GP Fitting Case 1 - Discussion Item 5

After reading the Patient History, read the Discussion Items below. To test your understanding of this case, click on the word "select" to read the reasoning behind each choice.

Patient History: 16 y/o female student has never worn contact lenses. She plays no extra curricular sports, and her mother wears GP lenses. No contraindications for lens wear.

Spectacle Rx	OD -2.00 -0.75 x 180 OS -2.25 -1.00 x 180
Corneal Measurements	OD 43.50/44.25 @ 90 OS 43.25/44.25 @ 90
Ocular Measurements (OU)
Corneal diameter	11.5mm
Pupil	4.0mm
Fissure width	10.5mm

Discussion Item 5: Based on the performance of this fluorescein pattern, what changes would you employ?

a)	Larger diameter select
b)	Smaller diameter select
c)	Steeper base curve select
d)	Flatter base curve select
e)	No change select
Go to Discussion Item 6 >>

Spectacle Rx	OD -2.00 -0.75 x 180 OS -2.25 -1.00 x 180
Corneal Measurements	OD 43.50/44.25 @ 90 OS 43.25/44.25 @ 90
Ocular Measurements (OU)
Corneal diameter	11.5mm
Pupil	4.0mm
Fissure width	10.5mm


a) A larger diameter will make the lens even steeper based on increased sagittal depth. Note how much fluorescein is pooled centrally, accompanied by excessive mid-peripheral bearing. If a larger diameter were chosen, the base curve would have to be significantly flatter than it presently is, possibly by 1-2 diopters. back

Spectacle Rx	OD -2.00 -0.75 x 180 OS -2.25 -1.00 x 180
Corneal Measurements	OD 43.50/44.25 @ 90 OS 43.25/44.25 @ 90
Ocular Measurements (OU)
Corneal diameter	11.5mm
Pupil	4.0mm
Fissure width	10.5mm


b) A smaller lens would loosen the fit. In this case the lens is already relatively small in comparison to the horizontal iris diameter. Thus, decreasing lens diameter would likely cause intermittent flare and halos as the lens moves with the blink. Smaller is not the best choice here. back

Spectacle Rx	OD -2.00 -0.75 x 180 OS -2.25 -1.00 x 180
Corneal Measurements	OD 43.50/44.25 @ 90 OS 43.25/44.25 @ 90
Ocular Measurements (OU)
Corneal diameter	11.5mm
Pupil	4.0mm
Fissure width	10.5mm


c) A steeper base curve would create more fluorescein pooling and potentially cause physiological problems relating to decreased tear exchange underneath the lens. back

Spectacle Rx	OD -2.00 -0.75 x 180 OS -2.25 -1.00 x 180
Corneal Measurements	OD 43.50/44.25 @ 90 OS 43.25/44.25 @ 90
Ocular Measurements (OU)
Corneal diameter	11.5mm
Pupil	4.0mm
Fissure width	10.5mm


d) Flattening the base curve is the desirable change in this case. Tip: If making changes by altering base curve, alter at least 0.50D (0.10mm) for a significant impact. back

Spectacle Rx	OD -2.00 -0.75 x 180 OS -2.25 -1.00 x 180
Corneal Measurements	OD 43.50/44.25 @ 90 OS 43.25/44.25 @ 90
Ocular Measurements (OU)
Corneal diameter	11.5mm
Pupil	4.0mm
Fissure width	10.5mm


e) While the patient initially may think this lens is comfortable because it doesn't move, wearing it long term could cause corneal health problems because of the lack of tear exchange. back

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This page was last updated Thursday, April 24, 2008.

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