Scleral lenses represent a great alternative for the rehabilitation of eyes that have keratoconus and ocular surface disease, among other pathologies, offering extraordinary comfort and satisfactory vision. In recent years, the number of patients who enjoy the benefits that these lenses offer has grown exponentially in the world.

Despite the advances in the designs of these devices, one of the greatest challenges that the specialist faces when fitting them is to achieve a correct landing of the lens, as the sclera is spherical in only 5.7% of the cases.¹ The remaining 94.3% will require lenses with a toric edge, specific quadrants, or free form.¹

Some of the more common elevations found in the scleral lens landing zone include pingueculae, scarring from prior injury or surgery, pterygia, filtering blebs, or tube shunts. These elevations can be found in a wide diversity of heights, widths, and locations.²

There are a variety of short-term effects that can result from a misaligned scleral lens, including discomfort, redness, instability, arcuate staining, vascular compression (blanching/impingement), and rebound injection after lens removal. If scleral lens misalignment persists over the long term, the previously mentioned effects can be exacerbated and conjunctival hypertrophy development is possible³ (Figure 1).

Preventing the landing of the lens from causing excessive pressure on any elevation or irregularity present in the conjunctiva is essential to ensure comfort and long-term eye health. To achieve this objective, there are options such as focal vaulting that is used to vault a scleral lens over a peripheral corneal or conjunctival elevation,⁴ reducing scleral lens diameter if the irregularity is beyond the limbus, increasing scleral lens diameter if the irregularity is near the limbus, switching to a scleral lens with more than four meridians, quadrant-specific design, customized haptic, molded/impression scleral lens design—and introducing a notch.⁵

The notching method necessitates the use of a lens that is rotationally stable. Initially, a scleral lens should be fit to ensure the rotational stability with using toricity in the landing zone or double-thin zone design.⁶

It is necessary to know the exact location of the elevation, as well as its size and depth, when making a notch. To delimit the area, the patient is observed in the slit lamp, placing the points on the lens with the help of a permanent marker. This information is sent to the laboratory, or the notch can be made in the office if you have the appropriate tools.

There are elements that must be considered when implementing a notch in a lens, on which the success or failure of the adaptation will depend. Here is a look at the top 10.

1. DISPLACEMENT OF THE NOTCH

The place and position that the lens will occupy when implementing the notch will change, suffering a displacement that will cause the lens to rub against the elevation that was intended to be avoided (Figure 2). This will cause discomfort, pain, hyperemia, patient rejection, and long-term conjunctival hypertrophy.

Therefore, making a slightly larger notch (approximately 0.5mm) should be considered, to the measurements of width, height, and depth that are obtained by delimiting with the help of the permanent marker. This is to compensate for the rearrangement that the lens will have, that is, the space that it will cover when placed on the eye.

Once the notch has been made, if it has not completely cleared the obstacle and is rubbing or pressing on it, the area must be delimited again, with the help of the marker, to be sent to the laboratory for reprocessing. Or, if the necessary tools are available, the modification can be made in the office (Figure 3).

An analogy of this point is the work that dentists do when manufacturing a dental piece; they place it in the patient’s mouth and examines the operation of the bite. If this is not satisfactory, they take measurements again, re-mark, and remove the part to modify it and achieve optimal performance.

2. UNEXPECTED ROTATION OF THE NOTCH

Despite correctly marking and delimiting the area on the lens where the notch will be located, there is a probability that it will tend to rotate 10º or more when the lens is placed on the eye (Figure 4).

The unexpected rotation of the lens will cause one edge of the notch to touch, rub, press, and hurt part of the elevation that was intended to be avoided, producing an undesirable effect on comfort, function, and hyperemia equal to or greater than that produced by a lens without modification.

This rotation can be attributed to various factors, including:

• Lenses with toric edges or asymmetric quadrants, in which the scleral toricity is small and insufficient to effectively anchor the lens.
• A notched lens has less suction on the eye, which could cause a shift in lens position.
• Lenses that are not perfectly aligned on landing will cause the notch to have more movement and rotation.
• A notch modifies the structure and dynamics of the lens-eye relationship; therefore, its behavior and position will also change.
• In cases in which there is a need to make two notches in the same lens (for example, in an eye with nasal and temporal pinguecula), this rotation will be more difficult to predict and control for the correct centering of both notches.

One way to discover the rotation that the notch will have and correct it without damaging the lens is to initially make a smaller notch, try the lens on the eye with the incomplete notch to observe the centering, and if you notice rotation, compensate for it by completing the missing part of the notch.

3. SEMI-BLANCHING DELIMITING THE NOTCH

On one of the edges of the notch corresponding to the edge adjacent to it, a slight blanching may be observed because of the redistribution of the weight that this area must carry (Figure 5). This sign can be considered benign since it frequently disappears a few hours after the lens has been placed on the eye and does not require any modification to the design.

