In the article presented by Wickham and associates,[1] the authors
compared vitrectomy and gas for treating inferior break retinal
detachments with vitrectomy, gas and scleral buckle. The study showed no
significant difference in the final outcome between the two groups. While
vitrectomy and gas for inferior break retinal detachments appears
promising, there are several issues that we would like to ra...
In the article presented by Wickham and associates,[1] the authors
compared vitrectomy and gas for treating inferior break retinal
detachments with vitrectomy, gas and scleral buckle. The study showed no
significant difference in the final outcome between the two groups. While
vitrectomy and gas for inferior break retinal detachments appears
promising, there are several issues that we would like to raise.
First, the surgery was performed by either a registrar, fellow or
consultant. These surgeons may have varying degrees of experience and the
inconsistency may affect the rate of successful surgical outcome. Second,
additional tears were treated with cryotherapy or laser. As shown by
Bonnet M et al,[2] the post-operative proliferative vitreoretinopathy (PVR)
rate could be as high as 25.8% in patients treated with cryotherapy as
compared to 2.2% in the laser group. It is unclear what the relative
distribution of patients who underwent cryotherapy in the two groups was
and this may have been a confounding factor in the study. Third, patients
underwent an air/gas exchange with either SF6 or C3F8. As C3F8 had a much
longer duration of tamponade than SF6, the use of one agent over another
may have lead to a difference in the success rate.
The study excluded patients with PVR grade C. However, for those with
grade A or B, a scleral buckle was planned before the operation. This
could lead to a selection bias where potentially more difficult cases were
scheduled into the scleral buckle group. This may be a contributing factor
for a higher rate of post-operative PVR (20%) and epiretinal membrane
formation in this group, compared to a rate of 5-10% reported previously.[3
-4] The underlying vitreo-retinal pathology rather than the placement of
the scleral buckle may have been a major reason behind the high PVR rate
noted in this group.
The authors stated that the main reasons for performing vitrectomy
and gas without scleral buckle was to avoid the possible complications of
scleral buckle, namely, longer operating time,[5] exposure, refractive
change, diplopia and anterior segment ischaemia.[6-10] Perhaps, in the
interest of readers, the authors can provide us with the information if
any of these complications developed during the study.
The high rate of final reattachment reported in the study is
encouraging. We believe that vitrectomy and gas alone is an effective
method to treat selected cases of retinal detachments with inferior
retinal breaks. A controlled, randomized, prospective study, comparing the
outcome in properly matched groups and with meticulous attention to
surgical methods [11] will help address some of the above issues and help
elucidate further if the procedure without the use of scleral buckle will
benefit patients with inferior break retinal detachment.
We would like to commend the authors for conducting this very nice
study on an important topic that may provide a better alternative
treatment. We wish that the issues that we raise will help broaden the
discussion on the topic.
Yolanda Y.Y. Kwong, MRCS
C.W. Tsang, MRCS
Wico W. Lai, MD, FACS
Dennis S.C. Lam, FRCS, FRCOphth
Hong Kong, People¡¦s Republic of China
The Corresponding Author has the right to grant on behalf of all
authors and does grant on behalf of all authors, an exclusive licence (or
non exclusive for government employees) on a worldwide basis to the BMJ
Publishing Group Ltd and its licensees, to permit this article (if
accepted) to be published in BJO and any other BMJPG products and to
exploit all subsidiary rights, as set out in our licence
(http://bjo.bmjjournals.com/misc/ifora/licenceform.shtml)
References
(1) Wickham L, Connor M, Aylward GW. Vitrectomy and gas for inferior
break retinal detachments: are the results comparable to vitrectomy, gas,
and scleral buckle? Br J Ophthalmol 2004;88:1376-1379.
(2) Bonnet M, Guenoun S. Surgical risk factors for severe postoperative
proliferative vitreoretinopathy in retinal detachment with grade B PVR.
Graefes Arch Clin Exp Ophthalmol 1995;233(12):789-91
(3) Charteris DG, Sethi CS, Lewis GP, Fisher SK. Proliferative
vitreoretinopathy ¡V developments in adjunctive treatment and retinal
pathology. Eye 2002;16:369-374.
