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

Final visual acuity (VA) was defined as the best corrected visual acuity at last fol- low-up examination, ranging from 3 to 46 months (mean: 26 months) after vitreo-retinal surgery to repair RRD after LASIK. Laser in situ keratomileusis was performed on patients with no history of prior refractive surgery, keratoconus, prior cataract surgery, proliferative diabetic retinopathy, or collagen vascular disease. Preoperative examinations included a very thorough dilated funduscopy with scleral depression and treatment of any retinal lesion predisposing for the development of a RRD.

We found forty eyes (34 patients) that developed RRD after LASIK for the correction of myopia. Our 34 patients had an average age of 37.8 (16-60) years old, and 66.6% were male. In our series 9% of eyes that developed a RRD had some kind of enhancement after LASIK. No patient had a history of any other ocular surgery after LASIK. The frequency of rhegmatogenous retinal detachments determined in our study is 0.04% (40/83,938).

Rhegmatogenous retinal detachments occurred between 12 days and 60 months (mean: 16.3 months) after LASIK. Eyes that developed a RRD had from –1.50 to –16.00 D of myopia (mean: -8.75 D) before LASIK. Retinal detachments were managed with vitrectomy, cryoretinopexy,scleralbuckling,argonlaserretinopexy, and pneumatic retinopexy techniques. In cases that developed a retinal detachment, a pars plana vitrectomy was performed using an Accurus (Alcon Laboratories, Fort Worth, TX) or a Millennium (Bausch & Lomb Surgical, Claremont, CA) vitrectomy system. Three 1.0 mm-wide sclerotomies were made using a microvitreal (MVR) blade from 2.5 to 3.5 mm posterior to the limbus. The infusion line

was sutured in the infero-temporal quadrant. After vitrectomy, sulfur hexafluoride (SF6) gas was used or 5,000 centistokes (cs) silicone oil (Richard-James, INC., Peabody, MA). A scleral buckling procedure was performed using a circumferential scleral band (Mira 240; Mira, Waltham, MA) sutured with the posterior border located 12 mm posterior to the limbus, and adding any necessary segmental sponges (Mira, Waltham, MA) when needed. Cryoretinopexy was performed using a CTU Ophthalmic Cryo Unit (Keeler, London, England). Argon laser retinopexy was performed using an HGM’s PC EDO argon (only green) laser (HGM, Salt Lake City, Utah) using the indirect delivery system (LIO). Pneumatic retinopexy was performed using the same argon laser (PC EDO) with LIO and sulfur hexafluoride (SF6) gas.

Vitreo-retinal surgery to repair RRD after LASIK was performed at a mean of 56 days (range: 1 day to 18 months) after the onset of visual symptoms. The mean follow up after retinal surgery was 26 months (range: 3 to 46 months) and 38.7% of the 38 eyes (two patients refused surgery) had a final best corrected visual acuity (VA) of 20/40 or better. Final VA was better than 20/200 in 77.4% of eyes. Poor VA (20/200 or worse) occurred in 22.6% of eyes. Reasons for poor VA included the development of proliferative vitreo-retinopathy (PVR),epiretinalmembrane, chronicity of RRD, new breaks, displaced corneal flap, and cataract.

Final VA after RRD surgery improved 2 lines or more in 51.6% of eyes. The anatomic success at final follow-up with one surgery was 87.1%. Three eyes required from 1 to 3 reoperations with pars plana vitrectomy and silicone oil injection (Figure 3) and one eye

required argon laser retinopexy to seal new retinal breaks. The anatomic success at final follow-up including reoperations was 90.3%. Information regarding VA after LASIK and before the development of RRD was available in 30 eyes, 45.8% of eyes lost 2 or more lines of VA.

