Roger F. Steinert, MD
Contents
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Pupillary Block Glaucoma |
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Technique for Aphakic and Pseudophakic Iridectomy and Anterior Hyaloid Vitreolysis |
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Anterior Vitreolysis and Cystoid Macular Edema |
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Techniques for Anterior Vitreolysis |
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“Prophylactic” Vitreolysis |
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Coreoplasty |
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Synechialysis |
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Removal of the Intraocular Lens Precipitates |
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Anterior Capsule |
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Retained Cortical Material |
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Intraocular Lens Repositioning |
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Conclusions |
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CHAPTER HIGHLIGHTS |
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Photodisruption with the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser can effectively treat a number of disorders arising after cataract surgery and intraocular lens (IOL) implantation. The pressure wave generated by optical breakdown of an Nd:YAG laser pulse allows the surgeon to cut and manipulate intraocular structures in a variety of postoperative disorders.*
Pupillary block glaucoma
Acute angle closure glaucoma in aphakia and pseudophakia may take several forms, as outlined in Table 52-1.[1,][2] Corneal edema and haze, anterior chamber reaction, and iris congestion may make argon laser iridectomy impossible. Even if a patent iridectomy is formed, an argon laser iridectomy may not relieve the glaucoma because of the role of the vitreous. In many cases, the Nd:YAG laser can better treat these conditions and is the treatment of first choice.[3] The success of the Nd:YAG laser “anterior hyaloidotomy” in curing ciliovitreal block glaucoma, in which surgical and argon iridectomies have failed, demonstrates the pathophysiologic role of the anterior hyaloid face in many cases of pupillary block glaucoma.
Table 52-1 -- Classification of acute aphakic and pseudophakic glaucoma
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Pupillary block (iridovitreal block)
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Aphakic malignant glaucoma (ciliovitreal block)
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Figure 52-1 illustrates a case of pupillary block in a patient who had an iridectomy and antibiotic therapy for endophthalmitis after complex extracapsular cataract extraction with an anterior-chamber IOL (AC IOL). The surgical iridectomy became occluded postoperatively, but an argon laser iridotomy succeeded in relieving the resultant iris bombé. Within weeks, the argon laser iridotomy closed, and the iris bombé recurred with an intraocular pressure of 50mmHg. The Nd:YAG laser at 4mJ readily created several new iridotomies with permanent relief of the iris bombé and pressure elevation. The pupillary membrane also was cleared by the Nd:YAG laser.
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Figure 52-1 A, Recurrent pseudophakic pupillary block with iris bombé after endophthalmitis and closure of argon laser iridectomy. B, Nd:YAG laser at 4mJ readily created several iridectomies (arrows) with permanent relief of the iris bombé. A pupillary membranectomy was also performed. |
The most common setting for pseudophakic block is after placement of an AC IOL, typically after complicated extracapsular cataract extraction or phacoemulsification. The risk of pupillary block is heightened when the surgeon fails to place a large surgical iridectomy. Even after a large anterior vitrectomy, further vitreous may prolapse and occlude the pupil against the optic of the AC IOL. A large surgical iridectomy may also be occluded by prolapsing vitreous, of course, as well as by capsular and cortical remnants.
The role of the hyaloid face in aphakic malignant glaucoma is clearly illustrated by the case shown in Figure 52-2. Three months after complicated cataract extraction and subsequent IOL removal in a patient who also had a large superior loss of iris, the chamber nevertheless became shallow, and the pressure rose to 34mmHg over several days, with the onset of deep pain. A thin, intact hyaloid face or inflammatory membrane was present. The patient was treated with the Nd:YAG laser, which was focused and fired at 3mJ on the hyaloid face through the mild corneal edema despite less than 1mm of residual anterior chamber depth. The anterior chamber deepened immediately.
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Figure 52-2 A, Aphakic malignant glaucoma with apposition of inferior iris to edematous cornea. B, Depth is restored to the anterior chamber immediately after Nd:YAG laser pulses have opened the anterior hyaloid face. Arrows show separation of iris and cornea, in comparison with part A. |
* Portions of the text and figures have previously been published in Steinert RF, Puliafito CA: The Nd:YAG laser in ophthalmology: principles and clinical applications of photodisruption, Philadelphia, 1985, WB Saunders.
