Article

PRESCRIBING FOR ASTIGMATISM

DUAL MANAGEMENT OF PRESBYOPIA AND ASTIGMATISM

The art of prescribing contact lenses to correct both astigmatism and presbyopia often involves attention to several factors to achieve visual satisfaction, comfort, and alignment with lifestyle needs. Choices regarding lens material, modality, and design must be thoroughly evaluated (Table 1), keeping in mind a patient’s expectations and ocular history.

TABLE 1 CHOICES TO EVALUATE IN CONTACT LENSES FOR PRESBYOPIA AND ASTIGMATISM
MATERIAL
Soft (Toric) Lens Immediate comfort and ease of adaptation; ability to correct residual astigmatism
Corneal GP Lens Provide optimal optics by correcting corneal astigmatism
Scleral GP Lens Correct corneal astigmatism; provide constant hydration for concurrent ocular surface disease
MODALITY
Multifocal Maintain binocularity and provide clear vision at several distances
Monovision Less visual compromise from glare and halos in low-contrast settings
CORNEAL GP DESIGNS
Translating Multifocal Distinct zones allow for sharp visual quality at specific focal points
Aspheric Multifocal Gradual blend in power allows for focus at wide ranges

What to Consider

A 67-year-old retired female presented for a contact lens fitting to achieve independence from spectacle lens wear. Her previous ocular history was significant for laser-assisted in-situ keratomileusis (LASIK) surgery of the left eye 20 years prior, which allowed for monovision correction (distance OS, near OD). Prior to LASIK, she wore GP corneal lenses and had tried soft lenses but discontinued due to “allergies.” Manifest refraction revealed roughly 1.00D of astigmatism in both eyes; best-corrected visual acuity was 20/20 OD and OS.

Today’s soft multifocal lenses can generally provide satisfactory vision for patients who have refractive astigmatism ≤ 1.00D. In cases in which greater astigmatic correction is needed, soft toric multifocal options are available and may be indicated.

Due to this patient’s history of soft lens intolerance and previous success with corneal GP wear, corneal lenses were ideal; scleral multifocals could also serve as an alternative. GPs provide optimal visual quality because they correct corneal astigmatism and irregularity by forming a tear lens between the cornea and the posterior lens surface.

This patient’s primary goals were to watch TV, play golf, and read without spectacles; she needed correction to achieve clarity at all distances. Multifocal correction was selected over monovision to retain binocularity and to provide full range of vision. This was especially significant when considering her avocations, particularly to preserve depth of focus when golfing.

Multifocal corneal GP lenses are available in aspheric or translating designs. Aspheric designs involve flattening of the posterior curvature from the center toward the periphery to allow for greater plus power. Adequate centration must be achieved to access the full range of powers. Due to the gradual curvature, visual quality can be less crisp compared to translating designs, but accessing intermediate and near powers does not require upward lens movement in downgaze as with translating designs. Significant lid laxity may preclude a translating fit. We selected an aspheric design because our patient did not want to have to adjust her posture for clear vision. CLS