initial scleral lens selection methods

Scleral lens utility is part of our career that has seen dramatic will increase over the previous few years. Whereas scleral lenses date again to the 1800s,^one Their present recognition is a reasonably latest phenomenon.

In keeping with the Scleral Lenses in Present Ophthalmic Observe Analysis (SCOPE) examine, greater than 54% of present scleral lens prescribers say they wore their first lens after 2010 and greater than 80% after 2005.² ​ ​

With rising recognition, producers’ curiosity in providing higher, extra dependable merchandise is rising. At the moment’s labs have the power to alter lenses and alter curves on the micron degree, permitting us to adequately match essentially the most advanced sufferers. Sufferers who expertise delicate to extreme keratoconus, clear marginal degeneration, keratoglobus, and even post-operative issues might discover reduction the place they’d no different choices earlier than.³

Sadly, labs have a limitation. If we’re not offering the lab with the proper knowledge, we’re doubtless thwarting their potential for achievement. Rising our productiveness with these glasses is essential and begins from the very starting.

The correct selection of your first lens can go a good distance in decreasing pointless seat time in addition to rising the probability of a profitable match. On this article, we’ll overview 2 strategies of selecting a beginning scleral lens.

Methodology 1: View profile

You’ll find practitioners who advocate utilizing keratometry readings as a place to begin for scleral lens match. Nevertheless, the literature sometimes doesn’t assist this, as the connection between keratometry and sclera form is quite weak.⁴ Scleral lens alignment is extra primarily based on sagittal peak, and it’s troublesome to estimate corneal values ​​to grasp scleral form.⁵

Corneal topography alone is useful in figuring out the general corneal form and the steepest a part of the cornea, however it has its limitations. Corneal topography doesn’t present knowledge on the scleral touchdown website.⁶

A latest examine has proven that the form of the sclera is extremely asymmetrical, and the asymmetry isn’t often of the identical extent as that discovered within the corneal toricity.⁷ That is clear proof that extra data is required than our keratometers and corneal topographers present.

Understanding the scleral form is important when starting scleral lens becoming. Measuring a affected person’s facet profile with none instruments is a ability I’ve discovered to develop through the years.

This profile imaging methodology includes lifting the higher and decrease eyelids and evaluating the general form of the sclera (Determine 1). Whereas this methodology lets you assess solely the higher and decrease corneoscleral angle, it is a wonderful start line within the absence of different instrumentation.

The speculation behind this methodology is supported by a sequence of research carried out at Pacific College.⁸ Research have reviewed anatomical angles that type past the limbus. Though this overview was not designed to assist profile viewing by nature, it was one of many first to measure clear variations in scleral form. These are the variations we hope to disclose with this preliminary methodology of lens choice.

Profile imaging is a ability that we as eye medical doctors can study on our personal. This methodology makes use of the understanding that we should think about each the cornea and the scleral touchdown website when selecting a beginning lens.

The primary few makes an attempt might require revision of cascading selections as you place varied diagnostic lenses within the affected person’s eye. After you have discovered the proper lens (one which adequately covers the steepest a part of the cornea), take away the lens and reassess this facet profile.

Now that the proper sagittal worth has been discovered, take a psychological image of what the scleral sagittal worth seems like. This can assist enhance your success fee over time. Effectivity with this methodology takes quite a lot of apply, trial and error.

One of many largest flaws of this methodology is that it relies upon closely on the plumber’s degree of experience. After you set the lens in your eye, it is as much as you to correctly consider your findings and go this data on to the producer.

This turns into more and more troublesome when coping with conjunctival irregularities corresponding to pinguecula or any scleral asymmetry. There’s quite a lot of variability past the limbus. A latest examine evaluating this discovered that almost all of members who have been potential scleral lens wearers have been asymmetrical or irregular past the limbus.⁸

Methodology 2: Profilometry

Profilometry is a technique of acquiring topographic knowledge concerning the sclera. This accommodates useful data for preliminary lens choice, as an in depth description of the sagittal peak and sclera is immediately offered. (Determine 2). This instrumentation makes preliminary lens choice hassle-free by offering quantitative knowledge factors that may information your course of.

There are at the moment 3 instruments obtainable that supply the power to measure the topography past the limbus. Two of the designs are placido disc-based. These instruments embody Eye Floor Profiler (Eaglet) and sMap3D (Visionary Optics). Placido disc devices require using fluorescence for picture seize. The third instrument is a rotating Scheimpflug imaging digicam referred to as the Pentacam Corneal Scleral Profile (Oculus). This gives 1000’s of knowledge factors overlaying a 18 to 22 mm diameter vary of the sclera.^9,10,11

After a picture has been taken, the software program will information you on the very best sagittal elevation and peripheral curves earlier than any lenses are positioned on the attention (Determine 3). If knowledge assortment is perfect, trial and error is often not mandatory. Even new installers can take pleasure in instantaneous success, as algorithms are extremely efficient find the proper first lens.