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Technique for aphakic and pseudophakic iridectomy and anterior hyaloid vitreolysis
Preparation of the patient
In many cases, the patient will have been treated maximally with miotic agents. If not, application of a miotic agent such as pilocarpine 2% is advisable to place the iris on maximal stretch.
Procedure
From 4 to 8mJ is usually adequate to perforate the iris in one pulse. Corneal edema or an anterior-chamber reaction may necessitate higher energy to obtain the same optical breakdown cutting power. In most cases, at least three iridotomies should be made to ensure full relief of aqueous entrapment, which may be localized into sectors around an AC IOL, and to increase the chance of maintaining at least one long-term patent iridotomy. Iridotomies tend to shrink as bombé is relieved, and the iris falls back. Inflammation also may close iridotomies postoperatively.
If the chamber is markedly shallow or flat, the haptic of an AC IOL, when present, usually provides a small area of clearance from the cornea. The first laser shots can be made immediately adjacent to such a haptic insertion to avoid corneal injury.
After the iridotomy has been completed or when a patent basal surgical iridectomy is already present, the Nd:YAG laser should be fired into the anterior vitreous through the iridectomy or the pupil. This procedure ruptures the hyaloid face and relieves any malignant glaucoma component caused by the intact hyaloid face.
Postoperative care
Intense topical steroid therapy such as prednisolone acetate 1%, or dexamethasone 0.1%, is used at least four times daily and more often as inflammation requires. Inflammation and a tendency for synechia formation also require cycloplegia and mydriasis. Intraocular pressure must be monitored and treated appropriately
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Anterior vitreolysis and cystoid macular edema
Vitreous strands and bands to the wound may cause eccentric pupils and can be associated with cystoid macular edema (CME) (Irvine-Gass CME).[4,][5] Iliff[6] first reported visual improvement after surgical section of such vitreous bands to the wound. He coined the term vitreous-tug syndrome; although no evidence was given that tugging on the vitreous body was, in fact, present or responsible for the visual loss.
Katzen, Fleischman, and Trokel[7] first reported the use of the Nd:YAG laser to lyse strands of vitreous to cataract wounds in their series. Vision improved by variable amounts in all 14 patients treated. However, the presence of CME was judged clinically, and the results of fluorescein angiography before and after laser treatment were not reported for 13 of the eyes.
Because of the unpredictable natural history of aphakic CME, with erratic response to anti-inflammatory agents and frequent spontaneous improvement,[8,][9] small and controlled series cannot unequivocally prove the efficacy of a given technique. However, my clinical experience has confirmed a high rate of visual improvement after anterior segment vitreolysis, particularly in favorable cases.[10] In that series of 29 patients, 22 of the patients had fluorescein angiographic confirmation of the presence of CME before laser treatment. The interval between cataract extraction and treatment averaged 10 months, with a range of 1–42 months; average follow-up after laser vitreolysis was also 10 months, with a range of 3–27 months.
The change in best-corrected Snellen acuity is shown in Figure 52-3. No patient had loss of vision after laser vitreolysis. The visual acuity in 16 of the 29 patients (55%) improved by two or more lines, with stable acuity following treatments. Five (17%) patients’ vision improved by at least two lines, but they experienced ongoing fluctuation of acuity. Vision in eight patients (28%) showed less than two lines of improvement. Of these eight patients, two had progressive maculopathy in addition to the CME (one had an epiretinal membrane and one had progressive diabetic maculopathy), two had severe glaucoma with loss of central vision in addition to the CME, and two had persistent CME. Two other patients were lost to follow-up without documentation of the basis for persistent unimproved acuity. Of note, patients who did not respond to vitreolysis had the poorest pretreatment visual acuity measurements.
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Figure 52-3 Scattergram of visual acuity level before and after Nd:YAG laser vitreolysis. Points above the diagonal line represent improvement. |
Postlaser fluorescein angiography was performed on nine eyes. Three eyes showed complete resolution of the CME, two showed improvement but persistent leakage, one showed no improvement in the appearance of the fluorescein angiographic leakage but still experienced improved acuity, and three had persistent CME and less than two lines of visual improvement.
