Retinal Photocoagulation
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Photocoagulation uses light to create a thermal burn in retinal tissue. When energy from a strong light source is absorbed by the retinal pigment epithelium (RPE) and is converted into thermal energy, coagulation necrosis occurs with denaturation of cellular proteins as temperature rises above 65°C. [1]
Since the Diabetic Retinopathy Study (DRS), the source of light for photocoagulation has evolved from using a diffuse Xenon arc to using well-focused laser in the treatment of proliferative diabetic retinopathy. Presently, laser retinal photocoagulation is a therapeutic option in many retinal and eye conditions. [2, 3, 4]
Effective retinal photocoagulation requires an unobscured view of the retinal tissue for light to be absorbed by pigment in the target tissue. In retinal tissue, light is absorbed by melanin, xanthophyll or hemoglobin. Melanin absorbs green, yellow, red and infrared wavelengths; xanthophyll (in the macula) absorbs blue but minimally absorbs yellow or red wavelengths; hemoglobin absorbs blue, green and yellow with minimal red wavelength absorption. [5]
Indications for retinal photocoagulation include the following: [6, 7, 8, 9, 10]
Panretinal photocoagulation (PRP) for neovascular proliferative diseases such as proliferative diabetic retinopathy, sickle cell retinopathy, and venous occlusive diseases (see image below)
Focal or grid photocoagulation for macular edema from diabetes or branch vein occlusion (see image below)
Treatment of threshold and high-risk prethreshold retinopathy of prematurity
Closure of retinal microvascular abnormalities such as microaneurysms, telangiectasia and perivascular leakage
Focal ablation of extrafoveal choroidal neovascular membrane
Creation of chorioretinal adhesions surrounding retinal breaks and detached areas [11]
Focal treatment of pigment abnormalities such as leakage from central serous chorioretinopathy [12]
Treatment of ocular tumors
Treatment of the ciliary body to decrease aqueous production for glaucoma
Patients require anesthesia for the procedure. Most patients undergo retinal laser procedures under topical anesthesia such as proparacaine eye drops. Other patients will require subconjunctival, peribulbar, or retrobulbar injections of lidocaine.
Monitored anesthesia care or general anesthesia is usually used for premature infants (with retinopathy of prematurity), children, and patients with problems in compliance.
The laser source is connected via a fiberoptic cable to different types of delivery systems. Laser is delivered to the retina externally either through the cornea (transcorneal) or the sclera (transscleral). Transcorneal delivery employs a slit lamp (see first image below) or a Laser Indirect Ophthalmoscope (LIO). With the slit lamp delivery system, the laser is fired onto the retina using a contact lens which is placed on the corneal surface of the patient. Using the LIO delivery system, a noncontact binocular indirect ophthalmoscope condensing lens such as 28 D or 20 D lens (see second image below), is used to focus the laser onto the retina. [13]
Transscleral delivery uses a diode transscleral laser probe applied onto the sclera to treat the retina or ciliary body. [14]
Laser can also be delivered internally (inside the eye), usually during vitrectomy procedures. An endolaser probe is introduced into the vitreous cavity, and laser is fired directly to the retina. The procedure is viewed using vitrectomy lens under an operating microscope.
When using the slit lamp delivery system, the procedure is performed with the patient in a sitting position. With the endolaser and transscleral delivery systems, the patient is supine. With the LIO, the patient may be sitting or supine.
Proper laser protection goggles are required for all staff assisting the procedure. The laser safety filter (specific for each wavelength of laser) on the delivery system should always be activated upon performing the procedure.
The patient should be well positioned and instructed prior to the procedure. Retrobulbar block or general anesthesia may be done for compliance problems.
The procedure should be performed or supervised by an experienced ophthalmologist to avoid technical errors resulting in complications from the procedure.
When using the slit lamp delivery system, a slit lamp contact lens is used to focus a beam of laser light onto the retina. With the indirect ophthalmoscope system, an indirect lens is used to focus the laser light onto the retina. With the endolaser, a laser probe is introduced into the vitreous cavity (usually during vitrectomy surgery) and the laser light is directly applied to the retina.
Conventional laser delivery systems for retinal photocoagulation deliver spots individually on the retina. Newer semiautomatic laser delivery systems like the pattern scanning laser (PASCAL) have been designed to produce multiple spots on the retina in the same amount of time as conventional laser delivery systems. This makes the procedure less tedious and time consuming, allowing for better patient comfort. [15]
New technology has been developed to minimize retinal damage, delivering micropulses of laser (micropulse laser). These micropulses have been shown to cause less retinal injury. [16]
Although proven safe, like any other surgical procedure, retinal photocoagulation may occasionally be associated with complications. Before undergoing retinal photocoagulation, the patient should be fully informed of these, which include the following: [17, 18]
Anterior segment complications such as corneal or lenticular opacification
Transient visual loss
Photocoagulation of the fovea
Macular edema
Hemorrhage
Choroidal Effusion
Color vision alterations
Visual field defects and night vision problems
Hemeralopia
Glickman RD. Phototoxicity to the retina: mechanisms of damage. Int J Toxicol. 2002 Nov-Dec. 21(6):473-90. [Medline].
Photocoagulation treatment of proliferative diabetic retinopathy: the second report of diabetic retinopathy study findings. Ophthalmology. 1978 Jan. 85(1):82-106. [Medline].
Okamoto M, Matsuura T, Ogata N. EFFECTS OF PANRETINAL PHOTOCOAGULATION ON CHOROIDAL THICKNESS AND CHOROIDAL BLOOD FLOW IN PATIENTS WITH SEVERE NONPROLIFERATIVE DIABETIC RETINOPATHY. Retina. 2015 Oct 7. [Medline].
