A pharmaceutical composition comprising at least one compound selected from the group consisting of tryptase inhibitors, selected from the group consisting of nafamostat mesilate, APC-366 (CAS REGISTRY NO: 178925-65-0), N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride (a free form of CAS REGISTRY NO 158921-85-8), APC-2059 (CRA-2059) (CAS REGISTRY NO: 433337-07-6), AVE-5638 (CAS REGISTRY NO: 1032129-37-5), AVE-8923 (CAS REGISTRY NO: 1032129-43-3), RWJ-56423 (CAS REGISTRY NO: 287182-50-7, 2-pyrrolidinecarboxamide, 1-acetyl-N-[ -4-[(aminoimino-methyl)amino]-1-(2-benzothiazolylcarbonyl)butyl]-4-hydroxy-,(2S,4R)-(CA INDEX NAME)), RWJ-58643 (CAS REGISTRY NO: 287183-00-0), 2-pyrrolidinecarboxamide, 1-acetyl-N-[4-[(aminoiminomethyl)amino]-1-(2-benzothiazolylcarbonyl)butyl]-4-hydroxy-,(2S,4R)-(CA INDEX NAME)), anti-tryptase antibodies, peptide/protein or nucleic acid molecules that inhibit tryptase activity such as aptamers, and siRNA and miRNA, including antisenses targeting tryptase DNAs and mRNAs, and mast cell stabilizers, selected from the group consisting of cromoglycic acid (cromolyn), pemirolast, amlexanox, tranilast, acitazanolast, ibudilast, repirinast, tazanolast, suplatast, picumast, tioxamast, quinotolast, andolast, nedocromil, tagorizine, AM-3301 (ME-3301), TA-5707 (CAS REGISTRY NO: 83282-09-1), 2-pyridinecarboxamide, 6-methyl-N-2H-tetrazol-5-yl-,sodium salt (1:1) (CA INDEX NAME) (a free form of CAS REGISTRY NO 83282-08-0), batebulast, quazolast, AL-136 (KP-136) (CAS REGISTRY NO: 76239-32-2), 8-(hexyloxy)-3-(1H-tetrazol-5-yl)coumarin)doqualast, MAR-99 (CAS REGISTRY NO: 98772-05-5), 5-pyrimidinecarboxylic acid, 1,6-dihydro-2-[[2-(two-methylpropoxy)-phenyl]amino]-6-oxo-(CA INDEX NAME)), asobamast, AS-35 (CAS REGISTRY NO: 108427-72-1), 4H-pyrido[1,2-a]pyrimidin-4-one, 9-[(4-acetyl-3-hydroxy-2-propylphenoxy)methyl]-3-(2H-tetrazol-5-yl)-(CA INDEX NAME), HSR-6071 (PTPC) (CAS REGISTRY NO: 111374-21-1), 2-pyrazinecarboxamide, 6-(1-pyrrolidinyl)-N-2H-tetrazol-5-yl-(CA INDEX NAME)), AHR-5333B (CAS REGISTRY NO: 60284-71-1), ethanone, 1-[4-[3-[4-[bis(4-fluorophenyl)hydroxymethyl]-1-piperidinyl]propoxy]-3-methoxyphenyl]-(CA INDEX NAME)), CI-949 (CAS REGISTRY NO: 121530-58-3), L-arginine, compd. with 5-methoxy-3-(1-methylethoxy)-1-phenyl-N-2H-tetrazol-5-yl-1H-indole-2-carboxamide (1:1) (CA INDEX NAME) (a free form of CAS REGISTRY NO 104961-19-5), tetrazolast, acreozast, CI-959 (CAS REGISTRY NO: 104795-68-8), benzo[b]thiophene-2-carboxamide, 5-methoxy-3-(1-methylethoxy)-N-2H-tetrazol-5-yl-,sodium salt (1:1) (CA INDEX NAME) (a free form of CAS REGISTRY NO 104795-66-6), cromproxate, LCB-2183 (CAS REGISTRY NO: 158454-08-1), Zy-15106 (CAS REGISTRY NO: 3106-85-2), N-acetyl aspartyl glutaminic acid, bamaquimast, CGP-25875 (6-butyryl-1-ethyl-4-hydroxy-7-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid), PNU-142731A (CAS REGISTRY NO: 214212-38-1), ethanone, 2-(2,4-di-1-pyrrolidinyl-9H-pyrimido[4,5-b]indol-9-yl)-1-(1-pyrrolidinyl)-,hydrochloride (1:1) (CA INDEX NAME) (free form of CAS REGISTRY NO 214212-39-2), doxantrazole (doxantrol), oxatomide, olopatadine, elbanizine, noberastine, mequitazine, ketotifen, azelastine, astemizole, terfenadine, emedastine, epinastine, ebastine, cetirizine, fexofenadine, bepostatine besilate, levocabastine, loratadine, and levocetirizine, for use in a method for therapy or prophylaxis of retinopathy of prematurity, said method comprising: detecting marker substances that can be released by degranulation of mast cells from biological samples derived from a subject, wherein the biological sample is blood or plasma and the marker substance is tryptase; determining whether the subject is a patient needing therapy or prophylaxis of retinopathy of prematurity on the basis of a detected amount of the marker substances; and administering said pharmaceutical composition to a patient needing therapy or prophylaxis of retinopathy of prematurity by an amount effective for the therapy or prophylaxis therefor by oral administration, intranasal administration, airway administration, percutaneous administration, intravenous administration, intramuscular administration, subcutaneous administration, percutaneous administration, or intraperitoneal administration. detecting marker substances that can be released by degranulation of mast cells from biological samples derived from a subject, wherein the biological sample is blood or plasma and the marker substance is tryptase; determining whether the subject is a patient needing therapy or prophylaxis of retinopathy of prematurity on the basis of a detected amount of the marker substances; and administering said pharmaceutical composition to a patient needing therapy or prophylaxis of retinopathy of prematurity by an amount effective for the therapy or prophylaxis therefor by oral administration, intranasal administration, airway administration, percutaneous administration, intravenous administration, intramuscular administration, subcutaneous administration, percutaneous administration, or intraperitoneal administration.