We thank Dr. Alm for his interest and comment on our paper entitled
“Practical recommendations for measuring rates of visual field change in
glaucoma.” We agree that the standard error of slope estimates is
dependent
on the number of examinations and duration of follow-up. However, these
two parameters are not interchangeable. As pointed out correctly by Dr.
Alm,
the same number of examinations ov...
We thank Dr. Alm for his interest and comment on our paper entitled
“Practical recommendations for measuring rates of visual field change in
glaucoma.” We agree that the standard error of slope estimates is
dependent
on the number of examinations and duration of follow-up. However, these
two parameters are not interchangeable. As pointed out correctly by Dr.
Alm,
the same number of examinations over a longer time period will lead to a
better slope estimation and therefore greater power simply because the
amount of net change is larger. Hence the difference in follow-up of 3 (27 compared to 24 months) months in his example yields an additional change
of -0.5 dB in Mean Deviation and therefore the number of examinations
derived to obtain equivalent power is not surprising.
The goal of our first recommendation of 6 examinations in the first
two years
was not to determine whether the slope of visual field decay is
statistically
significant or not. It was to identify patients who we feel are
progressing
rapidly. In these patients we do not feel that prolonging the follow-up
is an
adequate substitute for more frequent examinations. Even if equivalent
statistical power is obtained with this approach, prolonging the follow-up comes with the very significant cost of more visual field loss.
Our paper was meant to be an initial guideline for clinicians on what rates of visual field change could be detected (with varying degrees of power) with a
given frequency of examinations. We would like to emphasise that there is a large distinction between detection of progression and determining the
rate of visual field change. Therefore the proposed guidelines are not necessarily
designed to detect progression. We welcome the comments of Dr. Alm and others that encourage us to factor in aspects such as the time-separation
between tests and measures besides Mean Deviation which consider the
location of visual field defects.
Sincerely,
BC Chauhan, DF Garway-Heath, FJ Goñi, L Rossetti, B Bengtsson, AC
Viswanathan and A Heijl
There are many pertinent and interesting observations in your
article. As one of the first few users of PASCAL in India, we have now a
large data-base of patients in a short span of time. Critical to
understanding PASCAL is the fluence. Contrary to what we always thought,
retinal hemorrhages and acoustic damage are not seen at 10 ms pulses if
the fluence is within limits. I wish that PASCAL was also programmed to
fix the flue...
There are many pertinent and interesting observations in your
article. As one of the first few users of PASCAL in India, we have now a
large data-base of patients in a short span of time. Critical to
understanding PASCAL is the fluence. Contrary to what we always thought,
retinal hemorrhages and acoustic damage are not seen at 10 ms pulses if
the fluence is within limits. I wish that PASCAL was also programmed to
fix the fluence level at the beginning of each procedure (titrated for each eye) so that inadvertently fluence does not shoot up when the spot size
is changed. PASCAL has really taken out the sting from PRP.
In the article entitled 'Electrophysiological effects of intravitreal
Avastin (bevacizumab) in the treatment of exudative age-related macular
degeneration (ARMD)' by Karanjia et al (Br J Ophthalmol 2008), the authors
examine the sensitivity of multifocal-electroretinogram (mfERG) at
measuring changes in retinal electrical activity in response to Avastin
treatment for ARMD.
In this interesting paper t...
In the article entitled 'Electrophysiological effects of intravitreal
Avastin (bevacizumab) in the treatment of exudative age-related macular
degeneration (ARMD)' by Karanjia et al (Br J Ophthalmol 2008), the authors
examine the sensitivity of multifocal-electroretinogram (mfERG) at
measuring changes in retinal electrical activity in response to Avastin
treatment for ARMD.
In this interesting paper the authors study the changes of P1 response
amplitude and support that this is the first study to demonstrate a
statistically significant change in retinal electrical activity post-bevacizumab in patients with ARMD.