(4) The Retina Society Terminology Committee. The classification of
retinal detachment with proliferative vitreoretinopathy. Ophthalmol
1983;90:121-125.
(6) Findall RJ, Norton EW, Curtin, et al. Reduction of extrusion and
infection following episcleral silicone implants and cryopexy in retinal
detachment surgery. Am J Ophthalmol 1971;71:835-7.
(7) Hayashi H, Hayashi K, Nakao F, et al. Corneal shape changes after
scleral buckling surgery. Ophthalmology 1997;104:831-7.
(8) Domniz Y, Cahana M, Avni I. Corneal surface changes after pars
plana vitrectomy and scleral buckling surgery. J Cataract Refract Surg
2001;27:868-72.
I would like to congratulate Theelen et al for their recent
article on impact factors on intraocular pressure measurements in healthy
subjects [1], and I would like to add a thought. As Theelen and colleagues
point out with reference to the literature [2,3], increased pressure in
the jugular vein leads to increased brain pressure, and by an increase in
the episcleral venous pressure, to an elev...
I would like to congratulate Theelen et al for their recent
article on impact factors on intraocular pressure measurements in healthy
subjects [1], and I would like to add a thought. As Theelen and colleagues
point out with reference to the literature [2,3], increased pressure in
the jugular vein leads to increased brain pressure, and by an increase in
the episcleral venous pressure, to an elevation of intraocular pressure.
Correspondingly, in a previous study by Teng and associates, it was
discussed that a tight necktie may increase intraocular pressure by an
increased jugular vein pressure and could affect the diagnosis and
management of glaucoma [4]. It may be taken into account, however, that
the brain pressure and pressure in the cerebrospinal fluid space
surrounding the retrobulbar part of the optic nerve are the counter-
pressure against the intraocular pressure across the lamina cribrosa [5].
If the cerebrospinal fluid space pressure is elevated (due to increased
jugular vein pressure), the intraocular pressure may also be allowed to be
elevated so that the trans-lamina cribrosa pressure difference may remain
constant. Independently of the question, whether a thight neck-tie may or
may not increase intraocular pressure, one may assume that if the
intraocular pressure gets higher due to an increased jugular vein
pressure, it may, at least partially, be balanced by an increase in brain
pressure, without increasing the risk for glaucoma.
References
(1) Theelen T, Meulendijks CFM, Geurts DEM, van Leeuwen A, Voet NBM,
Deutman AF. Impact factors on intraocular pressure measurements in healthy
subjects. Brit J Ophthalmology 2004; 88:1510-1.
(2) Mavrocordatos P , Bissonnette B, Ravussin P. Effects of neck position
and head elevation on intracranial pressure in anaesthetized neurosurgical
patients—preliminary results. J Neurosurg Anesthesiol 2000; 12: 10–4.
(3) Toole JF. Effects of change of head limb and body position on cephalic
circulation. N Engl J Med 1968; 279: 307–11.
(4) Teng C, Gurses-Ozden R, Liebmann JM, Tello C, Ritch R. Effect of a
tight necktie on intraocular pressure. Brit J Ophthalmology 2003; 87:946-
94
(5) Jonas JB, Berenshtein E, Holbach L. Lamina cribrosa thickness and
spatial relationships between intraocular space and cerebrospinal fluid
space in highly myopic eyes. Invest Ophthalmol Vis Sci 2004; 45: 2660-5.
Dear Editor,
We were highly interested by Sharma et al's paper on inferior-tear
retinal
detachment (RD) and we would like to make a few remarks.
Is there any significant difference between phakic and pseudophakic
patients ? When comparing the two techniques, it is worth reminding that
vitrectomy will systematically induce cataract within a few years, which
will imply secondary surgery. This will considerably increa...
Dear Editor,
We were highly interested by Sharma et al's paper on inferior-tear
retinal
detachment (RD) and we would like to make a few remarks.
Is there any significant difference between phakic and pseudophakic
patients ? When comparing the two techniques, it is worth reminding that
vitrectomy will systematically induce cataract within a few years, which
will imply secondary surgery. This will considerably increase management
costs.
