Microscope in MISS

9 Microscope in MISS

Avelino Parajón, Robert Nicholas Hernandez, Sertac Kirnaz, and Andreas Korge

Summary

Modern microsurgery and minimally invasive spine surgery are no longer conceivable without a surgical microscope. After moderate beginnings starting from the Middle Ages, dramatic technical innovations from the 1950s led in many respects to the surgical microscope becoming an integral part of spinal surgery. Improvements in magnification, illumination, three-dimensional image reproduction, and intraoperative handling have led to increasing acceptance and integration of the microscope into the daily surgical workflow. Modern surgical microscopes already integrate robot-like functions and can be combined with augmented reality. Beyond clinical use, the surgical microscope also serves excellently as a training and teaching tool to train the manual skills of a surgeon outside of intraoperative use.

Keywords: surgical microscope operating microscope visualization magnification illumination spinal microsurgery optics

9.1 Introduction

By definition, microsurgery is performed with the assistance of a surgical microscope. In doing so, the microscope allows surgeons to perform operations through small skin incisions and narrow surgical corridors, with the great advantages and some difficulties due to the narrow surgical corridors. In minimally invasive spine surgery (MISS), the use of the microscope is essential. The use of modern surgical microscopes can save time in surgery, improve the surgical precision and efficiency, facilitate teaching and education, and ergonomically can even help prevent spine surgeons from developing back or neck pain.

9.2 Historical Overview

The first lens believed to have been used as a magnifying glass is the Nimrud lens, found in Nimrud, an ancient Assyrian city, around the 7th century BC.1 Archimedes in 212 BC is said to have used a burning glass against the Roman fleet which was laying siege to Syracuse. Few studies in optics are found until the 11th century, in which an Arab scholar, Ibn al-Haytham, known in the West as Alhazen, wrote the “Book of Optics” describing the optical principles and anatomy of the eye.² In the 13th century, Roger Bacon, an English friar, published the scientific principles of corrective lenses. In 14th century Italy, Friars Giordano da Rivalto and Alessandro della Spina each chronicled or spoke about meeting a man who created the first spectacles. In the 16th century, the most famous spectacle makers in the Netherlands were Zacharias Janssen and Hans Lippershey, who were two of the firsts to invent telescopes by placing two lenses within a sliding tube.³ In the 17th century in Italy, Galileo Galilei described his “tubum opticum” composed of two lenses, one concave and one convex so that the final image was not inverted. In the same century, Johannes Kepler, a German astronomer, created a telescope composed of two convex lenses so that the final image was inverted but allowed for a much wider field of view than Galileo’s telescope.³^,⁴ Coincident with the development of the telescope, the microscope was also being invented by the same visionaries: Janssen and Lippershey in the Netherlands and Galileo in Italy who described “the occhialino,” translated as “the little eye.” The term “microscope” was coined by Giovanni Faber who used the term to describe Galileo’s compound microscope submitted to the Accademia dei Lincei in 1625. In 1660, Robert Hooke used three lenses to achieve higher magnification, and the first binocular telescope was described by Chérubin d’Orléans in 1671 in his book La dioptrique oculare. The main disadvantages of early microscopes were blurry images and spherical aberrations. Additionally, they became more cumbersome with each additional lens. In the late 17th century, the Dutch scientist Antonie van Leeuwenhoek developed smaller and more powerful lenses with fewer aberrations, which led to the creation of a transportable, simple microscope. In the late 18th century, Chester Moore Hall managed to overcome chromatic aberrations by inventing the achromatic lens by placing concave and convex lens together.⁵ In 1830, Joseph Jackson Lister, the father of the famous surgeon Joseph Lister, overcame the spherical aberrations by placing a combination of flint glass lenses with crown glass lenses at specific distances. Lister also addressed the problem of vibrations from handheld use by making stands for microscopes, in association with James Smith.³^,⁶ In 1847, Carl Zeiss produced his first microscope in Jena, Germany. He hired Ernst Karl Abbe, professor of physics at University of Jena, as director of his research center. Abbe made tremendous advancements in the field of microscopy including the invention of the Abbe condenser used for illumination and the development of two critical equations, the Abbe sine condition and the resolution limit of the microscope. Abbe also made great developments in increasing the power of lenses by immersion into oil and later into monobromonaphthalene.⁷ Zeiss and Abbe later partnered with Friedrich Otto Schott, who had developed a lithium-based glass. Together they introduced the apochromatic lens, which had improved correction of chromatic and spherical aberrations than the achromatic lens.⁷^,⁸ With Abbe’s discoveries and equations, the optical qualities of lenses could be calculated and standardized, allowing for the mass production of quality microscopes.

