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Anterior chamber interleukin 1β, interleukin 6 and prostaglandin E2 in patients undergoing femtosecond laser-assisted cataract surgery
  1. Li Wang1,2,
  2. Zhe Zhang1,3,
  3. Douglas D Koch2,
  4. Yading Jia1,
  5. Weifang Cao1,
  6. Suhua Zhang1
  1. 1Shanxi Eye Hospital, Taiyuan, Shanxi Province, P. R. China
  2. 2Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA
  3. 3Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, P. R. China
  1. Correspondence to Dr Suhua Zhang, Shanxi Eye Hospital, Taiyuan, Shanxi Province, P. R. China; cfykys{at}163.com

Abstract

Purpose To evaluate the interleukin (IL) 1β, IL-6 and prostaglandin E2 (PGE2) concentrations in aqueous humour in patients undergoing femtosecond laser-assisted cataract surgery.

Methods In 27 eyes of 27 patients undergoing femtosecond laser-assisted cataract surgery (femto group), aqueous humour of 100 μL was collected after laser treatment. In 15 eyes of 15 subjects undergoing routine cataract surgery (control group), aqueous humour of 100 μL was also collected. The IL-1β, IL-6 and Prostaglandin E2 (Human Interleukin 1β, Interleukin 6 and Prostaglandin E2 ELISA Kits, Bio-Swamp Life Science) were used to determine the concentrations of IL-1β, IL-6 and PGE2 in the aqueous humour. All patients were treated with non-steroidal anti-inflammatory drugs prior to surgery.

Results For IL-1β, IL-6 and PGE2, respectively, the mean concentration values in aqueous humour were 25.6, 24.6 and 64.2 pg/mL in the femto group, and 17.1, 15.2 and 45.7 pg/mL in the control group (table 2). Concentrations of IL-1β, IL-6 and PGE2 were significantly higher in the femto group than those in the control group (all p<0.01). There were no significant correlations between concentrations of IL-1β, IL-6 or PGE2 and age, cataract densities, suction time or laser time (all p>0.05).

Conclusions Inflammatory cytokines IL-1β, IL-6 and PGE2 significantly increased after femtosecond laser-assisted cataract surgery, which maybe the cause of intraoperative miosis seen in these patients.

  • Lens and zonules
  • Inflammation
  • Immunology
  • Treatment Lasers
  • Treatment Surgery

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Introduction

Femtosecond laser-assisted cataract surgery introduces many new elements into the surgical procedure1 including the delivery of laser energy into the eye at some interval before the anterior chamber is entered. One side effect of this is postlaser miosis. Comparing pupil size before laser docking and at initiation of phacoemulsification, femtosecond laser capsulotomy and lens softening has been reported to induce miosis of up to 2–3 mm. Nagy and colleagues2 analysed intraoperative complications of the first 100 femtosecond laser-assisted cataract surgeries using the LenSx (Alcon Laboratories, Fort Worth, Texas, USA) and reported that intraoperative miosis occurred in 32% of cases. Bali et al3 reported that 9.5% of the patients had pupil size decrease after femtosecond laser treatment in their initial 200 cases using the LenSx system. The mechanism of this phenomenon is not clear.

Schultz et al4 investigated the intraocular prostaglandin concentrations after femtosecond laser treatment and the potential relationship to miosis. They found a significantly higher level of prostaglandins in the aqueous humour of patients immediately after femtosecond laser treatment, and a significant increase of prostaglandin E2 (PGE2) was also noted. No correlation was noted between age or cataract density and PG/PGE2 level or between corneal incision, suction time or laser time in the femto groups and PG/PGE2 level. In a more recent study, the same group of investigators5 demonstrated that the anterior capsulotomy was the main trigger for an increase of prostaglandins in the aqueous humour immediately after laser-assisted cataract surgery.

Inflammatory cytokines, such as interleukin (IL) 1, IL-6, IL-8 and tumour necrosis factor-α (TNF-α), have been studied in various eye diseases or after surgical procedures in the eye.6–10 To the best to our knowledge, there are no studies evaluating the IL levels in the anterior chamber following femtosecond laser treatment in cataract surgery. In this study, we investigated aqueous humour concentrations of IL-1β, IL-6 and PGE2 in patients undergoing femtosecond laser-assisted cataract surgery.

