|Year : 2016 | Volume
| Issue : 3 | Page : 114-122
Various topographic patterns of post-LASIK ectasia and their treatment modalities
Sherif A Eissa MD (Cairo University), FRCS (Glasgow)
Department of Ophthalmology, Cairo University, Cairo, Egypt
|Date of Submission||17-Jun-2016|
|Date of Acceptance||27-Oct-2016|
|Date of Web Publication||6-Dec-2016|
Sherif A Eissa
Kasr El Aini, 11451 Manial, Cairo
Source of Support: None, Conflict of Interest: None
The purpose of this study was to present different topographic presentations of keratectasia following laser in-situ keratomileusis (LASIK), and their management strategies.
The study was carried out in specialized eye hospital − Cornea and Refractive Unit.
This is a retrospective case series.
Patients and methods
The study enrolled 44 eyes of 29 patients who presented with post-LASIK ectasia, between 2011 and 2014. Eight eyes (18.18%) had previous LASIK surgery at our center and 36 eyes (81.81%) had LASIK procedure by surgeons outside our hospital.
Although 29 eyes (65.90%) presented early with crab-claw/pellucid-like pattern, only six eyes (13.63%) first presented with asymmetric bow tie with inferior steepening. Isolated inferior steep cone was the pattern in six eyes (13.63%), whereas three eyes (6.81%) presented early with superior steepness. Twenty-five eyes (56.81%) were managed by corneal collagen cross-linking (CXL) with riboflavin, followed 6 months later by toric implantable collamer lens in three eyes and implantable collamer lens in a single eye. Intracorneal ring segment implantation procedure was implemented in nine eyes (20.45%), whereas seven eyes (15.90%) had deep anterior lamellar keratoplasty done. Three patients − three eyes − (6.81%) refused treatment by cross-linking on early diagnosis, and they presented with progressive features of ectasia over 3 years, which finally required deep anterior lamellar keratoplasty.
Post-LASIK ectasia can manifest with various topographic patterns, at different onset points following LASIK, and unpredictable course of progression. Early diagnosis, proper discussion of the pros and cons of treatment modalities with the patient, and early intervention with the suitable corrective procedure is crucial.
Keywords: corneal ring segments, cross-linking, deep anterior lamellar keratoplasty, ectasia
|How to cite this article:|
Eissa SA. Various topographic patterns of post-LASIK ectasia and their treatment modalities. Delta J Ophthalmol 2016;17:114-22
| Introduction|| |
Corneal ectasia is a serious complication that may follow corneal refractive surgery. The most common scenario is progressive asymmetric inferior corneal steepening, progressive increase in myopia, irregular astigmatism, and corneal aberrations, followed by a consequent loss of corrected distance visual acuity (CDVA) that may require corneal transplantation . This corneal disorder has been described as a nightmare after refractive surgery, more often associated with laser in-situ keratomileusis (LASIK) surgery, compared with photorefractive keratectomy .
Major risk factors for ectasia include residual stromal bed thickness less than 250 μm, high myopic corrections, and preoperative thin corneas . Post-LASIK ectasia pathologically is a disruption of composite materials in a biomechanically weakened cornea when their structural integrity is compromised by excimer laser refractive surgery .
Any corneal specialist is currently offered effective transplant/nontransplant options that have expanded the treatment armamentarium available for post-LASIK ectasia . Cross-linking (CXL) may be used in the management of ectasia under standard Dresden, accelerated, pulsed, or transepithelial CXL protocol . However, regardless of the technique adopted, CXL can strengthen corneal tissue by increasing the formation of intrafibrillar and interfibrillar carbonyl-based covalent bonds through the process of photopolymerization .
Whether it is incomplete ring segments, Intacs and Ferrara ring, or complete intrastromal segment, Myoring, being implanted in ectasia, the same principle of modifying the corneal shape without tissue removal or manipulating the central cornea is adopted. The aim of this treatment is to improve spectacle-corrected vision, thus delaying or eliminating the need for a corneal transplant .
Deep anterior lamellar keratoplasty (DALK) in this study was indicated in advanced ectasia cases not candidate for CXL or intracorneal ring segment implantation (ICRS), with two or more findings of high Kmax (above 57 D), progressive decrease in CDVA to worse than 0.40 of Snellen lines, and decreased corneal thickness on two consecutive visits.
| Patients and methods|| |
The medical records of patients who presented with post-LASIK ectasia at Magrabi Eye Hospital (M.E.H.) − Aseer province − Kingdom of Saudi Arabia (KSA) in the period 2011–2014 were reviewed. Approval for this retrospective case series was obtained from the M.E.H. Ethical Committee. The study followed the tenets of the Declaration of Helsinki, and informed consent was obtained for every patient.
