Ever since 1677, when Descartes first observed the ability of the human eye to focus on objects at different distances in a visual field, this mechanism has fascinated and eluded physiologists and optical physicists. The initial treatment of patients with presbyopia was simple magnifiers that compensated for the declining accommodation that accompanied presbyopia. The first major breakthrough was Benjamin Franklin's invention of the bifocal spectacles. These spectacles were the only treatment available until bifocal contact lenses and the monovision technique were developed to more successfully treat patients with presbyopia.
Currently, 2 modalities are available for treating presbyopia. One modality involves simply compensating for presbyopia and not truly treating it. The other modality involves surgically treating/reversing presbyopia and is discussed in this article. [1, 2, 3, 4]
The compensatory approach to treating patients with presbyopia involves either the monovision technique or a multifocal lens technique.  The monovision technique of treating patients with presbyopia involves sacrificing one eye for distance to see clearly at near. Although successful, some limited decrease in stereopsis occurs.
The multifocal approach can be accomplished through various methods, including corneal surgery, lenticular surgery, or contact lenses. Attempts at creating a multifocal cornea have not been very successful because of the lack of predictability. Lenticular surgery, in which the pseudophakic lenses are multifocal in design, has been slightly more successful. The disadvantage of a multifocal intraocular lens is that any significant subluxation would markedly decrease the effect. In addition, a multifocal lens inherently decreases contrast sensitivity and has a high propensity for night glare. Early work is being performed on intracorneal lenses or intracorneal inlays; they are promising because of their greater predictability and reversibility.
Perhaps the most exciting development in this field of ophthalmology is the understanding of the pathophysiology of presbyopia. Schachar's theory of accommodation has created the most enthusiastic discussion. [6, 7, 8, 9] While leaving this battle to the theorists, simply put, the human lens grows continuously at the rate of 20 micrometers per year. This growth has little impact on lens accommodation until a person reaches an age of approximately 40 years. At this time, the space between the lens equator and the ciliary muscle has sufficiently decreased to begin lessening the pull effect of zonular changes that result in accommodation.
Presbyopia presents itself when lens growth results in a crowding of the ciliary space, thereby affecting near vision. In comprehending the above information regarding Schachar's theory of accommodation, multiple issues, including the lens and the ciliary zonules, must be considered when treating patients with presbyopia. If the lens could be stopped from growing, no progressive crowding of the ciliary space would occur, and presbyopia would not develop. If the lens could be reduced in size, presbyopia would be reversed. The ciliary zonules would also have to be modified. To reverse presbyopia, shrinking (or shortening) the ciliary zonules would be necessary; however, currently, this is not feasible. Thus far, the only successful treatment of patients with presbyopia is to expand the ciliary space by scleral expansion.
In understanding Schachar's new theory, clinicians can now approach the treatment of presbyopia, whereas inconsistencies in Helmholtz's theory prevented the proper clinical approach.  To further validate Schachar's theory, 3 completely different surgical techniques are being investigated by 3 independent groups of clinicians. All procedures rely on the expansion of the sclera to increase space between the ciliary muscle and the lens equator, thereby restoring accommodation. With the confidence that the scleral expansion theory is correct, clinicians are working toward perfecting a surgical approach to restore accommodation. 
Although originally developed by Schachar, Thornton leads the radial sclerotomy approach to accommodative restoration called anterior ciliary sclerotomy (ACS). As part of this investigation, Thornton led a multicenter study to examine the effect of scleral expansion on accommodation, and Fukasaku performed most of the work. Results from the first 2 years of this study demonstrated scleral expansion could improve the loss in accommodation that occurs in presbyopia. Because of a decreased effect after 6 months, Fukasaku began placing silicone implants within the sclerotomies and sutured them in place to prevent regression.
The second procedure under investigation involves the use of an erbium (Er) laser to form radial sclerotomies in the same manner as ACS.
The third procedure, which is currently in Phase 3 of Food and Drug Administration (FDA) clinical trials (Refocus Group), is called the scleral spacing procedure (SSP) for the surgical reversal of presbyopia (SRP). In this procedure, 4 small arched polymethylmethacrylate (PMMA) implants are tunneled through the sclera overlying the ciliary body just posterior to the lens equator. These implants result in localized increases in globe diameter over the lens equator, effectively reversing the crowding of the ciliary space due to lens growth and restoring zonule function on the crystalline lens.
In the 4 years that the author has been performing the SRP procedure, most patients have experienced increases in accommodation. Only a small percentage of patients had a relatively low gain in accommodation. (With the expanding group of surgeons who are successfully performing this procedure, only time and practice will refine the process.) The author's strongest recommendation to surgeons performing their initial SRP procedures is to execute them exactly as proposed.
After the first case, the author believed slight changes might improve the surgical procedure. However, until fully familiar with the procedure, surgeons should refrain from making any changes. For this reason, in follow-up visits with the first 3 patients, the author adhered to standard protocol. Changes were made only after the author became familiar with the specific needs of the procedure. Surgeons would be doing a disservice to both themselves and their patients in making any changes in this procedure prematurely. Small changes to this procedure should be attempted only after surgeons have completed their first 5-10 cases. The author cannot emphasize enough the importance of following the SRP protocol for the surgical technique. Variations of this technique have been attempted, with some successes and some failures. Attention to fine detail is an essential aspect of the SRP procedure.
