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  1. Classification of ocular surface burns.

    Dear Editor,

    Although Dua wishes this debate to close, we feel compelled to respond to his most recent e-letter1.

    Dua seems to misunderstand the meaning of the word 'guarded'. We have been careful to use the word 'guarded' rather than poor or other such adjective in terms of prognosis2. Guarded as is currently used when counselling a patient means 'cautious'3. Thus if two patients are told that their injury carries a guarded prognosis, this simply means that their prognosis is uncertain and in this context may be poor, but not necessarily the same. For example, two eyes that fall into grade III, one with conjunctival involvement and the other with corneal involvement will both have a guarded, that is, an uncertain prognosis. The former however, may have a poorer visual outcome and the latter a more unstable ocular surface. In essence two conditions may both have a guarded prognosis but different outcome depending upon treatment. Thus the examples, which Dua1 uses to discredit our classification are in fact entirely consistent within our classification. This is precisely the reason that we have adapted Roper-Hall's classification, with grade III encompassing those injuries, which carry a guarded prognosis. Nevertheless, Dua seems to want to dismiss the simplicity of our classification.

    It is gratifying however, that having previously ignored the inclusion of tarsal conjunctival involvement in their classification of chemical injuries, Dua now recognises its importance in grading a chemical injury.1

    References

    1. Dua HS. Classification of Ocular surface burns. Br J Ophthalmol e-letter, 8 February 2005.

    2. Harun S, Srinivasan S, Hollingworth K, Batterbury M, Kaye SB. Modification of the classification of ocular chemical injuries. Br J Ophthalmol. 2003;88:1353-1354.

    3. Longman Dictionary of the English Language. Longman Group Limited, Longman House Essex CM20 2JE. Merriam-Webster Inc. 1984.

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  2. Classification of Ocular surface burns

    Dear Editor

    Harun et al in their recent eLetter [1] contend that I have failed to understand their motivation. It is not the motivation that is being questioned but the outcome of that motivation, i.e. the proposed modification of the classification. The fact that they see the need to modify the Roper-Hall classification [2] is in itself evidence that the Roper-Hall classification does not entirely fulfil the purpose for which it was designed in the context of modern day practice and indeed is motivation enough to try and change it. Simplifying a classification is commendable but not if the simplification has not been validated and is unsubstantiated. The issue with the Roper-Hall classification is that it lumps a wide range of injury in its final grade IV giving all a poor prognosis. With modern treatments and approaches to management many chemical injuries within the Roper Hall grade IV will today do well. Grade IV injuries with total limbal involvement and total conjunctival involvement will not, despite the recent advances in management. Hence the clinical need is to expand, not contract grade IV, which is what the Dua, King and Joseph Classification does [3]. To the contrary, the proposed modification by Harun et al [4] further compounds the problem by combining the Roper-Hall grades III and IV. It is essential to understand that the Roper-Hall classification is a prognostic classification and one cannot simply give the same prognosis to an eye with (more than) 6 clock hours of affected limbus as to an eye with 12 clock hours of affected limbus (Roper -Hall classification). It is even less conceivable therefore to give an eye with 4 clock hours of affected limbus or 33% conjunctival involvement the same prognosis as an eye with 12 clock hours of limbus involvement and 100% conjunctival involvement as is proposed by Harun et al [4].

    Anatomically the conjunctiva is divided into tarsal (palpebral), forniceal and bulbar areas. Harun et al [4] have emphasised the importance of the forniceal conjunctiva in their original letter but have failed to account for the forniceal conjunctiva in the calculation of the area of conjunctiva involved. To quote from their original letter [4] “The bulbar and tarsal conjunctiva comprise approximately two thirds and one third of the total conjunctival surface respectively.” This contradiction is now being addressed by implying that tarsal and bulbar conjunctiva together include the forniceal conjunctiva! There are several other discrepancies that were pointed out in my previous eLetter [5] which have not been addressed. Another discrepancy worth mentioning is that according to the Table in the proposed modification [5] involvement of inferior bulbar and tarsal conjunctiva (and forniceal) without any corneal or limbal involvement (OR > 1/3 conjunctival involvement), will carry the same guarded prognosis as involvement of the entire limbus and the entire conjunctiva!! This is simply not the case.

