![]() Theory points to increased postoperative higher-order wavefront aberrations. Patients with higher levels of correction have a higher probability of nighttime visual complaints. If the patient is even mildly myopic and/or astigmatic, the residual ametropia coupled with a nighttime myopic shift can certainly elicit complaints. Halos are basically myopic, blurred circles surrounding point sources of light. Utilizing four separate excimer laser platforms over the past 4 years, it is clear to me that the following (in descending order) are the most likely causes of chronic postoperative night vision complaints: It is far easier to attribute a patient's subjective visual complaint to obvious explanations (large pupil, smaller optical zone) than to a more complex and subtle explanation. Incidence of subjective night vision complaints due to larger optical zones does not appear to be appreciably less compared to that with smaller optical zones (6.0 mm) in patients matched for pupil size and level of myopic correction. Increased optical zones are extremely inefficient, removing up to 40% more corneal tissue.ģ. Variable optical zones result in multiple nomograms and decrease the probability of achieving emmetropia.Ģ. I carefully implemented recommendations on matching optical zone to pupil size, only to be surprised with the following clinical conclusions:ġ. My experience using larger ablation zones matched to scotopic pupil size has led me to the following findings.Īs a refractive surgeon, I believed much of what our fellow ophthalmologists said about pupil size. It would be unwise, however, to perform higher volume/deeper ablations without well-designed clinical investigations into the long-term effects and potential benefits of such off-label treatments. For many highly myopic patients who lack adequate preoperative corneal thickness for LASIK, PRK/LASEK may be substituted for deeper (higher volume) ablations. ![]() Those using modern excimer lasers have been able to expand optical zones and remove greater tissue volume in order to match the optical zone size to the scotopic pupil. ![]() Unfortunately, wavefront technology only measures physical aberrations, not patient perceptions which may be affected by the Stiles-Crawford effect and other factors. Furthermore, surgeons are now using wavefront devices to support patients' complaints of postoperative night vision symptoms. Refractive surgeons bolster this surgical argument with case reports of patients who have large pupils and severely debilitated night vision after undergoing LASIK or PRK with optical zones smaller than their scotopic pupil. I believe it is a gross mistake, however, to draw major conclusions from studies that utilized first-generation excimer laser technology and techniques. This theory of increasing optical zone size to minimize subjective complaints of night vision does have a scientific basis. This surgical plan (optical zone size = scotopic pupil size) grows out of conclusions drawn from PRK studies in the early 1990s that noted that patients with 6-mm optical zones logged fewer subjective halo and glare complaints than patients with 4- to 5-mm optical zones. For example, if a patient with a refractive error of -7.0 D has a 7.5-mm pupil and desires LASIK or PRK, the surgeon should try to match the optical zone to the scotopic pupil (7.5 mm). Some believe that the LASIK treatment optical zone must at least match that of the scotopic pupil. How important is pupil size in modern keratorefractive surgery? Physicians are taking two basic positions. The incidence of anisocoria was no different on the basis of eye color.A debate is raging within the electronic forums of refractive surgery that I would like to address. The incidence of anisocoria was found to be 21%. A statistically significant difference in pupil size was found between blue and brown eyes. There was no statistical difference between right and left eyes. The mean (+/- SD) pupil size was 3.8 +/- 0.8 mm. Pupil size and color were obtained from photographs. Eight-eight healthy newborns were evaluated. Additionally, the normal range of infant pupil size is not well defined. N2 - The incidence of anisocoria in the newborn period is not well described. ![]() JF - Archives of ophthalmology (Chicago, Ill. T1 - Normal pupil size and anisocoria in newborn infants. ![]()
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