After the manifest refraction (but before dilating eye drops are administered), the external and anterior segment examinations are performed. Specific attention should be given to the pupillary examination. The pupil size should be evaluated in bright room light and under dim illumination, and the surgeon should look for an afferent pupillary defect. Various techniques are available for measuring pupil size in dim illumination, including use of a near card with pupil sizes on the edge (with the patient fixating at distance), or a pupillometer. The dim-light measurement should be taken using an amount of light entering the eye that closely approximates the amount entering during normal nighttime activities, such as night driving; it should not necessarily be done under completely dark conditions.
Pupil measurements should be standardized as much as possible. Measuring the lowlight pupil diameter preoperatively and using that measurement to direct surgery remains a controversial approach. Conventional wisdom suggests that the optical zone should be larger than the pupil diameter to minimize vision disturbances such as glare and halos. Recent evidence, however, does not support an association between preoperative pupil size and an increased incidence of either glare or halo concerns 1 year postoperatively. It is not clear, therefore, that pupil size can be used to predict which patients are more likely to have such symptoms. However, a thorough and documented discussion with the patient is required. The size of the effective optical zone—which is related to the ablation profile and the level of refractive error—may be more important in minimizing visual adverse effects than is the low-light pupil diameter.
When asked, patients often note that they had glare under dim-light conditions even before undergoing refractive surgery. Thus, it is helpful for patients to become aware of their glare and halo symptoms preoperatively, as this knowledge may minimize postoperative concerns or misunderstanding.
Chan A, Manche EE. Effect of preoperative pupil size on quality of vision after wavefront-guided LASIK. Ophthalmology. 2011;118(4):736–741.
Edwards JD, Burka JM, Bower KS, Stutzman RD, Sediq DA, Rabin JC. Effect of brimonidine tartrate 0.15% on night-vision difficulty and contrast testing after refractive surgery. J Cataract Refract Surg. 2008;34(9):1538–1541.
Pop M, Payette Y. Risk factors for night vision complaints after LASIK for myopia. Ophthalmology. 2004;111(1):3–10.
Schallhorn SC, Kaupp SE, Tanzer DJ, Tidwell J, Laurent J, Bourque LB. Pupil size and quality of vision after LASIK. Ophthalmology. 2003;110(8):1606–1614.
Schmidt GW, Yoon M, McGwin G, Lee PP, McLeod SD. Evaluation of the relationship between ablation diameter, pupil size, and visual function with vision-specific quality-of-life measures after laser in situ keratomileusis. Arch Ophthalmol. 2007;125(8):1037–1042.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.