John Vukich, MD, who is in practice in Wauwatosa, Wisconsin, was one of the primary investigators for SMILE and VisuMax and has a long history of performing LASIK. “In my previous refractive surgery practice, we were considering SMILE to be a premium procedure, so we were charging slightly more for it,” he says. “We believe that SMILE and LASIK aren’t completely equivalent and, physiologically, SMILE may have some advantage over LASIK, the more traditional option. SMILE is the newer technology, has a very good safety profile, and preserves a greater amount of integrity of the structure of the cornea.”

Microscope and objectives are complex optical systems with many uses. They are no longer used solely for biological setups (e.g. looking at cheek cells in an introductory biology class); rather, they can be used to study the emission wavelength of a flourophore, to analyze a 5μm defect on a machined part, to oversee the ablation of material off a base, and within a host of other applications in the optics, imaging, and photonics industries. Understanding the importance of each constituent part of a microscope and their specifications enables any user to choose the best system and achieve the best results.

With darkfield illumination, direct rays of light are not sent into the objective but instead strike the object at an oblique angle. It is important to keep in mind that these rays still illuminate the object in the object plane. The resultant darkfield illumination image produces high-contrast between the transparent object and the light source. When used in a microscopy setup, darkfield illumination produces a light source that forms an inverted cone of light blocking the central rays of light but still allowing the oblique rays to light the object. Figure 3 illustrates a sample darkfield illumination setup where the hollow cone of light is the numerical aperture of the objective. By comparison, no rays are blocked in a brightfield illumination setup. The design of darkfield illumination forces the light to illuminate the object under inspection, but not to enter the optical system, making it better for a transparent object.

SMILE was first approved in the United States for spherical myopia. A second approval for the treatment of compound myopic astigmatism came in 2018. With the second approval, surgeons were finally allowed to make adjustments to the energy levels. “The Zeiss clinical care specialist, in concert with the surgeon, carefully adjusts the energy levels to the point where the surgeon can still achieve easy lenticule dissection, but where they’re not seeing much of the opaque bubble layer,” explains Dr. Manche. “Lower energy levels can provide significantly better uncorrected visual acuity from postop day one. With the lower energy settings, we’re now seeing patients who are 20/20 or 20/25 on day one. We even see an occasional patient at 20/15 or better. The postoperative day one vision is still not quite as good as with LASIK, but it’s significantly better than what we saw in the early approval with our standard, fixed, higher treatment energy levels.”

Base, The base is the foundation on which the microscope stand is built. It is important that the base is relatively large, stable, and massive. When you ...

A microscope is an optical device used to image an object onto the human eye or a video device. The earliest microscopes, consisting of two elements, simply produced a larger image of an object under inspection than what the human eye could observe. The design has evolved over the microscope's history to now incorporate multiple lenses, filters, polarizers, beamsplitters, sensors, illumination sources, and a host of other components. To understand these complex optical devices, consider a microscope's components, key concepts and specifications, and applications.

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Condensermicroscope function

Many microscopes utilize backlight illumination compared to traditional direct light illumination because the latter usually over-saturates the object under inspection. A specific type of backlight illumination used in microscopy applications is Koehler illumination. In Koehler illumination, incident light from an illumination source, such as a light bulb, floods the object under inspection with light from behind (Figure 2). It employs two convex lenses: the collector lens and the condenser lens. It is designed to provide bright and even illumination on the object plane and on the image plane where the image produced from the objective is then reimaged through the eyepiece. This is important because it ensures the user is not imaging the filament of the light bulb. Since backlight illumination floods the object with light from behind, it is also referred to as brightfield illumination.

