to report photographically the evolution of an astrocytic hamartoma of the left optic nerve head over a 2-year follow - up in a patient with retinitis pigmentosa . a 14-year - old boy was seen in the medical retina clinic with a 3-year history of night blindness . fundus examination revealed bone spicule pigmentary changes at the retinal mid periphery typical of retinitis pigmentosa and superficial globules at the margins of both optic nerve heads . two years later , the ocular examination was unchanged except for the appearance of the optic nerve head lesion in the left eye . there was an increase in the size of the lesion which was diagnosed as an astrocytic hamartoma . astrocytic hamartomas of the optic nerve head and optic nerve head drusen have both been described in patients with retinitis pigmentosa . they can be a diagnostic dilemma although drusen are more common ( 10% ) . to differentiate these two entities it is very important to document any growth during the follow - up period which is suggestive of astrocytic hamartoma rather than optic disc drusen . retinal astrocytic hamartomas are rare benign tumours which can arise from any location in the retina , from the optic nerve head and macula to the far periphery . multifocal and bilateral lesions are likely to be associated with tuberous sclerosis and neurofibromatosis [ 1 , 2 ] . we report the evolution of an astrocytic hamartoma of the left optic nerve head over a 2-year follow - up in a patient with retinitis pigmentosa . a 14-year - old boy was referred to the medical retina specialists with a history of night blindness over the last 3 years . colour vision tested with ishihara plates was normal in both eyes and confrontation fields showed mid peripheral constriction . the retinal vessels were not significantly attenuated and the optic nerve heads were not pale . superficial globules at the margins of both optic discs were observed and regarded as optic nerve head drusen ( fig . two years later , the fundus examination revealed evolution of the left optic nerve head lesion with a nodular appearance overlying the optic nerve head vessels ( fig . autofluoresence imaging of the left optic nerve head showed increased autofluorescence of the nodular mass ( fig . astrocytic hamartomas of the optic nerve head are associated with certain types of phakomatoses such as neurofibromatosis and tuberous sclerosis but are also often seen in eyes with retinitis pigmentosa [ 4 , 5 ] . although optic nerve head drusen are more common in patients with retinitis pigmentosa [ 6 , 7 ] , they can be difficult to distinguish from an astrocytic hamartoma as illustrated in this case . histopathologically , the drusen contain multiple deposits of calcium crystals that vary in size ( 51,000 m ) . these crystals are located in the pre - laminar region of the optic nerve head and are believed to arise from the debris due to long - standing axonal stasis in the nerve fibre layer . they are within the substance of the nerve , whereas disc hamartomas consist of astrocytic cell proliferations in addition to calcifications which overlie the disc and then involve the peripapillary area . in the past , when the distinction between astrocytic hamartoma and optic nerve head drusen was not clear , many patients with retinitis pigmentosa were presumed to have optic disc drusen . differential diagnoses should also include papilloedema , optic disc hemangiomas , retinoblastomas , meningiomas , metastatic tumours , combined hamartomas of the retina and retinal pigment epithelium and granulomas of different aetiologies . b - scan , autofluorescence , fluorescein angiography , optical coherence tomography and computed tomography of the brain could be very helpful in differentiating the optic nerve head lesions . in our case , the lesion in the left optic nerve head was presumed to be a drusen on clinical examination in the first instance , but the examination 2 years later showed a change in the size and the appearance with characteristics suggestive of optic nerve head astrocytic hamartoma . this is the first time in our knowledge that such an evolution is documented photographically in a patient with retinitis pigmentosa .
aimto report photographically the evolution of an astrocytic hamartoma of the left optic nerve head over a 2-year follow - up in a patient with retinitis pigmentosa.methodsa 14-year - old boy was seen in the medical retina clinic with a 3-year history of night blindness . 
 best corrected visual acuity was 6/18 in both eyes . 
 colour vision was normal in both eyes and confrontation fields showed peripheral constriction . 
 fundus examination revealed bone spicule pigmentary changes at the retinal mid periphery typical of retinitis pigmentosa and superficial globules at the margins of both optic nerve heads . 
 electrodiagnostic tests confirmed moderately severe rod cone dystrophy with macular involvement bilaterally.resultstwo years later , the ocular examination was unchanged except for the appearance of the optic nerve head lesion in the left eye . 
 there was an increase in the size of the lesion which was diagnosed as an astrocytic hamartoma . 
 further investigations were recommended to exclude neurofibromatosis and tuberous sclerosis.conclusionastrocytic hamartomas of the optic nerve head and optic nerve head drusen have both been described in patients with retinitis pigmentosa . they can be a diagnostic dilemma although drusen are more common ( 10% ) . to differentiate these two entities 
 it is very important to document any growth during the follow - up period which is suggestive of astrocytic hamartoma rather than optic disc drusen .