Dear Editor,
We appreciate the interest shown by Jagat Ram et al and their well advised
comments on our paper titled, 'Population-based assessment of vision-
related quality of life in corneal disease: results from the CORE study.'1
As per their observation on the number of controls studied under marital
status (n=435) in Table 1, the typographical error has been corrected and
the change has been highlighted and the edited secti...
Dear Editor,
We appreciate the interest shown by Jagat Ram et al and their well advised
comments on our paper titled, 'Population-based assessment of vision-
related quality of life in corneal disease: results from the CORE study.'1
As per their observation on the number of controls studied under marital
status (n=435) in Table 1, the typographical error has been corrected and
the change has been highlighted and the edited section of Table 1 is shown
below. Now, the number of controls adds up to 435.
Table 1: Vision Function
scores by socio-demographic factors in cases and controls*
Marital Status
Cases (n=435)
Controls (n=435)
General functioning scale
Psycho-social impact scale
Visual symptom scale
n (%)
n (%)
Case
Control
Case
Control
Case
Control
Married
303 (69.7)
403 (92.6)
26 (22-32)
P = 0.001#
22 (21-25)
P = 0.5
6 (5-10)
P = 0.001#
5 (5-6)
P = 0.7
13 (9-21)
P = 0.001#
9 (7-13)
P = 0.7
Unmarried/
132 (30.3)
32 (7.4)
34 (26-58)
23 (21-25)
8 (6-15.5)
5 (5-6)
17 (11-28)
9 (8-13.5)
Widow/ Widower
Total
-
-
28 (23-39)
22 (21-25)
6 (5-12)
5 (5-6)
14 (9-23)
9 (7-13)
*Data presented as Median
(p25 p75) of VFQ scores
#Statistically
significant difference between groups
We agree with the second comment raised by the authors that bilateral
corneal conditions affect VR-QoL to a greater level than unilateral
corneal conditions, but the authors miss a mark here by not taking visual
impairment into account. The results presented in our paper are a part of
a well planned population-based epidemiological study and we cannot
question the results on clinical beliefs. As shown in our paper, visual
impairment (based on visual acuity in both eyes) due to corneal disease
affects VR-QoL significantly. Moreover, a point to note, is that VR-QoL is
dependent on visual acuity and not on ocular involvement. Bilateral
corneal conditions like pterygium and paracentral opacities with mild or
no visual impairment, do not affect VR-QoL to a greater degree than a
unilateral, total corneal opacity due to bullous keratopathy or trauma.
Hence, bilateral corneal involvement may have more effect on the quality
of life as compared to unilateral cases, considering visual impairment is
similar in both sub-groups. Activities of daily living, as well as the
ability to drive vehicles would be affected more in bilateral cases with
significant visual impairment.
The third point the authors raise is the variance of quality of life
with the grade of corneal opacity. The grade of corneal opacity in the
present study was graded as per the type (nebular, macular, leucoma),
location, size and depth of involvement. A total of 571 eyes of 435
patients were detected with corneal opacity. For the purpose of analysis,
the corneal opacity was divided into three grades ranging from mild to
severe. As the VFQ scores were recorded per person and the corneal opacity
was recorded eyewise, some cases had to be excluded from analysis. All
unilateral cases and bilateral cases with same grade of corneal opacity in
both eyes were used to compute VFQ scores in different grades of corneal
opacity. Forty cases with dissimilar grade of corneal opacity in two eyes
were excluded. The table below shows the variance of VR-QoL with grade of
corneal opacity and demonstrates that VR-QoL varies significantly in the
first two domains of vision function.?
Table 2: Vision Function scores by grade of corneal opacity in the study
population (n=395)*
Type of Corneal Opacity
General functioning scale
Psycho-social impact scale
Visual symptom scale
Mild (80)
26(22-44)
6(5-12)
14(9-21)
Moderate (185)
27(23-34)
6(5-9)
13(9-21)
Severe (130)
29(23-40)
7(6-13)
14(11-25)
P value
0.003*
0.042*
0.143
*Data presented as Median
(p25 p75) of VFQ scores
#statistically significant
difference between groups
Again, we would like to reiterate that the results presented in our paper
are a part of a well planned population-based epidemiological study and
demonstrate the findings in this rural population. It is possible that
married population in our study had better quality of life as compared to
unmarried or widows/widowers in contrast to other populations described in
earlier reports. We further explored reasons for this observation and we
found that the married population was younger (Mean age=57.5 vs 69.9 of
unmarried/divorced population). Hence, age could play as a confounding
factor in this association.
