To analyze the clinical course and outcomes of vitrectomy for severe vitreous hemorrhage of unknown etiology and to determine the primary cause of hemorrhage during the surgical process.

The medical records of patients who showed vitreous hemorrhage of Grade IV at their initial visit with no remarkable ophthalmologic or trauma history were reviewed retrospectively. All included patients underwent vitrectomy for severe vitreous hemorrhage for which a primary cause was not revealed before the surgery. The authors investigated the postoperative visual outcome, complications, and etiology of vitreous hemorrhage that was determined during the surgical process. We also analyzed the detailed intraoperative and postoperative funduscopic findings of patients with poor postoperative visual outcomes (BCVA < 20/200).

Among the 50 eyes of 50 patients, the causes of vitreous hemorrhage included: branch retinal vein occlusion (48%), central retinal vein occlusion (16%), age-related macular degeneration (12%), retinal tear (8%), diabetic retinopathy (4%), rhegmatogenous retinal detachment (4%), Terson's syndrome (2%), Eales' disease (2%) and unknown causes (4%). The mean best-corrected visual acuity (BCVA) before surgery was 2.17 ± 0.53 (log MAR) and it was recovered to 0.64 ± 0.58 (log MAR) 6 months after the surgery ( p < 0.001). The branch retinal vein occlusion showed better visual outcome than other disease entities. On funduscopic examination of the patients with poor visual outcome whose postoperative BCVA was poorer than 20/200, macular ischemia, macular degeneration, macular edema, submacular hemorrhage, tractional retinal detachment (including macular), or optic nerve atrophy were verified.

After the vitrectomy for severe vitreous hemorrhage of unknown origin, pathologic findings of macular or irreversible optic nerve atrophy showed poor postoperative BCVA. Of all the causes of vitreous hemorrhage that were revealed after the surgery, branch retinal vein occlusion was the most common etiology of this condition and showed the most favorable visual outcome, comparatively.