1. Bilateral phacoemulsification and intraocular lens (IOL) implantation for bilateral corneal ectasia after photorefractive keratectomy (PRK) Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, University Eye Center, Hong Kong Eye Hospital, 147K, Argyle Street, Hong Kong, People’s Republic of China.

2. Purpose To report the occurrence of bilateral corneal ectasia after PRKTo report the occurrence of bilateral corneal ectasia after PRK To discuss the methods of IOL power calculation and the phacoemulsification surgical outcomes in these eyes.To discuss the methods of IOL power calculation and the phacoemulsification surgical outcomes in these eyes.

3. Method A case report of two eyes of a patient who received PRK in both eyes in 1992.A case report of two eyes of a patient who received PRK in both eyes in 1992. History:History: –presented with progressive blurred vision in 2002. –BCVA: OD: 20/30 (-5.0/-1.75x75), OS: CF –Bilateal nuclear sclerosis –Corneal topography: irregular astigmatism with the steepest zone located inferotemporally suggestive of keratectasia, more marked on the left (figures 1a &1b).

4. Method figure 1a

5. Method figure 1b

6. Method Had consecutive phacoemulsification and IOL implantations.Had consecutive phacoemulsification and IOL implantations. OS: Gaussian optic method (contact lens refraction was not possible due to poor visual acuity). Target refraction = -2.0DOS: Gaussian optic method (contact lens refraction was not possible due to poor visual acuity). Target refraction = -2.0D OD: Contact lens method, target refraction -0.75D Limbal relaxing incision with a 600  m diamond knife centered at 332 deg with an arc length of 90 deg was performed at the same setting.OD: Contact lens method, target refraction -0.75D Limbal relaxing incision with a 600  m diamond knife centered at 332 deg with an arc length of 90 deg was performed at the same setting.

7. Results BCVA: OD: 20/20 (-0.50/-0.75 x 70)BCVA: OD: 20/20 (-0.50/-0.75 x 70) OS: 20/30 (-2.25/-1.25 x 115) OS: 20/30 (-2.25/-1.25 x 115) Satisfactory accuracy in determining the corneal power was achieved with both Gaussian optics method and contact lens methods, though both methods showed a slight overestimation of the corneal power.Satisfactory accuracy in determining the corneal power was achieved with both Gaussian optics method and contact lens methods, though both methods showed a slight overestimation of the corneal power.

8. Results The corneal topographic examinations have not changed during the3-year follow-up period.The corneal topographic examinations have not changed during the3-year follow-up period. LRI has corrected the astigmatism on the right eye.LRI has corrected the astigmatism on the right eye.

9. We hypothesized that weakening in the peripheral cornea in our patient with ectasia might slow down the progression of central corneal changes.We hypothesized that weakening in the peripheral cornea in our patient with ectasia might slow down the progression of central corneal changes. Longer-term follow up and larger patient group are needed to study this further.Longer-term follow up and larger patient group are needed to study this further. Results

10. Conclusions We report the uncommon occurrence of bilateral keratectasia after PRK in a patient.We report the uncommon occurrence of bilateral keratectasia after PRK in a patient. Both the Gaussian optics formula and contact lens methods for IOL calculation worked well.Both the Gaussian optics formula and contact lens methods for IOL calculation worked well. We also used a LRI in one eye during surgery. The effects of such surgical procedure on the long-term progression of the corneal ectasia however, remain to be seen.We also used a LRI in one eye during surgery. The effects of such surgical procedure on the long-term progression of the corneal ectasia however, remain to be seen.

11. References Rao SK, Srinivasan B, Sitalakshmi G, Padmanabhan P. Photorefractive keratectomy versus laser in situ keratomileusis to prevent keratectasia after corneal ablation. J Cataract Refract Surg 2004;30:2623-8. 1. Rao SK, Srinivasan B, Sitalakshmi G, Padmanabhan P. Photorefractive keratectomy versus laser in situ keratomileusis to prevent keratectasia after corneal ablation. J Cataract Refract Surg 2004;30:2623-8. 2.Hamed AM, Wang L, Misra M, Koch DD. A comparative analysis of five methods of determining corneal refractive power in eyes that have undergone myopic laser in situ keratomileusis. Ophthalmology. 2002;109:651-658. 3. Hoffer KJ. Related Articles, Links Intraocular lens power calculation for eyes after refractive keratotomy. J Refract Surg 1995;11:490-3. 4.Wang L, Swami A, Koch DD. Peripheral corneal relaxing incisions after excimer laser refractive surgery. J Cataract Refract Surg 2004;30:1038-44.