References:
1. Vashist P, Gupta N, Tandon R, Gupta SK, Dwivedi S, Mani K. Population-
based assessment of vision-related quality of life in corneal disease:
results from the CORE study. Br J Ophthalmol. 2016 May;100(5):588-93.
eLetter
Comment on: Anatomical effects of dexamethasone intravitreal implant in
diabetic macular oedema: a pooled analysis of 3-year phase III trials
Parul Chawla Gupta, MS; Jagat Ram, MS, FAMS
Department of Ophthalmology
Post Graduate Institute of Medical Education and Research, Chandigarh,
India, 160012
Corresponding author
Dr. Jagat Ram, MS, FAMS
Professor and Head
Department of Ophthalmology
Post Graduate Institute of M...
eLetter
Comment on: Anatomical effects of dexamethasone intravitreal implant in
diabetic macular oedema: a pooled analysis of 3-year phase III trials
Parul Chawla Gupta, MS; Jagat Ram, MS, FAMS
Department of Ophthalmology
Post Graduate Institute of Medical Education and Research, Chandigarh,
India, 160012
Corresponding author
Dr. Jagat Ram, MS, FAMS
Professor and Head
Department of Ophthalmology
Post Graduate Institute of Medical Education and Research, Chandigarh,
India, 160012
Email id: drjagatram@gmail.com
Conflict of interest and source of funding- None declared
Dear Editor,
We read with interest the recent paper by Danis [1] and associates
assessing the long-term effects of dexamethasone intravitreal implant (DEX
implant) monotherapy on retinal morphology in diabetic macular edema
(DME). While the study is indeed interesting, there are certain points we
wish to highlight. Firstly, among the previously treated eyes what was the
mean interval between DEX injection and any previous treatment since it
may confound the results. A recent study by Chhablani [2] et al, showed
significant difference (P= 0.016) between the longest treatment-free
interval between the groups that is, 10.5? 7.8 and 7.0? 4.4 months among
treatment naive and previously treated eyes, respectively. What was the
longest treatment-free interval in previously treated and na?ve eyes post
DEX implant in the present study? Secondly, how many patients had
vitreomacular traction syndrome or epiretinal membrane? Thirdly, in a
meta-analysis of observational studies carried out by Zhang and colleagues
[3] evaluating the effect of insulin use on the risk of developing macular
edema, it was seen that insulin use increased the risk of macular edema.
In few studies [3, 4], the risk for macular edema was greater in patients
receiving pioglitazone/rosiglitazone than in those who did not. In
addition, combining pioglitazone with insulin was associated with an even
greater risk for macular edema, with patients having a more than 11-fold
increased risk compared with diabetic patients who did not receive the 2
drugs. Hence, the authors need to take into account the number of patients
on oral hypoglycemic like pioglitazone/rosiglitazone and those who shifted
to insulin therapy during follow up. History of aspirin use and ACE
inhibitor use should be enquired as they are shown to be associated with a
reduced risk of DME. Fourthly, "at the final study visit, the decline in
the proportion of study eyes in this category was greater with DEX implant
0.7 mg (from 94.5% at baseline to 60.2%) and DEX implant 0.35 mg (from
94.8% to 58.7%) than with sham (from 95.9% to 71.6%)" and "the 10th
percentile of time to two-step improvement in diabetic retinopathy
severity was ?24 and ?13 months for the DEX implant 0.7 and 0.35 mg
treatment groups versus ?24 months for sham". Do the authors imply that
the 0.35 mg DEX implant is as efficacious as the 0.7 mg implant or does it
suggest better sustained metabolic control in the patients receiving the
0.35 mg implant? Moreover, since systemic hypertension is a risk factor
for the development and progression of both diabetic retinopathy and DME,
and hyperlipidemia increases the risk of leakage and exudative deposits in
the macula [5], blood pressure and lipid profile should have been recorded
at baseline and at subsequent visits to assess whether improvement in
macular edema was as a result of strict systemic control or as a result of
the implant itself. Lastly, since steroids exacerbate cataractous changes,
it would be interesting to know the lens status in the three groups at
final follow up.
References
1. Danis RP, Sadda S, Li XY, et al. Anatomical effects of dexamethasone
intravitreal implant in diabetic macular oedema: a pooled analysis of 3-
year phase III trials. Br J Ophthalmol 2016;100:796-801.
