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

Figure 7: Combined Pars Plana Cataract Extraction and Vitrectomy - Removal of Nucleus and Cortex. In cases of pars plana vitrectomy requiring lens removal, the lens may be removed through the pars plana approach. A phacoemulsifier, aspirating cannula fragmentator or vitreous cutter (O) shown, removes the nucleus and cortex. Infusion is supplied through a separate terminal (I), which will also be used during the vitrectomy stage of the operation. (Art from Jaypee -Highlights Medical Publishers).

Figure 8: Combined Pars Plana Cataract Extraction and Vitrectomy - Removal of the Posterior Capsule. When planning to insert an intraocular lens, an adequate capsular support is preserved, if possible. Some surgeons prefer to remove the posterior capsule as shown, through the pars plana with the vitreous cutter

(O). Following the pars plana vitrectomy, if a decision is then made to implant an intraocular lens, a limbal incision is performed and an intraocular lens is placed over the intact anterior lens capsule. Pars plana infusion terminal (I) is used for both the lensectomy and the vitrectomy. (Art from Jaypee - Highlights Medical Publishers).

Option 2: This technique involves removal of the cataract by phacofragmentation or aspiration through the pars-plana sclerotomies that are used for the subsequent vitrectomy procedure (Figure 7). During this fragmentation or aspiration of the lens, the anterior lens capsule is left intact, but cortical and nuclear aspects of the lens, as well as the posterior capsule, are removed (Figure 8). Then a pars-plana vitrectomy

is performed, and the entire vitreoretinal procedure is completed. If a decision is then made to implant an intraocular lens, a limbal incision is made, and an intraocular lens is placed over the anterior lens-capsule. Then the vitreous cutter is used to make a central opening in the anterior lens-capsule. This technique is welcomed by vitreoretinal surgeons who do not have experience in performing phacoemulsification.

When Not to Implant an IOL

There is general agreement that intraocular lenses should not be placed in eyes with iris or angle neovascularization in eyes with extensive neovascularization of the vitreous cavity, in eyes with extensive retinal detachments, or in eyes with complications occurring during surgery. If there is any doubt, it is better not to implant a posterior chamber intraocular lens and to rehabilitate the patient with a contact lens.

Dislocated Posterior Chamber

IOLs

Postoperative decentration of posterior chamber intraocular lenses occurs in 0.2 to 1.8% of cases. If the patient’s visual acuity is satisfactory treatment usually is not required. Dislocation into the vitreous cavity is much less common but may induce major complications; its frequency appears to have increased in the past few years because of the following reasons:

1)Phacoemulsification has a steep learning curve, and as it becomes more popular, more complications are occurring;

2)Surgeons are becoming more reluctant to place anterior chamber intraocular lenses;

3)Aggressive placement of posterior chamber IOL in the presence of capsular tears has become more common;

4)Silicone - plate IOLs have become more popular.

The posterior chamber implant may dislocate into the vitreous cavity at the time of surgery, or many months after surgery (Figure 9). During cataract extraction dislocation usually results from posterior capsular rupture. Following surgery, complete dislocation usually is observed during the first week after surgery, and may be due to unrecognized posterior capsule rupture, or unstable capsule, although the capsular support may seem to be satisfactory at the time of the initial surgery. Late dislocation is less common and may be due to progressive zonular dehiscence, as in eyes with pseudoexfoliation syndrome, trauma, and asymmetric haptic placement. IOL dislocation may also occur after Nd:YAG laser capsulotomy.

Clinical Findings

After dislocation, a sudden loss of vision, due to the uncorrected aphakia, is noticed by the patient. If the intraocular lens is mobile in the vitreous cavity, the patient may complain of an unusual floater or optical effects. An intraocular lens rarely dislocate completely onto the retinal surface; it usually lies meshed into the anterior vitreous with one haptic still adherent to the capsule or iris. Occasionally the IOL may induce some complications such as retinal detachment or cystoid macular edema secondary to vitreous changes, vitreous hemorrhage, pupillary block, or corneal contact with secondary edema. The presenting

Figure 9: Dislocated Intraocular Lens into Vitreoretinal Cavity. The posterior chamber implant (IOL) may dislocate into the vitreous cavity at the time of surgery, or months later. During cataract extraction dislocation usually results from posterior capsular rupture following surgery. (Art from Jaypee - Highlights Medical Publishers).