We do not fully agree with the definition proposed for this particular
RD
group. According to Sharma et al, inferior-tear RD is characterised by
at
least one tear being localised between the 4- and 8-hour meridians.
Figure
2 is a good illustration of that, where all three sketches show tears
beyond the 3h-9h meridians. It is our view that inferior-tear RD can
only
be evoked when all tears are between 4 and 8-h meridians. Otherwise, it
is
not inferior-tear RD but rather superior-tear RD complicated by an
inferior tear. Consistently with this definition, inferior-tear RDs
appear
to induce a high risk of recurrence. Indeed, we found a significantly
increased risk of recurrence in such specific RD cases2.
We agree with Sharma et al when they underline the importance of
postoperative positioning following inferior-tear RD surgery. Several
processes have been used. We setup a prospective study in patients
operated on for inferior-tear RD by indentation, subretinal fluid
drainage
and gas injection. We systematically positioned a wire under the right
inferior so as to leave the eye under traction for a few days (photos).
Bed foot legs were also propped up to give the patient a feet-up
posture.
Our first results in 10 patients revealed 100% anatomical success with
subretinal fluid persistence for 3 months in one patient and we had to
reinject gas in another.
Management of inferior tear RD is specific and requires more studies
like
that of Sharma et al, to try and establish a consensus.
References
1. Sharma A, Grigoropoulos V, Wiliamson TH. Management of primary
rhegmatogenous retinal detachment with inferior breaks. Br J Ophthalmol
2004;88:1376-1379
2. Quintyn JC, Ponchel C, Fillaux J et al. A. Retinal detachment by
inferior tear, bad pronostic ? J Fr Ophtalmol to be published
Competing Interest Statement No authors have any competing financial interests.
We read with interest for the article by Raiskup et al. on the long
term evaluation on mitomycin C (MMC) for pterygium.[1] It seems that the
usage MMC in pterygium surgery is relatively safe in the long term.
Overdosge of MMC eyedrops may be associated with potential serous
side effects such as corneal perforation.[2] In this regards, we would like
to point out a major typo in the Abstr...
We read with interest for the article by Raiskup et al. on the long
term evaluation on mitomycin C (MMC) for pterygium.[1] It seems that the
usage MMC in pterygium surgery is relatively safe in the long term.
Overdosge of MMC eyedrops may be associated with potential serous
side effects such as corneal perforation.[2] In this regards, we would like
to point out a major typo in the Abstract. The dosage of the MMC
eyedrops should be 0.01% or 0.02% instead of 1% or 2%. Besides, we would
be appreciative if the authors could clarify the duration of MMC eyedrops
that was given postoperatively, whether it is a 2-week course as described
in the Abstract or a 5-day course as described in the Patients and
Methods.
Since a single intraoperative application of MMC and post operative
MMC eyedrops are equally effective, it seems that the former is the
treatment of choice as it is easier to administer and there is no
compliance issue.
Finally, the authors also suggested that at present, they advise the
use of MMC at a concentration of 0.02% intraoperatively for 3 minutes.
This, however, according to our experience, is associated with a higher
recurrence rate as compared with 0.02 % for 5 minutes (42.9% vs 8.3%).[2]
References
1. Raiskup F, Solomon A, Landau D, Ilsar M, Frucht-Pery J. Mitomycin
C for pterygium: long term evaluation. Br J Ophthalmol. 2004;88:1425-8.
2. Lam DS, Wong AK, Fan DS, Chew S, Kwok PS, Tso MO. Intraoperative
mitomycin C to prevent recurrence of pterygium after excision: a 30-month
follow-up study. Ophthalmology. 1998;105:901-4
We read with interest the article by Muhtaseb et al. on the
development of a system for preoperative stratification of cataract
patients according to their risk of intraoperative complications. [1] In their article the authors have analyzed
1441 cataract surgeries in order to determine factors that would
increase
the risk of surgical complications.
We read with interest the article by Muhtaseb et al. on the
development of a system for preoperative stratification of cataract
patients according to their risk of intraoperative complications. [1] In their article the authors have analyzed
1441 cataract surgeries in order to determine factors that would
increase
the risk of surgical complications.
