Wide-angle viewing system.

A wide-angle viewing system offers a panoramic view of the surgical field and also improves the safety and efficacy of the vitreoretinal surgical procedure. Surgeons can easily observe the fundus in almost the whole area and evaluate the retinal pathologies through the panoramic view even in eyes with small pupils, corneal opacity, or eyes implanted with multifocal intraocular lens or toric intraocular lens. Recent wide-angle viewing systems consist of two types: contact lens and non-contact lens. The benefit of the contact lens type is better resolution and contrast of the fundus image compared to the non-contact lens type. The contact lens is directly attached to the cornea and the aberration and the reflection from the corneal surface are canceled. However, the eye position needs to be fixed and surgical procedures that rotate the eye should be avoided because incomplete attachment of the contact lens causes decreased visibility of the fundus image. The benefit of the non-contact lens type is that the viewing angle can be changed by moving the front lens up and down to adjust the distance between the cornea and the front lens. The surgical procedures are more flexible and the eye can be rotated. Dehydration of the corneal surface decreases the visibility of the fundus image and the corneal surface needs to be covered with viscoelastic material to avoid dehydration. Condensation of the front lens also decreases the visibility of fundus. Understanding the optical characteristics of the wide-angle viewing system is the key to a successful vitreoretinal surgery.