    The authors state that their proposed modification can be easily remembered by all ophthalmologists and not just cornea specialists. I ask, what can be more simple (and accurate) than recording clock hours of limbus involvement and percentage of conjunctival involvement, as indicated in the Dua, King and Joseph classification? Surely “all ophthalmologists” would take exception to the suggestion that they need something simpler than this.

    Harminder S Dua

    PS. This debate has stretched far enough and cannot continue without becoming tediously repetitious. I have stated all that I had to and do not intend responding to any further correspondence on any issue that has already been covered thus far.

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  3. Modification of ocular surface burns

    Dear Editor

    In his second eLetter (1), Dua continues his criticism of our proposed modification of the classification of ocular surface burns(2) but once again fails to understand our motivation, which is to simplify the grading of such injuries in the light of recent advances in the management of ocular surface disease (3-6). The result is a modification of a well established classification, which is easily remembered and can be used by all ophthalmologists and not just by corneal specialists. The Dua, King and Joseph classification (7) allows quantification of the injury, which is useful in a research environment but is trapped in its detail for routine clinical use.

    We would reiterate that our modifications are based on recent advances in the management of ocular surface injuries, which have meant that even severe injuries can have good outcomes (3-6). This is the rationale for having Grade III as the most severe injury grade and for uniformly assigning to it a guarded prognosis. Within that grade, different injury patterns will have different management protocols and different rates of recovery. The work by Roper Hall (8) elegantly showed that a good and doubtful prognosis correlated respectively to less or more than one third of conjunctival ischaemia at the limbus. Hence we retained this element of his classification to separate Grade II and Grade III in our modification. It serves to identify a serious ocular surface injury to the non-corneal specialist who can then arrange an appropriate referral. Dua's confusion about the role of 'OR' in our table in order to define the Grade of injury is actually dealt with in the text of the original article (2): the Grade of the injury is assigned simply on the basis of the most severe sign, rather than on the complex analysis of a combination of signs.

    Dua is supportive of our inclusion of conjunctival injury in our proposed modification (1) but disagrees with the inclusion of tarsal conjunctival assessment, on the basis that it does not influence prognosis. This is clearly wrong. Contiguous tarsal and bulbar injury can lead to symblepharon formation and shortening of the conjunctival fornices, which is detrimental to the ocular surface and therefore deserves inclusion in any assessment of ocular surface injury. The bulbar and tarsal conjunctiva extends into the fornices and forniceal conjunctival involvement is therefore included in the measured area of involvement - important for possible stem cell sites (9).

    We would leave it to readers of the Journal and those involved in this field to judge the value of the different grading systems.

    References

    1. Dua HS. Classification of ocular surface burns. Br J Ophthalmol eLetter ( 11 August 2004)

    2. Harun S, Srinivasan S, Hollingworth K, Batterbury M, Kaye SB. Modification of the classification of ocular chemical injuries. Br J Ophthalmol 2003;88:1353-1354

    3. Kobayashi A, Shirao Y, Yoshita T, et al.Temporory amniotic membrane patching for acute chemical burns. Eye 2003; 17: 149-158

    4. Stoiber J, Muss WH, Pohla-Gubo G, Ruckhofer J, Grabner G. Histopathology of human corneas after amniotic membrane and limbal stem cell transplantation for severe chemical burn. Cornea 2002;21(5):482-489.

    5.Nishiwaki-Dantas MC, Dantas PE, Reggi JR. Ipsilateral limbal translocation for treatment of partial limbal deficiency secondary to ocular alkali burn. Br J Ophthalmol 2001;85(9):1031-1033

    6.Ozdemir O, Tekeli O, Ornek K, Arslanpence A, Yalcindag NF. Limbal autograft and allograft transplantations in patients with corneal burns. Eye 2004;18(3):241-248

    7.Dua HS, King AJ, Joseph A. A new classification of ocular surface burns. Br J Ophthalmol 2001;85:1379-1383

    8.Roper-Hall MJ. Themal and chemical burns.Trans Ophthalmol Soc UK 1965;85:631-53

    9.Wei Z-G, Cotsarelis G, Sun T-T, Lavker RM. Label-retaining cells are preferentially located in the forniceal epithelium:implications on conjunctival epithelial haemostasis. Invest Ophthal Vis Sci 1995;36:236-46

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  4. Classification of Ocular surface burns

    Dear Editor

    It is interesting to read the attempt by Harun et [1] mounting a robust defence of their purely theoretical modification of the Roper Hall classification which has stood us well over the years but now takes its proud place in history. In the penultimate paragraph of the recent eLetter they contend that it is incorrect to state that their proposal is purely theoretical as they "..have based it on a widely accepted classification, which has almost 40 years of clinical use." The point is that the Roper Hall classification is widely accepted, their modification of it is purely theoretical and not clinically tested. I do not see how they can justify their modification by piggy backing on the very classification they are trying to modify?