Figure 10: B-Scan Ultrasound used in Dislocated Intraocular Lens. If a vitreous hemorrhage or severe corneal edema is present, a B-scan ultrasound (P) should be used to determine the position of the IOL, and to rule out the possibility of a retinal detachment

(RD). (Art from Jaypee - Highlights Medical Publishers).

visual acuity with aphakic correction may be very good, but it is commonly decreased to a moderate degree despite the best spectacle correction. The IOL may be freely mobile in the vitreous cavity, it may be in apparent contact with the retina, or it may have one haptic attached to the posterior capsule, iris, or ciliary body. If a vitreous hemorrhage or severe corneal edema is present, B-scan ultrasound should be used to determine the position of the IOL, and to rule out a retinal detachment (Figure 10).

Management

If the patient’s visual acuity is satisfactory with a contact lens or he or she is able to wear aphakic contact lens, the IOL is not mobile, and there are not associated complications, observation is an option (usually this is not the case). If the dislocated intraocular lens interferes with the vision and visual rehabilitation is needed, or if there are associated complications such as vitreous

hemorrhage, retinal detachment, and cystoid macular edema, surgery has to be considered.

There are three surgical options:

1)IOL removal,

2)IOL exchange,

3)IOL repositioning.

(Editor’s Note: If the IOL is located in the vitreous cavity, the anterior segment surgeon should avoid maneuvers trying to recover the IOL, because of the high risk of complications. The preferred approach is to close the wound, prescribe the usual topical medications, and refer the patient to a vitreoretinal surgeon. Of all the surgical options, it is generally felt that repositioning of the dislocated IOL, provides the most advantages. One of the problems associated with removal, exchange, or repositioning, of a posteriorly dislocated IOL is the potential for causing complications such us vitreous hemorrhage, contusion of the retina, retinal breaks, and retinal detachment. In the presence of complications such as complex retinal detachment, it is better to remove the IOL, to repair the detachment, and later on, make a decision regarding the best approach to visual rehabilitation.

It is recommended to calculate the power of the IOL preoperatively because an IOL exchange may be necessary if the first IOL is damaged during surgical manipulation.

Surgical Technique

If the anterior capsule and zonular rings are mostly intact and appear sufficient for adequate stability, the IOLmay be repositioned into the ciliary sulcus. Repositioning of the IOL into the ciliary sulcus, or over capsular remnant with less than a total of 6 clock hours of inferior capsular support, is not a stable situation. Many of those repositioned IOLs will end up dislocating again. The surgical technique consists of a three port pars plana approach; a vitrectomy is performed; if the vitreous is still attached to the retina, by using high suction with the vitreous cutter, or any other technique, the posterior hyaloid is removed. After the IOL is mobile and free of vitreous adhesion, removal of as much the basal vitreous as possible is recommended. The use of aspiration or perfluoro-n-octane, which is injected between the lens and the retina to float the dislocated IOL, and to protect the retina, has been recommended. These lenses often “skate or glide toward the periphery” on the bubble of perfluoro-n-octane, and its use is not required in most cases. The IOL is grasped with a forceps; silicone lenses are slippery and it may be necessary to use a serrated or diamond-dusted forceps for its manipulation. A wide-angle viewing system is an advantage for this surgical maneuver. The lens is then manipulated into the ciliary sulcus. One haptic may be brought in front of the iris and the other may be positioned in the sulcus, and then, using a bi-manual maneuver, the anterior haptic is brought to

the opposite sulcus (if enough capsular support has been preserved, suturing of the lens may not be necessary).

