title: [New biconcave prism contact lens for vitreous surgery in gas-filled eyes].
abstract: OBJECTIVE
  To obtain a surgical contact lens with adequate operative field in vitreous surgery of gas-filled eyes.
  
  
  METHODS
  We designed a new biconcave prism contact lens for gas-filled eyes by improving the material and the design of the lens (prism angle, radius and area of front concave of the lens). The operative field was calculated by a simulation using the ray tracing method for cases of simultaneous phaco-vitrectomy surgery, vitrectomy of pseudophakic eyes, and vitrectomy without phaco-surgery. For this study, a prototype of the newly designed lens was made and used for vitrectomy of gas-filled eyes.
  
  
  RESULTS
  The calculated operative field was about 47 degrees (central angle) for vitrectomy of pseudophakic eyes and vitrectomy without phaco-surgery. In cases of simultaneous phaco-vitrectomy surgery, the operative field can be varied continuously from 47 to 145 degrees (central angle) by adjusting the viscoelastic material in the anterior chamber. Appropriate visual field, good binocular vision, and visibility of the peripheral region were obtained in the vitrectomy of gas-filled eyes.
  
  
  CONCLUSIONS
  The newlydesigned contact lens is useful for viewing the fundus during the vitrectomy of gas-filled eyes.
authors.affiliation: Department of Ophthalmology, Osaka Rosai Hospital, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Emi
authors.forename: Tomohito
authors.initials: T
authors.lastname: Oyagi
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Futamura
mesh_terms: D000388:Air; D003261:Contact Lenses; D005654:Fundus Oculi; D006801:Humans; D055095:Optics and Photonics; D012031:Refractometry; D012163:Retinal Detachment / Q000601:surgery; D014821:Vitrectomy / Q000379:methods*