    In their second eLetter they make the technical point that three clock hours is 1/4 of limbal involvement and not 1/3rd. They miss the real point however that any classification equating more than 1/3rd limbal involvement with total (12 clock hours) limbal involvement and lumping the entire range therein in one grade of III+, is inaccurate as a prognostic indicator. They illustrate this flaw in paragraph four where they claim that injuries involving more than 3 to 6 clock hours of the limbus would be classified as Grade III (as would someone with 12 clock hours of limbal involvement). To give an eye with just over 1/3rd limbal damage and just over 1/3rd conjunctival damage the same "guarded" prognosis (grade III+) as an eye with 12 clock hours of limbal damage and total bulbar and forniceal conjunctival damage (also grade III+ in the proposed modification [2])incorrect and unacceptable. The prognosis for the latter is "very poor" not "guarded".

    It is correct that The Roper Hall classification [3] did not take into account conjunctival involvement in the same sense as is considered in the Dua, King and Joseph classification [4] or indeed in the proposed modification [2]. The Roper Hall classification refers to the limbus and "contiguous conjunctiva" which implies the involvement of conjunctiva adjacent to the limbus only. This is reflected in the table of the Roper Hall classification where the word 'conjunctiva' only appears at the heading of a column with no allowance made for including conjunctiva in the actual grading of the burn. Harun et al, [1,2] make an important point about the tarsal conjunctiva and clearly it is important to examine it in every ocular burns patient. However, for the purpose of the classification it does not make any material difference, as in my experience I have never encountered a case of tarsal burn without associated bulblar and/or foniceal conjunctival involvement. I would be interested to know if the Harun et al have. They imply that the Dua, King and Joseph classification [4] does not take into consideration forniceal involvement. This is not correct. In the original paper [4] a whole paragraph is devoted to his aspect. Harun et al in their original letter [2] distinguish between bulbar forniceal and tarsal conjunctiva and the mucocutaneous junction emphasising the importance of the latter two. Why then in their proposed modification do they not take into account the latter two? In paragraph six of the original letter [2] they account for one hundred percent of the conjunctival surface by divvying up the bulbar and tarsal conjunctiva. What about the forniceal conjunctiva, where the stem cells of the conjunctival epithelium are believed to reside [5,6]. Why is this not accounted for in the modification?

    Harun et al [1] state that "Dua also misinterprets the quantification of corneal damage. He admits that corneal haze is an indicator of severity of injury and of the offending chemical..." They have clearly misquoted me on this. Neither in the original paper nor in my response to their first letter have I stated the above. On the contrary I have stated that "Corneal haze can be an indicator of the offending chemical rather than the severity of the insult." Corneal haze or lack thereof can be very varying and misleading especially soon after a chemical insult.

    In Harun et al's proposed modification [2] the confusion is confounded because the table is not consistent with the text that supports it. In the table grade III+ equates to Hazy cornea OR >1/3 limbal ischaemia OR >1/3 conjunctival involvement. The text states "Grade III includes either a hazy cornea....and/or greater than one third of limbal or conjunctival damage." This begs the questions: What is the difference between III+ and III? Is "or" the same as "and/or"? to most people it isn't. Will greater than 1/3 conjunctival damage without limbal damage carry the same prognosis (as implied in the proposed modification) as greater than 1/3 conjunctival damage with more than 1/3 limbal damage? In their arguments they make a case, for retaining the term "ischaemia" over "involvement" yet use the terms "ischaemia", "involvement" and "damage" interchangeably through the text for both limbus and conjunctiva. For example "Grade II includes limbal or conjunctival involvement, but involving less than one third of the area involved" [2]. Furthermore, what is "... Involving less than one third of the area involved" supposed to mean?