4. ROUNDED EDGE THAT INCLUDES AXIAL LIFT

The notch, like the entire lens, must have an edge that respects the physiology of the conjunctiva, ensuring comfort and health in the short and long terms; therefore, the axial lift of the edge and the rounding must be present in it (Figure 6). This aspect is important to consider, especially if the notch is made manually in the office.

This can be done with the help of the modification unit and checked with the slit lamp (Figure 7). A notch with a poor quality on its edge can injure the conjunctiva (Figure 8), potentially compromising eye comfort and health.

5. FOREIGN BODY SENSATION

Some patients report a transient symptom when a notched lens is placed for the first time in their eye, even though it has a perfect size and depth and an adequate finish on the edge. This sensation is more linked to a psychological aspect or initial mistrust. Supporting the delivery of the lens with photographs that explain to the patients the benefit and the elevation that is being avoided to improve comfort helps to make them feel more confident in the modified lens. In the days following adaptation, patients should observe greater comfort with the lens than they did before the notch was made.

6. APPLICATION BUBBLES

The presence of bubbles when applying the notched lens is common and is directly proportional to the size and depth of the notch. Removing and placing the lens again is indicated, so the patient develops sufficient skill to place it on the eye without the formation of bubbles.

7. CLEARANCE MODIFICATION

One of the effects that can be expected in the behavior of the lens when incorporating a notch is a greater settling effect on the eye, which will be directly proportional to the size and depth of the notch; this will generate a reduction in the space that separates the lens from the cornea.

8. REDUCTION OF THE SUCTION AND ADHESION OF THE LENS

The notch in the lens helps reduce suction and lens-eye adhesion. The suction-cup effect present in the scleral lens decreases when the edge is altered. A simple way to check this is to look at how much easier it is to remove a modified lens from the eye compared to lenses that do not have a notch.

9. THE NOTCH IN THE LENS ATTENUATES INCREASED IOP

Scleral lenses have the possibility of increasing intraocular pressure (IOP) in the eye.⁷ According to various studies, this increases on average by 5 mmHg, regardless of diameter and design.⁸

Among the factors that could trigger this increase are the suction force (generated by the difference in external atmospheric pressure, which is greater than that existing under the lens),⁹ the compression of the episcleral veins and/or the deformation of Schlemm’s canal below the landing area of the scleral lens,¹⁰ adjusted lens fitting that may lead to blanching or impingement in one or several sectors of the conjunctiva, or adhesion of the lens to the eye.⁵

The notch reduces the suction and adhesion of the lens on the eye, helping to reduce pressure in the episcleral veins, which could reduce the increase in IOP that occurs with scleral lenses. Further study and research are needed on the subject.

10. IMPACT ON THE STRUCTURE OF THE LENS

The notch can weaken and modify the structure of the lens, affecting its lifespan. Especially if it is thin, it can fracture or break more easily. It can also make the lens more prone to flexure, generating unwanted cylinders and impacting the quality of vision. This can be reduced by asking the laboratory for a suitable thickness in the lens, preventing it from being manufactured too thin.

Notches represent a current alternative in solving problems that occur when there are obstacles in the landing zone of scleral lenses. Incorporating them into clinical practice requires overcoming a learning curve, but will ultimately provide practitioners and their patients with greater satisfaction. CLS

REFERENCES

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3. Noyes MR, Gelles JD. Scleral Lenses: The Perfect Landing, Rev Cornea Contact Lens. September/October 2021;10. Available at reviewofcontactlenses.com/article/scleral-lenses-the-perfect-landing . Accessed July 30, 2022.
4. Barnett M, Arnold TP. Advanced Scleral Lens Evaluation Can Improve Results, how and why to use some of the new technologies in this field. Modern Optometry. May/June 2020. Available at modernod.com/articles/2020-may-june/advanced-scleral-lens-evaluation-can-improve-results?c4src=article:infinite-scroll . Accessed July 30, 2022.
5. Fadel D. Scleral Lens issues and complications. First Edition. Dougmar Publishing Group Inc. August 2020.
6. Barnett M, Johns L. Ophthalmology Current and Future Developments (Volume 4), Contemporary Scleral Lenses, Theory and Application. Bentham Books. 2017:373.
7. Aitsebaomo AP, Wong-Powell J, Miller W, Amir F. Effect of Scleral Lens Wear on intraocular pressure. Invest Ophthalmol Vis Sci. 2018 July;59:1765.
8. Michaud L, Samaha D, Giasson CJ. Intra-ocular pressure variation associated with the wear of scleral lenses of different diameters. Cont Lens Anterior Eye. 2019 Feb;42:104-110.
9. Caroline PJ, André MP. Does IOP increase during scleral lens wear? Contact Lens Spectrum. 2019 Sep;34:52.
10. Nau CB, Schornack MM, McLaren JW, Sit AJ. Intraocular Pressure After 2 hours of Small-Diameter Scleral Lens Wear. Eye Contact Lens. 2016 Nov;42:350-353.