PRESBYOPIA: Pre-Testing for Presbyopia
Roxanne Achong-Coan OD, FAAO, FIAMOC, FSLS
Introduction
The first step to success in fitting a presbyopic patient is patient selection. Certain patients are more likely to succeed with multifocal contact lenses. These patients include patients who have active lifestyles, multitaskers, and patients who dislike wearing glasses or readers with their current contact lenses, which describes our current patients. Patients with critical visual demands who are amblyopic and have poor tear film and volume are not ideal candidates for presbyopia correction. Patients who are moderate-to-high myopes or hyperopes also tend to be more successful than patients who are emmetropic as these patients are accustomed to having excellent vision.
Test Procedures
The following tests are recommended in the preliminary testing:
- Patient Information and History
- Basic patient demographics: age, gender, and occupation.
- Medical and ocular history: any current eye conditions (i.e., dry eye syndrome), allergies, previous contact lens wear experience.
- History of ocular surgery – especially cosmetic surgery to the eyelids.
- Visual needs, goals, and expectations: activities that require clear near and distance vision (i.e., reading, driving).
- Medications – hormone replacement therapy, antihistamines, anticholinergics, antidepressants, and anti-anxiety drugs, which can affect the tear film and volume
- Any history of contact lens use, and what was successful and not successful.
- Visual Acuity Assessment
- The distance visual acuity test should be measured using a standard Snellen chart.
- The near visual acuity test is checked at 14-16 inches using an appropriate near vision chart.
- Refraction and Prescription Determination
- A refraction should be performed to determine the current refractive error (sphere, cylinder, axis) and obtain the best-corrected visual acuity (BCVA) with glasses.
- Bifocal power is determined based on refraction and near-vision demands.
- Corneal Evaluation and Contact Lens Fit
- The corneal curvature is measured by using keratometry or corneal topography to assess corneal shape.
- Corneal diameter for appropriate contact lens diameter determination (horizontal visible iris diameter).
- The ocular surface must also be examined to determine whether the patient can wear contact lenses successfully by assessing the quality and quantity of tear film. Tear break-up time and aqueous tear production should be measured as this can affect lens wetting and the length of time the patient can wear contact lenses comfortably. In a study by du Toit et al., 28% of presbyopes had dry eyes before contact lens wear, but 68% reported dryness after wearing contact lenses for six months.2 Corneal staining should not be present as a poor ocular surface will affect the comfort and wetting of the contact lens.
- Physical anatomy of the eye
- Corneal diameter: Horizontal visible iris diameters, vertical palpebral fissure size, and pupil size in dim and normal illumination should also be measured.
- Pupil size: Patients with large pupils will experience more glare and ghosting with a simultaneous design in dim light.
- Pterygia and pinguecula can also develop, disrupting the ocular surface.
- The eyelid also becomes more flaccid over time, which could be problematic with translating gas permeable bifocals.
- Papillary hypertrophy on the upper lid should also be absent which could affect contact lens movement.
- Position of eyelid: Patients with a lower lid inferior to the lower limbus will not be a good candidate for a translating design due to lack of alignment of truncation to the lid.3
- Ocular Dominance
Multifocal contact lens designs require the eye care practitioner to determine the patient’s dominant eye. Two methods determine ocular dominance:
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- Sighting dominance: The patient views the 20/30 line on the eye chart binocularly. The patient then makes a “triangle” with both hands and is told to look through the triangle with outstretched arms, then to close the right eye and ask if they can see the 20/30 line on the eye chart. The eye that the patient is using to see the chart is the dominant eye. The technician or doctor can verify this by checking to see which eye the patient is using to view the chart.
- Sensory dominance: Can be checked by holding a loose trial lens in front of each eye separately. The patient will tell the examiner which view is less blurry. The eye with the lens in front of it will be the non-dominant eye. This is the preferred method of testing.
- Another method to determine eye dominance is to ask the patient which eye they would use to look through when using a viewfinder on a camera. The eye they state that they use will be their dominant eye.
Sources
- Bennett ES, Potter RT, Watanabe RK, Schachter S. Preliminary Evaluation. In Bennett ES, Henry VA. Clinical Manual of Contact Lenses (5th Ed.). Philadelphia, Wolters Kluwer. 2020:2-35.
- Du Toit R, Situ P, Simpson T, Fonn D. The effects of six months of contact lens wear on the tear film, ocular surfaces, and symptoms of presbyopes. Optom Vis Sci 2001;78(6):455-462.
- Bennett ES, Henry VA, Richdale K, Benoit DP. Multifocal Contact Lenses. In Bennett ES, Henry VA. Clinical Manual of Contact Lenses (5th Ed.). Philadelphia, Wolters Kluwer. 2020:440-491.