    The authors allege that the Dua, King and Joseph classification [4] is "..a complicated semi-analogue sub-classification." Here again it is likely that they have misunderstood the classification. The table in the paper [4], as has been adequately explained by the supporting text, refers to a stepped graded classification, consistent with past and current systems, in the left hand columns and to an analogue scale (which one may prefer to call semi-analogue) in the right hand columns. On balance, in the paper, the analogue scale is recommended.

    What can be more simple than documenting the clock hours of limbus involvement and percentage of conjunctival involvement (tarsal conjunctiva included or not) as a true representation of the extent of damage following a chemical burn? These two are the key indicators of the eventual prognosis in terms of ocular surface reconstruction and visual improvement thereof. Even an attempt to put these into grades I to III or IV or VI would be superfluous as that is merely a 'lumping' exercise. For the purpose of any study or comparison, the documentation of clock hours of limbal involvement and extent of conjunctival involvement, whether in proportions or percentages, as accurately as possible will allow subsequent groupings tailored to address the question posed.

    The authors end with a profound statement "Without good evidence to the contrary, it would be irresponsible to disregard a widely accepted grading system." Unfortunately it applies aptly to their proposed modification.

    References

    (1) Harun S, Srinivasan S, Hollingworth K, Batterbury M, Kaye SB. Classification of ocular chemical injuries, continued BJO second eLetter (13 July 2004)

    (2) Harun S et al. Modification of classifiaction of ocular chemical injuries [electronic response to Dua et al. A new classification of ocular surface burns] bjophthalmol.com 2004 http://bjo.bmjjournals.com/cgi/eletters/85/11/1379#219

    (3) Roper-Hall MJ. Thermal and chemical burns. Trans Ophthalmol Soc UK 1965;85:631-53

    (4) Dua HS, King AJ, Joseph A. New Classification of Ocular surface burns. Br J Ophthalmol 2001; 85:1379-83

    (5) Wei Z-G, Cotsarelis G, Sun T-T, Lavker RM. Label-retaining cells are preferentially located in the forniceal epithelium: implications on conjunctival epithelial homeostasis. Invest Ophthalmol Vis Sci 1995;36: 236-46.

    (6) Pellegrini G, Golisano O, Paterna P et al. Location and clonal analysis of stem cells and their differentiated progeny in the human ocular surface. J Cell Biol 1999;145:769-82.

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  5. Classification of ocular chemical injuries, continued

    Dear Editor

    We welcome Dua's comments [1] regarding our proposed modification of the classification of ocular chemical injuries [2], as they help to highlight the reason why we have sought to modify a classification which has been used by ophthalmologists for many years, updating it based upon advances in our understanding of the healing of the ocular surface and have not attempted to design an entirely new system.

    His interpretation of our classification is misleading to the casual reader. It is incorrect that 12 clock hours of limbal involvement would be graded the same as 3 clock hours. Three clock hours represents ¼ of limbal involvement and therefore, would be classified on the basis of the most severe sign as grade II, whereas 12 clock hours (greater than 1/3) would be grade III. In the absence of good evidence that a difference of 1-3 clocks hours of limbal ischaemia or staining carries a significantly worse prognosis, there seems to be little point in promoting a complicated semi-analogue sub-classification.

    His assertion that the Roper-Hall classification [3] did not take into account conjunctival involvement is inaccurate. Both Ballen and Roper-Hall stressed the importance of conjunctival involvement [4,3]. Dr Dua further states that assessment of the tarsal conjunctiva is impractical. This is an integral part of the assessment, both to locate noxious foreign bodies and to identify the possibility of future symblepharon formation, particularly if contiguous bulbar and tarsal conjunctiva are affected. As has recently become apparent, the tarsal conjunctiva plays a pivotal role in maintaining the health of the ocular surface [5,6]- hence the inclusion of the tarsal conjunctival area in our classification.

    Dua also misinterprets the quantification of corneal damage. He admits that corneal haze is an indicator of severity of injury and of the offending chemical but has not included it in his classification [7]. To reduce or disregard the importance of corneal involvement, without good evidence to the contrary, is unsupported. Both Roper-Hall and Ballen recognized the importance of corneal damage [3,4] , hence its retention in our modified classification. Furthermore, the assertion that many chemical injuries involving more than 3 to 6 clock hours of the limbus with a clear cornea would not be catered for in our classification is inaccurate: they would comprise greater than 1/3 limbal injury and be classified on the basis of the most severe sign as Grade III.

