contracting the disease. However, appellant failed to discharge the burden of proof required by the law.   Based on medical findings, Open Angle Glaucoma arises as a complication of chronic obstruction of aqueous humor reabsorption in the trabecular meshwork. It is usually asymptomatic and only rarely causes ocular pain or corneal edema. The treatment is primarily medical. Surgery to prevent permanent visual loss is necessary in only a minority of patients (Ref.: Harrisons Principles of Internal Medicine, 11th edition, p. 71).   As suggested by the foregoing medical findings, the cleaning of chemicalspill-oil on deck and the spraying of [naphtha] chemical inside the tank were not predisposing factors in the contraction of Open Angle Glaucoma. Thus, we believe that the respondent System correctly ruled against the compensability of [petitioners] ailment.[9] An appeal from the adverse decision was filed before the CA.[10] On August 17, 1999, however, the petition was denied due course and the CA accordingly dismissed the case on the ground that petitioner failed to adduce substantial evidence supporting the conclusion that the working conditions as a seaman increased the risk of contracting his chronic open angle glaucoma.[11]   Petitioners motion for reconsideration was subsequently denied;[12] hence, this recourse.   The lone issue presented for consideration is whether the work of petitioner as a seaman contributed even in a small degree in or had increased the risk of contracting his chronic open angle glaucoma.[13]   While petitioner admits that chronic open angle glaucoma is not one of those listed as occupational diseases under the law he nonetheless maintains that the cause of glaucoma is still unknown and predisposition thereto is due to both physical and emotional factors. In his case, petitioner asserts that he had been exposed to these elements for 18 years during his employment. He claims that as a utility staff he performed odd jobs without fail such as cleaning chemical-spill-oil on deck, slat dislodging, and spraying naphtha chemical and washing dirt and rusts inside the tank. According to him, these strenuous tasks required climbing, bending