In an infinite conjugate, or infinity corrected, optical design, light from a source placed at infinity is focused down to a small spot. In an objective, the spot is the object under inspection and infinity points toward the eyepiece, or sensor if using a camera (Figure 12). This type of modern design utilizes an additional tube lens between the object and eyepiece in order to produce an image. Though this design is much more complicated than its finite conjugate counterpart, it allows for the introduction of optical components such as filters, polarizers, and beamsplitters into the optical path. As a result, additional image analysis and extrapolation can be performed in complex systems. For example, adding a filter between the objective and the tube lens allows one to view specific wavelengths of light or to block unwanted wavelengths that would otherwise interfere with the setup. Fluorescence microscopy applications utilize this type of design. Another benefit of using an infinite conjugate design is the ability to vary magnification according to specific application needs. Since the objective magnification is the ratio of the tube lens focal length $ ( \small{f_{\small{\text{Tube Lens}}}} ) $ to the objective focal length $ (\small{f_{\small{\text{Objective}}}} ) $ (Equation 5), increasing or decreasing the tube lens focal length changes the objective magnification. Typically, the tube lens is an achromatic lens with a focal length of 200mm, but other focal lengths can be substituted as well, thereby customizing a microscope system's total magnification. If an objective is infinite conjugate, there will be an infinity symbol located on the body of the objective.

A compound microscope is one that contains multiple lens elements. It works similar to a simple magnifier which utilizes a single lens to magnify a small object in order for the human eye to discern its details. With a simple magnifier, the object is placed within the focal length of the single lens. This produces a magnified, virtual image. With a microscope, a relay lens system replaces the single lens; an objective and an eyepiece work in tandem to project the image of the object onto the eye, or a sensor – depending upon the application. There are two parts to a microscope that increase the overall system magnification: the objective and the eyepiece. The objective, located closest to the object, relays a real image of the object to the eyepiece. This part of the microscope is needed to produce the base magnification. The eyepiece, located closest to the eye or sensor, projects and magnifies this real image and yields a virtual image of the object. Eyepieces typically produce an additional 10X magnification, but this can vary from 1X – 30X. Figure 1 illustrates the components of a compound microscope. Additionally, Equation 1 demonstrates how to calculate the overall system magnification. In Equation 1, m is magnification.

Objectives allow microscopes to provide magnified, real images and are, perhaps, the most complex component in a microscope system because of their multi-element design. Objectives are available with magnifications ranging from 2X – 200X. They are classified into two main categories: the traditional refractive type and reflective. Each category is further divided into types: finite conjugate and infinite conjugate (infinity corrected). In order to choose the correct objective, it is important to know the benefits of one category and type from another.

Function ofarm inmicroscope

In order to understand how the components of a microscope can be integrated with various optical, imaging, and photonics products, consider the following optical microscopy applications: fluorescence microscopy and laser ablation. Each utilizes its own unique setup in order to work with components from a microscope.

Plan, also known as planar, semi-plan, semi-planar, or microplan, objectives correct for field curvature. Field curvature is a type of aberration present when the off-axis image cannot be brought to focus in a flat image plane, resulting in a blurred image as it deviates from the optical axis. Figure 10 illustrates field flatness measured radially from the center in achromatic, semi-plan, and plan objective designs. Achromatic objectives have a flat field in the center 65% of the image. Plan objectives correct best overall and display better than 90% of the field flat and in focus. Semi-plan objectives are intermediate to the other two types with 80% of the field appearing flat.

Microscopeparts and functions

Dr. Manche agrees. “In all fairness, SMILE is relatively new, and it’s really quite impressive how good the data are this early in the evolution of the procedure,” he says. “I think it’ll just get better with time.”

One of the advantages of SMILE is the smaller incision. “We’re defaulted to a 4-mm incision in the United States,” Dr. Manche explains. “In other countries, it’s even smaller. This small incision provides less transection of the nerves in the cornea, and that’s directly correlated to how denervated the cornea becomes, and also how much dry eye the patient experiences, especially in the early postoperative period. Typically, there’s less induced dry eye with SMILE compared with LASIK because LASIK requires a 270-degree circumference flap. With LASIK surgery, you’re severing all of the nerves in that area, which leads to relative denervation of the cornea. Typically, corneal reinnervation takes place over the course of six to 12 months. Another advantage to SMILE is that there are no flap complications.”

“The quality of vision is very high for both procedures,” he adds. “Sometimes, there’s a day or two of additional recovery time for SMILE. However, there’s also always the possibility of delayed healing with LASIK, whether it be from striae or epithelial issues related to drops or other things. So, I would say the procedures are roughly equivalent in terms of acuity and patient satisfaction.”

