LOW ASTIGMATISMCASE: Inferior Decentration
Allison Jussel Zagst OD, MS, FAAO
History
- HPI: A 45 year-old white female with a history of inadequate vision, multiple Rx checks, and acne rosacea. The patient did not wear glasses until her early 40’s but felt that her vision was degrading. She presented wearing progressive lenses.
- CC: Blurry vision at distance and near. She stated that she could “see” but her vision was not as “crisp” as she would like it to be. She also noted that there is often the “memory of an image” around an image. She was interested in contact lenses.
- Modifying factors: Patient is currently taking Accutane.
Examination
- Entering visual acuities:
| Aided DVA: | Unaided NVA: |
| OD 20/20 | OD 20/40 |
| OS 20/20 | OS 20/50 |
| OU 20/ 20 | OU 20/30 |
- Refraction:
OD -0.25 -0.50 x 070, 20/20
OS -0.25 -0.25 x 105, 20/20
ADD: +1.50D
- Slit Lamp Examination:
| Lids/Lashes | Meibomian Gland Dysfunction |
| Cornea | Clear and intact |
| Tear Film | Reduced TBUT |
| Lens | Clear |
- Corneal Topography (Figure 1):
Keratometry: 42.67D/43.43D 42.79D/43.28D
HVID: 12 mm - Dilated Fundus Examination: Retina is intact with no holes or tears
Figure 1
Decision-Making Process
The patient was consulted on all contact lens options: soft, corneal GP, and scleral lenses as well as the option of continuing with glasses. The patient was interested in GP contact lenses to provide the best possible visual acuity. Scleral lenses were suggested as an option to also address her dry eye , likely worsened by Accutane; however, the patient was apprehensive about the price and wanted to start with GP lenses and consider scleral lenses in the future. Higher order aberrations and dry eye were also discussed as further causes of degraded vision.
Fitting and Evaluation
- Diagnostic GP lens fitting
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- GP lenses were selected from the diagnostic fitting set based on corneal topographies:
OD: Base Curve Radius (BCR): 7.85mm; Overall Diameter (OAD): 9.3mm; Power: -2.00DS, ORx: +1.25 -0.25 x 084OS: Base Curve Radius (BCR): 7.76mm, Overall Diameter (OAD): 9.3 mm, Power: -2.00DS, ORx: +0.75 -0.50 x 119
- GP lenses were selected from the diagnostic fitting set based on corneal topographies:
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- Both lenses fit mildly steep w/ mild dimple veiling, were inferiorly decentered with poor lid attachment, and had good edge clearance 360˚
- The plan was to increase the overall diameter (OAD) of the lenses to 9.6 mm to increase lid attachment and include the spherical equivalent over-refraction.
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- First dispense
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- The lenses were dispensed OU
OD: 20/20 ORx: Plano
OS: 20/25 ORx: +0.50DS 20/20 - Both lenses were better centered, demonstrated an alignment fit, and showed adequate movement
- Plan: Trial lenses for one week and return to the clinic for a follow-up visit.
- The lenses were dispensed OU
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- First follow-up visit
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- Patient noted blurry vision at distance, especially while driving at night and discomfort with lenses.
- Lenses on eye:
OD: 20/20- ORx: +0.25 DS 20/20
OS: 20/20- ORx: +0.50 DS 20/20
OU: 20/20 - Lens-to-cornea fitting relationship:
OD: Mild pooling centrally, mild inferior decentration, and poor lid attachment
OS: Mild inferior nasal decentration - Plan: Increase lens diameter to 9.8mm OU, flatten BCR OD by 0.50D, include over-refraction OU
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- Second dispense
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- Lenses dispensed OU
OD: 20/20-3
OS: 20/20-2OU: 20/20 - Lenses were better lid attached, centered well, and had an alignment fitting
- Plan: Wear lenses for one week and return to the clinic wearing lenses.
- Lenses dispensed OU
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- Second follow-up visit
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- Patient returned with some slight discomfort wearing the lenses and noted difficulty with night driving
- Over-refraction over lenses
OD: +0.25 -0.75 x 083
OS: +0.50 -0.75 x 117 - Plan: Order lenses with over-refraction and increase diameter to facilitate improved comfort
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- Third dispense
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- Lens Parameters:
OD: BCR: 7.85mm; OAD: 10.0mm; Power: -0.62 -0.75 x 083
OS: BCR: 7.67mm; OAD: 10.0mm; Power: -1.00 -0.75 x 117 - Visual acuity
OD: 20/20, ORx: PL
OS: 20/20, ORx: PL - Lenses were lid attached, centered well, had good movement, and an alignment NaFl pattern
- Plan: Finalize lenses. Patient reported improved vision and comfort with new lenses.
- Lens Parameters:
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Clinical Pearls
- A larger OAD is helpful in aiding in a lid attached fit
- A flat lens may decenter so centering the lens with your finger and assessing fluorescein pattern is a useful evaluation tool!