We have read with avid interest the article by Gupta et al. on the use of bovine pericardium as a wrapping material for hydroxyapatite orbital implants.[1] We are highly impressed by their results as none of the patients had implant extrusion. This is really commendable since implant extrusion rate has ranged from 9 % to 21 % in previous studies,[2] and it indicates meticulous technique and follow up....
We have read with avid interest the article by Gupta et al. on the use of bovine pericardium as a wrapping material for hydroxyapatite orbital implants.[1] We are highly impressed by their results as none of the patients had implant extrusion. This is really commendable since implant extrusion rate has ranged from 9 % to 21 % in previous studies,[2] and it indicates meticulous technique and follow up. We would like to clarify a few pertinent issues.
Although bovine pericardium is generally considered non-reactive, it has been reported to produce severe inflammatory reaction in cardiac use.[3] Another area of major concern with cardiovascular use of bovine pericardium has been development of calcification seen in both laboratory studies and cardiac patients.[4] It is still uncertain what impact such a calcification would have on an orbital implant and assessment of its effect would certainly require studies with a larger number of patients and longer follow up. However, it has been suggested that it may hamper its motility.[2] We suggest that the possibility of misinterpretation of imaging findings in cases of orbital recurrence of tumours should not be overlooked.
Another crucial area of concern is the risk of infection with xenografts, which cannot be totally eliminated even by highly stringent screening and processing procedures. We are referring to the group of bovine spongiform encephalopathies including Creutzfeld-Jakob disease (CJD) and its variant found in the United Kingdom (CJDv).
Therefore, the quest for a comparable synthetic wrapping material and better implants which do not require wrapping continues, and bovine pericardium should be considered, keeping in view its above mentioned shortcomings.
Mandeep S. Bajaj, MD
Neelam Pushker, MD
Dr Rajendra Prasad Centre for Ophthalmic Sciences
All India Institute of Medical Sciences
Ansari Nagar, New Delhi - 110 029
India
References
(1) Gupta M, Puri P, Rennie IG. Use of bovine pericardium as a wrapping material for hydroxyapatite orbital implants. Br J Ophthalmol 2002;86:288-9.
(2) Gayre GS, Debacker C, Lipham W, et al. Bovine pericardium as a wrapping for orbital implants. Ophthal Plast Reconstr Surg 2001;17:381-7.
(3) Skinner JR, Kim H, Toon RS, et al. Inflammatory epicardial reaction to processed bovine pericardium: case report. J Thorac Cardiovas Surg 1984;88: 789-91.
(4) Braile DM, Ardito RV, Greco OT, et al. IMC bovine pericardial valve: 11 years. J Card Surg 1991;6:580-8.
We read with great interest the article by Takei et al..[1] We
agree with the authors that axial length (AL) measurement in silicone
oil-filled eyes is a difficult situation. The need for accurate estimation
of AL has increased following advances in vitreoretinal surgical techniques
and improved visual results. We complement Takei and colleagues for an
excellent report on the matter. CT scanning for...
We read with great interest the article by Takei et al..[1] We
agree with the authors that axial length (AL) measurement in silicone
oil-filled eyes is a difficult situation. The need for accurate estimation
of AL has increased following advances in vitreoretinal surgical techniques
and improved visual results. We complement Takei and colleagues for an
excellent report on the matter. CT scanning for AL measurement is a novel
technique, but not without pitfalls.
We had studied AL in 28 eyes pre and post-silicon oil removal (viscosity
1000 centistoke) using A-scan ultrasonography in the sitting position and
found that the ratio between actual AL and AL measured in silicon oil-filled
eyes varied widely, from 0.64 to 0.92. This is in contrast to the study by
Murray et al.[2] who showed minimal variability and could derive a
mathematical constant of 0.71 to calculate AL in silicon oil-filled eyes to
get the actual AL.
We did find that the AL in the fellow eye compared well with the post SO
removal AL. Although the best method of biometry in silicon oil-filled eyes
still eludes us, we feel that AL measurement prior to the vitreo-retinal
procedure may be the best option (using combined A and B scan
ultrasonography). Failing that, AL in the fellow eye may give a fair
estimate. However the claims of CT scan for accurate determination of AL
needs further evaluation and refining considering its lack of easy
availability, high cost and irradiation exposure.