2. Chhablani J, Bansal P, Veritti D, et al. Dexamethasone implant in
diabetic macular edema in real-life situations. Eye 2016;30:426-430.
3. Zhang J, Ma J, Zhou N, Zhang B, An J. Insulin Use and Risk of Diabetic
Macular Edema in Diabetes Mellitus: A Systemic Review and Meta-Analysis of
Observational Studies. Medical Science Monitor?: International Medical
Journal of Experimental and Clinical Research. 2015;21:929-936.
4. Idris I, Warren G, Donnelly R. Association between thiazolidinedione
treatment and risk of macular edema among patients with type 2 diabetes.
Arch Intern Med 2012;172:1005-1011.
5. Gardner TW, Antonetti DA, Barber AJ, LaNoue KF, Levison SW. Diabetic
retinopathy: more than meets the eye. Surv Ophthalmol. 2002; 47(suppl 2):
S253-S262.
Dear Editor
I would like to thank the authors for their recent editorial "Eye hazards of laser 'pointers' in perspective" and that I agree and support the majority of points raised within the article. However I would like to correct one assertion made regarding the pilot injury reported by my team, that was published as a case report in January 2016. I would like to clarify some facts; the laser illumination incident was witnesse...
Dear Editor
I would like to thank the authors for their recent editorial "Eye hazards of laser 'pointers' in perspective" and that I agree and support the majority of points raised within the article. However I would like to correct one assertion made regarding the pilot injury reported by my team, that was published as a case report in January 2016. I would like to clarify some facts; the laser illumination incident was witnessed by both the pilot (victim) and captain, in addition to being subject to a police investigation. The pilot recalls how a blue laser beam illuminated from the right side of the cockpit, the pilot was sat on the right side of the flight deck at an altitude of 1300 feet. He recalls looking towards the laser beam by tilting his head slightly towards the right side; with the beam directly entering his right eye. Obviously concerned about the risk of blindness and injury, the pilot self presented to his local eye casualty department. He suffered temporary flash blindness immediately after the 'laser illumination' event, which once resolved left a blind spot within the superonasal field of the right eye. This corresponded to a mild focal laser retinal injury that was just visible on ophthalmoscopy, but clearly evident on fundus autofluorescence and ocular coherence tomography. The pilot was no longer subjectively aware of any blindspot in his vision a few weeks later, with a 24-2 Humphrey visual field found to be within normal limits. The lesion was uniocular, with no evidence of any retinal lesion in the fellow eye, either clinically or on retinal imaging. The retinal lesion has been monitored longitudinally over the last 18 months with evidence of healing commensurate with a retinal laser injury. Recently, the sensitivity of retinal lesion has been tested more accurately using fundus controlled microperimetry, with stimuli presented on the affected area; with focal reduction in retinal sensitivity over the retinal burn, with preserved retinal sensitivity within surrounding retina. Suggesting had the angle been different, and the fovea had been involved it would have resulted in visual loss; and potentially the end of this pilot's career.
I as a retinal specialist, given the history provided to me by the patient and clinical findings identified on examination, alongside retinal imaging and my personal experience of treating eyes with retinal laser: I can only come to a single conclusion that the retinal lesion on this pilot's right eye was the result of the laser injury. Possibly due to the use of ocular coherence tomography and fundus autofluorescence I have detected a laser injury at much lower levels compared to injuries used to demonstrate Maximum Permissible Exposure and the Nominal Ocular Hazard distance.
I would ask the authors to provide an alternative explanation of what induced this focal retinal lesion in a healthy fundus of a young gentleman, with an entirely healthy fundus in the fellow left eye?
References
1. Gosling DB, O'Hagan JB, Quhill FM. Blue Laser Induced Retinal Injury in a Commercial Pilot at 1300 ft. Aerosp Med Hum Perform. 2016 Jan;87(1):69-70. doi: 10.3357/AMHP.4411.2016.
Dear Editor,
After reading the article entitled "Ranibizumab 0,5 Treat-and-Extend
regimen for diabetic macular oedema: the RETAIN study" by Prunte et al
(1), there are several considerations that we would like to bring to your
attention.
From the data provided, we noticed how 48.3% of patients in the "pro re
nata" (PRN) regime required <=9 injections over a two-year period. On
the other hand, this condition in "treat...
Dear Editor,
After reading the article entitled "Ranibizumab 0,5 Treat-and-Extend
regimen for diabetic macular oedema: the RETAIN study" by Prunte et al
(1), there are several considerations that we would like to bring to your
attention.
