Journal of Refractive Surgery

Original Article 

Changes in Prostaglandin Levels in Patients Undergoing Femtosecond Laser-Assisted Cataract Surgery

Tim Schultz, MD; Stephanie C. Joachim, MD; Mathias Kuehn; H. Burkhard Dick, MD, PhD

Abstract

PURPOSE:

To investigate the intraocular prostaglandin concentrations after femtosecond laser treatment and the potential relationship to miosis.

METHODS:

Aqueous humor was collected from patients after femtosecond laser pretreatment and at the beginning of routine cataract surgery. The total prostaglandin and the prostaglandin E2 concentrations were measured in two independent studies using an enzyme-linked immunoassay.

RESULTS:

A significantly higher level of prostaglandins was noted in the aqueous humor of patients immediately after femtosecond laser treatment. This could be confirmed in two studies consisting of independent patient populations (study I: control = 17.3 ± 4.0 pg/mL [n = 22], femtosecond laser [femto] = 182.1 ± 38.1 pg/mL [n = 22], P = .0001, and study II: control = 17.5 ± 1.4 pg/mL [n = 37], femto: 377.1 ± 83.6 pg/ mL [n = 35], P = .00004). A significant increase of prostaglandin E2 was noted in two measurements (study III: control = 4.5 ± 1.9 pg/mL [n = 13], femto: 19.2 ± 2.5 pg/mL [n = 20], P = .0002, and study IV: control = 11.3 ± 1.6 pg/mL [n = 35], femto: 60.3 ± 16.1 pg/mL [n = 36], P = .004). No correlation was noted between age or cataract density and prostaglandin/prostaglandin E2 level or between corneal incision, suction time, or laser time in the femto groups and prostaglandin/prostaglandin E2 level.

CONCLUSIONS:

Prostaglandins rise immediately after femtosecond laser treatment. Future patients should perhaps be treated with non-steroidal anti-inflammatory drugs to maintain mydriasis before undergoing femto-second laser treatment for cataract surgery.

[J Refract Surg. 2013;29(11):742–747.]

From the Institute for Vision Science (TS, HBD) and Experimental Eye Research Institute (SCJ, MK), Ruhr University Eye Hospital, Bochum, Germany.

Dr. Dick was a member of OptiMedica’s Medical Advisory Board. The remaining authors have no financial or proprietary interest in the materials presented herein.

Drs. Schultz and Joachim contributed equally to this work and should be considered as equal first authors.

AUTHOR CONTRIBUTIONS

Study concept and design (HBD, SCJ, TS); data collection (HBS, SCJ, MK, TS); analysis and interpretation of data (HBD, SCJ, TS); drafting of the manuscript (SCJ, MK, TS); critical revision of the manuscript (HBD, SCJ); statistical expertise (SCJ); supervision (HBD)

Correspondence: Tim Schultz, MD, Institute of Vision Science, Ruhr University Eye Hospital, In der Schornau 23-25, 44892 Bochum, Germany. E-mail: tim.schultz@kk-bochum.de

Received: May 18, 2013
Accepted: July 23, 2013

Abstract

PURPOSE:

To investigate the intraocular prostaglandin concentrations after femtosecond laser treatment and the potential relationship to miosis.

METHODS:

Aqueous humor was collected from patients after femtosecond laser pretreatment and at the beginning of routine cataract surgery. The total prostaglandin and the prostaglandin E2 concentrations were measured in two independent studies using an enzyme-linked immunoassay.

