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Cord R. Huchzermeyer, Udo Reulbach, Nikolaos Bellios, Barbara Link, Robert Lämmer, Antonio Bergua, Folkert K. Horn, Christian Y. Mardin, Jünemann Anselm; Glaucoma Suspects with Primary Melanin Dispersion Syndrome Exhibit Phase Lag of Diurnal Rhythm of Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2011;52(14):673.
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To compare diurnal rhythm of intraocular pressure (IOP) of normal subjects, patients with ocular hypertension (OHT) and patients with primary melanin dispersion syndrome (MDP) from the Erlangen Glaucoma Registry using cosinor analysis.
For the Erlangen Glaucoma Registry (ClinicalTrials.gov number NCT00494923), annual 24h-IOP profiles with measurements at 7 am, noon, 5 pm, 9 pm and midnight were obtained. For this study, fifty-three subjects without signs of manifest glaucoma who have had at least five such profiles with no local or systemic antiglaucomatous therapy were identified from the Registry. To analyze characteristics of the rhythm of IOP, cosine curves were fitted to the IOP profiles using the least-squares method. Because at least five cosine curves were available for each subject, the presence of a significant individual mean angle was identified using the Rayleigh test. Differences in phase timing between groups were analyzed using the Hotelling test.
Of the fifty-three subjects studied, 31 had no manifest ocular disease (control group), 12 had MDP and 11 had OHT. None of them developed glaucomatous changes of the optic disc or visual field defects during follow-up. Altogether, 368 IOP profiles were available from these patientens. The acrophase coefficient was significant in 277 cosine curves fitted to these profiles (75.2 %). The overall mean acrophase of all subjects was 10:22 a.m. The majority showed a mean acrophase between 6 a.m. and noon. In many subjects, acrophase shows large variations from year to year. Therefore, a signficant individual mean direction of acrophases from different IOP profiles was found in only 18 of 53 subjects (34%). When only subjects with a significant mean individual acrophase where considered, subjects with MDP showed a significant phase lag of two hours and seven minutes (12:28 p.m. vs 10:21 a.m.).
In our study, patients with MDP showed a significant phase lag compared to normal subjects and patients with OHT. It is more likely that this is caused by peripheral mechanisms than by changes in the endogenous clock. Thus, further research on IOP patterns in MDP might offer new insights into the effector mechanisms of circadian rhythm of IOP.
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