To help surgeons, the finer points of performing the SRP procedure are addressed in this article. The learning curve is reduced because this technique involves the placement of 4 implants at oblique quadrants and each implant is placed using the exact same technique. Therefore, the learning curve of this surgical procedure is essentially 4-8 times shorter than the learning curves for other surgical procedures, such as phacoemulsification or laser in situ keratomileusis (LASIK). With phacoemulsification or LASIK, upon completion of 50 cases, most surgeons are comfortable with the particular procedure and see a significant improvement in their outcomes.  In teaching the SRP procedure to more than 30 surgeons, the author has found that surgeons reach this same comfort level after approximately 5-10 monocular cases.
This procedure is surgically challenging. The author's goal with this article is to make the procedure as patient friendly as possible. Surgeons must attain a high level of surgical skill and pay attention to detail. Achieving these goals results in less tissue trauma, increased patient comfort, and better outcomes. 
As an experienced surgeon in cataract and refractive procedures, the author recognizes the need for skilled and dexterous surgeons when performing the SRP procedure using the PresVIEW™ scleral implant (PSI). The most successful skills transfer technique is a good didactic introduction followed by a wet lab. This training is culminated with a personalized mentoring process. During this process, the author performs the SRP procedure, assisted by the learning physician; then, the new surgeon immediately performs the first case, assisted by the author. This enables a transfer of surgical knowledge and skills under real-time situations, within an excellent learning environment, while ensuring the patient's well-being.
After observing this procedure performed by Jose De La Garza, MD, in Monterrey, Mexico, in January 1998, with its impressive outcome, the author was convinced that this procedure had significant potential. The author understood the importance of correcting presbyopia. With the baby boomer population having entered the fourth decade of life, 1 person becomes presbyopic every 7 seconds. The author realized that numerous patients could potentially undergo this procedure, while not enough eye surgeons in the country would be available to adequately supply their needs for SRP. This realization motivated the author to further study the treatment of presbyopia.
The author's first patient was a 48-year-old female, with a small amount of myopia. The procedure was performed in Puerto Vallarta, Mexico, at the Ameri+MED Hospital. (Other than the FDA trials, these procedures must be performed outside of the United States. To date, the FDA has reviewed the Phase 1 and 2 clinical trial results and has authorized the sponsor, Refocus Group, to proceed with Phase 3, which is currently underway.) SRP was performed on the patient's dominant eye per the recommended protocol at the time. To further enhance accommodation, the patient elected to treat the second eye approximately 1.5 years after the first surgery. After more than 4 years, this patient continues to benefit from the increased accommodation.
As with most surgical procedures, preparation holds equal importance to the actual surgical technique and the postoperative care. Each patient initially undergoes a preoperative evaluation. The ideal candidate is aged 40-70 years with minimal refractive error. If patients require refractive surgery, their distance vision is typically corrected first, followed approximately 4-6 months later by the SRP procedure. The author has performed the SRP procedure both before LASIK and after LASIK; however, performing LASIK first is preferred. If the SRP procedure is performed first, the elevation of the sclera by the implant may cause difficulty in maintaining suction with the microkeratome during the LASIK procedure.
Patients who are more than +1.00 diopters (D) hyperopic may not attain enough accommodation to satisfy their particular near vision needs. Depending on the expectations of the patient, this may or may not be satisfactory. Since the procedure is performed with the intention of providing as much accommodation as is physiologically possible, the variability lies within both the patient's own anatomy and the surgeon's skill.
The author performed this procedure on a 71-year-old male, in good physical condition, who was a +1.25 D hyperope. As part of a thorough informed consent, this patient was told that this procedure had been performed on a 70-year-old patient without success. It was also explained to the patient that because of his farsightedness, he might not gain enough accommodation to completely stop using his reading glasses. Knowing this information, the patient still wanted to proceed with the surgery. The SRP procedure using PSIs was performed on the patient's dominant eye. Subsequently, he was able to drive without glasses because of improvement in his distance vision to 20/40. This patient still requires glasses to read the newspaper. However, since this patient is retired and enjoys golf, he is thoroughly satisfied.
As evident by the above example, a thorough informed consent is important and imperative. As long as the patient is aware of the potential outcomes, the surgeon should feel confident in being able to meet the patient's expectations. The probability of successful outcomes continues to increase with more of these procedures being performed and studied around the world. In addition, with the introduction of the PresVIEW™ System automated sclerotome, a reduction in the variability of surgeon technique has also been achieved. As a result of the new automated system, it has been the author's experience that clinical outcomes have become more predictable. To date, the author has performed surgery on nearly 200 eyes, and over 75 of these surgeries have been completed using the new automated sclerotome.