We have previously described a similar simple grading system for
assessing the risk of cataract surgery which we called "the cataract
surgery risk score" and found it to be useful for residents and
beginning
surgeons.[2] Our risk score is composed of individual points attributed to
risk factors that are believed to increase complications during surgery.
The advantage of such a system is that it allows the selection of cases
from easy to more difficult ones, as the surgeon's skills improve. It
also allows the beginning surgeons to focus on important details in the
ocular examination that are often overlooked.
References
1. M Muhtaseb, A Kalhoro, and A Ionides. A system for preoperative stratification of cataract patients according to risk of intraoperative complications: a prospective analysis of 1441 cases. Br J Ophthalmol 2004; 88: 1242-1246.
2. Najjar DM, Awwad ST. Cataract surgery risk score for residents
and beginning surgeons. J Cataract Refract Surg. 2003 Oct;29(10):2036-7.
We read with interest the article by Gouws et al.[1] on the apparent
increased incidence of cystoid macular oedema (CMO) in
phacoemulsification
patients when trypan blue was used to stain the anterior capsule.
Trypan blue was commonly used in both anterior and posterior
segment
surgeries.[2-4] If trypan blue does cause macular toxicity, its risks
should
theoretically be higher when used...
We read with interest the article by Gouws et al.[1] on the apparent
increased incidence of cystoid macular oedema (CMO) in
phacoemulsification
patients when trypan blue was used to stain the anterior capsule.
Trypan blue was commonly used in both anterior and posterior
segment
surgeries.[2-4] If trypan blue does cause macular toxicity, its risks
should
theoretically be higher when used in posterior segment surgeries.
However,
studies on the use of trypan blue, both in the anterior[2,3] and
posterior[4,5] segments, did not show apparent toxicity.
Thus, it would be appreciated if the authors could clarify whether
other potential confounders were assessed in their study, including:
1. Other causes of CMO such as diabetes, uveitis and prostaglandin
use;
2. Operating time since photo-toxicity from the operative
microscope[6] per
se is a risk factor for CMO development. It appears that only operations
for patients in group B were performed by one surgeon, if operations for
patients in group A (with trypan blue use) were done by trainees, the
operative time is expected to be longer;
3. Whether all patients received a fundus examination with dilated
pupil
after the operation. If these were only performed in patients with sub-
optimal visual acuities, the incidence of CMO may be underestimated.
Finally, we concur with the authors' view that we should try all
means in terms of minimising any theoretical toxicities of trypan blue.
It
is our routine to actively remove trypan blue with the bimanual
irrigation
aspiration system as soon as the anterior capsule has been stained. It
is
very effective and the potential toxicities might be reduced.
References
1. Gouws P, Merriman M, Goethals S, Simcock PR, Greenwood RJ,
Wright
G. Cystoid macular oedema with trypan blue use. Br J Ophthalmol. 2004
Oct;88(10):1348-9.
2. Melles GR, de Waard PW, Pameyer JH, Houdijn Beekhuis W. Trypan
blue capsule staining to visualize the capsulorhexis in cataract
surgery.
J Cataract Refract Surg. 1999 Jan;25(1):7-9.
3. Dada VK, Sharma N, Sudan R, Sethi H, Dada T, Pangtey MS.Anterior
capsule staining for capsulorhexis in cases of white cataract:
comparative
clinical study. J Cataract Refract Surg. 2004 Feb;30(2):326-33.
4. Feron EJ, Veckeneer M, Parys-Van Ginderdeuren R, Van Lommel A,
Melles GR, Stalmans P. Trypan blue staining of epiretinal membranes in
proliferative vitreoretinopathy. Arch Ophthalmol. 2002 Feb;120(2):141-4.
5. Li K, Wong D, Hiscott P, Stanga P, Groenewald C, McGalliard J.
Trypan blue staining of internal limiting membrane and epiretinal
membrane
during vitrectomy: visual results and histopathological findings. Br J
Ophthalmol. 2003 Feb;87(2):216-9.
6. Donzis PB, DeBartolo DF, Lewen RM, May DR. Light-induced
maculopathy and cystoid macular edema. J Cataract Refract Surg. 1988
Jan;14(1):84-5.
