Potential Side Effects of Small-Aperture Devices for Irregular Astigmatism
Small-aperture devices (SADs) for treating irregular astigmatism can cause several significant side effects including reduced contrast sensitivity, decreased night vision, visual disturbances like glare and halos, and potential loss of best-corrected visual acuity. 1, 2
Visual Quality Side Effects
Reduced Light Transmission
- Decreased overall brightness/darkened vision due to the reduced aperture size
- Particularly noticeable in low-light conditions
- Can affect patients' ability to function in dimly lit environments
Visual Disturbances
- Glare and halos, especially at night 1
- Starburst effects around light sources
- These symptoms are similar to those seen with other refractive procedures but may be more pronounced due to the aperture restriction
Contrast Sensitivity
- Significant reduction in contrast sensitivity
- Affects ability to distinguish objects from backgrounds, especially in low light
- May impact daily activities like driving at night or reading in dim lighting
Functional Limitations
Night Vision Problems
- Reduced visual acuity in low-light conditions
- Potential difficulty with night driving
- Increased dependence on additional lighting for tasks
Visual Field Restrictions
- Potential narrowing of peripheral visual field
- May affect depth perception and spatial awareness
Optical and Refractive Issues
Induced Astigmatism
- Potential for inducing new or worsening existing irregular astigmatism if device placement is suboptimal 1
- Can result from decentration of the small aperture
Loss of Best-Corrected Visual Acuity (BCVA)
- Risk of permanent reduction in BCVA 1
- May occur due to complications with device placement or tissue response
Adaptation and Comfort Issues
Foreign Body Sensation
- Discomfort or awareness of the implant
- May persist beyond the initial adaptation period
Fluctuating Vision
- Inconsistent visual quality throughout the day
- May be affected by pupil size changes and lighting conditions
Corneal Complications
Corneal Health Issues
- Potential for epithelial problems similar to those seen with other corneal devices
- Risk of dry eye symptoms or exacerbation of existing dry eye 1
- Decreased corneal sensitivity in some cases
Long-term Concerns
- Corneal haze or scarring (early or delayed onset) 1
- Potential for corneal infiltrates or inflammation
Management Considerations
Patient Selection
- Careful screening is essential to identify patients at higher risk for complications
- The American Academy of Ophthalmology recommends thorough evaluation with corneal topography/tomography before any procedure 2
Patient Counseling
- Patients should be informed about the approximately 27.3% rate of unsatisfactory visual outcomes reported in some studies 2
- Realistic expectations about visual improvement must be established
- Patients should understand the potential for night vision problems with any correction method 2
Follow-up Care
- Regular monitoring for complications
- Potential need for removal if side effects are intolerable
Conclusion
Small-aperture devices represent one option in the management of irregular astigmatism, but patients must be carefully selected and counseled about the significant potential side effects. For many patients with irregular astigmatism, alternative options like rigid gas-permeable lenses (which achieve BCVA of 20/30 or better in 93% of patients) or scleral lenses may provide better visual outcomes with fewer side effects 2.