Have a patient with keratoconus and can’t find seem to find the right lens fit? Or perhaps a post-LASIK patient who needs improved vision and prefers contacts? Scleral lenses may be the answer. Because these large-diameter gas-permeable lenses do not impinge the cornea, they are a comfortable option for many of your patients with vision compromised by corneal irregularity and ectasia.
1. Determine an appropriate candidate.
Consider fitting scleral lenses for:
• Patients with primary corneal ecstasia (e.g., keratoconus, keratoglobus and pellucid marginal degeneration).
• Patients with secondary corneal ectasia (e.g., post-LASIK, post-PRK and post-RK).
• Patients with persistent epithelial defects.
• Patients with a rehabilitated ocular surface, including cases of severe dry eyes, graft vs. host disease, Sjögren’s syndrome, Stevens-Johnson syndrome and neurotrophic keratopathy.
• Patients with inflammatory conditions, such as limbal stem cell deficiency and ocular cicatricial pemphigoid.
Since we currently do not have data on the long-term impact of scleral lens wear on the normal cornea, such use is considered controversial and not recommended. However, refractive error, astigmatism and presbyopia can all be corrected with scleral lenses.1-9
2. Find your starting point.
Each type of scleral lens has a unique fitting philosophy; thus, it is important to first read the individual fitting guide. This will help you determine a starting point and provide an outline for how best to fit the lens.
Start with a physical examination to evaluate the anterior segment. In particular, look for corneal staining and the appearance of the eyelids, including signs of meibomian gland dysfunction.
Scleral lenses are fit on sagittal depth—the measurement from the flat plane to the highest point of a concave surface. Since not all practitioners have immediate access to an anterior segment OCT, corneal topography is recommended to evaluate the cornea to determine a starting point for the fit.
Due to a poor endpoint in patients with corneal ectasia and ocular surface disease, subjective refraction may or maybe not helpful. Keep in mind that the refractive endpoint does not tend to correlate with the scleral lens power.9,10
3. Avoid bubbles during lens insertion.
When inserting the scleral lens, ask your patient to bend over so his or her face is parallel to the horizontal plane. It is important to completely fill the scleral lens with non-preserved sodium chloride solution. Try holding the eyelids open for easier lens insertion.
If bubbles appear, consider using a thicker non-preserved agent to fill the bowl of the lens (e.g., carboxymethylcellulose sodium solution).
Remember that the bowl of the scleral lens should be filled upon insertion, and should not drain out. If a bubble does occur, remove the scleral lens and reinsert.
4. Allow the lens to settle.
When a scleral lens is first placed on the eye, it may appear to fit well. However, the lens settles into the conjunctiva with time and the fit may appear quite differently a few hours later. When scheduling your patient’s initial fitting and follow-up dispensing appointment, allot extra chair time accordingly. Also, consider asking your patient to return four hours after your initial appointment to better gauge the lens fit.
5. Evaluate scleral lenses with fluorescein.
A few hours after your dispensing appointment, reevaluate the lens fit with fluorescein and white light to guarantee that fluid exchange is occurring with lens wear. If fluorescein is still present at that time, then evaluate the lens fit. If fluorescein is not present, apply a fluorescein strip to the conjunctiva to evaluate for fluorescein uptake under the lens.
6. Assess corneal clearance.
Note that there is no set amount of central corneal clearance required under the scleral lens. Smaller corneo-scleral lenses may only need 20µm to 30µm, whereas larger diameter scleral lenses may go up to 500µm. Instead, the amount of clearance varies with the condition.
Consider larger diameter lenses when a greater sagittal height is necessary, in cases of keratoglobus or when keratoconus presents with large differences in corneal sagittal height. On the other hand, post-corneal grafts or corneal scars may need a smaller sagittal height.
Keep in mind that corneal thickness may be useful as a comparison and reference. Normal corneas have an average thickness of 535µm (centrally) and 650µm (peripherally). With corneal ectasia patients, corneal center thickness may be significantly thinner.11,12
7. Evaluate the periphery of the lens.
When evaluating the fit of the scleral lens, address common complications. For example, conjunctival blanching, with a white appearance, is caused by pressure on the conjunctiva. Circumferential conjunctival blanching is a result of a landing that is too flat or too steep. In these situations, changing the fit of the peripheral curves may improve the fit of the lens.
If the blanching is under the entire area of the scleral lens, it may be necessary to increase the landing zone by increasing the lens diameter. If blanching is under the scleral lens edge, this may cause conjunctival staining and hypertrophy over time.
Sectoral conjunctival blanching may occur due to an irregular scleral shape. If this presents, a non-rotationally symmetrical lens may help create a more ideal fit. If a pinguecula is present, create a notch in the lens to leave additional room.
Impingement—when the lens edge pinches the conjunctiva—occurs when negative pressure builds up behind the scleral lens with the blink. As the scleral lens flattens with the blink, fluid escapes. Conjunctival staining and hypertrophy may be present after lens removal. In order to eliminate impingement, consider decreasing the sagittal depth, flattening the peripheral curves if the impingement is at the outer edge of lens, steepening the peripheral curves if impingement is at inner edge of the peripheral curve or increasing the center or junction thickness.
8. Evaluate for lens flexure.
If your patient complains of blurred vision or astigmatism on spherocylindrical over-refraction, evaluate for lens flexure by performing keratometry or topography over the lens. It may be necessary to increase the center thickness of the lens to reduce warpage.
9. Take care when removing the lens.
A large or small DMV plunger (DMV Corporation) is useful when removing scleral lenses. The plunger is squeezed to induce suction and then applied to the periphery of lens. Remember to avoid the central part of the lens. Once suction is induced, twist and pull the plunger and lens away from the eye to remove the lens.
Scleral lenses may also be removed by the manual two-finger method. After the patient looks down, move the lower eyelid outward while applying mild pressure to the eyeball, then gently push the lower eyelid with the index finger underneath the lower edge of the lens in order to remove the lens.
10. Stay informed.
The best way to keep abreast of new developments is to stay informed. The Scleral Lens Education Society (SLS) is a non-profit organization and resource website ( www.sclerallens.org) dedicated to teaching practitioners how to fit all different types of scleral lens designs in order to manage corneal irregularity and ocular surface disease.
Dr. Barnett is a principal optometrist at the UC Davis Medical Center in Sacramento, where she performs primary care and eye examinations and fits contact lenses, including specialty lenses. She also lectures on optics and contact lenses to ophthalmology residents.
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