Advanced Presbyopia (Normal Lower Lid Position) – Segmented Design: Thomas G. Quinn, OD, MS, FAAO
TA was a 43-year-old teacher who expressed interest in bifocal contact lenses. She had worn rigid contact lenses since the age of 14. She reported trying monovision in the past with poor success. She was currently wearing +2.75D readers over her contact lenses for near tasks.
Test Procedures, Fitting/Refitting, Design and Ordering
OD: -2.75 -0.50 x 068 20/20
OS: -3.50 DS 20/20
Add +1.50 OU
OD: 43.87 @ 180/43.87 @ 090
OS: 43.87 @ 170/43.75 @ 080
As the patient was found to be visual sensitive and emphasized the desire for “crisp” near vision, it was decided to pursue translating GP bifocal lenses. External examination revealed a lower lid tangent to the lower limbus, providing the ideal lower lid/cornea relationship for a translating lens design.
As diagnostic lenses were not available, the initial lens design was empirically calculated. The base curve selected was 0.50D flatter than “K”. 43.75D -0.50D = 43.25D (7.80mm) OU
Lens power was adjusted to account for the resulting -0.50D lacrimal lens.
R -2.75 +0.50 = -2.25 D
L -3.50 +0.50 = -3.00 D
A 9.6 mm diameter was selected. The seg height was placed 1.0 mm below the geometrical center of the lens: 9.6 divided by 2 = 4.8 (minus 1.0) = 3.8mm
Lenses Ordered: Tangent Streak Bifocal (Fused Kontacts):
|OD:||7.80||9.6||-2.25/+1.50add||3.8||2 (assume 10º nasal rotation)|
|OS:||7.80||9.6||-3.00/+1.50add||3.8||2 (assume 10º nasal rotation)|
Both lenses positioned on the lower lid, demonstrated little rotation and translated well when gaze was shifted down. The segment line was slightly below the pupil during straight ahead gaze similar to that in photo below.
Patient Consultation and Education
Some time was devoted to instructing TA to move her eyes to down gaze to view near objects, rather than tipping her head down. This was demonstrated by having her hold her head in a straight ahead position while holding and viewing a near card directly in front of her. She was then instructed to hold her head still and slowly lower the card until her vision cleared. She reported clear near vision when the card was lowered to a standard viewing angle.
Since TA had worn GP contact lenses for many years, care and handling was reviewed and full-time wear with her new lenses was permitted. The patient was instructed to return in approximately one week wearing the lenses, at minimum, 4 hours on the day of the visit.
Follow-Up Care/Final Outcome
The patient returned two weeks later reporting clear vision at distance and near. She also reported “these lenses seem to slide around a little more.” Lenses had been in 1.5 hours at the time of the visit, with an average wearing time of 12 hours per day.
6M40cm Over-refraction (6M)
Both lenses continued to display excellent fitting characteristics found at dispensing. No conjunctival injection or corneal staining was evident in either eye.
The over-refraction results were demonstrated. The patient denied any significant change in vision. It was therefore decided to release the patient without any changes to the lenses. She was instructed to return in 12 months for a comprehensive examination.
Discussion/Alternative Management Solutions
Contact lens options for presbyopic patients include single vision distance contact lenses with reading glasses, monovision and multifocal contact lenses.
Since TA had already experienced options 1 and 2 and was not satisfied, a multifocal option was pursued. As the patient had worn GP lenses successfully and GP multifocals are generally thought to provide superior vision than soft multifocals, the final choice was between a translating and simultaneous vision design GP multifocal. The patient’s lower lid position was ideal for a translating lens design and since the patient expressed a desire for “crisp” near vision, a translating design was selected and fit with excellent results.
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