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The Effect of Altitude on Intraocular Pressure in Vitrectomized Eyes with Sulfur Hexafluoride Tamponade by the Friedenwald Method: Rabbit Animal Model

View Article: PubMed Central - PubMed

ABSTRACT

The aim of this study is to assess the change in intraocular pressure after a road trip, in eyes with different levels of filling with gas tamponade. Five rabbit eyes were subject to pars plana vitrectomy and gas tamponade (filling percentage: 25%, 50%, and 100% of nonexpansile SF6, 100% saline solution, and 100% room air). A sixth eye was injected with 0.35 cc of undiluted SF6 without vitrectomy. Guided by global positioning system, they were driven to the highest point of the highway connecting Mexico City with Puebla city and back, stopping every 300 m to assess intraocular pressure. The rabbit's scleral rigidity and estimation for human eyes were done by using the Friedenwald nomogram. Maximum altitude was 3209 m (Δ949 m). There were significant differences in intraocular pressure on the rabbit eyes filled with SF6 at 100%, 50%, 25%, and 100% room air. Per every 100 m of altitude rise, the intraocular pressure increased by 1.53, 1.0046, 0.971, and 0.97 mmHg, respectively. Using the human Friedenwald rigidity coefficient, the human eye estimate for intraocular pressure change was 2.1, 1.8, 1.4, and 1.1 mmHg per every 100 m of attitude rise. Altitude changes have a significant impact on intraocular pressure. The final effect depends on the percentage of vitreous cavity fill and scleral rigidity.

No MeSH data available.


Related in: MedlinePlus

Rabbit model regression lines with 95% confidence interval lines for the study eye with 100 SF6 and 50% SF6. m: meters. SF6: sulfur hexafluoride.
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fig3: Rabbit model regression lines with 95% confidence interval lines for the study eye with 100 SF6 and 50% SF6. m: meters. SF6: sulfur hexafluoride.

Mentions: Table 3 shows the different regression lines per case, as well as the relevant slopes for each rabbit eye. As noted before, the eye in which IOP increased the most, upon altitude variation, was the eye with vitreous cavity 100% filled with SF6: 1.53 mmHg (95% CI: 0.9–2.2) per every 100 m of altitude rise. The eyes with no difference were those with SF6 and no vitrectomy and the eye with vitrectomy and BSS. The statistical significance of such differences on each case was set by comparing the cases' confidence intervals, considering 100% SF6 case as the benchmark, since it showed the highest increase in IOP. The 100% SF6, 50% SF6, 25% SF6, and 100% air study eye behaved similarly, with nonsignificant differences, while the eyes with SF6 and no vitrectomy and the eye with vitrectomy and BSS showed no IOP change in connection with altitude variations. Figures 3 and 4 illustrate these different behaviors in the experimental model for 100% SF6 and 50% SF6 (similar response) and the controls.


The Effect of Altitude on Intraocular Pressure in Vitrectomized Eyes with Sulfur Hexafluoride Tamponade by the Friedenwald Method: Rabbit Animal Model
Rabbit model regression lines with 95% confidence interval lines for the study eye with 100 SF6 and 50% SF6. m: meters. SF6: sulfur hexafluoride.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121576&req=5

fig3: Rabbit model regression lines with 95% confidence interval lines for the study eye with 100 SF6 and 50% SF6. m: meters. SF6: sulfur hexafluoride.
Mentions: Table 3 shows the different regression lines per case, as well as the relevant slopes for each rabbit eye. As noted before, the eye in which IOP increased the most, upon altitude variation, was the eye with vitreous cavity 100% filled with SF6: 1.53 mmHg (95% CI: 0.9–2.2) per every 100 m of altitude rise. The eyes with no difference were those with SF6 and no vitrectomy and the eye with vitrectomy and BSS. The statistical significance of such differences on each case was set by comparing the cases' confidence intervals, considering 100% SF6 case as the benchmark, since it showed the highest increase in IOP. The 100% SF6, 50% SF6, 25% SF6, and 100% air study eye behaved similarly, with nonsignificant differences, while the eyes with SF6 and no vitrectomy and the eye with vitrectomy and BSS showed no IOP change in connection with altitude variations. Figures 3 and 4 illustrate these different behaviors in the experimental model for 100% SF6 and 50% SF6 (similar response) and the controls.

View Article: PubMed Central - PubMed

ABSTRACT

The aim of this study is to assess the change in intraocular pressure after a road trip, in eyes with different levels of filling with gas tamponade. Five rabbit eyes were subject to pars plana vitrectomy and gas tamponade (filling percentage: 25%, 50%, and 100% of nonexpansile SF6, 100% saline solution, and 100% room air). A sixth eye was injected with 0.35 cc of undiluted SF6 without vitrectomy. Guided by global positioning system, they were driven to the highest point of the highway connecting Mexico City with Puebla city and back, stopping every 300 m to assess intraocular pressure. The rabbit's scleral rigidity and estimation for human eyes were done by using the Friedenwald nomogram. Maximum altitude was 3209 m (Δ949 m). There were significant differences in intraocular pressure on the rabbit eyes filled with SF6 at 100%, 50%, 25%, and 100% room air. Per every 100 m of altitude rise, the intraocular pressure increased by 1.53, 1.0046, 0.971, and 0.97 mmHg, respectively. Using the human Friedenwald rigidity coefficient, the human eye estimate for intraocular pressure change was 2.1, 1.8, 1.4, and 1.1 mmHg per every 100 m of attitude rise. Altitude changes have a significant impact on intraocular pressure. The final effect depends on the percentage of vitreous cavity fill and scleral rigidity.

No MeSH data available.


Related in: MedlinePlus