References
(1) Takei K, Sekine Y, Okamoto F and Hommura S. Measurement of axial
length of eyes with incomplete filling of silicone oil in the vitreous
cavity using X-ray computed tomography. Br J Ophthalmol 2002;86:47-50.
(2) Murray DC, Potamitis T, Good P, Kirkby GR, Benson MT. Biometry of
the silicone oil-filled eye. Eye 1999 Jun;13; 319-24.
I read with great interest the excellent perspective by Plsková et al1 in which they raise the issue of transient corneal opacification following corneal transplantation in the mouse model and argue that it might be due to a sufficient number of endothelia[l] cells regaining function.
What the authors describe for the mouse model, also occurs in the rat model. In fact most researchers in the rat model pr...
I read with great interest the excellent perspective by Plsková et al1 in which they raise the issue of transient corneal opacification following corneal transplantation in the mouse model and argue that it might be due to a sufficient number of endothelia[l] cells regaining function.
What the authors describe for the mouse model, also occurs in the rat model. In fact most researchers in the rat model probably have this experience, but for some reason do not think it is very important and/or choose to ignore it. Apart from the article by Williams et al[2], there is - as far as I know - only one other author who has explicitly mentioned this transient opacification. In his paper, Herbort[3] wrote "The grafts began clearing 4 weeks after surgery … and vessels in the graft diminished from 6 weeks post-surgery." and "It has to be noted that after acute rejection most corneas regain some clarity by 7-8 weeks." Transient corneal opacification also occurs in the rat model I used[4] (AO rats (strain RT1u) served as recipients of corneas from PVG rats (strain RT1c) and corneas were sutured with a single running suture). Allogeneic transplanted corneas showed no initial opacification immediately postoperative; neither did the syngeneic controls. All allogeneic corneas "rejected" (or more precisely showed total
opacification) around day 11-13 and those corneas, when followed long enough, all cleared. Opacification remained higher than 2 (meaning an increased corneal haze, but some anterior chamber structures still visible) at days 17-21 and became lower than 2 (slight haze) around days 21-32.
It would be exciting to know if the hypothesis put forward by Plsková et al1 would also apply to the rat model and to find out if this 'clearing' of the opacification also occurs in other rat strains than the ones mentioned.
Plsková et al have brought up a very important topic where a lot of uncertainty still exists, which warrants further research.
REFERENCES
(1) Plsková J, Kuffová L, Holán V, Filipec M, Forrester JV. Evaluation of corneal graft rejection in a mouse model. Br J Ophthalmol 2002;86:108-113.
(2) Williams KA, Coster DJ. Penetrating corneal transplantation in the inbred rat; a new model. Invest Ophthalmol Vis Sci 1985;26:23-30.
(3) Herbort CP, Matsubara M, Nishi M, Mochizuki M. Penetrating keratoplasty in the rat: a model for the study of immunosuppressive treatment of graft rejection. Jpn J Ophthalmol 1989;33:212-220.
(4) Claerhout I, Beele H, Verstraete A, Van den Broecke C, Kestelyn P. The effect of duration and timing of systemic cyclosporine therapy on corneal allograft survival in the rat model. Graefe's Arch Clin Exp Ophthalmol 2001;239:152-157.
Dr Ilse Claerhout
Department of Ophthalmology
Ghent University Hospital
De Pintelaan 185
9000 Gent
Belgium
Ilse.claerhout@rug.ac.be
We thank Dr. Panda for her comments on our recent paper entitled
"Treatment of fungal keratitis by penetrating keratoplasty". Dr. Panda
noted correctly that treatment modalities differ on different types of
keratitis. About 20% of the cases in our study were mixed infections, that
is, fungal infection combined with bacterial or herpes simplex virus
infection. However, the focus of our study was to s...
