A 72-year-old woman from Mumbai undergoes uncomplicated phacoemulsification and IOL implantation in the right eye for mature cataract. On postoperative day 1, she reports good vision (6/9) but complains of glare and halos around lights, particularly at night. Slit-lamp examination shows the IOL is well-centered in the capsular bag with no visible tilt or decentration. Posterior capsule is clear. Intraocular pressure is 16 mmHg. What is the most likely cause of her symptoms?

Explanation

## Postoperative Glare and Halos: Spherical Aberration ### Clinical Presentation The patient has: - Good visual acuity (6/9) on postoperative day 1 - Glare and halos, especially at night - Well-centered IOL with no tilt or decentration - Clear posterior capsule - Normal intraocular pressure ### Mechanism of Spherical Aberration **Key Point:** Spherical aberration (SA) is an **optical aberration** caused by the difference in refractive power between the center and periphery of a lens. Standard IOLs have positive spherical aberration, which increases with pupil dilation. ### Why Spherical Aberration Causes Glare and Halos 1. **Pupil dilation at night** increases the effective diameter of the IOL. 2. **Peripheral rays** passing through the edge of the IOL are refracted more than central rays. 3. This causes **multiple focal points** instead of a single focal point, creating a halo effect around bright objects. 4. The symptom is **most noticeable in dim lighting** when the pupil is dilated. ### High-Yield Facts **Mnemonic: GLARE = Glare from Lens Aberrations Reduces Evening vision** - **Spherical aberration is inherent** to standard monofocal IOLs and is one of the most common causes of postoperative glare/halos. - **Aspheric IOLs** (negative SA design) reduce spherical aberration and minimize glare. - **Multifocal IOLs** may have increased glare due to multiple focal zones. - **Pupil size is critical**: symptoms worsen with pupil dilation (night driving, dim environments). - **Timing**: SA-related symptoms appear immediately postoperatively, unlike posterior capsular opacification (which develops weeks to months later). ### Differential Diagnosis of Postoperative Glare | Cause | Onset | Posterior Capsule | IOL Position | Cornea | Management | |---|---|---|---|---|---| | **Spherical aberration** | Immediate (POD 1) | Clear | Centered | Clear | Aspheric IOL, pupil dilation exercises | | Posterior capsular opacification | Weeks to months | Opaque/hazy | Centered | Clear | Nd:YAG capsulotomy | | IOL tilt/decentration | Immediate | Clear | Decentered/tilted | Clear | Repositioning surgery if severe | | Corneal edema | Immediate | Clear | Centered | Edematous | Topical hypertonic saline, time | ### Clinical Pearl **Aspheric IOLs** (e.g., Alcon Acrysof IQ, Bausch + Lomb Enhancements) are specifically designed with **negative spherical aberration** to compensate for the eye's natural positive SA, reducing glare and improving contrast sensitivity, especially in low-light conditions. ### Management Options 1. **Reassurance**: Many patients adapt within 2–4 weeks. 2. **Pupil dilation exercises**: Encourage bright-light activities to keep pupils constricted. 3. **Aspheric IOL in fellow eye**: If cataract develops in the left eye, consider an aspheric lens. 4. **Topical alpha-2 agonists** (e.g., brimonidine): May reduce pupil dilation at night. 5. **Surgical repositioning**: Only if IOL is significantly decentered (not the case here).