Retinal Laser Photocoagulation in Peripheral Retinal Degenerations


Type of lesion

Treatmenta

Acute symptomatic horseshoe tears

Treat promptly

Acute symptomatic operculated holes

Treatment may not be necessary

Acute symptomatic dialyses

Treat promptly

Traumatic retinal breaks

Usually treated

Asymptomatic horseshoe tears (without subclinical retinal detachment)

Often can be followed without treatment

Asymptomatic operculated tears

Treatment is rarely recommended

Asymptomatic atrophic round holes

Treatment is rarely recommended

Asymptomatic lattice degeneration without holes

Not treated unless PVD causes a horseshoe tear

Asymptomatic lattice degeneration with holes

Usually does not require treatment

Asymptomatic dialyses

No consensus on treatment and insufficient evidence to guide management

Eyes with atrophic holes, lattice degeneration, or asymptomatic horseshoe tears where the fellow eye has had a retinal detachment

No consensus on treatment and insufficient evidence to guide management


Reprinted with permission of American Academy of Ophthalmology Retina/Vitreous Panel. Preferred Practice Pattern®Guidelines. Posterior Vitreous Detachment, Retinal Breaks, and Lattice Degeneration. San Francisco, CA: American Academy of Ophthalmology; 2014. Available at: www.​aao.​org/​ppp

aThere is insufficient evidence to recommend prophylaxis of asymptomatic retinal breaks for patients undergoing cataract surgery




Table 7.2
Follow-up guidelines in peripheral retinal degenerations
















































Type of lesion

Follow-up interval

Symptomatic PVD with no retinal break

Depending on symptoms, risk factors, and clinical findings, patients may be followed in 1–8 weeks, then 6–12 months

Acute symptomatic horseshoe tears

1–2 weeks after treatment, then 4–6 weeks, then 3–6 months, then annually

Acute symptomatic operculated holes

2–4 weeks, then 1–3 months, then 6–12 months, then annually

Acute symptomatic dialyses

1–2 weeks after treatment, then 4–6 weeks, then 3–6 months, then annually

Traumatic retinal breaks

1–2 weeks after treatment, then 4–6 weeks, then 3–6 months, then annually

Asymptomatic horseshoe tears (without subclinical retinal detachment)

1–4 weeks, then 2–4 months, then 6–12 months, then annually

Asymptomatic operculated tears

1–4 months, then 6–12 months, then annually

Asymptomatic atrophic round holes

1–2 years

Asymptomatic lattice degeneration without holes

Annually

Asymptomatic lattice degenerationwith holes

Annually

Asymptomatic dialyses

If untreated, 1 month, then 3 months, then 6 months, then every 6 months

If treated, 1–2 weeks after treatment, then 4–6 weeks, then 3–6 months, then annually

Eyes with atrophic holes, lattice degeneration, or asymptomatic horseshoe tears where the fellow eye has had a retinal detachment

Every 6–12 months


Reprinted with permission of American Academy of Ophthalmology Retina/Vitreous Panel. Preferred Practice Pattern® Guidelines. Posterior Vitreous Detachment, Retinal Breaks, and Lattice Degeneration. San Francisco, CA: American Academy of Ophthalmology; 2014. Available at: www.​aao.​org/​ppp


Therapeutic efficacy of LPC as a preventive method in different types of peripheral vitreochorioretinal degenerations is 75–100 % according to literature data [30, 31]. The need for retinal LPC in peripheral vitreoretinal degenerations is supported by many publications: the risk of retinal detachment with deferred symptomatic tears’ treatment may reach 30–50 % [32]. The risk of retinal tear and retinal detachment in patients with lattice degeneration and retinal detachment in the fellow eye without preventive laser treatment was 2.5 times higher than in same patients after retinopexy (5.1 % vs 1.8 %, p = 0.0125) [33]. Preventive retinal LPC in aphakic patients with vitreoretinal degeneration reduced the incidence of retinal detachment to 0.33 % of the cases compared to 2 % in the control group [34]. Ora secunda cerclage effectively protects against RRD [26]. LPC and cryotherapy are considered effective methods to prevent retinal detachment [9]. Prophylactic LPC significantly reduces the risk of retinal detachment [10], and many authors consider laser treatment an easy-to-use and convenient treatment method [35].

However, there is an alternative viewpoint, that laser treatment performed in the visible areas of degeneration may increase the invisible vitreoretinal traction and cause new tears and retinal detachment in unsuspected areas, and sometimes the treatment itself should be recognized as a risk factor for RRD [18, 36].

