Bilateral phacoemulsification and intraocular lens (IOL) implantation for bilateral corneal ectasia after photorefractive keratectomy (PRK)

1
Bilateral phacoemulsification and intraocular
lens (IOL) implantation for bilateral corneal
ectasia after photorefractive keratectomy (PRK)

• Anita S.Y. Ng, Arthur C.K. Cheng, Srinivas K.
  Rao, Philip T.H. Lam, Dennis S.C. LAM

Department of Ophthalmology Visual Sciences,
The Chinese University of Hong Kong, University
Eye Center, Hong Kong Eye Hospital, 147K, Argyle
Street, Hong Kong, Peoples Republic of China.
2
Purpose

• To 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.

3
Method

• A case report of two eyes of a patient who
  received PRK in both eyes in 1992.
• 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.
• OS 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.

7
Results

• BCVA OD 20/20 (-0.50/-0.75 x 70)
• 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.

8
Results

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

9
Results

• 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.

10
Conclusions

• 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.
• 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
  2004302623-8.
• 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. 2002109651-658.
• Hoffer KJ. Related Articles, Links Intraocular
  lens power calculation for eyes after refractive
  keratotomy. J Refract Surg 199511490-3.
• Wang L, Swami A, Koch DD. Peripheral corneal
  relaxing incisions after excimer laser refractive
  surgery. J Cataract Refract Surg 2004301038-44.