Scleral lenses are lenses which are large in diameter, rigid, and gas permeable, ranging from 14 to more than 20 mm in their diameter. They’re called ‘scleral’ due to the fact that they totally cover the eye’s cornea, which is the clear tissue dome that covers up the eye’s colored part and they also extend onto the white part that forms the eye’s outer wall.
As lens designs like these have fully developed, so too have classification systems that describe these. A lot of these systems of classifications are based mostly on the size of the lens. On the other hand, many of these could also get classified based on their characteristics of fitting. A corneal lens is exclusively supported by the eye’s cornea, nor do they extend further than the limbus, which is the junction that happens between the sclera and the cornea. Another kind is corneoscleral lenses that the sclera and the cornea both support which go past the limbus. Scleral and mini-scleral lenses are both usually just called scleral lenses, which the sclera support as they cross the cornea and limbus.
What advantages do scleral lenses have?
Scleral lenses that are large in diameter offer advantages over corneal lenses. First and foremost, patients might find larger diameter lenses to be of more comfort than other corneal lenses. Of all body parts and tissues, the cornea is perhaps the most sensitive. However, the conjunctiva, which is the clear and soft tissue lying on top of the sclera is far less sensitive than corneal tissue, so any lenses resting solely or primarily on this part might impart less sensation on the eye as compared to corneal lenses. That makes scleral lenses very comfortable to wear for most patients.
In a number of patients, the corneal tissue gets damaged. Since scleral lenses don’t touch the actual cornea, it’s bathed all day long with saline that is preservative-free so the ocular surface can rejuvenate. Scleral lenses are able to extend under both the lower and upper lids, so they rarely dislocate. Scleral lenses have demonstrated stability and centration at excellent levels in most patients.
Who might stand to benefit from something like scleral lenses?
Any patient with irregular corneas, refractive errors (astigmatism, presbyopia, farsightedness, nearsightedness), inability to wear alternative forms of corrective lenses, and any condition that affects the tear film might be someone who can gain advantage from scleral lenses.
Conditions like keratoconus or pellucid marginal corneal degeneration are able to cause cornea irregularities. Surgery like refractive surgery or keratoplasty might also lead to corneal irregularities. When a cornea isn’t smooth, then vision isn’t as easily corrected with the majority of soft contact lenses or any spectacles. Scleral lenses are able to mask such irregularities and provide a smoother front surface for improved vision.
A number of patients have various disorders that might impact the quantity of tears or their quality, which hurts the eye’s surface in terms of its health and smoothness. Dry eye syndrome, Sjogren’s syndrome, neurotrophic keratopathy, Stevens Johnson syndrome, and graft vs. host disease are all such instances. A number of inflammatory conditions such as ocular cicatricial pemphigoid and limbal stem cell deficiency are also things that cause severe damage to an eye’s front surface. Patients that are unable to completely close their lids might also suffer from health problems regarding their eye surfaces. A scleral lens often has a fluid reservoir underneath it that can enhance comfort, possibly even letting a corneal surface heal.
Patients that need their vision corrected but can’t wear different contact lenses might just find that scleral lenses are quite a bit more comfortable than alternative lens designs.
How long have scleral lenses been around?
Scleral lenses were actually among the first contact lenses which medical literature of the late 1800s described. On the other hand, these lenses failed to gain popularity at the time, largely due to challenges in manufacturing and the lack of ability to transmit oxygen through the early lenses that were produced. Over the course of the following century, though, both soft contact lenses and corneal rigid gas permeable lenses increased in their popularity.
Soft lenses and corneal rigid gas permeable lenses didn’t solve all the issues of corneal irregularity or other eye diseases. Scleral lenses saw a large increase in their popularity in the 1980s when high-oxygen materials became more readily available, so the lenses were able to be manufactured reliably and with increasingly sophisticated designs.