According to most of the foreign and national authors, one should carefully examine each patient and take into account all risk factors before performing a prophylactic treatment in peripheral degenerations. These risk factors include: the presence of symptoms, vitreoretinal traction, tear, and subretinal fluid around the break; localization of lesions, family history of retinal detachment, the state of the fellow eye, refraction, age, gender, patient’s profession; special circumstances, such as aphakia or pseudophakia, posterior capsulotomy due to the secondary cataract, planned refractive surgery. Laser is a useful treatment tool, and it must be used wisely [11, 14].

Performing optical coherence tomography of the retinal periphery may be of great help in determining the risk of RRD, necessity and timing (promptness) of preventive LPC (see Figs. 7.1, 7.2, and 7.3), and in assessing the state of the retina and laser burns in the postoperative period (see Figs. 7.4 and 7.5). OCT in the retinal periphery makes it possible to determine the morphometric parameters (length and height) of the vitreoretinal traction and its changes over time, that allows to refine the indications for retinal LPC. Analysis of OCT data in different clinical types of retinal tears allowed to identify three risk levels according to the probability of RRD development: retinal tears with high risk of RRD, retinal tears with moderate risk of RRD, and retinal tears with low risk of RRD. Below we present examples of three clinical cases, corresponding to different levels of RRD risk.

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Fig. 7.1
Spectral Domain OCT scan (6 mm) in the area of the retinal tear with neurosensory retinal detachment. (a) Color image, (b) Black and white image. Full-thickness retinal tear (crescent) with neurosensory retinal detachment (circle) is seen with its edges thickened (yellow arrow) and containing hyporeflective cavities (criss-cross), and vitreoretinal traction (asterisk) at the edges of the tear


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Fig. 7.2
Spectral Domain OCT scan (6 mm) in the area of the retinal tear with operculum and shallow retinal detachment. (a) Color image, (b) Black and white image. Full-thickness retinal tear (crescent) with flat (slit-like) neurosensory retinal detachment (circle) is seen with hyperreflective operculum (arrow) on the outer surface of the detached vitreous (asterisk); no vitreoretinal traction is seen in the tear area


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Fig. 7.3
Spectral Domain OCT scan (6 mm) in the area of the full-thickness retinal tear. (a) Color image, (b) Black and white image. Full-thickness retinal tear (crescent) is seen with surrounding neurosensory retina (criss-cross) attached to the retinal pigment epithelium; no vitreoretinal traction is seen


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Fig. 7.4
Retinal OCT scan 2 weeks after retinal laser photocoagulation. Localized hyperreflective areas at the level of the pigment epithelium and outer nuclear layer of the neurosensory retina (red arrow pointing at RPE thickening) are seen at laser burns, with photoreceptors and RPE destruction at the edges of these lesions (yellow arrow). The outer plexiform and inner nuclear layers became funnel-shaped (green arrow) in the direction of the retinal pigment epithelium


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Fig. 7.5
OCT image of retinal detachment occurring after the delimiting LPC. Neurosensory retinal detachment reaches laser burns (RPE thickening, red arrow), and its outer layers’ arcuate deformation (green arrow) is formed


First case

A 29-year-old male patient complained of intermittent lightnings and floaters affecting his right eye for 1 week. Ophthalmoscopic exam revealed a tractional tear in the upper-temporal segment of the peripheral retina. OCT scan showed a full-thickness retinal tear with a shallow neurosensory retina detachment and severe vitreoretinal traction (Fig. 7.1a, b). This case represents a high level of RRD risk and is an absolute indication for urgent delimiting retinal LPC on the right eye.


Second case

A 45-year-old male patient came to the ophthalmologist to have glasses prescribed, as he complained of blurred vision while reading. Ophthalmoscopic exam revealed an isolated tear with an operculum floating in the vitreous over the tear in the peripheral retina lower segment of the left eye. OCT scanning showed the full-thickness retinal tear with shallow neurosensory retinal detachment and hyperreflective operculum on the outer surface of the detached vitreous. Vitreoretinal traction is absent (see Fig. 7.2a, b). Taking into account both clinical data (absence of symptomatic complaints) and OCT results, this case illustrates a moderate RRD risk and is a relative indication for retinal LPC. It is recommended to follow changes over time.


Third case

A 59-year-old female patient complained of blurred vision in her right eye for six months. Ophthalmoscopic exam revealed mild cortical cataract and isolated tear in the lower-temporal segment of the retinal periphery. OCT (see Fig. 7.3a, b) revealed the full-thickness neurosensory retinal tear with its edges completely attached to RPE, no subretinal fluid and vitreoretinal traction. This case can be attributed to the third group with a low level RRD risk. There are no indications for urgent preventive LPC, but the patient should be instructed to visit an ophthalmologist in case of any visual symptom. It is recommended to follow changes over time.



