We found the level of fluctuation to be the best with Travatan [3. We had the most experience with Xalatan [range 3. Other medications also have been proven to reduce fluctuation. Alphagan and Trusopt tend to have higher fluctuations, above 5 mmHg. The prostaglandins would be the first-line therapy in terms of mean reduction of pressure fluctuations. They tend to do the best in terms of IOP efficacy for those two parameters," Dr. Stewart explains.
Surgical Options. Stewart says there is too much unknown about fluctuation for it to be a factor in considering glaucoma surgery. We just don't know that much about it," Dr. A recent study from Dr. Stewart and Professor Konstas showed that a successful trabeculectomy would reduce the fluctuations to about 2.
The clinical significance needs to be explored and we are not saying you need to do surgery first," he says. Asrani concurs that if medication or combinations of medications do not help then ultimately surgery is an option. Therefore, typically trabeculectomy is the treatment of last resort because it does work," he says. Future Outlook. While current monitoring systems provide a snapshot of IOP fluctuation and variation, more data are needed to better understand the whole picture of this complicated subject.
Weinreb says, "In the future, we need and hope for a continuous hour monitor of intraocular pressure because it changes not only hour-to-hour or minute-to-minute. IOP is changing instantaneously in everybody at all times.
The best means for us to understand the relationship between IOP and glaucoma would be to have something that captures IOP continuously," he says. Continued research may answer some of the remaining questions, says Dr. For example, he and his colleagues measure IOP in the habitual positions sitting during the day and supine during the nocturnal period to best mimic what happens in most individuals who are sitting or standing during the day and supine while they sleep.
In a supine position, IOP is always higher than in a sitting position, he says. So there is something more than just the supine position that accounts for the peak pressure," Dr. Weinreb explains. It may be related to changes in the autonomic nervous system," he adds.
Ophthalmology ; Mean intraocular pressure and progression based on corneal thickness in primary open-angle glaucoma. J Ocul Pharmacol Ther Feb;22 1 The relationship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol. Large diurnal fluctuations in intraocular pressure are an independent risk factor in patients with glaucoma. J Glaucoma ; This report describes the results of a single-centre study based on the retrospective analysis of the records of over 1, age-matched male and female at-risk but assumed non-glaucomatous subjects.
Statistical analysis of the collated data indicated that subject age group was not a major variable: however gender and the time of IOP assessment were both significant features. For recordings between the hours of Our cosinor model fitted values followed the observed average value for rhythms of habitual-position IOP and seated IOP, respectively.
No values suspicious of being outliers or influential points were detected. Figure 2. Table 2. Difference between daytime mean and nighttime mean. There were similar differences between these two groups in the hour peak, trough, fluctuation, and standard deviation IOP parameters, but not in the average hour IOP Table 3. Table 3. Figure 3. However, In contrast, Figure 4. There were no evident associations between body height and hour IOP parameters, including the magnitude of nocturnal IOP elevation in the habitual position and HFA indices, according to Pearson's correlation analysis.
Estimate of the type II error was between 0. After adjustment for possible confounders for glaucoma age, CCT, and refractive error , no parameter was significantly associated with the VF indices. Table 4. Finally, peak hour habitual-position IOP and peak nocturnal IOP could be estimated from the diurnal measurement of IOP with the following regression equations based on our multiple linear regression analysis:.
The coefficient of determination R 2 provides a measure of how well future outcomes are likely to be predicted by the model. R 2 of peak hour habitual-position and peak nocturnal habitual-position with the simple linear regression equations were 0.
This study is unique in that our study population consisted of a relatively large number of Asians Koreans with NTG who underwent hour IOP measurement. This finding suggests that nocturnal elevation of IOP is primarily due to postural changes, in agreement with the results of Hara and Tsuru, 6 who measured seated and supine IOP by noncontact tonometry over 24 hours.