We thank Dr. Panda for her comments on our recent paper entitled
"Treatment of fungal keratitis by penetrating keratoplasty". Dr. Panda
noted correctly that treatment modalities differ on different types of
keratitis. About 20% of the cases in our study were mixed infections, that
is, fungal infection combined with bacterial or herpes simplex virus
infection. However, the focus of our study was to study the treatment of
severe fungal keratitis cases that could not be controlled by antifungal
medication. KOH wet mount was prepared for all the infected eyes. Though
calcoflour white and acridine orange stain have become popular in the
world, it is difficult to get them in China now. In addition, we do not
feel that KOH wet mount preparation can be substituted by normal saline
smear method, because KOH can dissolve the impurities in the smear so that
the fungal filaments could be seen more clearly through the microscope.
We gave systemic antifungal medication to all the patients, but just
orally for 2 to 3 weeks for the purpose of preventing recurrent fungal
infection after PKP. We agree that fluconazole is only effective on a few
genera of fungi. However, usually it takes at least 3 days to identify the
infected fungi through fungal culture, so we used fluconazole combined
with natamycin or amphotericin B before the fungi were identified.
Furthermore, it is quite necessary to go on using antifungal medication
topically during and after surgery in case the infected tissue has not
been removed in its entirety. Topical antifungal medication is inevitably
epitheliotoxic, which may be endurable comparing with the recurrence of
fungal infection.
Dr. Panda is interested in the characteristic feature of fungi. We
reported it in another recent publication regarding fungal keratitis. [1]
In our study, the patients we performed PKP on were those with fungal
infection that could not be controlled by antifungal medication. We had
observed that more complications would occur after PKP in patients with
fungal keratitis than those with keratococus. However, the result of this
study was exciting, because we attached great importance to the prevention
of complications after surgery. A series of scientific articles written in
Chinese by us regarding this point has been published in the medical
journals in China, and we are preparing manuscripts submitted to journals
published in English in order to introduce them to international
colleagues.
A point of concern was raised about large graft. The optical result
is related to the size of graft, that is, patients with large grafts can
obtain better visual acuity than those with small ones. As long as the
infected tissue has been thoroughly removed, the only thing we need to do
after surgery is to prevent immunorejection.
Amniotic membrane transplantation has been performed at our hospital
for some recalcitrant corneal ulcers, and satisfactory effects were
achieved. Also, we have tried this therapy in a few cases of fungal
keratitis in which the infection just reached the superficial corneal
stroma and was completely removed, but did not get good postoperative
visual acuity. Therefore, at present, only LKP was chosen for the
treatment of fungal infection at the superficial or middle stroma at our
hospital.
Lixin Xie, MD
Shandong Eye Institute & Hospital
Qingdao 266071, P. R. China
References
(1) Xie L, Shi W, Liu Z, Li S. Lamellar keratoplasty for the treatment of
fungal keratitis. Cornea 2002;21:33-7
We have read with keen interest the article on trachomatous
trichiasis by Bowman et al. We fully endorse the authors' observations that
Trachoma and its sequelae are on the decline even in developing countries
as we are witnessing similar trends in south-east Asia,particlarly India.
However,we would like to raise a few pertinent issues.
It is our considered opinion that self-epilation of tri...
We have read with keen interest the article on trachomatous
trichiasis by Bowman et al. We fully endorse the authors' observations that
Trachoma and its sequelae are on the decline even in developing countries
as we are witnessing similar trends in south-east Asia,particlarly India.
However,we would like to raise a few pertinent issues.
It is our considered opinion that self-epilation of trichiatic
eyelashes should not be encouraged as it requires a considerable degree of
patient education and training.In patients with compromised vision due to
corneal opacities,prebyopes and those with poor training skills,it can
prove to be a fairly risky proposition as the patient may inadvertantly
damage vital stuctures such as the cornea and eyelid margin.
Secondly, even in cases which the authors have classified as minor
forms of trichiasis,repeated epilation may not be a preferable option as
the eyelashes which regrow after epilation are usually short with
extremely sharp tips and carry a greater potential for corneal damage than
the longer,unepilated eyelashes.Repeated epilation could lead to
alteration in morphology of the sharp posterior lid margin,which is so
crucial for tear film dynamics and lacrimal pump function.