For removal, or exchange of the IOL, after the IOL is in the anterior chamber, a limbal incision of adequate size, which has been previously prepared, is open and the IOL removed (entirely or cut in half). At this point, for protection of the endothelium, a dense viscoelastic is necessary. If there is another AC or posterior chamber IOL in place, the IOL dislocated in the vitreous cavity may be removed through a pars-plana incision.

If there is not enough capsular support transcleral sutures are necessary. An alternative is to remove and exchange the IOL with an anterior chamber (AC) lens, which may be easier and less traumatic to the corneal endothelium; newer AC IOLs, with flexible open loops, reportedly avoid complications caused by the mechanical side effects of earlier designs. The author prefers scleral suturing techniques with posterior chamber lenses.

Several techniques for IOL suturing have been described. Iris fixation for dislocated PC lenses requires that a suture pass through cornea and iris, around the IOL haptic, and back out through the iris and cornea. Concern regarding iris-mediated chronic inflammation and the technical difficulty encountered during suture placement have led to the development of other techniques.

If the IOL has positioning holes, Hilel Lewis described the following technique: Once the lens has been repositioned onto the residual posterior capsule or, if it is absent, in the ciliary sulcus, the haptics are rotated,

using two reverse sinsky hooks introduced through the horizontal sclerotomies, until they are in the vertical meridian and the holes of the optic in the same meridian as the horizontal sclerotomies. This technique may also be used to engage the haptic of the IOL. Single armed 9-0 prolene suture ends are grasped with intraocular forceps and introduced through the sclerotomies. They are passed through the positioning-holes from posterior to anterior. The sutures are tied to the sclerotomies under scleral flaps previously prepared. This technique requires using perfluorocarbon liquids to place the implant in a convenient positioning for suturing.

A safe technique recommended by W. Smiddy and H. Flynn is by using a disposable 27-gauge needle with a hole located in the bevel, which is threaded with 9-0 polypropilene suture and introduced into the eye, 1 mm posterior to the limbus, in the bed of a partial–thickness scleral flap. Slack is created in the suture along the shaft of the needle by withdrawing it slightly. The IOL haptic is guided through this loop by using the intraocular forceps to grasp the optic. The haptic is captured in the loop as the needle is withdrawn (Figure 11). (An alternative is to use a 9-0 or 10-0 prolene suture threaded retrograde up the bore of a five-eighths-inch 25-gauge needle. The end of the suture, that is not threaded, is retrieved through the hub of the needle. This results in a suture loop). A partial-thickness scleral needle passes in the bed of the scleral flap and allows fixation of the scleral suture. A similar procedure is repeated for the other haptic (Figure 12), unless capsular fixation is possible for the opposite haptic. The scleral flap is then closed with an absorbable suture

Figure 11: Suture connected to a needle passed through  the scleral bed (Escalon Treck Medical). The IOL optic is grasped with the forceps and the haptic is guided through the loop. (Art from Jaypee - Highlights Medical Publishers).

Figure 12: Opposed haptic is then guided through the loop. (Art from Jaypee - Highlights Medical Publishers).

and, if necessary, the vitrectomy is completed through the standard sclerotomies.

When the IOL has to be exchanged, appropriate optic size and haptic to haptic length are critical factors in the selection of an IOL. An optic of 6.5 mm to 7 mm is suggested. An IOL with an overall length of at least 12.5 mm will allow for adequate support in the ciliary sulcus. Using the larger lens is often helpful. However, if there is limited peripheral capsular or Soemmeringring´s support, we prefer to use several types of IOL especially designed for this purpose, which has a hole in the haptics to place the sutures. Once the dislocated IOL has been removed from the eye, a suture needle of Polypropylene is grasped, using a needle holder, and is passed through the bed of a scleral flap at 10-o’clock, 1 mm behind the limbus, and then it is guided to the bore of a bent 27 gauge needle inserted through the bed of the opposite scleral bed previously prepared (Figure 13). In this way the needle is guided outside the eye in a controlled manner. Then, the propylene suture is engaged in the pupillary space with an iris hook and brought outside the eye through the limbal incision (Figure 14). The ends of the suture are threaded through the holes located in the haptics, and are tightened (Figure 15). The IOL is then inserted in the sulcus, and the sutures are pulled, the needle is passed through the partial thickness of the scleral bed and the sutures are tightened; the procedure is repeated in the opposite scleral bed.

