Dysphotopsia is a general term for undesirable visual phenomena that occur in eyes with intraocular lenses (pseudophakic eyes) after cataract surgery 1). It is a major factor reducing patient satisfaction even after uncomplicated surgery.
It is broadly classified into two types: positive dysphotopsia (PD) and negative dysphotopsia (ND) 1).
Initially, many reports were for high-refractive-index hydrophobic acrylic intraocular lenses with square edges 1). However, occurrences have since been confirmed in intraocular lenses of various materials and designs, including silicone and hydrophilic acrylic 1).
Most abnormal photopsias resolve spontaneously or become unnoticeable through neuroadaptation. However, in some patients they persist and may require surgical intervention.
It does not always occur. ND is observed in about 15% of patients on the first postoperative day, but decreases to about 3% after one year without intervention 1). Most cases naturally diminish through neuroadaptation.
Positive Dysphotopsia (PD)
Halo: A ring of light around a light source. Becomes noticeable during night driving.
Starburst: Radial streaks of light emanating from a light source.
Arcs, rings, or flashes of light: Appearing in the central to mid-peripheral visual field.
Ghost image: Perceived as a double image.
Negative Dysphotopsia (ND)
Dark crescent-shaped shadow: An arcuate dark shadow in the temporal mid-peripheral visual field. Perceived as a scotoma or like a “horse blinder” 1).
Curtain-like shadow: Sensation of a dark arc blocking the visual field like a curtain.
Temporal changes: ND tends to diminish over time 1).
PD tends to worsen in environments with a light source, especially at night or in dark places. ND can be perceived in both bright and dark conditions.
There are few objective findings specific to dysphotopsia. Diagnosis is primarily based on the patient’s description of subjective symptoms.
The main causes of dysphotopsia are the optical properties and position of the intraocular lens. Square-edged intraocular lenses, flat anterior surfaces, small optic diameters, and multifocal designs are more likely to produce bothersome optical images 1).
The relationship between intraocular lens design factors and dysphotopsia is shown below.
| Design factors | PD | ND |
|---|---|---|
| Square edge | Increased risk | Increased risk |
| High refractive index | Increased risk | Associated |
| Multifocal design | Increased risk | — |
ND is multifactorial and not as clearly understood as PD.
Multifocal IOLs have a higher frequency of halos, glare, and dysphotopsia compared to monofocal IOLs2). Extended depth of focus (EDF) IOLs have been reported to have significantly fewer dysphotopsias than multifocal IOLs2).
IOLs with square edges, high refractive index, flat anterior surface, and small optic diameter have higher risk1). Multifocal IOLs have more dysphotopsia than monofocal IOLs2), and EDF IOLs are reported to have fewer than multifocal IOLs2).
The diagnosis of dysphotopsia is primarily based on the patient’s subjective symptoms. No consistently reliable objective test has been established.
This is the most important diagnostic step. Confirm the following:
Glare is a phenomenon in which light from outside the line of sight causes discomfort due to abnormalities in the optical system of the eye. Glare disability refers to a decrease in contrast sensitivity caused by glare. Glare testing is used for quantitative assessment of glare disability.
Treatment for abnormal photopsia begins with conservative management. Surgical intervention is considered when symptoms persist and interfere with daily life.
PD Management
Intraocular lens exchange: Exchange for an IOL with low refractive index, round edge, and low surface reflectivity. Exchange to PMMA, silicone, or copolymer IOLs has been reported.
Improvement rate after IOL material change: 76-88% of PD symptoms are reported to improve.
ND Management
Reverse optic capture: The optic is placed anterior to the capsulotomy opening, shifting the illumination gap anteriorly1).
Piggyback intraocular lens: An additional intraocular lens is inserted into the ciliary sulcus to improve ND1).
Haptic placement: Placing the optic-haptic junction inferotemporally has been reported to reduce ND1).
For multifocal intraocular lenses, abnormal photic phenomena such as “waxy” vision, glare, and halos are the most common reasons for explantation1).
If symptoms do not improve after several months, consultation with the attending physician is recommended. For PD, IOL exchange has been reported to improve symptoms in 76–88% of cases. For ND, reverse optic capture or piggyback IOL are effective options1).
The main mechanism of PD is reflection and refraction of light at the edge of the intraocular lens.
Spherical intraocular lenses have positive spherical aberration, causing myopic shift and increased depth of focus when the pupil dilates1). Aspheric intraocular lenses are designed to correct the spherical aberration of the cornea1). Among higher-order aberrations, spherical aberration is often associated with halos, and coma with positive dysphotopsias such as glare and starbursts. However, individual sensitivity varies, and there is not always a one-to-one correspondence.
The main cause of ND is the illumination gap. A band where light does not reach is formed on the retina between the light rays refracted by the optic part of the intraocular lens and the light rays that reach the periphery beyond the outer edge of the optic part.
Reverse optic capture places the optic anterior to the capsulotomy opening, moving the illumination gap forward and theoretically improving ND. Horizontal haptic placement may reduce the illumination gap by illuminating the peripheral retina differently from the optic periphery1).
To reduce PD, manufacturers are implementing measures such as rounding the anterior square edge, reducing edge thickness, leaving edges unpolished, and shifting refractive power from the posterior to the anterior surface. Despite these changes, PD remains a significant postoperative issue. Reports indicate that 76–88% of PD symptoms improve after changing the intraocular lens material, suggesting that optimization of materials and designs will continue.
EDF intraocular lenses have significantly fewer photic phenomena compared to multifocal IOLs and show a visual disturbance profile similar to aspheric monofocal IOLs 2). They are attracting attention as an option that provides good intermediate vision with minimal photic phenomena 2).
Understanding of the mechanism of ND continues to evolve. In addition to the luminance gap, multifactorial pathophysiology including IOL tilt due to capsular contraction and involvement of the central nervous system is becoming clearer. There are also reports of new minimally invasive approaches, such as symptom relief with YAG laser relaxing incisions on the anterior capsule edge.