I would like to draw attention to the authors of this article that in our
prospective study 'Intravitreal use of bevacizumab (Avastin) for
choroidal neovascularization due to ARMD: a preliminary mfERG and OCT
study' by Moschos MM et al (Doc Ophthalmol 2007; 114:37-44) really for
the first time we evaluated the macular function before and after
intravitreal use of Avastin.
In our paper based on the study of 18 eyes, 1 month after treatment the
retinal response density of mfERG really shows an improvement but 3 months
after treatment no difference was found between baseline and 3 months.
Our results show that there are anatomical correlates to support the
concept of disease amelioration 1 month after treatment. This is mainly
the decrease of macular thickness as measured by OCT in an extremely
significant degree (p<0.001) the first month after treatment. On the
contrary the mean visual acuity improved only by 0.03 the first month
after treatment and by 0.02 three months after treatment. On the contrary
the mfERG improvement did not follow the decrease of macular thickness and
is significant only the first month after treatment. These findings show
that the increase of visual acuity, as also the improvement of electrical
responses of the macular area is disproportional to the decrease of
macular thickness. This may be explained by the fact that macular edema
is only a parameter that may affect visual acuity and electrophysiological
responses in the beginning of the disease. Atrophy of the retina,
particularly of the photoreceptors, atrophy of the pigment epithelium and
scarring are all unmeasured variables, which influence vision [1, 2].
References
1. Moschos M, Brouzas D, Apostolopoulos M, et al. Intravitreal use of
bevacizumab (Avastin) for choroidal neovascularization due to ARMD: a
preliminary multifocal-ERG and OCT study. Doc Ophtalmol 2007;114:137-144.
2. Moschos M, Panayotidis D, Theodossiadis G, et al. Assessment of macular
function by electroretinography in age-related macular degeneration before
and after photodynamic therapy. J Fr Ophtalmologie 2004;27:1001-1006.
Marilita M Moschos, MD, PhD
Department of Ophthalmology, University of Athens, Athens, Greece
Correspondence and reprints:
Moschos M. Marilita MD, PhD
144, Kountouriotou Str
185 35 Piraeus
Greece
Tel : ++30 6944887319
Fax: ++30 210 4122139
E-mail: moschosmarilita@yahoo.fr
This is an interesting haematological syndrome. I would question calling
the occurrence simultaneous when the vision loss was symptomatically
sequential. Roughly 20% of normals have areas of absent choroidal
filling in the early venous phase of the retinal circulation. These
areas fill suddenly as the dye arrives in a normal manner; if there is
true pathological delay such as occurs with giant cell arteritis the...
This is an interesting haematological syndrome. I would question calling
the occurrence simultaneous when the vision loss was symptomatically
sequential. Roughly 20% of normals have areas of absent choroidal
filling in the early venous phase of the retinal circulation. These
areas fill suddenly as the dye arrives in a normal manner; if there is
true pathological delay such as occurs with giant cell arteritis the
areas tend to fill slowly and from the edges. It can not be called
pathological relative choroidal perfusion delay till the retinal
circulation has reached the mid venous phase as defined by the vein
being half filled with fluorescence. The most common cause for a delay
from injection to the early venous phase is a mild vasovagal reaction or
a reduced cardiac output in a patient with atrial fibrillation. The time
from injection thus cannot be used to define choroidal perfusion delay.
We read with interest the recent study by Krebs et al. demonstrating the limitations of StratusOCT mapping software in the context of age-related macular degeneration (AMD).[1] We wish to applaud the authors for their study - while the limitations of StratusOCT automated analysis have previously been reported,[2] the fact remains that many ophthalmologists may not be well acquainted with these errors. We agree wi...
