Ординатура / Офтальмология / Английские материалы / Retinal and Vitreoretinal Diseases and Surgery_Boyd, Cortez, Sabates_2010

pre-surgery determinant of post-operative visual acuity. While 87% of eyes with retinal detachment sparing the macula recover visual acuity of 20/25 or better, in eyes with successful reattachment of macula-off detachment, approximately 40% to 60% of eyes have final visual acuity of 20/50 or better.

PNEUMATIC RETINOPEXY

Pneumatic retinopexy, first introduced by Dominguez in Spain and then by Hilton in the U.S., allows the reattachment of the retina by the intravitreal injection of an expanding gas bubble. Transconjunctival cryopexy or laser photocoagulation as well as post-op- erative head positioning are mandatory for an increased rate of success. Pneumatic retinopexy can be performed in an office setting and may be the most cost-effective means of retinal reattachment.

Indications

Pneumatic retinopexy is an alternative for the treatment of retinal detachments in cases of a single retinal break, or a group of breaks confined to the superior two thirds of the retinal periphery. If the peripheral retinal view is adequate, pseudophakic detachments can also be managed with this technique.

Despite its advantages, some contraindications to this procedure have been identified:

(1) in breaks larger than one clock-hour, or

where there are multiple breaks extending more than three clock hours, (2) breaks are located in the inferior four clock-hours of the eye, (3) where there is significant traction on the retinal tears, (4) in cases of patients who are unable to maintain bodily adequate position, (5) due to the brief elevation of the intraocular pressure, advanced glaucoma patients are at higher risk for further optic nerve deterioration, (6) in the presence of cloudy media which prevent correct identification and treatment of the breaks.

Advantages and

Disadvantages

Advantages to this technique include: somewhat shorter time in surgery, less inflammation, and less cost to the patient. General anesthesia is not required. However, this technique is not free of complications:

(1) high intraocular pressure may develop while introducing the gas into the intraocular cavity. (2) When a gas-bubble has been introduced, there may be pulling on the vitreous and the retina which may result in bleeding or in the development of a new retinal tear.

(3) subretinal fluid may shift to the macular area while the bubble is pushing the break and the retina. This fluid behind the fovea will worsen the prognosis.

As a consequence, it is very important to carefully select the patient on whom we decide to apply pneumatic retinopexy.

Surgical Technique

Preparing the Syringe with Gas

Sulfur hexafluoride (SF6) and perfluoropropane (C3F8) are the most frequently used gases. The type and amount of gas depends on the number and location of the breaks. A 0.3 mL gas-bubble covers more than 45o of the area of the retina, but it takes approximately a 1.2 mL bubble to cover an arc 80o to 90o, of the surface area. A dose of 0.5 mL of SF6 doubles its size in 36 hours, and 0.3 mL of C3F8 quadruples it in the same period of time. In most cases a gas bubble volume of 1 mL, which requires an injection of 0,5 mL of pure SF6, would be enough. The injected gas bubble before expansion must be moderately larger than the retinal break, to prevent subretinal gas. The area of the breaks should be covered by the bubble for at least 5 days. Air can be used but requires a larger volume and sometimes its longevity might be insufficient to allow a chorioretinal scar to form.

Frequently a three (3) cc syringe with a millipore filter is used to draw the gas from a low-pressure system connected to the SF6 tank (the tube connecting the gas cylinder with the syringe, including the filter, is flushed through with gas to ensure no dilution with room air). A disposable 30 gauge needle is then placed tightly on the syringe, and the excess gas is expelled leaving the exact amount intended for injection. This amount may

vary depending on the size and location of the breaks. This gas lasts about two weeks inside the eye (0.3 mL of C3F8 last about 38 days).

Patient Preparation

The pupil is dilated in the usual manner using cyclopentolate 1% and neosynephrine 2.5%. A preoperative softening of the eye is recommended; for this purpose, personally, we prefer to apply a “Mercury Bag” which is placed over the eye for 20 to 30 minutes, prior to the injection. Then topical and subconjunctival anesthesia is given.

