Epithelial Ingrowth: Visual Acuity and Astigmatism Results One Year after YAG Laser Treatment

Purpose: To assess the response of YAG laser for epithelial ingrowth in LASIK patients undergoing re-treatment with flap re-lift, after one year. Materials and Methods: Prospective case series of LASIK patients with a symptomatic decrease in VA due to epithelial ingrowth (grades II-III), after retreatment with flap relift, with YAG laser (0.6-0.8 mJ) and followed-up during one year. Variables included pre and post YAG laser uncorrected visual acuity (UCVA, decimal scale), spherical equivalent (SE), topography astigmatism (SimK, 3.00 mm, and 5.00 mm zones). Data was registered and analyzed using Microsoft® Excel® 2013 (Microsoft Corporation), reported as mean, standard deviation (SD), and compared using paired t-student (p ≤ 0.05 for significance). Results: Nine patients were followed-up, for one year, 5 men and 4 women with mean age 46.8 ± 11-7 years. Pre/post results were: UCVA 0.75 ± 0.12/0.96 ± 0.09 (p=0.03), astigmatism 0.5 ± 0.68/0.10 ± 0.22D (p=0.03), SE 0.48 ± 0.46/0.25 ± 0.42D (p=0.24), topography astigmatism 2.0 ± 0.85/1.4 ± 0.45D (p=0.02), Km 39.3 ± 2.7/39.4 ± 2.4D (p=0.50). For pseudophakic patients pre/post mean UCVA 0.75 ± 0.24/0.83 ± 0.17 (p=0.22), SE 0.03 ± 0.80D / 0.06 ± 0.13D (p=0.94), astigmatism 0.49D ± 0.59/0.13D ± 0.25D (p=0.94), topographic astigmatism 2.8 ± 1.7D/2.5D ±1.1D (p=0.34). Conclusions: YAG laser treatment for symptomatic epithelial ingrowth, in LASIK patients after retreatment with flap relift, significantly improved UCVA and decreased subjective and topographic astigmatism. Clinical and topographical improvement in pseudophakic patients was not clinically significant.


Results
Nine LASIK patients with symptomatic epithelial ingrowth, after flap re-lift, were treated with YAG laser photodisruption and followedup for one year. We studied 5 men and 4 women, mean age of 46.8 ± 11.7 years, 5 right eyes, 4 left eyes, and mean time before UCVA decrease, due to ingrowth, was 11.8 ± 12.7 months. No complications were recorded during the procedure. Two patients had undergone previous surgical flap re-lifting and epithelium debridement before the YAG laser procedure, and 4 were pseudophakic. Evaporative dry eye syndrome, ocular Rosacea, or both, were observed in 3 patients who underwent YAG laser, exclusively. These were treated with lid hygiene and artificial tears during at least 6 months. One case required an additional YAG laser procedure, one month after performing the first YAG laser, due to lack of clinical improvement.
One case (65-year old pseudophakic woman) presented with corneal erosion, which was successfully treated with artificial tears, during 3 months. Her UCVA increased from 0.8 to 0.9 (no improvement in best corrected visual acuity; BCVA) and topography astigmatism decreased from 3.1D to 2.8D, one year after treatment. Table 1 reviews pre and post YAG laser results for all patients, after 12 months. Figure 1 compares case by case topographic astigmatism results after 6 and 12 months. Figure 2 displays mean topographic results one year after YAG laser for Sim K, on the 3.0mm and 5.0mm zones. Figure 3 shows pre and post YAG laser topographic astigmatism results in pseudophakic patients. Clinical and topographical follow-up of an epithelial ingrowth case treated exclusively with YAG laser is shown on Figure 4.    Results for patients who had previously undergone unsuccessful flap re-lift and debridement, one year after YAG laser treatment, were: for the first case, pre-YAG laser uncorrected VA (UCVA) increased 0.6 (1.0 BCVA with +2.0 -1.0 × 180°; 1.9 D topography astigmatism) to post YAG laser UCVA 1.0 (1.2 BCVA with +0.75 and 1-3D topography astigmatism). In the second case, UCVA increased (0.5 to 0.9; no improvement in BCVA) and topography astigmatism decreased from 1.5 D to 0.6 D after one year.

Discussion
Post LASIK epithelial ingrowth is a fairly common complication, up to 32%, particularly after retreatment, flap complications, bleeding, etc., and treatment is determined by clinical evolution [1][2][3]. According to Machat´s classification, grade I epithelial ingrowth (thin, transparent line, 1-2 cells, well limited, within 2mm of flap border, and non-progressive) requires observation and treatment for grades II (thicker nest, within 2 mm of flap border, no demarcation line and transparent cells without ocular surface pathology) and III (confluent greyish-white opacities well beyond 2 mm of the flap border, geographic areas made of up white necrotic cells, flap border irregularities/thick flap margins) is surgical (flap re-lifting and debridement) [1].  Histopathology has reported that early epithelial ingrowth resembles normal corneal epithelium, multilayered squamous epithelium, while late ingrowth are made up of clumps of amorphous material with scarce cells [10]. Classical treatment consists in flap relifting and surface debridement with or without sutures, phototherapeutic keratectomy, alcohol or mitomycin use, amniotic membrane, or even flap amputation [1][2][3][4][5][6][7]. YAG laser has been recently reported as a successful treatment for epithelial ingrowth, with important visual and topography profile improvement [8-9]. YAG laser high powered pulse induces plasma formation and shock wave photodisruption [11]. Eighty to 100% improvement in VA and topographic surface regularity have been reported in patients with epithelial ingrowth treated with YAG laser [8-9]. We report statistically significant improvement in mean VA, 0.75 to 0.96 (p=0.03). Nine out of 10 cases reported VA improvement of at least 1 line and in one case VA decreased one line. The latter had dry eye syndrome due to ocular rosacea and has been treated with artificial tears. All pseudophakic patients improved their VA, though not significantly.
Mean subjective and topography astigmatism decreased significantly, and topographic astigmatism improved in 90% of cases. The patient which failed to improve had been diagnosed with ocular rosacea and treated for dry eye syndrome. Mean topography astigmatism for the 3.0 mm and 5.0 mm zones also decreased but results were not statistically significant. Mean subjective and topography astigmatism also decreased in pseudophakic patients, though not statistically significant.
Previous flap re-lifting and mechanical debridement had been unsuccessful in two of our cases, which were later treated with YAG laser. UCVA and topography astigmatism also improved, one year after YAG laser treatment.
Our results show that YAG laser photodisruption for epithelial ingrowth, as a first treatment option or after failed surgical treatment, significantly improved UCVA and both subjective and topographic astigmatism, after 1-year follow up.