Optical Lens Tinting and Wavelength-Specific Filters
Optical lens tinting and wavelength-specific filters
Optical lens tinting is a technique used in the treatment of a variety of conditions that cause significant patient discomfort from photophobia. It was first developed in the late 1980’s with the first successful lens being dubbed the FL-41 lens designed to improve productivity in the workplace secondary by mitigating discomfort from fluorescent lighting. They are designed to block specific wavelengths of light that were observed to induce photophobia by dying the lens. More recently, optical notch filters have been developed that operate by the same principle; however, instead of tinting the original lens, a thin film is applied over the lens that provides a more specific wavelength blockade.
Mechanism of efficacy
Wavelength-specific blockade functions by reducing the amount of light that activates phototransduction in intrinsically photosensitive retinal ganglion cells (IPRGC). These cells are dubbed “intrinsically photosensitive” because they have been shown to transduce light signals even in the absence of traditional rod and cone photoreceptors. Stimulation of these cells has been linked to circadian rhythms, the pupillary light reflex, and nociceptive centers in the thalamus. IPRGCs contain a pigment called melanopsin that is bi-stable, isomerizing between its all-trans and 11-cis forms when exposed to light of 481nm and 587nm, respectively. Isomerization of this pigment is thought to be implicated in the IPRGC phototransduction pathway, so blockade of light with a wavelength around 481nm is theorized to reduce IPRGC phototransduction. This is clinically applicable in a patient with photophobia, because it may prevent activation of thalamic pain centers that would have normally been activated by the 481nm component of ambient light.
Photophobia is a prominent feature of many conditions, but wavelength-specific light filtering has not been studied in all of them. Prominent disorders that have been researched include migraine, post-concussion syndrome (PCS), benign essential blepharospasm (BEB), and disorders of cone photoreceptors. The filters have not been shown to help with efferent problems (e.g. convergence insufficiency or reading speed in PCS), but have shown a great deal of promise mitigating symptoms of photophobia which often affect patients’ quality of life. In migraine and BEB, wavelength blockade around 480nm has shown efficacy. It is important to block blue-green light. FPCS patients have reported improved comfort subjectively with a variety of lenses, but the trials have been small. Though also limited by sample size, patients with cone disorders have shown the most convincing improvement, and the treatment studied for them was using red contact lenses. The trials across all diseases have been limited by relatively small sample size, but a majority show objective improvement in patient symptoms, and they almost universally show a subjective improvement in symptoms.
Barriers to implementation
Barriers to implementation include low availability in optical shops and awareness of tinted lenses as a treatment option by physicians. Tinted lenses are available online, but they may be expensive, and this limits patients’ ability to trial the glasses before buying them.
Some commercially available lenses/glasses are labeled FL-41 and do not work as FL-41 protection. One must be careful and make sure the supplier is legitimate.