A diagnosis of corneal ectasia was made when the patients developed progressive corneal steepening, associated with an increasing myopic and/or astigmatic refractive error 3 or more months after LASIK surgery. These findings were combined with increasing inferior or superior corneal steepening and thinning, based on Scheimpflug tomography, plus deteriorated CDVA. Preoperative LASIK clinical data and topography were retrieved from our hospital database, in case surgery was performed initially inside our hospital. The above-mentioned data were requested from the referring physician or primary LASIK surgeon, in case the procedure was performed outside our hospital. Slit-lamp biomicroscopy confirmed the presence of LASIK flap in all patients. Each patient underwent manifest refraction, as well as measurement of uncorrected distance visual acuity and CDVA, using Snellen’s visual acuity chart. Keratometry readings (K) and topography were obtained by OPD scan II. Pachymetry was performed using Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany).
Of the 44 eyes enrolled in the study, 25 eyes (56.81%) were treated by corneal collagen cross-linking using Dresden protocol, as described below. A single surgeon (S.A.E.) performed all the procedures with the following technique. Corneal epithelium was removed with a beaver blade from the 9-mm treatment zone, and then 0.1% riboflavin–20% dextrane solution (Ricrolin; Sooft, Roma, Italy) was instilled every 5 min for 30 min. After the application of riboflavin, the corneal surface was washed thoroughly with a balanced salt solution. Ultrasound (US) pachymetry was then performed. If the cornea was thinner than 400 μm, distilled water was administered, after which US pachymetry was performed again to confirm that the stroma had swollen to more than 400 μm. This was followed by a 30-min exposure to UV irradiation of Gaussian profile (UV-X 2000, IROC INNOCROSS, Zurich, Switzerland), in accordance with riboflavin instillation every 5 min. At the end of the procedure, a bandage contact lens was applied. Postoperatively, moxifloxacin 0.5% (Vigamox Alcon Laboratories Inc., Texas, TX, USA) and prednisolone acetate 1% (Pred Forte; Allergan Inc., California, CA, USA) were prescribed six times daily for 2 weeks. The contact lens was removed after 4–5 days.
Nine eyes (20.45%) required ICRS implantation with the following technique. Surgical procedure was performed by the same surgeon (S.A.E.), under topical anesthesia. Two Intacs SK (Addition Technology Inc., Illinois, IL, USA) segments were inserted. The thickness of the segments was 0.200 mm for the upper tunnel and 0.450 mm for the lower tunnel. Femtosecond laser (iFS 150 mHz; AMO, Illinois, IL, USA) created two tunnels with 5.9-mm inner diameter and 7.1-mm outer diameter at a depth of 80% of thinnest location along the tunnel path, confirmed by US pachymetry. The inner and outer diameters of the tunnel were 5.9 and 7.1 mm, respectively. After proper dissection, the two polymethyl methacrylate segments were implanted in the clockwise and counterclockwise tunnels, through the 1.2-mm incision, keeping a space of 2.0 mm between their ends and 1.5 mm between the opposite edge of each ICRS and the edge of the incision. Intacs SK segments ended up central and deep to the LASIK flap edge, creating a central optic zone of 6.0 mm between them. The procedure was uneventful in two eyes, and no disruption of the LASIK flap occurred. In a single eye, insertion of the lower ring through the incision was misdirected to the more superficial LASIK interface, and the false pathway was corrected using the turn-around technique, by inserting the lower ring segment into the upper tunnel first and then pushing the latter with the upper tunnel segment to turn around the false tunnel. Patients received antibiotic and steroid combination eye drops four times daily for 1 week.