Surgical treatment of presbyopia
SRP may be considered an optional, cosmetic procedure with the same inherent issues. Therefore, this procedure may not be ideal for all persons. Patients must be aware of the need to exercise and work at strengthening the ciliary muscle for several months after the procedure to gain optimal effects. The patient's eyes will be quite red for a few weeks following the SRP surgery. Postoperative expectations given prior to the procedure are extremely important.
When obtaining the patient's history, note the following contraindications:
Insulin-dependent diabetes mellitus
Chronic or recurrent uveitis or other recurrent anterior or posterior segment inflammation
Previous eye surgery (eg, cataract, corneal transplant, glaucoma filtering surgeries, retinal detachment repair)
Patients on anticoagulant therapy (eg, heparin, warfarin)
Chronic systemic disease (eg, subacute lupus erythematosus, Crohn disease, collagen vascular disease, rheumatoid arthritis)
Scleral thickness less than 530 micrometers as measured 3.5 mm posterior to the angle
This procedure may be performed safely under local and topical anesthesia. The addition of light sedatives is beneficial to the comfort and well-being of the patient. If more secure with the assistance of an anesthetist, the surgeon should remember the benefits of minimal sedation, asking the patient to look in various directions during the surgical procedure. This patient participation allows exposure of the quadrant of the eye being operated on.
Lorazepam (1-2 mg) or diazepam (10-20 mg) may be given preoperatively about 1 hour before the procedure is started. Letting patients know in advance what they can expect during the surgical procedure (and why they are not being put to sleep) will greatly enhance their ability to cooperate. General anesthesia and its inherent risks are not indicated because of the effectiveness of topical anesthesia. In addition, local injectable anesthesia should be avoided because of conjunctival swelling and reactive hyperemia.
The only anesthesia the author uses perioperatively is 4% Xylocaine (AstraZeneca, Waltham, Mass) placed on a pledget and applied to each quadrant prior to performing surgery on that quadrant. Alphagan eye drops administered 15-30 minutes prior to beginning the procedure helps decrease operative bleeding.
Even if an oral medication (instead of an IV medication) is used, having an IV in place is a good idea. Since 250 mL (changed from 500 mL) of 20% mannitol needs to be infused within 30 minutes after the completion of this procedure, with a patent IV in place, this infusion can be started as the surgeon is nearing the end of surgery. The author usually starts the mannitol while beginning to finish the insertion of the last segment. Because of the manipulation and the pressure exerted on the eye during the surgical procedure, malignant glaucoma is possible. However, no cases of malignant glaucoma have been associated with this surgical procedure, and the infusion of the mannitol is believed to be a prophylactic step.
After instillation of 0.5% proparacaine, the patient's eyes should be marked with a skin scribe or a marking pen at the 12-o'clock position. Up to 10-15° of torsion or eye movement can occur when the patient is in a supine position as compared to the upright position. If this mark is not placed accurately, the segments may be off by as much as 20°. This inaccuracy in positioning may be sufficient to compromise the anterior circulation of the eye.
In the preoperative evaluation of the patient, include the following steps:
- Distance visual acuity with correction in place
- Visual acuity at 40 cm, 30 cm, and 20 cm using the Sloan method
- Visual acuity starting at 70 cm and bringing the eye chart closer until the smallest line read starts to blur. This test provides the baseline diopters of accommodation. The formula of measurement is 1/distance in centimeters X 100. For example, if a patient is able to clearly read the line up to 50 cm, the formula applied would be 1/50 X 100 = 2 D of accommodation.
- Axial length measurement and corneal topography
- Scleral thickness 3.5 mm posterior to the angle, as verified via B-scan ultrasonography, with appropriate tissue velocity correction factors (Refer to applicable diagnostic imaging literature.) 
Step 3 is also important in the postoperative evaluation to measure the amount of accommodation gained by the patient. When repeating this step postoperatively, patients must use the same line that they were able to see preoperatively (even if only 20/200). As in the preoperative evaluation, bring the eye chart toward the patient to determine the gain in accommodation. To illustrate (continuing from the example in step 3), if the patient is able to clearly see the same line on the eye chart when brought up as close as 20 cm, the result is as follows: 1/20 X 100 = 5 diopters of accommodation.
Step 4 results should not be affected by the surgery. Corneal topography may show induced astigmatism immediately after surgery. In all cases, this astigmatism is temporary and typically resolves within 1-3 months. At the time of this writing, SRP using the PresVIEW™ System has successfully been approved to begin FDA Phase 3 clinical trial enrollment.
The 6 basic steps involved in this procedure are outlined below. 
Oblique quadrant or meridian marking
Opening the conjunctiva (see video below)
Scleral marking (see video below)
Lamellar scleral tunnel formation (see video below)
Implant placement (see video below)
Each of these steps with appropriate clinical pearls will be discussed in detail.
With the recent addition of the PresVIEW™ Scleratome (Refocus Group, Dallas, Tex), step 4 (lamellar scleral tunnel formation) is significantly improved over previous surgical techniques. The PresVIEW™ Scleratome is discussed in Formation of the lamellar scleral tunnel.