RESULTS:

A significantly higher level of prostaglandins was noted in the aqueous humor of patients immediately after femtosecond laser treatment. This could be confirmed in two studies consisting of independent patient populations (study I: control = 17.3 ± 4.0 pg/mL [n = 22], femtosecond laser [femto] = 182.1 ± 38.1 pg/mL [n = 22], P = .0001, and study II: control = 17.5 ± 1.4 pg/mL [n = 37], femto: 377.1 ± 83.6 pg/ mL [n = 35], P = .00004). A significant increase of prostaglandin E2 was noted in two measurements (study III: control = 4.5 ± 1.9 pg/mL [n = 13], femto: 19.2 ± 2.5 pg/mL [n = 20], P = .0002, and study IV: control = 11.3 ± 1.6 pg/mL [n = 35], femto: 60.3 ± 16.1 pg/mL [n = 36], P = .004). No correlation was noted between age or cataract density and prostaglandin/prostaglandin E2 level or between corneal incision, suction time, or laser time in the femto groups and prostaglandin/prostaglandin E2 level.

CONCLUSIONS:

Prostaglandins rise immediately after femtosecond laser treatment. Future patients should perhaps be treated with non-steroidal anti-inflammatory drugs to maintain mydriasis before undergoing femto-second laser treatment for cataract surgery.

[J Refract Surg. 2013;29(11):742–747.]

From the Institute for Vision Science (TS, HBD) and Experimental Eye Research Institute (SCJ, MK), Ruhr University Eye Hospital, Bochum, Germany.

Dr. Dick was a member of OptiMedica’s Medical Advisory Board. The remaining authors have no financial or proprietary interest in the materials presented herein.

Drs. Schultz and Joachim contributed equally to this work and should be considered as equal first authors.

AUTHOR CONTRIBUTIONS

Study concept and design (HBD, SCJ, TS); data collection (HBS, SCJ, MK, TS); analysis and interpretation of data (HBD, SCJ, TS); drafting of the manuscript (SCJ, MK, TS); critical revision of the manuscript (HBD, SCJ); statistical expertise (SCJ); supervision (HBD)

Correspondence: Tim Schultz, MD, Institute of Vision Science, Ruhr University Eye Hospital, In der Schornau 23-25, 44892 Bochum, Germany. E-mail: tim.schultz@kk-bochum.de

Received: May 18, 2013
Accepted: July 23, 2013

A new generation of femtosecond lasers was introduced for cataract surgery in ophthalmology in 2009. These devices combine an ultra-short pulsed laser with an integrated imaging system to perform certain steps of the cataract procedure.1 Various studies have demonstrated advantages of this new technology. These benefits include higher precision and repeatability of the anterior capsulotomy, as well as a reduction in ultrasound power during phacoemulsification.1–3 Furthermore, lower postoperative corneal swelling, less macula edema in the first week after surgery, better lens centration, and fewer internal aberrations were reported when using femtosecond lasers.4–7 Overall better refractive outcomes might be possible with these new devices.

However, the intraocular effects after lens treatment are to some extent unknown. Bali et al. reported that in their initial set of 200 cases the pupil size decreased in 19 eyes (9.5% of the patients receiving surgery) after femtosecond laser treatment using the LenSx femtosecond laser system (Alcon Laboratories, Aliso Viejo, CA).8 It is well known that small pupils can increase the difficulty of the surgery and lead to higher complication rates during lens removal.9

Prostaglandins are high potential bioregulatory substances that are synthesized by cyclooxygenase 1 and 2 from arachidonic acid.10,11 In the eye, their principal source is the non-pigmented epithelial layer of the ciliary body. They appear in the aqueous humor after different mechanical and thermal stimuli.12,13 In several studies, the pupil contraction rate was reduced during phacoemulsification by the preoperative application of prostaglandin synthesis inhibitors (non-steroidal anti-inflammatory drugs [NSAIDs]).14–17 Furthermore, the intraocular prostaglandin E2 concentration was reduced in patients after NSAID treatment.18 Therefore, the authors assumed an involvement of prostaglandins in surgical pupil contraction.

To find out more about a potential laser-induced miosis during femtosecond laser-assisted cataract surgery, we investigated the prostaglandin concentration in patients’ aqueous humor immediately after femtosecond laser treatment.

