|Year : 2021 | Volume
| Issue : 4 | Page : 625-629
Topography-guided laser in-situ keratomileusis to treat visual distortions due to higher-order aberrations induced after ablation procedures
Urvija Choudhary1, Ayushi Choudhary2, Rajiv Choudhary3
1 Department of Cornea and Refractive Surgery, Rajas Eye Hospital, Indore, Madhya Pradesh, India
2 Senior Resident, Department of Cataract and Refractive Surgery, Rajas Eye Hospital, Indore, Madhya Pradesh, India
3 Head, Department of Cataract and Refractive Surgery, Rajas Eye Hospital, Indore, Madhya Pradesh, India
|Date of Submission||13-Sep-2020|
|Date of Acceptance||05-Mar-2021|
|Date of Web Publication||09-Oct-2021|
Dr. Urvija Choudhary
24 Mishra Vihar, Near Geeta Bhavan Mandir, Indore - 452 001, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
A 27-year-old male, with a history of bilateral Laser in situ keratomileusis (LASIK) followed by photorefractive keratectomy, presented with complaints of disturbed quality of vision, the right eye worse than the left eye. Uncorrected distance visual acuity (UDVA) was 20/20 in both eyes. Corneal topography and wavefront aberrometry revealed slightly decentered ablation and increased higher-order aberrations in the right eye, respectively. A topography-guided femtosecond-assisted LASIK was performed for the right eye successfully reducing his visual symptoms and conserving UDVA at 20/20.
Keywords: Decentered ablation, high-order aberrations, irregular cornea, topography-guided LASIK, vision disturbances
|How to cite this article:|
Choudhary U, Choudhary A, Choudhary R. Topography-guided laser in-situ keratomileusis to treat visual distortions due to higher-order aberrations induced after ablation procedures. Indian J Ophthalmol Case Rep 2021;1:625-9
|How to cite this URL:|
Choudhary U, Choudhary A, Choudhary R. Topography-guided laser in-situ keratomileusis to treat visual distortions due to higher-order aberrations induced after ablation procedures. Indian J Ophthalmol Case Rep [serial online] 2021 [cited 2021 Oct 28];1:625-9. Available from: https://www.ijoreports.in/text.asp?2021/1/4/625/327657
Laser in-situ keratomileusis (LASIK) is the most common procedure performed for refractive error correction worldwide. Although most outcomes are quite precise, problems arising due to induced higher-order aberrations (HOAs) are a major challenge.,, Sometimes aberrations may appear due to decentered ablation resulting from an absence of an eye-tracking system, inadequate registration, or excessive eye movements during the surgery. Despite the advent of eye-tracking software, mild decentration may occur. Recent literature reports significant improvement in visual quality for the retreated eyes with topography-guided laser treatment.,, To our knowledge topography-guided retreatment for visual disturbances in eyes with uncorrected distance visual acuity (UDVA) of 20/20 is yet not reported. We report such a case of severe visual distortion resulting from two sequential laser vision corrections but maintaining 20/20 UDVA. It was a challenge to successfully correct the corneal irregularity while preserving UDVA.
| Case Report|| |
A 27-year-old male presented to our hospital with complaints of seeing objects smeared from one side, severe in the right eye compared to the left. He had undergone bilateral LASIK for moderate myopia 2 years back followed by bilateral photorefractive keratectomy (PRK) 6 months later for residual refractive error overseas. Preoperative records were not available. The patient confirmed the absence of any photopic symptoms prior to surgery and on-off use of lubricant eye drops for the last 2 years postsurgery.
Clinical evaluation revealed bilateral UDVA of 20/20. Image clarity improved partially with a pin hole. On slit-lamp examination, the cornea was clear with faint flap margins in both eyes, the surface was lustrous, and fluorescein staining revealed no punctate epithelial erosions. Tear film breakup time was 6–8 s in both eyes.
Three repeatable scans of each eye were taken using corneal topography (Pentacam, Oculus, Germany). Axial curvature map of the right eye displayed a decentered ablation pattern with a small optical zone [Figure 1]a, and the left eye had a centered ablation [Figure 1]b. Wavefront aberrometry (iTrace, Tracey technologies, USA) revealed increased HOAs in the right eye [Figure 2]a, [Figure 2]b, [Figure 2]c as compared to the left eye [Figure 2]d, [Figure 2]e, [Figure 2]f. HOAs were primarily anterior corneal and contributed mainly by coma. The pupil size measured on iTrace was 4.33 mm and 4.31 mm for the right and left eyes, respectively. On anterior-segment optical coherence tomography (CASIA 2, Tomey Corporation, Japan), an area of hyper reflection in anterior stroma demarcating the previous LASIK flap thickness of about 90–100 μ [Figure 1]c. A trial of mini-scleral contact lens improved the clarity of objects and reduced image distortion.
