Purpose To evaluate the changes in re tinal nerve fiber layer(RNFL)thickness in the first 16weeks after acute primary angle closure(APAC)using scanning laser polarimetry(SLP)-Design Prospective,observational case series.Par-ticipants Thirty-seven Asian subje cts with APAC.Methods For all cases,APAC had resolved afte r treatment,and the study was conducted during the follo w-up period after the acute episode.Using the GDx Nerve Fi ber Analyzer(Laser Diagnostic Technologies,San Diego,CA),the RNFL was assessed in both eyes 2weeks after APAC,and again after16weeks.The SLP parameters were com pared between week 2and week 16within affected and fellow eyes.A multiple logistic regression analy sis was carried out to an-alyze factors likely to influence RN FL outcome.Main out-come measures Superior and inferior average RNFL thick-ness.Results The mean age of study su bjects was 60.1±10.3years(range,46-91years),and most subjects were female(68%)and Chinese(86%).In APAC eyes,the superior average RNFL thic kness decreased from63.8±13.6μm to 61.4±11.2μm(P=0.04)and the inferior average RNFL thickness decreased from 69.5±14.4μm to 66.3±12.6μm(P=0.005).There was also a decrease in inferior ratio(P=0.008)-and ellipse modulation(P=0.02).In the fellow eyes,there was no difference found between week 2and w eek 16for any of the SLP parameters studied.Logisti c regression analysis showed no significant association b etween developing a 10%reduction in either superior or i nferior RNFL thick-ness with age,gender,history of isc hemic risk factors,duration of symptoms during APAC,th e level of present-ing intraocular pressure(IOP),or the development of a rise in IOP between study visits.Con clusions After an episode of APAC,superior and inferior average RNFL thickness was found to decrease sign ificantly from week 2to week 16. Purpose To evaluate the changes in reinal nerve fiber layer (RNFL) thickness in the first 16 weeks after acute primary angle closure (APAC) using scanning laser polarimetry (SLP) -Design Prospective, observational case series. Par-ticipants Thirty-seven Asian subje cts with APAC.Methods For all cases, APAC had resolved afte r treatment, and the study was conducted during the follo w-up period after the acute episode. Using the GDx Nerve Fi ber Analyzer (Laser Diagnostic Technologies, San Diego, CA) , the RNFL was assessed in both eyes 2 weeks later APAC, and again after 16 weeks. The SLP parameters were com pared between week 2 and week 16 with in affected and fellow eyes. A multiple logistic regression analy sis was carried out to an-alyze factors likely to influence RN FL outcome. Main Out-come measures Superior and inferior average RNFL thick-ness. Results The mean age of study su bjects was 60.1 ± 10.3 years (range, 46-91 years), and most subjects were female (68%) and Chinese ( 86%). In APAC eyes, the superior average RNFL thic kness decreased from 63.8 ± 13.6 μm to 61.4 ± 11.2 μm (P = 0.04) and the inferior average RNFL thickness decreased from 69.5 ± 14.4 μm to 66.3 ± 12.6 μm (P = 0.005). Where was also a decrease in inferior ratio (P = 0.008) -and ellipse modulation (P = 0.02). The fellow eyes, there was no difference found between week 2 and w eek 16 for any of the SLP parameters studied. Logistic c regression analysis showed no significant association b etween developing a 10% reduction in either superior or i nferior RNFL thick-ness with age, gender, history of isc hemic risk factors, duration of symptoms during APAC, th e level of present-ing intraocular pressure (IOP), or the development of a rise in IOP between study visits. Con clusions After an episode of APAC, superior and inferior average RNFL was was found to decrease significantly from week 2 to week 16.