Quantification of hydroxyl radical produced during phacoemulsification

Ultrasound energy consumption and macular changes with manual and femtolaser-assisted high-fluidics cataract surgery: a prospective randomized comparison

PURPOSE

The purpose of the study was to compare ultrasound (US) consumption and central macular thickness (CMT) and volume changes with manual and femtosecond laser (FSL)-assisted cataract nucleus workup.

METHODS

Sixty patients scheduled for immediate sequential bilateral surgery underwent a prospective randomized intraindividual comparison of nucleus sector fragmentation performed manually in one eye and with low-energy FSL assistance in the partner eye, followed by high-fluidics phacoaspiration with a maximum US power of 30%. Ultrasound (US) energy consumption and macular thickness and volume were compared as measured by intraoperative effective phacoemulsification time (EPT) and high-resolution spectral domain optical coherence tomography pre- and 1 week, 3 weeks and 6 weeks postoperatively. Results are presented as means ± SD or medians [min; max].

RESULTS

Fifty-two patients completed the full follow-up. For the manual and FSL-assisted groups, nuclear hardness was almost identical with a mean LOCS III grade of 2.44 ± 1.08 and 2.50 ± 1.00 (p = 0.371). Median EPT was 1.40 [0.2; 8.3] and 1.25 [0.2; 9.4] seconds. Median preoperative CMT was 276.50 [263.25; 289.75] µm and 276.00 [262.00; 290.00] µm. Median postoperative CMT was 278.00 [260.50; 288.00] versus 275.50 [264.00; 290.50] µm at 1 week, 279.50 [266.75; 292.25] versus 280.00 [266.50; 294.50] µm at 3 weeks and 280.50 [268.00, 293.75] versus 279.50 [264.75; 295.25] µm at 6 weeks. Differences in CMT and total macular volume between the groups were not statistically significant at any point in time.

CONCLUSION

Femtosecond laser (FSL) prefragmentation of the nucleus into six sectors did not reduce US energy consumption compared with manual splitting of the nucleus into four quadrants in this particular surgical setting. Sectorial FSL-prechopping with the low-energy FSL used had no additional impact on postoperative macular thickness and volume.

[Frequency and type of macular edema after cataract surgery in patients with glaucoma]

Cataract is one of the common causes of reversible vision loss in people older than 50 years. Currently, the only way to treat it effectively is phacoemulsification with simultaneous implantation of an intraocular lens - a method that minimizes the amount of surgical trauma and the number of intra- and postoperative complications. Nevertheless, the problem of prevention and timely diagnosis of pathological changes in the retina, which may develop after extraction of cataracts, and in particular - macular edema, remains relevant. This problem becomes especially important when it comes to patients with concomitant cataract and glaucoma who use local antihypertensive drugs - in particular, prostaglandin analogues - for a long time. Having common properties with inflammatory mediators, in some cases they can cause vasodilation, increase vascular permeability and contribute to the development of exudative processes. Drugs of this group can cause impairment of the hematophthalmic and hematoretinal barriers provoking the development of cystoid macular edema, including in the early postoperative period after cataract extraction. As described by S. Irvine in 1953, macular edema is related to late postoperative complications and remains one of the main causes of visual impairment after lens removal. The review provides information about some studies concerning the effect of prostaglandin derivatives on the postoperative period after phacoemulsification. At this time, there is no consensus on this matter.

Effects of Hydrogen in Prevention of Corneal Endothelial Damage During Phacoemulsification: A Prospective Randomized Clinical Trial

PURPOSE

Hydrogen (H₂) has been reported to scavenge free radicals, particularly the hydroxyl radical (·OH). Ultrasound oscillation in an aqueous solution produces ·OH. Our recent study demonstrated that H₂ dissolved in an irrigation solution prevented corneal endothelial damage during phacoemulsification in an animal model. We examined the effects of H₂ during clinical phacoemulsification.

DESIGN

A single-center, prospective, randomized, double-masked clinical trial.

METHODS

Thirty-two patients who had cataracts of similar nucleus hardness in both eyes (age: 75.4±7.68 years; 17 males, 15 females) were recruited. Phacoemulsification was performed using a solution of dissolved H₂ in one eye, and a conventional solution in the contralateral eye. Endothelial cell density (ECD) at the center of the cornea was measured using noncontact specular microscopy preoperatively and at 1 day, 1 week, and 3 weeks postoperatively.

RESULTS

Reduction rates of ECD (mean ± standard deviation) were 16.0%±15.7% at 1 day, 15.4%±16.1% at 1 week, and 18.4%±14.9% at 3 weeks in the control group, compared to 6.5%±8.7% at 1 day (P = .003), 9.3%±11.0% at 1 week (P = .039), and 8.5%±10.5% at 3 weeks (P = .004) in the H₂ groups. These rates were significantly smaller in the H₂ group at all time points.

