Eye Care

Fitting Keratoconus

Keratoconus is a bilateral non-inflammatory corneal ectasia with an incidence of approximately 1 per 2,000 in the general population (1). The treatment of Keratoconus can be implemented by the use of spectacle lenses, contact lenses of various kinds and surgery.

In more advance Keratoconus cases where severe irregular astigmatism with resultant higher order aberrations are present, the use of Rigid Gas Permeable (RGP) lenses are indicated to restore the patients vision.  Unfortunately in some Keratoconus cases, contact lens intolerance develops and many patients consider Penetrating Keratoplasty (cornel graft). Lim, et al found that 83% of patients opting for Penetrating Keratoplasty was due to intolerance to contact lens wear (2).

However, Smiddy, et al found that 87% of the Keratoconus cases referred for Penetrating Keratoplasty to the Wilmer Institute at the Johns Hopkins Medical Institution could be successfully refitted with contact lenses.  Of the successfully fitted cases ultimately 31% needed keratoplasty after an average of 38.4 months of lens wear and 69% did not require Keratoplasty over an average follow-up interval of 63 months of wearing contact lenses.

Of the postoperative penetrating Keratoplasty eyes 60% had to wear contact lenses for best vision. Their conclusion was that Penetrating Keratoplasty can be delayed or avoided in many Keratoconus patients by using proper fitting contact lenses and further that Keratoconus eyes often need contact lenses after Keratoplasty (3).

Piggyback system

One option to improving the comfort of RGP lenses on Keratoconic and irregular corneas is to use a piggyback system. A piggyback system comprises of a soft contact lens first placed on the cornea and then followed by a RGP lens fitted on top of the soft lens.  With the birth of Silicone Hydrogel soft lenses and hyper DK RGP materials, piggyback systems have become a safe and viable option for vision correction of the compromised cornea. Tsubota, et al found that the oxygen pressure under piggybacked oxygen-permeable hard contact lenses was 95 +/- 14 mmHg after 5 minutes wear which was almost three times higher than the 34 +/- 14 mmHg when PMMA and low water-content lenses were used (4). Clare O'Donnell first reported on the fitting of a hyper-Dk piggyback contact lens system in Keratoconus and other irregular corneas in 2004 (5).

Eye care has seen a massive explosion of new diagnostic instruments and treatment procedures in the last number of years.  From instruments like the front and back chamber OCTs, Oculus Pentacam and Zeiss GDx to procedures like Intra ocular injections to halt the progression of previously untreatable wet macular degeneration, 30 days continues wear silicone soft contact lenses, Orthokeratology and also Corneal Collagen Cross-linking (CxL).

People who have Keratoconus are particular excited about the possibility of having Corneal Cross-linking done to their eyes in the hope of improving their sight.  It is however very important to stress that CxL is not a cure for keratoconus.  The main function of the procedure is only to halt the progression of the ectasia (bulge or cone on the cornea).  A couple of months after the procedure some flattening of the cone can occur, but this is not significant enough for the keratoconus patient to have normal sight without the use of other optical devices like Rigid Gas Permeable contact lenses.

For this reason it is not a necessity for all Keratoconus patients to have the Corneal Collagen Cross-linking procedure.  The keratoconus group that will benefit the most from CxL is the ones who develop keratoconus at a young age, normally between the ages of 16 to 28, and show quick thinning and progression of the keratoconus cone. 

Corneal collagen Cross-linking has been available in South Africa for a while but has only recently become available in the United States and Drs James Owen and William Tullo wrote a comprehensive article about CxL for the August edition of the US based Contact Lens Spectrum titled:

A Closer Look at Corneal Cross-Linking

The first treatment to halt the progression of corneal ectasia may soon be available in the United States. Although corneal collagen cross-linking (CXL) is currently available in most countries around the world, the majority of patients in the United States who have keratoconus must wait to access this technology. This procedure is exciting because it will allow for successful contact lens fitting of patients who might otherwise become contact lens intolerant.

One of the most common visual side effects of Post LASIK patients is halo's and ghosting which is more pronounced during low light levels. These visual disturbances are called higher order aberrations (HOA).   In the opinion of contact lens fitters, many patients find relief of the higher order aberrations and improvement of their visual acuity when they wear Rigid Gas Permeable (RGP) lens fitted over the Laser treated corneal area. 

I recently read this research paper titled 'Changes in wave-front aberrations after rigid gas permeable contact lens fitting in post-laser in situ keratomileusis patients with visual complaints' published in Can J Ophthalmol. 2010 Jun;45(3):264-8.

The authors were Tan G, Yang J, Chen X, He H, Zhong X

Intrastromal rings or Intacs broke into the ophthalmic market with a big bang and was hailed as a savior surgical procedure for Keratoconus patients.  The idea is to implant two semi circular rings into the tissue of the cornea on opposite sides of the keratoconus ectasia (protrusion of corneal tissue).  The mechanical effect of the Intact rings is to stretch the corneal tissue and in the process flatten the ectasia point of the Keratoconus.

Unfortunately the surgery outcome of the Intrastromal rings hasn't been as good as expected and very few patients achieve normal functional sight after the procedure.  Another complication is post op infections of the procedure as highlighted on this case study.

A 20-year-old woman presented with photophobia, decreased vision, and pain 11 days after uncomplicated implantation of intrastromal corneal ring segments (ICRSs) for keratoconus in both eyes. Bilateral corneal stromal infiltrates were noted at the site of ICRSs implantation. The patient was started on frequent topical fortified antibiotics in both eyes. Despite aggressive medical management, stromal infiltrates progressed, necessitating removal of ICRSs from both corneas to control infectious keratitis and melting of cornea.

Cultures obtained at the time of initial presentation yielded Streptococcus viridans. Patient responded well to the treatment and was left with stromal scars in both corneas.

One of the key active ingredients used in the production of the product has been discontinued and we have been unable to source an alternative option.

• Bausch & Lomb Conditioning Solution and Concentrated Cleaner was discontinued
• Customers are being transitioned to  Boston Advance Cleaning Solution and Boston Advance Conditioning Solution