Corneal Hypoxia happens when there is lack of oxygen in the cornea. This is primarily caused by wearing lenses with low oxygen permeability (Dk level) over an extended period of time. Good thing is that high Dk lenses made of soft materials such are silicone hydrogel are now widely available in the market. Some approved lenses with high DK levels and soft materials can be continuously worn for 30 nights without causing problems. However, checking the label first prior to continuous wear may be necessary to make sure that the product is intended, recommended or allowed to be used continuously over an extended period of time.
Corneal hypoxia symptoms include:
- redness and dryness around the cornea
- light sensitivity and blurred vision
- tearing and inflammation within the eyes
- corneal vascularization and conjunctival staining
- double vision
- general sense of discomfort
Other than these subjective corneal hypoxia symptoms, dilation of vessels in the eye may also be observed among sufferers. In some cases, pupillary muscles paralysis may also be incurred .
While continuous wear of low oxygen permeability (low Dk) lenses is primarily responsible for corneal hypoxia symptoms, wearing lenses with a non-silicone hydrogel material can also be a factor. However, permeable lenses made of rigid gas has been known to provide less risk for corneal hypoxia as long as the lenses have a high Dk level. 
Qualified eye experts may recommend various treatments depending on the symptoms present and the degree of damage present in the eye. If corneal neovascularization secondary to corneal hypoxia is present, some of the treatments patients may undergo include :
prescription of anti-inflammatory drugs and enzyme inhibitors like NORFLO, a product designed to fight inflammation
surgery such as photodynamic therapy
laser ablation, diathermy and cautery
However, it should be noted that treatment or therapy is given on a case-to-case basis and may only be recommended by medical practitioners. In some cases, patients may be advised to discontinue their use of contact lens while symptoms are present. Use of another type of lens with a different material such as scleral lenses or high-Dk rigid gas permeable lenses may also be recommended.
- Sanders and Hoyt (1969). Hypoxic ocular sequelae of carotid-cavernous fistulae. Retrieved from http://bjo.bmj.com/content/bjophthalmol/53/2/82.full.pdf
- Covey, Sweeney, Terry, Sankaridurg and Holden (2001). Hypoxic Effects on the Anterior Eye of High-Dk Soft Contact Lens Wearers Are Negligible. Optometry and Vision Science: February 2001 – Volume 78 – Issue 2 – p. 95-99. Retrieved from https://journals.lww.com/optvissci/Fulltext/2001/02000/Hypoxic_Effects_on_the_Anterior_Eye_of_High_Dk.9.aspx
- Chiang, Hemmati, Scott, and Fekrat (2013). Treatment of Corneal Neovascularization. Retrieved from https://www.aao.org/eyenet/article/treatment-of-corneal-neovascularization