Ophthalmic Surgery, Lasers and Imaging Retina

Clinical Science 

Comparative Study of Corneal Wetting Agents During 25-Gauge Microincision Vitrectomy Surgery Under a Noncontact Wide-Angle Viewing System

Soo Hyun Kwon, MD; Jae Pil Shin, MD; In Taek Kim, MD; Dong Ho Park, MD

Abstract

BACKGROUND AND OBJECTIVE:

To compare the effects of corneal wetting agents during 25-gauge microincision vitrectomy surgery (MIVS) under a binocular indirect ophthalmic microscope system.

MATERIALS AND METHODS:

This prospective, randomized, comparative study included 45 eyes undergoing 25-gauge MIVS. The randomly assigned corneal wetting agents were balanced salt solution, ProVisc, and DisCoVisc. The main outcome measures were the frequency of applications, the duration of each application, and the corneal surface status including corneal fluorescein staining score postoperatively.

RESULTS:

The mean frequency of applications was higher for balanced salt solution (13.6 ± 4.3) than ProVisc (2.7 ± 1.0) or DisCoVisc (1.7 ± 0.5) (P < .001). The duration of each application was longer for DisCoVisc (29.8 ± 6.0 minutes) than balanced salt solution (3.7 ± 1.1 minutes) or ProVisc (17.6 ± 3.6 minutes) (P < .001). The fluorescein staining score was higher for balanced salt solution until 7 days postoperatively (P < .001).

CONCLUSION:

ProVisc and DisCoVisc could be more effective corneal wetting agents than balanced salt solution by minimizing the frequency of intraoperative application and postoperative corneal injury.

[Ophthalmic Surg Lasers Imaging Retina. 2013;44:360–365.]

From the Department of Ophthalmology, School of Medicine, Kyungpook National University, Daegu, Korea.

Supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2012004585) and by the Korea Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (A111345).

The authors have no financial or proprietary interest in the materials presented herein.

Address correspondence to Dong Ho Park, MD, Department of Ophthalmology, School of Medicine, Kyungpook National University, #50 Samduk-dong-2-ga, Jung-gu, Daegu, 700-721, Korea; 82-53-420-5813; fax: 82-53-426-6552; email: sarasate2222@gmail.com.

Received: March 04, 2013
Accepted: May 01, 2013

Abstract

BACKGROUND AND OBJECTIVE:

To compare the effects of corneal wetting agents during 25-gauge microincision vitrectomy surgery (MIVS) under a binocular indirect ophthalmic microscope system.

MATERIALS AND METHODS:

This prospective, randomized, comparative study included 45 eyes undergoing 25-gauge MIVS. The randomly assigned corneal wetting agents were balanced salt solution, ProVisc, and DisCoVisc. The main outcome measures were the frequency of applications, the duration of each application, and the corneal surface status including corneal fluorescein staining score postoperatively.

RESULTS:

The mean frequency of applications was higher for balanced salt solution (13.6 ± 4.3) than ProVisc (2.7 ± 1.0) or DisCoVisc (1.7 ± 0.5) (P < .001). The duration of each application was longer for DisCoVisc (29.8 ± 6.0 minutes) than balanced salt solution (3.7 ± 1.1 minutes) or ProVisc (17.6 ± 3.6 minutes) (P < .001). The fluorescein staining score was higher for balanced salt solution until 7 days postoperatively (P < .001).

CONCLUSION:

ProVisc and DisCoVisc could be more effective corneal wetting agents than balanced salt solution by minimizing the frequency of intraoperative application and postoperative corneal injury.

[Ophthalmic Surg Lasers Imaging Retina. 2013;44:360–365.]

From the Department of Ophthalmology, School of Medicine, Kyungpook National University, Daegu, Korea.

Supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2012004585) and by the Korea Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (A111345).

The authors have no financial or proprietary interest in the materials presented herein.

Address correspondence to Dong Ho Park, MD, Department of Ophthalmology, School of Medicine, Kyungpook National University, #50 Samduk-dong-2-ga, Jung-gu, Daegu, 700-721, Korea; 82-53-420-5813; fax: 82-53-426-6552; email: sarasate2222@gmail.com.

Received: March 04, 2013
Accepted: May 01, 2013

Introduction

A noncontact wide-angle binocular indirect ophthalmoscope (BIOM)1 has many advantages over a contact wide-angle system, including not requiring an assistant and easily maintaining a good image during eye movement.

