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+ Larger Font / - Smaller Font NTRC Newsletter Volume 1 Issue 2 August 18, 2005 Central Retinal Vein Occlusion By Sunil S Patel, M.D., Ph.D and Tiffany Hardin, COA Central retinal vein occlusion (CRVO) occurs when the retinal venous outflow is partially or completely blocked at or near the lamina cribrosa by a thrombus or central retinal artery compression of the central retinal vein. It results in intraretinal hemorrhages in all four quadrants with or without blurring of optic disk margins and is often accompanied with macular edema. The vision is affected due to macular edema and/or poor perfusion (ischemia) of the retina. A CRVO can be associated with glaucoma, hypertension, diabetes, atheriosclerosis, cardiovascular disease, and hyperviscosity states. A person over age 50 with hypertension, diabetes, glaucoma, or atheriosclerosis who presents with CRVO requires no additional work up. However, a person under the age of 50 or anyone without the above risk factors should have a complete history and physical exam. A complete history should include tobacco use, blood pressure, hydration, birth control pill use, and hyperviscosity states (DVT etc). Lab work up should include ANA, RF, CBC, lipid panel, fasting blood glucose, ESR, CRP, PT/PTT, lupus anticoagulant, anticardiolipin antibodies, anti-thrombin III, protein C, protein S, alpha-2 globulin.(1) Once the etiology is determined, additional work up may be necessary for management. This includes photos and fluorescein angiogram to determine the perfusion status (i.e., ischemic vs nonischemic). An optical coherence topography (OCT) will be needed as well to examine for macular edema. There are two types of CRVO's: Nonischemic - normal or near normal capillary perfusion or Ischemic - at least 10 disk areas of capillary nonperfusion. Approximately 75% of CRVO are nonischemic, however up to 34% of nonischemic will progress to ischemic variety. About 60% of ischemic CRVO will develop iris neovascularization and approximately 33% will progress to neovascular glaucoma. Neovascular glaucoma has a very poor visual prognosis, since most will have vision of 20/400 or worse and some will progress to no light perception (NLP). It is very important that high risk eyes be carefully followed every month for the first six months to avoid neovascular glaucoma.(2,3) CRVO Study The CRVO Study was established to determine the risk factors associated with poor visual outcome, and management of ischemic CRVO and macular edema associated with CRVO. The results showed that the main variable in the final visual acuity was the initial visual acuity. The important factors in differentiating ischemic from nonischemic CRVO were the presence of afferent papillary defect, 10 or more disk areas of capillary nonperfusion, visual acuity of 20/200 or worse, and/or extensive intraretinal hemorrhages in 2-4 quadrants.(3) The CRVO study demonstrated that although grid photocoagulation had improvement of macular edema, no improvement in visual acuity was seen. Therefore, grid laser is not recommended for macular edema from CRVO.(4) The CRVO study also showed that panretinal photocoagulation (PRP) was effective in prevention and management of rubeosis isidis prior to development of neovascular glaucoma. However, the CRVO study recommended that PRP should be performed only once rubeosis iridis becomes evident.(5) It should be mentioned that none of the treatments in the CRVO study had any beneficial effect or improvement in the visual outcome. Patients should be followed monthly for the first 6 months because of the high risk of developing rubeosis iridis and neovascular glaucoma. Management For CRVO Laser Laser for CRVO is effective in only management of rubeosis iridis. It has no other role in the management of macular edema induced by CRVO. Intravitreal Triamcinolone Intravitreal triamcinolone has been shown to be very effective in the management of macular edema from CRVO. The vision improved with intravitreal triamcinolone from 20/200 to 20/60 (Figure 1). However, the edema often recurs after triamcinolone dissipates over 3-6 months. There are also complications such as endophthalmitis, IOP elevations and cataract formation. The Standard Care vs Corticosteroid for Retinal Vein Occlusion (SCORE) study currently underway should determine the efficacy of triamcinolone in the management of macular edema.(6)
Pars Plana Vitrectomy (PPV) Pars plana vitrectomy has been effective in the management of edema from CRVO. The PPV is effective in improving oxygenation to the ischemic retina and relieving any macular traction by removing the posterior hyaloid and inner limiting membrane. We have had visual improvement with PPV and membrane peeling in some patients who have not responded well to triamcinolone.(7) Radial Optic Neurotomy (RON) RON is a procedure that was developed by Opremcak.(7) The procedure involves making a radial incision on the optic nerve head to relieve the obstruction and decompress the nerve. As can be seen by decompressing the nerve head by a radial slit (Figure 2) incision, the obstruction of the central retinal vein is partially or completely relieved. We have performed 12 RON's on patients with vision 20/200 or worse. Four of 12 patients have had significant improvement (>3 lines) and the remaining eight had stabilization of visual acuity. It should be noted that none of the patients developed neovascular glaucoma or had worsening of the visual acuity. The patient in Figure 3 did improve with radial optic neurotomy from 20/200 to 20/40.
Other Treatments There is no role for laser induced chorioretinal anastomosis in the management of CRVO because of lack of efficacy and high rate of complications. Another procedure involves the canalization of the central retinal vein with a catheter and infusing the thrombolytic agents (tPA). This has been shown to have some efficacy, but requires extensive technological equipment and training. It is unclear if this procedure is better than radial optic neurotomy. Summary of Management Scheme for CRVO Figure 4 summarizes a basic management scheme for a CRVO. It is very important to differentiate between ischemic from non-ischemic CRVO. A careful follow up is recommended to examine for neovascularization of the iris. As newer therapeutic modalities became available, vision not only be stabilized, but improved. (1) Elman MJ. Systemic associations of retinal vein occlusions. Int Ophthalmol Clin 1991;31:15-22. (2) Hayreh SS. Classification of central retinal vein occlusion. Ophthalmology 1999; 110:123-188. (3) Central Vein Occlusion Study Group. Baseline and early natural history report: The Central Vein Occlusion Study. Arch Opththalmol 1993; 111:1087-1095. (4) Central Vein Occlusion Study Group. Evaluation of grid pattern photocoagulation for macular edema in central vein occlusions: the Central Vein Occlusion Group M report. Ophthalmology 1995; 102:1425-1433. (5) Central Vein Occlusion Study Group. A randomized clinical trail of early panretinal photocoaguation for ischemic central vein occlusion: the Central Vein Occlusion Study Group. Ophthalmology 1995; 102: 1434-1444. (6) William TH, O'Donnell A. Intravitreal triamcinolone acetonide for cystiod macular edema in nonischemic central retinal vein occlusion. American Journal of Ophthalmology May 2005; 139(5), 860-6. (7) Opremcak EM, Bruce RA, Lomea MD, Ridenour CD, Letson AD, Rehmar AJ. Radial optic neurotomy for central retinal vein occlusions. Retina 2001; 21(5):408-15. North Texas Retina Consultants Sunil S. Patel, M.D., Ph.D. S. Young Lee, M.D. 925 Santa Fe, Suite 105 Weatherford, Texas 76086 888-594-0914 817-594-0914 info@northtexasretina.com |
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