Therefore,in our experience,we feel that patients with
trichiasis,whether major or minor,should be subjected to a definitive
procedure after the active trachomatous process has been controlled.This
would entail surgical intervention if associated with a marked degree of
entopion,or electrolysis if the trichiatic component alone is predominant.
We read with interest the letter from Amin et al [1], suggesting a modification of the sub-tenon local anaesthetic injection procedure. They advocate the use of a venflon needle to penetrate the conjunctiva, with subsequent advancement of the cannula prior to anaesthetic injection. We are concerned that the use of a sharp needle should be recommended so close to the eye. Amin et al point out that the needle ti...
We read with interest the letter from Amin et al [1], suggesting a modification of the sub-tenon local anaesthetic injection procedure. They advocate the use of a venflon needle to penetrate the conjunctiva, with subsequent advancement of the cannula prior to anaesthetic injection. We are concerned that the use of a sharp needle should be recommended so close to the eye. Amin et al point out that the needle tip is clearly visible at all times and therefore at "minimal risk" of puncturing the eye. However, once under the conjunctiva, the needle is not necessarily "clearly" visible, and if subconjunctival haemorrhage should occur then it will quickly become obscured. We do not think it sensible to place a sharp needle this close to the eye when an effective and well proven alternative delivery system has already stood the test of time [2].
In his editorial on local anaesthetic injection techniques for cataract surgery, Smerdon [3] rightly emphasizes the risk of ocular penetration for all techniques involving needles, and highlights the Royal College of Ophthalmologists local anaesthesia survey[4] which demonstrated the relative safety of sub-tenon's and topical anaesthesia. We agree with him that when discussing an anaesthetic technique with a potential for high volume, it is not the expert anaesthetist/ophthalmologist who should be borne in mind, but rather the less skilled person, possibly less familiar with ophthalmic anaesthetic techniques, or in training, who may be required to administer a block. It is in this setting that the use of a needle very close to the eye is, in our opinion, an unwarranted risk. Surely the "no needle" sub-tenon's technique is just as effective, and safer.
References:
(1) Amin S, Minihan M, Lesnik-Oberstein S, Carr C. A new technique for delivering sub-Tenon's anaesthesia in ophthalmic surgery. Br J Ophthalmol 2002; 86; 119.
(2) Stevens JD. A new local anaesthesia technique for cataract extraction by one quadrant sub-tenon's infiltration. Br J Ophthalmol 1992; 76: 670-4.
(3) Smerdon D. Needle local anaesthesia for cataract surgery: a chip off the old block? Eye (2001) 15, 439-440.
(4) Eke T, Thompson JR. The national survey of local anaesthesia for ocular surgery. II. Safety profiles of local anaesthesia techniques. Eye 1999; 13: 196-204.
I congratulate Riordan-Eva et al for the article on temporal artery biopsy in the management of giant cell arteritis with neuro-ophthalmic complications.[1] This is an excellent article for residents, ER physicians, Family Practice physicians and Ophthalmologists.
The 3 cases discussed clearly show that patients over the age of 50 presenting with temporary or permanent visual loss or binocular dipl...
I congratulate Riordan-Eva et al for the article on temporal artery biopsy in the management of giant cell arteritis with neuro-ophthalmic complications.[1] This is an excellent article for residents, ER physicians, Family Practice physicians and Ophthalmologists.
The 3 cases discussed clearly show that patients over the age of 50 presenting with temporary or permanent visual loss or binocular diplopia and with or without systemic signs of temporal arteritis must have at least SED rate checked. If the suspicion is high the patient must be started on high dose steroids. We prefer IV solumedrol for the first 3-4 days followed by prednisone by mouth. A Medrol dose pack that is given for 5 days in tapering doses is not adequate.
We perform temporal artery at convenience within 2 weeks. When available we prefer to do frozen section on the affected side. If negative we do the other side. When frozen section is not available we do routine biopsy on the affected side and prefer to wait for the results. We do not do bilateral temporal artery biopsy at the same time.
As mentioned in the article the biopsy should be at least 2-2.5 mm and the pathologist must be adequately trained to interpret temporal artery biopsies. With negative biopsies on both sides provided the above criteria are met we conclude that the patient has no GCA.
