Effect of Acute Biomechanical Changes on Corneal Curvature After Photokeratectomy

Journal of Refractive Surgery - Tập 17 Số 6 - Trang 658-669 - 2001
William J. Dupps1, Cynthia J. Roberts2
1Biomedical Engineering Center and College of Medicine & Public Health, The Ohio State University, Columbus 43210, USA.
2The Ohio State University

Tóm tắt

ABSTRACT PURPOSE: Unintended hyperopia shift; is a common yet poorly understood complication of phototherapeutic keratectomy (PTK) that raises fondamental questions about the etiology of corneal curvature change in PRK and LASIK. We investigated the relative contributions of ablation profile and peripheral stromal thickening to intraoperative PTK-indueed central flattening, and propose a biomechanical model of the acute corneal response to central ablation. METHODS: Fourteen de-epithelialized eye bank globes from seven donors underwent either broadbeam ablation (~100-??? depth, no programmed dioptric change) or sham photoablation in pairedcontrol fashion. Peripheral stromal thickness changes and the pattern of thickness loss across each ablation zone were evaluated by optical section image analysis as predictors of acute corneal flattening. RESULTS: Relative to sham ablation, keratectomy caused significant anterior corneal flattening (-6.3 ? 3.2 D, P = .002). Concomitant peripheral stromal thickening (+57 ? 43 ??\, P = .01) was a significant predictor of acute hyperopic shift (r = 0.68, P - .047). Ablation pattern bias did not consistently favor hyperopia and was a poor lone predictor of hyperopic shift. CONCLUSIONS: Unintended keratectomyinduced hyperopic shift is replicable in a human donor model and is associated with significant thickening of the unablated peripheral stroma. This biomechanical response may have a considerable impact on early refractive outcomes in PTK, PRK, and LASIK [J Refract Surg 2001;17:658-669]

Từ khóa


Tài liệu tham khảo

1. Thompson VM. Excimer laser phototherapeutic keratectomy: clinical and surgical aspects. Ophthalmic Surg Laeers 1995;26:461-472.

2. Munnerlyn CR Koons SJ Marshall J. Photorefractive keratectomy: a technique for laser refractive surgery. J Cataract Refract Surg 1988;14:46-52.

3. Sher NA Bowers RA Zabel RW Frantz JM Eiferman RA Brown DC Rowsey JJ Parker P Chen V. Clinical use of the 193-nm excimer laser in the treatment of corneal scars. Arch Ophthalmol 1991;109:491-498.

4. Gartry D Kerr Muir M Marshall J. Excimer laser treatment of corneal surface pathology: a laboratory and clinical study. Br J Ophthalmol 1991;75:258-269.

5. Stark WJ Chamon W Kamp MT Enger CL Renes EV Gottsh JD. Clinical follow-up of 193-nm ArF excimer laser photokeratectomy. Ophthalmology 1992;99:805-812.

6. Campos M Nielsen S Szerenyi K Garbus JJ McDonnell PJ. Clinical follow-up of phototherapeutic keratectomy for treatment of corneal opacities. Am J Ophthalmol 1993;115:433-440.

7. Starr MS Donnenfeld E Newton M Tbstanoski J M?ller J Odrich M. Excimer laser phototherapeutic keratectomy. Cornea 1996;15:557-565.

8. McDonnell PJ Seiler T. Phototherapeutic keratectomy with excimer laser for Reis-Buckler's corneal dystrophy. Refract Corneal Surg 1992;8:306-310.

9. Hersh PS Spinak A Garrana R Mayers M. Phototherapeutic keratectomy: strategies and results in 12 eyes. Refract Corneal Surg 1993;9(suppl):S90-S95.

10. Fagerholm P Fitzsimmons TD ?rndahl M ?hman L Tengroth B. Phototherapeutic keratectomy: long-term results in 166 eyes. Refract Corneal Surg 1993;9(suppl): S76-S81.

11. Hahn TW Sah WJ Kim JH. Phototherapeutic keratectomy in 9 eyes with superficial corneal diseases. Refract Corneal Surg 1993;9(suppl):Sll5-SH8.

12. ?rndahl M Fagerholm P Fitzsimmons T Tengroth B. Treatment of corneal dystrophies with excimer laser. Acta Ophthalmol 1994;72:235-240.

13. O'Brart DPS Gartry DS Lohmann CP Patmore AL Kerr Muir MG Marshall J. Treatment of band keratopathy by excimer laser phototherapeutic keratectomy: surgical techniques and long term follow up. Br J Ophthalmol 1993;77:702-708.

14. Rogers C Cohen P Lawless M. Phototherapeutic keratectomy for Reis Bucklers' corneal dystrophy. Austral N Zealand J Ophthalmol 1993;21:247-250.

15. Seiler T. Der excimer-laser: ein Instrument f?r die Hornhautchirurgie. Der Ophthalmologe 1992;89:128-133.

16. Azar D. Quoted by: Stark WJ Chamon W Kamp MT Enger CL Renes EV Gottsh JD. Clinical follow-up of 193-nm ArF excimer laser photokeratectomy. Ophthalmology 1992;99:805-812.

17. Bryant MR Fredericks DJ Campos M McDonnell PJ. Finite element analysis of corneal topographic changes after excimer laser phototherapeutic keratectomy [Abstract]. Invest Ophthalmol Vis Sci 1993;34(suppl):S804.

18. Maurice DM. The cornea and sclera. In: Davson H ed. The Eye. Vol. Ib: Vegetative physiology and biochemistry. Orlando FL: Academic Press; 1984:1-158.

19. Jakus MA The fine structure of the human cornea. In: Smelser GK ed. The Structure of the Eye. New York NY: Academic Press; 1961.