DALK was performed by the same surgeon (S.A.E.) in seven eyes of four patients, using Anwar big bubble technique. All patients who underwent DALK had poor CDVA and rigid gas-permeable contact lens intolerance preoperatively. To prepare the recipient bed, 8.00–8.50 mm recipient trephine was used (Moria Inc., Pennsylvania, PA, USA) to cut around 400-μm depth of the recipient cornea, with utmost care to avoid leaving any residual rim of the LASIK flap, by careful centration of larger-size trephine over the old flap. Big bubble was successfully created using a 27-G needle, and it was confirmed by performing the small bubble test. Deroofing of the bubble was performed using a superblade, followed by supradescematic dissection using iris spatula to achieve a fully bare Descemet’s membrane. Donor corneal button was punched from the endothelial side using donor punch (Moria Inc.) of the same size as the trephine used. The endothelium was scrapped completely from the donor button using Merocel sponge. The donor button was sutured to the recipient bed with 16 running monofilament 10-0 nylon sutures with buried knots. A subconjunctival injection of 4 mg dexamethasone and 20 mg gentamicin was given at the end of surgery. Sutures were removed in four patients 10–11 months post-DALK.
All patients enrolled in this study were followed up to 18 months postoperatively. All data were analyzed using the statistical software package SPSS version 15 (SPSS Inc., Chicago, Illinois, USA). Data were presented as mean±SD. Repeated measures were analyzed using one-way analysis of variance. A P value less than 0.05 was considered statistically significant.
| Results|| |
In the present case series, post-LASIK ectasia of mean Brenner grade 2.3636±0.99 was diagnosed within a mean duration of 13.568±4.13 months after LASIK surgery. Mean corneal thickness on the thinnest location point was found to be 436.59±26.32 μm on Scheimpflug pachymetry map.
Although 29 eyes (65.90%) presented early with crab-claw/pellucid-like pattern ([Figure 1]a and [Figure 8]a), only six eyes (13.63%) first presented with isolated inferior steep cone ([Figure 2]a). One case with isolated inferior steepness refused treatment, and revealed a crab-claw pattern ([Figure 2]b) 28 months later. Asymmetric bow tie with inferior steepening was the pattern ([Figure 3]a) in six eyes (13.63%), whereas three eyes (6.81%) presented early with the rare pattern of superior steepness ([Figure 4]). The percentage of topographic patterns among the total number of ecstatic eyes is shown in [Figure 5].
|Figure 1 (a) Pellucid-like topographic pattern. (b) Postcorneal ring segment implantation|
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|Figure 2 (a) Post-LASIK ectasia presented with isolated inferior steepness. (b) Pattern changed to crab-claw after 28 months, with no treatment applied.|
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|Figure 3 (a) Asymmetric bow tie with inferior steepness. (b) Topography showing progressive ectasia that required deep anterior lamellar keratoplasty (DALK).|
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|Figure 5 Percent of various treatment modalities in relation to total cases with post-LASIK ectasia|
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CXL was performed in 25 eyes (56.81%) ([Figure 6]), followed 6 months later by toric implantable collamer lens in three eyes and implantable collamer lens in a single eye. Intacs SK implantation procedure was implemented in nine eyes (20.45%) ([Figure 7]), whereas seven eyes (15.90%) had DALK. Three patients with three affected eyes (6.81%) refused treatment by cross-linking on early diagnosis, and presented with progressive features of ectasia over 3 years ([Figure 8]b), and over 1 year ([Figure 3]b), which finally required DALK. The percentage of treatment modalities for ectasia patients in the current series is shown in [Figure 9].
|Figure 7 Ectasia before and after Intacs SK rings implantation on axial difference map.|
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|Figure 8 Progressive ectasia in a patient who refused treatment in early stage (a), which necessitated deep anterior lamellar keratoplasty (DALK) in advanced stage (b).|
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|Figure 9 Percentage of various treatment modalities in relation to total cases|
with post-LASIK ectasia.
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Mean uncorrected visual acuity (UCVA), CDVA, manifest refraction spherical equivalent, and steepest K of all patients were compared before and after management, throughout the follow-up period, postoperatively ([Table 1]).
All the Intacs SK patients had improved UCVA of 2–4 lines, compared with preoperative vision, and improved 1–5 lines of CDVA, compared with preoperative best corrected vision. [Figure 1]b shows axial and instantaneous map, 1 month after Intacs SK rings implantation. [Figure 7] demonstrates the axial difference map and the influence of corneal ring segment implantation on topography pattern and corneal steepness.
With regard to the DALK group, five eyes had an improved CDVA of 5–6 lines and two eyes improved by 8–9 lines. All eyes had UCVA improved by 3–7 lines.
Of the 25 cross-linked eyes, 21 eyes showed no improvement in UCVA, three eyes showed improvement by 1 line, and only one eye lost 1 line of UCVA. The CDVA was shown to be stable in 21 eyes and improved in four eyes by 4 lines. [Figure 6]b demonstrates an example of topography changes 20 months following corneal collagen cross-linking.
| Discussion|| |
Brenner and colleagues in 2012 proposed a grading system for post-LASIK ectasia, in which four groups were formed, each representing a different degree of visual limitation as follows: grade 1, no visual limitation, with a decimal CDVA of at least 0.9; grade 2, mild visual limitation, with a decimal CDVA between 0.7 and 0.9; grade 3, moderate visual limitation, with a decimal CDVA between 0.5 and 0.7; and grade 4, severe visual limitation, with a decimal CDVA worse than 0.5. The post-LASIK ectasia grading system was consistently represented by the differences in the severity variables of the disease . On the basis of this grading system, the same team in another following study concluded that the odds of a gain of at least 1 line of CDVA after ICRS implantation was 18 times greater for those who had lost at least 2 lines of CDVA after ectasia evolved − that is, grades 2–4. On the other hand, the risk for vision loss after ICRS implantation increased 7.5-fold for those who had lost a maximum of 1 line of post-LASIK ectasia CDVA − that is, grade 1 .
In the present study, the nine eyes with post-LASIK ectasia treated with the Intacs SK had topographic findings that remained stable during the 1-year follow-up. All patients had improved UCVA of 2–4 lines, compared with preoperative vision, and improved 1–5 lines of CDVA, compared with preoperative best corrected vision. Subjective symptoms in the early postoperative period included night glare and halos. No intraoperative or postoperative complications occurred. Kamburoglu and colleagues reported that, in a comparative study between Intacs SK and Intacs implantation in patients with advanced keratoconus, refractive results and K readings seem to be better improved in Intacs-SK-implanted eyes when compared with Intacs-implanted eyes. Intacs SK are implanted in a 6-mm zone, whereas the previous Intacs were implanted in a 6.8-mm zone. This characteristic offers the possibility of increasing the possible effect of Intacs SK (in comparison with the previous model) and avoiding segment interference with the edges of the LASIK flap .
Cross-linking was performed according to the Dresden protocol, as described earlier. Similar studies on cross-linking for post-LASIK ectasia evaluated manifest refraction spherical equivalent, UCVA, CDVA, and arrest of disease progression over months postoperatively. A study on 26 patients with ectasia was carried out by Richoz et al. , who followed up the patients for around 25 months after cross-linking. In their study, the CDVA improved (gain≥1 line) in 19 cases and remained stable in seven patients. No patient lost lines of CDVA. Hafezi et al.  and Aydin et al.  found a decrease in maximum K value in patients with post-LASIK ectasia, which is a crucial sign to ensure the success of CXL to halt the ectasia process. In the present study, of the 25 cross-linked eyes, 21 eyes showed no improvement in UCVA, three eyes showed improvement by 1 line, and only one eye lost 1 line of UCVA, whereas CDVA was shown to be stable in 21 eyes, and improved in four eyes by 4 lines.
DALK with the Anwar big-bubble technique was used in seven cases in this study, compared with Javadi and Feizi , who performed the procedure in 11 eyes with post-LASIK ectasia. In the present study, five eyes that underwent DALK had an improved CDVA of 5–6 lines and two eyes improved by 8–9 lines. All eyes had UCVA improved by 3–7 lines post-DALK. One of the limitations of DALK in the management of post-LASIK ectasia is the unpredictable outcome of UCVA, which may be attributed to the fact that post-DALK spherical equivalent (SE) refraction reflected the pre-LASIK SE refraction (i.e. hyperopic eyes remained hyperopic and myopic eyes remained myopic), confirming that pre-LASIK ametropia is the major determinant in post-DALK ametropia . In a study by Ramin and colleagues, 20 eyes of 18 patients with ectasia were managed by DALK using Melles manual dissection technique. Mean Snellen CDVA improved significantly from 0.104 before DALK to 0.86 after DALK .
The major limitation of the present study was incomplete pre-LASIK data endorsement by the LASIK surgeons outside our center, because of their noncooperation. The low number of patients may be attributed to the misdiagnosis of post-LASIK ectasia by refractive surgeons and/or ophthalmologists. Besides, some patients refused treatment, as stated in results section, and were excluded from the study.
Early diagnosis of post-LASIK ectasia, proper discussion of the pros and cons of available treatment modalities with the patient, and early intervention with the suitable corrective procedure are the mainstay in salvaging best visual outcome in these cases.
The author thanks Dr Ahmed Hassanein for statistical analysis and Dr Mohamed Dawood for referral of patients and data collection.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]