adequate to justify a conclusion, that the nature of his employment or working conditions increased the risk of contracting the ailment or that its progression or aggravation was brought about thereby.   Perusal of the records, however, regrettably reveals petitioners failure to adduce any proof of a reasonable connection between his work as a seaman and the chronic open angle glaucoma he had contracted. At the most, he merely claims that he performed odd jobs without fail cleaning chemical-spill-oil on deck, slat dislodging, and spraying naphtha chemical and washing dirt and rusts inside the tank strenuous tasks which according to him required climbing, bending over and running for so many times. Adding thereto were the perils of the sea and the homesickness he said he experienced which allegedly caused emotional strains on his part.   Other than positing the foregoing, petitioner presented no competent medical history, records or physicians report to objectively substantiate the claim that there is a reasonable nexus between his work and his ailment. Without saying more, his bare allegations do not ipso facto make his illness compensable. Awards of compensation cannot rest on speculations or presumptions. The claimant must present concrete evidence to prove a positive proposition.[19]   The necessity of establishing the supposed work connection is all the more crucial in the face of the fact that the readily-available medical literature would appear to consistently indicate that open angle glaucoma is brought about by several factors other than the purported physical and emotional strains, such as aging, race, family history, nearsightedness or farsightedness, prolonged corticosteroid use, nutritional deficiencies, brain chemical abnormalities, injuries, infection or abnormalities in the eye, and medical conditions such as diabetes, high blood pressure or heart disease.[20] Therefore, to easily attribute to the physical and emotional strains allegedly attendant in petitioners job as a seaman the chronic open angle glaucoma he is currently suffering is evidently to oversimplify an