|Figure 1: (a) Corneal topography showing decentered ablation in the right eye; (b) centered ablation in the left eye; (c) AS-OCT of right eye showing flap thickness at different areas from the previous LASIK|
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|Figure 2: Chang analysis on iTrace (a and b) increased total eye aberrations in the right eye at 5 and 3 mm pupil, respectively; (c) HOAs in the right eye; (d and e) comparatively less total eye aberrations in the left eye from previous laser ablation; and (f) HOAs in the left eye|
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Topography-guided femtosecond LASIK was planned in the right eye for regularization of the cornea. Keeping a note of residual stromal bed and depth of ablation, a flap was created at 110 μm with a femtosecond laser. Four repeatable and highly reproducible scans obtained from the Placido-based Allegretto Topolyzer were transferred to EX500 WaveLight (Alcon Inc., USA). Q value was set to “zero,” and the optical zone was enlarged to 6.5 mm. C4–C12 adjustment was made to equalize defocus and spherical aberration by adding -0.55 diopter [Figure 3]. No residual refraction was there. Topography-guided excimer laser ablation was performed solely to correct HOAs [Figure 3]f.
|Figure 3: Topography-guided treatment planning (a) refraction set as zero initially; (b) ablation profile due to HOAs showing more ablation in the periphery; (c) Zernicke coefficients when refraction kept zero; (d) balancing C4–C12 to near equal values; (e) refraction modified to balance C4–C12; and (f) the final ablation profile to be treated|
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Postoperatively, the patient was prescribed topical drops—prednisolone 1% QID tapered over a month, moxifloxacin 0.5% QID for 15 days, and lubricating drops QID for 3 months. After 1 month, corneal topography showed regularization in the central 3 mm zone [Figure 4]e. Chang's analysis on iTrace displayed a marked reduction in HOAs [Figure 4]a, [Figure 4]b, [Figure 4]c, [Figure 4]d, [Figure 4]e, [Figure 4]f, [Figure 4]g, [Figure 4]h and simulated vision also improved [Figure 4]f in the right eye. UDVA was preserved at 20/20. The patient reported a significant improvement in the quality of vision.
|Figure 4: (a and b) Decentered ablation and distorted simulated vision on presentation; (c and d) Chang analysis on iTrace showing high HOAs in the right eye; (e) regularization of corneal topography in the central 3 mm optical zone after planning topography-guided treatment; (f) improved simulated vision after the treatment; and (g and h) marked reduction of aberrations in the right eye|
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| Discussion|| |
Visual disturbances after the laser ablative procedure with a UDVA of 20/20 are often neglected. Patients are reassured by prescribing lubricating eye drops and other medical management. With the advent of highly precise corneal topographers, aberrometers, and topography-guided laser corrections for corneal irregularities, such patients can be meticulously evaluated and benefitted.
Decentered ablations cannot be managed conservatively, thus taking maximum precautions during the surgery is critical. Making sure that the eye-tracking system is on, reducing the surrounding illumination so that patient focuses on fixating lights and encouraging the patient to keep eyes still during the procedure can help control decentered ablations to some extent. A surgeon should be watchful and immediately stop laser firing if the patient moves.
Complications after laser ablative procedures like induction of HOAs, decentered ablation, and small optical zone are very well documented. Several methods have been described to reduce aberrations and residual refraction in decentered eyes. Topography-guided retreatments have proven effective in highly aberrated eyes with irregular corneas.,, Wavefront-guided ablation can also be used to successfully correct the abnormal aberration created by a decentered ablation. They have been shown to reduce total HOAs in the setting of persistently symptomatic eyes after LASIK as well. Topography-guided treatment measures and treats the aberration at the place where it is produced, whereas wavefront measurements calculate the aberrations of the whole eye and are difficult to reproduce in highly aberrated eyes. Improvement in image clarity on applying mini-scleral contact lens also suggested the corneal origin of aberrations. Relifting the flap was not chosen as a second PRK procedure would have possibly created central thinning in the previous flap. Therefore, we used topographic-guided femtosecond LASIK to treat this unhappy patient, which satisfactorily reduced the visual distortions.
| Conclusion|| |
Our case demonstrates that topography-guided treatment is a good option to treat HOAs and decentered laser ablation in symptomatic eyes even with UDVA of 20/20 postrefractive surgery without altering their emmetropic status.
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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