We read with interest the recent study by Krebs et al. demonstrating the limitations of StratusOCT mapping software in the context of age-related macular degeneration (AMD).[1] We wish to applaud the authors for their study - while the limitations of StratusOCT automated analysis have previously been reported,[2] the fact remains that many ophthalmologists may not be well acquainted with these errors. We agree with the authors and wish to underline the importance of these errors in this era of optical coherence tomography (OCT)-guided retreatment regimens for anti-angiogenic agents and increasing adoption of quantitative OCT measurements as secondary outcome parameters in clinical trials.[3]
In their study, the authors present evidence that automated Stratus software provides correct results in only 57.1% of eyes with AMD.[1] These results are consistent with previous reports and in line with clinical experience.[2] As mentioned in the discussion, manual placement of boundaries on OCT scans may represent a solution to this problem. We wish to thank the authors for mentioning our custom OCT grading software termed “OCTOR” as one possible software tool to perform this kind of analysis. The authors comment that "this software is not commercially available or supported by the StratusOCT". However, OCTOR was designed specifically with StratusOCT in mind and readily handles raw exported StratusOCT images. OCTOR is publicly available and can be downloaded from www.diesel.la. This software facilitates manual segmentation of OCT images and allows quantitative analysis of any area of interest in these images e.g. retina, subretinal fluid, subretinal tissue, or pigment epithelium detachment.[4] Furthermore, the most recent version of the Stratus OCT software (version 5.0) enables users to manually correct errant boundaries.
In their discussion, the authors comment that "manually set boundary lines would add subjectivity to the retinal thickness measurements". Recent research demonstrating both the accuracy and reproducibility of manual grading with OCTOR software in the setting of neovascular AMD suggests that manual grading does not necessarily add subjectivity to retinal thickness measurements.[5] Instead, manually corrected boundaries allow for more reliable data than the frequently erroneous automated boundary detection of the StratusOCT software. We recently used the manual grading software OCTOR to quantify the volumes of the neurosensory retina, subretinal fluid, subretinal tissue, and pigment epithelial detachments. Intergrader comparisons showed a high level of agreement and a strong correlation between measurements for all spaces (weighted Kappa= 0.72-0.97; ICC = 0.92-0.99). Although these values were obtained by graders who had undergone a formal certification program in our reading center, in our experience OCT grading can be learned both more quickly, and more easily, than grading of fluorescein angiography. This hypothesis is supported by the level of agreement between measurements in our study which was appreciably better than that which has been reported elsewhere for fluorescein angiography.[6]
Although significant progress is being made, the complex morphology of neovascular AMD presents a challenge to the development of automated OCT interpretation software. As automated segmentation algorithms improve, it will be necessary to assess their efficacy in a quantitative manner against a 'gold standard'. We believe that the accuracy of manual segmentation by trained human graders is such that it could serve as a 'gold standard' against which to compare the results of automated analysis.
In conclusion, we wish to commend the authors for highlighting this area, which is likely to be of critical importance as the next generation of OCT technology is incorporated into the diagnosis and management of neovascular AMD.
LICENCE FOR PUBLICATION:
The Corresponding Author has the right to grant on behalf of all authors, and does grant on behalf of all authors, an exclusive licence on a worldwide basis to the BMJ Publishing Group Ltd to permit this article (if accepted) to be published in BJO and any other BMJPGL products and sublicences such use and exploit all subsidiary rights, as set out in our licence (http://bjo.bmj.com/ifora/licence.pdf).
COMPETING INTERESTS:
Drs. Walsh and Sadda are co-inventors of Doheny intellectual property related to spectral domain optical coherence tomography that has been licensed by Topcon Medical Systems.
FUNDING:
Supported in part by NIH Grant EY03040 and NEI Grant R01 EY014375
References
1. Krebs I, Haas P, Zeiler F, Binder S. Optical coherence tomography: limits of the retinal-mapping program in age-related macular degeneration. Br J Ophthalmol 2008;92:933-5.
2. Sadda SR, Wu Z, Walsh AC, et al. Errors in retinal thickness measurements obtained by optical coherence tomography. Ophthalmology 2006;113:285-93.
3. Fung AE, Lalwani GA, Rosenfeld PJ, et al. An optical coherence tomography-guided, variable dosing regimen with intravitreal ranibizumab (Lucentis) for neovascular age-related macular degeneration. Am J Ophthalmol 2007;143:566-83.
