Laser in Situ Keratomileusis for High Myopic Refractive Error Beyond Recommended Range: Long-Term Follow-up Dr. Ashok P. Shroff, MD, Dr. Hardik Shroff, MD Shroff Eye Hospital, Near Railway Station, Navsari - India. We do not have any financial interest in this presentation… Purpose: To evaluate the results of Lasik in eyes with very high myopia after 4 years regarding its effectivity, predictability, stability and safety. Introduction: Lasik is better method than PRK because of modest healing response and lack of scar tissue 1,2,3. However to avoid postoperative keratectasia, minimum thickness of residual corneal stromal bad has been suggested at 250 µm 4. Therefore for lasik treatment upper refractive limits of -10 D / -12 D have been recommended. With older generation excimer machines and microkeratomes, the flap thickness would be more and treatment zone and ablation profile options were limited. Now with newer microkeratomes and excimer laser machines, 130 µm to 100 µm thick flaps, smaller treatment zones and various profiles are available. So that more diopter can be treated safely. Walter Sekundo et al have six year follow up of Lasik for moderate to high myopia with good results and no incidence of postoperative keratectasia 5. In this study, we have treated high to very high myopic refractive errors with very good results even after 4 years. Shroff Eye Hospital - India

Demography EyesMSE (D)Range (D) Full correction: to Under correction by -3.0 D (mean): to MSE = Mean Spherical Equivalent Total Eyes : 32 Preoperative Refraction Status No. of EyesUCVABCVA 6FC 1mt20/100 9FC 2mt20/80 9FC 3mt20/60 4FC 3mt20/40 2FC 4mt20/30 2FC 6mt20/20 Preoperative Visual Status All patients had UCVA between FC 1mt to FC 6mt. 24 eyes had BCVA of 20/100 to 20/60. 8 eyes had BCVA of 20/40 to 20/20 Eye was prepared as usual with topical proparacaine 0.5% drops. Flap maker microkeratome with 160 µ head was used to create flap. Gentian violet pen was used to make marks at two different places in UTQ & LTQ of cornea. Corneal flap was made as usual. After reflecting the flap, the stromal bed was dried, if required, by surgical spears. Treatment zone was set between 5mm to 6mm according to patients occupation and lifestyle. Laser ablation was done with MEL60 excimer laser. Stromal bad and flap inner surface were cleaned with BSS. Corneal flap was reposited and aligned and allowed to dry till it would adhere to the stromal bad. Routine antibiotics, tear substitutes and flurometholone ophthalmic suspension drops were used. Patients were followed next day, after 2 weeks, 2 months, 6 months, one year and 4 years. Procedure PatientsEyesSexAge (yrs) RELEMF to 35 (mean 22.7) Full correction: Group A - 25 eyes Under correction: Group B – 7 eyes Table 1 Table 2 Table 3 Shroff Eye Hospital - India

Pre Lasik: Pachymetry: 584 µm (Range 540 – 610 µm). K Value: D (mean) ( Range to D) Treatment –Full correction : 25 Eyes (Group A) –Under correction (by - 3 D) : 07 Eyes (Group B) Excimer laser : MEL 60 Microkeratome : Flap maker. All patients were comfortable during entire postoperative period except at times mild headache or symptoms related to dry eye 4 patients had some complaints regarding glare and haloes for initial 3 to 4 weeks but gradually disappeared without any additional treatment There was no complications regarding flap making as all flaps were of adequate size and thickness. Central average pre op. pachymetry which was 584 µm, was 447 µm after 3 months and 467µm after 4 years. Mean K value pre op. which was D, was D after 3 months and 38.2 D after 4 years. Observations MEL 60 FLAP maker Pre Op.Post Op. after 4 years RE LE Shroff Eye Hospital - India

