Classification corneal cross linking procedure
Classification corneal cross linking procedure is helpful to people seeking keratoconus treatment, keratoconus doctors and researchers.
When a person needs to choose a doctor providing the latest keratoconus treatment, it is important to understand what treatment is being offered. Sometimes the cheapest may not be best. It can be confusing with lot of medical jargon. Also each keratoconus doc may claim his unique version is the best.
When researchers and Keratoconus surgeons present data and want to compare results, a scientific classification helps.Further innovation can occur along each arm of the classification system.
Cornea Collagen Cross linking or CXL
Cross linking with Riboflavin C3R Cross linking with Rose Bengal C3RB
- Epithelium OFF
- Epithelium on
- Cornea Channel
This is the classic method described By Wollensack et al. Traditionally the epithelium is removed by a chemical like tetracaine or ethyl alcohol. Laser epithelium removal (PTK) is a new variant.
This innovative method was first described by Dr.Boxer-Wachler. The epithelium is irritated to break tight junctions to allow riboflavin(chromophore) to pass.
This is a combination method. At the time of making corneal channel for intacs, riboflavin can be instilled in the channels. Thus riboflavin loading can occur more effectively and rapidly while preserving the epithelium. Since the UVA wavelength is able to pass through the intact epithelium, it may work.
CHROMOPHORE (RIBOFLAVIN) SOAKING TIME
- 30 min
The conventional Dresden protocol require s30 minute soaking time. Riboflavin with dextran is used.
Dextran free formulations may allow faster penetration of riboflavin through the cornea in to the anterior chamber of the eye.
For epi on cornea cross linking procedures a longer soaking time may be needed. This may be upto 60 minutes and rarely more. The end point is flare in the anterior chamber.
UV RADIATION TIME
- 30 min
- 10 min
- 6 min
This is the gold standard time with 3 mw/cm2 power. This combination gives the best cross linking effect.
When the power is increased to 9 mw/cm2 only 10 minutes of UV radiation time is required. This is known as accelerated cornea cross linking, The results are comparable to classical cross linking.
As the power is increased further the time of UV exposure decreases. At 18mw/cm2 it is only 6 minutes. The effectiveness is less than the classical treatment time.
Oxygen gets depleted during the cross linking process in the cornea. Adding oxygen may increase speed and effectiveness of the procedure.
This is a method using ions to transport Riboflavin across an intact epithelium,
Another strategy to overcome the oxygen depletion. The UV light is pulsed to allow oxygen to regenerate.
The above Classification corneal cross linking procedure is based on and similar to the one proposed by Dr. Hafezi, Randelmann et al.