References
(1) Riordan-Eva, P, Landau, K, and O'Day, J. Temporal artery biopsy in the management of giant cell arteritis with neuro-ophthalmic complications. Brit J Ophthalmol 2001 85: 1248-1251.
It was with great interest that I read the recent article by Dr. al Arab and co-workers entitled "The Burden of Trachoma and the Royal Nile Delta of Egypt; the Survey of Menofiya Governerate".[1] This work clearly shows that endemic blinding trachoma continues to be a major health problem in this area of the Nile Delta, quite close to Cairo.
My attention was particularly drawn to the high rate of recurren...
It was with great interest that I read the recent article by Dr. al Arab and co-workers entitled "The Burden of Trachoma and the Royal Nile Delta of Egypt; the Survey of Menofiya Governerate".[1] This work clearly shows that endemic blinding trachoma continues to be a major health problem in this area of the Nile Delta, quite close to Cairo.
My attention was particularly drawn to the high rate of recurrence amongst those who had had trichiasis surgery. Overall, 44% of cases who had had surgery had recurrent trichiasis. It would be most interesting to look at the time that had elapsed between surgery, and the time of examination. Some have argued that the recurrence rate from trichiasis reflects poor or inadequate surgery. Others have alluded to the fact that the tarsal scarring trachoma is of a progressive nature and that trichiasis is likely to recur because of ongoing scarring, even after otherwise successful surgery. Information of the elapsed time would help explore the scenario.
References
(1) al Arab, GE, Tawfik, N, El Gendy, R, et al. The Burden of Trachoma and the Royal Nile Delta of Egypt; the Survey of Menofiya governerate, Brit J Ophthalmol 2002;85;1406-1410).
I commend Xie et al for their paper on the treatment of fungal keratitis by penetrating keratoplasty [1]. Though the subject is increasingly brought to the notice of the ophthalmic community, it requires more emphasis. This is not a unique problem for China but a major problem for many developing and underdeveloped countries.
In response to this article, a number of questions are raised. Wheth...
I commend Xie et al for their paper on the treatment of fungal keratitis by penetrating keratoplasty [1]. Though the subject is increasingly brought to the notice of the ophthalmic community, it requires more emphasis. This is not a unique problem for China but a major problem for many developing and underdeveloped countries.
In response to this article, a number of questions are raised. Whether all these cases are pure fungal keratitis or mixed fungal/bacterial infections were also included? No mention was made on this, and it is important to know as the treatment modalities differ on both types. It is also unclear from the report whether all eyes were KOH smear-proved or not. Further, was there any rationale to perform KOH staining for corneal ulcer unlike dermatological fungal infection? Presently, calcoflour white and acridine orange stain have become more popular and KOH wet mount preparation is replaced by saline wet mount preparation. What is the authors' opinion?
The authors have classified the ulcers into different categories according to size. But I wonder why they have given systemic antifungal medication to all the patients even when the ulcer's size was less than 6mm. Moreover, fungal corneal ulcers require repeated debridement and (if required) keratectomy for better drug penetration. No mention was made of this aspect. The rationale for fluconazole use in all eyes was not given; this drug is not effective for all fungi and the cultures from surgically removed corneal buttons demonstrate a variety of fungal isolates including Fusarium. Conjunctival flap in active ulcer is usually not advised because of the spread of the ulcer underneath the flap. Lamellar keratoplasty in fungal ulcer is also not indicated as the fungi have the tendency for deeper involvement, even in a vertical manner [2], which is very difficult to judge on the operating table.
Infective corneal tissue removal 0.5 mm larger than the exact dimension of the corneal lesion is a worthy point; this approach accounts for negligible re-infection rate [1,3]. While surgical procedures are very well described [1], for an eye with total corneal ulcer, a sclerokeratoplasty [4] would have been a better choice than a total PKP using a 14 mm penetrating graft.
Subconjunctival injections of fluconazole at the time of surgery and for another 3 consecutive days following surgery is again confusing as discussed earlier. Topical antifungals to a recently grafted cornea could be epitheliotoxic. I would like to know the experience of the authors on this.
