central retinal vein occlusion ( crvo ) is the second most common retinal vasculopathy and predominantly occurs in patients over 60 years of age with associated risk factors , such as vascular disease , hypertension and glaucoma .
a minority of patients with crvo are young adults , under 40 years of age . in most of these cases
, crvo occurs without the presence of the typical risk factors , and a comprehensive workup is warranted .
unusual causes for crvo in young patients include hypercoagulability states , collagen vascular diseases , lymphoproliferative disorders , malignant hypertension , medications ( most notably oral contraceptives and isotretinoin ) , and trauma [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] .
a recent study has demonstrated that hyperlipidemia and hyperhomocysteinemia were the most significant risk factors for crvo in patients under 40 .
intense exercise and associated dehydration have rarely been reported to cause crvo in young patients [ 15 , 16 , 17 ] .
we report a patient who suffered crvo following intense exercise and was treated with intravitreal bevacizumab injections with complete resolution .
a 19-year - old man was referred to our clinic due to decreased visual acuity ( va ) in his left eye .
the patient had no previous systemic or ocular medical history and did not use any medication .
his complaint of decreased va acutely started 1 week prior to his presentation , after several days of intense physical activity ( long distance running and weight lifting performed outdoors during the summer ) .
he remained stable during the time of exercise . on initial examination , his best corrected va was 20/20 in the right eye and 20/150 in the left eye .
his intraocular pressure was 12 mm hg in both eyes , the range of ocular movements was fully bilateral , and there was no relative afferent pupillary defect .
fundus examination of the left eye was significant for a swollen disc , numerous retinal hemorrhages , macular edema ( me ) and tortuous dilated retinal vasculature ( fig .
fluorescein angiography demonstrated hyperfluorescence compatible with disc hyperemia , me , and areas of blocked fluorescense compatible with the retinal hemorrhages .
our workup included a normal complete blood count , blood chemistry , lipid profile and coagulation tests ( pt and ptt ) .
the erythrocyte sedimentation rate was normal ( 5 mm / h ) , and a complete collagenogram , including the rheumatic factor , antinuclear antibodies and antineutrophil cytoplasmic antibodies , was also normal .
hemoglobin electrophoresis , the complete neurological examination and the head ct were also normal , as was the further workup for an increased coagulability ( including tests for hyperhomocysteinemia , antiphospholipid antibodies , factor v leiden mutation and 2-glycoprotein ) . the patient was treated with 3 monthly intravitreal injections of bevacizumab ( 1.25 mg/0.05 ml ) . following these 3 injections , va in the left eye
had improved to 20/20 , the hemorrhages had resorbed , and the fundus examination returned to normal ( fig .
the me had also been completely resorbed with the restoration of a normal macular architecture ( fig .
the natural history of eyes with crvo is associated with a poor visual prognosis , especially in cases with nonperfused crvo [ 19 , 20 ] . until recently ,
treatment of me in patients with crvo had been guided by the historic central vein occlusion study that recommended mere observation in these cases .
however , significant advances had been made in recent years , and there are now several effective treatment options for the affected eyes .
these include intravitreal injections of steroidal agents , such as triamcinolone acetate   and the ozurdex slow - release dexamethasone implant , and anti - vascular endothelial growth factor agents such as ranibizumab , bevacizumab [ 25 , 26 ] and aflibercept .
in contrast to older patients , crvo in young adults has a much more favorable natural history . at presentation , va is typically not reduced and a spontaneous resolution over several months is possible .
however , it should be noted that some of these eyes suffer a significant and permanent visual impairment and may develop complications such as chronic me , retinal neovascularization and vitreal hemorrhage . due to the rarity of crvo in young patients , randomized controlled trials of the various treatment options for these patients has not yet been performed , and there are currently no established guidelines for the treatment of these patients .
dehydration due to either fasting or intense exercise has been infrequently reported as a cause of crvo in young patients [ 15 , 16 , 17 , 18 ] .
out of the 11 patients reported in these works , only 1 had been treated with bevacizumab .
this was a 40-year - old male athlete with crvo that occurred following intense exercise and secondary dehydration .
the patient we described had no previous medical or ocular history and underwent a comprehensive investigation that revealed no causative factor for crvo .
since the symptoms started after a period of intense exercise , it is likely that the patient had been dehydrated and that was the cause for the occurrence of crvo . during dehydration , the blood hematocrit increases , which results in a temporary hyperviscosity state .
the central retinal vein is susceptible for thrombosis in the presence of hyperviscosity , which reduces the blood flow , especially at the point it goes through the lamina cribrosa .
we describe a second case of a young patient with crvo , caused by intense exercise , that was treated with bevacizumab .
after 3 monthly injections , a complete resolution with a restoration of 20/20 vision was achieved , and no recurrence occurred following cessation of treatment .
although it is possible that a spontaneous resolution would have occurred even without treatment in this patient , it should be noted that me was significant and his va was reduced in an otherwise healthy and young patient .
repeated intravitreal injections of anti - vascular endothelial growth factor agents have been established as a safe and effective treatment method for me in crvo [ 24 , 25 , 26 ] and may very well be beneficial in young patients with crvo .
this case report should raise awareness to the possibility of intense exercise as a possible cause for crvo in young patients . in the absence of an established treatment regimen for these cases , we suggest that treatment can be initiated despite the possibility of a spontaneous resolution .
intravitreal bevacizumab injections seem to be a safe and effective treatment option for such cases .
the authors declare that there are no conflicts of interest regarding the publication of this article .
 we report a 19-year - old patient who developed a central retinal vein occlusion ( crvo ) with significant macular edema and visual impairment following intense exercise and dehydration . 
 the patient was treated with 3 intravitreal bevacizumab injections with complete resolution . 
 a review of the literature on the cause and treatment for crvo in young patients was performed , focusing on the role of intense exercise and dehydration as a rare pathogenesis mechanism of crvo . 
Introduction
Case Report
Discussion
Disclosure Statement