Vitreous Volume (Vv) Syndrome Is Associated With Myopic Refractive Surprise After Cataract Surgery – Quantel Ultrasound Biomicroscopy (Ubm) And Anterion Optical Coherence Tomography (Oct) Study Of Anterior Segment Of Short Eyes

To compare the errors of predicted postoperative refraction (PPR) in group of short eyes with Vitreous volume (VV) syndrome to group of other short eyes (SE). VV syndrome is a shift of ciliary body and iris anteriorly on anterior segment imaging due to increased vitreous cavity volume. VV syndrome may be defined using different parameters for different instruments. VV syndrome for the purpose of this study using Quantel UBM imaging is defined as ciliary angle ≥ 15 degrees, ciliary-spur layer distance ≤ 0.3 mm, iris-spur layer distance ≤ 0.1 mm and lens thickness ≤ 5.2 mm. Actual pseudophakic anterior chamber depth (pACD) measured using UBM and Anterion OCT is to be compared to predicted pACD to explain the errors of PPR.

Private referral practice Great Lakes Eye Consultants, Traverse City, USA and MUS, Bratislava, Slovakia, EU

Inclusion criteria of this retrospective study were 1/ good quality UBM of the entire anterior segment, 2/ axial length of 22.75 mm or 3/ cataract surgery using the same Acrysof platform IOL. Preoperative and postoperative optical biometry, measured refraction (MR), autorefraction (AR) and keratometry measurements were obtained. Standard quantitative analysis of UBM was developed using 16 anterior segment measurements. Three UBM measurements were obtained by two operators. The errors of predicted postoperative refractions were calculated as the difference between both postoperative AR and MR compared to predicted refractions. Predicted refractions were calculated using ESCRS website and Aladdin software using 9 different formulas.

The study included 20 patients. The average axial length was 21.86 mm. Repeatability of all 16 UBM parameters was very good with the intrapersonal and interpersonal variation using Pearson correlation coefficients of 0.8 to 0.99. Six patients fulfilled the criteria for Vitreous Volume Syndrome (VV) group and the other 14 patients constituted short eye (SE) group. The error of predicted postoperative refraction using measured refraction (MR) and Barrett Universal II formula in the VV group was -0.8 diopters (D) and in SE group was -0.1 D. The error of PPR using auto-refraction (AR) and Barrett Universal II formula in the VV group was -0.87 D and in the SE group it was +0.01 D.

Vitreous Volume (VV) syndrome is associated with myopic refractive surprise after cataract surgery of -0.7 D using MR and -0.8 D using AR in our group of 20 small eyes. Analysis of actual pACD confirmed that this is due to error in prediction of IOL position. New anterior segment analysis was developed with 16 parameters that is useful in better prediction of IOL position in short eyes and  may be useful in glaucoma, refractive errors and other eye conditions. New biomechanical model of the eye is presented with three layers of anterior segment of scleral spur, iris and ciliary body and two independent barriers of iris membrane and ciliary membrane, instead of current concept of iris-lens diaphragm.