Patients and methods

Subjects

This study followed the tenets of the Declaration of Helsinki. The study was approved by the Institutional Review Board. After detailed explanation, informed consent was obtained from each patient prior to enrolment.

Prospectively, we enrolled patients undergoing either femtosecond laser-assisted cataract surgery (femto group) using the LenSx laser (Alcon Laboratories) or traditional cataract surgery (control group) between December 2013 and July 2014. One eye from each patient was included. Inclusion criteria were dilated pupil size of 8 mm or larger, no history or current inflammatory eye disease or other ocular diseases, no previous ocular surgery, no rheumatic diseases or other immune diseases, and no use of steroids or non-steroidal anti-inflammatory drugs (NSAIDs) within 6 months, except the eye-drops used within 48 h before the cataract surgery, which is the standard of care at our clinic.

Cataract density was graded using the Lens Opacities Classification System (LOCS) III nuclear opalescence grading score.11

Cataract surgery

All patients in both study and control groups were prescribed pranoprofen 0.1% (Niflan 0.1%, Senju Pharmaceutical Co., Osaka, Japan) and levofloxacin 0.5% (Centaur Pharmaceutical Co., Osaka, Japan) eye-drops for use in the operative eye four times daily beginning 48 h before surgery. Routine use of an NSAID before cataract surgery is the standard of care at our clinic. One experienced surgeon (SZ) performed all surgeries.

In the femto group, capsulotomy, lens fragmentation, the primary cataract incision and one paracentesis incision were performed using the femtosecond laser. The programmed capsulotomy size was 5.2 mm with an incision depth of 600 μm above and below the plane of the capsule (6 µJ pulse energy). The minimal diameter of the dilated pupils was 8 mm. The lens was segmented into four quadrants (cataract grade II) or six quadrants (cataract grade III) (10 µJ pulse energy). A 2.2 mm primary cataract incision was created using the laser (6 µJ pulse energy). Incision design was two-plane with an anterior side cut angle of 80° and a posterior side cut angle of 25°. A 1.2 mm single-plane paracentesis incision was also created (6 µJ pulse energy). About 15 min after laser treatment (range 13–17 min, exact time was not recorded), the incision was opened with blunt dissection, phacoemulsification using the Infiniti Vision System (Alcon Laboratories) was performed, and an aspherical or multifocal intraocular lens (IOL) was implanted in the capsular bag.

In the control group, a 2.2 mm clear corneal incision was made with a 2.2 mm single bevel knife (Alcon Laboratories). A continuous curvilinear capsulorhexis measuring approximately 5.5 mm in diameter was created, and again the Infiniti Vision System was used for phacoemulsification, followed by insertion of an aspheric or multifocal IOL into the capsular bag.

Collection of anterior chamber aqueous humour

In the femto group, at the start of the intraocular portion of the surgery, the paracentesis incision was opened, and 100 μL of aqueous humour was aspirated into a 1 mL syringe. The sample was stored immediately in a freezer with −80°C. In the control group, prior to making the primary cataract incision, similar aqueous aspiration was performed through the paracentesis incision.

Measurements of IL-1β, IL-6 and PGE2 in aqueous humour

To determine the concentrations of IL-1β, IL-6 and PGE2 in the aqueous humour, the Human Interleukin 1β ELISA Kit, Human Interleukin 6 ELISA Kit, and Human Prostaglandin E2 ELISA Kit (Bio-Swamp Life Science, Shanghai, China) were used.

One masked investigator performed experiments on all samples. The ELISA Kits were used in accordance with the manufacturer’s protocol. Briefly, purified Human IL-1β, IL-6 or PGE2 was used to coat the microtiter plate wells to form solid-phase antibody. The aqueous samples were added to individual wells. IL-1β, IL-6 or PGE2 present in the aqueous combined with horseradish peroxidase (HRP)-labelled antibody to form antibody–antigen–enzyme–antibody complex. After washing completely, tetramethylbenzidine (TMB) substrate solution was added, turning the HRP-enzyme-catalysed TMB substrate blue. The reaction was terminated by the addition of a sulphuric acid solution, and the colour change was measured spectrophotometrically at a wavelength of 450 nm. The concentration of IL-1β, IL-6 or PGE2 in the samples was then determined by comparing the optical density (OD) of the samples to the standard curve. From each sample, the concentration of IL-1β, IL-6 or PGE2 was measured two times, and the average was used to represent the concentration of IL-1β, IL-6 or PGE2 in that sample.

