Article
Excimer-laser phototherapeutic keratectomy for granular and lattice corneal dystrophy: a comparative study
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Published: | September 22, 2004 |
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Outline
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Objective
To compare the visual and refractive outcome after excimer laser phototherapeutic keratectomy (o-PTK) for superficial corneal opacities in granular (GRAND) and lattice (LATTID) dystrophy.
Methods
O-PTK was performed in 62 eyes of 40 patients (50x GRAND, 12x LATTID) after epithelial debridement and pannectomy using MEL 60/70 excimer laser (Carl Zeiss-Meditec). The number of laser pulses (median) were 1578 and 1516, the intended depths of excimer laser ablation were 50μm and 35μm for GRAND and LATTID, respectively, and diameter of the treatment zone was either 6.0mm or 6.5mm. Data regarding pre- and postoperative best-corrected visual acuity (BCVA), changes in spherical equivalent (SE), astigmatism and central power (Zeiss keratometry), and regularity of corneal topography (TMS-1) were analyzed. Recurrence, if any, was noted during a mean follow-up of 3.0 ± 2.7 (maximum 10) years.
Results
The BCVA improved in 79% of eyes in GRAND and 62% of eyes in LATTID. The SE increased by a median of 1.0 diopter (D) for GRAND and 0.5D for LATTID. The keratometric central power decreased by a median of 1.6D for GRAND and 0.7D for LATTID. There was no significant change of keratometric astigmatism both in GRAND and LATTID. The proportion of regular/mild irregular keratometry mires increased (39% vs. 67% for GRAND and 0% vs. 50% for LATTID). In GRAND, the SRI/SAI (surface regularity index/surface asymmetry index) decreased significantly from 2.14/2.24 preoperatively to 1.31/0.80 postoperatively (P=0.006/P=0.01). In contrast, decrease of SRI/SAI did not reach statistical significance in LATTID (from 1.97/1.65 preoperatively to 1.35/1.16 postoperatively). Recurrences were observed in 20% of GRAND and 17% of LATTID.
Conclusions
Our results suggest that o-PTK may be tried in all patients with superficially accentuated opacities or recurrent erosions in GRAND and LATTID before going for a more invasive procedure, such as lamellar or even penetrating keratoplasty. However, outcome is better in GRAND.