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Techniques for anterior vitreolysis
Preoperative assessment
The evaluation and medical treatment of CME are reviewed in detail in Chapter 54. A comprehensive examination including fluorescein angiography should be performed to establish a definitive diagnosis of CME.
Small vitreous strands may be missed on casual examination. The strand is usually best seen on slit-lamp examination with a narrow slit beam in a darkened room. Careful gonioscopy may be necessary to visualize the strand, particularly if the vitreous enters the anterior chamber through the area of a peripheral iridectomy. The most favorable cases for Nd:YAG laser vitreolysis are those with relatively discrete strands under tension. Broad bands are most difficult to fully transect. Amorphous vitreous herniation is extremely difficult to cut with a laser approach. In general, the larger the amount of vitreous involvement, the more consideration should be given to pars plana vitrectomy for definitive removal of all pathologic vitreous.
Pupillary distortion may be subtle. Figure 52-4A shows mild peaking of a pupil, indicating a vitreous strand coming around the pupil. After vitreolysis, less peaking is present, although some permanent change has occurred in the sphincter, preventing complete rounding of the pupil, as seen in Figure 52-4B. Permanent changes in the iris stroma are frequent in cases of long duration. Figure 52-5 shows the decreased but persistent oval shape of the pupil after lysis of a vitreous strand. The iris stroma is partially depigmented locally, perhaps indicating chafing of the iris by the vitreous strand. The vitreous band may distort the pupil in several ways, depending on the angle, direction, and number of vitreous strands under tension. Figure 52-6 shows a “hammock” effect by two separate strands.
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Figure 52-4 A, Fine vitreous strand caused mild peaking of the pupil (arrow). Gonioscopy showed a fine vitreous strand to the wound. B, After laser vitreolysis, less peaking is present, but chronic change in the sphincter prevents a completely normal pupillary contour. |
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Figure 52-5 A, Eccentric pupil caused by a vitreous strand. B, After vitreolysis, depigmentation of the underlying iris stroma, present before the laser treatment, is more readily seen (arrow), and the pupil remains partially distorted. |
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Figure 52-6 Pupillary distortion caused by two separate strands of vitreous to the wound (arrows). The pupil became round after treatment. Despite CME of 57 months’ duration, vision improved from counting-fingers level to 20/50. |
Preparation of the patient
The procedure should be explained beforehand and informed consent obtained. The patient should be told that the procedure often requires more than one session.
When the vitreous strand or band passes through the pupil, treatment is often facilitated by administration of pilocarpine 2% every 10 min for three or four drops preoperatively. Inducing stretch of the vitreous through miosis facilitates identification of the strand. Moreover, release of tension when the laser transects the strand is shown more definitively.
Procedure
Figure 52-7 illustrates the three most common configurations of vitreous to the wound: (1) a small discrete strand, (2) a broad band, and (3) a band with either adhesions to the iris or iris entrapment behind the band.
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Figure 52-7 A, A narrow vitreous strand to a cataract wound. The inset shows possible laser pathways for vitreolysis: (1) a gonioscopic approach, directed at the cataract wound – the location at which the vitreous strand is often the most discrete; (2) a direct approach near the limbus; (3) a direct approach in the region of the collarette; and (4) a direct approach at the pupil. This last approach is rarely successful. B, A broad vitreous band at the wound. C, Iris pulled upward in a tentlike configuration and entrapped by the vitreous incarceration in the wound. |
The laser can be directed at a vitreous strand in four general areas (inset, Figure 52-7A). The most reliable landmark during vitreolysis is the cataract wound because the vitreous band or strand has to terminate at that location. The cataract wound is visualized with a gonioscopy lens (pathway 1 on the figure), and the laser can be fired at the wound area with a reasonable chance of successful vitreolysis. Because of the contact lens and mirror optics, the energy settings are usually in the 6–12mJ range to obtain adequate cutting power. The disadvantages of this technique include the requirement of a gonioscopy lens, which involves some extra manipulation and positioning requirements, and the subsequent commitment to use a contact lens for the completion of the treatment session, even if a different approach is needed later in the session, because of the application of gonioscopy fluid to the cornea.