Microincision vitrectomy surgery (MIVS) has recently been employed as a more beneficial and less traumatic surgical procedure than conventional 20-gauge vitrectomy.2–4 Since MIVS has become more prevalent, noncontact wide-angle viewing systems have become more popular.

Frequent irrigation of the corneal surfaces with corneal wetting agents such as balanced salt solution is necessary to maintain a clear view of the surgical manipulations during vitrectomy. However, repeated irrigation of the corneal surface, which takes a longer time during vitrectomy than phacoemulsification, may disrupt the clear microscopic view and the surgeon’s concentration. Furthermore, as the frequency of repeated irrigations increases, the possibility of damaging the corneal surface also increases.

Ophthalmic viscoelastic devices (OVDs) play an important role in modern cataract surgery. In addition, because OVDs including sodium hyaluronate and chondroitin sulfate provide a relatively long duration of corneal wetting, they have been used as topical corneal wetting agents in patients with dry eye syndrome.5,6

Similarly, the corneal wetting properties of OVDs could prevent the need for frequent irrigation of the corneal surface during 25-gauge MIVS under a BIOM system. To our knowledge, a comparison of corneal wetting agents during vitrectomy and postoperative changes in the surface of the cornea after vitrectomy has not been reported before. The purpose of this study was to investigate whether there was a difference among balanced salt solution and other OVDs as corneal wetting agents during 25-gauge MIVS under BIOM in terms of surgical effectiveness and postoperative corneal injury.

Patients and Methods

Subjects

A prospective, comparative study was conducted with 45 consecutive patients (45 eyes) who underwent 25-gauge MIVS with a BIOM system in the ophthalmology department at Kyungpook National University Hospital in Daegu, Korea, from September 2011 to April 2012. The study was conducted in accordance with the Declaration of Helsinki, and the study protocol was approved by the institutional review board of Kyungpook National University Hospital. Informed consent was obtained from all patients.

The indications for vitreoretinal surgery were idiopathic epiretinal membrane, idiopathic macular hole, vitreous hemorrhage due to retinal vein occlusion, proliferative diabetic retinopathy, and pseudophakic rhegmatogenous retinal detachment.

The exclusion criteria were dry eye syndrome including scratchy sensation and tear film breakup time (TFBUT) of no more than 5 seconds or Schirmer 1 test score of no more than 5 mm in 5 minutes;7 ocular diseases such as severe blepharitis, allergic conjunctivitis, or keratitis; age older than 60 years; severe cataract requiring combined phacoemulsification; previous cataract surgery within 1 year; and previous excimer laser refractive procedures.

Patients were assigned to either balanced salt solution (BSS), ProVisc, or DisCoVisc (all Alcon Laboratories, Fort Worth, TX) according to a sequence generated using randomly permuted blocks and a randomization table. After the computerized randomization procedure, the masked trial statistician generated sequentially numbered opaque, sealed envelopes. The allocation envelopes remained concealed until the interventions were assigned. Once a participant consented to the study, a masked research trial coordinator opened the sealed envelope and assigned participants to each group.

Ophthalmic Examinations

All patients had ophthalmic examinations including Snellen best corrected visual acuity (BCVA) and dilated fundus examination with slit-lamp biomicroscopy at baseline. Snellen visual acuity was converted to the logarithm of the minimum angle of resolution (logMAR). In addition, principal outcome measures including corneal fluorescein staining score (FSS) and fluorescein TFBUT were evaluated.

Corneal FSS was measured using the grading system recommended by the National Eye Institute/Industry Workshop on Clinical Trials in Dry Eyes.8 The cornea is divided into five areas (Figure 1), and each is graded on a scale of 0 to 3 according to the intensity of the fluorescein staining.

Map of the National Eye Institute corneal grading system. The cornea is divided into five areas graded on a scale of 0 to 3. The maximum possible staining score is 15.

Figure 1. Map of the National Eye Institute corneal grading system. The cornea is divided into five areas graded on a scale of 0 to 3. The maximum possible staining score is 15.

A fluorescein sodium strip moistened with a drop of sterile normal saline was applied to the inferior palpebral conjunctiva. Patients were asked to open and close their eyes and roll them around to distribute the dye in the tear film. Patients were then asked to blink and then open their eyes and refrain from blinking. The precorneal tear film was examined with a biomicroscope with a 10× objective, and the elapsed time before the initial breakup or rupture of the tear film or formation of dry spots was recorded. The test was conducted three times for each eye, and the results were averaged.

