Effect of preoperative pupil measurements on glare, halos, and visual function after photoastigmatic refractive keratectomy.
OBJECTIVE
To prospectively assess the effect of preoperative variables such as pupil size on glare, halos, and visual function after photoastigmatic refractive keratectomy (PARK).


METHODS
Department of Ophthalmology, Stanford University School of Medicine, Stanford, California, USA.


METHODS
Ninety-three eyes had PARK for primary compound myopic astigmatism. Preoperative pupil diameters were measured under scotopic and photopic illuminance conditions. Postoperatively, patients were evaluated at 1, 3, 6, 9, 12, 18, and 24 months. A regression model was performed to evaluate the predictive value of assessing preoperative variables such as pupil diameter on the development of glare and halos, contrast sensitivity, and best spectacle-corrected visual acuity (BSCVA) under scotopic, photopic, and glare conditions.


RESULTS
The greater magnitude loss of BSCVA under scotopic conditions in the early postoperative period as well as the slower recovery to preoperative levels in eyes with larger scotopic pupil diameters were not statistically significant (P >.05). An increase in symptoms of glare was related more to the attempted level of spherical equivalent (SE) correction than to the pupil size during the first 12 postoperative months (P <.01). The photoablation dimensions as determined by the attempted level of astigmatic correction may result in decreases in the glare BSCVA up to 12 months after PARK (P =.03). At the 2 year follow-up, pupil diameter under both scotopic and photopic illuminance conditions was not predictive of any of the measured outcomes variables.


CONCLUSIONS
An assessment of preoperative pupil size and the attempted level of both SE and astigmatic correction may be useful in identifying patients at risk of developing symptoms or declines in visual performance after PARK. However, follow-up studies are indicated to identify variables predictive of poor visual outcomes following excimer laser refractive surgery.
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Department of Ophthalmology, Stanford University School of Medicine, Stanford, California 94305, USA.
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D000221:Adaptation, Ocular; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology* / Q000601:surgery; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D019466:Glare; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology* / Q000601:surgery; D018903:Photorefractive Keratectomy; D011300:Preoperative Care; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology*; D014786:Vision Disorders / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology*