Highlights
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The initial expectation of a better performance with PureVision2 due to its thinner central thickness and higher oxygen transmission.
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Equivalency of these lenses in important aspects of corneal re-epithelialization and subjective comfort.
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A higher inclination rate for deposits and conjunctival hyperemia with PureVision2.
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Not only attention to Dk/t in selecting a BCL for early postoperative periods after refractive surgery.
Abstract
Purpose
To compare the efficiency and safety of two bandage contact lenses after photorefractive keratectomy (PRK).
Methods
In this double-blind study, 45 patients (90 eyes) received PRK in both eyes and wore bandage contact lenses (BCLs), PureVision (Bausch & Lomb, Rochester, NY, USA) in one eye and PureVision2 (Bausch & Lomb, Rochester, NY, USA) in the other eye, randomly assigned. The medication regimen after surgery was the same for both eyes. The epithelial defect’s size, conjunctival hyperemia and lens centration were graded objectively using slit-lamp biomicroscopy on days 1, 3 and 5 after surgery. Also ocular symptoms of discomfort including tearing, photophobia, foreign body sensation and visual fluctuations were assessed subjectively at each visit.
Results
The mean epithelial defect size on the first day after operation was similar in eyes fitted with PureVision (30.08 ± 5.30 mm²) and PureVision2 (30.25 ± 5.72 mm 2 ) lenses. (p = 0.79) Contact lens deposits and bulbar hyperaemia on days 1 and 3 after PRK were similar between the two eyes, but were significantly greater on day 5 for PureVision2 lenses. (p = 0.02; p = 0.04 respectively) There was no difference in contact lens decentration, and discomfort symptoms including pain, tearing, foreign body sensation, photophobia and visual fluctuations between the eyes fitted with PureVision and PureVision2. (p > 0.05)
Conclusions
PureVision and PureVision2 contact lenses are equivalent as bandage lenses in important aspects such as corneal re-epithelialization and subjective comfort., although PureVision2 led to a higher incidence of contact lens deposits and conjunctival hyperemia early post-PRK.
1
Introduction
Bandage contact lenses (BCLs) are widely used after corneal refractive surgery to reduce pain, promote epithelial healing, provide mechanical and structural protection, maintain corneal hydration and facilitate the visual recovery process. [ , ] The introduction of silicone hydrogel soft contact lenses improved corneal oxygenation and mitigated the complications related to hypoxia; additionally, they have been found to attenuate the patient’s discomfort compared to conventional hydrogel lenses mostly due to faster re-epithelialization after refractive surgery. [ , ] There are a wide variety of silicone hydrogels commercially available [ ]. The key features considered to select the optimum BCL include its oxygen permeability, water content, wetting agents, diameter, base curve and modulus [ ].
Several studies have investigated the effect of different materials on the epithelial healing, visual outcomes and subjective assessment of pain and discomfort after corneal refractive surgery; [ ] however, they could not determine which specific parameters influence the contact lens’s performance or its role during the healing process. PureVision and PureVision2 silicone hydrogel (SiH) contact lenses are made of the Balafilcon A that contains 36 % water and AerGel™ technology lens material that are manufactured by cast molding process. Surface treatment is performed using the Performa™ process which transforms hydrophobic silicone to hydrophilic silicate. These two lenses are similar except for center thickness and hence Dk/t [ , , ]. Therefore, this study allows the effect of two BCLs, PureVision and PureVision2, on wound healing, conjunctival hyperemia, subjective symptoms and contact lens deposits following PRK to be investigated with minimal effects from other confounding factors such as lens design and other material properties in this study.
2
Patients and methods
In this prospective double-masked, contralateral, comparative clinical study, participants were 45 myopic patients (90 eyes) undergoing bilateral PRK who met the inclusion criteria. Of these patients, 37 (82 %) were women. The mean age was 29.4 ± 6.5 years with a range 19–45 years. The aims of this project were clearly clarified to the patients in advance, and an informed consent was signed by all participants. All steps of this study were conducted under the provision of the tenets of the Declaration of Helsinki and the study was approved by the local ethics committee.
