W8: Scleral lenses

WATCH LECTURE

Ability to quantify corneal shape and size, and pupil

Knows the methods for the CL correction of aphakia, high ametropia, keratoconus, post- surgical and post- refractive surgery

Contents

What anatomical features influence scleral shape?

• Nasal sclera is flatter

• Space from limbus to muscle insertion:

  • Temporal: 7.0 mm

  • Superior: 7.5 mm

  • Inferior: 6.5 mm

  • Nasal: only 5.0 mm

What do scleral profile measurements reveal about peripheral cornea and anterior sclera?

• Avg peripheral corneal radius: 9.10 mm (range 7.80–10.80 mm)

• Avg anterior scleral radius (nasal + temporal): 12.40 mm (range 10.10–16.60 mm)

• Some peripheral corneal radii were actually flatter than some anterior scleras

Scleral toricity

What is fourier transform profilometry?

Topographers: Corneo-scleral profile

Flashes vertical line patterns on the fluorescein-dyed tear film to map corneal & scleral topography

What are the key features of scleral and limbal profile asymmetry (vertical vs horizontal sag differences)?

• Traditional concept shows smooth corneal–scleral junction, but reality shows an angled transition

• Horizontal vs vertical asymmetry is significant

  • Vertical sag ≈ 3,660 µm

  • Horizontal sag ≈ 3,490 µm

  • Difference ≈ 170 µm

• Sectoral sag pattern: Inferior > Nasal > Temporal > Superior

• Overall rule shown: N sag > T & I sag > S, but full order = I > N > T > S

• Limbal profile reveals true asymmetry important for scleral lens fitting

Why is scleral lens fitting dependent on understanding ocular shape?

• Scleral CLs interact with areas beyond the cornea, incl the limbus & sclera

  • Anterior eye= not a symmetrical solid

  • Lens + lens edges contact the nasal paralimbal zone before the temporal

What material advancements have supported the resurgence of scleral lenses?

• Newer scleral lens materials have higher O₂ permeability (Dk)

• They do not rely on tear exchange beneath the CL

• Result =improved corneal physiology during wear

What technological and manufacturing developments have improved scleral lens fitting?

• Advancements and automation in lathing

• Greater understanding of ocular shape from:

  • Topography

    • Anterior segment OCT

    • Profilometry

    • Scheimpflug imaging

What are the primary visual indications for scleral lenses?

• Irregular astigmatism

  • Post-traumatic irregularity

  • Penetrating Keratoplasty

  • Keratoconus

  • Pellucid Marginal Degeneration

  • Post-refractive surgery

  • Post herpetic infection

What additional functional indications support the use of scleral lenses?

• Athletes

• Poor CL centration

• Poor CL stability

• Corneal GP CL intolerance

• High scripts

What are the therapeutic indications for scleral lenses

• Therapeutic indications

  • Chemical burns

  • Ocular pemphigoid

  • Stevens–Johnson syndrome

  • Symblepharon management

• Graft vs host disease

• Exposure keratitis

• Neurotrophic keratopathy

• Persistent epithelial defect(s)

• Severe dry eye

  • Sjögren’s syndrome

  • Filamentary keratitis

  • Limbal stem cell deficiency

What does current evidence suggest about intra-ocular pressure (IOP) changes during scleral lens wear?

• As measured using a non-standard transpalpebral IOP method, scleral lens wear may increase IOP by ~5 mmHg on average.

  • Regardless of scleral lens diameter.

• Further research =req’d to det whether clinicians should exercise caution when fitting scleral lenses on patients at risk for glaucoma.

Scleral lens design

What are the key features of the central/optical zone in a scleral lens?

• Front surface optics can be spherical or aspheric.

• Back surface of the optical zone usually does not touch the cornea.

• Post-lens fluid contributes optical power.

What is the role of the transition/mid-peripheral/limbal zone in a scleral lens?

• Connects the end of the optical zone to the beginning of the landing zone going outwards

• Sets the sagittal height of the lens.

• In smaller designs:

  • Important to match the limbal shape.

    • Minimises mechanical pressure, as limbal clearance is typically absent (lens rests here).

Fenestration

What are the characteristics of the landing/scleral/haptic zone in a scleral lens?

• Region where the lens fits and makes contact with the eye.

• Should be at least 3 mm wide for comfortable wear.

• Defined as a flat curve or series of curves, often with radius 13.5–14.5 mm.

What are the main fitting goals for a scleral lens?

• Clears (vaults) the central cornea

• Increases limbal clearance

  • Visible as a bright ring of fluorescein above the limbus

• Scleral alignment

  • All pressure, weight, and bearing of the lens should be on the sclera

Apical Clearance

Limbal Clearance Zone

What are the characteristics of a flat landing zone fit in a scleral lens?