At the end of the procedure a careful inspection of the periphery to rule out retinal breaks is recommended.

Complications

Contusion to the retina and retinal breaks may happen during surgical manipulations. Vitreous hemorrhage may occur if the major arterial circle of the iris is pierced inadvertently, during the maneuvers required to suture the IOL. Torque of the IOL may occur. Erosion of the sutures through the conjunctiva also has been reported. To melt the eroded sutures with the argon laser has been recommended. The sutures cannot be removed because the IOL haptics may not be fixed by a scar into place in the ciliary sulcus. Endophthalmitis due to bacterial migration along the transcleral suture has been described. The use of a partial thickness scleral flap to cover the suture knot reduces the risk for this complication. Retinal detachment occurs in about 2%.

Functional Results

The final visual acuity depends not only on pre-operative macular function, but also on complications of the original cataract surgery, such as cystoid macular edema and retinal detachment. With proper vitreo-retinal techniques, excellent visual results and a low complication rate is possible. A post-operative visual acuity of 20/40 or better has been reported between 50% and 94%.

-Cortez, R: Cirugía Combinada Vitreoretinal y de catarata., World Atlas Series of Ophthalmic Surgery

if Highlights, Boyd, BF, Vol IV, 1997; pp. 71-75.

-Wu, L, Garcia, RA: Intraocular lens dislocation. In Phillpotts, B, Fong, D, Charles, S, Brown, L, and Roy, H, Sr (eds):eMedicine Journal, April 26 2001, Vol. 2, N° 4.

-Smiddy WE, Flynn HW Jr. Management of dislocated posterior chamber intraocular lenses. Ophthalmology 1991;98:889-894.

-Smiddy WE, Avery R. Posterior chamber IOL implantation with sub-optimal posterior capsular support. Ophthalmic Surg. 1991;22:16-19.

-Lewis H, Sanchez G: The use of perfluorocarbon liquids in the repositioning of posteriorly dislocated intraocular lenses. Ophthalmology 1993:100;7:105559.

-Lewis, H: Management of Dislocated crystalline and intraocular lenses. In Lewis, H and Ryan, S, eds.:

Medical and Surgical Retina:Advances, Controversies and Management. St Louis, 1994. Mosby, pp 229237.

-Lane, S, Schwartz, G: IOL Exchanges and Secondary IOLs:Surgical Techniques. Focal Points (AAO). Vol XVI, N° 1. March 1998.

-Smiddy, WE, and Flynn, HW Jr.: Posterior Segment Complications of Anterior Segment Surgery

. In Regillo, C, Brown, G, Flynn, Jr., HW, eds: Vitreoretinal Disease. The essentials. New York. 1999. Thieme, pp 567-579.

-Flynn, HW Jr., and Smiddy, WE: Posterior Segment Complications of Anterior Segment Surgery. In Parrish II, Richard K, ed.: The University of Miami, Bascom Palmer Eye Institute. Atlas of Ophthalmology. Boston, 2000. Butterworth-Heinemann, pp. 268-271.

Introduction

The prevalence of myopia in the United States is said to be 25% to 46.4% of the adult population.1-2 In Asian populations these proportions may be much higher and in African and Pacific island groups, much lower. The market for refractive surgery has a very large potential for people with low (less than –5.00 diopters (D)) and moderate myopia (-5.01 to –10.00 D), and most patients fall into one of these two groups.2

Refractive surgery has been accepted for correcting ametropias, however this procedure may lead to complications. Several studies have described the retinal complications of refractive surgery since its early days, and procedures. Hofman et al3, Sanders et al4, and Feldman et al5 have described cases of retinal detachment (RD) after radial keratotomy. Rodriguez and Camacho6 reported 14 eyes (12 patients) which had either asymptomatic or symptomatic retinal breaks, subclinical and clinical rhegmatogenous RD, or both,7 after