Retinopexy

Initially some surgeons delayed cryopexy (or laser treatment, applying a conventional laser through the pupil and through the gas-bubble, or using a diode laser through the sclera, instead), until the retina has been flattened against the retinal pigment epithelium. The technique has evolved into a one stage operation; cryotherapy may be applied to detached retinal break(s), if they are not highly elevated prior to the gas injection. It is often possible to apply laser treatment through a large gas bubble, or the bubble is moved away by tilting the head of the patient. The laser indirect ophthalmoscope allows treatment of the extreme anterior periphery, and, if the detachment is shallow, it may be possible to apply a laser using scleral depression to flatten the retina.

Gas Injection into the Eye

Sterilization of the ocular surface is obtained with topical povidine iodine solution. After placing a sterile lid speculum and with the patient supine, the head and the eye are turned approximately 45o to one side so as to place the pars plana uppermost. The injection is usually performed temporally, 4 mm behind the limbus, unless the pars plana is detached or large retinal breaks are present in that area, in which case another site is selected. In a patient with retinal detachment in whom there is intraocular fluid the gas is placed under the anterior hyaloid. The needle is directed toward the center of the vitreous and inserted to a depth of 7 to 8 mm and then is partially withdrawn, so that about 3 mm of the needle is left inside the eye. In order to create a single gas-bubble, the gas should be injected in a moderately brisk fashion, avoiding the formation of so-called “fish eggs”, in which multiple small bubbles at the needle tip are formed. As the needle is withdrawn from the eye, a sterile cotton tip applicator is rolled over the needle-tract and the head of the patient is rotated to the opposite side to prevent leakage of the gas. Immediately following this, an indirect ophthalmoscopy is performed to corroborate the patency of the central retinal artery. If the artery is closed and does not reopen within 10 minutes a paracentesis is done to lower intraocular pressure. Finally antibiotic-steroid drops, or in ointment, are applied, and the eye is patched.

In patients with a bullous retinal detachment which extends almost to an attached macula, placement of a gas bubble might push fluid into the macula and detach it. To prevent this problem, after the injection, the head of the patient is turned to a face-down position; over a period of 10 to 15 minutes the patient́shead is very gradually rotated until the retinal break is uppermost, causing the bubble to roll toward the retinal break, pushing the subretinal fluid away from the macula and back into the vitreous, and flattening the retina.

Positioning of the Patient

Great effort must be made to ensure that the patient and his/her family understand the importance of proper positioning, so that the retinal break is uppermost. It may be helpful to draw an arrow on the patient’s eye-patch, or on their forehead, to indicate the meridian of the tear, so as to help in postoperative positioning. The patient is instructed to point the arrow toward the ceiling. In order to avoid cataract formation, the patient has to avoid lying on the back, facing towards the ceiling. As an example, if we have a tear in the nasal superior quadrant of the right eye, we would keep the head tilted toward his/her right side so that the bubble migrates to the superior nasal quadrant. If the tear is on the superior temporal quadrant of the right eye, the tilting is done toward the left side. The correct head position should be maintained during the waking hours for at least five days.

Remaining in this position during sleep is advisable. The contact of the air-bubble with the edges of the tear blocks the passing of fluid to the subretinal space. Because of this tamponade effect the subretinal fluid will be absorbed within approximately 24 hours. If the retinopexy has not been previously applied, cryo, or laser treatment, is applied to the edges of the tear to create a chorioretinal adhesion and thus seal the tear.

The patient should be seen at frequent intervals during the early postoperative period to assess adequacy of the retinopexy, and to rule out possible complications, including new or missed retinal breaks and recurrent retinal detachments.

Complications

Intraoperative Complications

After placing the patient in the supine position and with scleral depression the bubble is relocated. The formation of new retinal breaks has been reported in 14% to 19% of cases (Figure 21).