Retinal Breaks, Posterior

Vitreous Detachment, and

Lattice Degeneration

Fundus drawings of the 40 eyes were evaluated (Figure 2). The mean number of retinal breaks per RRD was 4.3 (range: 0-40),

including 98 holes, 41 horseshoe tears, two retinal dialysis, and one giant retinal tear. In 71.1% of cases retinal breaks were located temporally. The vitreous status was available from 33 of our cases, and 62.9% had posterior vitreous detachment (PVD), and 22.5% of our RRD cases had a retinal break associated to lattice degeneration. In 19.3% of our cases RRD was associated with proliferative vitreoretinopathy (PVR) grade C.

The long interval between the onset of symptomsandRRDsurgerymayberesponsible for some of the factors (including a 19.3% rate of PVR) that contributed to poor final VA in more than 20% of our cases. In some of our patients there may have been some delay in

the referral to the vitreo-retinal specialist due to a belief that the visual symptoms were related to a refractive or corneal problem after LASIK. In addition, other factors related to high myopia (including myopic degeneration and amblyopia) might also influence the final functional results regardless of our high anatomic success rate.

Macular Hemorrhage and

Choroidal Neovascular

Membranes

Few reports have been published regarding macular hemorrhage after LASIK. Kim and Jung26 reported one eye that lost greater than two lines of pre-operative best-corrected vision due to macular hemorrhage. Luna et al27 have reported a case of bilateral macular hemorrhage after LASIK. One day after surgery the patient’s uncorrected visual acuity was in the 20/50 range and by 17 days after surgery his visual acuity had declined to 20/200 range. Fundus examination showed multifocal subretinal macular and posterior pole hemorrhages. Fluorescein angiography showed some macular lesions compatible with lacquer cracks.

Only a few studies can be found regarding choroidal neovascular membranes after refractive surgery. We have described the first case of a choroidal neovascular membrane (CNV) that presented after LASIK.24 A 48 year-old Hispanic hyperopic (+3.50 D OD and +4.00 D OS) man was seen on December of 1997

at our institution because of visual loss OS two years after a LASIK procedure. On examination, visual acuity was 20/400, and biomicroscopy was unremarkable. Dilated funduscopy and fluorescein angiography showed a juxtafoveal CNVM with sub-retinal fluid (Figure 4-A). A pars plana vitrectomy and a temporal retinotomy were performed to remove the CNVM from the sub-retinal space and air was instilled into the vitreous cavity. Topical steroids and cycloplegics were prescribed. Eight months later his visual acuity OS was counts fingers and funduscopy showed a juxtafoveal retinal pigment epithelium defect (Figure 4-B).

Ruiz-Moreno et al have reported an incidence of 0.1% CNV after LASIK and one caseafterphotorefractivekeratectomy(1/5936). The incidence seems to be very low, however the appearance and treatment of CNV was followed by a significant decrease of visual acuity. Choroidal neovascularization is related to myopia itself and its incidence varies from 4 to 11% in patients with high myopia. In addition, lacquer cracks have been found to be associated with CNV in up to 82% of cases with myopia.28 Theoretically, when a break in Bruch’s membrane occurs, it allows invasion of the neovascular complex under the retina. The increase in intraocular pressure (IOP) to levels over 60 mm Hg during suction with the microkeratome suction ring up to 4 mm posterior to the limbus may exert traction and compression posteriorly. In addition, we have to consider that the excimer laser is responsible for a shock wave that is transmitted to the eye. These mechanisms may open the gap in Bruch’s membrane

even more. We believe that in patients with high myopia and lacquer cracks (Figure 5), LASIK should be considered contraindicated and some other method of refractive surgery offered (i.e. phakic intraocular lens).

Macular Hole

Arevalo et al30 described nineteen patients (20 eyes) who developed macular hole after undergoing bilateral LASIK for the correction

of myopia. The macular hole formed at a mean of 12.1 months after LASIK. In 60% of cases the macular hole developed ≤ 6 months after LASIK, and in 30% of cases the macular hole developed one year or more after LASIK. Eighteen out of 19 (94.7%) patients were female. Mean age was 46 years old. All eyes were myopic (mean: -8.9 D). Posterior vitreous detachment (PVD) was not present before and was documented after LASIK on 55% of eyes. A vitrectomy closed the macular hole on the fourteen eyes that underwent

surgical management with an improvement on final best-corrected visual acuity on 13 out of 14 (92.8%) patients (Figure 6). The 20 eyes with full-thickness macular hole after LASIK reflect an incidence of 0.03% (20/55,458). The authors concluded that a macular hole may infrequently develop after LASIK for the correction of myopia, and that vitreoretinal surgery can be successful in restoring vision for most myopic eyes with a macular hole after LASIK.

