to report the case of failed surgical excision of optic nerve drusen ( ond ) . a 53-year - old woman presented with bilateral ond leading to progressive field defects and le light perception and re 20/25 vision . a vitrectomy was performed on the legally - blind left eye to test the resectability of ond . the removal of superficial ond failed because the singular - appearing superficial ond presented as one large mass with multiple excrescences on its surface . ond can not always be removed surgically , due to their variable consistency and hardness . optic nerve drusen ( ond ) are acellular , calcific deposits occurring in 3.4 to 24  of the population . changes in axoplasmatic transport and the axonal degeneration of optic nerve fibres are suspected of being involved in ond formation [ 2 , 3 ] . most patients are subjectively asymptomatic , but visual acuity , preceded by severe visual field defects , is severely impaired in a small number of patients . in contrast , and to demonstrate the heterogenicity of cases , we present a patient whose surgical excision of ond failed . a 53-year - old woman presented with progressive visual field defects in the right eye , and long - standing visual loss in the left eye . initial examination revealed best - corrected visual acuity of 20/25 re , light perception le , a severely constricted visual field in the re < 10 and an unremarkable slit - lamp examination ou . dilated ophthalmoscopic examination revealed bilateral superficial ond , which appeared as multilobular , yellowish - white , sharp - edged nodules and anomalous arterial and venous branchings , increased tortuosity , and cilioretinal arteries ( fig .  1 ) . 1fundus photography of right eye ( a ) , with progressive field defects and left eye ( b ) , functionally blind , showing multiple superficial ond covering the entire disc and abnormal branching of retinal vessels fundus photography of right eye ( a ) , with progressive field defects and left eye ( b ) , functionally blind , showing multiple superficial ond covering the entire disc and abnormal branching of retinal vessels to test the resectability of ond and to gain experience , we decided to perform a vitrectomy with surgical excision on the blind left eye before considering surgical manipulations on the right eye with the risk of losing the remaining small central visual field , leading to complete blindness . after informing the patient about the procedure s experimental character and obtaining informed consent , we conducted a standard three - port pars plana vitrectomy . we then performed a small retinotomy at the nasal edge of the optic nerve . despite numerous efforts using different vitreoretinal surgical instruments such as blades , forceps and fine scissors , removal of the superficial ond failed . during surgery , we became aware that the small , multiple , and singular - appearing superficial onds presented as the multilobulated surface of one calcified crust covering the complete optic nerve head , with central retinal vessels passing through ( fig . it was impossible to split the extremely hard crust into small pieces and to remove considerable parts of it . moreover , radial neurotomy as described in the literature was impossible due to the hardness of the ond material . 2intra - operative image of left eye showing ineffective manipulations at the nasal edge of the optic nerve intra - operative image of left eye showing ineffective manipulations at the nasal edge of the optic nerve axonal degeneration , ischaemia within the optic nerve head , and ond pressing down on prelaminar nerve fibres have been proposed as pathogenetic mechanisms in ond disease [ 1 , 3 ] . a recent publication reported on a good functional outcome after vitrectomy and radial optic neurotomy ( ron ) for ond , suggesting that ron leads to mechanical decompression with subsequent optic nerve fibre recovery , and that the excision of prelaminar deposits is an effective strategy in ond disease . however , our case shows that surgical removal or decompression is not possible in all cases ; our patient was considerably older than theirs . a histological study in 1981 demonstrated that the number and size of superficial and buried ond vary greatly . furthermore , their size and density increase with age , due to continuous calcium apposition . rather than revealing multiple small deposits , our patient s ond formed a single , large solitary mass with central retinal arteries and veins passing through it . our observation concurs with a report by kapur et al . , who reported on the incomplete surgical excision and bisection of ond in a 59-year - old patient in contrast to their experience , in our patient the excision or even splitting of this large , extremely hard ond crust without damaging adjacent structures was not feasible . other diagnostic methods such as autofluorescence fundus photography , ultrasound b and optical coherence tomography are available , but they do not enable us to assess the size , formation and hardness of ond . in conclusion , this case report demonstrates that ond removal is not feasible in every case . their variability in consistency and hardness makes them unpredictable , thus we can not know in advance which patient is an appropriate candidate for surgery . patient age seems to be an important factor associated with the composition of ond , but also earlier surgery could perhaps yield superior results . in accordance with kapur et al . , we propose that other surgical or ablating laser techniques must be developed to achieve safe removal of extremely hard material , while avoiding damage to adjacent , functionally important and sensitive structures such as optic nerve fibres and retinal vessels .
backgroundto report the case of failed surgical excision of optic nerve drusen ( ond).methodscase report . a 53-year - old woman presented with bilateral ond leading to progressive field defects and le light perception and re 20/25 vision . 
 a vitrectomy was performed on the legally - blind left eye to test the resectability of ond.resultsthe removal of superficial ond failed because the singular - appearing superficial ond presented as one large mass with multiple excrescences on its surface . 
 retinal vessels passed through it , which made an excision impossible.conclusionond can not always be removed surgically , due to their variable consistency and hardness .