What is the role of non-contact viewing systems vs. contact lens viewing systems in MIVS?

Contact lens is preferred

Steve Charles

Non-contact viewing decreases axial (depth) and lateral resolution and, unlike contact-based viewing, does not compensate for pre-existing corneal asphericity (previous RK, LRI, cataract surgery, LASIK and PRK, as well as keratoconus and forme fruste keratoconus). Non-contact wide-angle viewing provides 10° less field of view than contact-based wide-angle viewing. In addition, non-contact wide-angle viewing of the periphery requires much greater ocular rotation; this increases instrument flex, which is especially a concern when using 25-gauge instruments.

Viewing systems should be considered in conjunction with illumination. Decreased axial and lateral resolution and the use of chandelier illumination, which also reduces the surgeon’s ability to identify clear vitreous, ILM and transparent epiretinal membranes, are likely a driving force behind the adoption of stains that are toxic to the retina, even more so in the case of retinal tears or macular holes when the underlying retinal pigment epithelium is exposed. These adjuvants should be unnecessary for experienced surgeons using proper viewing and illumination systems.

I recommend a flat (plano), non-sutured contact lens for macular surgery and traction retinal detachments, and contact-based (Volk or AVI) wide-angle viewing for rhegmatogenous retinal detachments, PVR and giant breaks. When used in conjunction with endoillumination, which can be both repositioned (unlike chandelier) and adjusted in intensity to reduce the potential for phototoxicity, contact-based viewing systems provide ideal viewing conditions for surgical maneuvers while lowering the potential to harm the retina.

Wide-angle non-contact viewing systems and chandelier illumination are sometimes preferred because they help improve the resolution on cameras used to make surgical videos. However, the point of surgery is not to make videos, but to achieve the best visual outcome, which means using a viewing system that provides optimal visualization and illumination that yields the lowest risk of phototoxicity.

Steve Charles, MD, is a clinical professor at the University of Tennessee, an adjunct professor at Columbia College of Physicians and Surgeons and Chinese University of Hong Kong, and the founder of the Charles Retina Institute in Memphis, Tenn.

Non-contact offers surgical advantages

Timothy W. Olsen

Since the mid-1990s, the non-contact system has been the wide-angle system of choice for many retina specialists. The non-contact system has several key advantages.

First, the non-contact system is simple with a large viewing angle of up to 130°. A long-lasting topical lubricant neutralizes corneal aberrations. There is no other lens or instrumentation to interfere with the globe during surgery. The smaller objective lens is ideal for manipulating the wide-angle view in a pediatric eyes.

Second, the resolution is excellent. The view is more than adequate to peel complex peripheral membranes, create extensive retinotomies in PVR surgery or even peel obvious membranes in the macular region. When one views a wide-angle contact system, there is improved clarity from complete neutralization of the corneal aberrations. However, this small differential in image clarity does not make up for the added manipulation and interference of the contact.

Third, non-contact systems work well in MIVS. The 23-gauge instruments and the newer 25-gauge instruments provide more than adequate “stiffness” for globe mobility and sufficient to see well into the far periphery. The other technology that improves the advantage of the non-contact system is the chandelier-style illumination systems. These systems permit bimanual dissection procedures that can be performed in the far periphery often with minimal or no scleral depression.

Because there is a compromise in the stereoscopic image under higher magnification, detailed macular peels, such as ILM peeling, should not be performed using a wide-angle non-contact system. I use a sew-on style plano lens, which provides a crystal clear view of the macula. I have not yet found a non-sutured lens that gives similar resolution. My preference is to peel ILM with a “dusting” of triamcinolone.

Timothy W. Olsen, MD, is an OSN Retina/Vitreous Board Member and F. Phinizy Calhoun Sr. Professor and Chairman, Emory Eye Center, Emory University, Atlanta.