    We retained limbal ischaemia in our classification as it has been validated as a prognostic indicator in the original Roper-Hall classification and provides continuity with it. We do not promote limbal staining as evidence of ischaemia, because there is no evidence that it is a better indicator of limbal stem cell damage. Indeed the evidence would favour limbal ischaemia [3,4]. Therefore, there is no issue in using both corneal and conjunctival staining to grade the extent of the injury, precisely because we do not presume that staining represents ischemia or stem cell failure.

    Whilst the effect of a chemical injury may not be fully apparent at presentation, this in no way invalidates grading or classifying the injury at presentation. There is no constraint to a chemical injury being graded as II at presentation and grade III when evaluated at a later date. The assertion that the modified classification does not allow for variation in the extent of the conjunctival and limbal injury is flawed. As stated, the most severe sign dictates the grade.

    Dr Dua is incorrect in saying that our proposals are purely theoretical and not based on clinical experience. We have based them on a widely accepted classification, which has almost 40 years of clinical use and have essentially made a few adjustments, while retaining the core principles.

    Without good evidence to the contrary, it would be irresponsible to disregard a widely accepted grading system. However, the success of such a classification does not depend on how good the authors perceive it to be but on how user friendly and reliable it is to the clinicians who deal first hand with such injuries. We would leave it to the reader to decide if this has been achieved.

    References:

    (1) Dua HS. Classification of ocular surface burns :Authors response.bjophthalmol.com 2004. http:/bjo.bmjjournals.com/cgi/eletters/85/11/1379#219

    (2) Harun S et al. Classification of ocular surface burns electronic response to Dua et al. (A new classification of ocular surface burns).bjophthalmol.com 2004. http:/bjo.bmjjournals.com/cgi/eletters/85/11/1379#219

    (3) Roper-Hall MJ. Thermal and chemical burns. Trans Ophthalmol Soc UK 1965;85:631-53

    (4) Ballen PH, Hemstead NY.Treatment of chemical burns of the eye.Eye,Ear, Nose and Throat Monthly 1964;43:57-61

    (5) Wirtschafter JD., Ketcham JM, Weinstock RJ, et al. Mucocutaneous junction as the major source of replacement palpebral conjunctival epithelial cells. Inv Ophth Visual Science. 40(13):3138-46, 1999 Dec.

    (6) Wei ZG, Wu RL, Lavkar RM, et al. In vitro growth and differentiation of rabbit bulbar, fornix and palpebral conjunctival epithelia. Implications on conjunctival epithelial transdifferentiation and stem cells. Inv Ophth Visual Science 1993 Apr;34(5):1814-1828

    (7) Dua HS, King AJ, Joseph A. A new classification of ocular surface burns. BJO 2001;85:1379-1383

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  6. Classification of ocular surface burns: Author's response

    Dear Editor

    The eLetter by Harun et al. on "Modification of classification of ocular chemical injuries"[1] is to be commended in so far as it highlights the problems with the current Roper-Hall classification system and the difficulties it poses in evaluating outcome and efficacy of treatment modalities in ocular surface burns. As a proposed modification however, it is a retrograde step.

    The three major issues with the Roper-Hall [2] classification were that it lumped all injuries with 50% or more of limbal involvement into one category, did not take into account conjunctival involvement in the actual classification and placed undue emphasis on the degree of corneal haze.

    The proposed modification by Harun S et al. goes a step backwards by grouping all injuries with more than 33% limbal involvement (1/3) into one category. The grading of a patient with all 12-clock hours of limbus involvement would then be the same as one with just over 3 clock hours of limbus involvement! The prognosis given to these two patients cannot be the same, given that the Roper-Hall and the Dua, King and Joseph [3] classifications are prognostic classifications. Furthermore, a patient presenting with less than one third limbus involvement does not necessarily come with less than one third conjunctival involvement, which could be much more. The proposed modification does not allow for such variances, which are frequent. The Dua, King and Joseph classification has the flexibility to allow for such variables and also to progressively document change both improvement and deterioration, over the acute phase of the injury. The authors rightly point out that the degree of ischaemia does not always correspond to degree of limbal involvement. Yet limbal involvement without ischaemia, in the form of loss of stem cells, can have an equally important impact on prognosis. That is precisely why the Dua, King and Joseph classification considers limbal involvement (to encompass ischaemia as well) rather than limbal ischaemia alone.

