Lens Dynamics, Inc. (LDI) is the largest manufacturer of keratoconus lenses in North America through its work with the Dyna Family of Lenses. Most of LDI’s lenses are for highly irregular corneas and we have listened to our practitioners asking for larger diameter lenses for some patients. This led to the development of the Dyna Intra-Limbal (DIL) lens and subsequent FDA approval in March 2002.

Corneal conditions that the DIL successfully fits include: pellucids marginal degeneration, globus keratoconus, post penetrating keratoplasty, tilted grafts, inferior apexed keratoconus, highly asymmetric corneas, intolerant patients, soft toric non adapt, and compromised corneas. An excellent choice for myopia control as well.   LDI recommends the Dyna Cone Plus+ series for steep nipple Keratoconus patients. The standard DIL diameter is 11.2 mm, but is available from 10.0 to 12.0 mm, depending on the condition being treated. The lens is to be fit within the limbus as opposed to some designs that extend onto the sclera. The DIL design achieves the comfort and irregular corneal masking characteristics of scleral designs without the many difficulties encountered with those designs.

Parameters

The standard lens is 11.2mm diameter with a 9.4 OZ.  Since the DIL design is custom made, most parameters are available: any power, toric designs, any base curve, reverse geometry secondary curves, different optical zone sizes and a proprietary peripheral curve system that starts with a standard edge lift but has flatter or steeper edge lifts available.  Lab time is one day for spheres. We also have diagnostic sets available from our loaner library and also for purchase.

Keratoconic Corneas

Only steep Nipple cones are best fitted by smaller diameter (8.0 mm - 9.9 mm) contact lens designs. Globus and oval cones, very inferiorly placed cones, double cones and superior cones are all best fitted with larger diameter designs. The Dyna Intra-Limbal design with a standard diameter of 11.2 mm works best on these corneas.

Pellucid Marginal Degeneration (PMD)

PMD is often misdiagnosed as severe keratoconus. PMD exhibits central to inferior corneal thinning with AGAINST-THE-RULE astigmatism and a curious steepening pattern. This topography has been described as two birds kissing, a crab claw, or a handle bar moustache appearance. See topography on the right. Post Penetrating Keratoplasty Many keratoplasty patients need visual enhancement following surgery. A critical component of these fits is to vault the host-graft interface. Impingement of this area will result in corneal deterioration and/or graft failure. A larger diameter corneal lens with large base optical zone is needed to vault the suture area. The Dyna Intra-Limbal design meets these criteria.

Types of Keratoplasty:

Standard Grafts: Donor zones of 6-9 mm with no steepening in the graft area. These can also be quite irregular with multiple ridges and valleys.
Steep Grafts: The graft area is quite steep and possibly shows signs of returning Keratoconus.
Raised Grafts: The cornea exhibits a steep area along most of the graft/host juncture.
Tilted Grafts: The graft area has a fl at area at one side and a steep area at another size.
Sunken Grafts: The graft area sinks, resembling a Post Lasik topography. This type of graft is better fit with a Dyna Intra-Limbal Special Reverse Geometry design.

Post Refractive Surgery Patients

Post Lasik: These corneas typically require a reverse geometry design due to the fl at central area surrounded by a steeper peripheral zone. Try the Dyna Intra-Limbal Special Reverse Geometry design on these corneas.
RK Corneas: Some of these corneas will have the fl at central zone surrounded by a steeper peripheral area and others will not. If the topography does NOT have a fl at area in the center, use the standard Dyna Intra-Limbal lens. If it does have a fl at central appearance, use the Special Reverse Geometry lens design.

Fitting Cones, Pellucids & Grafts

Base Curve Selection:

Start with the base curve from the fitting set that is closest to the average of the central Ks or the average of the Sym Ks if using topography. For instance, if the Ks are 45.00 x 150 by 51.00 x 60, select a trial lens closest to 48.00 D or 7.03 mm.

Diameter Selection:

The overall diameter should be approximately 0.2 mm to 0.5 mm smaller than the cornea and may need to be smaller or larger than 11.2 mm to achieve this. The standard Dyna Intra-Limbal lens is 11.2 mm in diameter with a 9.4 mm BOZ. The lens is designed to fit intra-limbal and to achieve 0.5 mm to 1.0 mm of movement. With adequate edge lift, light limbal involvement is acceptable. The BOZ can be changed from the standard 9.4 mm to get the best fit. Small adjustments in sagital depth can be achieved by increasing or decreasing the BOZ. Dyna Intra-Limbal is available in diameters 10.4 mm to 12.5 mm.

Desired Fluorescein Pattern:

Keratoconus and Pellucid Marginal Degeneration
The best fit will exhibit a light feather touch on the apex of the steepened area. The rest of the pattern should be as aligned as possible, but may exhibit a feather touch over the ectasia pooling outside of this area and alignment in the peripheral area creating a bulls eye appearance. Since ectasias are often located inferiorly, it is not unusual to see a fairly deep tear pool above the area of ectasia. This is acceptable as long as there is not a large or static bubble trapped in this area. Small, transient bubbles are acceptable on advanced ectasia. The edge profile will show about 0.2 mm of clearance and overall lens movement will be 0.5 mm to 1.0 mm.

Post Penetrating Keratoplasty
The best fit will exhibit as close to an alignment fluorescein pattern as is possible depending on the irregularity of the cornea. There should be no bearing on the host/graft margin. The edge profile will show about 0.2 mm of clearance and overall lens movement will be 0.5 mm to 1.0 mm.

Post R-K
The best fit will exhibit as close to an alignment fluorescein pattern as is possible depending on the irregularity of the cornea. There should be minimal to no bearing on incision sites as this can cause epithelial defects and possible scarring. The edge profile will show about 0.2 mm of clearance and overall lens movement will be 0.5 mm to 1.0 mm.

Edge Profile:

The desired edge lift will be about 0.2 mm wide. The Dyna Intra-Limbal system starts with a standard edge lift. Flatter or steeper edge lifts are available in a step system. You can order any edge profile in steps 1 through 15 flatter and steps 1 through 10 steeper. All changes are computer modeled so that reproducibility is insured.

Examples: Should the standard edge profile show pinch off, start with a 1 step Flat edge lift. This should be adequate in most cases. Flatten the edge lift until a 0.2 mm edge width is achieved. The same is true in reverse. If the standard edge profile shows too much edge lift, steepen the edge until a 0.2 mm edge width is achieved.

Quad Sym® Edge Treatment:

Many times one or more of the four quadrants may have touch or stand-off. In these cases, the Quad Sym PC Option allows for increasing or decreasing the edge lift in any or all quadrants.

Other Design Options:

Multifocal Option: Front aspheric optics can be added for presbyopic correction. The base curve is not affected.
Toric Options: Bitoric and front toric designs are available.

Downloads

Attachments:

DIL FaBs	[Features and Benefits of the DIL and DIL Elite]	213 Kb
DIL Fitting Guide	[Fitting Guides for Keratoconic, Corneas Pellucid Marginal Degeneration, Post Penetrating Keratoplasty, Post Refractive Surgery]	1780 Kb
Vertex Calculator	[Must have Microsoft Excel to use]	17 Kb