In 1952, Hans Littmann, a physicist working at Zeiss, invented a microscope capable of changing magnification without changing focal length. In 1953, Zeiss made the Zeiss OPMI 1 (Zeiss Operating Microscope 1), a microscope mounted on a stand equipped with a rotating arm and with superior coaxial lighting than other microscopes at the time (Fig. 9.1). Further modifications and improvements were made by users like the Barraquer family, a family of Spanish ophthalmologists who made several contributions to the development of modern microscopes, and Leonard Malis and Gazi Yasargil, who introduced the idea of adjustable multiaxis counterweights with electromagnetic brakes.⁵^,⁷^,⁹

Fig. 9.1 Photographs of Hans Littmann (left) and the OPMI 1 Zeiss microscope (right). (Reproduced with permission from American Journal of Otolaryngology, 21(6), The History of the Microscope for Use in Ear Surgery, 880-883, Copyright Elsevier, 2000.)

The first clinical use of the microscope dates back to the 17th century when Petrus Borellus described the first use of the microscope in medicine, and Athanasius Kircher used a microscope to examine the blood of individuals affected by the plague. The first depicted use of a microscope in clinical practice was Giuseppe Campani’s optical viewing system used for the examination of wound in leg.10 In the 20th century, otolaryngologists were the first to use microscopes in the operating room. A monocular microscope was designed and built by Carl-Olof Nylén in 1921, an otologist from the Stockholm Clinic, and used to treat a patient suffering from chronic otitis media (Fig. 9.2). In 1922, Gunnar Holmgren, Nylén’s chief, attached a light source to a microscope and created the first binocular surgical microscope, which overcame the lack of depth perception noticed in the monocular microscope¹¹^,¹² (Fig. 9.3). Theodore Kurze became the first neurosurgeon to use the surgical microscope in 1957, and in 1958, R.M.P. Donaghy founded the world’s first microsurgery research and training laboratory in Burlington, Vermont, USA.¹³ By the mid-1960s the microscope was used in intracranial vascular neurosurgery. In the late 1970s, it was introduced to spine surgery by Caspar, Yasargil, and Williams who published it in different papers.¹⁴^,¹⁵^,¹⁶

Fig. 9.2 Photographs of Carl-Olof Nylén (left) and his first monocular microscope (right). (Reproduced with permission from American Journal of Otolaryngology, 21(6), The History of the Microscope for Use in Ear Surgery, 880-883, Copyright Elsevier, 2000.)

Fig. 9.3 Photographs of Gunnar Holmgren (left) and his first binocular microscope (right). (Reproduced with permission from American Journal of Otolaryngology, 21(6), The History of the Microscope for Use in Ear Surgery, 880-883, Copyright Elsevier, 2000.)

9.3 Advantages of Using the Microscope in MISS

The main advantages of using a microscope in spine surgery, and particularly in MISS, can be summarized as follows 17^,¹⁸ (Table 9.1):

a)Magnification: Without any magnification, the resolution (distance at which two objects can be distinguished as separate) of the human eye is 0.2 mm. The operating microscope can decrease this distance to 0.006 mm (Table 9.2) (Fig. 9.4). Magnification also results in improved accuracy and precision, as both are limited not only by the hands but also by the eyes. Without magnification, a surgeon can make instrument movements 1 to 2 mm at a time. At 20-times magnification, a surgeon may be capable of refining his or her movements to 1 to 20 microns.

b)Illumination: This is essential for visualization of deep structures. The microscope illuminates with parallel light in addition to coaxial light, which provides better visualization and less burden on the surgeon’s eyes.

c)Coaxial lighting: It allows for unobstructed, shadow-free illumination of the operating field.

d)Three-dimensional image: The binocular microscope allows the surgeon to view the operative anatomy as a three-dimensional image, including depth perception.

e)Provides ergonomic workflow: A microscope allows the surgeon to operate while looking straight ahead without having to bend forward (causing lower back pain) or to look down (causing neck pain). The prevalence rates of neck and back pain in spine surgeons are 59.4 and 62.2%, respectively¹⁹ (Fig. 9.4).

f)Co-observation by the assistant: It allows the observer to participate and assist the primary surgeon. Additionally, this allows the surgeon to teach and observe trainees.

g)Documentation: Surgeons can take photographs or videos intraoperatively to be used for educational, research, or legal purposes.

h)Fluorescence imaging techniques: The magnification and illumination allow the surgeon to perform operations through small skin incisions and access corridors (keyhole surgery), a key concept of MISS.