Speaker: Ania Gloomier II, Assistant Professor at New England College of Optometry.
Focus: Basics of scleral lenses, assessment, and fitting.
History of Scleral Lenses
Scleral lenses have seen a resurgence in the last decade.
Initial discovery: 1988, first scleral lens made of blown glass.
Early usage for conditions like keratoconus and high refractive errors.
Shift away from glass due to low oxygen permeability; introduction of PMMA plastic.
PMMA offered better fitting but still lacked oxygen permeability.
Current scleral lenses utilize modern materials with improved oxygen permeability.
Definition and Characteristics
Scleral Lens: Rigid gas permeable lens designed to vault over the cornea and rest on the sclera.
Function: Clears irregularities in the cornea, holds a saline reservoir to keep the cornea hydrated.
Comparison to Corneal Gas Permeable Lenses:
Corneal lenses rest on the cornea, allowing for tear exchange.
Scleral lenses interact less with the eyelids, leading to greater comfort and stability.
Scleral Lens Nomenclature
New nomenclature based on resting zones:
Corneal Lens: Lands on cornea.
Scleral Lens: Lands entirely on the sclera.
Corneal-Scleral Lens: Lands between cornea and sclera.
Distinction between mini-scleral (<6mm) and large scleral (>6mm).
Basic Scleral Lens Design
Zones:
Optic Zone: Houses base curve and power; can correct astigmatism and add multifocal optics.
Transitional Zone: Connects optic zone to haptic zone; crucial for sagittal depth control.
Haptic Zone: Contacts the sclera; needs to distribute lens weight evenly.
Toricity and Scleral Topography
Importance of understanding scleral shape for better fitting.
Scleral toricity increases with distance from the limbus; less correlation with corneal toricity.
Toric Peripheral Curves: Helps in matching the natural toric shape of the sclera to improve comfort and decrease edge lift.
Indications for Scleral Lenses
Beyond keratoconus, scleral lenses are used for:
Corneal irregularities (e.g., scarring, ectasia).
Protection of ocular surface in conditions causing chronic desiccation.
Refractive errors (e.g., high myopia, astigmatism).
Fitting Challenges
Challenges include determining clearance values, centration, and ensuring patient comfort.
Initial lens selection is key to saving time and ensuring fit.
Insertion and Removal Techniques
Insertion:
Use large DMV plunger.
Center the lens on the plunger and overfill with saline.
Patient positions: face parallel to the floor.
Avoid bubbles; if present, lens must be removed and reapplied.
Removal:
Use small DMV suction device.
Patient looks down, gently rock lens to break suction before removal.
Assessment of Scleral Lens Fit
Central Clearance: Assess first, followed by limbal and peripheral zones.
Use fluorescein to evaluate clearance and check for bubbles.
Document findings and evaluate lens movement.
Additional Tools and Techniques
Use of anterior segment OCT for precise measurements and assessments.
Identifying complications like impingement or excessive edge lift.
Lens Care and Maintenance
Use appropriate care solutions (e.g., GP care solutions, hydrogen peroxide).
Rinse with non-preserved saline before insertion.
Provide patients with clear instructions and resources for care.
Conclusion
Scleral lenses provide a valuable option for many patients, especially those with complex conditions. Their fitting requires careful assessment, manipulation, and patient education.