Knowledge Center/ Application Notes/ Microscopy Application Notes/ Understanding Microscopes and Objectives

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Brightfield illumination requires a change in opacity throughout the object. Without this change, the illumination creates a dark blur around the object. The end result is an image of relative contrast between parts of the object and the light source. In most cases, unless the object is extremely transparent, the resulting image allows the user to see each part of the object with some clarity or resolution. In cases where an object's transparency makes it difficult to distinguish features using brightfield illumination, darkfield illumination can be used.

Function ofbody tube inmicroscope

DIN and JIS have historically been used when considering a classic compound microscope. Some microscope manufacturers prefer to list the tube lens length by the optical properties instead of the mechanical. For a DIN standard objective, this changes the tube lens length to 150mm because the eyepiece is imaging the intermediate image plane (Figure 8). Lastly, there is a dimension typically listed for objectives to allow the user to consistently know what length it is: the parfocal distance (PD). The parfocal distance is the distance from the flange of the objective to the object under inspection. For DIN objectives this distance is a standard 45mm and for JIS is it 36mm (Figures 8 and 9).

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Function of ocular on microscopepdf

A third type of illumination used in microscopy is epi-Illumination. Epi-illumination produces light above the objective. As a result, the objective and epi-illumination source substitute for a Koehler illumination setup. Using the objective for a large section of the illumination makes epi-illumination very compact – a major benefit of this design. Figure 4 illustrates an epi-illumination setup that is used frequently in fluorescence applications. For more information on fluorescence microscopy, view Fluorophores and Optical Filters for Fluorescence Microscopy.

Interestingly, another Chinese study found that, while SMILE is as effective as FS-LASIK in correcting high myopia, attention should be paid to the induction of vertical coma in highly myopic patients following SMILE.3

Illumination within a microscope is just as important as selecting the proper eyepiece or objective. It is crucial to choose the correct illumination in order to obtain the most conclusive results. Before deciding on the type of illumination setup to work with, consider the application setup, object under inspection, and desired results.

At the six-month visit, 96.6 percent of eyes in the SMILE group and 91.3 percent in the FS-LASIK group achieved unchanged or better best-corrected distance visual acuity. Additionally, 96.6 percent of eyes in the SMILE group and 95.7 percent in the FS-LASIK group achieved uncorrected distance visual acuity of 20/20 or better. As for wavefront aberrations, high-order aberrations and spherical aberrations increased significantly after surgery in both groups relative to preoperative values, and vertical coma increased after SMILE. Other than the difference in vertical coma, there were no statistically significant differences in the changes in higher-order aberrations, spherical aberrations, horizontal coma, coma, horizontal trefoil, vertical trefoil or trefoil between the two groups.

When viewing fluid materials such as bacteria, cell cultures, blood, etc, it is necessary to use a coverslip in order to protect the object under inspection and microscope components from contamination. A coverslip, or glass microscope slide, changes the way light refracts from the object into the objective. As a result, the objective needs to make proper optical corrections to produce the best quality image. This is why objectives denote a range of coverslip thicknesses for which they are optimized. Typically, this is listed after the infinity symbol (which denotes that an objective is an infinite conjugate, or infinity corrected design) and ranges from zero (no coverslip correction) to 0.17mm.

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The Numerical Aperture (NA) of an objective is a function of the focal length and the entrance pupil diameter. Large NA objectives sometimes require the use of immersion oils between the object under inspection and the front of the objective. This is because the highest NA that can be achieved within air is an NA of 1 (corresponding to 90° angle of light). To get a larger angle and increase the amount of light entering the objective (Equation 2), it is necessary to use immersion oil (index of refraction typically = 1.5) to change the refractive index between the object and the objective. High NA objectives in conjunction with immersion oil are a simple alternative to changing objectives, a move that may be costly.

Function ofnosepiece inmicroscope

According to Dr. Vukich, SMILE is another step in the evolution of corneal recontouring as it relates to a refractive outcome. “We have data to support that the intrastromal removal of tissue versus the creation of a cap leaves intact a greater percentage of the corneal strength and integrity, and we believe that to be an advantage in the long run,” he says. “Many patients seeking refractive surgery are in their 20s and 30s, and they’re making decisions with the understanding that they will need to have healthy eyes and good vision for maybe another 70 years. All things being equal, a greater percentage of retained corneal structural integrity is a tiebreaker for many people.”