The inclusion criteria were myopia less than or equal to 8.00 diopters (D) and astigmatism ≤2.00 D, age at least 18 years old, normal corneal topo/tomography, stability of refraction of at least 1 years < ±0.25D in spherical equivalent (SE), spectacle distance corrected visual acuity (SDCVA) of at least 20/20, no ocular and systemic diseases and not pregnant or breast feeding.
A complete ophthalmic examination including distance uncorrected visual acuity (DUCVA) and spectacle distance corrected visual acuity (SDCVA), manifest and cycloplegic refraction using cyclopentolate hydrochloride 1%, slit lamp biomicroscopy examination, corneal topography using Placido-disk based topography (Tomey Corp, Nagoya, Japan), corneal tomography using Orbscan (Orbscan IIz, Bausch & Lomb, Rochester, NY, USA), Hartmann-Shack aberrometry (Zywave aberrometer, Bausch & Lomb, Rochester, NY, USA) and fundus examination after pupil dilation was conducted for each patient.
2.1
Surgical technique
All PRK procedures were performed by one surgeon (S.Z) and both eyes of each patient were treated consecutively. Initially, a topical anesthetic (Tetracaine 0.5 %) was applied 3 times. Subsequently, 20 % ethanol through an 8 mm semi-sharp corneal marker was applied for 20 s to soften the corneal epithelium. A weck cell sponge was used to remove the alcohol and the cornea was rinsed with 40 ml of a balanced salt solution (BSS). Corneal epithelium was removed by weck sponge. Stromal ablation was performed using Technolas 217-Z100 excimer laser (Bausch & Lomb, Rochester, NY, USA), and was followed by application of Mitomycin-C 0.02 % for 5 s per each diopter of SE treatment and irrigation using 40cc of BSS. At the end of procedure, one eye of each patient was fitted with PureVision (PureVision™ Bausch & Lomb, Rochester, NY, USA) and the other eye with PureVision 2 (PureVision2™ Bausch & Lomb, Rochester, NY, USA) bandage contact lens, assigned randomly. Slit-lamp biomicroscopy evaluation at the end of surgery showed an appropriate fit of BCL in all eyes. The characteristics of these lenses are shown in Table 1 .
| Variables | PureVision | PureVision2 |
|---|---|---|
| Material | Balafilcon A | Balafilcon A |
| Surface treatment | Plasma oxidation | Plasma oxidation |
| Optics technology | Aspheric optics | Aspheric optics |
| Dk (10 −11 ) | 91 | 91 |
| Central thickness@-3.00 (mm) | 0.09 | 0.07 |
| DK/t (10 −9 , -3.00D) | 101 | 130 |
| Water content (%) | 36 | 36 |
| Diameter (mm) | 14.0 | 14.0 |
| Base curve (mm) | 8.6 | 8.6 |
| Optic zone for -3.00 D (mm) | 8.9 | 9.0 |
| Wetting agent | None | None |
| Modulus (MPa) | 1.1 | 1.1 |
| UV blocking | No | No |
Patients and surgeon were masked to the type of BCL fitted in each eye. The same surgeon evaluated the BCL’s fitting using slit lamp biomicroscopy. The mean and standard deviation (SD) of preoperative refractive status, keratometry reading and central corneal thickness in the eyes fitted with the two BCLs which are shown in Table 2 did not show significant difference. ( Table 2 )
| Variables | PureVision (n=45 eyes) | PureVision2 (n=45 eyes) | p-value |
|---|---|---|---|
| Mean ± SD (Range) | Mean ± SD (Range) | ||
| Sphere (D) | −2.92 ± −1.46 (0.00 to −6.5) | −2.82 ± −1.55 (0.00 to -6.5) | 0.17 |
| Cylinder (D) | −0.59 ± −0.69 (0.00 to −2.75) | −0.72 ± −0.75 (0.00 to -3.00) | 0.07 |
| Spherical equivalent (D) | −3.18 ± −1.42 (−0.75 to −6.75) | −3.21 ± −1.44 (-0.5 to -6.75) | 0.68 |
| Mean Keratometry (D) | 44.06 ± 1.22 (41.64 to 46.36) | 44.10 ± 1.20 (41.65 to 46.28) | 0.20 |
| Corneal thickness (μm) | 545.6 ± 37.32 (472–612) | 547.64 ± 38.84 (478–621) | 0.09 |
2.2
Medications and postoperative follow-ups
The postoperative medication regimen was the same for both eyes and included topical diclofenac sodium 0.1 % (Allergan, Dublin, Ireland) administrated 6 times daily for 2 days, levofloxacin (Oftaquix, Santen Pharmaceutical, Osaka, Japan) drops 5 mg/ml 6 times daily until complete corneal re-epithelialization, and betamethasone (Betasonate, Sina Daru, Iran) eye drop used for 1 month, and then replaced with fluorometholone 0.1 % (Allergan Ltd, Dublin, Ireland) eye drop every 6 h in a tapering schedule for 2 months. Preservative-free artificial tears (Artelac Advanced, Bausch & Lomb, Rochester, NY, USA) were administrated frequently in the first month until complete re-epithelialization and then gradually tapered with attention to the ocular surface condition.
