Handling Irregular Corneas with Scleral Contact Lenses

Usage is an excellent alternative for effective visual rehab in these patients

Fully scleral contact lenses are a good option for achieving effective visual rehabilitation in irregular corneas and they have been extensively used though there is need to build up more awareness around them.
2 subgroups were earlier identified in types of scleral lenses depending upon the presence of corneal bearing or not: corneo-scleral or semi-scleral are their names. Just recently, the Scleral Lens Education Society (SLS) has defined a much more accurate differentiation between different types of scleral lenses not only based on the lens diameter, but also on the size of visible iris of the eye in which the lens is fitted, as has been outlined in Table 1 above.
SLS sustains public education that highlights the benefits and availability of scleral contact lenses to promote their usage.
Scientists found that fully scleral lens of a particular diameter can behave as mini-scleral or large-scleral, depending on the eye on which it is fitted.
This sort of lens has to always be fitted after being entirely filled with saline solution, staying clear of the formation of bubbles through the insertion that eventually can bring about discomfort and poor vision in the patient.
Scleral contact lenses have actually always been considered suitable for the correction of irregular astigmatism (post-corneal refractive surgical procedure, post-keratoplasty), including keratoconus as well as various other ectatic problems, as they have the ability to neutralise the effects of abnormalities with the tear film meniscus that develop with the cornea, while preserving high levels of comfort.
Nonetheless, there are also other symptoms viable for corneo-scleral as well as fully scleral contact lenses, such as the correction of refractive errors that cannot be dealt with satisfactorily with rigid gas-permeable (RGP) corneal or soft contact lenses, the introduction of prismatic corrections, for cosmetic functions as well as also in healthy corneas, due to the advantages of this type of lens: much less palpebral interaction, great convenience as conjunctitival sensitivity is lower than that of the cornea, no chances of producing corneal distortion if the fitting is adequate as well as a streamlined fitting procedure.
Additionally, the procedure of insertion and removal of the lens is simplified by the use a suction cup, avoiding the fingers coming in contact with the eye at all times.

The scleral Contact lens ICD
The ICD16.5 contact lens is a fully scleral contact lens that has four differentiated zones enabling a proper centration with no corneal touch and also a stable positioning over the conjunctiva.
These zones are: Central clearance zone (CCZ), Peripheral Central clearance zone (PCCZ), limbal clearance zone (LCZ), and also scleral landing zone (SLZ).
The geometry of these zones can be customized to accomplish a best fitting of the lens independently from the corneo-scleral profile.
Similarly, a peripheral toricity can be added if the conjunctival-scleral profile presents a significant level of astigmatism or to stabilise a scleral lens with toric power to make up for recurring astigmatisms through fitting.
This contact lens is fitted considering the sagittal elevation rather than keratometry that can be determined using optical coherence tomography (OCT), Scheimpflug video cameras, or more accurately with corneo-scleral topographers, such as the Eye Surface Profiler (ESP).
A central vault of around 300 µm is needed for providing a suitable fitting, without any corneal bearing while wearing because of a potential conjunctival compression of the lens (Figure 2).
This lens is an RGP contact lens manufactured in product HDS 100.
The product made use of is a thermoset fluorosilicone acrylate copolymer derived primarily from methylmethacrylate, trifluoroethyl methacrylate, and siloxane acrylate with a water content of less than 1% (Paflufocon D), with a Dk (oxygen permeability measure) of 100 Fatt (the unit of measure).

