Putting vital stains in context

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  • SPECIAL ARTICLE

    Putting vital stains in context

    Clin Exp Optom 2013; 96: 400421 DOI:10.1111/j.1444-0938.2012.00802.x

    Nathan Efron BScOptom PhD DScFAAOInstitute of Health and Biomedical Innovation,and School of Optometry and Vision Science,Queensland University of Technology, Kelvin Grove,Queensland, AustraliaE-mail: n.efron@qut.edu.au

    While vital staining remains a cornerstone in the diagnosis of ocular disease and contactlens complications, there are many misconceptions regarding the properties of com-monly used dyes by eye-care practitioners and what is and what is not corneal stainingafter instillation of sodium fluorescein. Similarly, the proper use and diagnostic utility ofrose Bengal and lissamine green B, the other two ophthalmic dyes commonly used forassessing ocular complications, have similarly remained unclear. Due to the limitationsof vital stains for definitive diagnosis, concomitant signs and symptoms in addition to acomplete patient history are required. Over the past decade, there have been manyreports of a type of corneal stainingoften referred to as solution-induced cornealstaining (SICS)that is observed with the use of multipurpose solutions in combinationwith soft lenses, more specifically silicone hydrogel lenses. Some authors believe thatSICS is a sign of lens/solution incompatibility; however, new research shows that SICSmay be neither a measure of lens/solution biocompatibility nor true corneal staining,as that observed in pathological situations. A large component of SICS may be a benignphenomenon, known as preservative-associated transient hyperfluorescence (PATH).There is a lack of correlated signs and/or symptoms with SICS/PATH. Several proper-ties of SICS/PATH, such as appearance and duration, differentiate it from pathologicalcorneal staining. This paper reviews the properties of vital stains, their use and limita-tions in assessment of the ocular surface, the aetiology of corneal staining, characteris-tics of SICS/PATH that differentiate it from pathological corneal staining and what theSICS/PATH phenomenon means for contact lens-wearing patients.

    Submitted: 9 June 2011Revised: 17 June 2012Accepted for publication: 19 June 2012

    Key words: cornea, fluorescein, preservative-associated transient hyperfluorescence, solution-induced corneal staining, vital stains

    The use of vital stains to detect ocularsurface abnormalities has been a mainstayfor eye-care professionals for nearly half acentury.1 Since their first use,24 much hasbeen learned regarding their physicalproperties and what the observed ocularsurface staining means with respect toocular health. With the advent of contact

    lenses, ocular surface defects, disordersand diseases have increased in magni-tude.5,6 Differential diagnosis of ocularsurface disorders in contact lens wearers isoften difficult due to the overlappingsymptomatology and signs among differ-ent contact lens complications, as wellas non-contact lens-related disorders.711

    The use of the three most commonlyused vital dyes, rose Bengal (RB),lissamine green B (LG), and sodiumfluorescein (NaFl),12 which havevarious properties and preferred uses(Table 1),1,3,1335 can impart a wealth ofinformation regarding the health of theocular surface and aid in differential

    C L I N I C A L A N D E X P E R I M E N T A L

    OPTOMETRY

    Clinical and Experimental Optometry 96.4 July 2013 2012 The Author

    400 Clinical and Experimental Optometry 2012 Optometrists Association Australia

  • diagnosis of ocular complications(Table 2).1,36,37 Due to ease of use andfamiliarity of eye-care professionals withvital dyes, there may have been an over-reliance on them for assessment of ocularhealth and a definitive cause of complica-

    tions. Their value as a reliable diagnostictool is hampered due to several factors,especially our incomplete knowledge ofwhat these dyes do at a cellular andmolecular level. This has become appar-ent over the past decade due to the vast

    research in dry eye syndromes (DES)38

    and widespread use of silicone hydrogel(SiHy) lenses.39,40

    The seminal study of Jones, McDougalland Sorbara39 in 2002 showed thathigh levels of asymptomatic corneal

    Fluorescein Rose bengal Lissamine green B

    At ocular pH (predominantly) Dianion (two negative charges);large population of monoanionswill also exist23

    Dianion (two negative charges)24 Anion (single negative charge);large population of dianions willalso exist19

    pKa a1 = 2.50; a2 = 3.81; a3 = 6.1023 a1 < 0; a2 = 1.89; a3 = 3.9324 a1 = 1.31; a2 = 7.66; a3 = 11.7219

    Spectra* Abs (nm): lmax = 474500[blue to cyan]23,28,30,75,80

    Em (nm): lmax = 510550[green]28,29,75

    Reflect/transmit = Orange75

    Abs (nm): lmax = 543567,507522

    [green to yellowish green]24,31,34,75

    Em (nm): lmax = 565570[yellowish green to orange]3133,75

    Reflect/transmit = Magenta75

    Abs (nm): lmax = 624635[red]25,72,73,75

    Reflect/transmit = Bluish green75

    Illumination (Filter) Cobalt blue (Yellow Wratten #12)20 White light (None)1 White light (Red Wratten #24)84,161