The most common intraoperative complication is the unwanted injection of the gas anterior into the anterior hyaloid phase, which gives the appearance of a “sausage”, to the injected bubble. As the gas expands over 24-48 hours, it usually breaks through the anterior hyaloid face and enters the vitreous cavity (this complication is avoided by injecting deeper into the center of the vitreous cavity, which ensures penetration of the anterior hyaloid face).

Another intraoperative complication is the formation of subretinal gas when small gas bubbles gain access to the subretinal space.

Figure 21: Complications during Pneumatic Retinopexy. A common complication is injection of gas into the anterior hyaloid space or even subretinal, which gives an appearance of a balloon to the bubble injected (A). This complication will cause a re-detachment of the retina. This side view illustration focuses the proper maneuver to inject the bubble into the vitreal space

(B) avoiding the retina with the needle (S). (Art from Jaypee Highlights Medical Publisher).

Postoperative Complications

Cataract formation, endophthalmitis and extension of the retinal detachment can occur. Formation of new breaks, PVR and a reopening of retinal breaks have also been described.

Anatomical and Visual

Results

With one operation, and with occasional postoperative cryotherapy or laser supplementation, retinal reattachment has been achieved in 80% to 84%. In cases of failure, a subsequent scleral buckling can be offered which would increase the success rate of retina reattachmet to 98%. The visual acuity recovery has been reported to be statistically significantly better in patients after pneumatic retinopexy, particularly if the detachment included the macula for at least 2 weeks, when compared to a scleral buckle.

LINCOFF’S ORBITAL

BALLOON

What is a Lincoff Balloon and How does it Work?

The Lincoff ́sballoon is a non-drainage technique and is another alternative used to create a temporal buckling effect. It was

described by Harvey Lincoff, M.D., in New York, in 1979. This technique consists of the use of a small balloon made of siliconized latex, - which combines the tissue inertness of silicone with the strength and elasticity of latex-, at the end of a soft plastic tube which has been modified by the addition of a steel stylette that stiffens it, facilitating insertion. A balloon catheter that accepts a fiberoptic stylette, in order to facilitate location, has been developed. The proximal end of the catheter accepts the steel or fiber optic stylette and a plastic-adapter, which has a self-sealing valve for inflation. The balloon is inflated by inserting a 1mL syringe into the plastic-adapter and injecting sterile water. The catheter and balloon are introduced in the subconjunctival space to create a temporary buckling effect and to seal the breaks; the subretinal fluid it absorbs through the retinal pigment epithelium.

Indications

The balloon procedure is suitable for retinal detachments caused by tears that are located within a one-clock-hour arc or 6 mm at the equator. Its use is limited in cases of very posterior tears, and in those with an associated PVR. The extent of the detachment is not a factor for patient selection. A retinal break located beneath a rectus muscle is especially suited for this procedure, whereas a sponge explant placed beneath a muscle, particularly a vertical one, will often cause postoperative diplopia.

Surgical Technique

This surgical procedure is not considered a major surgery and, if needed, it can be done in an office-setting. The procedure is performed with retrobulbar, subconjunctival or topical anesthesia. Accurate transconjunctival localization of the breaks is performed and a mark with ink is placed on the conjunctiva. A second mark is made more anteriorly in the exact meridian of the tear, a little posterior to the limbus (where the conjunctiva and Tenon’s capsule merge). Transconjunctival cryopexy is then applied to treat all retinal breaks. Alternatively laser can be applied at a later time when the retina is attached. A sterile field is then prepared applying 10% povidone iodine solution to the conjunctiva. A 2 mm incision is made through conjunctiva and Tenońs capsule at the anterior mark. The deflated balloon is inserted into Tenońs space and subsequently advanced to the location of the break. The stylette is then withdrawn; the balloon is inflated with 0.5 mL of sterile water, and its position is checked with an ophthalmoscope. If necessary, the location of the balloon can be adjusted so that it lies directly beneath the break. Then the balloon is inflated under ophthalmoscopic control to a volume appropriate to the height and width of the break. This usually requires an additional 0.75 to 1.0 mL of water. The sudden expansion of the balloon causes a temporary rise in intraocular pressure, making it necessary to check the patency of the central retinal artery; if required, water from the balloon is withdrawn until flow is restored. To observe the process within the eye one