Patients and Methods

Aqueous humor samples were obtained from patients undergoing routine microincision cataract surgery and femtosecond laser-assisted cataract surgery. The samples were collected at the beginning of the surgery and stored at −80°C until used. The tenets of the Declaration of Helsinki were observed and approval by the local ethics committee was granted. The Lens Opacities Classification System III (LOCS III) nuclear opalescence grading score was used.19 Preoperative nuclear opalescence was estimated by one physician using a Haag Streit BQ 900 Slitlamp (Haag-Streit, Bern, Switzerland) at maximum illumination.

Inclusion Criteria

Patients were scheduled for cataract surgery on one eye and allocated to one of four study groups based on the following inclusion criteria. In the control group (study I to IV), patients with a significant cataract (LOCS III grades II to V) and without any other ocular diseases were assigned for traditional microincision phacoemulsification. Similarly, patients with significant cataract and no ocular diseases were included in the femtosecond laser (femto) group (study I to IV) when they were scheduled for femtosecond laser-assisted cataract surgery.

Exclusion Criteria

In both groups (study I to IV), patients with a history of inflammatory eye disease, previous ocular surgery or trauma, age-related macular degeneration, diabetic and hypertensive retinopathy, any kind of glaucoma, pseudoexfoliation, dilated pupil size smaller than 6 mm, rheumatic diseases, and the use of NSAIDs or steroids in the past 6 months were excluded.

Femtosecond Laser-Assisted Cataract Surgery and Control Surgery

All surgeries were performed at the Institute for Vision Science, Ruhr University Eye Clinic, Bochum, Germany. The manual and the femtosecond laser part was done by one experienced surgeon (HBD). Both groups received the same topical medication preoperatively. Medical mydriasis was induced using topical 0.5% tropicamide eye drops (Mydriaticum; Stulln Pharma, Stulln, Germany) and 5.0% phenylepherine eye drops (Neo-Synephrine; Ursapharm, Saarbrücken, Germany) instilled three times within 1 hour prior to surgery. Oxybuprocain eyedrops (Conjuncain EDO 0.4%; Bausch & Lomb, Rochester, NY) were used three times for topical anesthesia 30 minutes preoperatively.

In the femto group, capsulotomy and lens fragmentation were conducted with the help of a femtosecond laser for cataract surgery (Catalys Precision Laser System; OptiMedica, Sunnyvale, CA). In the larger studies (study II and IV), the primary cataract incision was also performed with the laser system in approximately half of the cases. In all cases, the set capsulotomy size was 4.8 to 5.0 mm and the programmed pulse energy was 4 μJ with an incision depth of 600 μm. The lens was segmented into quadrants and softened with a grid spacing of 350 μm (10 μJ pulse energy). The laser primary incision was a triplanar incision with an anterior side cut angle of 90° and a posterior side cut angle of 30°. The pulse energy was set to 5 μJ. Within 4 to 5 minutes after laser treatment, the incision was blunt opened or a 2.75-mm clear corneal primary incision was made with a Blumenthal knife (BD Ophthalmic Systems, Bidford on Avon, United Kingdom) under sterile conditions and approximately 100 μL of aqueous humor was collected. The samples were directly stored at −80°C in a freezer located in the operating room. Subsequently, nuclear disassembly was conducted and an intraocular lens was implanted. In all cases, the total laser time (from the beginning of the laser firing until laser off) and the total suction time (from suction on until suction off) was measured.

In the control group, a 2.75-mm clear corneal primary incision was made in exactly the same manner as described for the femto group. Similar to the femto group, approximately 100 μL of aqueous humor was collected and immediately stored at −80°C. Routine manual cataract surgery with implantation of an intraocular lens was performed.