CONCLUSIONS

H₂ dissolved in irrigation solution reduced corneal endothelial damage during phacoemulsification. This suggests that a considerable part of the corneal endothelial damage during phacoemulsification is caused by oxidative stress, and that H₂ is useful in clinical phacoemulsification.

Glutathione homeostasis and functions: potential targets for medical interventions

Glutathione (GSH) is a tripeptide, which has many biological roles including protection against reactive oxygen and nitrogen species. The primary goal of this paper is to characterize the principal mechanisms of the protective role of GSH against reactive species and electrophiles. The ancillary goals are to provide up-to-date knowledge of GSH biosynthesis, hydrolysis, and utilization; intracellular compartmentalization and interorgan transfer; elimination of endogenously produced toxicants; involvement in metal homeostasis; glutathione-related enzymes and their regulation; glutathionylation of sulfhydryls. Individual sections are devoted to the relationships between GSH homeostasis and pathologies as well as to developed research tools and pharmacological approaches to manipulating GSH levels. Special attention is paid to compounds mainly of a natural origin (phytochemicals) which affect GSH-related processes. The paper provides starting points for development of novel tools and provides a hypothesis for investigation of the physiology and biochemistry of glutathione with a focus on human and animal health.

Determining the local origin of hydroxyl radical generation during phacoemulsification

PURPOSE

To determine the local origin of hydroxyl radicals during phacoemulsification using an ultrasonic phacoemulsification device that includes longitudinal and torsional modalities.

SETTING

Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA.

DESIGN

Experimental study.

METHODS

Experiments were conducted using the Infiniti Vision System and Ozil handpiece. Hydroxyl radical concentrations during longitudinal and torsional phacoemulsification were quantitated as malondialdehyde (MDA) determined spectrophotometrically using the deoxyribose assay. The difference between the total concentration found in the aspirated solution at steady-state concentrations and the pre-aspirate levels deductively determined the concentration of MDA formed along the interior of the sonicating tip. The time to reach 50% of steady state as a function of reaction vessel volume was determined.

RESULTS

The mean maximum for torsional ultrasound at 100% amplitude was 7.70 nM ± 0.38 (SD), 91.1% of which was generated outside the tip. During longitudinal ultrasound at 100% power, MDA concentration in the aspirated solution was 29.5 ± 0.3 nM, 71.6% of which was generated outside the tip. The time (seconds) to reach 50% of maximum for longitudinal ultrasound using 5 mL, 10 mL, and 20 mL reaction vessels was 12.6 ± 1.5, 21.0 ± 1.5, and 25.3 ± 3.4, respectively.

CONCLUSION

Although a significantly greater proportion of the hydroxyl radicals generated during ultrasound modality were formed outside the phaco tip (91.1% torsional; 71.6% longitudinal), torsional ultrasound generated only about one-fourth the amount of MDA as longitudinal ultrasound in total and about one-third that generated outside the tip (7.02 nM versus 21.1 nM).

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Hydroxyl free radical production during torsional phacoemulsification

PURPOSE

To quantitate free radical generation during phacoemulsification using an ultrasonic phacoemulsification device that includes a torsional mode and evaluate tip designs specific to the torsional mode.

SETTING

Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA.

DESIGN

Experimental study.

METHODS

Experiments were performed using the Infiniti Vision System and OZil handpiece. Hydroxyl radical concentrations in the aspirated irrigation solution during torsional phacoemulsification were quantitated as nanomolar malondialdehyde (nM MDA) and determined spectrophotometrically using the deoxyribose assay.

RESULTS

The mean free radical production during phacoemulsification with torsional modality at 100% amplitude was 30.1 nM MDA ± 5.1 (SD) using a 0.9 mm 45-degree Kelman tapered ABS tip. With other tip designs intended for use with the torsional modality, free radical production was further reduced when fitted with the 0.9 mm 45-degree Kelman mini-flared ABS tip (13.2 ± 5.6 nM MDA) or the 0.9 mm 45-degree OZil-12 mini-flared ABS tip (14.3 ± 6.7 nM MDA). Although the measurements resulting from the use of the latter 2 tips were not statistically significantly different (P ≈ .25), they were different from those of the tapered tip (P<.0001).

CONCLUSIONS

The MDA concentration in the aspirated irrigation solution using the torsional modality was approximately one half that reported for the handpiece's longitudinal modality in a previous study using the same bent-tip design (Kelman tapered, P<.0001). The level of MDA was further reduced approximately one half with torsional-specific tips.