    Preferred use Cornea;13,26 conjunctiva (only withboth absorption and emissionfilters)27,144

    Conjunctiva13,26; cornea (HSK, DE,other disorders with mucindeficiency)13,26,27

    Conjunctiva;13,26 may be of valueassessing the cornea with a redfilter161

    Test conductance NaFI-impregnated filter stripmoistened with a drop of sterilesaline (excess shaken off); assess1 to 4 minutes after applicationand several blinks27,84

    RB-impregnated filter stripmoistened with a drop of sterilesaline (excess shaken off) or 25 mlof a 1% solution; assessed after afew minutes; perform towards endof ocular surface exam38,152

    LG-impregnated filter stripmoistened with a drop of sterilesaline (excess shaken off) or 10 mlof 1% solution; assessed 1 to 4minutes after application84,161

    Stains Healthy cells15,17,22,50,83

    Damaged cells14,50

    Dead cells17

    Intracellular spaces14,17,21

    Healthy cells18,21,35

    Dead cells3,17

    Damaged cells3,21

    Mucous strands3

    Damaged cells3,21

    Dead cells3

    Mucous strands3

    Correlation with other stains Little correlation with RB andLG1,13,21

    Little correlation with NaFI1,13,21

    High correlation with LG3,13,16,84,95Little correlation with NaFI13

    High correlation with RB3,13,16,84,95

    pKa: the pH value at which equal concentrations of a molecule that differ by a single charge exist (X X X X- -+ pKa pKa pKa1 2 3 2 )lmax: peak/dominant wavelength(s), Abs: absorption, DE: dry eye, Em: emission, HSK: herpes keratitis, LG: lissamine green, NaFI: sodium fluorescein,RB: rose bengal.* Absorption, emission and reflection are highly sensitive to environment; emission and reflection spectra are also highly dependent upon lightsource/excitation wavelength.79 RB has a second lesser peak at 507522 nm; the two peaks are responsible for the magenta, which falls in the non-spectral purples (a combinationof blue and red).24,31

    Table 1. Characteristics of the most commonly used vital stains for ocular surface visualisation

    Putting vital stains in context Efron

    2012 The Author Clinical and Experimental Optometry 96.4 July 2013

    Clinical and Experimental Optometry 2012 Optometrists Association Australia 401

  • Observation Staining Signs Symptoms

    MechanicalForeign body(RGP>SCL)1,11

    NaFlzig-zag track1 Tearing121 Sudden stinging; pain/discomfort while trappedunder lens/eyelid;121

    asymptomatic to milddiscomfort once foreignbody is removed123

    Abrasion NaFlDeep or coalescedepithelial defect122

    Tearing, blepharospasm, ciliaryinjection (severity of signsbased on extent of cornealinjury)121

    Pain (often after lensremoval), FBS, reducedvisual acuity,photophobia122,123

    Superior epithelialarcuate lesion (SEAL)1

    (SiHy>non-SiHySCL or RGP)11

    NaFlsuperior arcuate;parallel to limbus7

    None; some may experiencehyperaemia7

    Most often asymptomaticduring lens wear/FBS afterlens removal; some mayexperience burning,irritation, lens awareness7

    Lens binding/tight lenssyndrome1,11

    (RGP/EW high waterhydrogel lenses)11

    NaFlArc correspondingto lens edge or diffusestain in excessive bearing;1

    RB/LGpossiblecircumlimbal103,124

    Corneal oedema, conjunctivalhyperaemia, poor lensmovement, limbal indentation7,11

    Irritation, visual defects,constant pain/discomfort,photophobia or may beasymptomatic123

    ExposureKeratoconjunctivitissicca/dry eye syndrome(non-Sjgrens) (causedor exacerbated bycontact lens wear)122

    NaFlpunctate epithelialkeratopathy ininterpalpebral region;7,104

    RB/LGconjunctiva stainsmore intensely than cornea;cornea may also stain inmore severe cases37,127

    Negligible tear meniscus at thelower lid, reduced tear break-uptime (TBUT)104

    Dryness, burning/stinging,sandy or gritty FBS,itchiness, excess tearing(epiphora), contact lensintolerance104106

    3/9 oclock staining(RGP)1,108

    NaFlat the 3 and 9oclock positions;1,108

    conjunctiva adjacent tocornea at 3/9 oclock (mostcommonly with highergrade corneal staining andsymptomatic patients)91

    None to moderate bulbarhyperaemia adjacent to cornealstaining91,109

    Asymptomatic (especiallywith low grade cornealstaining), discomfort, FBS,tearing, burning, reducedwearing times, andphotophobia91,126

    Incomplete blink/lagophthalmos(inferior epithelialarcuate lesion/smilestain)1

    (SCL)11

    NaFlinferior arcuatepunctate band;1

    RBlimited to inferonasalcornea and conjunctiva;37

    LGconjunctiva possiblewhen symptomatic110

    None; though low blink rate,increased contact lensdeposition, inferior limbalhyperaemia, lid wiperepitheliopathy may beobserved110,125

    Asymptomatic or milddiscomfort, irr