- ↑ Wilkins AJ, Wilkinson P. A tint to reduce eye-strain from fluorescent lighting? Preliminary observations. Ophthalmic Physiol Opt [Internet]. 1991 Apr [cited 2019 Jul 19];11(2):172–5. Available from: http://www.ncbi.nlm.nih.gov/pubmed/2062542
- ↑ 2.0 2.1 2.2 Katz BJ, Digre KB. Diagnosis, pathophysiology, and treatment of photophobia. Surv Ophthalmol [Internet]. 2016 Jul 1 [cited 2019 Jul 19];61(4):466–77. Available from: http://www.ncbi.nlm.nih.gov/pubmed/26875996
- ↑ 3.0 3.1 3.2 Hoggan RN, Subhash A, Blair S, Digre KB, Baggaley SK, Gordon J, et al. Thin-film optical notch filter spectacle coatings for the treatment of migraine and photophobia. J Clin Neurosci [Internet]. 2016 Jun [cited 2019 Jul 19];28:71–6. Available from: http://www.ncbi.nlm.nih.gov/pubmed/26935748
- ↑ 4.0 4.1 Berson DM, Dunn FA, Takao M. Phototransduction by retinal ganglion cells that set the circadian clock. Science [Internet]. 2002 Feb 8 [cited 2019 Jul 20];295(5557):1070–3. Available from: http://www.ncbi.nlm.nih.gov/pubmed/11834835
- ↑ 5.0 5.1 Hattar S, Liao HW, Takao M, Berson DM, Yau KW. Melanopsin-containing retinal ganglion cells: architecture, projections, and intrinsic photosensitivity. Science [Internet]. 2002 Feb 8 [cited 2019 Jul 20];295(5557):1065–70. Available from: http://www.ncbi.nlm.nih.gov/pubmed/11834834
- ↑ 6.0 6.1 Noseda R, Kainz V, Jakubowski M, Gooley JJ, Saper CB, Digre K, et al. A neural mechanism for exacerbation of headache by light. Nat Neurosci [Internet]. 2010 Feb 10 [cited 2019 Jul 19];13(2):239–45. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20062053
- ↑ Mure LS, Cornut P-L, Rieux C, Drouyer E, Denis P, Gronfier C, et al. Melanopsin Bistability: A Fly’s Eye Technology in the Human Retina. Egles C, editor. PLoS One [Internet]. 2009 Jun 24 [cited 2019 Jul 20];4(6):e5991. Available from: https://dx.plos.org/10.1371/journal.pone.0005991
- ↑ 8.0 8.1 8.2 Jackowski MM, Sturr JF, Taub HA, Turk MA. Photophobia in patients with traumatic brain injury: Uses of light-filtering lenses to enhance contrast sensitivity and reading rate. NeuroRehabilitation [Internet]. 1996 [cited 2019 Jul 19];6(3):193–201. Available from: http://www.ncbi.nlm.nih.gov/pubmed/24525771
- ↑ Fimreite V, Willeford KT, Ciuffreda KJ. Effect of chromatic filters on visual performance in individuals with mild traumatic brain injury (mTBI): A pilot study. J Optom [Internet]. 2016 Oct [cited 2019 Jul 19];9(4):231–9. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27257034
- ↑ Herz NL, Yen MT. Modulation of sensory photophobia in essential blepharospasm with chromatic lenses. Ophthalmology. 2005 Dec;112(12):2208-11. doi: 10.1016/j.ophtha.2005.06.030. Epub 2005 Oct 19. PMID: 16242188.
- ↑ 11.0 11.1 Adams WH, Digre KB, Patel BCK, Anderson RL, Warner JEA, Katz BJ. The Evaluation of Light Sensitivity in Benign Essential Blepharospasm. Am J Ophthalmol [Internet]. 2006 Jul [cited 2019 Jul 19];142(1):82-87.e8. Available from: http://www.ncbi.nlm.nih.gov/pubmed/16815254
- ↑ 12.0 12.1 Rajak SN, Currie ADM, Dubois VJP, Morris M, Vickers S. Tinted Contact Lenses as an Alternative Management for Photophobia in Stationary Cone Dystrophies in Children. J Am Assoc Pediatr Ophthalmol Strabismus [Internet]. 2006 Aug 1 [cited 2019 Jul 20];10(4):336–9. Available from: https://www.sciencedirect.com/science/article/pii/S1091853106003326
- ↑ 13.0 13.1 Park WL, Sunness JS. Red contact lenses for alleviation of photophobia in patients with cone disorders. Am J Ophthalmol [Internet]. 2004 Apr 1 [cited 2019 Jul 20];137(4):774–5. Available from: https://www.sciencedirect.com/science/article/pii/S0002939403011498
- ↑ Anderson, R.L. et al. Ophthal Plast Reconstr Surg 1998; 14:305-317.
- ↑ Lee EY, Emami S, Cho R, Ing E. Availability of FL-41 lens tint in Toronto and Vancouver. Can J Ophthalmol [Internet]. 2018 Oct [cited 2019 Jul 19];53(5):e169–70. Available from: http://www.ncbi.nlm.nih.gov/pubmed/30340731