What Is The Expected Change In Iop At 4-8 Weeks After Phacoemulsification When The Preop Measured Iop Is 20Mmhg?

To determine a) the significance of any association between intraocular pressure measured at preop (IOP) and the change in this pressure (ΔIOP) observed between 4 and 8 weeks after uneventful routine phacoemulsification, b) if a significant association is found then the limits of agreement (LoA) between the predicted and actual change in IOP would be calculated.

Kyiv City Clinical Ophthalmological Hospital “Eye Microsurgery Center”, Ukraine

Intraocular pressure (mmHg) was assessed using pneumotonometer (Tomey FT-1000, Tomey Corp.) at preop and all postop sessions following routine unremarkable phacoemulsification with nontoric IOL implantation. All surgeries were performed under topical anaesthesia (2.2mm incision at 12o’clock), postop injection of dexamethasone (subconjunctival) and betamethasone (parabulbar), topical levofloxacin, oftan-dexamethason, indomethacin, dexpanthenol, trehalose and hyaluronic acid.

Only data from the treated eye (n=51, right eyes in bilateral cases) were harvested for analysis.

Mean (±sd, 95% CI) IOP reduced significantly (p<0.001) from 17.04mmHg (±3.80, 16.00-18.08) at preop to 14.52 mmHg (±3.19, 13.64-16.28).

A significant correlation was revealed between the change in IOP observed at 4-to-8 weeks postop and the IOP (x)  measured at preop. The relationship is described as follows,

ΔIOP = 0.82x-11.48 (r²=0.501, n=51, p<0.01). LOA between actual predicted values for ΔIOP = ±6.11mmHg

For preop IOP = 20mmHg, ΔIOP = 4.95mmHg (predicted range in ΔIOP = -1.2 to 11.1mmHg).

As expected, the mean IOP reduced significantly after phacoemulsification.

The predicted change in IOP is about 5mmHg when the preop value is 20mmHg, but the likely change sits somewhere between -1.2mmHg and 11.1mmHg. The r² value indicates the chances of correctly predicting the change in IOP is 50%.