    The point about conjunctival involvement is well made in the proposed modification. This does not differ significantly from the Dua, King and Joseph classification. The latter was the first to take this aspect of burns into account in determining severity and prognosis. The authors mention the importance of tarsal conjunctival involvement. This is a valid though often an impractical consideration. Associated swelling, induration, thickening, shrinkage and the like, of the lids make tarsal conjunctival evaluation impractical if not impossible in some cases, in the immediate post injury period. It was for this practical consideration that the Dua, King and Joseph classification included only the extent of bulbar conjunctival involvement in determining the grade. It is interesting to note that the authors disregard limbal fluorescein staining as an indicator of limbal damage (as proposed in the Dua, King and Joseph classification) but propose fluorescein staining as an indicator of conjunctival damage in evaluating extent of conjunctival damage. This implies that fluorescein staining is appropriate to evaluate both conjunctival epithelial damage and conjunctival ischaemia but not limbal epithelial damage and limbal ischaemia. There is no rationale for this.

    Corneal haze can be an indicator of the offending chemical rather than the severity of the insult. It is not uncommon to find a clear and transparent cornea, which is totally denuded of its epithelium, immediately after a chemical injury. This can stay so for a few days before becoming rapidly hazy or opaque, or remain clear and become re- epithelised. Corneal endothelial damage leading to stromal edema and haze can occur later in the course of an acute chemical injury. Conversely, a hazy cornea with a resultant scar could do well following a corneal graft procedure if the limbal involvement is minimal. The proposed modification retains corneal haze as a grading parameter and includes a hazy cornea in grade 3 only. There are many chemical injuries, which involve 3 to 6 clock hours of the limbus (30 to 50%) with a clear cornea. These do not fall well in any grade in the proposed new classification and highlight the inherent problem in the Roper-Hall classification and its proposed modification.

    Most important of all, the proposed classification is purely theoretical and has not been validated. The Dua, King and Joseph classification is based on several years of clinical experience of managing burns including over 67 patients. It is simple and easy to use (clock hours of limbus involvement and percentage of conjunctival involvement), flexible and allows for all combinations of different extents of involvement of the two structures. It is validated as a prognostic indicator and allows for accurate comparison of cases. The proposed new classification/modification fails on all these counts.

    References

    (1) Harun S et al. Modification of classifiaction of ocular chemical injuries [electronic response to Dua et al. A new classification of ocular surface burns] bjophthalmol.com 2004http://bjo.bmjjournals.com/cgi/eletters/85/11/1379#219

    (2) Roper-Hall MJ. Thermal and chemical burns. Trans Ophthalmol Soc UK 1965;85:631-53

    (3) Dua HS, King AJ, Joseph A. New Classification of Ocular surface burns. Br J Ophthalmol 2001; 85:1379-83

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  7. Modification of classifiaction of ocular chemical injuries

    Dear Editor

    A recent paper by Kobayashi and co-workers[1] on temporary amniotic membrane patching for acute chemical burns highlights the difficulty in the consistent classification of this type of injury.

    Roper-Hall’s classification of acute chemical injuries to the eye is based on the original classification of Ballen[4] and there is little difference between them. However, in neither classification is the grade based on the most severe sign. This immediately leads to the problem of trying to classify an eye having, for example, corneal signs of one grade and conjunctival signs of another. There is also difficulty in grading the conjunctival and limbal injuries.

    Dua et al.[2] recognized the problem of assessing limbal stem cell damage and proposed a quasi-analogue scale in order to incorporate inter-grade variations. They suggested using limbal fluorescein staining as a marker of limbal stem cell damage. However, their grading scheme is complex and departs significantly from that of Roper-Hall. Although fluorescein staining is a useful sign, it does not necessarily imply limbal stem cell damage or failure and has not been shown to be a better index of limbal damage than perilimbal ischaemia. Importantly, it is also becoming apparent, that both the fornices and mucocutaneous junction of the conjunctiva are important for conjunctival regeneration.[5,6] In fact, Roper Hall stressed the importance of involvement of contiguous area of the conjunctiva, which may lead to symblepharon formation.[2]

    Although there are limitations with Roper-Hall’s classification, it is simple and remains popular. Rather than replace Roper-Hall and Ballen’s classification,[3] we suggest a modification, which addresses some of the issues raised and makes the classification more robust.

