treatment duration lasts for months , and is often fraught with potentially dangerous side effects . some of these side effects , such as influenza - like illness , myalgias , depression , and cytopenias can be intolerable resulting in premature treatment cessation , but have no lasting effects . ocular complications are among the complications of interferon therapy and include retinal hemorrhages , cotton wool spots , loss of color vision , cataracts , glaucoma , and occasionally retinal artery or vein obstruction . although the incidence of ophthalmological disorders while on interferon therapy is low , this can result in loss of vision.411 in this prospective case series study , one hundred patients with chronic hepatitis - c under interferon ( inf ) therapy were consecutively recruited from patients attending the outpatient ophthalmic clinic at the university hospital , faculty of medicine , al - azhar university , assuit . the study protocol was approved by the ethics committee at al - azhar university hospital . written informed consent was obtained from all patients included in the study , and then in addition to the medical and laboratory examination , all patients were subjected to full ophthalmological assessment to evaluate the retinopathy associated interferon therapy . inclusion criteria were : ( 1 ) seropositivity for anti - hcv antibodies determined using elisa ; ( 2 ) first use of interferon therapy . exclusion criteria were : ( 1 ) previous interferon therapy ; ( 2 ) patients with hepatitis b ; ( 3 ) patients with decompensated liver ; ( 4 ) patients with renal failure ; ( 5 ) patients with cardiovascular disorders such as coronary insufficiency , congestive heart failure , and ischemic stroke ; ( 6 ) patients with a dense cataract , visual field abnormality , glaucoma , or any other ocular abnormalities . evaluation before treatment : history of visual loss , hazy vision , and ocular disease or ocular surgeries ophthalmological examination : ( 1 ) best corrected visual acuity ( bcva ) measured using landolt s broken rings ; ( 2 ) pupillary reaction ( direct and consensual ) and if there is afferent pupillary defect ; ( 3 ) full slit - lamp examination ; ( 4 ) intraocular pressure ( iop ) measured by goldmann s applanation tonometer ; ( 5 ) fundus biomicroscopy ( carried out after maximum pupillary dilation by a combination of tropicamide 1% eye drops and phenylephrine 2.5% eye drops using both slit - lamp biomicroscopy with noncontact + 90 d volk lens and/or goldmann contact lens ) ; ( 6 ) examination of the retinal periphery using an indirect ophthalmoscope . medical examinations and abdominal ultrasonography investigations : ( 1 ) ocular , both colored fundus photography and fundus fluorescein angiography ( ffa ) ; ( 2 ) laboratory ( including enzyme - linked immunosorbent assay ( ellsa ) test for hepatitis surface ag and ab ; polymerase chain reaction ( pcr ) for hepatitis c virus rna ; full blood count ; prothrombin time ; direct and indirect bilirubin ; fasting blood sugar ; serum creatinine ; liver enzymes ( serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase ) ; alanine aminotransferase . patients were treated with pegylated interferon -2a at a dose of 180 mcg injected subcutaneously once weekly for 48 weeks . all patients underwent clinical and laboratory assessments , ophthalmic examination , at 15 days , 1 month , 2 months , 3 months , 6 months , 8 months , and 9 months after the start of ifn treatment . patients were treated with pegylated interferon -2a at a dose of 180 mcg injected subcutaneously once weekly for 48 weeks . all patients underwent clinical and laboratory assessments , ophthalmic examination , at 15 days , 1 month , 2 months , 3 months , 6 months , 8 months , and 9 months after the start of ifn treatment . initially , 120 patients fulfilled the criteria for ifn therapy , but 20 of them were excluded due to non - compliance with the follow - up visits and due to the presence of diabetic or hypertensive retinopathy . also , two patients died during the study time , due to a disease not related to hepatitis , so these patients are not included . therefore , a total of 100 patients ( 68 male and 32 female ) , with chronic hcv were selected . after the start of interferon therapy , 16 out of 100 patients ( 16% ) developed retinopathy which was bilateral in 12 ( 75% ) patients and unilateral in 4 ( 25% ) patients . retinopathy was initially diagnosed by the appearance of a cotton wool spot in 14 patients . in four of the 14 patients , retinal hemorrhage two of the 16 patients who developed retinopathy were diagnosed by retinal hemorrhage without cotton wool spots . one patient ( not diabetic or hypertensive ) had cystoid macular edema , this was the only patient who complained of the visual disturbance due to interferon . all patients had bcva of ( 6/6 ) during ifn treatment except for three patients : the one who had cystoid macular edema ( bcva was 6/12 and returned to 6/6 after cessation of treatment ) and two patients with ametropic amblyopia . in addition , we confirmed that all patients with hypertension had no retinopathy using the standard classification . to exclude the possibility of the development of diabetic or hypertension retinopathy after ifn treatment , we deleted the data obtained from patients who had diabetes or hypertension and any retinopathy 2 months after the cessation of ifn treatment . retinopathy was first diagnosed 214 weeks after the start of treatment and disappeared in 11 of the 16 patients despite the continuation of therapy . a few cotton wool spots , retinal hemorrhages , or both were observed in the remaining five patients at the end of treatment but resolved within 1 month after treatment was stopped . no other ocular complications ( ie , cataracts , glaucoma , retinal artery , or vein obstruction ) were observed . the mean hemoglobin values , white blood cell , red blood cell , and platelet counts decreased significantly ( p < 0.0001 ) during ifn treatment . the clinical profiles and laboratory data of the patients are shown in tables 1 and 2 , respectively . interferon - associated retinopathy was first recognized in 1990 when ikebe and associates reported a 39-year - old patient who developed retinal hemorrhages and cotton wool spots following intravenous administration of interferon.12 the underlying mechanisms of interferon - induced retinopathy are not completely understood . guyer et al13 had proposed an immune complex deposition causing occlusion of retinal capillaries leading to cotton wool spot formation . on the other hand , an ischemic insult , similar to that seen in hypertensive and diabetic patients could be another potential mechanism by which these changes develop.14 some studies15,16 have shown a relatively higher incidence of retinopathy ( symptomatic or asymptomatic ) ranging from 19% to 64% during treatment with interferon . panetta and gilani17 and cuthbertson et al14 show relatively lower incidences of retinopathy ( 3.8% and 6.25% , respectively ) . similar to other studies,4,5,9 our study also shows that retinal changes usually develop within the first 3 months of interferon treatment , a fact that may favor an immune etiology rather than a cumulative effect of interferon leading to the development of retinopathy . retinopathy developed by week 14 in most of the patients ( 13/16 , 81.25% ) after the start of therapy and disappeared in the majority of the patients ( 11/16 , 68.75% ) during the 48 week period in which the patients were receiving the treatment . this suggests that treatment can be continued despite the development of retinopathy in many patients . however , two patients who developed cotton wool spots early in the therapy ( 2 weeks ) thereafter suffered from retinal hemorrhage in a prolonged manner . therefore , patients who develop cotton wool spots early on during therapy should be carefully monitored . however , as reported in previous studies,4,13,14 most of the patients with retinopathy in this study were asymptomatic . this study confirms previous reports that retinopathy is a temporary and asymptomatic complication of interferon therapy . therefore there is no rule for suspending the use of interferon in patients who develop retinopathy or any other ocular side effects . it s commonly agreed among authors that careful monitoring should be performed in the presence of any ocular sign , even without symptoms.18