Dr.Sheetal Brar,Dr.Sri Ganesh
ABSTRACT
Purpose: To evaluate the visual and refractive outcomes, changes in keratometry, pachymetry , higher order aberrations and asphericity following tissue addition technique in moderate to high hyperopia
Methods: This retrospective study included 30 eyes of 17 patients (mean age 27 years) with unilateral or bilateral hyperopia. Femtosecond laser was used to create a pocket in patient’s cornea, into which a cryopreserved/fresh lenticule, obtained from myopic patients undergoing ReLEx SMILE and matched for refractive error, was implanted. Mean follow up was 2 years (range 8 – 24 months).
Results: Based on values before and 4 year after the procedure, clinical improvement was noted in best corrected visual acuity (0.19 ± 0.22 logMAR v/s 0.15 ± 0.11logMAR), manifest spherical equivalent (4.73 ± 1.65D v/s +0.65 ± 0.59), mean CCT (551.23 ± 43.00µ v/s 600.87 ± 46.54). Mean keratometry increased from 44.3±2.51D to 46.7±2.11D. Asphericity changed from -0.37 ± 0.33 to -0.96 ± 0.19 . Pre op and post op higher order aberrations were 0.20 µ and 0.32µ respectively. One patient developed bilateral interface haze, for which the lenticules were explanted, followed by reimplantation of fresh lenticules. Both eyes of another patient with high hyperopia of + 9.0DS had a residue of +2.5DS, for which bowman’s membrane relaxation was done using a Barren trephine.
Conclusion: At 4 years, tissue addition technique was found to be safe and effective to treat moderate – high hyperopia. Potential advantages are less chances of regression, less induced aberrations, no flap complications, reversible and any residual refractive error can be managed effectively.
Keywords: FILI, Tissue addition, Hyperopia, Lenticule, SMILE, Cryopreservation
CTRI Reference number : REF/2015/06/009258
Introduction
With the advent of technology, refractive surgery has shown a significant growth in the recent years, with a change in the trend from flap to flapless correction for myopia correction. Small incision lenticule extraction (SMILE) procedure has been evaluated in comparsion to LASIK in numerous studies, and has been shown to provide comparable or better results in terms of safety, predictability, post-operative dry eye, induction of higher –order aberration and biomechanics(Ref).The by-product of the procedure provides a corneal lenticule, which is predominantly stromal collagen tissue.
This lenticule has been used by some researchers as an allogenic inlay to potentially treat conditions like hyperopia, keratoconus, corneal lamellar defect and presbyopia(Ref). Recently, our group reported the initial outcomes of tissue addition technique, which we call FILI (Femtosecondlaser Intrastromal Lenticule Implantation) for hyperopia correction(ref).The procedure was found to be safe and fairly effective in managing moderate hyperopia in 6 months follow-up in the exploratory phase of the study involving 9 eyes.
The aim of this paper, however, is to report the long term visual and refractive results of the first 30 eyes treated with FILI for hyperopia, along with discussion of some complications observed in a long term follow-up of two years.
Materials and Methods
This retrospective study included eligible patients who underwent FILI for hyperopia from July 2013 till July 2017, and had completed at least 2 years follow-up. The study was approved by institutional ethics committee and adhered to the tenets of the Declaration of Helsinki. Before the surgery was performed, an informed consent explaining the nature of the procedure along with the possible benefits and risks, was obtained from each patient participating in the study.
Inclusion criteria were- age between 21- 40 years, hyperopia between +2 to +10 D spherical equivalent (SE) with a maximum astigmatism of 1 D, stable refraction (<0.5 D change in past 12 months), corrected distant visual acuity(CDVA) of 6/36 or better, healthy ocular surface, absence of corneal ectatic diseases,corneal scars, absence of any retinal pathology likely to affect visual outcomes and assured follow-ups.
Eyes with dense amblyopia (CDVA <6/60), diagnosed or suspicious cases of corneal ectatic conditions, severe dry eyes and contact lens induced allergy, patients on systemic steroids, immune suppresants, oral contraceptives, antidepressants, pregnant females and patients with unrealistic expectations were excluded from the study.
Preoperative evaluation
All patients underwent a thorough preoperative evaluation including anterior and posterior segment examination, cycloplegic and subjective refraction, assessment of uncorrected and corrected distance visual acuity, corneal topography using Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Orbscan II (Bausch and lomb, Rochester, NY), abberometry (Hoya iTrace, surgical workstation, Japan), specular microscopy (Tomey, Japan) and dry eye evaluation (Schirmer 1 and tear film break up time).Patients using soft and rigid contact lenses were instructed to discontinue their lenses at least one and 3 weeks respectively, prior to the topographic evaluation.
