Annular Array Ultrasound in Ophthalmology

• Detection of posterior vitreous detachment: 20MHz annular array versus 10MHz single element [ Time Frame: Subjects will be examined with both the 20MHz annunlar array and 10MHz single element ultrasound during the same exam, approximately 30 minutes in duration. ] [ Designated as safety issue: No ]
  The investigators will examine eyes with both conventional 10MHz ultrasound and a 20MHz annular array with synthetic focusing. The investigators will evaluate and compare images acquired with both techniques and determine their relative efficacy in visualizing the presence or absence of posterior vitreous detachment.
  
  

The goal of this study is to develop and evaluate advanced annular-array transducer technology for rapid, high-definition imaging. The study will assess high frequency ultrasound (HFU, 40 & 20 MHz) annular arrays in imaging posterior vitreous detachments (PVDs) associated with diabetic retinopathy, the leading cause of blindness in the US working-age population according to Prevent Blindness America. Current HFU instruments do not use linear arrays for such applications because of a variety of technical and cost reasons. Instead, current HFU instruments use mechanically scanned, single-element transducers, which provide fine-resolution images over a very limited depth of field (DOF). For ophthalmic applications, a shallow DOF causes most ocular anatomy to be imaged with poor definition compared to the in-focus region; therefore, because only a small portion of the eye is in focus at a given time, detection and assessment of ocular conditions such as PVD are prone to inaccuracies and false-negative determinations. Annular-array transducers offer a promising approach to significantly extend DOF and to increase the depth range over which fine-lateral resolution is provided. The investigators will validate system performance using animal experiments and human-subject examinations. First, in vivo animal experiments will be conducted to evaluate a 40-MHz annular array for anterior-segment imaging and a 20-MHz annular array for posterior segment and full-globe imaging. The investigators will test the hypothesis that 20-MHz annular arrays improve detection of PVD. Validation of this hypothesis will significantly improve our ability to assess disease status in diabetic retinopathy.