Dear Editor

We thank Dr Kwok for his comments[1] on our article.[2]

In our study inadequate suction was generated during LASIK in two eyes. This may possibly be attributed to the excessive conjunctival scarring in these eyes secondary to prior retinal surgery. None of the eyes had undergone multiple retinal surgeries. We could not correlate the failure of development of adequate suction to the size of buckle as inadequate suction was seen in only 2 eyes out of six eyes with 1800 buckle with encirclage.

We agree with Dr Kwok that hansatome microkeratome has only one suction port to hold the conjunctiva. Those microkeratomes that have more than one suction ports might give better suction in eyes with conjunctival scarring. We had measured corneal flap thickness intraoperatively using the Corneo- gage plus (Sonogage Inc, Cleveland, Ohio) ultrasonic pachymeter. This was performed by subtracting the intraoperative corneal stromal bed thickness from the intraoperative total corneal thickness. We agree with Dr Kwok that intraoperative pachymetry can give us a better idea of residual stromal thickness which is an important factor for the development of post -LASIK keratectasia.

References

(1) Kwok AK. LASIK after scleral buckling surgery [electronic response to Sinha et al. LASIK after retinal detachment surgery] bjophthalmol.com 2003 <a href="http://bjo.bmjjournals.com/cgi/eletters/87/5/551#152">http://bjo.bmjjournals.com/cgi/eletters/87/5/551#152

(2) R Sinha, T Dada, L Verma, D B Chaudhury, R Tandon, and R B Vajpayee. LASIK after retinal detachment surgery. Br J Ophthalmol 2003;87:551-553.

Dear Editor

Sinha et al. describing ten eyes of nine patients who had a myopic refractive error and had previously undergone retinal detachment surgery underwent LASIK surgery.[1]

All of them received a scleral buckle and encirclage at least six months before LASIK surgery. The LASIK surgery could be completed in eight eyes but in two eyes it was aborted intraoperatively because of inadequate suction secondary to extensive conjunctival scarring. This report is of interest, as there is hardly any similar information in the literature. Since all the eyes received a scleral buckle and encirclage before, why did the suction only fail in the two eyes? Did they receive multiple retinal detachment surgery before? Did the number of quadrants buckled and the size of the scleral buckle implanted matter? This additional information certainly will shed more light into this clinical problem.

The authors used hansatome microkeratome (Chiron Vision, Claremont, CA, USA) to create a hinged flap. This hansatome has only one suction port to hold the conjunctiva. Maybe those microkeratomes, like the one from Nidek, that have more than one suction ports would give better suction and extra safety especially in these eyes with conjunctival scarring. Inadequate suction can lead to serious complications like thin flap as reported by the authors. The authors used the hansatome head cutting a 180 µm flap and reported a wide range of thickness of the flap from 110 – 170 µm. However, the method of measurement was not reported. Corneal flap thickness can be measured by subtracting the intraoperative corneal bed pachymetry measurement from intraoperative total corneal pachymetry.[2] In addition, intraoperative pachymetry can give us a better idea of ‘residual stromal thickness’, which is particularly important in these eyes that the development of postoperative keratectasia is a real concern. I agree with the authors that other refractive procedures like photorefractive keratectomy are good options in suitable candidates in this scenario.

References

(1) Sinha R, Dada T, Verma L, Chaudhury DB, Tandon R, Vajpayee RB. LASIK after retinal detachment surgery. Br J Ophthalmol 2003;87:551-3.

(2) Gailitis RP, Lagzdins M. Factors that affect corneal flap thickness with the Hansatome microkeratome. J Refract Surg 2002;18:439-43.