From the data provided, we noticed how 48.3% of patients in the "pro re
nata" (PRN) regime required <=9 injections over a two-year period. On
the other hand, this condition in "treat-and-extend" (T&E) groups only
occurs in 9.92% of the cases (with/without laser, 11.12%/8.74%
respectively).
Referencing another trial for diabetic macular oedema (DMO) with anti-VEGF
therapy, DRCR.net Protocol T (2), 56.36% of the patients received
bilateral treatment. Based on the number of medical visits, total costs
and potential overexposure (there is a growing concern about adverse
events (3)), bilateral treatment brings a correction factor worth to be
considered.
Regarding medical visits, any other monitoring regimen different from
monthly medical visit during the course of two years would clearly alter
this analysis. For instance, the recommendation issued by The Royal
College of Ophthalmology (4): If the patient is stabilized, in year 2
onwards, period between follow up appointments may be increased gradually,
ultimately to a maximum of 12-16 weeks.
The prospect of a better outcome offered by the T&E (vs PRN) in macular
degeneration is where its main strength lies (5). However after reviewing
the DMO results, we believe that the proposed intervention in real
medicine would only make sense after providing enough context to make the
patient fully aware of his options. Otherwise we would be assuming that an
intravitreal injection would be chosen over multiple visits to the
ophthalmologist, which is unlikely.
Clinical caseloads is a major challenge, but should not be addressed by a
strategy that requires the patient to undergo invasive treatments more
often than might be necessary.
References
1. Prunte C, Fajnkuchen F, Mahmood S, et al. Ranibizumab 0.5 mg treat
-and-extend regimen for diabetic macular oedema: the RETAIN study. Br J
Ophthalmol Published Online First: 17 October 2015. doi:
10.1136/bjophthalmol-2015-307249
2. The Diabetes Retinopathy Clinical Research Network. Aflibercept,
bevacizumab, or ranibizumab for diabetic macular edema. N Engl J Med
2015;372:1193-203. doi: 10.1056/NEJMoa1414264
3. Avery RL, Gordon GM. Systemic Safety of Prolonged Monthly Anti-Vascular
Endothelial Growth Factor Therapy for Diabetic Macular Edema: A Systematic
Review and Meta-analysis. JAMA Ophthalmol Published online first; 29
October 2015. doi:10.1001/jamaophthalmol.2015.4070
4. Royal College of Ophthalmologists. Diabetic Retinopathy Guidelines,
2013. https://www.rcophth.ac.uk/wp-content/uploads/2014/12/2013-SCI-301-
FINAL-DR-GUIDELINES-DEC-2012-updated-July-2013.pdf (accesed 24 October
2015)
5. Chin-Yee D, Eck T, Fowler S, et al. A systematic review of as needed
versus treat and extend ranibizumab or bevacizumab treatment regimens for
neovascular age-related macular degeneration. Br J Ophthalmol Published
Online First: 29 October 2015. doi:10.1136/bjophthalmol-2015-306987
We read with interest the report by Espina et al(1) regarding changes
occurring in outer retinal tubulation (ORT) during the course of
intravitreal anti-VEGF treatment.(2) These authors retrospectively
describe ORT changes observed during and after anti-VEGF treatment and
correlated these changes to disease activity or presence of retinal fluid
in 31 patients with neovascular age-related macular degeneration (AMD)
with...
We read with interest the report by Espina et al(1) regarding changes
occurring in outer retinal tubulation (ORT) during the course of
intravitreal anti-VEGF treatment.(2) These authors retrospectively
describe ORT changes observed during and after anti-VEGF treatment and
correlated these changes to disease activity or presence of retinal fluid
in 31 patients with neovascular age-related macular degeneration (AMD)
with a median follow-up time of 11 months.(1) They noted ORT changes in 10
of 33 eyes with ORT detected at baseline and subsequent anti-VEGF
treatment suggesting that some ORT contain vascular elements.(1) We
address the latter issue here.
We recently showed (2, 3) histology and electron microscopy from 77
ORT cross-sections identified in 53 human donor eyes (40 exudative AMD and
13 geographic atrophy), and compared to spectral domain optical coherence
tomography (SD-OCT) scans from 43 eyes with ORT from 34 patients.