4. Sadda SR, Joeres S, Wu Z, et al. Error correction and quantitative subanalysis of optical coherence tomography data using computer-assisted grading. Invest Ophthalmol Vis Sci 2007;48:839-48.
5. Joeres S, Tsong JW, Updike PG, et al. Reproducibility of quantitative optical coherence tomography subanalysis in neovascular age-related macular degeneration. Invest Ophthalmol Vis Sci 2007;48:4300-7.
6. Holz FG, Jorzik J, Schutt F, et al. Agreement among ophthalmologists in evaluating fluorescein angiograms in patients with neovascular age-related macular degeneration for photodynamic therapy eligibility (FLAP-study). Ophthalmology 2003;110:400-5.
We appreciate Dr. Kadyan’s letter regarding our study “Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ)” [1]. He requests clarification on several issues and, to the best of our ability we will attempt to respond to each in turn.
Regarding the proportion of cases and controls diagnosed with glauco...
We appreciate Dr. Kadyan’s letter regarding our study “Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ)” [1]. He requests clarification on several issues and, to the best of our ability we will attempt to respond to each in turn.
Regarding the proportion of cases and controls diagnosed with glaucoma, this information appears in Table 1 of the published manuscript.
Regarding exclusion criteria for the control group, as stated in the published manuscript the controls were randomly selected from patients seen in the Department of Ophthalmology clinic for reasons other than NAION; there were no other exclusionary criteria. With respect to the other ocular diagnoses of the control group, we did not collect this information. We also do not have information on the results of any sleep studies the study participants may have obtained.
Finally, regarding which of the specific sleep apnea syndrome symptoms in the SA-SDQ were associated with NAION, it appears that the cases reported more frequent loud snoring (or bothering others), having nose block up when wanting to sleep, and snoring/breathing getting worse when sleeping on the back compared to controls. There were no statistically significant differences for the other SAS specific items nor for any of the non-SAS items (e.g., body mass index, smoking status). Furthering these analyses to create a weighted score is an interesting idea and something we may consider pursuing in the future.
Regards,
Gerald McGwin, Jr., M.S., Ph.D.
Cynthia Owsley, Ph.D., M.S.P.H.
Departments of Epidemiology and Ophthalmology
University of Alabama at Birmingham
Birmingham, Alabama
References
1. Li J, McGwin G, Vaphiades, Owsley C. Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ). Br J Ophthalmol. 2007;91:1524-7.
We thank Dr Munier and Dr Satgé for their interest in our work on
“Aggressive metastasising adenocarcinoma of the retinal pigment epithelium
with trisomy 21” [1] and welcome the opportunity to respond to their
comments.
We are in agreement with Dr Munier and Dr Satgé that life-threatening
ophthalmic tumours must be kept in mind while taking care of patients with
Down syndrome. Despite an imp...
We thank Dr Munier and Dr Satgé for their interest in our work on
“Aggressive metastasising adenocarcinoma of the retinal pigment epithelium
with trisomy 21” [1] and welcome the opportunity to respond to their
comments.
We are in agreement with Dr Munier and Dr Satgé that life-threatening
ophthalmic tumours must be kept in mind while taking care of patients with
Down syndrome. Despite an important progress in life expectancy, solid
tumours of the eye and ocular adnexa remain very rare in these patients
[2].
In our case report we describe a 37-year-old man with trisomy 21 who
presented with a longstanding blind eye with opaque media. Histopathology
revealed an aggressive adenocarcinoma of the retinal pigment epithelium
(RPE) with marked invasion of the choroid, retina, sclera, orbital and
cranial optic nerve and subarachnoid space. The tumour seeded into the
lumbar spinal-cord space, and metastatic foci developed in the parietal
lobe and cerebellopontine angle [1].
However, the aggressive behaviour of this tumour is clearly atypical
for the usual tumour reported as RPE adenocarcinoma in the literature. The
fact that aggressive tumor extension and metastasis occur in a middle-aged
patient with trisomy 21 is quite remarkable.
