Accuracy, Precision, and Residual Volume of Commonly Used Syringes for Intravitreal Injections and the Impact on Intraocular Pressure.

PURPOSE: To compare accuracy, precision, and residual volume of commonly used syringes for intravitreal injections (IVIs) and to assess the intraocular pressure (IOP) rise by variations in volumes delivered. DESIGN: Experimental laboratory study. SUBJECTS: No subjects were involved in this study. METHODS: We tested 8 syringe models with 2 different needle setups, with 2 different solutions (distilled water or glycerin) and target volumes (50 and 70 µL). To obtain the delivered and residual volumes, we weighed the syringe-needle setups with scale before liquid withdrawal, with liquid, and after liquid release. We also created an experimental eye model to determine the transient rise in IOP following stepwise 10-µL increases in injection volumes. MAIN OUTCOME MEASURES: Delivered and residual volumes, IOP rise. RESULTS: We tested a total of 600 syringe-needle setups. Becton Dickinson (BD) Ultra-Fine (0.34 ± 0.28 µL), Zero Residual (1.53 ± 1.15 µL), and Zero Residual Silicone Oil-free (1.40 ± 1.16 µL) syringes showed the lowest residual volume (P < 0.001) in comparison with the others (range: 24.86 ± 1.78 µL for Injekt-F to 51.97 ± 3.37 µL for Omnifix-F). The most accurate setups were (percentage deviation from target volume): Zero Residual Silicone Oil-free (+ 0.70%), Zero Residual 0.3 ml (+ 4.49%), BD Ultra-Fine (+ 7.83%), Injekt-F (9.42%), Norm-Ject (+ 15.88%), Omnifix-F (+ 16.96%), BD Plastipak Brazil (+17.96%), and BD Plastipak Spain syringes (+ 19.41%). There was a statistically significant difference between the Zero Residual Silicone Oil-free syringe and all other syringes (P < 0.0001), except for the Zero Residual 0.3-ml syringe (P = 0.029). The coefficient of variation was low for all syringes. The modeled IOP rise ranged from 32.3 (standard deviation [SD], 1.4) mmHg for 20-µL injection volume to 76.5 (SD, 1.0) mmHg for 80-µL injection volume. For the standard 50-µL injection volume, the peak pressure was 50.7 (SD, 0.1) mmHg, and the pressure rise duration was 28 (SD, 2) minutes. CONCLUSIONS: There were significant differences in accuracy and residual volume between syringes, whereas they showed a high precision. Volume excess results in a considerable increase in IOP rise after injection. These findings may provide a relevant overview to clinicians and to both device and drug manufacturers regarding pharmacoeconomic, safety, and efficacy issues. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Abnormal vascular and neural retinal morphology in congenital lifetime isolated growth hormone deficiency.

OBJECTIVE: Experimental models demonstrate an important role of GH in retinal development. However, the interactions between GH and the neuro-vascularization of the human retina are still not clear. A model of untreated congenital isolated GH deficiency (IGHD) may clarify the actions of GH on the retina. The purpose of this work was to assess the retinal neuro-vascularization in untreated congenital IGHD (cIGHD). DESIGN: In a cross sectional study, we performed an endocrine and ophthalmological assessment of 25 adult cIGHD subjects, homozygous for a null mutation (c.57+1G>A) in the GHRH receptor gene and 28 matched controls. Intraocular pressure measurement, retinography (to assess the number of retinal vascular branching points and the optic disc and cup size), and optical coherence tomography (to assess the thickness of macula) were performed. RESULTS: cIGHD subjects presented a more significant reduction of vascular branching points in comparison to controls (91% vs. 53% [p=0.049]). The percentage of moderate reduction was higher in cIGHD than in controls (p=0.01). The percentage of individuals with increased optic disc was higher in cIGHD subjects in comparison to controls (92.9% vs. 57.1%). The same occurred for cup size (92.9% vs. 66.7%), p<0.0001 in both cases. There was no difference in macula thickness. CONCLUSIONS: Most cIGHD individuals present moderate reduction of vascular branching points, increase of optic disc and cup size, but have similar thickness of the macula.