chemical warfare agents ( cwa ) such as sulfur mustard ( sm ) , a vesicant agent , were extensively used against the iranian troops and civilians during 1983 - 1988 . other proliferating stem cells may also involve and induce long - term impairments , including respiratory and ocular complications . central retinal vein occlusion ( crvo ) is a relatively common retinal vascular disorder and a frequent cause of visual morbidity in patients older than 50 years and can be associated with systemic vascular disease and coagulopathy . although most patients with crvo are over 65 years , it can occur in younger patients commonly termed papillophlebitis . younger patients frequently have an associated inflammatory cause or coagulopathy , which deserve particular attention . up to now , as far as we are aware , no early or late retinal complication of sm exposure has been reported . here , we report a fairly young man presented with non - ischemic crvo without any systemic known predisposing factor except for a history of sm exposure . a 41-year - old man was referred to our eye hospital with a complaint of sudden visual loss in his left eye . an eye examination showed that his best corrected visual acuity ( bcva ) in the right eye ( re ) was 20/20 and in the left eye ( le ) was 20/80 . relative afferent pupillary defect ( rapd ) was slightly positive in the left eye as sluggish movement of the iris . intraocular pressure ( iop ) was 13 and 15 mmhg in re and le , respectively . tear break - up time was less than five seconds , which indicated an abnormal tear film . funduscopic examination of his right eye showed no specific abnormality . in the left eye , retinal hemorrhage in all quadrants of the retina , retinal edema , venous tortuosity , and macular edema were present ( figure 1 ) . in fluorescein angiography delayed circulation , hyperfluorescence due to the breakdown of the blood - retinal barrier , venous tortuosity , and blockage due to retinal hemorrhages were obvious ( figure 2 ) . in ocular optical coherence tomography ( oct ) , macular edema was obvious and central macular thickness was increased to 357 microns ( figure 3 ) . . shows fundus photo of the patient who was exposed to sulfur mustard showing vascular tortuosity , hemorrhages , and macular edema . fluorescein angiography showing vascular tortuosity , macular edema , hemorrhages , multiple hypo and hyperfluorescence of the fundus in a 41-year - old male patient who was exposed to sulfur mustard . optical coherent tomography ( oct ) of the macula showing macular edema in a 41-year - old male patient who was exposed to sulfur mustard . hiv ( eliza ) , antinuclear antibody ( ana ) , and rheumatoid factor ( rf ) tests were also negative . all biochemical , immunological and hematologic investigations revealed no abnormalities and the results are summarized in tables 1 and 2 . results of the biochemical and immunological investigations results of the hematologic investigations the patient had no history of systemic arterial hypertension , no obvious cardiac disease , and no connective tissue diseases . however , cardiology and rheumatology consultations were requested . echocardiographies , both trans - thoracic and trans - esophageal , were negative for structural cardiac abnormalities . although all routine coagulation laboratory tests were within normal limits , we also requested hematologic consultation to rule out any coagulopathies . after 15 months , the consultations were repeated and again all were reported as normal . again , we reviewed his possible use of any drug , medication ( either chemical or herbal ) trauma , smoking , and familial history of such diseases . however , the patient had three times exposure to sm during 1987 - 1988 iran - iraq war . he had ambulatory admission and treatment in a field hospital after the last sm exposure in 1988 and recovered within two days . following written informed consent , he received four serial intravitreal injections of an anti - vascular endothelial growth factor , bevacizumab ( 1.25 mg/0.05 milliliter ) , as an off - label treatment modality . after one year , the central macular thickness decreased to 334 microns and vision improved to 20/25 . the patient was followed up for more than 24 months during which he had stable retina and vision . the patient was informed about the publication of this case report and an oral consent was obtained . sm and similar bifunctional agents have been produced as chemical weapons since the 19 century . high dose exposure to sm may result in death within hours or weeks . however , low - dose exposure may cause injury to the eyes , skin , and respiratory tract without any mortality . very low dose of sm exposure may not induce any symptom or sign and thus it is called subclinical exposure . it seems that our patient had two subclinical exposures in 1987 and one mild symptomatic sm exposure in 1988 , after which he recovered within a couple of days . however , long term effects and delayed complications of sm poisoning are well known and several reports are available , particularly on the respiratory tract , skin and the eyes . . it could be due to ocular characteristics such as high turnover rate , intense metabolic activity of corneal epithelial cells , and the aqueous - mucous surface of the cornea and conjunctiva . as it is absorbed by the lungs and skin , it may disseminate in the body and act as a toxic agent involving the internal organs as well . to our knowledge , no retinal abnormal finding ensuing sm exposure has been reported yet . endothelial cells are proposed to be injured in the sm toxicities and may induce apoptosis and necrosis in endothelial cells all over the body . this may explain the vascular permeability in acute phase after exposure , which can result in bronchial edema . long term effect of sm on vessels may predispose them to occlusion , particularly in microvasculature system such as the retina . crvo is usually associated with systemic cardiovascular diseases and coagulopathies ; and is mostly observed in elderlies . crvo in young adults is probably a general ( nonspecific ) change that results from a number of individual causes or a combination of causes . in unusual cases , the cause is known but in the vast majority of the patients , the specific cause or even the contributing factors are unknown . this is mainly due to limited literature and the paucity of histopathologic material from patients with such condition . in our case , we performed a wide array of laboratory tests , systemic work up , and consultations according to the current findings and algorithms . as all our tests and consultations were normal , we re - evaluated the patient and found a history of exposure to sm , a highly toxic chemical warfare agent that may have caused or played a predisposing factor for his non - ischemic crvo . we thus propose that sm may cause or act as a predisposing factor for non - ischemic crvo .