At the five-year follow-up, all eyes in both groups were within 1 D of attempted spherical equivalent refraction, and no statistically significant difference was found between the intended and achieved correction comparing the groups at any time points.

Postoperative spherical equivalent refraction was -0.20 ±0.25 D in the SMILE eyes and -0.03 ± 0.20 D in the LASIK eyes, and the posterior corneal curvature was unchanged after both procedures. The measured corneal thickness was reduced by 137.40 ±15.01 µm in the SMILE eyes and by 155.06 ±17.43 µm in the LASIK eyes. The change in the SE was -0.01 ±0.26 D in the SMILE eyes and -0.13 ± 0.30 D in the LASIK eyes after one week. Only the peak distance (the distance between the highest points of the nondeformed corneal parts) differed between the groups; the distance was 1.06 ±1.44 mm in the SMILE eyes and -0.26 ±1.16 mm in the LASIK eyes. The SMILE eyes had smaller changes in higher-order aberrations and spherical aberration than the LASIK eyes.

2. Yang X, Liu Q, Liu F, Xu J, Xie Y. Comparison of outcome between small incision lenticule extraction and FS-LASIK in eyes having refractive error greater than negative 10 diopters. J Cataract Refract Surg 2020;46:1:63-71.

Function ofstage inmicroscope

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According to Dr. Manche, one of the advantages of LASIK is that it’s been around a long time, with tens of millions of procedures having been performed. “It’s a very well-known and mature technology,” he says. “SMILE was approved in the United States in 2016, and about 3 million cases have been performed worldwide.”

Another advantage of LASIK is that it’s easy to do a touch-up. Surgeons can lift the flap and perform a retreatment. “In comparison, surgeons cannot perform a repeat SMILE surgery on an eye that’s already had SMILE,” notes Dr. Manche. “If an eye that has previously had SMILE requires an enhancement procedure, you are left with a couple of options. You can perform LASIK surgery by cutting a flap in the SMILE cap. In the United States, the SMILE cap thickness is defaulted at 120 µm, so you then have to cut a LASIK flap at either 90 µm or 95 µm, which only gives you about 25 to 30 µm of play between the cap cut and the flap cut. Some surgeons aren’t comfortable with that. Another choice is to perform a side cut and open up the original 120-µm SMILE cap and convert that into a LASIK flap. A final choice is to perform PRK surgery on top of the SMILE cap. I don’t like to cut a LASIK flap 25 to 30 µm away from the SMILE cap interface, so I perform PRK touch-ups for all of my SMILE enhancements.”

Reflective objectives utilize a reflective, or mirror-based design. They are often overlooked in comparison to their refractive counterparts, though they can correct for many issues present in the latter. Reflective objectives consist of a primary and secondary mirror system (Figure 6) to magnify and relay the image of the object under inspection. Edmund Optics® utilizes the popular Schwarzschild design, though other designs are available. Since light is reflected by metallic surfaces and not refracted by glass surfaces, reflective objectives do not suffer from the same aberrations as refractive objectives and, thus, do not need the additional designs to compensate for these aberrations. Reflective objectives can produce higher light efficiency as well as better resolving power for fine detail imaging because the system is primarily dependent upon the mirror coating instead of upon the glass substrate being used. Another benefit of reflective objectives is the possibility of working deeper into either the ultra-violet (UV) or infrared (IR) spectral regions due to the use of mirrors compared to conventional refractive optics.

3. Yang W, Liu S, Li M, Shen Y, Zhou X. Visual outcomes after small incision lenticule extraction and femtosecond laser-assisted LASIK for high myopia. Ophthamic Res 2020;63:4:427-433.

When microscopes were first invented, eyepieces played a major role in their design since they were the only means to actually see the object under inspection. Today, analog or digital cameras are used to project an image of the object onto a monitor or a screen. Microscope eyepieces generally consist of a field lens and an eye lens, though multiple designs exist that each creates a larger field of view (FOV) than a single element design. For a simple guide on selecting the right design, view Choosing the Correct Eyepiece.