If the cornea is clear near the limbus and a vitreous strand can be visualized with some clearance from the iris stroma, direct cutting without a contact lens or with a peripheral button Abraham lens may be successful along pathway 2 (see Figure 52-7). Usually 4–8mJ is required. In the course of dozens to hundreds of shots along this pathway, considerable pigment may be liberated from the underlying iris stroma, which will ultimately obscure the surgeon's view. Misfocused shots can cause local damage to the underlying or overlying stroma.
Occasionally the use of pathway 3 (see Figure 52-7), directed at the vitreous passing over the iris collarette, can be helpful. This is particularly true when the vitreous has formed adhesions to the collarette, pulling it forward in a tentlike formation. Close proximity of vitreous and iris makes damage to the underlying iris stroma likely, but this may be clinically tolerable.
The use of pathway 4 (see Figure 52-7), directed at the vitreous as it passes around the pupil, is tempting but rarely successful. Vitreous traction components are poorly defined as they come around the pupil. The shock wave is ineffective at rupturing vitreous strands except directly at the laser focal point. Firing the laser immediately adjacent to the pupillary border inevitably causes low-grade capillary hemorrhage, as well as the release of pigment, obscuring further visualization of the area.
Successful treatment releases the tension and converts a discrete strand or band to an amorphous gelatinous appearance. The observation of a change and any iris deformation is the best indicator of a successful release of tension. Hundreds of shots over several treatment sessions may be necessary to cut a large band.
Postoperative care
Strong topical steroids such as prednisolone acetate 1% or dexamethasone 0.01% are given four times daily until visual improvement occurs, typically in 2 to 3 months. Topical nonsteroidal anti-inflammatory drugs may well be of further benefit alone or in conjunction with topical steroids. Typically, ketorolac or diclofenac drops are administered four times daily.
Intraocular pressure elevation following vitreolysis has not been well documented. A drop of a beta-blocker or brimonidine at the time of treatment probably provides adequate prophylaxis if desired.
In recalcitrant cases, the addition of a systemic nonsteroidal anti-inflammatory drug can be considered.
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“Prophylactic” vitreolysis
With the availability of laser vitreolysis, the surgeon may treat vitreous strands to the wound in the absence of CME in an effort to prevent its later development. Only a large, long-term randomized treatment trial can scientifically determine the usefulness of this approach, and such a study is unlikely. Certainly, some patients with vitreous strands to the wound never acquire CME.
In patients with vitreous to the wound and good visual acuity, a baseline fluorescein angiogram is recommended to document the macular status. If CME is detected, laser vitreolysis is probably indicated even in the presence of good acuity. If visual loss later develops in conjunction with the new onset of CME, the baseline angiogram will be a useful reference to further support therapeutic intervention.
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Coreoplasty
The Nd:YAG laser can cut through iris stroma or the pupillary sphincter to open an occluded visual axis. Indications for coreoplasty including pupillary enlargement for restoration of vision or improvement of the fundus view for examination and treatment. Synechialysis can also affect a pupillary configuration, as discussed in the next section.
Figure 52-8 illustrates a case in which the pupil became updrawn after intracapsular cataract extraction many years earlier. The upper lid covered the pupil. Unless the lid was elevated, vision was limited to counting fingers. The Nd:YAG laser cut through the sphincter with only a localized, self-limited hemorrhage. Vision improved to 20/70 and was limited only by pre-existing maculopathy.
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Figure 52-8 A, Updrawn pupil after intracapsular cataract extraction. B, Immediately after sphincterotomy, a candle wax-like trickle of blood was seen clotted at the inferior margin of the sphincterotomy (arrow). A light reflection from the lid margin gave an appearance similar to hypopyon (arrowhead), but no gross hemorrhage or inflammation occurred. C, One week later, the clot had cleared, and the central cornea was in the optical axis. |
In Figure 52-9, postoperative inflammation has caused nearly complete seclusion of the pupil over a posterior-chamber IOL (PC IOL). Dense associated fibrosis was present with thickening of the iris stroma. The pupil was successfully enlarged by 6mJ pulses directed through a central button Abraham lens with a resultant improvement in acuity from 20/80 to 20/30.
