Corneal crosslinking is currently the standard in terms of halting/slowing the progression of corneal thinning diseases such as keratoconus. The cornea is made up of many thin layers of clear sheets that lay on top of one another. Crosslinking refers to the adhesions between these sheets, which strengthen them structurally.

As we age, our corneas naturally become crosslinked and more structurally “rigid.”  But for patients that develop diseases that thin the cornea at a younger age (e.g. keratoconus, PMD, or post-LASIK/PRK/RK complications), accelerating this natural crosslinking effect allows the cornea to maintain more structural integrity.

Corneal crosslinking is an FDA-approved, outpatient procedure that increases the cross-linked nature of the cornea. Even though it’s extremely effective in slowing the progression of keratoconus, it cannot undo or reverse any damage that occurred before the procedure, it can only “lock” it in place.

Corneal crosslinking is the ideal treatment for patients whose corneas are still weakening/thinning. This in-office procedure may require a small amount of corneal tissue to be removed (don’t worry, it grows back quickly!), depending on the subtype of corneal crosslinking procedure that’s required. A special solution is instilled into your eye, which is subsequently activated with UV light, which results in more crosslinking between your corneal layers. The focus of this procedure is structural stability, which means that the majority of patients may not experience a change in vision afterward. The main goal of corneal crosslinking is to eliminate/reduce the progression and then to provide clarity with other treatment means, such as scleral lenses. We team up with corneal specialists to provide the pre and post-operative care that’s necessary for corneal crosslinking.

INTACTS is an FDA-approved, minimally invasive surgical option used to treat mild forms of keratoconus. With keratoconus, the structural fibers of the cornea begin to thin and weaken, which leads to frontal bowing of the cornea. The bowed area of the cornea becomes more cone-like in the area of weakness, hence the name of the disease, keratoconus.

INTACTS alleviate some of the corneal bowing (the cone-like formation) that results from keratoconus through structural relief. In this outpatient procedure, a thin channel is created between specific layers of the cornea and biocompatible rings are inserted into those channels. With the rings in place, the cornea is relieved of the strain on the bulged area of the cornea, reducing the amount of bowing and shape irregularity. Under most conditions, INTACTS can reduce some of the effects of keratoconus, but it does not alter its progression. For most patients, assistance with scleral lenses, contact lenses, or glasses is still necessary to see clearly.

An implantable collamer lens (ICL) is a biocompatible lens that is implanted inside of the eye to reduce large degrees of myopia (which leads to nearsightedness) and hyperopia (which leads to farsightedness). Most patients are aware of lenses that are worn on the eye, but an ICL is different in that it is implanted inside of the eye. It’s implanted between the iris (the colored portion of the eye) and the crystalline lens (which is the lens on the inside of the eye behind the iris).

One’s candidacy for an ICL depends on a few factors. First, patients with keratoconus must no longer be progressing, either through natural aging or through an accelerated corneal crosslinking procedure. Second, the severity of keratoconus cannot exceed that of mild to mild-moderate, as ICLs are unable to correct for corneal distortion or astigmatism that results from keratoconus. The residual corneal distortion and astigmatism must then be corrected with a contact lens (scleral lenses, hybrids, or GPs).  

TG-PRK is a non-FDA approved procedure that is used to reduce corneal irregularity and distortion that results from keratoconus. PRK is typically used to correct myopia and astigmatism in eyes without keratoconus, but it can also be adapted for use with keratoconus. For patients without keratoconus, a guided laser is utilized to remove corneal tissue in order to reduce the patient’s prescription to near-zero. When TG-PRK is utilized for patients with keratoconus, the treatment goal is not to aim for a prescription of zero, as there may be a catastrophic loss of corneal tissue and structural integrity. Instead, TG-PRK aims to reduce the irregularity of the corneal surface, leading to a reduction in visual distortion. Corneal crosslinking is typically performed prior to TG-PRK to ensure a stable corneal canvas. 

In terms of treatment modalities, TG-PRK is still non-FDA approved for keratoconus. 

A corneal transplant is an FDA-approved procedure in which damaged corneal tissue is replaced with donor corneal tissue. Corneal transplants fall into two varieties. Traditional “full-thickness” corneal transplants involve the removal of the entire depth of the cornea. The removed cornea is then replaced with a donor cornea. For our review, we will focus on the newer form of corneal transplants, specifically Deep Anterior Lamellar Keratoplasty (DALK). DALK differs from full-thickness corneal transplants in that only the damaged or scarred front half of the cornea is replaced, leaving the patient’s original back half of the cornea intact.

Despite replacing damaged tissue with a healthy donor, corneal transplants still present a few issues. First, corneal transplant surgery serves to replace diseased tissue, not necessarily to enhance vision. Second, transplanted tissue carries a risk of immune rejection and corneal transplants are no different in this regard (although with a lower rejection rate with DALK over full-thickness transplants). Lastly, the recipient of a corneal transplant must still utilize other forms of correction in order to see clearly (scleral lenses, hybrid lenses, and to a lesser extent, gas permeable lenses and glasses).