Ogura S, Yasukawa T, Kato A, Kuwayama S, Hamada S, Hirano Y, et al. Indocyanine Green Angiography-Guided Focal Laser Photocoagulation for Diabetic Macular Edema. Ophthalmologica. 2015 Sep 23. [Medline].
Ip M, Puliafito CA. Laser Photocoagulation. Yanoff, Duker JS. Ophthalmology. 3rd. Elsevier Health Sciences; 2008. 522-3.
Parodi MB, Bandello F. Branch retinal vein occlusion: classification and treatment. Ophthalmologica. 2009. 223(5):298-305. [Medline].
Leaver P, Williams C. Argon laser photocoagulation in the treatment of central serous retinopathy. Br J Ophthalmol. 1979 Oct. 63(10):674-7. [Medline]. [Full Text].
Salvin JH, Lehman SS, Jin J, Hendricks DH. Update on retinopathy of prematurity: treatment options and outcomes. Curr Opin Ophthalmol. 2010 Sep. 21(5):329-34. [Medline].
Stoffelns BM, Schoepfer K, Vetter J, Mirshahi A, Elflein H. [Long-Term Follow-Up 10 Years after Transpupillary Thermotherapy (TTT) for Small, Posterior Located Malignant Melanomas of the Choroid.]. Klin Monbl Augenheilkd. 2011 Apr. 228(4):277-283. [Medline].
Becker BC, MacLachlan RA, Lobes LA Jr, Riviere CN. Semiautomated intraocular laser surgery using handheld instruments. Lasers Surg Med. 2010 Mar. 42(3):264-73. [Medline].
Zhou C, Qiu Q. 360° versus localized demarcation laser photocoagulation for macular-sparing retinal detachment in silicone oil-filled eyes with undetected breaks: A retrospective, comparative, interventional study. Lasers Surg Med. 2015 Oct 6. [Medline].
Kretz FT, Beger I, Koch F, Nowomiejska K, Auffarth GU, Koss MJ. Randomized Clinical Trial to Compare Micropulse Photocoagulation Versus Half-dose Verteporfin Photodynamic Therapy in the Treatment of Central Serous Chorioretinopathy. Ophthalmic Surg Lasers Imaging Retina. 2015 Sep 1. 46 (8):837-43. [Medline].
Mizuno K. Binocular indirect argon laser photocoagulator. Br J Ophthalmol. 1981 Jun. 65(6):425-8. [Medline].
Gangwani R, Liu DT, Congdon N, Lam PT, Lee VY, Yuen NS. Effectiveness of diode laser trans-scleral cyclophotocoagulation in patients following silicone oil-induced ocular hypertension in Chinese eyes. Indian J Ophthalmol. 2011 Jan-Feb. 59(1):64-6. [Medline].
Blumenkranz MS, Yellachich D, Andersen DE, et al. Semiautomated patterned scanning laser for retinal photocoagulation. Retina. 2006 Mar. 26(3):370-6. [Medline].
Yu AK, Merrill KD, Truong SN, Forward KM, Morse LS, Telander DG. The comparative histologic effects of subthreshold 532- and 810-nm diode micropulse laser on the retina. Invest Ophthalmol Vis Sci. 2013 Mar 1. 54 (3):2216-24. [Medline].
Fong DS, Girach A, Boney A. Visual side effects of successful scatter laser photocoagulation surgery for proliferative diabetic retinopathy: a literature review. Retina. 2007 Sep. 27(7):816-24. [Medline].
Henricsson M, Heijl A. The effect of panretinal laser photocoagulation on visual acuity, visual fields and on subjective visual impairment in preproliferative and early proliferative diabetic retinopathy. Acta Ophthalmol (Copenh). 1994 Oct. 72(5):570-5. [Medline].
David G Telander, MD, PhD Ophthalmologist, Vitreo-Retinal Diseases and Surgery, Retinal Consultants Medical Group; Volunteer Clinical Faculty, Department of Ophthalmology, University of California, Davis, School of Medicine
David G Telander, MD, PhD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Retina Specialists, Association for Research in Vision and Ophthalmology, Retina Society
Disclosure: Nothing to disclose.
Andrew A Dahl, MD, FACS Assistant Professor of Surgery (Ophthalmology), New York College of Medicine (NYCOM); Director of Residency Ophthalmology Training, The Institute for Family Health and Mid-Hudson Family Practice Residency Program; Staff Ophthalmologist, Telluride Medical Center
Andrew A Dahl, MD, FACS is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, American Intraocular Lens Society, American Medical Association, American Society of Cataract and Refractive Surgery, Contact Lens Association of Ophthalmologists, Medical Society of the State of New York, New York State Ophthalmological Society, Outpatient Ophthalmic Surgery Society
Disclosure: Nothing to disclose.
Edmin Michael G Santos, MD, DPBO Associate Clinical Professor, Department of Ophthalmology and Visual Sciences, University of the Philippines, Philippine General Hospital; Chief of Service, Retina and Vitreous, EYE REPUBLIC Ophthalmology Clinic; Visiting Consultant, International Eye Institute, St Luke’s Medical Center; Staff Physician in Ophthalmology, Asian Hospital and Medical Center
Edmin Michael G Santos, MD, DPBO is a member of the following medical societies: American Academy of Ophthalmology, Philippine Medical Association, Philippine Society of Cataract and Refractive Surgery, Philippine Academy of Ophthalmology
Disclosure: Nothing to disclose.
Retinal Photocoagulation
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