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Figure 52-9 A, Nearly total seclusion of the pupil secondary to postoperative inflammation after extracapsular cataract extraction with posterior chamber intraocular lens implantation. B, Coreoplasty with the Nd:YAG laser resulted in little improvement superiorly, inferiorly, and nasally (to the right). However, in the temporal zone, to the left, the sphincter was successfully transected, and a clear visual axis was restored. |
Technique
Preparation of the patient
In addition to a comprehensive eye examination and informed consent, information regarding the presence of bleeding abnormalities must be specifically elicited in the history because clotting abnormalities increase the risk of a large hyphema.
Preparatory thermal iris photocoagulation with an argon laser has not been necessary or helpful in most cases. Very heavy and extensive iris coagulation is necessary to prevent bleeding when the pulsed Nd:YAG laser is subsequently used. The pressure wave after optical breakdown radiates over several millimeters with enough shearing force to cause a capillary oozing. Thus, it is difficult to eliminate bleeding without widespread intense preparatory coagulation. An exception to this principle is a visible blood vessel whose patch cannot be avoided; it would be folly to cut such a vessel with the Nd:YAG laser without prior photocoagulation. Patients in whom preparatory laser coagulation has been performed generally state that the photocoagulation is more painful than the photodisruption.
Procedure
The is usual setting is 6–10mJ. Numerous shots are required to cut across 3–5mm of sphincter and stroma.
The sphincter is the most difficult region to cut and, with the minor arterial circle, the most prone to hemorrhage. If the surgeon starts at the pupil and cuts across the sphincter first, gross hemorrhage and free red blood cells and fibrin in the anterior chamber may prevent completion of the treatment in one session. To avoid significant hemorrhage until nearly the end of the session, the treatment should begin in the peripheral iris stroma and progress toward the sphincter and pupil. Figure 52-10 illustrates a sequential sphincterotomy.
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Figure 52-10 Technique for Nd:YAG laser sphincterotomy. A, Treatment is begun in the peripheral iris stroma. B and C, Progressive cutting is made toward the iris sphincter. D, Sphincter is cut last so that bleeding is minimized for as long as possible to increase the chance of completing the treatment in one session. |
If bleeding begins without clotting and does not cease rapidly, pressure should be applied to the globe through a contact lens, if one is being used, by a finger through the eyelids, or with a cotton-tipped swab applied to the globe. Pressure adequate to stop the bleeding is maintained for several minutes until effective iris intravascular coagulation has time to occur.
Because the damage zone from optical breakdown (“plasma growth”) occurs backward along the beam path toward the Nd:YAG laser source, it is possible to perform sphincterotomy and coreoplasty over a PC IOL without damaging the underlying lens. However, it is not advisable to perform this procedure in a phakic patient. The pressure wave generated can rupture the anterior capsule of the natural crystalline lens, inducing immediate cataract formation.
Postoperative care
A strong topical steroid (typically prednisolone acetate 1% or dexamethasone 0.1%) is given four times daily, initially, with the dosage tapered as inflammation subsides. Cycloplegia is usually unnecessary. Intraocular pressure elevation is monitored and treated appropriately.
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Synechialysis
Localized synechiae with associated pigment may be broken by photocoagulation with the argon laser. Generally, however, the Nd:YAG laser is more successful than the argon laser in synechialysis because pigmentation of the target is not required and forceful rupture of adhesions can be achieved.
The most common synechiae are to the anterior or posterior capsule, or both. Often a tag of anterior capsule, such as is typically present after a can-opener anterior capsulotomy, adheres to the underside of the iris. As progressive fibrosis and adhesion between the anterior and posterior capsule occur, the iris adhesion is brought posteriorly. This process can exert sufficient force to bring the iris sphincter around the edge of a PC IOL, leading to iris capture of the IOL optic. In Figure 52-11A the iridocapsular adhesion has exposed the superior edge of the PC IOL. This is more evident after dilation. The adhesion is frozen and the posterior capsule in that area ruptured through the application of 2mJ shots. Following treatment (Figure 52-11C), the iris sphincter is back in proper position anterior to the PC IOL.
