EyeWitness

Winter 2017

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CLSA EyeWitness Winter 2017 21 procedure. Overall, diagnostic fitting can result in improved patient satisfaction and better compliance while giving the prac- titioner greater confidence in the fitting relationship. 2 Assessing a GP Fit Eyelid position of a patient often in- fluences whether a GP should be fit lid attached or interpalpebrally. Lid attached contacts are usually larger in diameter (~9.5mm) and center slight- ly superior with the upper lid covering the top quarter to third of the GP. This is a great option for patients whose up- per eyelid completely covers their su- perior limbus in primary gaze. When the upper eyelid is above the superior limbus, an interpalpebral lens-lid rela- tionship can be achieved. In this case, the positioning of the GP is not influ- enced by the upper eyelid. A smaller diameter GP used (~9.0mm) to pro- mote centration with minimal eyelid involvement. Regardless of diameter, it is important to note the GP position on the cornea as well as the movement (e.g., Lid attached fit, GP riding supe- rior, 2mm movement on blink). GP movement can be quantified similar to a soft lens and will be discussed in more detail in the soft lens section. Fluorescein pattern assessment identifies how closely the base curve of the GP aligns to the curvatures of the cornea. By instilling sodium fluo- rescein (NaFl) to the superior bulbar conjunctiva after the GP is inserted, then using a cobalt blue light and often a yellow Wratten filter, the fitting rela- tionship between the GP and the cen- tral cornea can be determined. If the lens is too steep, excessive pooling will be noted. This is called apical clear- ance (Figure 3). If the lens is too flat, a dark area of central bearing or apical touch will be noted (Figure 4). When the lens curvature almost perfectly matches the curvature of the cornea and a smooth, even lacrimal lens ex- ists between the cornea and GP, this is called apical alignment (Figure 5). Ideally, a lens will fit as close to apical alignment as possible. The midperiphery of the lens is Figure 3 Figure 4 Figure 5

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