11.2 Scleral Parameter Adjustments: Sagittal Depth, Landing Zones & Micro-Vaults

11.2 Scleral Parameter Adjustments and Localized Vaults

Modern scleral lenses are multi-zone systems. The optic zone, transition or limbal zone, and landing zone may be coupled in one design and partly independent in another. A good order states the observed problem, location, intended result, and the exact design being used.

Describe the Finding First

Document:

• lens identifier, diameter, material, and design;
• application and examination time;
• central and focal clearance by method and location;
• limbal clearance around the full circumference;
• compression, impingement, or edge lift by clock hour;
• rotation marks and stability;
• obstacles such as pingueculae, pterygia, scars, blebs, or drainage devices;
• corneal and conjunctival staining;
• over-refraction, vision, comfort, fogging, and edema findings.

A laboratory cannot safely interpret “too steep” without knowing which zone and which tissue finding prompted the statement.

Sagittal Depth and Base Curve

Total sagittal depth describes lens depth at a specified chord or diameter. Increasing it generally increases clearance, but the amount of on-eye change depends on where and how the design adds depth. A base-curve change can also alter optics and reservoir shape. Some platforms let the laboratory change central sagittal depth while holding other zones relatively stable; others do not.

Use microns, steps, angles, or curve labels exactly as that laboratory defines them. There is no universal directive that every scleral change must be ordered in microns or that the base curve must never change.

Zone-Specific Changes

When central clearance is acceptable but the limbus touches, request a limbal or transition-zone review rather than automatically increasing the whole lens. When the center touches broadly, an overall or central sagittal change may be appropriate. When one quadrant bears, a toric, quadrant-specific, or free-form landing change may solve the problem with less unnecessary thickness.

For compression, identify the broad area under the haptic. For impingement, identify a focal edge digging into tissue. For edge lift, note bubble entry, movement, debris, or lid interaction. Terms such as heel and toe differ across laboratories; include photographs or OCT when possible.

Localized Obstacles

Options can include changing total diameter to land inside or outside an elevation, using a notch or cutout, adding a localized microvault or channel, or ordering an impression-based or scan-based free-form surface.

A notch interrupts the physical edge and must stay aligned with the target. A localized vault preserves the edge but still requires stable orientation. The amount and width of elevation are determined from measured anatomy and the laboratory design, not a universal 100-to-200-micron recipe.

Filtering blebs and glaucoma drainage devices require coordination with the glaucoma or prescribing clinician. Avoid pressure, erosion, and device interaction. Do not assume that a contact lens can safely land over a bleb merely because the patient is comfortable.

Rotation and Orientation

Toric or quadrant-specific haptics can improve rotational stability, but markings must be observed after realistic wear. Record the direction and amount of rotation. The laboratory may compensate the feature position, redesign the haptic, or select a different diameter. Do not order a clock-hour vault from an immediate image if the lens later rotates.

Optical Consequences

Any geometry change can affect decentration, flexure, tear-lens power, higher-order aberrations, and over-refraction. Repeat a sphero-cylindrical over-refraction after the redesigned lens settles. Verify power with the laboratory rather than manually assuming that a sagittal change has no optical consequence.

After the New Lens Arrives

Verify lens identity and ordered parameters, inspect the surface and edge, and repeat the complete on-eye assessment. Confirm that solving the focal problem did not create new limbal touch, edge lift, blanching, bubbles, excessive reservoir thickness, or reduced oxygen tolerance.

Laboratory Consultation Example

A useful message might state: the current lens has acceptable central clearance after four hours, focal nasal impingement from two to four o'clock over a measured pinguecula, stable orientation mark at six o'clock, no corneal edema, and acceptable over-refraction. The request is for the least disruptive design-supported method to clear the obstacle while preserving the current central and limbal relationship.

This is more actionable than “add a 150-micron vault,” because it communicates the clinical objective and allows the laboratory to translate it into its own geometry.

Exam Traps

• Parameter names and signs are not interchangeable between laboratories.
• Do not correct every touch finding with global sagittal depth.
• A notch or local vault requires stable orientation.
• Do not land on a filtering bleb or drainage device without specialist coordination.
• Recheck optics and the entire fit after a local change.