I agree with the authors' view that earlier surgical intervention to remove the infected tissue may help in the final outcome. But it is also equally important to make the fungi nonviable prior to therapeutic keratoplasty. Furthermore, poor outcomes in such eyes are due to (i) surgery in an inflamed eye; (ii) presence of vascularization; (iii) deeper involvement of ocular tissue by the organism; (iv) the increased incidence of operative and post-operative complications; and (v) grater need of a larger recipient window [3].
The authors have very rightly pointed out the value of histopathological evaluation of surgically removed corneal tissue following keratoplasty [2]. However, the characteristic features which may help for further management were not discussed.
Following therapeutic keratoplasty both anatomical and functional success need equal mention. Visual outcomes following therapeutic keratoplasty reported by the authors are really exciting1. Reports from various series, listed in the table below, reveal functional success between 13-60% of eyes with over 85% anatomical success [3,5-7]. Functional success of 54.7% was achieved in a previous series [3] where the graft size was less than 8.5 mm. The percentage of success receded as the size increased accounting for their excellent achievement.
Finally, I would like to know from the authors whether they had tried amniotic membrane graft prior to therapeutic keratoplasty in any eyes, as this is one of the current modes of management of recalcitrant ulcers.
Professor A Panda
Table I
Therapeutic Keratoplasty (Comparative Study)
Authors & Year
Anatomical Success
Functional Success
Sanders (1970)
13/15 (86%)
2/15 (13.3%)
Polack (1971)
15/16 (90%)
12/20 (60%)
Malik (1973)
20/20 (100%)
12/20/ (60%)
Panda (1991)
117/123 (95%)
34/123 (27.7%)
Xie (2001)
108/108 (100%)
76/108 (70.3%)
Anatomical Success: Anatomical integrity of the globe is maintained
Functional Success: Visual gain 6/60
References
(1) Xie L, Dong X, Shi W. Treatment of fungal keratitis by penetrating keratoplasty. Br J
Ophthalmol 2001;85:1070-4
(2) Panda A, Mohan M, Mukherjee G. Mycotic keratitis: Report on histopathological
evaluation. Ind Jour Ophthalmology 1984;32:311-5
(3) Panda A, Vajpayee RB, Sankar Kumar T. Critical evaluation of therapeutic
Keratoplasty in keratomycosis. Ann Ophthalmol 1991;23:373-6
(4) Panda A, Sharma N, Angra SK. Sclerokeratoplasty for total corneal ulcer. Aust NZ
J Ophthalmol 1999;27:15-9
(5) Sanders N. PK in fungal keratitis. Am J Ophthalmal 1970;70:24-30
(6) Polak M, Kaufman HE, Newmann E. Keratomycosis medical and surgical therapy.
Arch Ophthalmol 1971;85:410-6
(7) Malik SRK, Singh G. Bhatnagar PK. Therapeutic values of keratoplasty in keratomycosis. Arch Ophthalmol 1974;92:48-50
In a recent "Perspective" article by Morlet et al titled "Astigmatism and the analysis of its surgical correction" [1] there are a number of omissions and fundamental errors of content that lead to erroneous conclusions. These significant inaccuracies overlooked in the review process compromise the article's broad contribution.
In Dr Morlet's attempt to detail "the use and limitations of vector...
In a recent "Perspective" article by Morlet et al titled "Astigmatism and the analysis of its surgical correction" [1] there are a number of omissions and fundamental errors of content that lead to erroneous conclusions. These significant inaccuracies overlooked in the review process compromise the article's broad contribution.
In Dr Morlet's attempt to detail "the use and limitations of vectors. . . for the analysis of change in astigmatism" he displays an incomplete understanding of the subject. He has made a valiant attempt to assemble an abundance of historical and contemporary references on a subject of significant interest, but key material has been omitted or misquoted. This has resulted in leading statements of the article, in both the body of the text and even the conclusion that require re-evaluation and substantial revision.