How could the excimer laser, or the microkeratome, cause a macular hole? What is the pathophysiology? When the suction ring induces an increase in IOP and then is suddenly released, the anterior segment is rapidly drawn into a vacuum chamber with it’s shape changed rapidly, and all structures posterior to the suction ring are also compressed and decompressed in sequence. This type of “trauma” is in some ways analogous to what happens in a closed eye injury. A mechanism for development of peripheral retinal tears or macular disease could be anterior-posterior compression and expansion. The eye elongates along the anterior-posterior axis and the diameter of the globe may increase. At the same time, because the eye is a closed system, the eye is constricted in the equatorial plane (Figure 7A). As the anterior segment is drawn into a vacuum, the lens may be displaced forward along with the

anterior hyaloid. This might accelerate vitreous detachment or cause traction at the vitreous base. When the suction is suddenly released, decompression leads to a dynamic overshoot with equatorial expansion and shortening in the anterior-posterior dimension (Figure 7B). These events may cause acute vitreo-retinal traction at the vitreous base and posterior pole.

In addition, when the excimer laser light ablates tissue, energy is released anteriorly as a plume of ablated tissue and is thrown into the air in front of the cornea. Certainly such a powerful force might also be associated with backward force into the vitreous. Posteriorly, energy is transmitted in the form of a shockwave (Figure 7C). The effect of such shockwaves and posteriorly radiated energy on the vitreous integrity is unknown.

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Corneo-Scleral Perforations

In our series24, two eyes had suffered corneo-scleral perforations with the surgical microkeratome when a corneal flap was being performed (one of them developed a vitreous hemorrhage and the other one later developed a retinal detachment).

A 24 year-old Hispanic myopic (-5.00 D OD and -4.25 D OS) woman was seen on August of 1995 at our institution because of visual loss OD immediately following a LASIK procedure. According to the refractive surgeon, he had omitted to place a spacing plate into the microkeratome when a corneal flap was being performed. An ocular perforation occurred with corneal and iris wounds, loss of the crystalline lens, vitreous loss, and the development of vitreous hemorrhage. We performed a thorough anterior vitrectomy and sutured the corneal and iris wounds with 10-0 nylon. Oral and topical steroids were prescribed. Thirteen months later her visual acuity was 20/25-1 with a contact lens.

In the second case, a 38 year-old Hispanic myopic (-20.00 D OD and -15.00 D OS) woman was seen on May of 1997 at our institution because of visual loss OS following a LASIK procedure. According to the refractive surgeon, a corneal perforation had occurred with the microkeratome when a corneal flap was being performed. She had undergone crystalline lens remnant aspiration and an anterior vitrectomy one week later. On examination, a sutured (10- 0 nylon) corneal wound with Descement folds is seen on biomicroscopy (Figure 8A). Dilated funduscopy did not show details of the retina due to opacities of the media. Di-

A

B

Figure 8 A-B: A) Sutured (10-0 nylon) corneal wound with Descement folds is seen on biomicroscopy. B) Diagnostic B-scan ultrasound shows an inferior retinal detachment (Reprinted with permission from Arevalo et al. Incidence of vitreo-retinal pathologic conditions 24 months after laser-assisted in situ keratomileusis (LASIK). Ophthalmology 2000;107:258-262).

360o circumferential scleral band, endolaser, and SF6. Topical steroids and cycloplegics were prescribed. Three months later she developed a retinal tear in the fellow eye (also treated with LASIK) which was managed with an argon laser retinopexy. Six months later her visual acuity OS was hand motions due

to corneal scarring and a recurrent inferior rhegmatogenous retinal detachment.

