Intraoperative intraocular pressure fluctuation during standard phacoemulsification in real human patients

Comparison of macular changes and visual outcomes between femtosecond laser-assisted cataract surgery and conventional phacoemulsification surgery for high myopic cataract patients

BACKGROUND

To evaluate differences in log MAR best-corrected visual acuity (BCVA) improvement and postoperative central foveal thickness (CFT) and choroidal thickness (CT) changes between conventional phacoemulsification surgery (CPS) and femtosecond laser-assisted cataract surgery (FLACS) for high-myopia cataracts.

METHODS

This was a retrospective and observational study. One hundred and two eyes of 102 patients with high-myopia cataracts were examined. CPS was performed in 54 eyes, and FLACS was performed in 48 eyes. All eyes underwent logMAR BCVA, CFT and CT of three different sectors preoperatively and one week and six months postoperatively.

RESULTS

The logMAR BCVA improved significantly after surgery in both groups (both P < 0.001), but no difference was observed in BCVA improvement between the groups (P = 0.554). Moreover, no significant differences were reflected in the changes in CFT, nasal 1 mm CT or temporal 1 mm CT between the two groups, and only subfoveal choroidal thickness (SFCT) in the CPS group decreased significantly compared with that in the FLACS group at any postoperative time (P = 0.003 and 0.026). AL, preoperative logMAR BCVA, and CT of the three regions exhibited a notable correlation with postoperative BCVA (all P < 0.05) according to univariate logistic regression analysis. However, only the AL, preoperative logMAR BCVA and SFCT remained significant in the multivariate model. Postoperative logMAR BCVA revealed a positive correlation with AL and preoperative logMAR BCVA but a negative correlation with SFCT.

CONCLUSIONS

FLACS was not superior to CPS in improving BCVA but had less impact on SFCT in the treatment of high-myopia cataracts. Eyes with a longer AL, worse preoperative logMAR BCVA and thinner SFCT had a high risk of worse postoperative BCVA.

Comparison of intraocular pressure fluctuation and glaucoma progression rate between phakic and pseudophakic eyes in pseudoexfoliation glaucoma

The management of patients with concurrent pseudoexfoliation glaucoma (PXG) and cataract is challenging given its worse prognosis compared to other glaucoma types and the increased risk associated with cataract surgery. In this retrospective study, we investigated the long-term outcomes of cataract surgery in patients with PXG. We enrolled patients with PXG who had undergone cataract surgery at least 2 years previously and compared them with mean deviation (MD) matched patients with phakic eyes. The results showed that both groups experienced a decrease in MD, with the group of pseudophakic eyes exhibiting a significantly higher rate of decline (-2.15 ± 2.66 dB/year vs. -0.86 ± 0.95 dB/year; P = 0.040). Similarly, there was a trend towards more rapid thinning of the retinal nerve fiber layer in the pseudophakic group (-2.92 ± 2.34 μm/year vs. -1.79 ± 1.71 μm/year; P = 0.074). No significant differences in the intraocular pressure parameters were observed between the two groups. Multivariate analysis revealed that pseudophakic lens status was significantly associated with a faster rate of MD decline in patients with PXG (regression coefficient, -1.391; P = 0.022). These findings underscore the importance of close monitoring of patients with pseudophakic PXG to effectively manage glaucoma progression.

Contralateral Forced Eyelid Closure Increases Intraocular Pressure

OBJECTIVES

The purpose of the study was to describe the influence of contralateral forced eyelid closure on intraocular pressure (IOP).

METHODS

Twenty-one healthy volunteers with no ophthalmic history had their IOP measured in the supine position to simulate the intraoperative environment. Intraocular pressure was measured with a handheld tonometer over three scenarios: (1) both eyes in a relaxed state, (2) eyelid speculum in the right eye with both eyes open and relaxed, (3) eyelid speculum in the right eye with the fellow eye squeezing tightly.

RESULTS

Intraocular pressure significantly increased with forced contralateral eyelid squeezing compared with the relaxed state by a mean of 7.71±5.08 mm Hg (95% Confidence Interval of 5.40-7.37), P<0.001.

CONCLUSIONS

Contralateral eyelid squeezing can significantly increase intraoperative IOP measurements.

Injection time related to intraocular pressure using a CO2 driven preloaded injector: An experimental laboratory study

PURPOSE

Experimental study to measure the intraocular lens (IOL) injection time and injection speed at different intraocular pressure (IOP) settings when using the AutonoMe® injector.

METHODS

In this experimental study, following phacoemulsification in porcine cadaver eyes, a trocar was inserted at pars plana with a connected infusion and IOPs of 20, 50 and 80 mmHg were generated by altering the infusion height. Twelve CO2 gas-driven injectors were used to implant an IOL via a corneal incision of 2.2 mm. For each IOP setting, the duration of the IOL injection and the injection speed was measured by analyzing a video recording of the procedure.

RESULTS

The mean ±SD injection time (seconds) was 4.47±0.50 at 20 mmHg, 4.98±0.55 at 50 mmHg and 5.47±0.20 at 80 mmHg. The mean ±SD injection speed (millimeters per seconds) was 1.36±0.15 at 20 mmHg, 1.22±0.14 at 50 mmHg and 1.10±0.04 at 80 mmHg. There was a significant (p<0.05) difference between the 20 and 80 mmHg groups in mean injection duration and injection speed.

CONCLUSION

The CO2 gas driven injector allows a safe IOL injection even at elevated IOP. Although the implantation time is slightly extended at higher IOPs, this does not seem to be clinically relevant. No IOL damage was observed at these pressure settings.

Modeling of the increased intraocular pressure effect on changes in the stress state of the eyeball’s internal structures

The aim of the study was creating a model and evaluating the effect of elevated IOP in the anterior chamber during phacoemulsification on the changes in the stress state of various ocular structures. Materials and methods.A simplified axial symmetrical anatomical model of the eyeball was created using the finite element method. Using the Deform software package, the deformation problem was worked out by calculating the redistribution of the excess pressure in the anterior chamber during phacoemulsification, on the changes in the stress state of different ocular structures.Results. At processing of modeling results, data were obtained on redistribution of the excess pressure delivered to the anterior chamber towards its decrease in the posterior pole area. The pressure level amounted to 0.85 % of excess pressure applied. The findings are supported by few animal experiments. Conclusions.Proposed model of the increased IOP level effect on changes in the stressed state of various ocular structures demonstrates that the autoregulation mechanism maintaining ocular blood flow at a constant level includes a compensating mechanism for a steep IOP increase due to elastic properties of the vitreous body. This model allows calculating the redistribution of pressure in different parts of the eyeball, depending on the state of resilient-elastic properties of the vitreous, as well as on avitreal eyes, and in patients with silicone oil tamponade.