Statistical analysis

For sample size calculation, we wish to detect a difference of one SD of differences between two groups. With a significance level of 5% and a test power of 80%, 16 eyes are required in each group. Student's t test was used to compare the concentrations of IL-1β, IL-6 and PGE2 between femto group and control group. Correlation analysis (Pearson correlation for interval data and Spearman's rank correlation for ordinal data) was performed to assess the relationship between the concentrations of IL-1β, IL-6 and PGE2 and age, cataract density, suction time and laser time. χ2 test was used for comparison of frequency parameters. SPSS for Windows (V.21.0) was used. A p value of <0.05 was considered statistically significant.

Results

Twenty-seven eyes of 27 patients were enrolled in the femto group and 15 eyes of 15 subjects were included in the control group. There were no significant differences in age, gender or cataract density between two groups (all p>0.05) (table 1).

Table 1

Characteristics of patients in femtosecond laser-assisted cataract surgery group (femto group) and standard cataract surgery group (control group)

In the femto group and control group, respectively, the mean concentrations in aqueous humour were 25.6 and 17.1 pg/mL for IL-1β, 24.6 and 15.2 pg/mL for IL-6, and 64.2 and 45.7 pg/mL for PGE2 (table 2) (p<0.01 for all three comparisons) (figure 1).

Table 2

Interleukin (IL) 1β, IL-6 and prostaglandin E2 (PGE2) concentrations (mean±SD, range, pg/ml) in anterior chamber aqueous humour

Figure 1

Box plot of aqueous humour concentrations of interleukin (IL) 1β, IL-6 and prostaglandin E2 (PGE2) in eyes with femtosecond laser-assisted cataract surgery (femto) and routine cataract surgery (control) (*significant difference between groups, p<0.01).

There were no significant correlations between concentrations of IL-1β, IL-6 or PGE2 and age, cataract densities, suction time or laser time (all p>0.05).

Discussion

Maintenance of mydriasis is critical to the safety and surgical ease of the cataract procedure.12 Intraoperative miosis can occur following femtosecond laser treatment in cataract surgery. Schultz et al4 investigated the intraocular prostaglandin concentrations after femtosecond laser treatment using the Catalys (Abbott Medical Optics, Santa Ana, California, USA). We are unaware of studies evaluating intraocular prostaglandin concentrations using other laser platforms or analysing other inflammatory cytokines, such as IL-1β and IL-6, in the aqueous humour after femtosecond laser treatment.

In this study, we evaluated aqueous humour concentrations of IL-1β, IL-6 and PGE2 in patients undergoing femtosecond laser-assisted cataract surgery. The concentrations of IL-1β, IL-6 and PGE2 in the anterior chamber were significantly higher in the femtosecond laser group, compared with those in the control group. We chose IL-1β and IL-6 because both have been studied in various eye disease and following certain surgical procedures, and PGE2 was selected because it is a known component of the aqueous humour, and Schultz et al4 ,5 studied its levels in eyes that underwent femtosecond-assisted laser surgery.

Using the Catalys laser platform, Schultz et al4 found that the prostaglandin and PGE2 concentrations significantly increased after femtosecond laser treatment. In femto group and control group, respectively, Schultz et al4 reported mean PGE2 concentrations of 19.2 and 4.5 pg/mL in an earlier cohort of patients, and 60.3 and 11.3 pg/mL in a newer set of patients, indicating that the mean PGE2 concentrations were about 3–4 times higher in the femto group compared with those in control group. In our study using the LenSx, we also found a significantly increased PGE2 concentration of 64.2 pg/mL in the femto group, compared with the concentration of 45.7 pg/mL in the control group. The mean PGE2 concentration was about 40% higher in the femto group than that in control group. The differences between study results may be attributable to: (1) no NSAIDs were used in the study by Schultz et al,4 and pranoprofen 0.1% eye-drops was use in the operative eye four times daily beginning 48 h before surgery in our study, which may lead to increased higher concentration of NSAIDs in the aqueous humour when the samples were obtained; and (2) different laser platforms and different enzyme immunoassay kits used. Further studies are desirable in this area.