Field of view or FOV is the area of the object that is imaged by a microscope system. The size of the FOV is determined by the objective magnification. When using an eyepiece-objective system, the FOV from the objective is magnified by the eyepiece for viewing. In a camera-objective system, that FOV is relayed onto a camera sensor. The sensor on a camera is rectangular and therefore can only image a portion of the full circular FOV from the objective. In contrast, the retina in your eye can image a circular area and captures the full FOV. This is why the FOV produced by a camera-microscope system is typically slightly smaller than that of an eyepiece-microscope system. Equations 3 and 4 can be used to calculate the FOV in the aforementioned systems. In Equations 3 and 4, $ \small{H_{\small{\text{Camera Sensor}}}} $ is the sensor size of the camera and $ \small{H_{\small{\text{Eyepiece Field Stop}}}} $ is the field stop of the eyepiece.

For example, a retrospective case series from Turkey found that SMILE and FS-LASIK were safe and similar in terms of efficacy and predictability at five-year follow-up for the correction of myopia and myopic astigmatism.1 The study included 44 eyes from 22 patients who received SMILE in one eye and FS-LASIK in the contralateral eye. Patients were examined at one, three and five years.

Dr. Vukich says he’s encountered patients who have done research and have come to the conclusion that SMILE was a better procedure for them. “You try to be even-handed,” he says. “The majority of our cases remained LASIK, however. When given the choice, some of the decision was driven by the price differential, some of it was driven by familiarity and some of it was driven by just the potential longevity of exposure to LASIK.

Additionally, studies have shown that, compared to LASIK, SMILE provides potentially better biomechanical stability of the cornea. “Some very good work has shown that the anterior lamellar tissue in the cornea is the strongest,” Dr. Manche says. “SMILE spares the anterior corneal lamellar tissue. The side incision with SMILE is only 4 mm compared to the 20-mm incision with LASIK. There’s significantly more transection of the corneal lamellae with LASIK compared to SMILE. Preservation of the anterior stromal tissue results in a reduced biomechanical insult to the cornea with SMILE, and that could have implications with regard to lowering the risk of ectasia.”

1. Aygun BT, Cankaya KI, Agca A, et al. Five-year outcomes of small-incision lenticule extraction vs femtosecond laser-assisted laser in situ keratomileusis: A contralateral eye study. J Cataract Refract Surg 2020;46:3:403-409.

The quality of an objective and eyepiece determine how well the system performs. In addition to choosing the magnification and complexity of the design, understanding correct quality correction is extremely important when deciding on the type of objective to use. Quality correction (i.e. achromatic, apochromatic, plan, semi-plan) is denoted on the objective itself to allow the user to easily see the design of the objective in question. There are typically two levels of chromatic aberration correction: achromatic and apochromatic. Achromatic objectives are among the simplest and least expensive of objectives. They are designed to correct for chromatic aberration in the red and blue wavelengths, in addition to being corrected for spherical aberration in a green wavelength. Limited correction for chromatic aberration and lack of a flat FOV reduce objective performance. Apochromatic objectives, by contrast, provide higher precision and are chromatically corrected for red, blue, and yellow. They also provide spherical aberration correction for a broad spectral range and generally have a long working distance given the extremely high numerical apertures (NA) that this optical design offers. Apochromatic objectives are ideal for white light applications, whereas achromatic objectives are best suited for monochromatic. Both objective designs, however, suffer significantly from distortion and field curvature, which worsen as objective magnification increases. Therefore, it is always important to focus on the complete system performance, rather than just objective performance alone.

In a finite conjugate optical design, light from a source (not at infinity) is focused down to a spot (Figure 11). In the case of a microscope, the image of the object under inspection is magnified and projected onto the eyepiece, or sensor if using a camera. The particular distance through the system is characterized by either the DIN or JIS standard; all finite conjugate microscopes are either one of these two standards. These types of objectives account for the majority of basic microscopes. Finite conjugate designs are used in applications where cost and ease of design are major concerns.

