scleral lenses correct keratoconus | pellucid marginal degeneration

CASE STUDY: Pellucid Marginal Degeneration / Keratoconus
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	This case study illustrates how Biometric Scleral LensesTM addressed a specific patient's vision problems due to Pellucid Marginal Degeneration and Keratoconus.
	The patient is a 26-year old man with a history of keratoconus. Manifest refraction OD:-2.50 -3.50 x 100 20/25 OS:-2.75 -4.50 x 097 20/30 Pellucid marginal degeneration is similar to the other corneal thinning disorder, keratoconus. Patients typically develop high irregular astigmatism that cannot be fully corrected with eyeglasses or soft contact lenses.
Corneal Topography
		Corneal topography shows the large inferior area of steepening and the central bowtie pattern of irregular astigmatism.
OCT Pachymetry
		Optical Coherence Pachymetry plots a map of corneal thickness. The hotter colors indicate thinning. In this case, the thinning corresponds to the location of the corneal steepening evident on the corneal topography.
OCT Scan Axis 180
		An OCT scan through the central cornea in the horizontal meridian appears normal and symmetrical.
CT Scan Axis 90
		When the OCT scan is taken through the steep section of the cornea, the steeper area can be readily appreciated. The lower cornea is on the left, and the upper cornea is on the right. Notice how much flatter the upper cornea is compared to the lower cornea.
Retinal Spot Diagram
		The result is that light is not focused inside the eye.
HOA Point Spread Function
		Even with glasses, this is how a point source of light might appear in dim light. The extent of the smeared image is quite large.
Start of Design Process
		Design of the lens begins as detailed measurements are taken of the cornea and sclera.
Scleral Lens Apical Clearance
		The result is a lens that is very comfortable and clears the corneal apex.
Fluorescein Pattern
		The fluorescein pattern reveals the thicker and thinner areas of the tear film between the lens and the cornea. The tear film is thinnest in the area of the apex.
Retinal Spot Diagram with Lens
		The final lens design was a quadrant specific design with different lens powers within the optical zone. The net result is a significant tightening of the retinal image and a significant decrease in higher order aberrations from 1.471 microns to 0.568 microns.
Point Spread Function with Lens
		The lens makes the point source of light look like a point source of light.

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