    One of the questions that needs to be answered is whether to base the grade of injury upon the most severe sign or on a combination of ocular surface signs. A combination of signs using 3 parameters (cornea, limbus and conjunctiva) each with 3 levels requires 27 possible combinations to avoid cross-over. To avoid this complexity and without evidence to indicate a difference in prognosis, it would seem reasonable therefore to base the grade of injury on the most severe sign.

    Although limbal ischaemia does not necessarily imply limbal stem cell failure, it remains to be shown that it is less indicative than fluorescein limbal staining of limbal damage. We propose therefore to continue to use limbal ischaemia in the grading of injury. With regard to conjunctival involvement, in order to be able to include the total area of involvement, we suggest dividing the conjunctival surface into bulbar and tarsal areas, as is natural. The bulbar and tarsal conjunctiva comprise approximately two thirds and one third of the total conjunctival surface respectively. Using conjunctival fluorescein staining as an indicator of the extent of conjunctival damage, the area of involvement can be based on the fraction of the third involved, limiting any division into not less than sixths. That is, the tarsal surfaces together comprise a third of conjunctiva (see Figure 1). This includes the issue that a vertical distribution of conjunctival injury is as important as a horizontal distribution.

    Figure1 Estimation of Conjunctival injury

    E.g, 1/6th +1/6th = 1/3rd

    Corneal involvement in terms of prognosis remains an area of difficulty. Although it may be assumed that limbal and conjunctival damage implies a worse prognosis than isolated corneal damage, this has yet to be shown. In addition, a severe chemical injury involving the cornea but not the limbus, or vice versa, would be expected to be an uncommon event. We therefore propose to retain the degree of corneal damage (as proposed by Roper-Hall [3] and Ballen [4]) in grading of the injury (see Table 1).

     

    Table 1 Modified Classification of Ocullar Chemical Injuries

    Grade Cornea Limbal
    Ischaemia
    Conjunctival involvement Prognosis
    I Clear: epithelial damage only None None Good
    II Clear: epithelial damage only <1/3 <1/3 Good
    III+ Hazy cornea OR >1/3 OR >1/3 Guarded

    Thus grade I is identified by any isolated corneal epithelial injury. Grade II includes limbal or conjunctival involvement, but involving less than one third of the area involved. Grade III includes either a hazy cornea, defined as obscurity of the iris or pupil details (as per Roper-Hall’s and Ballen’s original descriptions), and/or greater than one third of limbal or conjunctival damage. With the advent of recent surgical techniques such as amniotic membrane transplants and limbal allografts, the prognosis of more severe ocular chemical injuries previously classified as Roper-Hall grade IV have improved and no longer carry a uniformly poor prognosis.[2] Therefore we reason that these cases can be included in Grade III of our proposed classification.

    In conclusion, in the absence of good evidence for re-classifying ocular surface injuries, it would seem reasonable to keep to Roper-Hall / Ballen’s classification and to move it forwards by addressing the weaknesses of that system. We hope that the proposed grading system improves the consistency with which chemical injuries are reported in the literature, serves as a basis for controlled comparative evaluation of modern treatment options and stimulates further work in this area.

    References

    1. Kobayashi A, Shirao Y, Yoshita T, et al.Temporory amniotic membrane patching for acute chemical burns. Eye 2003; 17: 149-158

    2. Dua HS, King AJ, Joseph A. A new classification of ocular surface burns. BJO 2001;85:1379-1383

    3. Roper-Hall MJ. Themal and chemical burns. Trans Ophthalmol Soc UK 1965;85:631-53

    4. Ballen PH, Hemstead NY.Treatment of chemical burns of the eye.Eye,Ear, Nose and Throat Monthly 1964;43:57-61

    5. Wirtschafter JD., Ketcham JM, Weinstock RJ, et al. Mucocutaneous junction as the major source of replacement palpebral conjunctival epithelial cells. Inv Ophth Visual Science. 40(13):3138-46, 1999 Dec.

    6. Wei ZG, Wu RL, Lavkar RM, et al. In vitro growth and differentiation of rabbit bulbar, fornix and palpebral conjunctival epithelia. Implications on conjunctival epithelial transdifferentiation and stem cells. Inv Ophth Visual Science 1993 Apr;34(5):1814-1828

    7. Brodovsky SC, McCarty CA, Snibson G, et al. Management of alkali burns: an 11 year retrospective review. Ophthalmology. 2000;107(10):1829-1835

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