may use indirect ophthalmoscopy, or the wide angle contact lenses, which allow the surgeon to inspect the periphery and the buckling effect in the specific area of the tear. The main wide angle lenses are the Stanley Chang lens and the Schlaegel Panfunduscope lens (Figure 22) as advocated by E. Malbran. The external portion of the catheter and the valve are taped to the patient’s forehead, antibiotic ointment is applied, the lid is closed over the tube, and the eye is then patched. The fellow-eye is also patched overnight.

The eye is checked on the first-postop- erative day. If needed, the balloon can be enlarged by injecting additional water. After 7 days, the balloon is completely deflated and withdrawn under topical anesthesia. No conjunctival suture is needed.

Results

Successful reattachment of the retina with this technique has been reported in 64% to 96% of cases. Visual results are similar to those achieved with scleral buckling. A disadvantage is the limited number of cases in which its use is appropriate. The indications for the orbital balloon are very similar to pneumatic retinopexy; however the latter is a more popular procedure.

Although this technique is clearly of value in selected cases, it has not gained widespread popularity in the United States, and it probably is not employed as frequently at this time, as it was in the past.

Figure 22: Panoramic Image of Vitreo-Retinal. Cavity with Wide Angle Contact Lenses (Panfunduscope) The panfunduscope provides the surgeon with a much wider field of view (V) to better appreciate panoramic intravitreal and retinal tissue relationships. As an example, the entire structure of the vitreous band spanning from A to B can be seen in a single view, thus providing the surgeon with a most accurate and all-encompassing display of the intravitreal pathology. Such all-encompassing information available to the surgeon can determine the very best approach to solving a problem. The inset shows the resultant field of view of the fundus seen by the surgeon. (Art from Jaypee Highlights Medical Publisher).

Complications

Because the procedure is entirely extraocular, complications are rare. A postoperative shift in the position of the balloon may allow the break to remain open. Also spontaneous deflation of the balloon has been described.

PRIMARY VITRECTOMY AND FLUID-GAS EXCHANGE

Pars plana vitrectomy combined or not with scleral buckle, and fluid-gas exchange, is becoming the more popular approach as an intial surgical therapy for rhegmatogenous retinal detachment. In these cases, vitrectomy is selected to decrease the difficulties and risks associated with scleral buckling, to help relieve vitreoretinal traction in cases of moder- ate-severe PVR. The pars plana vitrectomy is the most invasive approach of all the techniques described above, and may cause postoperative complications, such as new retinal breaks and detachments, and it promotes a high incidence of cataract formation; therefore today this procedure is mainly considered in aphakic or pseudophakic eyes.

vitrectomy, emphasis is placed on removing vitreous adherent to the margin of the retinal breaks. Sometimes the traction is best removed by excising the flap of a horseshoe tear (Figure 23). In order to stabilize the retina, after the posterior vitreous has been completely removed (with previous separation of the posterior hyaloid), heavy fluid can be used (i.e. perfluorocarbon liquid). Once the vitrectomy has been completed, additional heavy fluid is injected to flatten the retina. The subretinal fluid will be pushed through the retinal break, exhibiting a schlieren sign, seen when two liquids of differing refractive index are mixed; this may help to rule out any coexistent peripheral retinal breaks that were not seen preoperatively (Figure 24). When the heavy fluid is near the posterior edge of the tears, an extrusion cannula is placed in the break and a total fluid-gas exchange is performed, which reattaches the retina. Fi-

for draining the subretinal fluid are: the passage of an extendable silicon extrusion catheter through a retinal break, transscleral drainage or making a posterior or anterior retinotomy. Once the retina is flat, retinal breaks are treated with endolaser photocoagulation or external cryopexy (Figure 25).

