![]() The aforementioned factors apply to a well-focused eye. In dim light conditions, the detrimental effects of aberrations are outweighed by the dramatic decline in retinal contrast sensitivity. Consequently, under mesopic conditions the ideal pupil size increases to about 6 mm. At lower light levels, this change in the signal-to-noise ratio due to photon noise is known as the deVries-Rose law, in which the change in retinal image quality is the square root of change in retinal illuminance. 5 Under dim illumination and with significant miosis, however, if retinal illuminance declines below 100 trolands (a troland is a measure of the angular flux density of light incident upon the retina 6), quantal fluctuations change the tradeoff between diffraction and aberrations because photon noise greatly elevates the retinal neural contrast threshold. In an eye with HOAs (B), retinal image quality degrades with larger pupils owing to the negative impact of HOAs on the retinal point spread function.Īt photopic light levels, the decrease in retinal illuminance produced by constricting the pupil with strong miotics has no effect on vision because the retinal neural contrast threshold changes proportionately to background illumination (a relationship known as Weber’s law). In an eye with no HOAs (A), the quality of the retinal point spread image worsens with smaller pupils owing to the negative impact of diffraction. 1-3 This optimal pupil size can be even smaller for highly aberrated eyes (eg, those with keratoconus or a history of radial keratotomy or LASIK). For normal, well-focused eyes with an average level of HOAs, this interplay generally results in an optimum photopic pupil size of somewhere between 2 and 3 mm vis-à-vis visual acuity and retinal image quality. In aberrated eyes, however, contrast decreases with pupillary dilation because of the impact of aberrations on the retinal point spread function (Figure 1). In eyes with no HOAs, retinal image quality increases proportionately to pupillary diameter owing to increases in the diffraction bandwidth. UNDERLYING FACTORSįor a well-focused eye (defocus = 0 D), the optical impact of pupillary diameter is modulated by the competing negative effects of diffraction with smaller pupils and the blur generated by optical aberrations with larger pupils. This article attempts to provide a framework that will help eye care practitioners to understand pupillary modulation more fully and evaluate the benefits and compromises involved in pupillary modulation during a person’s typical day. The pupillary diameter to optimize distance, intermediate, or near vision can differ because it is affected by a number of determining factors, including retinal illuminance, diffraction, lower-order aberrations (LOAs ie, defocus), and higher-order aberrations (HOAs). Studies of visual performance when the entrance pupil is artificially modified by viewing through small apertures speak directly to the original query: What is the optimal pupil size? As this article explains, the answer to this question is that it depends. Psychophysical studies suggest that, for a well-focused eye, pupil size iterates to whatever achieves the best visual acuity, 1 grating detection, 2 and retinal image quality 3 for viewing objects at various levels of environmental light. This new approach to presbyopia was heralded by the recent first-in-class FDA approval of Vuity (pilocarpine HCl ophthalmic solution 1.25%, Allergan) and affirmative decision on the premarket approval application for the IC-8 small-aperture IOL (AcuFocus), both for the treatment of presbyopia.Ĭhanges in pupillary diameter are highly dynamic they are influenced by accommodative effort, lighting, refractive error, emotional state, age, and other factors. Today, the subject has practical implications given the number of pupil-modulating drops and small-aperture IOLs in development to treat presbyopia. Perspectives On Prevalence, Gaps, And Management Of MGDĬonsiderations of optimal pupil size used to be a largely intellectual exercise. Using AcrySof ® IQ PanOptix ® and Vivity™ in Your Practice Pearls From the Experts: Part 3 Administration Techniques Strategies for Removing Subincisional Cortex The Benefits of Combining MD and OD Practices Phacoemulsification After Pars Plana Vitrectomy: Cataract Surgery Concepts and Pearls When All Hell Breaks Loose: Zonular Dialysis and the Placement of a Synergy IOLģ0-Gauge Needle Levitation of a Dropped IOL Traumatic Flap Dislocation After Laser Vision Correctionįour-Incision Phaco Chop and Phaco Complications ![]() Pearls for Keratoconus Screening and Treatment ![]()
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