Laser Retinopexy
Alan R. Hromas
Laser retinopexy refers to the use of photocoagulative laser in an attempt to halt the progression of retinal pathology threatening symptomatic retinal detachment. Treatment involves the application of confluent individual laser burns to demarcate an area of concern, with the goal of inducing a chorioretinal adhesion and thus preventing the start or progression of retinal detachment. This may include treatment of retinal flap tears (“horseshoe tears”), atrophic retinal holes, degenerative peripheral changes such as lattice degeneration, or subclinical peripheral retinal detachments.
The causative role of retinal breaks in retinal detachment was first asserted by Jules Gonin in 19181 and led to the treatment of retinal detachments with ignipuncture. Nearly 30 years later, Gerhard R.E. Meyer-Schwickerath introduced the concept of photocoagulation for therapeutic purposes within the eye. As applied to retinal breaks, he hypothesized that the chorioretinal scarring produced by focused light damage to the retina could prevent the accumulation or spread of subretinal fluid by effectively “tacking the retina down.” After initially performing treatment using focused rays from the sun, he worked with Zeiss to develop the powerful xenon-arc coagulator. In the ensuing 30 years, the xenon-arc coagulator was gradually replaced with the laser technology that remains the most common mode of treatment today.2 While trans-scleral cryotherapy remains commonly used for certain situations, for many surgeon’s, the associated discomfort, inflammation, and increased rate of proliferative vitreoretinopathy3 limit its use relative to laser.
There are many types of lasers employed in retinal applications. Currently, the most popular are green argon (514 nm) and frequency doubled neodymium yttrium aluminum garnet (Nd:YAG) (532 nm), and yellow krypton (568 nm) and dye (577 nm) lasers. These wavelengths lie within the peak absorption range for the tissues being treated, namely the pigmented and vascular structures of the retinal pigment epithelium and choroid.4 Yellow wavelengths are believed to penetrate more effectively through nuclear sclerotic lenses.
Laser spots generate a controlled thermal effect ultimately resulting in chorioretinal scarring and adherence of the neurosensory retina to the underlying tissues, thus its usefulness in decreasing the risk of retinal detachment in patients with retinal breaks.
INDICATIONS
Key Indications
Acute symptomatic retinal tear (“horseshoe tear”)
Retinal dialysis
Traumatic retinal breaks
Peripheral or asymptomatic retinal detachment
Lattice degeneration, atrophic holes, or other peripheral pathology that has significant risk of progression to retinal detachment in the surgeon’s opinion
Studies of the natural history of peripheral retinal defects have refined our knowledge regarding which retinal lesions confer the greatest risk of retinal detachment and thus require treatment.5,6 Most acute, symptomatic flap or horseshoe tears are a consequence of posterior vitreous detachment (PVD) (Figure 21.1). A PVD is a natural, degenerative consequence of aging; complete PVD is defined as the separation of the posterior hyaloid from the optic nerve head. The process of PVD often produces patient symptoms of “flashes and floaters,” and it has been estimated that retinal breaks occur in up to 10%-15% of patients with symptomatic PVD. Untreated breaks have been estimated to progress to clinical retinal detachment in up to 50% of cases, and thus an acutely symptomatic horseshoe tear is a clear indication for prophylactic treatment.7
Although acute flap tears are the classic cause of rhegmatogenous detachment, other retinal defects may also lead to detachment. Atrophic retinal holes are a degenerative thinning of the peripheral retina and often occur in conjunction with lattice degeneration. Operculated retinal breaks represent flap tears wherein the flap has been avulsed, thus reducing active traction on the retina. Observations with regard to the natural history of such lesions have shown that many never progress to detachment over a lifetime of monitoring, and thus the routine treatment of such lesions is generally not performed. Treatment can be considered on a case-by-case basis; for instance, documented accumulation of subretinal fluid around an atrophic hole is a reasonable situation to treat.
 FIGURE 21-1 Retinal tear. |
Retinal dialysis (separation of the neurosensory retina at the ora serrata) generally occurs as a result of significant blunt trauma to the eye. In some cases, dialysis may not lead to detachment for several years following the initial injury, but treatment of this and other traumatic retinal breaks is generally recommended due to the relatively high risk of progression.
Asymptomatic retinal defects are commonly found on routine dilated exam and may include the aforementioned flap tears, atrophic holes, operculated breaks, or even subclinical peripheral detachments. Signs of chronicity, such as pigment demarcation, indicate that a particular lesion has remained stationary for months; however, the presence of such pigment does not ensure the lesion will not progress in the future. The presence of subretinal fluid adjacent to a hole or a break (operculated or not) increases the chance of progression.
Lattice degeneration represents defined areas of thinning in the peripheral retina. Patches of lattice are generally roughly oval shaped and characterized by an overlying pocket of liquified vitreous, with especially adherent vitreous at the border of the lesion. Due to the abnormal vitreoretinal adherence, lattice is prone to tearing along its border, usually during the process of PVD. These lesions thus increase the risk of retinal detachment. There is no clear consensus with regard to whether prophylactic treatment of lattice is warranted.8 The author generally only prophylactically treats lattice in cases that are especially high risk: Those patients with a personal history of retinal detachment in the contralateral eye or those with a strong family history of detachment.
CONTRAINDICATIONS
Key Contraindications
Media opacity preventing clear view of posterior segment
Patient inability to cooperate with treatment
Performing in-office laser retinopexy involves some degree of patient cooperation. Though the procedure is relatively safe with an adequate view and a stationary patient, sudden eye or bodily movements during the process of treatment can risk inadvertent laser to important structures (e.g., the macula and optic nerve). In patients who are too young, invalid, intoxicated, or exhibiting dementia, treatment may best be performed with laser indirect ophthalmoscopy (LIO) in the operating room under sedation. Ensuring adequate anesthesia helps with cooperation.
Performing safe laser retinopexy requires an adequate view of the posterior segment. In acute retinal breaks associated with PVD, vitreous hemorrhage is often present, which can make the view difficult. Other conditions such as corneal opacities, cataract, or inadequate mydriasis may be compounding factors.
It should be noted that in cases of acute PVD associated with vitreous hemorrhage, the risk of an underlying retinal break is high.9 If the view is inadequate to exclude the presence of an underlying break, B-Scan ultrasound should be performed to exclude any clear tear or detachment. The presence of a clear retinal detachment or a break that is untreatable due to media opacity is an indication for urgent pars plana vitrectomy,10 with the goal of treating or halting any concerning lesion prior to it progressing to a “macula off ” status and irreversible vision decrease. If B-Scan does not demonstrate a break or detachment, options include close monitoring (every two to three days) with repeat B-Scans as necessary to allow for some clearing or proceeding with pars plana vitrectomy to clear the visual axis and treat any underlying pathology.
INFORMED CONSENT CONSIDERATIONS
Key Informed Consent Adverse Events
Inadvertent laser damage to optic nerve or macular area with resulting scotoma
Symptomatic visual field defect
Discomfort during the procedure
Progression of retinal detachment despite treatment
Subsequent development of symptomatic epiretinal membrane
Informed consent should include a description of the procedure to be performed, as well as the purpose, in plain language. For instance, “laser treatment to minimize or decrease the risk of progression of retinal detachment.” In addition to the proposed benefits of the procedure, the risks listed previously should be addressed.
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