We read with interest the report by Henderson et al.[1] The title of the paper includes the word "early" and the
median time to leak is 3.5 days, but the range of time taken for bleb
leakage to develop extends to 408 days postoperatively. We do not think
this is early nor a postoperative complication.
Wound leakage complicates the management of trabeculectomy: some eyes
develop anter...
We read with interest the report by Henderson et al.[1] The title of the paper includes the word "early" and the
median time to leak is 3.5 days, but the range of time taken for bleb
leakage to develop extends to 408 days postoperatively. We do not think
this is early nor a postoperative complication.
Wound leakage complicates the management of trabeculectomy: some eyes
develop anterior chamber shallowing, choroidal detachment and even
hypotony, causing the clinician to intervene by a variety of methods.
Whilst leakage is occurring subconjunctival fibrosis may proceed
unchecked, but standard interventions, such as needling with injection of
5-fluorouracil, may be contraindicated in the presence of a wound leak.
It would be helpful for the reader to know whether any interventions were
needed or were delayed, since not only may these affect the long term
outcome but also will help to guide the surgeon managing a wound leak.
1. H W A Henderson, E Ezra, and I E Murdoch
Early postoperative trabeculectomy leakage: incidence, time course, severity, and impact on surgical outcome
Br J Ophthalmol 2004; 88: 626-629.
We read with interest the comments of Professor Bajaj and colleagues
and wish to respond to the points raised as follows.
Firstly, we are in complete agreement that the horizontal laxity of
the eyelid should be evaluated pre-operatively and indeed this was done.
This led to the necessity for 9 of the patients (28%) to undergo primary
adjunctive procedures as stated in the article. Indeed 1...
We read with interest the comments of Professor Bajaj and colleagues
and wish to respond to the points raised as follows.
Firstly, we are in complete agreement that the horizontal laxity of
the eyelid should be evaluated pre-operatively and indeed this was done.
This led to the necessity for 9 of the patients (28%) to undergo primary
adjunctive procedures as stated in the article. Indeed 12 adjunctive
procedures were performed on 10 eyelids of these 9 patients, emphasising
the importance of this aspect.
Concerning the fixation of the implant and the risk of posterior
migration, none of the authors has any experience of using Prolene or
another non-absorbable suture in this context; we therefore cannot comment
on whether this reduces the tendency to upward or forward migration of the
superior aspect of the plate and are unaware of any data on this. We would
however make the observation the posterior slippage allowed by incising
the orbital septum is a desirable effect to improve lid motility on
downgaze, and not an effect that we would wish to reduce. However, we
suspect that this effect is not dependent on the type of fixation between
the tarsus and the superior aspect of the Medpor plate.
Regarding the subset of patients with previous hard palate or donor
sclera, it was not our experience that these eyelids were more likely to
have a poor outcome, however as only 2 eyelids fell into this subset, then
we do not have the data to comment further on this point.
In his second eLetter (1), Dua continues his criticism of our
proposed modification of the classification of ocular surface burns(2)
but
once again fails to understand our motivation, which is to simplify the
grading of such injuries in the light of recent advances in the
management
of ocular surface disease (3-6). The result is a modification of a well
established classification, which is easily reme...
In his second eLetter (1), Dua continues his criticism of our
proposed modification of the classification of ocular surface burns(2)
but
once again fails to understand our motivation, which is to simplify the
grading of such injuries in the light of recent advances in the
management
of ocular surface disease (3-6). The result is a modification of a well
established classification, which is easily remembered and can be used
by
all ophthalmologists and not just by corneal specialists. The Dua, King
and Joseph classification (7) allows quantification of the injury, which
is useful in a research environment but is trapped in its detail for
routine clinical use.
We would reiterate that our modifications are based on
recent advances in the management of ocular surface injuries, which have
meant that even severe injuries can have good outcomes (3-6). This is
the
rationale for having Grade III as the most severe injury grade and for
uniformly assigning to it a guarded prognosis. Within that grade,
different injury patterns will have different management protocols and
different rates of recovery. The work by Roper Hall (8) elegantly showed
that a good and doubtful prognosis correlated respectively to less or
more
than one third of conjunctival ischaemia at the limbus. Hence we
retained
this element of his classification to separate Grade II and Grade III in
our modification. It serves to identify a serious ocular surface injury
to
the non-corneal specialist who can then arrange an appropriate referral.