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Figure 52-11 A, Iris capture of a posterior-chamber intraocular lens (IOL) secondary to iridocapsular adhesions in an undilated patient. B, Adhesion of the iris to the anterior capsular edge is seen clearly after dilation. C, IOL capture is released, and the pupil becomes round after Nd:YAG laser capsulotomy releases the iridocapsular adhesions. |
Another cause of iridocapsular adhesion is a retained fragment of anterior capsule that becomes incarcerated in the cataract wound. The appearance will simulate a vitreous strand to the wound as shown in Figure 52-12A. Careful examination will disclose a typically grayish membrane resulting from fibrosis of the epithelial cells on the anterior capsule, distinctly different from the appearance of a vitreous strand. After dilation, the capsular origin can be seen (Figure 52-12B). The capsular fragment is disrupted with the laser at approximately 2–3mJ if the laser is used and approximately 6mJ if the laser is used gonioscopically. Extra energy is needed because of the thickened fibrotic nature of the capsule.
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Figure 52-12 A, Iridocapsular adhesion simulating pupillary distortion seen with vitreous incarceration in the wound. B, After dilation, the iridocapsular adhesion is better seen (arrow). C, After lysis of the anterior capsular fragment, improvement in the pupillary position is seen compared with the preoperative photo (A), but the iris distortion continues to expose the edge of the intraocular lens optic, giving glare symptoms. D, After gonioscopic application of Nd:YAG laser pulses to the iridocapsular adhesions posterior to the iris, the pupil becomes central, and the glare symptoms are resolved. |
If the capsular fragment is not disrupted within several months postoperatively, however, additional adhesions may form because of the proliferation of the cells present on the anterior capsule fragment. In one case, shown in Figure 52-12C, the pupillary position has improved with photodisruption of the capsule strand incarcerated in the wound, but the pupil remains partially eccentric. The edge of the PC IOL is exposed and a source of functionally significant glare for the patient. This was addressed with further Nd:YAG laser pulses to the epithelial pearl adhesion underlying the iris superiorly. This succeeded in further freeing the sphincter and resulting in a nearly round pupil (see Figure 52-12D).
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Removal of the intraocular lens precipitates
Inflammatory precipitates on the IOL surface are not usual. They may consist of both pigmented and nonpigmented, relatively round precipitates similar in appearance to keratic precipitates or the inflammation may cause the deposition of a more fibrinous gray sheet.
In some cases, these precipitates will respond to appropriate anti-inflammatory therapy. In some cases, however, visually significant precipitates will remain after the inflammation is quiet.
As shown in Figure 52-13A, a mixture of localized dense inflammatory precipitates and a sheetlike precipitate remain after a severe postoperative inflammation. Marked clearing of the IOL optics is evident in Figure 52-13B, following Nd:YAG laser therapy.
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Figure 52-13 A, After complicated extracapsular cataract extraction with posterior-chamber intraocular lens (IOL) implantation and prolonged postoperative inflammation, fibrinous and cellular debris persist on the anterior IOL optic. B, Nd:YAG laser photodisruptive pulses have cleared most of the debris from the IOL surface. |
To remove IOL precipitates, the Nd:YAG laser is set at an energy level adequate to create optical breakdown in the aqueous. This is typically about 2–3mJ. The Nd:YAG laser aiming beams are first focused on the anterior IOL surface. The laser is then slightly defocused by withdrawing the laser slightly toward the beam origin and away from the beam target. The abrupt pressure wave generated by the subsequent optical breakdown in front of the IOL precipitate liberates inflammatory debris into the aqueous humor, leaving a cleaned IOL.
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Anterior capsule
The lens anterior capsule becomes hazy postoperatively because of the epithelial cells present on the inner surface of the anterior capsule. Retained anterior capsule in the pupillary zone will invariably become opaque. Fortunately, the retained capsule does not strongly adhere to the underlying IOL.