Although the most frequent malignant intraocular tumor in blind eyes
with opaque media is choroidal melanoma [3], other malignancies with
invasive features and metastatic potential, such as adenocarcinoma of the
RPE, must be considered in the clinical management, even in patients with
Down syndrome.
References
1. Heindl LM, Naumann GOH, Kruse FE, Holbach LM. Aggressive metastasising
adenocarcinoma of the retinal pigment epithelium with trisomy 21. Br J
Ophthalmol 2008;92:389-91.
2. Satgé D, Lacombe D, Vekemans M, Bonnet A, Réthoré MO, Munier F. A
survey of ocular tumors in Down syndrome alone or associated with another
genetic affection. Int J Disabil Human Dev 2006;5:311-7.
3. De Gottrau P, Holbach LM, Naumann GOH. Clinicopathological review of
1146 enucleations (1980-90). Br J Ophthalmol 1994;78:260-5.
How often should we do visual fields in the first 2 years? Chauhan
and co-workers [1] recommend 3 visual fields per year. It will have an 80%
power of detecting a rate of loss of 2 dB/year in an eye with moderate
variability. Is this a significant improvement over 2 fields per year? In
order to answer that we should look at the efficacy of increasing the
frequency of field examinations versus prolongin...
How often should we do visual fields in the first 2 years? Chauhan
and co-workers [1] recommend 3 visual fields per year. It will have an 80%
power of detecting a rate of loss of 2 dB/year in an eye with moderate
variability. Is this a significant improvement over 2 fields per year? In
order to answer that we should look at the efficacy of increasing the
frequency of field examinations versus prolonging the duration of the
follow-up. From regression theory it is clear that the ability to detect a
statistically significant slope is determined by the variability of
measurement (MD), the number of observations/examinations and the span
along the X-axis (duration of follow-up). Furthermore, increasing the
duration is much more efficient than increasing the frequency of
examinations. Thus, 5 examinations in 1.7 years will not be able to detect
the same slope as 5 examinations in 5 years! The total amount of change
(rate * duration) will be much lower, and, as pointed out by the authors,
the amount of change affects power. Planning of a longitudinal study is a
useful parallel. Extensive tables, based on regression theory, on the
effect of number of examinations and duration of the study on the
precision of the estimate of the linear regression line have been
published.[2]From these tables it can be seen that five measurements,
evenly spread over 27 months, have the same power to detect a
statistically significant slope as seven measurements over 24 months. Thus
a visual field every 6 month’ the first two years would seem to be an
optimal frequency, if the goal is to determine if the slope of the
regression line is statistically significant or not.
References
[1] Chauhan BC, Garway-Heath DF, Goñi FJ, Rossetti L, Bengtsson B,
Viswanathan AC, and Heijl A. Practical recommendations for measuring rates
of visual field change in glaucoma. Br J Ophthalmol. 2008;92:569-73.
[2] Schlesselman JJ. Planning a longitudinal study: II. Frequency of
measurement and study duration. J Chron Dis. 1973;26:561-570.
Vitreous buffering capacity as a mechanism for silicone oil optic neuropathy
Dear editors
I read with interest the article concerning silicone oil optic
neuropathy
by Knecht et al in October issue of BJO. In that article they
suggest
an active transport of silicone oil into the optic nerve as a mechanism
for optic neuropathy. [1] I would like to suggest a new mechanism based
on buffering capacity...
Vitreous buffering capacity as a mechanism for silicone oil optic neuropathy
Dear editors
I read with interest the article concerning silicone oil optic
neuropathy
by Knecht et al in October issue of BJO. In that article they
suggest
an active transport of silicone oil into the optic nerve as a mechanism
for optic neuropathy. [1] I would like to suggest a new mechanism based
on buffering capacity of normal vitreous as a cause of silicone oil
optic neuropathy.
