VIVEX: A Formula for Calculating Individual Vitreous Volume: A New Approach Towards Tailored Patient Dosing Regime in Intravitreal Therapy

Abstract

Introduction Personalized medicine and patient-tailored drug dosing have been substantiated through thousands of clinical studies, demonstrating their safety and efficacy. The principle: “as much as necessary, as little as possible” is widely spread. Quantities and doses are therefore adjusted individually. This is not the case for intravitreal injections in the context of retinal diseases. Intravitreal injections are not adjusted in relation to the vitreous volume. The vitreous body is described as “approx. 4 cm 3 ” in the literature. Methods In this retrospective observational study, we included 72 eyes of patients who had undergone magnetic resonance imaging (MRI) of the orbit and biometry measurements of the anterior chamber depth (ACD) and axial length. After segmentation of the volume data, the vitreous volume was extracted by voxel integration, and a simple prediction model was derived to determine the vitreous volume from the axial length (AL) measurement with AL 3 ·π/6·(0.76 + 0.012·(AL-24). This is the volume of a sphere AL 3 ·π/6 and a correction term 0.76 + 0.012·(AL-24) to account for the portion of the vitreous in the entire globe and the proportional increase of the vitreous portion for long (myopic) eyes. Results Emmetropic eyes with an axial length of 22.50–23.50 mm had a vitreous volume of around 4.5–5.5 cm 3 . Myopic eyes with an axial length of 30.00 mm had a calculated vitreous volume of 9.0–10.0 cm 3 . Hypermetropic eyes with an axial length of 20.00 mm showed a vitreous volume of 3.0–4.0 cm 3 . Conclusions By implementing the new calculation formula on the IOLCON website, it will be easy to get the exact individual vitreous volume. The data could be used by retinal surgeons prior to surgery. The knowledge of anatomical dimensions and exact individual vitreous volume seems to be important for gas and silicone oil fillings. With the newly derived knowledge, multicentric studies can evaluate the impact of the dose in intravitreal therapies. Patient-tailored dosing could prevent side effects and improve effectiveness.

Calculated Drug Concentrations in Currently Available Intravitreal Therapies: Determination of Dilution Factor and Deviation From Recommended Doses

“…With reference to the anatomical spherical shape with the diameter of the axial length (AL), which has a volume of AL 3 ·π/6, a correction element of 0.76 + 0.012·(AL-24) was derived (VIVEX formula) [ 13 ].…”

“…Recently, studies using magnetic resonance imaging (MRI) and biometric measurements of the anatomy of the eyes, including anterior chamber depth, lens thickness, and axial length of the eyeball, have shown that there are impressive differences in the size ratios of the vitreous body volume [ 13 ]. The specification of a “standard volume” of 4-5 mL in literature and many books on ophthalmology appears to be inaccurate and outdated.…”

“…It has been shown that hyperopic, small eyes have vitreous volumes of 2-3 mL, and highly myopic, long eyes have large vitreous volumes of >9-10 mL, which is four times the volume of a hyperopic eye. The authors also introduced a novel calculation formula (vitreous volume exact (VIVEX)) to determine the vitreous body volume more accurately based on the axial length of the eye [ 13 ]. This can be done quickly and easily by measuring the axial length of the eye using ultrasound or modern biometric devices during a routine ophthalmological examination.…”

Letter to the Editor Regarding “VIVEX: A Formula for Calculating Individual Vitreous Volume: A New Approach Towards Tailored Patient Dosing Regime in Intravitreal Therapy”

“…We were really excited to read the article about VIVEX [ 1 ], a new formula that allows us to calculate vitreous volume very easily. It is very common for ophthalmologists to perform intravitreal injections with standard doses based on the knowledge that the volume of the vitreous in an adult eye is approximately 4.0 ml.…”

A Response to: Letter to the Editor Regarding “VIVEX—A Formula for Calculating Individual Vitreous Volume: A New Approach Towards Tailored Patient Dosing Regime in Intravitreal Therapy”

“…With great interest we have read the Letter to the Editor from Erduran et al regarding our experimental study to calculate the individual vitreous volume more precisely [ 1 ]. We very much appreciate the interest in our study and the positive response expressed by the authors in their letter [ 2 ].…”