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The incidence of night vision problems resulting from LASIK or PRK refractive surgery for myopia can be minimised if accurate preoperative pupil measurements are taken and the ablation is tailored accordingly, says a French ophthalmologist. Jean-Jacques Saragoussi MD, told delegates at the annual congress of the French Implant and Refractive Surgery Association (SAFIR) that careful preoperative assessment and rigorous surgical procedures held the key to better refractive outcomes in LASIK and PRK treatments. Dr Saragoussi presented the results of a recent patient satisfaction survey carried out at Clinique de la Vision in Paris, one of the primary laser eye surgery centres in the French capital. The retrospective study included objective and subjective assessments of 219 consecutive eyes (111 patients) operated on with LASIK or PRK over a 10-month period. The patients included 50 men and 61 women, with ages ranging from 22 to 50 years and a mean age of 33 years. The patients had preoperative errors ranging from -1D to -9.25D with an average preoperative manifest spherical equivalent of -4.52D (+-1.84). LASIK surgery was performed on 200 eyes (91.3%) using the Technolas 217z excimer laser and Hansatome microkeratome. Of the remaining 19 eyes (8.7%), PRK was the preferred option, either owing to contraindications for LASIK such as large pupil size, weak pachymetry, or the choice of the patient. In an effort to limit known night vision complications, the optical zone for all surgeries was greater than 5mm and the transition zone was larger than the scotopic pupil size. When an ablation is smaller than the pupil, a differential focus of light through the optical zone and untreated surrounds are created, leading to problems of halo and glare, explained Dr Saragoussi. "In refractive surgery it is critically important to accurately establish the likely range of the pupil diameters, especially with scotopic illumination, when the pupil is at its largest. The ablation needs to cover the whole of the dilated pupil," he advised Preoperative central corneal thickness also had to be sufficient to ensure at least 250 microns in the posterior stroma after making the corneal flap in LASIK procedures, said Dr Saragoussi. The median preoperative best-corrected visual acuity (BCVA) was 0.85 (range 0.2-1.0) in the monocular group and 1.02 (range 0.7-1.2) in the binocular group. Patients had a mean postoperative spherical equivalent of -0.08 D (range from -2.37-+0.87 D). In terms of subjective data, 90 myopic patients (81%) responded to a follow-up questionnaire no later than six months after their surgery. More than half (58%) of patients reported a better quality of daytime vision, one third (33%) said it was unchanged and nine perecent said it was worse after surgery. One third of patients (34%) believed their postoperative night vision had improved, 39% reported no change and 26% said they felt it had deteriorated. However when asked if they experienced problems with night vision, almost half (47%) said they did experience some difficulties, 51% said they did not and 2% didn’t know. Some 29.5% said they experienced more problems with night driving postoperatively, 46% reported no change and 23% said they had less difficulty. Of 42 patients who reported problems with night vision, 69% cited halos, 35% glare and 35% scatter. A little more than one third of these 42 patients suffered from just one complaint, 55% suffered from two and 7% all three. Of the 90 patients, 79% said they were very satisfied overall with the outcome of their surgery, 19% said they were quite satisfied, and 2% described themselves as satisfied. None of the patients described themselves as dissatisfied with the overall result and 98% said they would recommend the procedure to others. Looking at the overall data, Dr Saragoussi said that the study helped to pinpoint certain risk factors for night vision problems induced by refractive surgery. Patients with pre-operative myopia greater than -4.50D seemed to pose a greater risk of experiencing night vision problems, although other factors such as the depth of the ablation, the size of the treatment zone and post-operative pachymetry also played a role. "In terms of surgical technique, I would stress the importance of keeping the ablation treatment zone larger than the diameter of the scotopic pupil size if you want to avoid subsequent problems with the quality of night vision for your patients," he said. Dr Saragoussi said while night vision problems were frequent and were clearly associated with higher levels of preoperative myopia and low keratometry values post-operatively, these factors did not impinge on the subjective degree of overall satisfaction reported by patients after surgery. Jean-Jacques Saragoussi, MD, |
