|Year : 2019 | Volume
| Issue : 1 | Page : 77-81
Combined wavefront guided on the flap photorefractive keratectomy with accelerated collagen cross-linking for postlaser In situ keratomileusis ectasia: A novel technique
GV Prabhakar1, JK Reddy2, KS Siddharthan2, Anushree Agrawal2
1 Department of Cornea, Sankara Eye Hospital, Coimbatore, Tamil Nadu, India
2 Department of Refractive Surgery, Sankara Eye Hospital, Coimbatore, Tamil Nadu, India
|Date of Web Publication||10-Jun-2019|
Dr. G V Prabhakar
Department of Cornea, Sankara Eye Hospital, Sathy Road, Coimbatore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Purpose: To report a series of patients who underwent simultaneous wavefront guided photorefractive keratectomy (PRK) followed by corneal collagen cross-linking (CXL) for post lasik ectasia. Methods: Two patients with corneal ectasia who underwent wavefront guided (iDesign Advanced Wave Scan Studio) PRK (STAR S4 IR ) immediately followed by CXL (AVEDRO) were included. Patient's Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, keratometry, pachymetry, corneal topography (Oculus Pentacam), were analyzed till 36 months of follow up. Results: 2 eyes had an improvement to UDVA of 20/20 at last follow-up. At 3 years follow up all the 2 eyes are topographically and visually stable maintaining 20/20. Conclusion: Simultaneous wavefront-guided PRK and CXL is effective and safe in achieving both visual quality improvement and topographic stability which is maintained in long term .This technique may offer an alternative and effective method to treat iatrogenic corneal ectasia.
Keywords: Combined photorefractive keratectomy with corneal cross-linking, cross-linking, ectasia, iatrogenic ectasia, laser in situ keratomileusis, photorefractive keratectomy, postlaser in situ keratomileusis ectasia
|How to cite this article:|
Prabhakar G V, Reddy J K, Siddharthan K S, Agrawal A. Combined wavefront guided on the flap photorefractive keratectomy with accelerated collagen cross-linking for postlaser In situ keratomileusis ectasia: A novel technique. TNOA J Ophthalmic Sci Res 2019;57:77-81
|How to cite this URL:|
Prabhakar G V, Reddy J K, Siddharthan K S, Agrawal A. Combined wavefront guided on the flap photorefractive keratectomy with accelerated collagen cross-linking for postlaser In situ keratomileusis ectasia: A novel technique. TNOA J Ophthalmic Sci Res [serial online] 2019 [cited 2019 Nov 11];57:77-81. Available from: http://www.tnoajosr.com/text.asp?2019/57/1/77/259870
| Introduction|| |
Corneal ectasia is the condition in which there is a loss of corrected distance visual acuity, myopia, and irregular astigmatism secondary to progressive corneal thinning and steepening. Corneal ectasia following laser in situ keratomileusis (LASIK) was first described by Seiler et al., and it is a sight-threatening complication with a prevalence rate of 1/2500.
After analyzing a series of eyes developing post-LASIK ectasia, certain parameters such as high myopic corrections, thin corneas, and residual corneal bed thickness <250 μm act as red flags for this condition.,, Corneal ectasia sometimes can be unpredictable as it can occur in the absence of these risk factors too.
Treatment of post-LASIK ectasia is aimed at refractive error correction and stabilizing progression of ectasia. Refractive error is corrected with spectacles, rigid gas permeable lenses, and intrastromal corneal ring segments. If these methods fail, Lamellar or penetrating keratoplasty is considered.
Arresting the progression of ectasia is achieved by corneal cross-linking (CXL) which acts by inducing additional cross-links between collagen fibers., However, it does not have any significant role in visual recovery.,
CXL with photorefractive keratectomy (PRK) and phototherapeutic keratectomy has offered combined effect in halting the progression of ectasia and providing visual improvement at the same time. To the best of our knowledge, there are only few studies on simultaneous PRK-CXL applied for post-LASIK ectasia which are associated with good results, where both the studies used topography-guided PRK., Because there has been little literature on combined CXL with topography-guided PRK and no literature on wavefront-guided PRK for post-LASIK ectasia, we would like to add our experience to the same.