Measurements of Prostaglandin in Aqueous Humor

All samples from one study (study I or II) were measured at the same time by the same investigator with the same standard preparation to avoid inter-user or plate variability. Prostaglandin concentrations were determined using commercially available enzyme immunoassay kits (Cayman Chemicals, Ann Arbor, MI). The enzyme immunoassay kits were used according to the provided manufacturer’s instructions. The assays were performed on 96-well plates, precoated with a monoclonal mouse anti-rabbit antibody. Briefly, serial dilutions of a prostaglandin standard (15.6 to 2,000 pg/ mL) and controls were prepared. A total of 50 μL of standards, controls, and samples (undiluted aqueous humor) were pipetted into individual wells, followed by addition of a prostaglandin-acetylcholinesterase conjugated tracer and a monoclonal rabbit anti-prostaglandin antibody. After 18 hours of incubation at 4°C, the plates were rinsed with the provided washing buffer. Ellmans reagent was added to each well and incubated on an orbital shaker at room temperature in the dark for 1 hour. The measurement was performed at a wavelength of 405 nm and analyzed using a Microplate Reader (AESKU.Reader with Gen5 ELISA Software; AESKU.DIAGNOSTICS, Wendelsheim, Germany).

Measurements of Prostaglandin E2 in Aqueous Humor

Samples from studies III and IV were used to determine prostaglandin E2 (PGE2) levels in aqueous humor. Commercially available enzyme immunoassay kits (Cayman Chemicals) were used. The procedure is analogue to the procedure of the prostaglandin-enzyme immunoassay kits described above, except the 96-well plates are precoated with a polyclonal goat anti-mouse antibody that binds to a PGE2-specific monoclonal mouse antibody and the standard ranges from 7.8 to 1,000 pg/mL.

Statistical Analysis

All statistical analyses were performed using a commercial predictive analytics software (Statistica, Version 10; Statsoft, Tulsa, OK). Significance in prostaglandin concentration between study and control groups was calculated using Student’s t test. A P value less than .05 was considered statistically significant.

Pearson’s correlation coefficient (R) was calculated for the analyses of the associations between the patient’s individual prostaglandin or prostaglandin E2 level and patient’s age or cataract density for patients in studies II and IV. The correlation coefficients were also calculated for the associations between individual prostaglandin or prostaglandin E2 levels and the kind of corneal incision (manual or femto laser), total suction time, or total laser time for the patients of the femto groups.

Results

Patients were randomly assigned to one of the four studies. In total, 220 aqueous humor samples were analyzed: 113 samples of patients undergoing femtosecond laser surgery and 107 samples of patients before conventional cataract surgery (Table 1). There was no difference between the patient groups with regard to age, sex, or cataract density.

Clinical Patient Data

Table 1:

Clinical Patient Data

Total Prostaglandin Concentrations in Aqueous Humor

The total prostaglandin concentration was analyzed in the human aqueous humor immediately after femtosecond laser treatment and in the control group. In study I, the total prostaglandin concentration was significantly higher in the femto group (182.1 ± 38.1 pg/mL) than in the control group (17.3 ± 4.0 pg/mL; P = .0001; Figure 1A and Table A, available in the online version of this article). To confirm this finding, a second analysis (study II) was performed. Again, a significantly higher prostaglandin concentration was measured in the femto group (377 ± 83.6 pg/mL) compared to the control group (17.5 ± 1.4 pg/mL; P = .00004) using an enzyme immunoassay (Figure 1B and Table A).

(A) Study I. Mean prostaglandin levels in aqueous humor of control (conventional cataract surgery) and femto (femtosecond laser-assisted surgery) groups (n = 22 in each group). Measured prostaglandin levels were significantly higher in the femto group compared to the control group (P = .0001). (B) Study II. Prostaglandin levels in aqueous humor of control and femto groups of a later study (n = 35 to 37 in each group). Prostaglandin levels were significantly higher in the femto group (P = .00004). Values are median ± 25% to 75% ± range.

Figure 1.