Dua's confusion about the role of 'OR' in our table in order to define
the
Grade of injury is actually dealt with in the text of the original
article
(2): the Grade of the injury is assigned simply on the basis of the most
severe sign, rather than on the complex analysis of a combination of
signs.
Dua is supportive of our inclusion of conjunctival injury in our
proposed modification (1) but disagrees with the inclusion of tarsal
conjunctival assessment, on the basis that it does not influence
prognosis. This is clearly wrong. Contiguous tarsal and bulbar injury
can
lead to symblepharon formation and shortening of the conjunctival
fornices, which is detrimental to the ocular surface and therefore
deserves inclusion in any assessment of ocular surface injury. The
bulbar
and tarsal conjunctiva extends into the fornices and forniceal
conjunctival involvement is therefore included in the measured area of
involvement - important for possible stem cell sites (9).
We would leave it to readers of the Journal and those involved in
this field to judge the value of the different grading systems.
References
1. Dua HS. Classification of ocular surface burns. Br J Ophthalmol
eLetter ( 11 August 2004)
2. Harun S, Srinivasan S, Hollingworth K, Batterbury M, Kaye SB.
Modification of the classification of ocular chemical injuries. Br J
Ophthalmol 2003;88:1353-1354
3. Kobayashi A, Shirao Y, Yoshita T, et al.Temporory amniotic
membrane patching for acute chemical burns. Eye 2003; 17: 149-158
4. Stoiber J, Muss WH, Pohla-Gubo G, Ruckhofer J, Grabner G.
Histopathology of human corneas after amniotic membrane and limbal stem
cell transplantation for severe chemical burn. Cornea
2002;21(5):482-489.
5.Nishiwaki-Dantas MC, Dantas PE, Reggi JR. Ipsilateral limbal
translocation for treatment of partial limbal deficiency secondary to
ocular alkali burn. Br J Ophthalmol 2001;85(9):1031-1033
6.Ozdemir O, Tekeli O, Ornek K, Arslanpence A, Yalcindag NF. Limbal
autograft and allograft transplantations in patients with corneal burns.
Eye 2004;18(3):241-248
7.Dua HS, King AJ, Joseph A. A new classification of ocular surface
burns. Br J Ophthalmol 2001;85:1379-1383
8.Roper-Hall MJ. Themal and chemical burns.Trans Ophthalmol Soc UK
1965;85:631-53
9.Wei Z-G, Cotsarelis G, Sun T-T, Lavker RM. Label-retaining cells
are preferentially located in the forniceal epithelium:implications on
conjunctival epithelial haemostasis. Invest Ophthal Vis Sci
1995;36:236-46
We read with interest the paper by Tan et al. [1] on Charles Bonnet
Syndrome (CBS) in Asian patients. Their finding of a lower CBS prevalence
than European or North American surveys demands further investigation,
although this may reflect the stringent criteria of hallucination
complexity they used in making the diagnosis (thus excluding the commonest
CBS hallucinations of coloured blobs and gri...
We read with interest the paper by Tan et al. [1] on Charles Bonnet
Syndrome (CBS) in Asian patients. Their finding of a lower CBS prevalence
than European or North American surveys demands further investigation,
although this may reflect the stringent criteria of hallucination
complexity they used in making the diagnosis (thus excluding the commonest
CBS hallucinations of coloured blobs and grid-like ‘tesselloptic’
patterns [2,3]) and, as pointed out in the accompanying editorial comment,
the relatively low prevalence of macular disease in their cohort.
However, it is not this aspect of the report we found most intriguing - it
was the observation that CBS occurred with good acuity. In fact, 3 of the
4 CBS patients described had a degree of impairment which placed them at
risk for CBS (best eye acuity 0.3 or worse [4]). It is the remaining
patient (patient three, a 72 year old male) who is of particular
importance as his relative preservation of acuity bilaterally (20/30 RE,
20/40 LE) challenges the view that significant acuity loss is a
prerequisite for ‘ophthalmological’ visual hallucinations. This case
mirrors 4 patients we have recently studied with Charles Bonnet Syndrome
secondary to glaucoma and bilaterally good acuity. We describe the cases
below and offer a pathophysiological mechanism for the association.