Along with accuracy, profilometry has different benefits for preliminary lens choice. These benefits have been highlighted through the COVID-19 pandemic, when reusing diagnostic lenses and time spent within the workplace turned actual issues.

With the added accuracy of preliminary lens choice, practitioners can order lenses purely empirically and carry out excessive refraction on a lens particularly designed for a affected person. As a result of the success fee for these lenses may be very excessive, this methodology additionally considerably reduces the time spent within the chair.

diameter choice

An equally necessary issue within the preliminary lens choice is across the diameter for use. Correct diameter choice of the lens tells the general objective and true definition of a scleral lens.

The Scleral Lens Schooling Society has not too long ago up to date the accepted language for the definition of scleral lenses. Scleral lenses are at the moment outlined as a lens that’s “positioned to cowl the complete cornea, together with the limbus, and descend on the conjunctiva, which covers the sclera.”¹²

Selecting the best diameter to your first scleral lens generally is a very simple course of. After acquiring the horizontal obvious iris diameter (HVID) for a affected person, including 5 to six mm is enough to sufficiently descend a couple of millimeters past the limbus.

are you prepared to begin?

Scleral lens utility generally is a satisfying expertise for each the practitioner and the affected person. Whereas we talk about solely 2 strategies of selecting the beginning lens, different viable choices embody ocular coherence tomography (OCT)13 and even measurement-based fashions.¹⁴

No matter methodology you select for preliminary lens choice, it is necessary to take a scientific, evidence-based strategy to make sure success. It goes with out saying that there’s way more to scleral lens compatibility than the preliminary lens choice. Nevertheless, bettering effectivity on this a part of the examination will streamline the method and enhance your success fee considerably.

References

1. Bowden TJ. Contact Lenses: The Story. Kent: Bower Home Publications; 2009.

2. Nau CB, Harthan J, Shorter E et al. Demographics and prescribing patterns of scleral lens practitioners: the SCOPE examine. Eye Contact Lens. 2018;44(appendix 1):S265-S272. doi:10.1097/ICL.0000000000000399

3. van der Worp E, Bornman D, Ferreira DL, Faria-Ribeiro M, Garcia-Porta N, González-Meijome JM. Fashionable scleral contact lenses: a overview. Depend Lens Entrance Eye. 2014;37(4):240-250. doi:10.1016/j.clae.2014.02.002

4. Schornack MM, Patel SV. The connection between corneal topographic indices and scleral lens base curve. Eye Contact Lens. 2010;36(6):330-333. doi:10.1097/ICL.0b013e3181eb8418

5. Consejo A, Llorens-Quintana C, Bartuzel MM, Iskender DR, Rozema JJ. Rotation asymmetry of the human sclera. Acta Ophthalmol. 2019;97(2):e266-e270. doi:10.1111/aos.13901

6. Macedo-de-Araújo RJ, Amorim-de-Sousa A, Queirós A, van der Worp E, González-Méijome JM. The connection of plasido corneal topography knowledge with scleral lens placement parameters. Depend Lens Entrance Eye. 2019;42(1):20-27. doi:10.1016/j.clae.2018.07.005

7. Kinoshita B, Morrison S, Caroline P, Kojima R, Lampa M. Corneal toricity and scleral asymmetry….are they associated? Poster presentation: World Particular Lens Symposium; 21-24 January 2016; Las Vegas, NV.

8. Kojima R, Caroline P, Graff T et al. Eye form and scleral lenses. Contact Lens Spectrum. April 1, 2013. Retrieved September 29, 2022. https://www.clspectrum.com/points/2013/april-2013/eye-shape-and-scleral-lenses

9. ESP—Eagle Eye. Eagle Eye. Retrieved September 29, 2022. www.eaglet-eye.com/the-esp

10. sMap3D. Visionary Optics. Retrieved September 29, 2022. www.visionary-optics.com/smap3d

11. Maller Okay. Pentacam CSP software program will increase the effectivity and effectiveness of advanced customized scleral lens design. Fashionable Optometry. April 2019. Retrieved September 29, 2022. https://modernod.com/articles/2019-apr-supplement/pentacam-csp-software-to-improve-efficiency-and-effect-of-complex-custom-scleral-lens-design?c4src=article:infinite- draft

12. Michaud L, Lipson M, Kramer E, Walker M. Official information to scleral lens terminology. Depend Lens Entrance Eye. 2020;43(6):529-534. doi:10.1016/j.clae.2019.09.06

13. Vincent SJ, Alonso-Caneiro D, Collins MJ. Optical coherence tomography and scleral contact lenses: scientific and analysis functions. Scientific Exp Optom. 2019;102(3):224-241. doi:10.1111/cxo.12814

14. Nau A, Shorter ES, Harthan JS, Fogt JS, Nau CB, Schornack M. Multicenter overview of impression-based scleral units. Depend Lens Entrance Eye. 2021;44(5):101380. doi:10.1016/j.clae.2020.10.010