Myopia is one of the main risk factors for the onset of open-angle glaucoma. One of the first steps to assess glaucoma occurrence is the measurement of the intraocular pressure (IOP) by the Goldmann applanation tonometry (GAT). Even if this device is considered to be the gold standard for such measurements, it is affected by several sources of errors. Among these, there are the corneal thickness and curvature, both modified by corneal refractive surgery (CRS), that nowadays has become a very popular method to treat refractive errors. Indeed, CRS, by modifying the corneal shape and structure, causes an underestimation of the IOP measurements. In the literature, several IOP correction formulas to utilize with different devices have been proposed to overcome this problem. This paper aims to review the various correction formulas applied to the GAT in the attempt to improve the reliability of this measurement.

Background and Objectives: It has been established that body position can play an important role in intraocular pressure (IOP) fluctuation. IOP has been previously shown to increase significantly when lying down, relative to sitting; this type of investigation has not been extensively reported for the standing (ST) position. Therefore, this study aims to look for eventual significant IOP changes while ST, sitting, and lying down. Materials and Methods: An Icare PRO was used to measure the IOP of 120 eyes of 60 healthy individuals, with age ranging from 21 to 55 years (mean 29.22 ± 9.12 years), in sitting, supine and ST positions; IOP was measured again, 5 min after standing (ST-5m). Results: Mean IOP difference between sitting and ST position was 0.39 ± 1.93 mmHg (95% CI: 0.04 to 0.74 mmHg) (p = 0.027); between sitting and ST-5m, it was −0.48 ± 1.79 mmHg (95% CI: −0.8 to −0.16 mmHg) (p = 0.004); between the sitting and supine position, it was −1.16±1.9 mmHg (95% CI: −1.5 to −0.82 mmHg) (p < 0.001); between the supine and ST position, it was 1.55 ± 2.04 mmHg (95% CI: 1.18 to 1.92 mmHg) (p < 0.001); between supine and ST-5m, it was 0.68 ± 1.87 mmHg (95% CI: 0.34 to 1.02 mmHg) (p < 0.001); and between ST-5m and ST, it was 0.94 ± 1.95 mmHg (95% CI: 0.58 to 1.29 mmHg) (p < 0.001). Mean axial eye length was 24.45 mm (95% CI: 24.22 to 24.69 mm), and mean central corneal thickness was 535.30 μm (95% CI: 529.44 to 541.19 μm). Conclusion: Increased IOP in the ST-5m position suggests that IOP measurements should be performed in this position too. The detection of higher IOP values in the ST-5m position than in the sitting one, may explain the presence of glaucoma damage or progression in apparently normal-tension or compensated patients.

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Background:to compare intraocular pressure (IOP) changes (ΔIOP) between obese patients and normal weight controls in relation to different positions: standing, sitting and supine. Subjects and Methods: Patients candidates for bariatric surgery and normal weight controls. IOP was measured both in patients and controls with Tono-Pen AVIA in different positions. The utilized sequence was: after 5 minutes (5’) in standing position, sitting, supine, 5’supine, and immediately after standing. ΔIOP obtained by supine positions and all other positions were therefore evaluated. Results: Ninenty-two eyes of 46 obese patients (14 males) with an age between 18 and 59 years (mean 38.07±11.51 years) and BMI between 31.84 and 60.65 (mean 41.84±7.05) were evaluated. Forty-eight eyes of 24 normal weight controls (5 males) aged between 23 and 55 (mean 35.21±11.96 years) and BMI between 18.20 and 26.79 (mean 21.04±2.36) were also recruited. In obese patients there were statistically significant differences between IOP in supine position and supine positions 5’ with all other IOP measurements (all P<0.05). There were statistically significant differences between ΔIOP in both supine positions and prolonged standing positions obtained by patients and controls. (P<0.05). Conclusions: In obese patients there is a statistically significant increase in IOP in the supine positions that is significantly greater than normal weight population. BMI is weakly correlated with IOP and ΔIOP in postural changes.