An eyelid speculum is used to open the eye for maximum exposure (see video below). With the proparacaine on board, the precision calipers are set to 6.0 mm and the corneal center is determined using a 4-point interpolation procedure. One point of the caliper is inked for marking, and the other point is placed at the edge of the limbus. The inked point of the caliper is used to mark the cornea center based upon the 6.0 mm distance. This process is repeated for the 3-, 6-, 9-, and 12-o'clock positions. The corneal center is determined to be the point central to all 4 marks.
The meridian marker is inked and used to mark the 45° meridians. The point of the central locating feature of the marker should be placed at the corneal center and either 1 of the 2 engraved marks should be oriented with the 12-o'clock position. This will ensure that the marks are delivered accurately at the oblique meridians. The marks will not necessarily be made directly onto the limbus. Most likely, they will be about 0.5-1.0 mm posterior. Their purpose is to delineate the axis for the placement of the lamellar scleral tunnel, not the limbus location.
Re-ink any of the marks that may fade by the time they are ready to be used. Also, because a flap will be created in the conjunctiva, the marks need to be visible. This may necessitate remarking closer to the limbus. After successfully completing the marking, 12 separate spots, in groups of 3, should be seen. They are centered on the 45° meridians. Straddling those will be 2 marks that are 4 mm apart (the length of the tunnel). Barrie Soloway, MD, at the New York Eye and Ear Infirmary, prefers to add an exclamation point as a secondary locator mark, and this has become the author's preferred method when instructing new surgeons. These marks are made on the cornea to ease in the re-marking of the clockwise positions if required later in the procedure.
A corneal shield can then placed on the cornea with viscoelastic or viscous artificial tears (see video below). This shield is placed after the quadrant marks have been made to ensure stable ink markings, which could be interfered with by the viscous fluid.
Opening the conjunctiva
The video below shows conjunctival opening.
In performing this procedure for 4 years, the author has used 3 different techniques to open the conjunctiva for exposure of the surgical site prior to implanting the segments.
The first technique, which is no longer used, incorporated a limbal-based conjunctival flap in which the conjunctiva was incised approximately 7.0 mm in each oblique quadrant, about 6.0 mm posterior to the limbus. This technique was difficult because of the time of closure and the direct splitting of the Tenon membrane. In addition, no matter what was done to ensure that the incision was made posteriorly, it appeared to drift forward, with the suture lining lying over the belt loop and the segment.
When using the PresVIEW™ Scleratome, the method of exposure is to make a 360° peritomy with relaxing incisions using the pointed tipped scissors at the 3- and 9-o'clock positions. The Tenon capsule can be pulled back using the blunt tipped scissors, as well as completing the peritomy.
First performing surgery on the inferior quadrants is recommended for the following reasons.
The time to perform the surgery is longer than the anesthetic's (ie, Xylocaine) effect. After the topical anesthetic wears off, a reactive hyperemia and/or a postanesthesia hyperesthesia occurs in many patients. These conditions make further anesthesia more difficult to attain. See videos below.
While anesthetizing the superior quadrants, the anesthetic pools in the lower quadrants. By the time the surgeon approaches the lower quadrants, they have already gone through the cycle of anesthesia (as mentioned above).
When deciding which of the 2 inferior quadrants to first operate on, choose the quadrant with the least amount of bleeding (see video below). By the time the surgeon approaches the second quadrant, natural hemostasis should have occurred. The author does not cauterize in preparation of these incisions because this shrinks the conjunctiva and makes reapproximation less accurate, leading to poorer coverage.
The videos below show scleral marking.
After proper exposure, the next step is marking for the scleral tunnels. Using a proprietary method, Refocus Group, the manufacturer of the PresVIEW™ System, has determined a range of distances appropriate for creation of the lamellar scleral tunnel posterior to the meridian marks based upon the following assumptions:
The transverse sclera sphere of the globe varies little between myopic eyes and hyperopic eyes or between male eyes and female eyes.
The variations in distance from the anterior surface of the cornea to the lens equator in an emmetropic eye are mostly due to variations in the depth of the lens.
In addition, adoption of these ranges to a myopic or hyperopic eye can also be made based upon the following:
The majority of variation in the depth of the anterior chamber in myopic and hyperopic eyes is due to the changing shape of the cornea.
The relative position of the anatomy from the iris to the posterior lens remains relatively constant and similar to an emmetropic eye.
Based upon an A-scan ultrasonogram of the patient's sagittal lens depth, Refocus Group calculated distances for marking the posterior position for fixating the PresVIEW™ Scleratome. This mark is made using a precision caliper by inking the posterior point and setting the caliper as follows:
Sagittal lens depth less than 4.10 mm - Set to 2.75 mm
Sagittal lens depth 4.11-4.89 mm - Set to 3.00 mm
Sagittal lens depth more than 4.90 mm - Set to 3.25 mm
The anterior (noninked) point of the caliper is positioned on the clockwise meridian mark. The posterior point is pressed firmly and perpendicular to the scleral surface to produce a lasting mark that is point shaped. (A circular mark posterior to the limbus is important for orientation of the PresVIEW™ Scleratome.)
