this study aims to determine the frequency of opthalmyomyiasis externa and the ocular findings of disease in southern khorasan . all patients referred to the emergency department of valiaser hospital during the year 2011 with external ophthalmomyiasis were enrolled in this study . the diagnosis of external ophthalmomyiasis was made according to clinical findings and the presence of oestrus ovis larvae . there were 18 cases of external ophthalmomyiasis in the emergency department of valiaser hospital in 2011 . most cases had the common signs and symptoms of allergic conjunctivitis , except for three males who were referred with respective complaints of red eye , foreign body sensation , and swelling around the eyelids after contact injury the previous day ; corneal infiltration was present in three cases . the visual acuity among the three cases that had peripheral corneal involvement was 20 / 30 in both eyes . the bulbar conjunctiva showed chemosis in all cases and a ropy pattern discharge that was clinically compatible with external ophthalmomyiasis . however , in one case , microscopic slit lamp examination did not show oestrus ovis larvae . although external ophthalmomyiasis usually manifests as allergic conjunctivitis , coronary - like corneal infiltration may be considered in the differential diagnosis of external ophthalmomyiasis or toxic insult . all patients referring to the emergency department of the main general hospital with red eye during the year 2011 were enrolled in this study . the clinical findings were recorded in a questionnaire sheet that was prepared for this reason . an external ophthalmomyiasis diagnosis was made according to clinical findings ( foreign body sensation , lids edema , conjunctival congestion and watering eye , chimosis , and ruppy pattern discharge ) and the presence of oestrus ovis larvae . topical anesthetic drops were used to remove the larva with a plain fine forceps , and topical steroid and antibiotic drops were prescribed for five days thereafter . the frequency of external ophthalmomyiasis in valiaser hospital 's emergency department during the year 2011 was 18 cases ( table 1 ) . all the cases occurred in males who had jobs as farmers or who lived in a rural area . all cases included a history of traveling to desert places or an environment with sheep six to 24 hours earlier , and all patients reported something striking their eye . most patients had the signs of allergic conjunctivitis shown in table 1 , including conjunctival injection along with foreign body sensation , ropy pattern discharge , chemosis , periorbital lid edema , pseudomembrane and corneal infiltration . there was not a remarkable change in visual acuity during or after removal of the larvae . three cases ( 75- , 59- , and 60-year - old residents ) from rural areas referred to the emergency department at valiaser hospital reported that their foreign body sensation began immediately after exposure , and that tap water irrigation of their eyes did not relieve the discomfort . overnight they experienced lid edema , epiphora , and the sensation that the foreign body was moving around their eye . the visual acuity did not change much , with a clear central cornea without intraocular inflammation . the visual acuity among these three cases with peripheral corneal involvement ranged from 20 / 20 to 20 / 30 in both eyes . after initial treatment , one patient no longer experienced the sensation of a moving foreign body ; however , the other patients ' symptoms and signs were not relived after two days of treatment ( figs . 1 and 2 ) . no larva was found on the external surface of eyeball due to late referral in one case , but the external ophthalmomyiasis was characteristic . 3 and 4 showed the larva in the eye of one patient and corneal involvement in the other two cases . the clinical presentation of external ophthalmomyasis is similar to viral or allergic conjunctivitis , with tearing , itching , hyperemia , and foreign - body sensation . keratouveitis has been reported after conjunctivitis ; however , there are a few cases of corneal involvement consisting of diffuse corneal edema , linear subepithelial corneal opacities and endothelial keratic precipitates . this survey is the first ophthalmomyiasis report in the eastern area of iran that was associated with well - defined signs such as red eye , conjunctival chemosis , and a ropy pattern discharge . circumlimbal coronary - shape corneal infiltration is the specific finding in this report that we were not able to find in previous literature , except for a similar finding on conjunctiva as a gelatinous superior limbal conjunctival elevation with overlying fine white plaques ( tanas dots ) in vernal limbitis . the other finding of our study is the frequency and similarity of unilateral conjunctivitis without intraocular involvement as described by masoodi and hosseini   from the fars province in southern iran . the symptoms began while the affected individual was outdoors during the daytime , after the sense of something striking their eye . none of the patients had a history of allergic reactions . also , the first symptoms of foreign body sensation and itching in the eye appeared abruptly in all cases , unlikely related to other possible insults or causes . however , whether these corneal involvements are a result of direct mechanical insult or a toxic reaction is still uncertain and requires future study . if it has spread to the interior of the eye ( ophthalmomyiasis interna ) , the resulting uveitis and endophthalmitis may require aggressive treatment such as vitrectomy and intra vitreal instillation of antibiotics , especially in cases where the visual prognosis remains poor . this report encourages ophthalmologists to suspect external ophthalmomyiasis in people living outdoors and in rural places . the high frequency of external ophthalmomyiasis without intraocular involvement was another interesting finding of our study . the most probable reason that larvae did not invade the intraocular space in this survey may be related to early access to the medical department for the removal of larva . the other possible hypothesis is that this lack of intraocular involvement could be due to the type of masques or number of larval infestations . a coronary pattern of corneal infiltration is the first report of an additional clinical finding in external ophthalmomyiasis , especially in patients with a history of an object striking the eye and in patients who reside in a rural location . awareness of ophthalmomyiasis amongst ophthalmologists working in rural areas is important for the timely diagnosis and treatment of this infestation . a thorough examination of the eye under magnification and prompt removal of the larvae could obviate the disastrous complications of internal ophthalmomyiasis . limiting the exposure to adult flies and exterminating the flies will play a major role in preventing the disease .