To introduce the concept of a stage 0 macular hole based on optical coherence tomographic observations of the vitreoretinal interface in fellow eyes of patien ts with unilateral idiopathic macular holes, and to evaluate the subsequent risk of progression to a full thickness macular hole. Retrospective observational c ase series. Ninety four patients with a unilateral stage 2, 3, or 4 full thick ness macular hole. The medical records of patients with a unilateral macular hol e diagnosed between 1994 and 2000 at the New England Eye Center were reviewed. D evelopment of a full thickness macular hole in the fellow eye on biomicroscopic fundoscopy or optical coherence tomography (OCT). In 27 (28.7%) of 94 clinical ly normal fellow eyes, OCT detected an abnormality of the vitreoretinal interfac e but normal foveal anatomy. The vitreoretinal abnormalities were further subcla ssified into severe (4 eyes), moderate (8 eyes), and mild (15 eyes) based on the intensity and morphology of the OCT signal. One of the 4 (25%) severe cases pr ogressed to a full thickness macular hole, 4 of the 8(50%) moderate cases beca me full thickness macular holes, and no (0%) mild cases progressed to a full thickness macular hole. Severe and moderate eyes seemed to share characteristic features on OCT that increased their risk of macular hole development (stage 0 m acular hole). The macular hole free survival at 48 months was 94%for stage 0 ne gative patients, versus 54%for stage 0 positive patients. Univariate analysis r evealed that the presence of a stage 0 macular hole was significantly associated with an almost 6 fold increase in the risk of macular hole formation (relative risk: 5.8, 95%confidence interval: 1.16 28.61, P=0.03). A stage 0 macular hole has a normal biomicroscopic appearance clinically, but has salient features on OCT as a result of oblique vitreous traction. Optical coherence tomographic find ings consist of a normal foveal contour and normal retinal thickness and must in clude the presence of a preretinal, minimally reflective, thin band inserting ob liquely on at least one side of the fovea. The presence of a stage 0 macular hol e in the fellow eye is a significant risk factor for the development of a second macular hole. To introduce the concept of a stage 0 macular hole based on optical coherence tomographic observations of the vitreoretinal interface in fellow eyes of patien ts with unilateral idiopathic macular holes, and to evaluate the subsequent risk of progression to a full thickness macular hole. Retrospective observational c ase series. Ninety four patients with a unilateral stage 2, 3, or 4 full thick ness macular hole. The medical records of patients with a unilateral macular integrity diagnosed between 1994 and 2000 at the New England Eye Center were reviewed. D evelopment of In a 27 (28.7%) of 94 clinical ly normal fellow eyes, OCT detected an abnormality of the vitreoretinal interfac e but normal foveal anatomy. The vitreoretinal abnormalities were further subcla ssified into severe (4 eyes), moderate (8 eyes), and mild (15 eyes) based on the intensity and morphology of the OCT si gnal. One of the 4 (25%) severe cases pr ogressed to a full thickness macular hole, 4 of the 8 (50%) moderate cases beca me full thickness macular holes, and no (0%) mild cases progressed to a full Thick macular hole. Severe and moderate eyes showed to share characteristic features on OCT that increased their risk of macular hole development (stage 0 m acular hole). The macular hole free survival at 48 months was 94% for stage 0 ne gative patients, versus 54% for stage 0 positive patients. Univariate analysis r evealed that the presence of a stage 0 macular hole was significantly associated with an almost 6 fold increase in the risk of macular hole formation (relative risk: 5.8, 95% confidence interval: 1.16 28.61 , P = 0.03). A stage 0 macular hole has a normal biomicroscopic appearance clinically, but has salient features on OCT as a result of oblique vitreous traction. Optical coherence tomographic find ings consist of a normal foveal contour and normal retinal thickness and must in clude the presence of a preretinal, minimally reflective, thin band inserting ob liquely on at least one side of the fovea. The presence of a stage 0 macular hol e in the fellow eye is a significant risk factor for the development of a second macular hole .