Ophthal. Physiol. Opt. 2002 22 68±77 Do tinted lenses or ®lters improve visual performance in low vision? A review of the literature Frank Eperjesi1,2, Colin W. Fowler1 and Bruce J. W. Evans3 1Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK, 2Low Vision Centre, Birmingham Focus on Blindness, 62 Woodville Road, Harborne, Birmingham B17 9AX, UK and 3The Institute of Optometry, 56-62 Newington Causeway, London SE1 6DS, UK Abstract This is a review of studies that have investigated the proposed rehabilitative bene®t of tinted lenses and ®lters for people with low vision. Currently, eye care practitioners have to rely on marketing literature and anecdotal reports from users when making recommendations for tinted lens or ®lter use in low vision. Our main aim was to locate a prescribing protocol that was scienti®cally based and could assist low vision specialists with tinted lens prescribing decisions. We also wanted to determine if previous work had found any tinted lens/task or tinted lens/ocular condition relationships, i.e. were certain tints or ®lters of use for speci®c tasks or for speci®c eye conditions. Another aim was to provide a review of previous research in order to stimulate new work using modern experimental designs. Past studies of tinted lenses and low vision have assessed effects on visual acuity (VA), grating acuity, contrast sensitivity (CS), visual ®eld, adaptation time, glare, photophobia and TV viewing. Objective and subjective outcome measures have been used. However, very little objective evidence has been provided to support anecdotal reports of improvements in visual performance. Many studies are ¯awed in that they lack controls for investigator bias, and placebo, learning and fatigue effects. Therefore, the use of tinted lenses in low vision remains controversial and eye care practitioners will have to continue to rely on anecdotal evidence to assist them in their prescribing decisions. Suggestions for future research, avoiding some of these experimental shortcomings, are made. Keywords: adaptation, age-related macular degeneration, colour vision, contrast sensitivity, ®lters, glare, low vision, photophobia, retinitis pigmentosa, rehabilitation, tinted lenses, visual acuity, visual ®eld albinism. This review will concentrate on studies that Introduction have investigated the use of tinted lenses in the Tinted lenses are currently used by eye care practition- rehabilitation of people with visual loss, and highlight ers to assist people with low vision in maximising use of areas where more research would be useful. Proposed residual vision, improve visual function, control glare eects of tinted lenses on progressive eye disease and improve orientation and mobility skills. Tinted (especially RP) are controversial and will not be lenses are often prescribed to people with various ocular discussed here. diseases, including age-related macular degeneration (ARMD), retinitis pigmentosa (RP), cataract, diabetic Terminology retinopathy, cone dystrophy and oculo-cutaneous Terminology in this ®eld can be confusing. The following de®nitions are after Millodot (1999). Glare-a Received: 17 February 1998 Revised form: 6 December 2000 visual condition in which the observer feels either Accepted: 4 July 2001 discomfort and/or exhibits a lower performance in Correspondence and reprint requests to: Frank Eperjesi. visual tests. Photophobia-abnormal fear or intolerance E-mail address: [email protected] to light. Dark adaptation-adjustment of the eye such 68 ã 2002 The College of Optometrists Tinted lenses and low vision: F. Eperjesi et al. 69 that after observation in the dark, sensitivity to light is A prescription can be ground on to the surface and the greatly increased. These meanings will be used in the lens glazed into a spectacle frame. discussion and conclusions sections of this paper, There are currently six CPFÒs, marketed under the however, it is not possible to determine how these terms Glare Control trademark (Corning SA, Division Op- were interpreted by the investigators of the various tique, 77167 Bagneaux-sur-Loing, France) each with a studies described. dierent wavelength cut-o level: CPFÒ450, CPFÒ511, CPFÒ527, CPFÒ550, CPFÒ527X (improved colour rendition and better cosmetic appearance than the Commercially available tinted lenses standard CPFÒ527) and the CPFÒ GlareCutterTM (improved colour rendition compared with the other Corning photochromic ®lters ®lters). The number corresponds to the wavelength in The optical division of Corning Glass developed the nanometers, above which light is transmitted. See Corning photochromic ®lters (CPFÒ) range, which is Table 1 for CPFÒ characteristics. considered by some practitioners to be the gold standard Corning recommend certain ®lters for certain tasks for use in low vision rehabilitation. These tints have and for certain eye conditions. For example, CPFÒ450 