The ophthalmic examinations were performed at baseline, 6 hours, and 1, 3, 7, 14, and 30 days postoperatively by a single ophthalmologist (SHK) masked to the patients’ assigned groups.

Surgical Procedure

All surgeries were performed by one surgeon (DHP) using the 25-gauge trocar system under peribulbar anesthesia. A BIOM III (Oculus, Wetzlar, Germany) viewing system was used to enable posterior visualization. The surgical approach began with displacing the conjunctiva immediately above the designated sclerotomy site to disallow communication between the two entry sites. Next, a transconjunctival cannula was inserted diagonally through the sclera, 3.5 mm from the limbus, using a beveled trocar to create a conjunctival-scleral incision measuring 0.5 mm in diameter. After three cannulas were placed, applications of the corneal wetting agents were performed by an assistant. The 25-gauge MIVS procedures were performed using the Accurus Vitrectomy System (Alcon, Fort Worth, TX), which included core vitrectomy, epiretinal membrane peeling, or fibrovascular membrane dissection.

When a microscopic view was obscured by desiccation of the corneal surface, applications of the corneal wetting agents were repeated, and the assistant counted the frequency of the wetting agent applications. The frequency and duration measurements were not masked because they were based on the subjective blurring of the surgical image.

The postoperative regimen included topical 0.3% levofloxacin, 1% prednisolone acetate, and artificial tear eye drops four times per day over 4 weeks.

Sample Size and Statistical Analysis

The final sample size was calculated after an interim analysis of the first 10 eyes in each group. An alpha error level of 0.05 and a power level of 0.8 were defined. Differences in the mean and standard deviation of the duration of efficacy for the applications among the three groups suggested a sample size of 15 eyes per group. Means ± standard deviation were used to describe quantitative data, and percentages were used to describe qualitative data. The chi-square test was used to compare the qualitative data. Overall intergroup differences were first compared using the Kruskal-Wallis test. Post hoc pairwise comparisons using the Bonferroni correction were performed if significant overall intergroup differences were found. The Kruskal-Wallis test was performed to compare the mean FSS and TFBUT at each postoperative period between the BSS, ProVisc, and DisCoVisc groups. The model was adjusted for age, operative time, and presence of diabetes. Repeated measures analysis of variance (ANOVA) corrected by Bonferroni’s method were used to compare the mean FSS values for each postoperative period in the same group. Statistical analyses were conducted using SPSS statistical software. For all statistical tests, a P value of less than 0.05 was considered significant.

Results

Baseline Characteristics

Forty five patients (45 eyes) enrolled in this study. The mean age was 55.6 ± 5.4 years (range: 40 to 59 years). Demographics and clinical data of the patients are summarized in Table 1. Among the 45 patients, 15 patients (15 eyes) each received one of three corneal wetting agents, BSS, ProVisc, or DisCoVisc. There were no significant differences among the three groups in age, gender, diabetes status, lens status, indication of vitrectomy, and BCVA at first visit.

Demographics and Clinical Characteristics

Table 1: Demographics and Clinical Characteristics

Application Frequency, Efficacy Duration

There was no difference in operative time among the three groups (Table 2). The frequency for the BSS group was significantly higher than that of the Pro-Visc and DisCoVisc groups (P < .001, respectively). The duration of effect for the DisCoVisc group was longer than that of the BSS and ProVisc groups (P < .001, respectively).

Comparison of Wetting Solution Efficacy During 25-gauge Microincision Vitrectomy Surgery

Table 2: Comparison of Wetting Solution Efficacy During 25-gauge Microincision Vitrectomy Surgery

Fluorescein Staining Score

There was no difference in the baseline FSS among the three groups (Table 3). However, there was a significant difference in the FSS at 6 hours and 1, 3, 7, and 14 days postoperatively (P < .001, P < .001, P < .001, P < .001, and P = .004, respectively) (Figure 2). The FSS of the BSS group was higher than that of the ProVisc and DisCoVisc groups at 6 hours and 1, 3 (P < .001 and P < .001, respectively), and 7 days (P = .002 and P < .001, respectively) postoperatively. The FSS of the BSS group increased from baseline at 6 hours and 1, 3, 7, and 14 days postoperatively (P < .001, P < .001, P < .001, P < .001, and P = .001, respectively) (Table 3). The FSS of the Pro-Visc group increased at 6 hours and 1, 3, and 7 days postoperatively (P < .001, respectively). The FSS of the DisCoVisc group increased at 6 hours, and 1 and 3 days postoperatively (P = .001, respectively).