In our case series, we describe two cases of post-LASIK ectasia treated with wavefront-guided PRK with CXL and its effect at 3 years. This study was approved by the institutional ethical review board, and the study was carried out in accordance with the provisions of the World Medical Association Declaration of Helsinki.
PRK was performed before the CXL treatment. The surgical procedure was conducted under sterile conditions. The patient's eye was anesthetized with proparacaine 0.5%. The epithelium was removed with spatula. A customized ablation on top of the LASIK flap was given. Mitomycin C 0.02% solution was applied over the ablated tissue for 20 s followed by irrigation with 10 mL of balanced salt solution. Refractive error correction was based on wavefront calculated by aberrometer device (I DESIGN).
CXL – For the next 10 min, the proprietary 0.1% riboflavin sodium phosphate was applied topically for every 2 min. Followed by UVA light of mean 370-nm wavelength and 14 mW/cm2, radiance was projected onto the surface of the cornea for 7 min (Avedro cxl) with a fluence of 5.4 J/cm2 and bandage contact lens was placed. Postoperatively, topical moxifloxacin (0.5%) and dexamethasone (0.1%) was used qid and tapered over 1 month.
| Case Reports|| |
Case report 1
A 23-year-old male had undergone LASIK in September 2011 at another institution. Pre-LASIK uncorrected distance visual acuity (UDVA) was 6/24 in both eyes as per the records. Manifest refraction was −0.75 DS, −1.50 DC at 120° (6/6) in the right eye and −0.75 DS, −2.00 DC at 60° (6/6) in the left eye. Preoperative keratometry and corneal thickness readings were not available. No surgical data were available. The patient achieved UDVA of 6/6 in both eyes. In October 2012, he complained of progressively decreasing vision in the left eye with UDVA of 6/18 in the left eye and 6/6 in the right eye.
The patient was followed up in March 2013, 26 months after LASIK, with a manifest refraction of −0.50 DS, −1.25 DC at 70° (20/20) in the left eye. Keratometry was 38.75 D at 90°/35.62 D at 180° in the left eye and 40.65 D at 05°/39.55 D at 95° in the right eye. Endothelial cell count was 2860 cells/mm2. Central corneal thickness (measured with Pentacam) was 495 μm with thinnest pachymetry of 490 μ in the right eye and 505 μm in the left eye with thinnest pachymetry of 480 μ. A diagnosis of left eye corneal ectasia was made. Flap thickness was 100 μ.
Combined wavefront-guided PRK/CXL technique was performed on the left eye in April 2013, 32 months after LASIK.
In February 2017, 48 months after wavefront-guided PRK/CXL, UDVA improved to 20/20 in the left eye [Figure 1]. Keratometry was 37.50 at 85°/36.62 at 175° in the right eye and 37.75 at 79°/37.87 at 169° in the left eye. Pentacam pachymetry was 414 μm with flap thickness of 85 μ in the left eye. Endothelial cell count was 2854 cells/mm2.
|Figure 1: Demonstrates the pre- and postoperative topographies with stability|
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Case report 2
A 27-year-old female had undergone LASIK in September 2012 at our institution. Pre-LASIK UDVA was 4/60 in both eyes and manifest refraction was − 5.5 D improving to 6/6. Preoperative keratometry was 42.54 at 153°/43.04 at 63° in the RE, 42.52 at 152°/43.16 at 62° at the left eye. Central corneal thickness (Pentacam) was 510 μ and 520 μ. The patient achieved UDVA of 6/6 in each eye. In October 2013, she complained of progressively decreasing vision in the left eye (6/18). The patient was followed up in March 2014, 26 months after LASIK, with a manifest refraction of 0.00 (6/6) in the right eye and 1.25 DS, –2.79 DC at 115° (20/20) in the left eye. Central corneal thickness was 465 μm in the right eye and 456 μm in the left eye and thinnest pachymetry was 460 μ and 440 μ [Figure 2] and [Figure 3], respectively. A diagnosis of left eye corneal ectasia was made [Figure 4].