The most obvious omission, is the paper's absence of any discussion of the difference vector, a precise absolute measure of surgical error described in reference 70 [2]. When the difference vector is related to the treatment (ie: TIA or target induced astigmatism vector) one has an extremely useful relative value of success of astigmatism treatment. Dr Morlet has overlooked this key vectorial entity and struggles to find any useful alternative. In sharp contrast Dr Doug Koch, Editor of the Journal of Cataract and Refractive Surgery, in his editorial introduction to the Analyzing Astigmatism issue of January 2001 [3] described the difference vector and the index of success as "remarkably useful and intuitive means of understanding the effects of the surgery".
The authors state more than once for their principle foundation of the article that "Vector analysis alone does not provide any indication of the relative value of the surgical procedure and that it (vector analysis) does not assign a value to the outcome". These statements are erroneous, and the author's failure to discuss or dispute the value of the difference vector and index of success leaves the assertion unsupported and lacking credibility. If the surgical induced astigmatism vector (SIA) (and its further translation) was the only product of vector analysis, indeed vector analysis would be a limited tool. This seems to be Dr Morlet's contention. This is far from the truth and as a result the restatement in the conclusion that "vector analysis does not give a measure of outcome" is factually inaccurate.
In addition, Dr Morlet's interpretation that the off-axis effects of treatment at 45 degrees to the surgical plane are deemed to be rotation, would more accurately be termed "torque" the component of the SIA that has been ineffective in reducing astigmatism. The relevant reference [4] describing flattening, steepening, torque and effect of off-axis treatments has been omitted from the attempt at a comprehensive list of relevant published material. The phenomena of rotation and torque are fundamentally different physical processes. The polar value at 45 degrees to the "surgical plane" quantifies the torque which causes an increase in the existing astigmatism associated with its change in orientation. It does not properly gauge the cylinder rotation where no concurrent change in the amount of existing astigmatism occurs. Rotation includes some associated flattening (or steepening) effect occurring as a result of the SIA.
The article's conclusion that "a better evaluation of the effect of astigmatism axis requires the use of the 'by the rule' or mirror equivalent axis notation, or by a manual scoring method to produce an outcome summary measure" is convoluted and unworkable. If implemented this would adversely affect the comprehension of astigmatism outcome analysis by the average general ophthalmic or refractive surgeon.
It is unfortunate the reviewers of this paper did not direct the author to other significant fallacies that merited revision. The statement "vector analysis is only valid in the early post-operative period" because "the healing response has modified the initial result of the surgery" shows the authors' failure to understand that the healing response cannot be divorced from the surgical process. It is part of it. The amount of astigmatism correction (SIA/TIA) achieved shows consistent trends over time when examining aggregate data, and this phenomenon requires surgeons to examine outcomes facilitating adjustment of nomograms based on longterm (at least 6 months) and not immediate outcomes. The later statement "the use of vector analysis over time is conceptually invalid, because unlike the initial surgical event, the wound healing process is continuous" is seriously flawed. Vector analysis is an essential component of this refinement process. In fact, vector analysis could be used to determine the astigmatic effect of the healing process itself by comparison of data at various stages in the post-operative period.
The recommendations promoted by Dr Morlet introduce greater complexity to an already complicated subject. For example, mixing negative and positive cylinder notation is unnecessary. The technique put forward does not address the changes that occur in corneal shape as measured by keratometry and topography, and cannot be readily applied when targeting non-zero goals associated with incomplete or off-axis refractive astigmatism treatments.
It is probable that the authors are careless in raising phantom "problems" for planning techniques based on incorrect quoting of information (such as reference 33). [6] The merits of this customized treatment technique are that refractive as well as keratometric data are employed (contrary to its misrepresentation that the technique "only uses keratometric data for the planning of refractive surgery").
Dr Morlet's unfortunate statement of opinion that "a lack of critical evaluation" has resulted in "the surgical vector's adoption as the de facto standard used in most reports concerning the surgical management of astigmatism" is not shared by many experienced investigative surgeons in the field. This has been shown by its admitted prevalence by the authors, and the usefulness of vectorial analysis in understanding the surgical process [5]. Indeed, many of the erroneous statements and omissions in the Perspective article might lead one to ask where the "lack of critical evaluation" actually lies.