A fluorophore (or fluorescent dye) is used to mark proteins, tissues, and cells for examination or study. Fluorophores can absorb light of one wavelength and emit (fluoresce) light of another wavelength. In a typical fluorescence microscopy setup three filters are used: an excitation filter, an emission filter and a dichroic filter. Each fluorophore has a specific absorption or excitation wavelength band, the excitation filter will transmit only that specific range of wavelengths. The fluorophore, once excited, will emit a different range of wavelengths. The emission filter transmits only the emission wavelengths. A dichroic filter that is specifically designed to reflect the emission wavelengths and transmit the excitation wavelengths is used to separate the excitation and emission channels. Figure 13 illustrates a typical fluorescence imaging setup. For additional information on fluorescence microscopy, view Fluorophores and Optical Filters for Fluorescence Microscopy.

Function of ocular on microscopequizlet

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Most microscope objective specifications are listed on the body of the objective itself: the objective design/standard, magnification, numerical aperture, working distance, lens to image distance, and cover slip thickness correction. Figure 7 shows how to read microscope objective specifications. Since the specifications are located directly on the body of the objective, it is easy to know exactly what one has, a very important fact when incorporating multiple objectives into an application. Any remaining specifications, such as focal length, FOV, and design wavelength, can easily be calculated or found in the specifications provided by the vendor or manufacturer.

Additionally, LASIK has faster visual recovery. “When SMILE was initially approved in the United States, we were using relatively high energy levels,” Dr. Manche says. “ The use of higher energy levels in SMILE surgery has been associated with significantly slower visual recovery. So, when SMILE was first released, many patients experienced  slower recovery of vision. It was common to have patients seeing 20/40 or 20/30 on postoperative day one. This is in contrast to what you see with LASIK, after which the majority of patients see 20/20 or 20/15 on day one.”

If the objective follows a simple microscope standard (such as DIN or JIS) then it is listed on the body to show what required specifications must be present within the system. Most compound microscopes employ the Deutsche Industrie Norm, or DIN, standard. The DIN standard has a 160mm distance from the objective flange to the eyepiece flange (Figure 8). The other available standard is the Japanese Industrial Standard, or JIS. The JIS standard has a 170mm distance from objective flange to eyepiece flange (Figure 9). Paying attention to these two distances is necessary when choosing the proper objective and eyepiece in order to make sure that the image projected from the former is properly imaged through the latter. Though the image distances are different for DIN and JIS, there is no difference in optical performance; they are equal in quality. Similarly, each standard utilizes the same RMS mounting thread of 0.7965" x 36TPI.

The most commonly used category of objectives is refractive. In a refractive design light passing through the system is refracted, or bent, by the optical elements. Each optical element is typically anti-reflection coated to reduce back reflections and improve overall light throughput. Refractive objectives are often used in machine vision applications that require resolution of extremely fine details. There are multiple refractive objective designs each utilizing different optical configurations. The designs can range from two elements in basic achromatic objectives (an achromatic lens and a meniscus lens) to fifteen elements in plan-apochromatic objectives (Figure 5). Plan-apochromatic objectives are the most complex, high-end objective design with chromatic and flat field correction done within the objective itself.

Eyepieces and objectives both have magnification that each contribute to the overall system magnification. Magnification is usually denoted by an X next to a numeric value. Most objectives contain a colored band around the entire circumference of the body that indicates their magnification (Figure 7). For example, a yellow band denotes a 10X magnification.

LASIK has been performed for more than 30 years with impressive results, but surgeons and patients are always on the lookout for something new and—possibly—improved. It’s with this mindset that eyes were turned toward the relative newcomer in the refractive surgery marketplace, small-incision lenticule extraction, performed with the VisuMax femtosecond laser (Carl Zeiss Meditec; Jena, Germany). Even though SMILE is in its relative infancy as a go-to refractive procedure, it’s producing results similar to advanced LASIK—but it’s not without its issues. Here, experts discuss the relative merits of the two procedures, and we also look at the results of well-performed studies of the surgeries.

