispersal associated with speech. When using PI for pre-injection antisepsis, concentrations below 5% should be avoided.

Study methodology and diabetes control in patients from the non-English diabetes management project (NEDMP).

BACKGROUND: To describe the clinical characteristics of non-English speaking patients from the Diabetes Management Project (NEDMP), and compare their diabetes management and severity of diabetic retinopathy (DR) with the English-speaking DMP sample (EDMP). DESIGN: A prospective study was conducted on non-English speaking adults with diabetes who attended the Royal Victorian Eye and Ear Hospital. PARTICIPANTS: 136 (90.1%) non-English speaking adults were assessed, with a mean age of 72.2 years (range: 50-88 years); 74 (54.4%) were male. METHODS: Participants completed interviewer-administered questionnaires and underwent visual acuity, fundus photography, optical coherence tomography, biochemistry and anthropometric measurements. The EDMP assessed 609 patients in 2009 using a similar protocol. MAIN OUTCOME MEASURES: Type and duration of diabetes, diabetes control and diabetic retinopathy. RESULTS: A total of 127 (93.4%) and 8 (5.9%) participants reported having type 2 and type 1 diabetes, respectively, with a median (IQR) duration of 17 (14) years. The proportion of patients with poor diabetes control (HbA1c ≥ 7%) in the NEDMP was similar to the EDMP (64.0% and 68.2%, respectively; P = 0.411). A significantly higher proportion of patients with DR in the NEDMP were found to have poor diabetes control (HbA1c ≥ 7%) compared to those without DR (80.9% vs. 50.0%, P = 0.003). Almost two-thirds of NEDMP patients (74/118) had DR and 23% (27/115) had diabetic macular edema. The prevalence of DR was similar between the NEDMP and EDMP studies, ranging from 25-30% and 28-29%. CONCLUSIONS: The clinical characteristics, diabetes control, and DR severity of English and non-English-speaking patients were similar. The high proportion of poor diabetes management in non-English speaking patients with DR suggests educational and behavioural interventions to improve glycaemic control are warranted.