Prostaglandins upregulate and downregulate the inflammatory response with different effects on the conjunctiva, sclera, cornea, iris, ciliary body, choroid and retina.13 Prostaglandins are synthesised in the iris and ciliary body after trauma.14 PGE2 is a major transmitter for ocular inflammation. Schultz et al5 investigated a possible correlation between intraocular prostaglandin concentrations and partial steps of laser-assisted cataract surgery. They found that the anterior capsulotomy was the main trigger for an increase of prostaglandins in the aqueous humour immediately after laser-assisted cataract surgery. Miosis during cataract surgery is thought to be partly related to an increase in the concentration of prostaglandins.15 NSAIDs work by their ability to inhibit cyclooxygenase (COX), which ultimately decreases the production of prostaglandins.16 The patients in our study were pretreated with NSAIDs, but not with prostaglandin antagonists. It would be interesting to evaluate aqueous humour concentrations of these cytokines in patients with open-angle glaucoma with long-term use of topical prostaglandin agonists.

The inflammatory cytokine IL-1 is an important mediator of inflammation and immunity.17 Li and colleagues18 demonstrated that hyperosmotic stress induces expression and production of IL-1β by primary cultured human limbal epithelial cells. Dry-eye disease is accompanied by an increase in the proinflammatory forms of IL-1 (IL-1α and mature IL-1β) in tear fluid.19 Laser trabeculoplasty induces the expression and secretion of IL-1β within the first 8 h after treatment.20 In our study, we found that the level of IL-1β in anterior chamber aqueous humour was significantly higher in the femto group.

IL-6 plays a central role in host defence against environmental stress such as infection and injury.21 Under physiological conditions, IL-6 is barely detectable in serum (1–5 pg/mL).22 ,23 In non-infectious inflammations such as burn or traumatic injury, damage-associated molecular patterns from damaged or dying cells stimulate toll-like receptors to produce IL-6.24 Significant elevation of IL-6 has been found in ocular fluids derived from patients with refractory/chronic uveitis. Gao and colleagues25 reported elevated IL-6 following femtosecond laser-assisted laser in situ keratomileusis and refractive lenticule extraction. One study suggested that IL-6 was involved in promoting corneal wound healing.26 In our study, we found detectable IL-6 in anterior chamber aqueous humour, and the level was significantly higher in the femto group.

Our results showed that there were no significant correlations between concentrations of IL-1β, IL-6 or PGE2 and age, cataract densities, suction time or laser time, consistent with report from Schultz et al4 that there was no correlation between the prostaglandin concentration in aqueous humour and suction time, laser time or cataract densities. In this study, pupil diameters were not recorded; therefore, we could not assess correlations between concentrations of IL-1β, IL-6 or PGE2 and changes in pupil diameter. Further studies are needed to investigate the mechanism of inflammatory cytokine and prostaglandin increases in aqueous humour following femtosecond laser-assisted cataract surgery.

The limitation of this study was that anterior chamber aqueous fluid was obtained at different stages of the procedure in the femto and control groups. This was unavoidable due to the nature of the surgical procedures, specifically the need to inject either an ophthalmic viscosurgical device or balanced salt solution prior to making a manual capsulotomy. An area of further research would be to compare the effect of blade versus femtosecond corneal incisions on endothelial cells adjacent to the incision, considering recent studies that have shown that femtosecond laser capsulotomies induce greater amount of apoptosis of adjacent lens capsule epithelial cells, compared with manual continuous curvilinear capsulorhexis.27 ,28 Further studies are also desirable to investigate other inflammatory cytokines, such as IL-8 and TNF-α, in aqueous humour following femtosecond laser-assisted cataract surgery.

In conclusion, our study demonstrated that the concentrations of IL-1β, IL-6 and PGE2 in the aqueous humour were significantly higher in the femtosecond laser group, compared with those in the control group. Further studies are desirable to identify which steps of laser-assisted cataract surgery increase the concentration of inflammatory cytokines and to investigate the changes of inflammatory cytokines and prostaglandins in aqueous humour postoperatively in eyes with femtosecond laser treatment, presumably in animal studies.

References

Footnotes

  • LW and ZZ are contributed equally.

  • Funding This study was supported in part by Department of Science and Technology research grant (No.20140313014-9), Shanxi Province, and by an unrestricted grant from Research to Prevent Blindness, New York, NY.

  • Competing interests DDK is a consultant for Abbott Medical Optics and Alcon Laboratories.

  • Patient consent Obtained.

  • Ethics approval Eye Research Institution of Shanxi Province.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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