Have a Safe Landing
Lynette Johns OD FAAO FSLS FBLCA
When fitting scleral lenses, pingueculae can be major conjunctival obstacles. There are a variety of strategies to reduce the interaction.
As a first option, practitioners can fit small diameter scleral lenses (Figure 1, to right) to avoid the elevation - if there’s room. However, if the patient is very ectatic, the landing zone may be too small to support the weight of the lens bridging over the cornea.
Second option is that a scleral lens notch can be created by the manufacturer in which a cut-out is drilled ( in the lens periphery to fit around the pinguecula or elevation (Figure 2, to right). Disadvantages to notching include inconsistent reproducibility, bubble intrusion under the lens if notched too centrally, and pinguecula impingement if not notched enough.
Alternatively, very flat peripheries can be designed to lie upon the pinquecula(e). Using that method, the lens becomes quite loose in the vertical meridian and requires toric peripheral curves to steepen the vertical meridian. When fitting a large diameter scleral lens to land beyond the pinguecula(e), handling of these large diameters can be difficult or a deterrent, and sometimes compression is unavoidable (Figure 3, to right).
This case describes a different approach: a unique feature of Zenlens™ is that it creates a focal microvault to bridge over the pinguecula.
A 47-year-old woman was referred for scleral lens fitting. She had a history of post-PRK ectasia with entering BCVA of OD 20/30+ and OS 20/30. She was dispensed scleral lenses with parameters of OD sag 5.0 mm, limbal 300 μm, diameter 16.0 mm/oblate, base curve/power 7.8/+0.75, landing zone flat 2 @160°/steep 9-total toricity 330 μm, acuity 20/20 and OS sag 5.0 mm, limbal 300 μm, diameter 16.0 mm/oblate, base curve/power 7.8/+0.75, landing zone flat 3@10°/steep 10-total toricity 390 μm, acuity 20/20-).
She returned for a follow-up and complained of redness nasally OD and discomfort (Figure 4, to right).
The nasal periphery is compressing (blanching), and the edge is impinging into the pinguecula. The center of the pinguecula was measured at 4°, and it was 2.5 mm wide at the edge of the lens. A microvault was designed at the edge that had a 500 μm depth and was 3.5 mm wide (creating a gradual height increase to bridge over the elevation). The microvault center was at 8 mm from the center of the lens and was oriented to account for the location of the pinguecula (4°) and the toricity (20° counterclockwise).
The lens is marked with a dot at the 6 o’clock position (which also rotates at 20°). The patient applies the lens with the dot at 6 o’clock, and the lens rot
ates to its position because of the peripheral toricity. (The patient was instructed to place the dot at the bottom of the plunger for appropriate placement). The patient reported immediate and long-term comfort with the microvault. She denies any discomfort or redness during wear or after removal. The lens vaults over the nasal pinguecula without compression or impingement (Figure 5, to right).
Having the ability to vault over a peripheral elevation with a scleral lens landing zone is an excellent option to avoid compression, impingement, wearing discomfort and resultant inflammation of pingueculae, symblepharon or other elevated obstacles. Another advantage is that the microvault is lathed and reproducible. The microvault is actually circular in diameter, but when it is at the edge, it is bisected. The peripheral vaulting can be seen in Figure 6 (below, left). Figure 7 (below, right) shows that the microvault does not affect the circular shape of the diameter, unlike notching.
The microvault can be manufactured internally. Barnett and Ryff described an internal microvault over a Salzmann’s nodule.1 Only one microvault can be fabricated in a lens, so the practitioner must choose the most elevated pinguecula in cases where a pinguecula is present both nasally and temporally. Innovations in scleral lenses, like the microvault, provide more tools for practitioners to enhance the quality and comfort of scleral lenses for their patients.
1. Barnett, M., Ryff, B. Scaling Salzmann Nodular Degeneration with the Zenlens Oblate Design. Poster presented at the Global Specialty Lens Symposium. January 2016. Las Vegas, Nevada.
Lynette Johns is an adjunct assistant professor and clinical attending in contact lenses at the New England College of Optometry.
She was formerly the senior optometrist at the Boston Foundation for Sight where she exclusively fit scleral lenses and managed complex corneal disease.
She is a fellow of the American Academy of Optometry and Scleral Lens Education Society as well as a fellow of the BCLA. She is a clinical and educational consultant to the GP and specialty soft lens division of Bausch + Lomb.