Additionally, we published a direct clinicopathologic correlation of ORT
in one patient.(3) ORT is a gliotic formation of Muller cells and
surviving photoreceptors, almost all cones, located in the outer nuclear
layer.(2, 4) Cone photoreceptors degenerate by losing their outer
segments, followed by inner segment retraction, with only the external
limiting membrane formed by Muller cells left at the end-stage.(5) Thus,
ORT undergo a natural evolution independent of anti-VEGF treatment,
because our sample did not contain treated eyes, and we did not observe
any vascular elements within these ORTs.
Others have reached similar conclusions about the ongoing
degeneration of ORT as a natural progression of AMD, not secondary to anti
-VEGF treatment,(6) and despite treatment with optimal visual outcomes,
the prevalence of ORT has increased.(7)
To determine ORT dynamics longitudinally, a metric for measuring ORT
changes, including size, shape, and eccentricity, in multiple closely
spaced SD-OCT scans will be necessary. On the basis of extensive
histology, ORT represents a distinctive process of neurodegeneration,
observable in living patients, with a widely available imaging technology.
References
1. Espina M, et al. (2015) Outer retinal tubulations response to anti-VEGF
treatment. The British journal of ophthalmology.
2. Schaal KB, et al. (2015) Outer retinal tubulation in advanced age-
related macular degeneration: Optical coherence tomographic findings
correspond to histology. Retina 35(7):1339-1350.
3. Litts KM, et al. (2015) Clinicopathological correlation of outer
retinal tubulation in age-related macular degeneration. JAMA ophthalmology
133(5):609-612.
4. Curcio CA, Medeiros NE, & Millican CL (1996) Photoreceptor loss in
age-related macular degeneration. Investigative ophthalmology & visual
science 37(7):1236-1249.
5. Litts KM, Messinger JD, Freund KB, Zhang Y, & Curcio CA (2015)
Inner segment remodeling and mitochondrial translocation in cone
photoreceptors in age-related macular degeneration with outer retinal
tubulation. Investigative ophthalmology & visual science 56(4):2243-
2253.
6. Gildener-Leapman JR, Srivistava S, Ehlers JP, & Kaiser PK (2015)
Prevalence of outer retinal tubulation after anti-VEGF therapy for age-
related macular degeneration. Ophthalmic surgery, lasers & imaging
retina 46(3):345-348.
7. Dirani A, Gianniou C, Marchionno L, Decugis D, & Mantel I (2015)
Incidence of outer retinal tubulation in ranibizumab-treated age-related
macular degeneration. Retina 35(6):1166-1172.
eLetter
Comment on: Population-based assessment of vision-related quality of life
in corneal disease: results from the CORE study
Parul Chawla Gupta, MS; Jagat Ram, MS, FAMS
Department of Ophthalmology
Post Graduate Institute of Medical Education and Research, Chandigarh,
India, 160012
Corresponding author
Dr. Jagat Ram, MS, FAMS
Professor and Head
Department of Ophthalmology
Post Graduate Institute of Medical Education an...
eLetter
Comment on: Population-based assessment of vision-related quality of life
in corneal disease: results from the CORE study
Parul Chawla Gupta, MS; Jagat Ram, MS, FAMS
Department of Ophthalmology
Post Graduate Institute of Medical Education and Research, Chandigarh,
India, 160012
Corresponding author
Dr. Jagat Ram, MS, FAMS
Professor and Head
Department of Ophthalmology
Post Graduate Institute of Medical Education and Research, Chandigarh,
India, 160012
Email id: drjagatram@gmail.com
Conflict of interest and source of funding- None declared
Dear Editor,
We read with interest the recent paper by Vashist and associates [1]
assessing the impact of corneal disease on vision-related quality of life
(VR-QoL) in a rural North Indian population. We herein address important
issues, some of which warrant further discussion. Firstly, as the authors
stated "The Vision Related Quality of Life (VR-QoL) was assessed in 435
cases with corneal disease and 435 controls without any ophthalmic
disease". However, in Table 1, under the subheading of 'marital status';
the total number of controls add upto 436. Secondly, in the present study,
there was no statistically significant difference in VR-QoL scores between
unilateral and bilateral corneal conditions. We strongly believe that
patients with bilateral corneal involvement may have significantly more
effect on the quality of life as compared to the unilateral [2] cases.
Activities of daily living, as well as the ability to drive vehicles would
be affected more in bilateral cases. Thirdly, no mention has been made of
the variance of quality of life with the grade of corneal opacity. Lastly,
an interesting observation in the present study was that in the cases with
corneal disease, married patients had better scores on the IND-VFQ-33
questionnaire as compared to unmarried or widows/widowers in contrast to
the study by Onakoya et al [3] carried out in glaucoma patients, in whom
marital status had no significant effect on QoL scores.