In Figure 52-14A, a large remnant of anterior capsule remained after implantation of a PC IOL and significantly opacified. The pupillary zone was cleared with Nd:YAG laser photodisruptive pulses of 2–3mJ. These pulses were applied beginning in the upper left corner and were then carried in the direction of the lower right corner (Figure 52-14B). The capsular membrane was not fully liberated but rather was left adherent at the lower right to curl up on itself. Damage to the underlying PC IOL is avoided by focusing on the anterior capsule and then withdrawing the laser focus slightly anterior to the target. The propagation of the laser plasma is toward the laser source. Accordingly, the damage to the underlying IOL can be avoided as long as the photodisruptive optical breakdown is not focused within the IOL itself.
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Figure 52-14 A, Anterior capsule was inadvertently retained after posterior-chamber intraocular lens (IOL) implantation. Opacification of the anterior capsule occurred rapidly. B, A window has been cut in the anterior capsule with the Nd:YAG laser, with a small amount of the anterior capsule remaining attached in the lower right to avoid a free-floating capsular remnant in the anterior chamber. No damage has occurred to the anterior IOL surface. |
Contracture of a continuous curvilinear capsulorrhexis may cause progressive blockage of an initially clear pupillary zone. This may be due to eccentric contracture of an anterior capsule, as shown in Figure 52-15A, or a more symmetric contracture, as shown in Figure 52-16A. This “capsule contraction syndrome”[11] or “capsular phimosis syndrome” is seen more commonly when the diameter of the original cataract surgical capsulorrhexis is 4mm or smaller. It is attributed to contracture of the structurally strong round anterior capsule opening by the lens epithelial cells that have undergone myofibroblastic differentiation. In addition to causing pupillary obstruction, the capsular contracture stretches the peripheral zonules, with the risk of frank rupture of the zonules and potential weakening of the IOL support. Capsular contracture is best avoided by keeping the diameter of continuous curvilinear capsulorrhexis to 5mm or greater.
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Figure 52-15 A, Contracture of the anterior capsule inferiorly has nearly occluded the optical zone. B, Nd:YAG laser cutting of the inferior capsule adhesion restores an adequate visual axis. |
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Figure 52-16 A, Symmetric contracture of the anterior capsulorrhexis leaves an inadequate visual axis. B, Photodisruption of the anterior capsulotomy edge restores an adequate visual axis. |
As soon as the capsular contracture syndrome is recognized postoperatively, Nd:YAG laser photodisruption of the capsular margin should be undertaken. This will prevent further contraction of the capsule because the disrupted anterior capsule no longer has mechanical integrity. In addition, the pupillary zone is clear of the opaque capsule.
The technique typically consists of 2–3mJ pulses at the edge of the capsulorrhexis, transecting the round capsulorrhexis edge into at least four quadrants. The capsule will then contract and eventually resume a relatively round appearance with a much larger opening (see Figure 52-16B).
Damage to the underlying PC IOL is avoided by deliberate anterior defocusing of the laser beam, as described earlier, for removal of the IOL precipitates and opening of retained anterior capsule.
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Retained cortical material
Occasionally, cortex is retained postoperatively. It may be unrecognized initially or may be deliberately left because of a defect in the posterior capsule or a difficult-to-reach location, particularly under the incision. Cortex will become hydrated in the hours after surgery, swelling and loosening its position. Occasionally, on the day after surgery the visual axis has been occluded by such hydrated retained cortical material (Figure 52-17A).
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Figure 52-17 A, Retained cortex is hydrated but trapped behind the posterior chamber intraocular lens optic. B, Nd:YAG laser pulses have disrupted the retained cortex in the pupillary zone. |
Retained cortex may slowly resorb, but this process is particularly slow when the cortex is trapped between the posterior capsule and the PC IOL anteriorly. With essentially no aqueous turnover, the gradual clearing of this material can take a number of months. Moreover, rather than clearing fully, the retained material may slowly become a dense fibrotic sheet that is difficult to open with laser techniques and may require more invasive surgery.