The PresVIEW™ Scleratome Footplate Marker is used to place marks on the sclera in preparation for the next step of the procedure. This marker has the same shape as the sclerotome footplate and orients with the caliper mark made off the clockwise meridian mark. The crescent shaped side feature of the marker is placed concentrically with the caliper mark such that the anterior edge of the footplate marker is substantially parallel to the clockwise and counterclockwise meridian marks. One pair of prongs beneath the footplate marker is intended to provide reference points on the sclera for placement of the forward fixation features of the PresVIEW™ Scleratome hand piece. Violet dye is put on the tips of these prongs to facilitate visualization of the exact area for the sclerotomy.
The technique the author prefers in marking is as follows. The crescent shaped anterior feature of the footplate marker is placed on the sclera in alignment with the caliper mark and with the forward prongs lifted from the surface. The conjunctiva is pushed back with a cellulose spear to absorb moisture and to gain exposure. The prongs are then pressed firmly onto the sclera once the anterior edge of the footplate marker is properly oriented parallel to the meridian marks. This provides for the PresVIEW™ Scleratome hand piece location marks that have reasonable longevity, as small indentations are still visible in the sclera even if the ink has been diminished.
Formation of the lamellar scleral tunnel
The videos below demonstrate sclerotomy and creation of the belt loop.
The PresVIEW™ Scleratome should be prepared beforehand according to the PresVIEW™ System Instructions for Use (see video below).
The blade is handled using the blade loading tool to remove the blade safely from the case and to align and fix the blade to the hand piece of the PresVIEW™ Scleratome. The footplate and the blade guard should already be attached to the hand piece with the blade guard closed over the new blade prior to use. The blade guard ensures unhindered blade motion through the sclera, as loose tissue and thrombus can infiltrate the blade connection to the hand piece and reduce the efficiency of the blade travel in comparison between the first tunnel and the last tunnel. The blade should be lubricated before the creation of each tunnel by activating the sclerotome while suspending the hand piece assembly in a bowl of sterile saline. Care should be taken when performing this operation, as the fixation features on the sclerotome footplate are delicate and can become damaged during handling.
The technique the author prefers in creating the lamellar scleral tunnels is as follows. The forward fixation features on the "toe" of the PresVIEW™ Scleratome Footplate are aligned with the marks made in the sclera clockwise and posterior to the caliper mark. The points of the fixation features should be engaged into the sclera followed by maneuvering of the hand piece flush with the surface of the sclera. The anterior crescent shaped feature should be aligned concentrically with the caliper mark, and the anterior edge should be parallel to the meridian marks. Pushing back the conjunctiva with a cellulose spear is important to, once again, absorb moisture and to prevent interference between the sclera surface and the underside of the PresVIEW™ Scleratome Footplate. Ensuring that the "heel" of the footplate is flush with the sclera surface is important so that the blade path is uninterrupted.
Fixation of the PresVIEW™ Scleratome Footplate is achieved using a twist fixation instrument. The twist is placed concentrically within the crescent shaped feature of the footplate, perpendicular to the sclera and oriented with the groove of the blade guard. Fixation is achieved by turning the twist clockwise approximately 180° (see video below). This engages the bottom features of the twist into the sclera and prevents shifting of the footplate during blade passage.
Activation of the PresVIEW™ Scleratome is achieved via a foot pedal (see video below). Constant pressure on the black activation pad of the pedal is required to ensure that the blade completes the entire incision and return circuit.
The control box for the PresVIEW™ Scleratome will beep during the incision cycle; short beeps during incision, long beeps during retraction (see video below).
Once the blade circuit is complete, the twist can be removed via a counterclockwise turn and the footplate can be lifted from the sclera surface (heel first, then toe; see video below).
The author's preference is to complete all 4 lamellar scleral tunnels before placing the first PSI. Since use of the hand piece can sometimes cause a reduction in ocular pressure over time, making all 4 tunnels while the eye is still firm ensures the highest quality tunnels, from start to finish. In addition, the amount of pressure exerted by the surgeon when using the hand piece is the primary source of discomfort for the patient during the procedure; this discomfort varies from patient to patient as well as from surgeon to surgeon. By completing all 4 tunnels sequentially, the time period through which the patient must experience this discomfort can be minimized.
After completion, each tunnel must be assessed for adequacy. This is important, as tunnel length may vary depending on globe firmness and footplate fixation during blade circuit. Each lamellar scleral tunnel requires the insertion of a tapered measuring spatula that provides immediate visual feedback on tunnel quality. The spatula has gold engraved marks across the mid section that indicates tunnels of 3.50-4.00 mm in length (see video below). The PresVIEW™ Scleratome produces tunnels that are generally 3.75-4.25 mm in length. Tunnels less than 3.5 mm in length require extension via a manual sclerotomy. Tunnels in excess of 4.50 mm in length can result in an increased risk of subluxation (or shifting) of the implant. Reduction in tunnel length using the vertical diamond blade is recommended.
Implant placement, techniques, and hints
The videos below show belt loop formation and animation of the scleral band.