Some cases of LASIK induced corneal perforation have been treated by applying a therapeutic soft contact lens with topical antibiotics, oral carbonic anhydrase inhibitors, and eye patching. However, we believe that it is important to mention that LASIK-induced corneal perforations can be very severe and sutures may be necessary. In addition, severe cases may be associated to posterior segment damage as demonstrated in our report.24 The incidence of vitreo-retinal complications (vitreous hemorrhage and retinal detachment after corneo-scleral perforations) during LASIK determined in our study is 0.006% (2/29,916).

We recommend that refractive surgeons be meticulous in properly assembling the

microkeratome to create a corneal flap during LASIK. The use of currently available disposable microkeratomes may help to avoid this complication in the future.

Displacement of Corneal Cap

During Vitrectomy

In one of our cases, a dislocated corneal flap (Figure 9) occurred with corneal epithelial debridement during vitrectomy 69 months after LASIK. A similar case has been previously reported by Chaudhry and Smiddy31. Their case underwent vitreous surgery only 4 months after LASIK.

Displacement of a corneal flap after LASIK is a potentially serious complication. Possibilities include losing the cap, epithelial

ingrowth, interface particles, and striae in the flap (trauma to the flap may affect the final refractive status). Displacement of the corneal flap has been described after corneal epithelial debridement during a scleral buckling procedure, and vitrectomy.

Recommendations for vitreo-retinal surgeons when treating an eye with a history of LASIK include avoiding debridement of the corneal epithelium. However, if it is necessary, start corneal debridement nasally and advance temporally (most cases have a nasal hinge). If a displaced corneal flap occurs, initial management includes repositioning of the flap, followed by patching and topical steroids. Refractory cases may require suture fixation. A bandage contact lens may be useful if striae develop. If striae persist, it is an indication to elevate and reposition the flap.

Final Considerations

Laser-assisted in situ keratomileusis (LASIK) has become the most popular option for the correction of low to moderate ametropias worldwide. The number of patients who have had LASIK is not accurately known. In the US, the market estimate for LASIK procedures is 900,000 per year. We estimate that in Latin-America, LASIK is done in 0.06% of the population per year. At least 80% of those cases are myopes, typically from -0.50 to –10.00 diopters (D). Patients with higher degrees of myopia tend to be corrected now with the aid of phakic intraocular lens or phacorefractive surgery to avoid excessive ablation of the corneal bed by the excimer laser.

The incidence of rhegmatogenous retinal detachment (RRD) in myopes in general is 1 to 3%.32 There is a relationship between the severity of myopia and the frequency of RRD.33-35 Ogawa et al analyzed 1,116 RRD cases and found that myopia was present in 82.16% of them. In myopia higher than –15.00 D the frequency of RRD was 68.6 times higher than for patients with hyperopia.33 In most myopes there is an axial component, and vitreous modifications and peripheral fundus abnormalities in myopic eyes are the major factors that predispose to RRD.34 The Eye Disease CaseControl Study Group reported that an eye with a spherical equivalent refractive error of –1.00 to –3.00 D had a fourfold increased risk of retinal detachment compared with a non-myopic eye; if the refractive error was greater than –3.00 D, the risk was increased 10-fold.35

Is there a cause-effect relationship between LASIK and the development of retinal breaks and detachment, and between LASIK and exacerbation of macular changes associated with myopia? How do we account for the development of vitreo-retinal disease after LASIK? It is important to first state that there is little hard data with which to even attempt to determine if there is any causative relationship. Myopes undergo LASIK in ever increasing numbers and myopes are predisposed to retinal detachment as well as macular hemorrhage and other macular pathologies. It is possible that these abnormalities or exacerbation of these conditions are associated with the LASIK procedure itself. However, they may have occurred anyway. Unfortunately, it is very difficult to do a controlled study.