No competing interests
References
1. Vashist P, Gupta N, Tandon R. Population-based assessment of vision-
related quality of life in corneal disease: results from the CORE study.
Br J Ophthalmol 2016;100:588-593.
2. Vu HTV, Keeffe JE, McCarty CA, Taylor HR. Impact of unilateral and
bilateral vision loss on quality of life. Br J Ophthalmol 2005;89:360-363
3. Onakoya AO, Mbadugha CA, Aribaba OT, Ibidapo OO. Quality of life of
primary open angle glaucoma patients in lagos, Nigeria: clinical and
sociodemographic correlates. J Glaucoma. 2012;21(5):287-95.
We read with interest the article titled "Predictive factors for
treatment failure in patients with presumed ocular tuberculosis in an area
of low endemic prevalence" by Agarwal et al published in Br J Ophthalmol
2016;100:348-355.
We wanted to point out few things regarding the article -
The diagnosis of ocular tuberculosis was presumptive in most cases. The
authors have used clinical guide...
We read with interest the article titled "Predictive factors for
treatment failure in patients with presumed ocular tuberculosis in an area
of low endemic prevalence" by Agarwal et al published in Br J Ophthalmol
2016;100:348-355.
We wanted to point out few things regarding the article -
The diagnosis of ocular tuberculosis was presumptive in most cases. The
authors have used clinical guidelines from an article by Gupta et
alignment published in 2007.[1]The same authors have published revised
criterion in 2010.[2]It would have been more appropriate to use the latter
more recent guidelines.
The authors do not provide a break-up of the morphological forms of
posterior uveitis considered as tubercular in the present series. Few
categories of posterior uveitis such as serpiginous choroiditis and
vasculitis may have been included as ocular tuberculosis only on basis of
Quantiferon gold test positivity. All patients with these diagnosis may
not actually be due to active tubercular infection.[3] Rather only a
subset of these patients may be due to active tuberculosis. Thus it is
difficult to analyse treatment failure in cases where the aetiology is not
very certain.
The findings of the authors of higher failure rate of Anti-tubercular
therapy (ATT) in those given higher doses of immunosuppressives could also
indicate that the disease process is not due to active tubercular
infection. The ATT has probably no role in the management of these
disorders and it is actually the immunosuppression that is working. The
failure may be due to inadequate or rapid withdrawal of immunosppression.
Thus it may not be prudent to attribute failure to some property of
tubercular infection when the diagnosis of tuberculosis itself is probable
or questionable.
The authors donot mention if any cases had side-effects of the anti-
tubercular medication or if any patients dropped out.
The authors mention that the decision to start ATT was based on discretion
of physician. Although from the article it appears that the onus of
starting ATT was with the treating ophthalmologist as it was started only
on basis of ocular findings and QFT-G positivity even in the absence of
systemic evidence of tuberculosis.
The authors mention in the end that the evidence base for benefit of oral
steroids in TB-associated uveitis is weak. However we feel that the
contrary, i.e. evidence of benefit of ATT in certain cases of presumed
ocular tuberculosis is weak as in most studies ATT has been given in
combination with steroids and not alone.
References
1: Gupta V,Gupta A,Rao NA.Intraocular tuberculosis--an update.Surv
Ophthalmol 2007;52:561-87.
2: Gupta A, Bansal R, Gupta V, Sharma A, Bambery P. Ocular signs
predictive of tubercular uveitis.Am J Ophthalmol. 2010 Apr;149(4):562-70.
doi: 10.1016/j.ajo.2009.11.020. Epub 2010 Feb 10.
3: Nazari Khanamiri H, Rao NA.Serpiginous choroiditis and infectious
multifocal serpiginoid choroiditis. Surv Ophthalmol. 2013 May-
Jun;58(3):203-32.
The response by Feizi et al is comprehensive and notable. But the
condition could be simply explicated by a clear demonstration of actual
data in a table representing DALK success-failure versus different
trephination diameters. If the authors accept to publish these data, every
reader would be able to deduce the practically applicable end result.
The response by Feizi et al is comprehensive and notable. But the
condition could be simply explicated by a clear demonstration of actual
data in a table representing DALK success-failure versus different
trephination diameters. If the authors accept to publish these data, every
reader would be able to deduce the practically applicable end result.
