Surgical Loupes and Ophthalmic Microsurgery
Article by Dr. Tim Mauri, MD, Ph.D
Ophthalmologists are tasked with performing microsurgery on one of the smallest organs in the human body, the eye. They perform operations with incredible detail and precision. It would be essentially impossible for ophthalmologists to do their work with such accuracy if they did not rely on the variety of magnification instruments available to them. From operating microscopes to surgical flip-up loupes, the ophthalmologist uses magnification for cataract, vitreoretinal and corneal procedures, as well as for pediatric and oculoplastics procedures.
As these procedures vary greatly in the level of detail and skill needed to perform them, so does the difference in magnification between operating microscopes and surgical loupes. Microscopes are necessary for performing surgery on structures of less than one or two millimeters wide. Operating microscopes can provide up to 40 times magnification. Quality surgical loupes, however, can provide magnification of up to six or eight times. Such magnification is sufficient to complete most of the procedures. Mobility and size make them more versatile, less expensive and easier to use when compared with microscopes. Surgical loupes are well-suited for a wide range of surgical subspecialties and great for procedures requiring less magnification than an operating microscope.
Microscopes provide up to 40x magnification
Surgical flip –up loupes are used the most among ophthalmologists. There are several key factors to be taken into consideration when purchasing surgical loupes. Perhaps the most important factor is the surgical loupe’s resolution. It is the most important factor in assessing the overall quality of surgical loupes. Resolution is the device’s capacity to distinguish small structures from each other. Resolution can vary greatly among different brands of surgical loupes. Some surgical loupes may have good resolution across a central portion of the visual field only, but not the perimeter. Such design makes images appear distorted at the edges on the picture. Quality surgical flip-up loupes will have excellent resolution across all of the visual field with edge to edge clarity. Images with quality loupes appear very flat and easy to view. In addition, superior magnification loupes are made with Apochromatic lenses, such as Precision SCOPE (Portland, ME, USA), that are known to eliminate visual distortion,.
Another important factor in determining the quality of surgical loupes is the width of the loupe field. The width of the field is how large the area of focus is in the field of view. Ophthalmologists often prefer surgical loupes with a large field width, allowing them to keep their instruments in perspective at all times, and thereby simulating the normal wide visual field of the naked eye and reducing eye fatigue. Width of field is partially determined by the quality and design of the surgical loupes, but more so it depends on the level of magnification the loupes offer. A stronger power lens will have a smaller field width than a lower power lens. It is best to try on surgical loupes with different magnification powers to find the best width of field. Generally, ophthalmic surgeons prefer surgical loupes with a magnification between 2.5X and 4X. However, two surgeons performing the same procedure may prefer surgical loupes with entirely different magnification powers. Different manufacturers also use different explanations of magnification. As there is no true standard to measure magnification, differences in magnification up to 10 or 15 percent among similar surgical loupes is not uncommon.
Precision SCOPE offers loupes with improved working angle, visibility and lighter weight without obtrusive hinges.
A surgical loupe’s depth of field is also very important in how they perform for the ophthalmologist. The field depth relates to the loupe’s capacity to focus across a given distance. A long field depth will allow the surgeon to focus over a long range in the surgical field. Conversely, a short field depth restricts the surgeon to a narrow range.
The working angle, or optical declination angle, is another factor the user needs to consider. This is the angle at which a surgeon lowers his or her eyes in order to reach the optimal working position through the surgical loupes. Flip-up loupes offer different working angles due to their design. This is the main reason why surgeons prefer the flip-up loupes over the TTL loupes that have the loupe build into the lens. Shallow working angles can lead to poor neck health and muscle strain, so this should be an important consideration in finding quality surgical loupes. By trying on several pairs of loupes, an ophthalmologist can find the pair perfectly suited to perform a wider variety of procedures without strain.