been designed, and are marketed speci®cally, to improve is recommended for indoor use, for reading, watching the comfort and visual performance of visually impaired TV, VDU and oce work, for `hobbyists' and as a people who suer from a range of ocular disorders. The shopping aid; CPFÒ511 and CPFÒ527 `have been found tints evolved from research in the late 1970s investi- to be of bene®t by many people who experience visual gating the possible detrimental eects of visible light on problems associated with cataract or macular degener- the ocular system. ation'. The CPFÒs can be glazed into a spectacle frame, According to Corning marketing literature, `short with or without side-shields and in a variety of lens wavelength light has been shown to cause visual forms and materials (see Table 2 for details). Corning discomfort, hazy vision, reduced contrast and prolonged advise that prospective users are given enough time to adaptation times'. It is implied that CPFÒs can alleviate test the ®lters and recommend the use of a plano, ®xed- some or all of these eects by ®ltering out blue light in tint, plastic clip-on to give the user experience with all the visible portion of the spectrum, `at the wavelengths the ®lters, both in and outdoors over a trial period. that create problems for the photophobic or ageing eye'. There are several CPFÒ facsimiles that are claimed to They are designed to ®lter short wavelength light of perform in a similar way to CPFÒs, but none have as yet solar and arti®cial origin. been scienti®cally appraised. A base borosilicate, photochromic glass is used in the manufacturing process. This goes through a ®ring UVShieldÒ and NoIRÒ ®lters treatment that changes the chemical structure of the silver halide crystals at the surface of the lens. The tint NoIR Medical Technologies (South Lyon, MI, USA) produced by this `chemtempering technique' is inde- market two types of ®lter for use in low vision; the pendent of thickness and is even across the lens surface. UVShieldÒ and the NoIRÒ ®lter. According to the Table 1. Transmission details for CPFÒ range (from Corning marketing material) CPFÒ450 CPFÒ511 CPFÒ527 CPFÒ550 CPFÒ527X GlareCutterTM Wavelength cut-off (nm) 450 511 527 550 ± ± % Light transmission (lightened state) 67 44 32 21 33 18 % Light transmission (darkened state) 19 14 11 5 15 6 Absorption % in darkened state Minimum UVB 100 100 100 100 100 100 Minimum UVA 97 98 98 99 98 98 Blue light 95 98 98 98 98 98 Table 2. CPF lens forms, power ranges and materials (from Corning marketing material) Lens form Refractive index Spherical power range (DS) Cylindrical power range (DC) Addition (DS) Single vision 1.50 glass +6.00 to )8.00 Up to 4.00 ± Single vision 1.80 glass +6.00 to )23.00 Up to 4.00 ± C28 bifocal 1.50 glass +6.00 to )8.00 Up to 4.00 0.75±4.00 Progressive 1.50 glass +6.00 to )8.00 Up to 4.00 0.75±3.50 Fixed tint clip-on 1.50 plastic Plano Plano ± ã 2002 The College of Optometrists 70 Ophthal. Physiol. Opt. 2002 22:No1 manufacturer's marketing literature, the UVShieldÒ studies have been divided into those that used mainly provides protection for 100% UV and visible light and objective outcome measures and those that used mainly the NoIRÒ ®lter eliminates near infrared, 100% UV and subjective outcome measures in the determination of `provides visible light protection, for maximum eye eects of tinted lenses on visual performance. Those comfort'. At the time of writing there are 22 UVShieldsÒ studies with an objective outcome measure have been and 12 NoIRÒ ®lters. Constructed from polycarbonate, further divided according to the measure used, for they retain their original shape and will not stretch or example, the eect of tinted lenses and ®lters on VA. deform with use. Supplied in large ®tover moulded form, with wide temples that double as side-shields, and Objective outcome measures made from the same material with the same colour as the front. The design helps to shield the eyes from light Visual acuity incident from above and that re¯ected from below and allows a wide ®eld of view. During the manufacturing The literature search located six papers that reported a process an ultraviolet and infrared absorbing chemical is positive eect of tinted lenses on VA. Lynch and Brilliant blended with polycarbonate before it is moulded into the (1984) compared the eects of CPFÒ550 and a 20% ®nal product. A hard-coated version is available. transmission neutral density (ND) ®lter on the VA of 16 From discussions with several low vision specialists, it RP subjects. CPFÒ550 improved VA in 24 eyes, one seems that the current mode of determining whether decreased, and in seven it remained unchanged. Eight tinted lenses will be of bene®t to a particular person is to eyes that had improved VA with the ND ®lter had even have a brief indoor clinic based trial, with a plano plastic greater improvement with the CPFÒ550.