The efficient way to proceed to the next step of implant insertion is by maintaining globe fixation, especially if good fixation is already established. The assistant will then hand the implant loaded in the implant forceps to the surgeon. Deciding whether the implant should be placed upside down and then rotated or whether it should be placed directly right side up through the belt loop is important at this point. The following consideration should be made in making this decision.
If any difficulty is encountered in forming the lamellar scleral tunnel, whether being excessively deep (as a function of the percentage incision depth versus preoperative scleral thickness) or needing to change the length of the tunnel using the diamond blade(s), the surgeon should opt for putting the implant in upside down. When inserting the implant, if it is placed right side up, the leading nose of the implant has a tendency to want to project inwardly or toward the inner globe. This is due to not only the shape of the implant but also the tight scleral tunnel because it pushes down constantly on the implant as it is being inserted. This is consistent with the design intent of the implant "lifting" the sclera anterior to the implantation site. See video below.
Because of this natural tendency, and if the surgeon is overly aggressive in manipulating the implant across a tight tunnel, the implant may penetrate the underlying sclera and enter the suprachoroidal space. The few documented occurrences of this event have not resulted in serious adverse effects. The author is personally aware of 2 implants that were inadvertently placed into this suprachoroidal space and were left there with no sequelae occurring.
When inserting the implant right side up, it is easier to place the implant within the entrance point first. To get the insertion started, the implant has to be delivered at about a 45° angle and inserted into the lamellar scleral tunnel blade entrance side. This angle is maintained until the underside notch of the implant is reached (which is 0.75 mm from the end of the implant). Once the tip portion of the implant is fully within the tunnel, the channel forceps should be angled up enough to prevent the tip of the implant from rubbing the sclera at the base of the tunnel. Once this angle is maneuvered, the implant can be fully advanced across the tunnel. See video below.
This maneuver will prevent the leading edge of the implant from damaging the scleral bed beneath or penetrating due to tearing this portion of sclera. Of equal importance is the hand that is holding the fixation device. As the implant is being placed, the fixation device held in the other hand applies an equal counter pressure, that is, as the implant is being inserted into the tunnel, the fixation device is pushed toward the implant. This slightly puckers the lamellar scleral tunnel exit, provided appropriate scleral depression of the fixation device is applied. The exit site of the tunnel will then fish mouth and allow an easier exit of the leading edge of the implant being placed. See video below.
If fixation is lost during this counter pressure maneuver, the surgeon can try refixating or even changing to a different fixating device. Likewise, if the surgeon is using the twist pick, remembering to apply the appropriate rotational force to maintain fixation on the sclera is important. By not applying this rotational force, the surgeon can inadvertently rotate the twist pick and fixation will be lost. Another key point on using the twist pick is that the surgeon must rotate the twist pick at least 180° to achieve good scleral fixation.
The lamellar scleral tunnel should be tight, and often at this point, just prior to the implant exiting the tunnel, a lot of pressure needs to be exerted. Sometimes, a slight wiggling of the implant will help if the surgeon feels that the implant cannot be exited. Otherwise, the implant can be removed and inserted from the other direction or inserted upside down. Once the implant is inserted from the exit site, and as it approaches the original entrance to the tunnel, its advancement from the belt loop will be much easier. This is because of the fact that the tunnel has been stretched by the first attempt of the implant insertion.
When the implant is nearly ready to exit, the surgeon can use the tapered spatula to both depress the sclera and form a ramp for the implant to exit (see video below). If the spatula is placed parallel to the belt loop, only very mild countertraction can be applied safely. If too much pressure is applied, the spatula will unexpectedly slip into the suprachoroidal space. For this reason, the author places the spatula parallel to the exit incision and perpendicular to the tunnel. This placement allows the surgeon to exert as much counterpressure as necessary.
Another helpful way to use the spatula is as follows. When making the tunnel or prior to placing the implant, inserting the spatula all the way through the incision site and then slightly depressing to tamponade any subscleral bleeding are often beneficial. If the exit lamellar scleral tunnel appears to be a little tight, the spatula can be used to slightly stretch out the exit incision, making the placement of the implant a little easier.
The advantage of placing the implant upside down is that the leading edge of the implant does not have a tendency to submarine into the suprachoroidal space; instead, it hugs the undersurface of the belt loop and allows for an easier exit (see video below). The disadvantage of upside-down insertion is that the belt loop is slightly stretched by rotating the implant back into its upright position. Submarining of the implant can occur when inserted from either the entrance side or the exit side of the tunnel.
If, during the tunnel formation, extending or reducing the incision length using the diamond blade was necessary, consider inserting the implant upside down. This implant insertion approach will avoid blind pockets (due to manual extension in tunnel length) or scleral flaps (due to manual reduction in tunnel length). When inserting the implant upside down, the position of the implant has to be greater than a 45° angle toward the entrance point of the sclerotomy to get the tip of the implant into the belt loop. If difficulty is still encountered prior to implant exiting, counterpressure is needed to push the implant through the tunnel exit.