Results with scleral lens ICD16.5
The group carried out a study to assess outcomes achieved with the fully scleral contact lens ICD16.5 in corneas with different sorts of problems.
The research was consecutive and prospective.
The research consisted of a total of 42 eyes of 27 patients, 15 males (55.6%) and 12 females (44.4%).
The average age of patients in the study was 39 ± 12 years (range, 14 to 65 years).
Inclusion requirements for the research were that the participants had no active ocular disease, no severe dry eye, no previous intolerance to soft or corneal gas permeable contact lenses, and also they likewise accepted and signed informed consent papers.
A pre-fitting assessment is also confirmed to be a useful step in the procedure, and the study results bear this out.
In all cases, a very total pre-fitting assessment was carried out that included: filiation data, uncorrected and also corrected visual acuity, manifest refraction, eye aberration measurements, biomicroscopy, corneal topography, as well as previous anterior section evaluation by optical coherence tomography.
The patient was evaluated after 1, 3, 6 months and 1 year of contact lens wear to check the success of the fitting.
In our study, a total number of 25 eyes with keratoconus (59.5%) were fitted, four of them with previous implantation of intra-corneal ring segments and also 10 with previous corneal collagen cross-linking, 6 eyes with irregular cornea after previous LASIK surgery (14.3%), two eyes with irregular cornea after radial keratotomy surgical treatment (4.8%), three eyes after keratoplasty (7.1%), one eye with endothelial corneal decompensation (2.4%), two cases of dry eye (4.8%), as well as 2 eyes with nearsightedness magna (4.8%).
The mean sagital height required for the fitting was 4294.12 ± 292.56 Î 1/4 m (4,000 to 4,900 Î 1/4 m) and the mean optical power was – 6.96 ± 6.95 D (- 21 to +4 D).
After 1 hour of using the lenses, the mean apical vault determined by optical coherence tomography was 299.4 ± 85.56 Î 1/4 m (201 to 420 Î 1/4 m).
Concerning the visual outcomes, a considerable renovation in decimal visual acuity was achieved with the contact lens after 1 month of wearing compared to that acquired with eyeglasses prior to fitting (p < 0.001), without substantial modifications occurring during the remainder of the follow up (Figure 3).
This follows the results of previous researches making use of the very same version or various other versions of scleral contact lenses.

There was a propensity to an increasing positive over-refraction throughout the follow up, although it did not get to statistical significance (p = 0.17).
This adjustment followed a minor anterior (p = 0.91) and also posterior corneal flattening (p = 0.37), which did not get to either statistical significance.
Moreover, the noted change is in agreement with current research studies reporting the level of corneal molding induced by fully scleral contact lenses.
In our research, we found that a small yet statistically significant pachymetric increase was also observed at 3 months of wearing (minimum thickness p = 0.001, central thickness p = 0.08), without considerable changes later (minimal thickness p = 0.86, central thickness p = 0.88).
This minimal pachymetric increase has been reported by various other authors and does not seem to be related to issues of clinically relevant hypoxia as high Dk material has been utilized.
It was concluded in a prospective research study that, although a small percentage of corneal swelling was induced following 8 hrs of mini-scleral lens wear (generally <2%), modern high Dk (measure of permeability) mini-scleral contact lenses that vault the cornea do not generate clinically significant corneal edema (swelling) or hypoxic-related posterior corneal curvature changes during short-term wear.
Concerning ocular high-order aberrations, there was a considerable decrease, especially of the primary coma, as shown in Figure 4. This additionally has actually shown to be consistent with the considerable gain in fixed range visual acuity that has been attained with the contact lens.
The tolerance of the contact lens was good in all cases, with the following issues or difficulties reported:.
– Abandonment of fitting: 3 cases (6.8%) due to bad tolerance as a consequence of an excessive lens indentation throughout the day.
– Lens power changes needed throughout the first month (8 cases, 18.2%).
– Changes of the scleral landing zone due to lens fogging (5 cases, 11.4%) or too much scleral indentation (2 cases, 4.5%).
– Episodes of occasional conjunctival hyperemia (tobradex, thealoz, recugel) (5 instances, 11.4%).
Conclusions
In conclusion, the fully scleral contact lens ICD16.5 is a good choice for attaining an effective visual rehab in irregular corneas, specifically if previous fittings with other kinds of contact lenses have fallen short.
This kind of lens has the ability to provide a significant increase in visual acuity combined with a considerable improvement in visual acuity, maintaining high levels of comfortability.
The fitting process of these lenses is fairly easy and can be highly optimized by introducing the proper changes in the different zones of the lens.

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