20. Ehlers N. Mechanical factors in the maintenance of normal corneal deturgescence. Acta Ophthalmol 1967;45:658-672.

21. McNicol LA Strahlman E eds. Corneal Biomechanics and Wound Healing. Proceedings of Workshop on Corneal Biophysics I; 1989 Sept 27-29; Bethesda MD: National Eye Institute 1989.

22. Bierly JR Hainsworth DP Schmeisser ET Baker RS. Effect of extraocular muscle surgery on corneal topography [Abstract]. Invest Ophthalmol Vis Sci 1993;34(suppl):S1249.

23. Komai Y Ushiki T The three-dimensional organization of collagen fibrils in the human cornea and sclera. Invest Ophthalmol Vis Sci 1991;32:2244-2258.

24. Polack FM. Morphology of the cornea I: study with silver stains. Am J Ophthalmol 1961;51:179.

25. Ehlers N. Studies on the hydration of the cornea with special reference to the acid hydration. Acta Ophthalmol 1966;44:924-925.

26. Waring GO HI. Corneal structure and pathophysiology. In: Leibowitz HM ed. Corneal Disorders: Clinical Diagnosis and Management. Philadelphia PA: WB Saunders; 1984: 3-25.

27. Smolek MK McCarey BE. Interlamellar adhesive strength in human eyebank corneas. Invest Ophthalmol Vis Sci 1990;31:1087-1095.

28. Smolek MK Interlamellar cohesive strength in the vertical meridian of human eye bank corneas. Invest Ophthalmol Vis Sci 1993;34:2962-2969.

29. Terry MA Ousley PJ Zjhra ML. Hydration change in cadaver eyes prepared for practice and experimental surgery. Arch Ophthalmol 1994;112:538-543.

30. Koers DM. The measurement of human corneal thickness by photography [Master's Thesis]. Columbus OH: The Ohio State University; 1982.

31. von Bahr G. Measurements of the thickness of the cornea. Acta Ophthalmol 1948;26:247-265.

32. Zantos SG. The ocular response to continuous wear of contact lenses [Dissertation]. University of South Wales; 1981.

33. Montgomery DC Peck EA. Introduction to Linear Regression Analysis. 2nd ed. New York NY: John Wiley & Sons; 1992:161-192.

34. Gordon A Boggess EA Molinar JF. Variability of ultrasonic pachometry. Optometry Vis Sci 1989;67:162-165.

35. Reader AL SaIz JJ. Differences among ultrasonic pachymeters in measuring corneal thickness. J Refract Surg 1987;3:7-11.

36. Litwin KL Moriera H Ohadi C McDonnell PJ. Changes in corneal curvature at different excimer laser ablative depths [Letter]. Am J Ophthalmol 1991;111:382-384.

37. Moller-Pedersen T Cavanagh HD Petroli WM. Instability and haze development after photorefractive keratectomy: a 1-year confocal microscopic study. Ophthalmology 2000;107:1235-1245.

38. Gilbert ML Roth AS Friedlander MH. Corneal flattening by shallow circular trephination in human eye bank eyes. Refract Corneal Surg 1990;6:113-116.

39. Gilbert ML Roth AS Friedlander MH. Human corneal steepening by annular keratotomy [Abstract]. Invest Ophthalmol Vis Sci 1989;30(suppl):S186.

40. Amra M Duncker GL Refractive changes after phototherapeutic keratectomy. J Cataract Refract Surg 1997;23: 839-844.

41. Novak KD Koch DD Soper B Padrick T. Changes in computerized videokeratographic measurements induced by artificial tears [Abstract]. Invest Ophthalmol Vis Sci 1994;35(suppl):S2062.

42. Pavlopoulos GP Hom J Feldman ST. The effect of artificial tears on computer-assisted corneal topography in normal eyes and after penetrating keratoplasty. Am J Ophthalmol 1995;119:712-722.

43. Parel J-M Simon G Lowery JA The effect Of wound hydration on central corneal curvature in laser and diamond knife keratotomy [Abstract] Invest Ophthalmol Vis Sci 1990;31(suppl):S479.

44. Dougherty PJ Wellish KL Maloney RK. Excimer laser ablation rate and corneal hydration. Am J Ophthalmol 1994;118:169-176.

45. Dupps WJ. Peripheral stromal expansion and anterior corneal flattening in phototherapeutic keratectomy: an in vitro study in human donor globes [Master's Thesis]. Columbus OH: The Ohio State university; 1995.

46. Dupps WJ Roberts C Schoessler JP. Peripheral lamellar relaxation: a mechanism of induced corneal flattening in PTK and PRK? [Abstract]. Invest Ophthalmol Vis Sci l995;36(suppl):S708.

47. Fahd AK Seitz B Oliveira CBR McDonnell PJ Bryant MR. Effects of phototherapeutic keratectomy on peripheral corneal thickness [Abstract]. Invest Ophthalmol Vis Sci 1996;37(suppl):S568.

48. Maurice DM. Mechanics of the cornea. In: Cavanagh HD ed. The Cornea: Transactions of the World Congress on the Cornea HI. New York NY: Raven Press; 1988:187-193.

49. Jue B Maurice DM. The mechanical properties of the rabbit and human cornea. J Biomech 1986;19:847-853.

50. Roberts C. The cornea is not a piece of plastic. J Refract Surg 2000;16:407-413.

51. Roberts C. Future challenges to aberration-free ablative procedures. J Refract Surg 2000;16:S623-S629.

52. Roberts C Dupps WJ. Corneal biomechanics and their role in corneal ablative procedures. In: MacRae SM Krueger RR Applegate RA eds. Customized Corneal Ablation. Thorofare NJ: SLACK Ine; 2001:109-131.

Thông tin
Thông tin xuất bản

Journal of Refractive Surgery

Tập 17 Số 6

658-669

Thông tin tác giả