No viscoelastic or other lubricating material should be used to help the implant slide through the sclera, because whatever allows the implant to slide in easily will also increase the likelihood of it sliding out. To prevent postoperative subluxation, none of these lubricants should be considered. In addition, any viscoelastic agent underneath the conjunctiva causes a prolonged swelling and conjunctival edema and prevents early adhesion of the Tenon capsule and the conjunctiva to the surface of the tunnel, which will help secure the implant in place. Once the upside-down implant has exited and has equal portions extending out of both ends of the belt loop, the implant is now ready to be rotated.
When rotating the implant (see videos below), the surgeon should position his wrist and hand in such a fashion so as to anticipate the 180° rotation and allow this movement to be made in a single, smooth step. Often, because of poor exposure or other difficulties, this cannot be achieved, so 0.12 forceps can be used at the other end of the implant. Once the implant is rotated halfway, the other forceps can be used to grab the opposite end of the implant and complete the rotation. If the implant is not extended evenly on either side of the belt loop, the least prominent edge of the implant should be grasped by the forceps for rotation. The reason for this is that, as the surgeon rotates with the forceps, it has a tendency to pull out the implant. If the surgeon grabs the edge of the implant that is more exposed, the other end may fall back into the tunnel. When using channeled forceps, the implant can be rotated as soon as the leading edge of the implant exits the belt loop.
Currently, the author often places implants upside down followed by rotation. Once the implant is in position, one has to make sure it is symmetrically exiting on either side of the tunnel. This is particularly important because the notches on the underside of the implant should be aligned with the entry and exit points of the tunnel. This is the reason for the precise 3.50-4.0 mm width of the engravings on the tapered spatula for visual verification of tunnel length. By ensuring that the channels under the implant are on or just past both edges of the sclera, it encourages the sclera to ride up into the notch and prevents the implant from subluxation. See videos below.
The difficulty encountered when placing the segment often leads surgeons to think about other maneuvers to facilitate segment insertion. Early on, the author developed a spatula with an upturned lip at the end to catch these notches (see video below). However, because the belt loop is so tight, no room exists for the segment and the spatula. This step was quickly abandoned. As mentioned earlier, lubricating agents should not be used. Guides, such as the Sheets guide used in the implantation of intraocular lenses, cannot be used because of the very tight relationship that the tunnel has around the implant. The tighter the fit, the greater the scleral lift, and the more accommodation the patient gains postoperatively.
New methods for improving the ease of implant placement across the scleral tunnel have been developed by Refocus Group and greatly simplify this process. The author has personally participated in validation surgeries for these techniques and can attest to their value in enhancing the ergonomics of the surgery.
The videos below show closure of the conjunctiva.
After all implants are in position, the conjunctiva is pulled over the implants and back toward the original conjunctival relaxing incisions. The 2 corners of the conjunctiva at each relaxing incision are identified, and a single 10-0 nylon suture is placed at the 3- and 9-o'clock positions. The suture should be tied in a buried knot fashion, taking a scleral bite at the limbal interface to prevent migration of the conjunctiva.
If the conjunctiva is stretched or torn prior to placing the 10-0 nylon in the sclera, the surgeon should pull the conjunctiva and make sure the extreme aspects do provide sufficient coverage. This coverage should mean that the conjunctiva should be within 1.0-1.5 mm of its original insertion. If it is not, the suture bite should take a little extra conjunctiva and pull it toward the 6- or 12-o'clock position to pull it tighter. Only a single suture is necessary for each relaxing incision, and it has provided adequate coverage in all the author's cases.
In the rare instances when the PresVIEW™ Scleratome produces a lamellar scleral tunnel too long or too short, the diamond blades provided with the PresVIEW™ System Instrument Kit can be used to correct them. These blades were the original instruments developed for the manual procedure and are still useful in these special instances.
Tunnels of excessive length can be shortened using the vertical diamond blade. The table top marking instrument can be used to indicate the optimal exit length by aligning the instrument with the incision entrance. The diamond blade can then be used to produce a 300-micrometer vertical incision across the mark, shortening the tunnel appropriately. The tapered spatula can be used to verify adequacy of the incision be inserting it into the newly formed incision (exit). If the spatula does not slide easily into the tunnel, a scleral flap may still be separating the newly made incision from the original tunnel. The lamellar diamond blade can then be carefully inserted into the vertical incision to complete the pathway down and across the original tunnel.
Tunnels of inadequate length can be extended in a similar fashion. The table top marking instrument is used to indicate the optimal exit length by aligning the instrument with the incision entrance. The vertical diamond blade can be used to produce a 300-micrometer vertical incision across the mark, creating the new tunnel exit. The lamellar diamond blade can then be carefully inserted into the original tunnel incision entrance to complete the pathway down and across the newly created tunnel exit. The tapered spatula can be used to verify adequacy of the lengthened tunnel by inserting it into the newly formed incision (exit) and remeasuring the extended length. See videos below.
Based on the surgeons' experience and the anticipated speed of surgery, at some time during the final implant, the staff should be instructed to start an IV of 250 cc of 20% mannitol.