Other researchers have also speculated that nocturnal IOP elevation is due to changes of body posture that lead to increased episcleral venous pressure. Although the analysis of our entire population indicated that mean IOP was highest at night when the patients were supine, we also identified three major IOP rhythms among our patients: diurnal acrophase Mosaed et al.
Although the exact physiologic mechanisms underlying nocturnal IOP change are unknown, our study and the study of Mosaed et al. Interestingly, a significant portion of our NTG eyes Renard et al. In contrast to our present findings and those of Mosaed et al. However, direct comparison of different studies may be problematic because of the differences in study populations, number of enrolled subjects, study designs, and definition of NTG.
Another crucial finding of our study was that 9. This percentage is similar to that reported by Hara and Tsuru. Barkana et al. Kiuch et al. In our recent studies of NTG, 18 , 19 we found that hour ocular perfusion pressure OPP fluctuation, due to the significant blood pressure BP dip at night, was the most consistent risk factor for both severity and progression of glaucoma.
We suggest that a future longitudinal study should investigate the influence of various hour IOP parameters in conjunction with OPP, including those that accompany posture changes, on glaucoma progression. A study by Magnaes 20 showed that the intracranial CSF pressure at eye level falls by an average of 14 mm Hg as a subject changes position from the left lateral decubitus posture to the sitting or standing posture.
Although the change in CSF pressure may be related to glaucomatous damage of hydrostatic causes with different body height, body height was found not to be associated with VF indices. Thus, this increase in CSF pressure at night may act as a stable support of the lamina cribrosa against the nocturnal rise in IOP. This may also explain our finding that IOP changes after postural changes at night did not show a significant association with glaucomatous damage.
Estimation of the hour maximum IOP in untreated glaucoma patients is clinically relevant. Again, differences in the study designs, sample sizes, and study population may explain these discrepancies.
Although a clinician can estimate or extrapolate the peak hour habitual-position IOP in untreated NTG patients by measuring the highest daytime IOP, the absolute magnitudes of the difference between the highest daytime IOP and the peak hour habitual and nocturnal IOP were relatively small nearly 3 and 4 mm Hg IOP, respectively.
Enrollment of NTG subjects according to our study design may have contributed to a relatively small range of IOP change over 24 hours. A limitation of using our estimation formula is its main applicability to subjects who show a nocturnal acrophase pattern, whereas clinicians often do not know the pattern of IOP elevation in each patient. Further studies are needed to assess the utility of various proposed models for estimation of hour maximum and nocturnal IOP in NTG subjects.
Our study has a few limitations. Calculation of habitual-position IOP using a handheld tonometer TonoPen XL; Mentor Ophthalmics may be subject to different accuracy and variability, although the tonometer has shown good agreement with the GAT in eyes with normal corneas in previous studies. Moreover, we tested the agreement of the measurement with that of the GAT with NTG patients or suspects and the agreement was excellent. A second limitation is the inability to generalize our findings to other POAG and NTG subjects with different definitions or race, such as those studies referenced, since 2-hour monitoring of habitual-position IOP was performed in Korean patients with maximum multiple untreated IOPs less than 22 mm Hg during office hours using the GAT in our study.
Hourly measurements may have made the modeling of IOP rhythms and prediction of the peak hour habitual position and nocturnal IOP more precise and physiological. However, waking patients up every hour at night for IOP measurement could lead to nonphysiological acquisition of IOP. Another limitation is that no control group was included in the present study.
As an increase in IOP during nocturnal period in supine position may be a physiological phenomenon, it remains unclear whether the NTG patients with nocturnal acrophase have a pathologic or physiological IOP curve. Finally, measurement of habitual-position IOP using the tonometer may not provide the best physiological hour ocular tension data in our NTG subjects, as our IOP measurement was based on the theoretical assumption sitting during the day and supine at night.
VF indices were not correlated with nocturnal IOP elevation in the habitual position. Our study suggests that clinicians should consider the daytime peak IOP to estimate the hour or the nighttime maximum habitual-position IOP. Disclosure: Y. Lee , None; M. Kook , None; S. Joe ; None; J. Na , None; S.
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