Treatment planning and surgical technique : While planning the treatment, a corneal lenticule, which was obtained from a donor patient who had undergone SMILE for myopia correction was implanted into the recipient eye. The lenticule to be implanted was matched for the spherical equivalent and adjusted for the back vertex distance of the hyperopic patient eye. The donor lenticules were sourced either from a cryobank or obtained fresh(depending upon availability of tissue), in the latter case both the SMILE surgery of the donor and FILI surgery of the recipient were planned on the same day. If cryopreserved lenticules were used, they were thawed and prepared with the method previously described(ref).On the other hand, if fresh lenticules were used, they were immediately stored in a glass vial, containing balanced salt solution under sterile conditions. It was ensured that these lenticules were used for the FILI procedure within 2 hours of storage, to prevent excessive oedema from developing.
All surgeries were performed by a single experienced refractive surgeon(S.G.)under topical anesthesia using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany), with a pulse repitition rate of 500 KHz and a cut energy of 160 nj using the surgical technique described earlier(ref).Essentially in all cases, a pocket was created at 160 µm depth , which was dissected with blunt spatula followed by which the donor lenticule was inserted and centered on the visual axis.
For the initial 15 eyes operated, an incision size of 4 mm created superiorly, was used to allow insertion of the donor lenticule using two micro-forceps( ). However, for the subsequent cases a special T-shaped inserter (Epsilon surgicals, Mumbai, India ) was used, which allowed the insertion of lenticule tissue through a superior 2 mm incision. For one case, which had against the rule corneal astigmatism on topography in both eyes, 2 mm incision on steep axis was used (temporal incision).
All surgeries were uneventful and no intraoperative complications such as suction loss, lenticule tear / damage or incision tears occurred in any of the eyes.
Postoperative medications included topical 0.3% Ofloxacin (Exocin®, Allergan, Irvine, U.S.A.) 4 times for 3 days, 0.1% prednisolone acetate eye drops (Pred Forte®, Allergan, Irvine, U.S.A.) in tapering dosage for 3 months, hypertonic saline
(Hypersol- 5, Jawa pharmaceuticals, India ), and lubricants 4 times for 4 weeks or more.
Post-operative follow-ups were conducted day 1, 2 weeks, 6 months, 1 year and yearly afterwards. On all review visits from 2 week onwards, assessment of UDVA, manifest refraction, corrected distant visual acuity (CDVA) and topography was performed.
Statistical Analysis: SPSS software for Windows version 17.0.0 (IBM Corp., Armonk, NY) was used for statistical analysis .All values were expressed as mean ± standard deviation (SD). Independent sample t test was carried out for intergroup comparison of means. A p-value of 0.05 or less was considered statistically significant. JRS standard graphs were generated using Datagraph-med 5.20 software.
Results
A total of 30 eyes from 17 patients( mean age =27.3±5.7 years, 6 males and 11 females) underwent FILI procedure for hyperopia correction during the study period. Seventeen (17/30) eyes had associated mild to moderate amblyopia with Snellen’s CDVA ranging from 6/9 -6/36. For 18 eyes, a cryopreserved SMILE lenticule was used (mean time of cryopreservation=115 days, range=19 to 211 days), and for the remaining 12 eyes a fresh lenticule was used for implantation. The mean age of the SMILE donor patients was 29.19±5.2 years. One eye had FILI for treatment of traumatic aphakia in which a cryopreserved lenticule of +10 D was implanted, was excluded from the statistical analysis.
Visual Outcomes
Efficacy (Post-operative UDVA/ Preoperative CDVA)
At 4 years, the mean post UDVA was 0.15 ±0.22 LogMAR, which was slightly better than the pre CDVA of 0.19±0.22 LogMAR, however the improvement was not statistically significant( p=0.24)(Table1).The efficacy index was 1.16.
All eyes had UDVA 20/50 or better with 52 % eyes with UDVA of 20/20 or better compared to pre-op where this percentage was 41% (Figure 1)
Safety (Post-operative CDVA/ Preoperative CDVA)– At the end of 2 years mean follow-up, 21 % eyes gained 1 line, 17% gained 2 lines and 7% eyes gained more than 2 lines of CDVA.However, 55% eyes showed no change in CDVA.No eye lost lines of CDVA at the end of 2 years mean follow-up, the safety index being 1.15( Figure 2)
Refractive outcomes
The mean SE reduced from +5.00 ±2.18 D preoperatively to +0.40±0.24 D, at the end of 2 years follow up (p=0.000). 95% eyes were within ±0.50 D, while all eyes were within 1.50 ± D of SE correction.
Long term Complications: One patient underwent lenticule exchange with a fresh lenticule for presumed stromal rejection in both eyes, and remained stable after that. There was no incidence of infectious keratitis , corneal decompensation or stromal melt in our series. Both eyes of another patient with high hyperopia of + 9.0DS had a residue of +2.5DS, for which bowman’s membrane relaxation was done using a Barren trephine.
Conclusion: At 4 years, tissue addition technique was found to be safe and effective to treat moderate – high hyperopia. Potential advantages are less chances of regression, less induced aberrations, no flap complications, reversible and any residual refractive error can be managed effectively.
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