References
(1) Morlet N, Minassian D, Dart J. Astigmatism and the analysis of its surgical
correction. Br J Ophthalmol 2001; 85:1127-1138
(2) Alpins NA. A new method of analyzing vectors for changes in astigmatism.
J Cataract Refract Surg 1993;19:524-533
(3) Koch DD. How should we analyze astigmatic data? J Cataract Refract Surg
2001;27:1-3
(4) Alpins NA. Vector Analysis of astigmatism changes by flattening, steepening
and torque. J Cataract Refract Surg 1997;23:1503-1514
(5) Alpins NA. Astigmatism analysis by the Alpins Method. J Cataract Refract
Surg 2001;27:31-49
(6) Alpins NA. New method of targeting vectors to treat astigmatism. J Cataract
Refract Surg 1997;23:63-75
Dear Editor
We have read with avid interest the article by Gupta et al. on the use of bovine pericardium as a wrapping material for hydroxyapatite orbital implants.[1] We are highly impressed by their results as none of the patients had implant extrusion. This is really commendable since implant extrusion rate has ranged from 9 % to 21 % in previous studies,[2] and it indicates meticulous technique and follow up....
Dear Editor
We read with great interest the article by Takei et al..[1] We agree with the authors that axial length (AL) measurement in silicone oil-filled eyes is a difficult situation. The need for accurate estimation of AL has increased following advances in vitreoretinal surgical techniques and improved visual results. We complement Takei and colleagues for an excellent report on the matter. CT scanning for...
I read with great interest the excellent perspective by Plsková et al1 in which they raise the issue of transient corneal opacification following corneal transplantation in the mouse model and argue that it might be due to a sufficient number of endothelia[l] cells regaining function.
What the authors describe for the mouse model, also occurs in the rat model. In fact most researchers in the rat model pr...
Dear Editor,
We thank Dr. Panda for her comments on our recent paper entitled "Treatment of fungal keratitis by penetrating keratoplasty". Dr. Panda noted correctly that treatment modalities differ on different types of keratitis. About 20% of the cases in our study were mixed infections, that is, fungal infection combined with bacterial or herpes simplex virus infection. However, the focus of our study was to s...
Dear Editor,
We have read with keen interest the article on trachomatous trichiasis by Bowman et al. We fully endorse the authors' observations that Trachoma and its sequelae are on the decline even in developing countries as we are witnessing similar trends in south-east Asia,particlarly India. However,we would like to raise a few pertinent issues.
It is our considered opinion that self-epilation of tri...
We read with interest the letter from Amin et al [1], suggesting a modification of the sub-tenon local anaesthetic injection procedure. They advocate the use of a venflon needle to penetrate the conjunctiva, with subsequent advancement of the cannula prior to anaesthetic injection. We are concerned that the use of a sharp needle should be recommended so close to the eye. Amin et al point out that the needle ti...
I congratulate Riordan-Eva et al for the article on temporal artery biopsy in the management of giant cell arteritis with neuro-ophthalmic complications.[1] This is an excellent article for residents, ER physicians, Family Practice physicians and Ophthalmologists.
The 3 cases discussed clearly show that patients over the age of 50 presenting with temporary or permanent visual loss or binocular dipl...
It was with great interest that I read the recent article by Dr. al Arab and co-workers entitled "The Burden of Trachoma and the Royal Nile Delta of Egypt; the Survey of Menofiya Governerate".[1] This work clearly shows that endemic blinding trachoma continues to be a major health problem in this area of the Nile Delta, quite close to Cairo.
My attention was particularly drawn to the high rate of recurren...
I commend Xie et al for their paper on the treatment of fungal keratitis by penetrating keratoplasty [1]. Though the subject is increasingly brought to the notice of the ophthalmic community, it requires more emphasis. This is not a unique problem for China but a major problem for many developing and underdeveloped countries.
In response to this article, a number of questions are raised. Wheth...
In a recent "Perspective" article by Morlet et al titled "Astigmatism and the analysis of its surgical correction" [1] there are a number of omissions and fundamental errors of content that lead to erroneous conclusions. These significant inaccuracies overlooked in the review process compromise the article's broad contribution.
In Dr Morlet's attempt to detail "the use and limitations of vector...
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