title: Not only pregnancy but also the number of fetuses in the uterus affects intraocular pressure.
abstract: OBJECTIVE
  To investigate whether, intraocular pressure (IOP) is affected when there is a second fetus in the uterus during pregnancy.
  
  
  METHODS
  Eighty eyes of 40 twin pregnancies (TwPs), 80 eyes of 40 singleton pregnancies (SiPs) and 80 eyes of 40 non-pregnant females (NoPs) were included in the study.
  
  
  METHODS
  Repeated measurements analysis of variance with two factors, one-way analysis of variance (ANOVA) and the Tukey's multiple comparison test were used.
  
  
  RESULTS
  The mean IOP (MIOP) values in TwPs were 14.29 ± 1.28, 11.48 ± 1.20, and 9.81 ± 1.36 mmHg and the MIOP values in SiPs were 14.42 ± 0.95, 13.12 ± 0.75, and 10.97 ± 0.89 mmHg in subsequent trimesters. The MIOP values in NoPs were 14.77 ± 1.18, 14.92 ± 1.33, and 15.08 ± 0.89 mmHg in subsequent 3-month measurements. The results show that the MIOP values for the TwPs group were significantly lower than the SiPs in all trimesters.
  
  
  CONCLUSIONS
  During pregnancy, the number of fetuses in the uterus is an indirectly important factor that influences the decrease in IOP. We hypothesize that the increased ocular hypotensive effect of TwPs is most likely related to the presence of higher levels of hormones, particularly estrogen, progesterone and relaxin compared with SiPs.
authors.affiliation: Department of Ophthalmology, Van Ipekyolu Government Hospital, 65100, Van, Turkey.
authors.forename: Metin
authors.initials: M
authors.lastname: Saylik
authors.forename: Safiye A
authors.initials: SA
authors.lastname: Saylık
mesh_terms: D000328:Adult; D005260:Female; D005333:Fetus; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D009798:Ocular Hypertension / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000503:physiopathology*; D011272:Pregnancy, Multiple / Q000502:physiology*; D014065:Tonometry, Ocular; D014599:Uterus