Postoperative Changes in Corneal Fluorescein Staining Score Among the Balanced Salt Solution, ProVisc, and DisCoVisc Groups

Table 3: Postoperative Changes in Corneal Fluorescein Staining Score Among the Balanced Salt Solution, ProVisc, and DisCoVisc Groups

Postoperative changes in corneal fluorescein staining score (FSS) among the BSS, ProVisc, and DisCoVisc groups. There was a significant difference in the FSS at 6 hours and 1, 3, 7, and 14 days postoperatively.

Figure 2. Postoperative changes in corneal fluorescein staining score (FSS) among the BSS, ProVisc, and DisCoVisc groups. There was a significant difference in the FSS at 6 hours and 1, 3, 7, and 14 days postoperatively.

Tear Film Breakup Time

There was no difference in the TFBUT at baseline among the three groups (Figure 3). In addition, there was no difference in the TFBUT among the three groups postoperatively (P > .05).

Postoperative changes in tear film breakup time (TFBUT) among the BSS, ProVisc, and Dis-CoVisc groups. There was no intergroup difference in TFBUT at baseline and each postoperative period.

Figure 3. Postoperative changes in tear film breakup time (TFBUT) among the BSS, ProVisc, and Dis-CoVisc groups. There was no intergroup difference in TFBUT at baseline and each postoperative period.

Correlating Age, Operative Time With FSS, TFBUT

Spearman correlation showed that there was no correlation between age and operative time, and FSS at baseline and at each postoperative period (P > .05, respectively). Furthermore, there was no correlation between age and operative time, and TFBUT at baseline and at each postoperative period (P > .05, respectively).

Intraoperative and Postoperative Complications

There were no eyes requiring sutures due to leakage at the sclerotomy sites. There were no eyes with postoperative complications related to MIVS, which included postoperative hypotony, postoperative vitreous hemorrhage, recurrent ERM, and endophthalmitis during the first month postoperatively.

Discussion

DisCoVisc (hyaluronic acid 1.6%-chondroitin sulfate 4%) is a new-generation OVD that has both cohesive and dispersive OVD properties. The cohesive and dispersive OVD properties maintain adequate space and protect the corneal endothelium during cataract surgery.9

Several studies compared the corneal wetting properties of BSS and lubricants including HsS (elastoviscous hylan surgical shield, 0.45%),10 hydroxypropyl methylcellulose 2% gel,11 and lidocaine 2% jelly12 during phacoemulsification. The mean number of BSS applications was about 10 times more than that of the other coating agents, even during short time periods of phacoemulsification. The current study compared the frequency and duration of the effect of corneal wetting agents that included BSS, ProVisc, and DisCoVisc during 25-gauge MIVS under BIOM. The frequency of applications of BSS was significantly higher than ProVisc and DisCoVisc groups.

A previous study investigated the residual amounts of OVDs on the corneal endothelium following phacoemulsification in animal models.13 While ProVisc disappeared completely from the anterior chamber, DisCoVisc remained on the entire corneal endothelium in a uniform thickness.13 In the current study, the duration of effect was longer for DisCoVisc than BSS or ProVisc. Furthermore, DisCoVisc, which has an intermediate cohesive/dispersive index, has retention and removal properties. For this reason, DisCoVisc has a similar time for complete removal from the anterior chamber compared to ProVisc, the cohesive OVD.14

A previous comparison study between BSS and hydroxypropyl methylcellulose demonstrated no difference in FSS.11 However, the mean duration of phacoemulsification for the study population was 13.5 minutes. The current study evaluated changes in the corneal surface after vitrectomy, which took longer than 45 minutes on average in all groups. The FSS of the BSS group was higher than that of the ProVisc and DisCoVisc groups at 6 hours and 1, 3 and, 7 days postoperatively. The OVDs have been used as topical corneal wetting agents in patients with dry eye syndrome including sodium hyaluronate and chondroitin sulfate, which provide a relatively long duration of corneal wetting.5,6 The protective effect of OVDs from the microscope light or flow of air in the operating room could cause less corneal injury compared to BSS.