Automated Lamellar Keratoplasty (ALK) and7 after radial keratotomy. Rodriguez et al7, Barraquer et al8, and Ripandelli et al9 have reported retinal detachments after clear-lens extraction for myopia correction. Ruiz-Moreno and associates10 reported the results of a clinically controlled study to investigate the rate of retinal detachment after implantation of phakic anterior chamber intraocular lenses. The implantation of a phakic anterior chamber intraocular lens as a correcting procedure for severe myopia was followed by a 4.8% incidence of retinal detachment.

Laser-assistedinsitukeratomileusis(LASIK) has become one of the most popular options for the correction of low to moderate myopia worldwide. 11-12 However, complications including undercorrections, overcorrections, flap displacement, epithelial ingrowth,flapmelting, keratitis, retinal tears, retinal detachments, corneo-scleral perforations, retinal hemorrhages, macular holes, choroidal neovascular membranes, and irregular astigmatism have been reported. 13-25

The objective of this chapter is to review the retinal complications that may occur after refractive surgery with an emphasis on LASIK.

Retinal Detachments

Little has been reported in the literature regarding retinal detachments after LASIK. A Medline search reveals just a few studies.17, 20-24 Ozdamar et al20 reported a case of bilateral retinal detachment associated with giant retinal tear after LASIK. Stulting and associates17 reported a case of rhegmatogenous retinal detachment after LASIK for the correction of myopia. Ruiz-Moreno and coworkers21 reported 4 retinal detachments (an incidence of 0.25%) in myopic eyes after LASIK and a mean best-corrected visual acuity of 20/45 after retinal surgery. Aras et al22 described 10 retinal detachments (an incidence of 0.22%) in myopic eyes after LASIK. Farah and coworkers23 reported four eyes that had early rhegmatogenous retinal detachment within 3 months of LASIK for correction of high myopia. Although no cause-effect relationship between LASIK and retinal detachment can be stated from their study, the authors cases suggest that LASIK may be associated with retinal detachment, particularly in highly myopic eyes.

We have previously reported (Ramirez, and Arevalo et al, The Association for Research in Vision and Ophthalmology Annual Meeting, Fort Lauderdale, FL, May 1998 and Arevalo et al, American Academy of Ophthalmology Annual Meeting, New Orleans, Louisiana, November 1998) our two-year follow up of 29,916 eyes after LASIK for the correction of ametropias (myopes and hyperopes).

The incidence at 24-months of vitreo-retinal pathology in our study was 0.06% including 14 rhegmatogenous retinal detachments (RRD).24 The incidence of RRD after LASIK in our previous studies ranges between 0.04% and 0.05%.24-25

For our latest data analysis (Arevalo JF. The Wilmer Eye Institute’s Current Concepts in Ophthalmology-A Forum for Global Ophthalmic Innovators, Baltimore, MD, April 2007) we reviewed the medical records and obtained follow-up information on all patients in our files with rhegmatogenous retinal detachment (RRD) after LASIK for the correction of myopia between March 1996 to March 2004 at five institutions. A total of 83,938 LASIK procedures (eyes) were performed during the study period (8 years) by five experienced refractive surgeons. The mean age of the patients that had LASIK was 36 years (range: 16-60 years). Patients underwent surgical correction of myopia ranging from -0.75 to -29.00 D (mean: -6.19 D). Patients were scheduled to be seen during the first postoperative day, at 3 months, at 12 months, and yearly thereafter. Patients were followed for a mean of 65 months after LASIK (range: 6-84 months).

Five vitreo-retinal surgeons and 40 eyes (34 patients) that developed RRD after LASIK for the correction of myopia participated in the study (Figures 1 and 2). The clinical findings, frequency of RRD after LASIK, characteristics (fundus drawings of the 40 eyes were evaluated), and surgical outcomes of 38 eyes (two patients refused surgery) are presented. Patients with RRD after LASIK were included in the study independent on the length of follow-up.