Results: Residual Refractive Error 25 Eyes (Group A) (Full correction done) Residual Ref. Error (MSE) No. of Eyes After 3 months After 4 years D16 (64%) D 11 (44%) D3 (12%) D4 (16%) D 5 (20%) D2 (80%) D4 (16%) D5 (20%) After 3 months –16 eyes (64%) had residual refractive error at D –3 eyes (12%) had residual refractive error at D –4 eyes (16%) were at -1.0 D –2 eyes (80%) were at D However after 4 years there was some regression –11 eyes (44%) were at D –5 eyes (20%) were at D –4 eyes (16%) were at D –5 eyes (20%) were at D Total myopic refraction treated: 363 D –After 3 months Total refractive error corrected: D (96.35%) Total residual refractive error: D (3.65%) –After 4 years Total refractive error corrected: D (91.12%) Total residual refractive error: D (8.88%) Table 4 Regression (Reduction in Refraction) Between 3 M to 4 yrs: 96.35% to 91.12% Shroff Eye Hospital - India

Post op Ref. Error (MSE) No. of Eyes After 3 monthsAfter 4 years D2 (28.57%) D3 (42.86%) D-2 (28.57%) D2 (28.57%) D-3 (42.86%) D-2 (28.57%) Residual Refractive Error: 7 Eyes (Group B) (Under corrected by -3.0 D) Total myopic refraction treated: 133 D After 3 months –Total residual refraction: D (20.86%) –Total refractive error corrected: D (79.14%) After 4 years –Total reduction in refraction: 39.0 D (29.32%) –Total refractive error corrected: 94 D (70.68%) After 3 months –2 eyes (28.57%) had -3.0 D residual refractive error –3 eyes (42.86%) had D residual refractive error –2 eyes (28.57%) had D refractive error After 4 years, there was some regression –2 eyes (28.57%) were at D –3 eyes (42.86%) were at D –2 eyes (28.57%) were at D Table 5 Regression (Reduction in Refraction) Between 3 M to 4 yrs: 79.14% to 70.68% Shroff Eye Hospital - India

Results: Reduction in Refraction 25 eyes were treated for full myopic correction. –After 3 months, the refraction was D i.e. reduction in refraction was D (96.56%) –After 4 years, the refraction was D i.e. reduction in refraction was D (91.12%). In 7 eyes -3 D was less treated (under correction) than the preoperative D value as pachymetry was less. –After 3 months, the reduction in refraction was from -19 D to D i.e D (79.16%), but in reality, the refraction was corrected from D to D i.e D (94% ). –After 4 years, the reduction in refraction was from -19 D to D i.e D (71.05%), but in reality the reduction was from -16 D to D i.e D (84.38%). EyesPre op. Ref. (MSE) Post Lasik Refraction Reduction in Ref.Reality Reduction in Ref. 3 M4 Yrs3 M4 YRS3 M4 Yrs (Group A) D D D (96.35%) (91.12%) (Group B) 7 (- 3 D under correction) - 19 D (- 16 D) D D (79.16%) (71.05%) 94%84.38% Table 6 Shroff Eye Hospital - India

Results: Visual Recovery No. EyesUCVABCVA 420/3020/20 720/4020/30 520/5020/40 620/6020/40 320/10020/60 2FC 5 mt20/80 5FC 5 mt20/100 Table 7 BCVA Pre Op. (Eyes Post Op. (Eyes) 20/ / / / / / If we compare Table 3 & Table 7, we can realize that there is tremendous improvement in UCVA in group A (25 eyes). BCVA also improved in all eyes in group A. In group B of 7 eyes, where pre op. refraction error was very high, there is slight improvement in UCVA, however, BCVA was almost same. Incidentally, there was no loss of any line which may be due to no occurrence of flap related complications. BCVA less than 20/20 or 20/30 was due to moderate to severe myopic retinal degeneration. Results: Improvement in BCVA Table 8 Shroff Eye Hospital - India