In such a case, the hydrated opaque cortical material can be liquefied with photodisruptive laser pulses. A minimal amount of laser energy is used, just adequate to cause optical breakdown within the cortical material. A typical amount of energy would be 2mJ. The pressure wave from Nd:YAG pulses within the cortex will emulsify the hydrated cortex, creating an appearance of a more uniform lens “milk.” Within 24h, this more liquefied material will usually clear, restoring a good visual zone (see Figure 52-17B).
The rapid liberation of lens protein through photodisruption may cause secondary inflammation and pressure elevation. Prophylactic antiglaucoma medical therapy is indicated, as is close monitoring of the patient. The surgeon should be prepared to surgically irrigate the retained cortical material if a clinically intolerable level of inflammation or pressure elevation occurs.
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Intraocular lens repositioning
In rare circumstances, Nd:YAG laser photodisruption can be used to manipulate the position of an IOL. The pressure wave from optical breakdown can shift an IOL optic if the optic is sufficiently mobile.
One special case is illustrated in Figure 52-18A. A previously well-centered ciliary sulcus-fixated PC IOL became captured in the pupil after pupillary dilation. The pupil could not be redilated beyond the border of the IOL optic. Mechanical manipulation of the IOL optic by placing the patient in the supine position or with pressure of a cotton-tipped applicator over the ciliary sulcus failed to cause the IOL optic to shift posteriorly.
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Figure 52-18 A, Iris capture of the optic of a posterior-chamber intraocular lens (IOL) (arrow). A single 6mJ pulse focused at an area just anterior to the lens surface, approximately 1mm centrally from the optic edge (arrowhead), retropulsed the optic behind the iris. B, IOL is now in proper position behind the iris. |
A 6mJ pulse from an Nd:YAG laser was then applied to the peripheral edge of the IOL. The laser was focused just anterior to the anterior IOL surface. This anterior pressure wave caused the IOL optic to shift posteriorly, just behind the pupillary sphincter. The sphincter was then constricted with pilocarpine, successfully maintaining the PC IOL in the posterior chamber (see Figure 52-18B).
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Conclusions
Nd:YAG laser photodisruption allows a surgeon to effectively reach inside the eye with a pair of microscissors delivered on a beam of light. In rare circumstances, photodisruptive laser energy can be constructively used to push and cut. Photodisruption, therefore, gives the surgeon a range of additional options for the correction of a wide range of complications following cataract surgery.
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References
[1]. Shaffer R.N.: The role of vitreous detachment in aphakic and malignant glaucoma. Trans Am Ophthalmol Otolaryngol 1954; 28:217-231.
[2]. Shaffer R.N.: A suggested anatomic classification to define the pupillary block glaucomas. Invest Ophthalmol 1973; 12:540-542.
[3]. Epstein D.L., Steinert R.F., Puliafito C.A.: Neodymium-YAG laser therapy to the anterior hyaloid in aphakic malignant (ciliovitreal block) glaucoma. Am J Ophthalmol 1984; 98:137-143.
[4]. Irvine S.R.: A newly defined vitreous syndrome following cataract surgery. Am J Ophthalmol 1953; 36:599-619.
[5]. Gass J.D.M., Norton E.W.D.: Cystoid macular edema and papilledema following cataract extraction. Arch Ophthalmol 1966; 76:646-661.
[6]. Iliff C.E.: Treatment of vitreous tug syndrome. Am J Ophthalmol 1966; 162:856-859.
[7]. Katzen L.E., Fleischman J.A., Trokel S.: YAG laser treatment of cystoid macular edema. Am J Ophthalmol 1983; 95:589-592.
[8]. Gass J.D.M., Norton E.W.D.: Follow-up study of cystoid macular edema following cataract extraction. Trans Am Acad Ophthalmol Otolaryngol 1969; 73:665-682.
[9]. Jacobson D.R., Dellaporta A.: Natural history of cystoid macular edema after cataract extraction. Am J Ophthalmol 1974; 77:445-447.
[10]. Steinert R.F., Wasson P.J.: Neodymium:YAG laser anterior vitreolysis for Irvine-Gass cystoid macular edema. J Cataract Refract Surg 1989; 15:304-307.
[11]. Davison J.A.: Capsule contraction syndrome. J Cataract Refract Surg 1993; 19:582-589.