(A) Study I. Mean prostaglandin levels in aqueous humor of control (conventional cataract surgery) and femto (femtosecond laser-assisted surgery) groups (n = 22 in each group). Measured prostaglandin levels were significantly higher in the femto group compared to the control group (P = .0001). (B) Study II. Prostaglandin levels in aqueous humor of control and femto groups of a later study (n = 35 to 37 in each group). Prostaglandin levels were significantly higher in the femto group (P = .00004). Values are median ± 25% to 75% ± range.

PGE2 Concentrations in Aqueous Humor

Prostaglandin E2 levels were measured in the first study in 20 patients in the femto group and 13 patients in the control group using an enzyme immunoassay kit (study III). The femto group had a significantly higher mean PGE2 concentration (19.2 ± 2.5 pg/mL) compared to the control group (4.5 ± 1.9 pg/mL) (P = .0002; Figure 2A and Table A). This elevation of PGE2 immediately after femtosecond laser surgery could be confirmed through a repeated analysis using a new set of patient samples. Study IV also revealed high levels of PGE2 in the femto group (60.3 ± 16.1 pg/mL) compared to the control group (11.3 ± 1.6 pg/mL; P = .004; Figure 2B and Table A).

(A) Study III. Plots of the mean prostaglandin E2 levels in aqueous humor of control (conventional cataract surgery; n = 13) and femto (femtosecond laser-assisted surgery; n = 20) groups. A significantly higher level of prostaglandin E2 was observed in the femto group (P = .0002). (B) Study IV. A second analysis of prostaglandin E2 levels in a larger study population revealed similar results (n = 35 to 36 in each group). The mean prostaglandin E2 levels were significantly higher in patients immediately after femtosecond laser application (P = .004). Values are median ± 25% to 75% ± range.

Figure 2.

(A) Study III. Plots of the mean prostaglandin E2 levels in aqueous humor of control (conventional cataract surgery; n = 13) and femto (femtosecond laser-assisted surgery; n = 20) groups. A significantly higher level of prostaglandin E2 was observed in the femto group (P = .0002). (B) Study IV. A second analysis of prostaglandin E2 levels in a larger study population revealed similar results (n = 35 to 36 in each group). The mean prostaglandin E2 levels were significantly higher in patients immediately after femtosecond laser application (P = .004). Values are median ± 25% to 75% ± range.

Correlation Analyses

No correlation was noted between the patient’s age and the prostaglandin concentrations in aqueous humor in study II (r = 0.05, r2 = 0.002; P = .7; Figure A, available in the online version of this article). Correlation coefficients between patient’s age and prostaglandin E2 levels were not statistically significant in study IV (r = −0.03; r2 = 0.001; P = .8; Figure A).

There was no significance in correlation coefficients between the cataract densities and prostaglandin levels in aqueous humor in study II (r = 0.10, r2 = 0.009; P = .4; Figure A). There was also no correlation between the cataract densities and prostaglandin E2 concentrations (r = 0.05; r2 = 0.003; P = .7; Figure A).

We additionally evaluated whether the method of performing the corneal primary incision (femtosecond laser or manually cutting) affected the prostaglandin or prostaglandin E2 levels in the aqueous humor of the femto group. A primary laser incision was performed in 17 of 35 patients in study II and in 22 of 36 patients in study IV. We observed no significant correlation between the method of performing the corneal incision and the prostaglandin levels in aqueous humor (study II: r = 0.11; r2 = 0.013; P = .5; Figure B, available in the online version of this article). There was also no correlation between corneal incision procedure and individual prostaglandin E2 levels in the femto group of study IV (r = −0.07, r2 = 0.004; P = .7; Figure B).

No significant correlation was found between the individual suction times and the prostaglandin concentrations in the femto group of study II (r = 0.04, r2 = 0.001; P = .8; Figure B) or the suction times and prostaglandin E2 levels in the femto group of study IV (r = 0.09, r2 = 0.007; P = .6; Figure B).