For another perspective, a recent study conducted in China found that, when compared to LASIK, SMILE may offer better safety and objective visual quality, comparable stability and efficacy, but slightly inferior predictability when correcting myopia exceeding 10 D.2 This prospective, randomized, comparative study included 60 eyes in 60 patients. Thirty eyes were corrected using SMILE, and 30 were corrected using FS-LASIK. Patients received preoperative and six-month postoperative examinations.

Fluorite objectives further correct for aberrations using advanced glass types containing fluorspar or other synthetic substitutes. Just like achromatic objectives, fluorite objectives are designed to correct for chromatic aberrations for red and blue wavelengths. However, fluorite objectives are designed to correct for spherical aberration at two or three wavelengths instead of just green, typically have a higher NA, and feature a better resolving power and higher degree of contrast.

As mentioned above, outcomes of the two procedures are quite comparable. Dr. Manche just completed a randomized clinical trial of 40 patients who underwent wavefront-guided LASIK in one eye and SMILE in the fellow eye. He assessed patients at one, three, six and 12 months. “We did find slightly better outcomes with wavefront-guided LASIK compared to the SMILE surgery,” he says. “We had slightly more LASIK eyes achieve an uncorrected visual acuity of 20/20, as well as higher levels of visual acuity of 20/16 and 20/12.5. Additionally, we had greater gains of lines of best-corrected visual acuity in the wavefront-guided LASIK group compared to the SMILE group. So, on the whole, the outcomes were very similar, but there were small but measurable benefits to wavefront-guided LASIK compared to SMILE.” Dr. Manche will be presenting the results of this study at this year’s meeting of the American Society of Cataract and Refractive Surgery.

Pertinent to the article’s topic, Dr. Manche performs sponsored research for Alcon, Carl Zeiss Meditec and Johnson & Johnson Vision. He is a consultant for Johnson & Johnson Vision. Dr. Vukich has no financial interest in any of the products discussed.

At six months postoperatively, the uncorrected distance visual acuity was -0.01 ±0.06 logMAR (a little better than 20/20) in the SMILE eyes and -0.05 ± 0.10 (a little better still) in the LASIK eyes, while the corrected visual acuity was -0.07 ± 0.07 logMAR in the SMILE eyes and -0.08 ± 0.08 (a shade off of 20/16) in the LASIK eyes.

Two common uses of lasers are to (1) heat material onto a base or (2) to ablate material off of a base. Laser ablation systems require microscope components because of the precision beam manipulation (i.e. focusing, bending, scattering reduction, etc) required. A laser ablation setup typically contains custom optics, rather than off-the-shelf components, with the laser precisely designed into the system (Figure 14). The laser is oriented in an epi-illumination design to utilize the microscope objective's ability to focus light at the object plane, and to produce extremely small spot sizes with minimal aberrations. Also, an eyepiece allows the user to see where the laser is located and to make sure everything is working properly. Filters are necessary to block the laser from causing damage to the user's eye. Laser ablation setups are used in medical and biological applications because they offer higher precision than conventional surgical methods.

Frankel (GB), unsurprisingly, has been named the champion sire of France in 2022. He ceded his position as champion in Britain and Ireland to Dubawi (Ire).

This prospective, comparative study included 52 eyes of 34 consecutive highly myopic patients with spherical equivalent between -8 and -10 D. Twenty-three eyes of 16 patients underwent FS-LASIK, while 29 eyes of 18 patients underwent SMILE. Visual outcomes and wavefront aberrations were analyzed preoperatively and six months postoperatively.

... backlights, masked backlights, collimated backlights, and ... The slope from the conventional backlight has a similar profile to the collimated backlight ...

Edward Manche, MD, director of the Cornea and Refractive Surgery Service at Stanford University School of Medicine, has been performing SMILE surgery since it was approved in 2016, so he’s familiar with the trade-offs of each. “Both LASIK and SMILE work very well,” he says. “Both provide excellent outcomes and safety, and both can be used in about 85 percent of all patients that come into a typical practice. However, SMILE isn’t yet approved for hyperopia or mixed astigmatism. In addition, in the United States, we’re limited to 3 D of astigmatism or less with SMILE. So, within those parameters, SMILE and LASIK have a pretty wide approval, and a lot of the choice in procedure comes down to patient preference.”