In one sense, the finding that CBS occurs with preserved acuity is
hardly novel. As cited by Tan et al.[1], several previous reports have
found such an association. However, all is not as it seems, the term
Charles Bonnet Syndrome (CBS) being used in different ways by different
authors. Some use the term to describe visual hallucinations with insight,
irrespective of the presence of eye disease, age or clinical context [5,6].
Others use the term to describe the association of visual hallucinations
with age and intact cognition, without reference to eye disease or
hallucination phenomenology [7,8]. Under these definitions it is hardly
surprising that a patient with ‘CBS’ has preserved acuity, the patients in
these studies having a diverse range of conditions from delirium to
Parkinson’s disease and beyond. In contrast, ophthalmologists and
neurologists have used CBS to emphasise eye or visual pathway disease,
with the phenomenology of the hallucinations and age being of secondary
importance [9,10]. Although each definition of CBS has its merits, the ophthalmological definition reminds us best of Bonnet’s original
description and helps characterise a distinctive subgroup of visually
hallucinating patients with predicable prognosis and specific
pathophysiology [2,11]. However, even CBS as defined ophthalmologically
carries with it an inherent ambiguity: is it eye disease itself or the
loss of acuity that is the important factor? The consistent finding of
acuity loss as a risk factor [4,12,13] suggests the latter, or at least
that the central retina plays a key role in the underlying pathophysiological mechanism.
As part of a larger study into the visual phenomenology of CBS, we
have recruited 4 patients with advanced glaucoma (3 POAG and 1 chronic
narrow angle) but preserved visual acuity. The age range of the patients
was 81 to 91, 3 men and 1 woman. Their visual acuities ranged from 6/6 to
6/12 monocularly with all patients having 6/9 or better in their better
eye. All had extensive field defects bilaterally and cup to disc ratios of
0.8 or greater in both eyes. 2 patients had bilateral trabeculectomies now
off treatment, one was on g.bimatoprost and g.trusopt to both eyes and one
on g.timolol 0.25% to both eyes. 2 patients were bilaterally pseudophakic.
The patient with chronic narrow angle glaucoma had previous surgical
iridectomies. The duration of their hallucinations ranged from 6 months to
6 years. 3 patients hallucinated in colour and one in black and white. The
most common hallucination was of tessellopsia [2] experienced by all the
patients, with 2 patients seeing, in addition, formed buildings and 2
patients, letter-like shapes. There were also single reports of
hallucinations of groups of people, animals, branching shapes
(dendropsia [2]) and one patient described visual allesthesia [14]. In three
of the patients the hallucinations encompassed the entire visual field, in
the fourth they were restricted to the visual field defect. None had
hallucinations in other sensory modalities and all had insight into the
nature of the experiences. The phenomenology of the hallucinations and the
relative frequency of the different hallucination categories are
consistent with previous descriptions of ophthalmologically-defined
CBS [2,3]. Non-ophthalmological causes of visual hallucinations [2,3] were
excluded. As far as we are aware this is the largest case series of
patients with visual hallucinations secondary to eye disease and
bilaterally preserved visual acuity yet to be reported.
Current aetiological theories of CBS emphasise the importance of
deafferentation [15] (both ‘physiological’ through ganglion cell loss and
‘functional’, e.g. related to blindfolding or cataract), the loss of
visual input resulting in a change in cortical excitability [2]. Although
it has been assumed that deafferentation of sufficient severity to
precipitate CBS implies a consequent loss of acuity, our cases and that of
Tan et al.[1] suggest otherwise. Patients with advanced glaucoma can have
a significant degree of ganglion cell loss and consequent physiological deafferentation without a loss of acuity, placing them at risk for CBS.
This contrasts with age related macular disease where the loss of central
retinal ganglion cells leads, indirectly, to an association of CBS with
acuity loss. We conclude that reduced acuity is not a necessary
prerequisite for ophthalmologically-defined CBS and that ophthalmologists
should be aware that patients with preserved acuity but significant
deafferenting ocular disease are at risk of the syndrome.
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