Furthermore, there was no correlation between the individual laser time and prostaglandin concentrations in study II (r = 0.05, r2 = 0.003; P = .8; Figure B) or between laser time and prostaglandin E2 levels in study IV (r = 0.25, r2 = 0.062; P = .1; Figure B).

Discussion

In the current study, we evaluated alterations in aqueous humor prostaglandin levels due to femtosecond laser pretreatment of eyes with cataract. We noted a significant increase in total prostaglandin in the samples of the femto group (P < .001). Additionally, significantly higher levels of prostaglandin E2 were observed right after the femtosecond laser-assisted procedure (P < .005). Both findings were confirmed in two independent studies each.

Prostaglandins are synthesized in the iris and ciliary body after trauma.20 They are high potential inflammation-regulating substances with different effects on the conjunctiva, sclera, cornea, iris, ciliary body, choroid, and retina.21 Because of their close correlation to inflammation, we analyzed the prostaglandin levels immediately after femtosecond laser treatment. We observed significantly higher levels of total prostaglandin in aqueous humor in these patients (Figure 1). This could mean laser treatment triggers inflammation in the eye, but the location of the prostaglandin release and the release trigger are currently unknown. During cutting, a laser spot is focused on the tissue and the vaporization generates a microplasma of gas and water. This gas arises during each laser beam and might trigger prostaglandin release.22 Involvement of alterations in temperature, soundwaves, or vibrations seems possible. Furthermore, we analyzed prostaglandin E2 levels after femtosecond laser-assisted cataract treatment. In general, levels of prostaglandin E2 were lower in aqueous humor than total prostaglandin levels. We observed significantly higher levels of prostaglandin E2 after femtosecond laser-assisted cataract treatment (Figure 2). Within the cyclooxygenase cascade, prostaglandin E2 is a major transmitter for ocular inflammation and a connection to inflammation-induced miosis seems possible.18,23,24

No correlation between the prostaglandin concentration increase and the age of the patients or the density of the lens was noted in our study (Figure A). Matsuo25 analyzed the levels of prostaglandin E2 in patients during cataract surgery and noted no correlation between prostaglandin E2 levels in aqueous humor and patient’s age. This correlates with our findings. The measured physiological levels of prostaglandin E2 in the aqueous humor of this study are similar to the levels we measured in our control group, which also underwent conventional cataract surgery. We also noted no correlation between cataract density and prostaglandin or prostaglandin E2 levels (Figure A). Furthermore, no correlation between the total suction time or total laser time and the prostaglandin or prostaglandin E2 levels was found (Figure B). Therefore, we assume that the observed increase in prostaglandin is not mechanically induced. The execution of laser corneal incisions seems to slightly raise the total prostaglandin level, but the difference between both groups was not statistically significant (Figure B). A possible explanation could be the additional overall energy applied.

Patients should possibly be pretreated with topical NSAIDs before femtosecond laser-assisted cataract surgery. NSAIDs could produce an inhibition of prostaglandin E2 in aqueous humor and therefore can be used as a pretreatment for conventional cataract surgery.26 This might also be a possible pretreatment option for femtosecond laser-assisted cataract surgery and needs to be investigated in the future. NSAID or steroidal pre-treatment might be advisable to decrease a possible risk for inflammation and hence intraoperative miosis.

This prospective study found that femtosecond laser-assisted pretreatment in cataract surgery leads to a prostaglandin level increase in the aqueous humor.

References

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(A) Correlation of individual patient’s age and prostaglandin in aqueous humor. Each dot represents one patient. The correlation coefficient was r = 0.05, indicating no significant association (P = .7). (B) Correlation of age and prostaglandin E2 levels was also not significant (r = −0.03; P = .8). (C) Scatterplot of cataract densities versus prostaglandin levels in aqueous humor. There was no correlation between prostaglandin and cataract density (r = 0.10, P = .4). (D) Plot of cataract densities versus prostaglandin E2 levels. No correlation between prostaglandin E2 and cataract density could be observed (r = 0.05; P = .7). Linear regressions are displayed as solid lines.