Discussion: Lasik is still most popular method of correcting moderate to high myopic refractive error. In very high myopia development of keratectasia is most dangerous complication to be afraid about. Therefore phakic IOLs or clear lens extraction have been advocated to treat very high myopia or eyes who have very thin corneas. The femtosecond laser can customize the flap thickness even upto 100 µm, hence more corneal stroma is available for ablation. However as it is very cost effective, not available everywhere. Lasik has been successfully used to treat moderate to high myopia but follow up period is 1 to 2 years only 6,7,8. Walter Sekundo et al has recently published data with six years follow up 5. We have divided our treated eyes in two groups. Group A where full correction was possible and group B where cases have been under treated by - 3 D (MSE). In group A, our results are matching with other studies in terms of correction and visual recovery. Incidentally, there was no flap related or ablation related complications (we admit that we have seen complications like free cap, button holing, irregular or incomplete flap, gross under correction, over correction, regression in other eyes which are not part of this study). In group B, where 7 eyes had MSE -19D but they were treated for -16 D only due to inadequate availability of corneal stroma. If we look at Table 6, and evaluate our results in right perspective then it is evident that correction of refractive error was almost same as group A. Here 3 D which has been left out, should not be considered for evaluation because that much ablation was not done. Shroff Eye Hospital - India

32 eyes of 19 patients with high to very high myopia ( D to D) were treated with MEL60 Excimer Laser. 25 eyes (Group A) were treated for full correction as enough corneal stroma was available. 7 eyes (Group B) was under corrected by 3 D(MSE) as there was fear of keratectasia. Flaps of about 160 µm were made by Flap Maker microkeratome. Results are analyzed after 4 years. There was some regression over a period of time. After 4 years, total corrected refractive error D was D (96.35%) in group A while it was 94 D (70.68%) in group B. But in reality we could treat only 112 D and not 133 D (133 D – 21 D) that means 84.38% could be corrected as against 71.05% overall correction. Improvement in UCVA was significant. Lasik in high to very high myopia is quite effective, predictable, stable and safe procedure even after 4 years. Conclusion : In General There was no flap related complications. There was no complication related to procedure. There was significant change in pre and post lasik mid pachymetry and K Reading. Vision improved by 2 lines in 13 eyes (40.62%), by one line in 9 eyes (28.12%) and remained steady in 10 eyes. There was no loss of any line in this study. No excimer laser has one stage programme to treat any amount of high myopia. Therefore, we need to re-run the treatment programme for additional D. This may be reason for some residual / under correction. There was some regression between 3 months and 4 years in both the groups. (Refer Table 6). There was significant change in UCVA and BCVA in group A where total correction was possible. Discussion : Shroff Eye Hospital - India

References: 1.Pallikaris IG, Papatzanaki ME, Siganos DS, Tsilimbaris MK. A corneal flap technique for laser in situ keratomileusis; human studies. Arch Ophthalmol 1991; 109:1699 – Gu¨ell JL, Muller A. Laser in situ keratomileusis (LASIK) for myopia from –7 to –18 diopters. J Refract Surg 1996; 12:222– Knorz MC, Liermann A, Seiberth V, et al. Laser in situ keratomileusis to correct myopia of –6.00 to –29.00 diopters. J Refract Surg 1996; 12:575– Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg 1998; 14:312– Walter Sekundo, MD, Katrin Bo¨nicke, MD, Peter Mattausch, Wolfgang Wiegand, MD. Six-year follow-up of laser in situ keratomileusis for moderate and extreme myopia using a first generation excimer laser and microkeratome. J Cataract Refract Surgvol 29: June 2003: Han HS, Song JS, Kim HM. Long-term results of laser in situ keratomileusis for high myopia. Korean J Ophthalmol;2000; 14:1–6. 7.Lyle WA, Jin GJC. Laser in situ keratomileusis with VISX Star laser for myopia over –10.0 diopters. J Cataract Refract Surg 2001; 27:1812– Magallanes R, Shah S, Zadok D, et al. Stability after laser in situ keratomileusis in moderately and extremely myopic eyes. J Cataract Refract Surg 2001; 27:1007– Shroff Eye Hospital - India