• Ring of bearing on the inner part of the landing zone

• Air bubbles may appear in the periphery of the lens

• Possible frothing

What are the characteristics of a steep landing zone fit in a scleral lens?

• Bearing occurs on the outer zone

• Fluorescein pooling visible extending inward underneath the landing zone from the corneal clearance

• Blanching

Landing: Impingement

How is the sagittal height method used in scleral lens fitting?

• Determine the anterior eye’s sagittal height for:

  • the chord length at 15.0 mm (for a 16.5 mm TD scleral lens)

• Add 0.30 mm (300 μm) to that sagittal height to select the lens

How is the sagittal height of a scleral contact lens calculated?

• Eye’s total sagittal height = sag @ 10 mm + sag @ 15 mm

  • Example: 2100 μm + 1900 μm = 4000 μm

• Initial diagnostic CL = 4000 μm sagittal height + 300 μm apical clearance = 4300 μm

How is sagittal height assessed using corneal topography?

• Topographers (e.g., Medmont) measure sag heights within 10.0 mm chord lengths

• Avg sag height btwn 10.0 mm and 15.0 mm chord ≈ 2,000 μm

  • Similar sag heights found in normal + keratoconic eyes

  • Sag from 10 to 15 mm chords is unaffected by rCorneal Apex

How is the sagittal height for a scleral contact lens calculated?

• Cornea/Sclera Sag: 2,000 μm

• Corneal Sag: 1,727 μm

• Corneal Clearance: 300 μm

• Total Sag: 4,027 μm

• Lenses are ordered by sag (e.g., 4.0 Sag = 4,000 μm)

How can adjustments to the limbal zone affect the sagittal depth of a scleral contact lens?

• Most scleral CL designs allow independent parameter adjustments for different portions of the lens.

• Increasing the rise of the limbal zone by 5° will increase the overall sagittal depth of the lens by 125 μm

Label:

_____________ limbal clearance

What does OCT imaging reveal about scleral CL settling over time?

• Initial apical clearance upon application: 300–400 μm

• Clearance reduces over time as the lens settles on the eye

• Example (Right Eye, baseline 370 μm):

  • 1 hr: 320 μm (50 μm reduction)

  • 2 hr: 310 μm

  • 4 hr: 295 μm

  • 6 hr: 280 μm

  • 8 hr: 220 μm (150 μm total reduction)

What factors contribute to the presence of bubbles under a scleral lens?

• Bubbles can arise from:

  • Insertion technique

  • Lens fit (more frequent)

• Observe their location to det cause

What is the clinical significance of bubble location under a scleral lens?

• Central bubbles → central sagittal height too large, needs lowering.

• Small bubbles that move behind the lens may be acceptable if they do not cross the pupil margin.

• Large stationary bubbles → not acceptable.

• Limbal area bubbles → too much limbal clearance; may req:

  • Steepening the BC

  • Dec’ng the limbal shape profile, depending on lens design.

How can air bubbles be managed or minimized when fitting scleral lenses?

• Not always preventable, esp w/ non-uniform tear reservoir (e.g., corneal ectasia).

• Consistent air bubbles may be reduced by using a more viscous solution for lens insertion.

Asphericity and quadrant specific

Fill in the table:

Semi scleral lenses

Fill in the table:

Semi scleral lenses

Full scleral*

Application

How would you assess the fit of scleral lenses using a slit lamp?

White light

• Use optic section to assess tear film clearance:

  • Centrally

  • Laterally

  • Vertically

  • Over the limbus all around

• Assess the edge fit:

  • Heel → pressure on inside of edge curve

  • Toe → pressure on outer side of edge curve

What are the limitations of white light slit lamp assessment for scleral lenses?

• Less accurate than OCT

• Ideally, lens thickness should be known; if not, a 1:1 ratio is accepted

• Corneal thickness is not always uniform, which can affect assessment

How would you assess the fit of scleral lenses using a slit lamp?

Blue light

• Use blue light for overall view of limbal clearance

• Easy to detect bubbles or bearing

• Easy to observe decentration, often caused by lens gravity

  • Lift the top lid to check for superior limbal tissue bearing

What is the expected scleral lens settling pattern and related patient education?

• Settling time: allow 20–30 minutes for the lens to sink in

  • Initial drop: 50–80 microns

  • Further drop after 6–8 hours wear: 50–100 microns

• Check tear film

• Educate pt that tear debris is normal in nearly 30% of scleral wearers

  • Reinsertion throughout the day may be needed to remove debris

What is the correct technique for removing a scleral lens with a plunger?

1. Aim for the lower half of the lens with the plunger.

2. Once the plunger is sucked on, make a movement away from the eye, and upward. This will break the seal and the lens can easily be removed.

3. Lift the lens edge from the eye

Lens care

Scleral CLs: Is Saline Appropriate?