Methods of Retinal Laser Photocoagulation


Characteristics of laser radiation are unique: it is highly coherent in time (monochromaticity) and in space (small beam divergence), which allows to focus the light energy on the small diameter spot. Simply said, the mechanism of laser action in the fundus tissues is to convert light energy into heat, and to perform the primary coagulative damage of the pigment epithelium, choriocapillaris and photoreceptors’ outer layers. In long-term prospective, these necrotic masses are replaced by the reparative tissue rich in pigment cells, and the chorioretinal scar is formed [37]. Furthermore, retina should be fully attached in the LPC area, which is an obligatory condition for a strong chorioretinal adhesion. The direct clinical effect is produced if the desired intensity of the retinal burns is achieved [38].

Optical coherence tomography in vivo reveals the destructive changes in the pigment epithelium during preventive retinopexy and the redistribution of pigment epithelium at the burn’s borders. Cells are destructed and deformed during LPC, as a result, pigment epithelium is proliferated and chorioretinal adhesions are formed in 1 or 2 weeks after the operation (see Figs. 7.4 and 7.5).

Lasers with the wavelength of visible (yellow, green, red, etc.) or near-infrared range (approximately to 1 μm) may be used for retinopexy. Exposure varies from tenths of seconds to seconds. Selection of power begins with the minimum value [11, 15, 39] which then is gradually increased until the 1 degree burn is achieved. For more severe burns one should continue to increase the output power to meet the coagulation step. Burns of greater intensity may also be obtained by increasing the exposure without increasing the power.

When performing retinal LPC with the argon laser (blue-green part of the spectrum: 488–514 nm) or the solid-state YAG laser with doubled frequency (wavelength of the green part of the spectrum: 532 nm), it is necessary to achieve 2–3 degree burns, and 1–2 degree burns when using the diode (infrared: 810 nm) laser.

Burn degree is more homogeneous when using lasers with a wavelength of the visible spectrum, and may differ slightly between burns when using infrared lasers, which is determined, as a rule, by the inhomogeneity of the fundus pigmentation. Burn’s degree and size are influenced by optical media opacities, and the denser is optical haze, the larger may be the laser spot diameter on the fundus and the lower burn’s degree. In the presence of optical media opacities, infrared lasers provide obvious advantage for fundus coagulation, but infrared laser retinopexy weaknesses include the lack of visual control of the tissue response to laser irradiation.

Depending on the extent of degenerative process, its localization and the “malignancy” of its course, that may lead to retinal tear and detachment, there are different methods of LPC: barrier, delimiting, and circular. Several different types of the preventive laser retinopexy have been proposed in the literature: two rows of confluent laser burns [8]; two to three rows of staggered burns with the distance of ≤1 burn diameter between them [11, 39]; three to four rows of adjoined burns along the lesion edge [14].

The most possible attenuated coagulation modes should be used for preventive LPC of peripheral tears and rhegmatogenous retinal degenerations. When performing retinal LPC with an argon laser or a solid-state YAG laser with doubled frequency the continuous mode is used with spot diameter of 300–500 μm and exposure of 0.2 s, the power is adjusted individually depending on the fundus pigmentation and optical media transparency (2–3 degree burn is considered the best). In cases when a diode laser (infrared: 810 nm) is used, burn diameter is 200–300 μm, exposure is 0.1–0.2 s, and the power that is required to achieve 1–2 degree laser burns. The results of treatment are evaluated after 2 weeks after retinal LPC.

A constant follow-up is recommended after retinal LPC: first in 1–2 weeks, then after 3–6 months, and then annually [22]. Additional retinal LPC should be performed in cases of new degenerative foci or progressive and complicated course of retinal lesion [11].

Many authors have warned about the possible complications after retinal LPC, including maculopathy, macular epiretinal membranes, new tears, RRD, exudative retinal detachment, and intraretinal and preretinal haemorrhages [8, 22, 23, 40]. According to several authors, some changes in macular area were observed in 1.7 % of cases after prophylactic laser treatment, vitreous haemorrhage – in 3.7 % of cases, new retinal tears in the early postoperative period – in 5.5 % of cases, and in the late postoperative period – in 8.3 % of cases [41]. Generally, serious adverse events after peripheral LPC are uncommon and usually are associated with different violations of the LPC basic principles: excess of radiation power [40, 42], inadequate or incomplete treatment due to lack of retinopexy along the tear’s anterior margin [41] or obviously excessive overtreatment of large retinal areas [8].

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Jun 27, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Retinal Laser Photocoagulation in Peripheral Retinal Degenerations
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