Figure A. (A) Correlation of individual patient’s age and prostaglandin in aqueous humor. Each dot represents one patient. The correlation coefficient was r = 0.05, indicating no significant association (P = .7). (B) Correlation of age and prostaglandin E2 levels was also not significant (r = −0.03; P = .8). (C) Scatterplot of cataract densities versus prostaglandin levels in aqueous humor. There was no correlation between prostaglandin and cataract density (r = 0.10, P = .4). (D) Plot of cataract densities versus prostaglandin E2 levels. No correlation between prostaglandin E2 and cataract density could be observed (r = 0.05; P = .7). Linear regressions are displayed as solid lines.

(A) Correlation of corneal incision procedures (manual or femtosecond laser-assisted) and prostaglandin in aqueous humor. Each dot represents one patient. No significant correlation was noted in study II (r = 0.11, P = .5). (B) Plot of corneal incision procedures versus prostaglandin E2 levels. No correlation was found between prostaglandin E2 and corneal incision in study IV (r = −0.07, P = .7). (C) Correlation of suction times in the femto group and prostaglandin levels. No significant correlation was noted in study II (r = 0.04, P = .8). (D) Scatterplot of suction times versus prostaglandin E2 levels. No correlation between prostaglandin E2 and suction time could be observed (r = −0.09, P = .6). (E) Correlation of laser times and prostaglandin levels. No correlation between prostaglandin and laser time could be observed (r = 0.04, P = .8). (F) No correlation was noted between individual laser times and prostaglandin E2 levels in study IV (r = 0.25, P = .1). Linear regressions are displayed as solid lines.

Figure B. (A) Correlation of corneal incision procedures (manual or femtosecond laser-assisted) and prostaglandin in aqueous humor. Each dot represents one patient. No significant correlation was noted in study II (r = 0.11, P = .5). (B) Plot of corneal incision procedures versus prostaglandin E2 levels. No correlation was found between prostaglandin E2 and corneal incision in study IV (r = −0.07, P = .7). (C) Correlation of suction times in the femto group and prostaglandin levels. No significant correlation was noted in study II (r = 0.04, P = .8). (D) Scatterplot of suction times versus prostaglandin E2 levels. No correlation between prostaglandin E2 and suction time could be observed (r = −0.09, P = .6). (E) Correlation of laser times and prostaglandin levels. No correlation between prostaglandin and laser time could be observed (r = 0.04, P = .8). (F) No correlation was noted between individual laser times and prostaglandin E2 levels in study IV (r = 0.25, P = .1). Linear regressions are displayed as solid lines.

Clinical Patient Data

Study No. of Patients Mean Age ± SD (y) Sex (M/F) Eye (OD/OS) Mean Cataract Stage ± SD Suction Time ± SD (sec)
I–Total Prostaglandin
  Control 22 73.9 ± 8.8 13/9 10/12 3.1 ± 1.0 NA
  Femto 22 71.5 ± 12.2 10/12 11/11 3.3 ± 0.8 176 ± 47.2
II–Total Prostaglandin
  Control 37 70.1 ± 16.1 25/12 15/22 3.1 ± 0.9 NA
  Femto 35 72.1 ± 11.0 18/17 14/21 3.3 ± 0.9 175.1 ± 40.0
III–PGE2
  Control 13 74.8 ± 12.2 4/9 8/5 3.2 ± 1.2 NA
  Femto 20 72.9 ± 8.9 10/10 9/11 3.5 ± 0.9 177.5 ± 55.3
IV–PGE2
  Control 35 72.4 ± 15.4 22/13 20/15 3.1 ± 0.8 NA
  Femto 36 72.8 ± 12.5 17/19 20/16 3.1 ± 0.8 170.2 ± 32.2

10.3928/1081597X-20131021-03

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