Results

The results of four reports of this technique yield a weighted average of 78% single-opera- tion success and 89% ultimate anatomic success with one or more operations. These results

Figure 23: Primary Vitrectomy. During this process it is important to remove the vitreous adherent to the margin of the retinal tear and detachment (R). The vitreal traction may be removed by excising the border of the flap of the retinal tear (T). The injection of perfluorocarbon liquid may be useful to retain the retina attached during the vitrectomy (PFC). Endoillumination

(E). (Art from Jaypee Highlights Medical Publisher).

appear to be inferior to those expected from other techniques for primary uncomplicated retinal detachments. In general the preliminary results of the vitrectomy procedure are comparable to those of pneumatic retinopexy, and this is consistent with the fact that both techniques work by a similar mechanism. However, there appears to be little apparent advantage of vitrectomy and intraocular gas injection over pneumatic retinopexy for cases

Figure 24: Sub-Retinal Fluid Drainage Process. When the perfluorocarbon liquid (PFC) is near the posterior edge of the causative retinal tear (R), an extrusion cannula is placed in the break and a total sub-retinal fluid drainage is initiated to reattaches the retina (arrow): Once the vitrectomy is performed a fluid-gas exchange procedure is performed by visualization with endoillumination in one hand (E) and the extrusion cannula in the other (C). (Art from Jaypee Highlights Medical Publisher).

Figure 25: Endophotocoagulation. At the end of the process, once the retina is flat, all retinal tears or lesions are treated with endolaser photocoagulation

(T). In selected cases the surgeon may use external cryopexy as a viable option. In this phase we may observe how the retinal tears is sealed with several rounds of endolaser application (L). (Art from Jaypee Highlights Medical Publisher).

in which the latter technique can be used. It is useful in cases which are not favorable to simpler procedures, however, the surgeon must take into consideration, before choosing one surgical technique over the other, the particular conditions of the patient, such as age, lens status, retinal and vitreal pathology.

SCLERAL BUCKLE VERSUS PRIMARY VITRECTOMY

A recent study by Heimann et al, showed a benefit of the scleral buckle over the primary vitrectomy as a primary treatment for rhegmatogenous retinal detachment in phakic eyes with respect to the best corrected visual

acuity. No difference in the visual acuity was demonstrated in the pseudophakic trials; based on a better anatomical outcome. On the other hand, pars plana vitrectomy was recommended in this particular group of patients.

VITREOUS SUBSTITUTES

Vitreous substitutes have been used to facilitate retinal reattachment surgery since the last century. The first (one ever used) was air in 1911, which provided adequate retinal tamponade. Nonetheless, air tends to be absorbed rapidly from the vitreous cavity diffusing across the retina, limitating is tamponade effect. The use of perfluorocarbon gases began in the 1980s. These gases remain in the vitreous long enough to produce an effective tamponade; however, this prolonged persistence in the eye, may also come with the development of complications such as an increase intraocular pressure and lens opacification.

In the recent decades, great advances have been made in the development of fluids, such as collagen and hyaluronic acid, gases, silicone oils, perfluorcarbon liquids and polymer hydrogels, that can be used intravitrealy to facilitate the surgery of retinal reattachment.

USE OF INTRAOCULAR GASES

Gases Mostly Used and When

In retinal detachment surgery an intraocular gas-bubble is frequently used to flatten the retina by providing a temporary internal tamponade. The development of gases that provide longer internal tamponade has improved the ability to successfully manage complex retinal detachments. They are also used for pneumatic retinopexy in selected conventional rhegmatogenous retinal detachments, and for the treatment of macular holes. Two expanding gases, sulfur hexafluoride (SF6), and perfluoropropane (C3F8), are the most commonly used.

Use of SF6

SF6 is a colorless, odorless, chemically inert and nontoxic gas, which expands twice its volume in 24 to 48 hours. Its longevity inside the eye is from 10 to 12 days. SF6 gas is commonly used in PR. If the bubble is larger than the retinal break, the surface tension of the gas prevents it from passing through the hole.