We enthusiastically read the article entitled: "Factors influencing
big-bubble formation during deep anterior lamellar keratoplasty in
keratoconus" by Feizi et al (1). Authors have included many variables to
find factors influencing success in the big bubble formation and defined
meaningful P value for statistical significance to less than 0.05. From
statistical viewpoint multiple comparisons could increase the false
di...
We enthusiastically read the article entitled: "Factors influencing
big-bubble formation during deep anterior lamellar keratoplasty in
keratoconus" by Feizi et al (1). Authors have included many variables to
find factors influencing success in the big bubble formation and defined
meaningful P value for statistical significance to less than 0.05. From
statistical viewpoint multiple comparisons could increase the false
discovery rate and an increase in type I error. A method of multiple
testing corrections, like Bonferroni correction, or other more complex
statistical adjustment is necessary to decrease the rate of apparently
meaningful findings which may be due to random chance alone (2).
According to our unpublished experience with big bubble deep anterior
lamellar keratoplasty (DALK) in keratoconus, the bubble is difficult to
spread to peripheral cornea in most cases. In larger trephinations of the
recipient cornea, the surgeon needs to create a larger diameter bubble.
Trying to extend the bubble sometimes will end with rupture of Dua's and
Descemet's layers. On the other hand cutting the recipient cornea in a
case of small bubble diameter is difficult and could create holes or
ruptures in peripheral posterior layers with subsequent failure. This
problem might be explained by the anatomy of the pre-Descemet's (Dua's)
layer that allow expansion of type-1 bubbles up to diameter of 8.5
millimeters (3). As many of our successful DALK big bubbles are formed
anterior to Dua's layer, the larger the diameter of trephination could
potentially cause more failure of the procedure. In our experience
trephination of recipient more than 8.25 mm could be associated with
increased failure of the DALK. Revising the statistical analysis of the
study by Feizi et al (1) and adjustment for the level of significance of
multiple comparisons may reveal different results to this valuable
article.
?
References:
1. Feizi S, Javadi MA, Daryabari SH. Factors influencing big-bubble
formation during deep anterior lamellar keratoplasty in keratoconus. The
British journal of ophthalmology. 2015.
2. Streiner DL. Best (but oft-forgotten) practices: the multiple problems
of multiplicity-whether and how to correct for many statistical tests. The
American journal of clinical nutrition. 2015.
3. Dua HS, Faraj LA, Said DG, Gray T, Lowe J. Human corneal anatomy
redefined: a novel pre-Descemet's layer (Dua's layer). Ophthalmology.
2013;120(9):1778-85.
We would like to acknowledge our appreciation for Dr. Peyman for
paying close attention to our article and raising important points. Now,
big-bubble deep anterior lamellar keratoplasty (DALK) is a corneal
transplantation technique of choice for corneal stromal pathologies not
involving endothelium such as keratoconus. The principle shortcoming of
this technique is that it is technically challenging. Any attempts to
incr...
We would like to acknowledge our appreciation for Dr. Peyman for
paying close attention to our article and raising important points. Now,
big-bubble deep anterior lamellar keratoplasty (DALK) is a corneal
transplantation technique of choice for corneal stromal pathologies not
involving endothelium such as keratoconus. The principle shortcoming of
this technique is that it is technically challenging. Any attempts to
increase the success rate of big-bubble formation should be commended as
it is a critical step and difficult for many surgeons. Our article aimed
to investigate the possible influence of patient- and surgery-related
variables on this rate in a homogeneous group of keratoconus patients who
were operated on by a single experienced surgeon.1 The exploratory
analysis revealed that among various factors, recipient sex and
trephination size significantly influenced the rate of achieving a bare
Descemet's membrane (DM).1
Following are points in response to the critiques posed by Dr. Peyman:
1) As mentioned in the Methods section, the influence of the independent
variables on the success rate of big-bubble formation was first
investigated using univariate analysis. Only the variables which had a
significant association at a univariate level were entered into multiple
regression analysis. In our final confirmatory analysis, there was a
limited number of variables including recipient sex, vertical corneal
diameter, corneal thickness, anterior chamber depth, and recipient
trephination size. Therefore, it is very unlikely that multiple
comparisons led to a false positive correlation between the variables.
Additionally, comparisons between the bare DM group and the manual
dissection group using Chi-square and Mann-Whitney tests revealed
significant differences between the two groups in terms of patient sex
distribution and recipient trephination size confirming the results
yielded by multiple regression analyses. This indicates that the
significant associations found in our study were not caused by chance.
