It’s officially Halloween season! Like most people, I enjoy getting the chance to decorate, dress up, and have excessive amounts of chocolate. I’m also a person that plans my costume months in advance! Lots of people are looking to spice up their costume with cosmetic contact lenses. Though their effect is visually striking, these contact lenses can have serious consequences ranging from dry eyes to infections, abrasions, and even permanent scarring or vision loss (including blindness). Here’s some information on how to keep your costumes spooky without risking damage to your eyes:
Contacts are clear, thin lenses used to correct vision, much like glasses do, and are specified to a person’s prescription (which can differ from their glasses)! They are also measured to find the right size and shape for your eyes. Contact lenses that fit poorly can damage the eyes, especially if worn for extended periods of time (1,2). Even contact lenses with the same measurements (such as base curve, diameter, etc), fit differently and varies between individuals (3,4,5). So you can't just take your prescription for a brand of contacts and order different ones with the same parameters - they fit differently!
The contact lens fits at the front of our eye, over the cornea. The cornea is the transparent outer layer of the eye which sits over the iris and pupil. This clear covering protects the structures of the eye and is responsible for two-thirds of our refractive power, so our vision depends on a healthy cornea! Oxygen is transmitted from the air around us to our cornea through our tears, and sufficient levels of oxygen for the cornea are imperative in maintaining both the health of our eyes and the clarity of our vision (6). Contact lenses reduce the amount of oxygen available to the eye! Like the rest of our body, if the cornea is starved of oxygen (hypoxia), it quickly becomes a horror story. This includes corneal swelling, blurred vision, pain, and dry eyes. This eventually can also cause vision loss, scarring, and neovascularization (the formation of small irregular blood vessels) (7). Interestingly, after these blood vessels have healed and drained, they’re called ghost vessels. So convenient for our Halloween blog!
Many different contact lens materials have been produced, starting with glass (OMG!) in the late 1800s, then plastic materials such as hydrogel in the 1960s, and silicone hydrogel in 1998. As one can imagine, these lenses have different levels of comfort. Additionally, they transmit different amounts of oxygen. This is measured as the “Dk” of the material.
Today there are many materials for soft contact lenses. Hydrogel was the prominent soft lens material for decades, and for a good reason. Hydrogel lenses are comfortable, easy to use, and can be made into most prescriptions. One of the other key factors was the amount of oxygen that was able to flow past the lens to the cornea, which allowed people to wear the contact lenses for longer with less hypoxia. This was related to the amount of water in the material. Though contact lenses are plastic, water is also present. Hydrogel lenses with higher water content allow more oxygen through the lens, and therefore have a higher Dk (8).
Then, in 1998 a new material, silicone hydrogel, was introduced and now accounts for almost 50% of prescribed contact lenses (9). Opposite from the hydrogel, Silicone hydrogel lenses with lower water content actually allow more oxygen through the lens (10). Even beyond that, there are many different silicone hydrogel lenses that all have varying amounts of water content, oxygen transmissibility, and much more. So when we see websites and stores promoting their lenses with a ‘high water content,’ this doesn’t necessarily mean that the lens is capable of giving the eye the oxygen it needs. Additionally, people who purchase lenses online can be at an increased risk of complications (11).
Studies have shown that the cornea needs a minimum of 24 Dk oxygen transmissibility before corneal swelling occurs (12). So how do cosmetic contact lenses stack up? The material used for most of these lenses is polymacon, which has a Dk of 9 (13). OOF! So when wearing these lenses, your cornea is being starved of oxygen. You only get one pair of eyes. Is it really worth it to risk them for your costume?
All of this being said, we know there are some of you who will use these contacts despite their risks. If you are going to wear them (please don’t!!), you can follow these guidelines to reduce your risk of infection and damage to your eyes.
1. Wear the lenses for only 3 hours or less
Since these lenses transmit less oxygen than the cornea needs to function, the less time on the eyes, the better!
2. Dispose of them immediately
If you NEED to reuse them (do you really, though?), use a proper cleaning solution and thoroughly clean the lens and store in a clean contact lens container
3. If your eyes are red, painful, or blurry, go see your eye doctor!
Yikes! Don’t worry, we are always here to help you regardless of what’s caused these problems. We don’t judge ;)
… But we hope you learned your lesson!
Thaer AA, Geyer OC. The application of confocal slit scanning microscopy to the in vivo study of corneal microstructure associated with contact lens wear. Contactologica. 1997; 19:158-77
Kilp H, Heisig B. Changes in glucose and lactate concentrations in rabbit tears mechanical irritation and contact lens wear. Graefes Arch Clin Exp Ophthalmol. 1975; 193: 259-67.
Wolffsohn JS, Hunt OA, Basra AK. Simplified recording of soft contact lens fit. Contact Lens Ant Eye. 2009; 32:37–42.
Tranoudis I, Efron N. In-eye performance of soft contact lenses made from different materials. Contact Lens Ant Eye. 2004;27:133–48.
Belda-Salmerón, L., Drew, T., Hall, L., & Wolffsohn, J. S. Objective analysis of contact lens fit. Contact Lens and Anterior Eye. 2015; 38(3), 163–167. doi:10.1016/j.clae.2015.01.006 ).
Sridhar M. S.. Anatomy of cornea and ocular surface. Indian Journal of Ophthalmology. 2018; 66(2), 190–194. https://doi.org/10.4103/ijo.IJO_646_17
SUCHECKI, J., DONSHIK, P., & EHLERS, W. Contact lens complications. Ophthalmology Clinics of North America. 2003; 16(3), 471–484. doi:10.1016/s0896-1549(03)00056-7
EFRON, N., MORGAN, P. B., CAMERON, I. D., BRENNAN, N. A., & GOODWIN, M.. Oxygen Permeability and Water Content of Silicone Hydrogel Contact Lens Materials. Optometry and Vision Science. 2007; 84(4), E328–E337. doi:10.1097/opx.0b013e31804375ed
Morgan PB, Woods CA, Tranoudis IG, et al. International contact lenses prescribing in 2011. Contact Lens Spectrum. 2012; 27:26–32.
Sweeney, D. F. Have Silicone Hydrogel Lenses Eliminated Hypoxia? Eye & Contact Lens: Science & Clinical Practice. 2013; 39(1), 52–59. doi:10.1097/icl.0b013e31827c7899
American Optometric Association. "Contact Lenses Purchased Over Internet May Place Individuals At Risk For Harmful Eyecare Practices." ScienceDaily. ScienceDaily, 7 January 2008.
Holden, B. A., & Mertz, G. W. Critical oxygen levels to avoid corneal edema for daily and extended wear contact lenses. Investigative ophthalmology & visual science. 1984; 25(10), 1161–1167.
Contact Lens Spectrum, Issue: 2010 Contact Lenses & Solutions Summary July 2010