Dear Editor,
We would like to congratulate Issa et al. [1] on their excellent and,
we believe, important paper regarding cataract surgery and intraocular
pressure drop.
It has become increasingly obvious to us, in our practice, that many
patients do indeed get a significant drop in IOP after
phacoemulsification. We now have a substantial number of patients with
both acute and chronic angle closure who, following cataract surgery, have
been able to come off all antihypertensive medications. We would now goes
as far as to say that in these patients it is now the operation of choice
(when medical therapy has deemed to have failed) and this is supported by
a number of studies [2-5]. There is also the added benefit of a
reduction in the incidence of aqueous misdirection.
It is interesting that Issa et al used 'normal' patients in their
study and still found a significant reduction in IOP. We have felt for
sometime that a number of glaucoma patients who on gonioscopy are seen to
have 'open-angles' but do on closer inspection have some (usually central)
anterior chamber shallowing, often seem to have profound drops in their
IOP following cataract surgery. Although many of these patients have
degrees of hypermetropia, this is not always the case. Indeed with
increasing nuclear sclerosis some may be myopic at presentation.
The authors rightly state that their study needs to be repeated by
others to confirm their results. We personally would feel that lens
thickness plays more of a role than this study suggests. There is an
important flaw - acknowledged by the authors - regarding the lack of data
on corneal thickness. Any future studies need to correct for this -not
only to allow a more accurate assessment of the IOP -but because the
cornea itself is part of the anterior structure of the eye and may not
necessarily be an independent variable.
Finally we speculate that there is likely to be a measurable
relationship between IOP, volume of the anterior segment, lens size and
possibly corneal thickness. Once we have quantified this it may then allow
us not only to be able to assess the likely magnitude of IOP drop after
phacoemulsification, but will give an essential insight into some of the
underlying mechanisms of raised IOP.
References
[1] S A Issa, J Pacheco, U Mahmood, J Nolan, and S Beatty. A novel
index for predicting intraocular pressure reduction following cataract
surgery. Br J Ophthalmol 2005; 89: 543-546
[2] Gunning FP, Greve EL. Lens extraction for uncontrolled angle-
closure glaucoma: long-term follow-up. J Cataract Refract Surg.
1998;24(10): 1347-56.
[3] Acton J, Salmon JF, Scholtz R. Extracapsular cataract extraction
with posterior chamber lens implantation in primary angle-closure
glaucoma. J Cataract Refract Surg 1997;23(6):930-4
[4] Jacobi PC, Dietlein TS, Luke C, Engels B, Krieglstein GK.
Primary phacoemulsification and intraocular lens implantation for acute
angle-closure glaucoma. Ophthalmology. 2002 Sep;109(9):1597-603
[5] Teekhasaenee C, Ritch R Combined phacoemulsification and
goniosynechialysis for uncontrolled chronic angle-closure glaucoma after
acute angle-closure glaucoma. Ophthalmology. 1999 Apr;106(4):669-74;
Dear Editor,
We would like to congratulate Issa et al. [1] on their excellent and, we believe, important paper regarding cataract surgery and intraocular pressure drop.
It has become increasingly obvious to us, in our practice, that many patients do indeed get a significant drop in IOP after phacoemulsification. We now have a substantial number of patients with both acute and chronic angle closure who, following cataract surgery, have been able to come off all antihypertensive medications. We would now goes as far as to say that in these patients it is now the operation of choice (when medical therapy has deemed to have failed) and this is supported by a number of studies [2-5]. There is also the added benefit of a reduction in the incidence of aqueous misdirection.
It is interesting that Issa et al used 'normal' patients in their study and still found a significant reduction in IOP. We have felt for sometime that a number of glaucoma patients who on gonioscopy are seen to have 'open-angles' but do on closer inspection have some (usually central) anterior chamber shallowing, often seem to have profound drops in their IOP following cataract surgery. Although many of these patients have degrees of hypermetropia, this is not always the case. Indeed with increasing nuclear sclerosis some may be myopic at presentation.
The authors rightly state that their study needs to be repeated by others to confirm their results. We personally would feel that lens thickness plays more of a role than this study suggests. There is an important flaw - acknowledged by the authors - regarding the lack of data on corneal thickness. Any future studies need to correct for this -not only to allow a more accurate assessment of the IOP -but because the cornea itself is part of the anterior structure of the eye and may not necessarily be an independent variable.
Finally we speculate that there is likely to be a measurable relationship between IOP, volume of the anterior segment, lens size and possibly corneal thickness. Once we have quantified this it may then allow us not only to be able to assess the likely magnitude of IOP drop after phacoemulsification, but will give an essential insight into some of the underlying mechanisms of raised IOP.
References
[1] S A Issa, J Pacheco, U Mahmood, J Nolan, and S Beatty. A novel index for predicting intraocular pressure reduction following cataract surgery. Br J Ophthalmol 2005; 89: 543-546
[2] Gunning FP, Greve EL. Lens extraction for uncontrolled angle- closure glaucoma: long-term follow-up. J Cataract Refract Surg. 1998;24(10): 1347-56.
[3] Acton J, Salmon JF, Scholtz R. Extracapsular cataract extraction with posterior chamber lens implantation in primary angle-closure glaucoma. J Cataract Refract Surg 1997;23(6):930-4
[4] Jacobi PC, Dietlein TS, Luke C, Engels B, Krieglstein GK. Primary phacoemulsification and intraocular lens implantation for acute angle-closure glaucoma. Ophthalmology. 2002 Sep;109(9):1597-603
[5] Teekhasaenee C, Ritch R Combined phacoemulsification and goniosynechialysis for uncontrolled chronic angle-closure glaucoma after acute angle-closure glaucoma. Ophthalmology. 1999 Apr;106(4):669-74;