2) Providing no evidence, Dr. Peyman anecdotally reports that when the
recipient trephination size is large, it is difficult to complete the
procedure as big-bubble DALK. However, Huang et al.2 used two different
recipient trephination sizes (7.75 mm and 8.25 mm) and reported that big-
bubble DALK was successfully completed in 89.4% of the 7.75-mm group and
in 84.8% of the 8.25-mm group (P=0.60). It is possible that due to some
technical problems Dr. Peyman has with large diameter trephines in DALK,
he has been convinced that the larger diameter of trephination could
potentially cause more failure of the procedure.
3) According to Dr. Peyman's experience, cutting the recipient cornea in a
case of incomplete small bubbles is difficult and could create holes or
ruptures in peripheral posterior layers. However, corneal surgeons who
master different techniques of DALK such as manual dissection technique
and Melle's technique can safely complete dissection using viscoelastic
materials or blunt spatula once the dissection plane is reached.
4) Dr. Peyman refers to a study by Dua et al.3 to explain the reason for
difficult expansion of the big bubble to the border of trephination when a
large trephine is used. In the initial article, Dua et al.3 revealed that
pre-Descemet posterior stromal layer (PDL) ended before the termination of
DM. In the subsequent study, however, they provided evidence that PDL
extends beyond the edge of the big bubble to insert into the trabecular
meshwork.4 Therefore, it is possible to separate posterior stroma from the
PDL far to the corneal periphery. We conducted a study comparing the rate
of achieving a bare DM during big-bubble DALK using central versus
peripheral air injection (the manuscript has been submitted). Using
surgical calipers, we precisely measured the size of achieved bubbles
which ranged from 7.0 to 10.5 mm. These data indicate the big bubble can
successfully be enlarged beyond that Dr. Peyman mentioned.
To summarize, DALK grafts employing a larger diameter recipient bed
provide several advantages including low graft astigmatisms, stable
postoperative refractive outcomes, and better graft biomechanics.2,6 Our
recent study adds a new advantage to the application of a large trephine
size in keratoconic eyes which increases the likelihood of successful big
bubble formation during Anwar's DALK technique.1
References
1- Feizi S, Javadi MA, Daryabari SH. Factors influencing big-bubble
formation during deep anterior lamellar keratoplasty in keratoconus. Br J
Ophthalmol. 2015; In press.
2- Huang T, Hu Y, Gui M, et al. Large-diameter deep anterior lamellar
keratoplasty for keratoconus: visual and refractive outcomes. Br J
Ophthalmol. 2015; 99:1196-1200.
3- Dua HS, Faraj LA, Said DG, et al. Human corneal anatomy redefined: a
novel pre-Descemet's layer (Dua's layer). Ophthalmology. 2013;120:1778-
1785.
4- Dua HS, Faraj LA, Branch MJ, et al. The collagen matrix of the human
trabecular meshwork is an extension of the novel pre-Descemet's layer
(Dua's layer). Br J Ophthalmol. 2014;98:691-697.
5- Feizi S, Einollahi B, Yazdani S, et al. Graft biomechanical properties
after penetrating keratoplasty in keratoconus. Cornea. 2012;31:855-858.
Sepehr Feizi, MD, MSc
Assistant Professor of Ophthalmology, Shahid Beheshti University of
Medical Sciences, Tehran, Iran.
Email: sepehrfeizi@yahoo.com
Conflict of Interest:
None declared
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The response by Feizi et al is comprehensive and notable. But the condition could be simply explicated by a clear demonstration of actual data in a table representing DALK success-failure versus different trephination diameters. If the authors accept to publish these data, every reader would be able to deduce the practically applicable end result.
Conflict of Interest:
None dec...
We enthusiastically read the article entitled: "Factors influencing big-bubble formation during deep anterior lamellar keratoplasty in keratoconus" by Feizi et al (1). Authors have included many variables to find factors influencing success in the big bubble formation and defined meaningful P value for statistical significance to less than 0.05. From statistical viewpoint multiple comparisons could increase the false di...
We would like to acknowledge our appreciation for Dr. Peyman for paying close attention to our article and raising important points. Now, big-bubble deep anterior lamellar keratoplasty (DALK) is a corneal transplantation technique of choice for corneal stromal pathologies not involving endothelium such as keratoconus. The principle shortcoming of this technique is that it is technically challenging. Any attempts to incr...
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