All patients were followed up at 1, 3 and 5 days postoperatively by the same surgeon. Postoperative assessments were digital slit-lamp biomicroscopy (BQ 900, Haag-Streit, Koniz, Switzerland) to evaluate the integrity of corneal epithelium, corneal infiltration, conjunctival hyperemia, lens decenteration and contact lens deposit.
The epithelial defect size was calculated based on the remaining area (A) of epithelial defects using the following equation [ ]:
where “a” and “b” refer to the shortest and longest dimension of epithelial defect, respectively.
For each patient, the BCL was removed when there was no observable epithelial defect and the day of epithelial healing was recorded in each case.
Contact lens deposition was graded based on a five point scale, [ ] and lens decenteration and conjunctival hyperemia using a four point scale [ ]. ( Tables 3 and 4 )
| Grade | Contact lens deposit |
|---|---|
| 0 | No deposit |
| 1 | Up to 25 % of the lens surface |
| 2 | Up to 50 % of the lens surface |
| 3 | UP to 75 % of the lens surface |
| 4 | Over than 75 % of the lens surface |
| Grade | Lens decenteration | Conjunctival hyperemia |
|---|---|---|
| 0 | Centered lens or decentration, less than 1mm | Very slight |
| 1 | Decentration between 1-2mm | Slight |
| 2 | Decenteration between 2-3mm | Moderate |
| 3 | Decenteration more than 3mm | Sever |
Also, all patients completed a subjective questionnaire grading pain, tearing, foreign body sensation, photophobia and visual fluctuations on a five point score (0–4) on the first, third and fifth days after surgery [ ].
2.3
Statistical analysis
The data was analyzed in SPSS-21 software using the paired-sample t -test or a non-parametric test (Wilcoxon signed rank test) based upon whether the data displayed a normal distribution or not (Kolmogorov–Smirnov test <0.05). A p-value less than 0.05 was considered significant statistically.
3
Results
The mean size of epithelial defect in the eyes fitted with PureVision and PureVision2 on the first day after surgery was 30.08 ± 5.30 mm² (range: 20.82–44.16 mm²) and 30.25 ± 5.72 mm 2 (range: 6.97–45.94 mm²), respectively with no statistically significant difference between the two contact lenses. (p = 0.79) The defect size on the third post-operative day was 0.08 ± 0.29 mm² (range: 0.0–1.77 mm²) with PureVision and 0.14 ± 0.55 mm² (range: 0.0–3.14 mm²) with PureVision2. (p = 0.47) After five days, re-epithelialization was completed and BCLs were removed from all eyes except in one eye (fitted with PureVision2) that healed seven days after surgery. However, there was no statistically difference in corneal epithelial healing between the two lenses at all visits.
The difference between the mean conjunctival hyperemia between the two lenses was not statistically significant on days 1 (p = 0.37) and 3 (p = 0.53); however, conjunctival hyperemia on day 5 was significantly higher in the eyes fitted with PureVision2 than those with PureVision. (p = 0.04). ( Fig. 1 )