Conway et al demonstrated buffering capacity for bovine vitreous, when
it was incubated with 5%CO2 -95% air mixture. [2]
Buffering capacity of vitreous is largely dependent on bicarbonate-
CO2 system. This system is the most important buffer in the
extracellular fluid. [3] If we consider vitreous as like as the plasma
regarding its
CO2 content, we will need 5%CO2 over the vitreous to demonstrate vitreous
buffering effect. (5%*760mm Hg=38mm Hg so closed to normal 40mmHg P CO2 of
plasma)
Water in vitreous cavity may have buffering capacity comparable to
vitreous itself. Remember that 99% of normal vitreous is water.In the
presence of carbonic anhydrase as the catalyst and 40 mmHg of P CO2 in
nearby blood and interstitial tissue, which is in dynamic equilibrium
with this water, this buffering capacity is expected either for normal
vitreous or balanced salt solution.
Buffering capacity is also dependent on volume of buffer, so with
replacement of water content of vitreous with silicone oil the buffering
capacity might be decreased significantly or even lost.
Retinal nerve fiber in contact with a fluid which doesn't support PH
homeostasis will be at risk for more degeneration, and silicone oil-associated optic nerve degeneration could occur. [4]
Mehdizadeh M MD
Shiraz University of Medical Sciences
Shiraz, IRAN
References
1. Knecht P, Groscurth P, Ziegler U,et al. Is silicone oil optic
neuropathy caused by high intraocular pressure alone? A semi-biological
model.Br J Ophthalmol. 2007;91:1293-5
2. Conway M D,Jermak CM,Peyman GA
et al.Buffering capacity of bovine vitreous. Retina 2008;28: 150-153
3.
Berne R M Levy M N :Principles of physiology.St Louis C.V.Mosby
1990:470
4. Budde M, Cursiefen C, Holbach LM, et al. Silicone
oil-associated optic nerve degeneration. Am J Ophthalmol 2001; 131:
392-4
We read with interest the study from Moutray et al[1] that found
Optical Coherence Tomography (OCT) measures are not robust markers for
visual function. We have looked at 20 patients with wet age related
macular degeneration (AMD) and compared visual function and OCT measures
using the new generation of Fourier Domain 3D OCT. We also find no
significant correlation between OCT measurements of central...
We read with interest the study from Moutray et al[1] that found
Optical Coherence Tomography (OCT) measures are not robust markers for
visual function. We have looked at 20 patients with wet age related
macular degeneration (AMD) and compared visual function and OCT measures
using the new generation of Fourier Domain 3D OCT. We also find no
significant correlation between OCT measurements of central foveal
thickness, maximum retinal thickness and distance LogMar acuity, near
vision and contrast sensitivity. We believe that this data is relevant to
the use of ranibizumab in the UK.
The licence for the use of ranibizumab (Lucentis) in the UK is for a
loading phase of one injection per month for three consecutive months,
followed by a maintenance phase in which patients should be monitored for
visual acuity every month. If the patient experiences a loss of greater
than 5 letters in visual acuity (EDTRS) or one Snellen line equivalent,
ranibizumab should be administered.
The PrONTO[2] study however, used visual and OCT criteria to make
retreatment decisions. Retreatment was carried out if there was a loss of
5 letters in conjunction with fluid in the macula as detected by OCT, or
an increase in OCT central retinal thickness of at least 100 microns along
with other non- OCT guided criteria. More than a quarter of the study
participants did not lose 5 letters of vision but had an increase in OCT
central retinal thickness of at least 100 microns. Results from this study
still showed a comparable proportion of patients (35% vs 33%) gaining 15
letters or more compared to the MARINA[3] trial where monthly dosing was
carried out regardless of vision or OCT findings.
These studies suggest that visual function alone does not relate to
the presence or absence of intraretinal and/or subretinal fluid in a
significant proportion of patients which may signify the recurrence of the
CNV. We therefore believe that Moutray et al’s study adds weight to the
argument that visual function and OCT measurements should jointly be
considered as criteria for retreatment with ranibizumab in order to
maintain the level of vision achieved after the loading phase.
References
1. Moutray T, Alarbi M, Mahon G, et al. Relationships between clinical
measures of visual function, fluorescein angiographic and optical
coherence tomography features in patients with subfoveal choroidal
neovascularisation. British Journal of Ophthalmology 2008;92(3):361-364.