|Figure 3: Postoperative residual flap thickness 40 μ with collagen cross-links in the form of stromal haze secondary to corneal cross-linking|
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|Figure 4: Demonstrates the pre- and postoperative topographies of the left eye with differential map|
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PRK with CXL was performed on the left eye in June 2015 based on the wavefront refraction (1.25 DS, −0.75 DC at 110°) [Figure 5] and [Figure 6]. In February 2018, 32 months after wavefront-guided PRK/CXL, UDVA improved to 20/20 in the left eye [Figure 7]. Pentacam pachymetry was 465 μm and 414 μm in the right and left eyes, respectively. Endothelial cell count was 2656 and 2646, respectively, pre- and postoperatively.
|Figure 5: Demonstrates preoperative Zernike analysis of patient 2 with root mean square value of 2.543 and coma of 0.16|
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|Figure 6: Demonstrates postoperative Zernike analysis of patient with significant improvement to root mean square value of 0.552 and coma of 0.05|
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|Figure 7: Demonstrates progression of ectasia at 1st follow-up and topographic stability postsurgery|
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| Discussion|| |
Corneal ectasia is a rare but severe complication after corneal refractive surgery with a decline of biomechanical stability and vision. Treatment should be aimed at arresting the progression of ectasia and improving visual acuity. CXL has been proven to be clinically successful in halting the progression of ectasia by inducing CXL to increase corneal stiffness and stability. However, the role of CXL alone in improving the visual function is limited.
PRK-CXL has also been demonstrated effectively in eyes with keratoconus in studies by Kymionis et al. and in post-LASIK ectasia by topography-guided PRK by Kanellopoulos and Binder and Zhu et al. Considering the benefits of combined therapy, we applied the combined PRK-CXL procedure for post-LASIK ectasia.
Furthermore, deeper CXL can be achieved owing to the thinner flap thickness compared to CXL alone, as CXL is known to act in the anterior 250–350 μm part of the corneal stroma. As all our patients presented early, none of their ablation depth crossed 80 μ to correct refractive error, restricting ablation to flap only. The reason we performed PRK on the corneal flap was it does not contribute to postoperative corneal tensile strength. The desirable effect of the wavefront-guided PRK was to produce an emmetropic eye with least possible aberrations. After the procedure, all higher-order aberrations decreased. Especially coma-like root mean square was almost eliminated completely. Same-day simultaneous wavefront-guided PRK and CXL has its own advantages such as when wavefront-guided PRK is performed following the CXL procedure, some of the cross-linked anterior cornea is removed, minimizing the potential. By removing the Bowman layer with PRK, this may facilitate riboflavin solution penetration in the corneal stroma and less “shielding” of UVA light in its passage through the cornea, resulting in more effective CXL. A meta-analysis of seven studies shows that CXL is a promising treatment to stabilize the keratectasia after excimer laser refractive surgery without any deterioration on endothelial cell count and corneal thickness.,, Implantation of an allogeneic corneal lenticule, created by small incision lenticule extraction, is proven to be another effective way to treat post-LASIK ectasia.,,
The significant visual acuity improvement and documented stability of the ectasia during the postoperative follow-up insists that combined wavefront-guided PRK and CXL may offer an alternative solution to postlaser refractive surgery ectasia. Patients with early detected post-LASIK ectasia with small refractive errors which needs not more than 50% of flap thickness ablation can be considered for this procedure. Longer follow-up and larger patient sample is necessary to validate the safety and the stability of this combined procedure. This is first-ever series of wavefront-guided PRK, demonstrating that we now have a new method of achieving 6/6 visual acuity and mechanical stability of a serious complication while avoiding or delaying keratoplasty.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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