Optical Lens Tinting and Wavelength-Specific Filters

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Review:
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 by Claudia Prospero Ponce, MD on September 13, 2020.


Topic

Optical lens tinting and wavelength-specific filters

Description

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.[1] They are designed to block specific wavelengths of light that were observed to induce photophobia by dying the lens.[2] 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.[3]

Mechanism of efficacy

Wavelength-specific blockade functions by reducing the amount of light that activates phototransduction in intrinsically photosensitive retinal ganglion cells (IPRGC).[2] 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.[4][5] Stimulation of these cells has been linked to circadian rhythms, the pupillary light reflex, and nociceptive centers in the thalamus.[4][5][6] 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.[7] 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.[6]

Clinical applications

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[3], post-concussion syndrome (PCS)[8][9], benign essential blepharospasm (BEB)[10], and disorders of cone photoreceptors.[11][12] 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.[8] In migraine and BEB, wavelength blockade around 480nm has shown efficacy.[3][10] It is important to block blue-green light[13]. FPCS patients have reported improved comfort subjectively with a variety of lenses, but the trials have been small.[8] 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.[11][12] 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.[2][14]

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 legit.

References

  1. 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. 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. 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. 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. 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. 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
  7. 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. 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
  9. 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
  10. 10.0 10.1 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
  11. 11.0 11.1 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
  12. 12.0 12.1 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
  13. Anderson, R.L. et al. Ophthal Plast Reconstr Surg 1998; 14:305-317.
  14. 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