At the conclusion of the case, the pupil should be observed; if the pupil is dilated or asymmetrical, 1% pilocarpine should be given to ensure that the pupil is round and symmetrical. If there is any oblique shape to the pupil, pilocarpine should be applied and the patient should be observed closely until the pupil is round.
The patient's eyes are patched only if a corneal abrasion is present. Otherwise, no patching is necessary.
For the most part, postoperative pain usually only requires extra-strength acetaminophen, but a few patients have had more serious pain.
If any corneal abrasion is present, the author would hesitate to put on a collagen shield or a contact lens, because it could migrate underneath the conjunctiva and prevent it from sealing down around the implant.
Postoperative eye drops, including the antibiotic Ciloxan (Alcon, Fort Worth, Tex) and usually Flarex (Allergan, Irvine, Calif) or another mild steroid, are sufficient. For cases of marked inflammation postoperatively, one can change to a prednisone acetate 1% or even add Voltaren (CIBA Vision, Duluth, Ga). However, this is rare, and most of the patients tolerate the postoperative irritation.
Patients who undergo SRP must also undergo rehabilitative eye exercises to ensure optimal results. The ciliary muscle of these patients has not been used for a number of years and requires physical therapy.
Before the exercises are started, the quality and the quantity of the tear film must be evaluated. During the first few weeks, the conjunctiva is swollen over the implants and prevents the eyelids from spreading the tear adequately; therefore, artificial tears are necessary. Artificial tears should be used every 2 hours, and a bland ointment should be used at bedtime. Sometimes, punctal plugs are also necessary.
The accommodative exercise is called the push-up/push-out technique. Patients are given a reading card and told to hold the card at 10 cm from their eyes. They are to focus on the smallest line that they can see and then concentrate without squinting and see if they can see any letters on the next smaller line. This exercise is repeated as patients slowly move the near card away from their eyes while keeping the smaller line in focus until the near card is at arm's length. Then, the patients should bring the near card slowly back up to 10 cm from their eyes while trying to keep the same line in focus. Once the card is 10 cm from their eyes, they are instructed to try and see the next smaller line. This exercise should be done 6-8 times for each eye, 4-5 times a day.
Push-up exercises using a pencil or other nonaccommodative target will only strengthen the convergence mechanism and will not effect accommodation. Patients must focus on print while doing the eye exercises to increase ciliary muscle function. The author has found that it is better to start at near and move the target away, as described above, rather than to start with the target further away and bring it close.
Anterior segment ischemia, though rare, is a complication that could develop if segment placement is not accurate. During the first case that the author witnessed in Monterrey (although quite successful), the segments were 7.0 mm long and caused a small amount of local ischemia in 1 quadrant. The current PSIs are 5.5 mm long, and, if not placed in the exact quadrant, anterior segment ischemia can still occur. The design and the methodology for accurately placing the scleral implants have been significantly improved to address and curtail this unwanted adverse event.
In the 7 years that the author has been performing the SRP procedure, many modifications have enhanced both the procedure and the outcome.
Such modifications include design upgrades in the scleral implant and improvements in the instrumentation, including the newly developed PresVIEW™ Scleratome. This device, a highly sophisticated automated instrument, is designed to make the scleral tunnel in one step. Through FDA wet lab validation testing and the ongoing FDA clinical trials, this instrument has proven to provide greater uniformity and consistency among surgeons.
The author has been performing eye surgery for over 25 years, and, in that time, new surgical procedures and techniques have been developed. To minimize patient risk and to maximize success with changing procedures or attempting new procedures, pay particular attention to the history of that procedure. The author has studied diligently from surgeons who have performed the procedures in the past and then mimics their techniques. Changes in the procedure are made to accommodate the author's personal surgical skills only after overcoming the learning curve, which is perhaps the most important advice that the author gives to new surgeons regarding the SRP procedure.
Many of the surgeons who have significant experience with the SRP procedure would advise new surgeons to perform it exactly as developed. Making single small changes, one at a time, to determine if that change in the procedure is advantageous or not, is recommended only after overcoming the learning curve. In performing this procedure and mentoring over 30 physicians, the author has seen many combinations and techniques; some have been successful, and some have failed. The author's intent in this article is to provide a detailed history of his experience with the procedure so that the new surgeon may learn from these experiences and not repeat any changes in the procedure that have been unsuccessful.
Four surgeons with the most experience in performing the SRP procedure include the author; Barrie Soloway, MD; Larry Lothringer, MD; and Brian Boxer-Wachler, MD. Collectively, these surgeons have performed nearly 75% of the procedures performed thus far and have a wealth of experience and teaching ability.
The author believes that surgically reversing presbyopia is definitely possible, and performing the SRP procedure presented herein is rewarding. Although not all patients are happy with the outcome, the patients who are happy far outweigh the small number of patients who are less gratified. The ability to reverse presbyopia is perhaps the last goal, the final frontier, of the refractive surgeon. Ophthalmic surgeons can pool their experience and resources to perfect this procedure and to put an end to the frustrating experience of presbyopia.