2. Fung AE, Lalwani GA, Rosenfeld PJ, et al. An optical coherence
tomography-guided, variable dosing regimen with intravitreal ranibizumab
(Lucentis) for neovascular age-related macular degeneration. American
Journal of Ophthalmology 2007;143(4):566-583.
3. Rosenfeld PJ, Brown DM, Heier JS, et al. Ranibizumab for neovascular age-related macular degeneration. New England Journal of Medicine
2006;355(14):1419-1431.
Dear Editor
We thank Dr. Alm for his interest and comment on our paper entitled “Practical recommendations for measuring rates of visual field change in glaucoma.” We agree that the standard error of slope estimates is dependent on the number of examinations and duration of follow-up. However, these two parameters are not interchangeable. As pointed out correctly by Dr. Alm, the same number of examinations ov...
There are many pertinent and interesting observations in your article. As one of the first few users of PASCAL in India, we have now a large data-base of patients in a short span of time. Critical to understanding PASCAL is the fluence. Contrary to what we always thought, retinal hemorrhages and acoustic damage are not seen at 10 ms pulses if the fluence is within limits. I wish that PASCAL was also programmed to fix the flue...
Dear Editor,
In the article entitled 'Electrophysiological effects of intravitreal Avastin (bevacizumab) in the treatment of exudative age-related macular degeneration (ARMD)' by Karanjia et al (Br J Ophthalmol 2008), the authors examine the sensitivity of multifocal-electroretinogram (mfERG) at measuring changes in retinal electrical activity in response to Avastin treatment for ARMD. In this interesting paper t...
This is an interesting haematological syndrome. I would question calling the occurrence simultaneous when the vision loss was symptomatically sequential. Roughly 20% of normals have areas of absent choroidal filling in the early venous phase of the retinal circulation. These areas fill suddenly as the dye arrives in a normal manner; if there is true pathological delay such as occurs with giant cell arteritis the...
We read with interest the recent study by Krebs et al. demonstrating the limitations of StratusOCT mapping software in the context of age-related macular degeneration (AMD).[1] We wish to applaud the authors for their study - while the limitations of StratusOCT automated analysis have previously been reported,[2] the fact remains that many ophthalmologists may not be well acquainted with these errors. We agree wi...
We appreciate Dr. Kadyan’s letter regarding our study “Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ)” [1]. He requests clarification on several issues and, to the best of our ability we will attempt to respond to each in turn. Regarding the proportion of cases and controls diagnosed with glauco...
Dear Editors
We thank Dr Munier and Dr Satgé for their interest in our work on “Aggressive metastasising adenocarcinoma of the retinal pigment epithelium with trisomy 21” [1] and welcome the opportunity to respond to their comments.
We are in agreement with Dr Munier and Dr Satgé that life-threatening ophthalmic tumours must be kept in mind while taking care of patients with Down syndrome. Despite an imp...
Dear Editors
How often should we do visual fields in the first 2 years? Chauhan and co-workers [1] recommend 3 visual fields per year. It will have an 80% power of detecting a rate of loss of 2 dB/year in an eye with moderate variability. Is this a significant improvement over 2 fields per year? In order to answer that we should look at the efficacy of increasing the frequency of field examinations versus prolongin...
Vitreous buffering capacity as a mechanism for silicone oil optic neuropathy
Dear editors
I read with interest the article concerning silicone oil optic neuropathy by Knecht et al in October issue of BJO. In that article they suggest an active transport of silicone oil into the optic nerve as a mechanism for optic neuropathy. [1] I would like to suggest a new mechanism based on buffering capacity...
Dear Editors
We read with interest the study from Moutray et al[1] that found Optical Coherence Tomography (OCT) measures are not robust markers for visual function. We have looked at 20 patients with wet age related macular degeneration (AMD) and compared visual function and OCT measures using the new generation of Fourier Domain 3D OCT. We also find no significant correlation between OCT measurements of central...
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