Furthermore, a recent study showed that corneal fluorescein staining indicating superficial punctate keratopathy (SPK) correlated with visual function in dry eye patients.15 Dry eye with SPK showed significant deterioration in visual function and optical quality compared with dry eye without SPK and normal eyes. The present study included patients with various retinal diseases including a macular hole or rhegmatogenous retinal detachment that required C3F8 flushing at the end of vitrectomy. Thus, the study could not compare the BCVA which could be affected by FSS. However, the above results could suggest that patients with a higher FSS are likely to have lower visual function and optical quality.

Another study reported that the longer the operative time, the greater the inflammatory response, which could damage and reduce the goblet cells.16 However, in the current study, the FSS and TFBUT results were adjusted for the operative time and there was no correlation with the operative time and the FSS and TFBUT. This could suggest that the operative time is not a main factor that changes the ocular surface postoperatively. Although 25-gauge MIVS could cause some minimal conjunctival trauma, it may not significantly damage the ocular surface including the goblet cells.

The current study has several limitations including no evaluation of subjective symptoms, visual function, and histological changes in the ocular surface. Although the number of diabetic eyes was the same in all of the three groups, these eyes had an inherent problem of loose corneal epithelium. Furthermore, because of the small number of cases, this study could not compare the results of patients with and without diabetes. However, the authors excluded patients with dry eye syndrome or any corneal surface diseases. In addition, the results were adjusted for age, operative time, and the presence of diabetes to exclude possible confounding factors. Because a sterilized 2% hydroxypropylmethylcellulose (HPMC) suitable for the surgery is not available in Korea, we used BSS as a control group and could not compare the results with HPMC.

In conclusion, the present study compared the effect of corneal wetting agents during 25-gauge MIVS under a noncontact wide-angle viewing system. Pro-Visc and DisCoVisc could be more effective corneal wetting agents than BSS by minimizing the frequency of intraoperative corneal irrigation, thus minimizing the disruption of the clear microscopic view and concentration of the surgeon during vitrectomy. Furthermore, ProVisc and DisCoVisc cause less postoperative corneal injury, which would be more beneficial to patients who have dry eye syndrome or corneal surface diseases.

References

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Demographics and Clinical Characteristics

BSSProViscDisCoViscP Value
No. of eyes (patients)15 (15)15 (15)15 (15)
Gender ratio (male: female)8:75:106:9.529*
Age (mean ± SD)55.0 ± 6.656.7 ± 4.855.1 ± 4.8.716 **
DM, n (%)5 (33.3)5 (33.3)7 (46.7).685*
Lens status ratio
  Phakic to pseudophakic12:311:413:2.710 *
Vitrectomy indication, n (%).988 *
  ERM4 (26.7)5 (33.3)5 (33.3)
  Macular hole2 (13.3)2 (13.3)1 (6.7)
  VH due to RVO3 (20.0)2 (13.3)2 (13.3)
  PDR5 (33.3)4 (26.7)6 (40.0)
  Pseudophakic RRD1 (6.7)2 (13.3)1 (6.7)
BCVA at first visit (logMAR)1.49 ± 1.211.47 ± 1.141.42 ± 1.18.966**

Comparison of Wetting Solution Efficacy During 25-gauge Microincision Vitrectomy Surgery

BSSProViscDisCoViscP Value*
Operative time (minutes)47.4 ± 9.845.9 ± 17.950.9 ± 15.8.605
Frequency of applications13.6 ± 4.32.7 ± 1.01.7 ± 0.5< .001
Duration of effect (minutes)3.7 ± 1.117.6 ± 3.629.8 ± 6.0< .001

Postoperative Changes in Corneal Fluorescein Staining Score Among the Balanced Salt Solution, ProVisc, and DisCoVisc Groups

BSSProViscDisCoViscP Value*
FSSP Value**FSSP Value**FSSP Value**
Baseline0.1 ± 0.40.2 ± 0.40.2 ± 0.4.862
Postop
6 hrs6.9 ± 2.0< .0012.6 ± 1.2< .0011.4 ± 1.0.001< .001
1 D5.0 ± 2.1< .0012.1 ± 1.1< .0011.1 ± 0.8.001< .001
3 D3.1 ± 1.6< .0011.5 ± 0.9< .0010.9 ± 0.6.001< .001
7 D2.2 ± 1.3< .0011.1 ± 0.6< .0010.5 ± 0.5.055< .001
14 D1.3 ± 0.9.0010.7 ± 0.6.0680.3 ± 0.5.433.004
30 D0.5 ± 0.5.0590.4 ± 0.5.4990.1 ± 0.4.670.146

10.3928/23258160-20130715-07

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