Causes of Pupillary Block
Pupillary block is a type of angle closure glaucoma. As we know that the iris lies infront of the lens and usually there is no physical contact between the back surface of the iris and the anterior surface of the natural lens.
The aqueous humor will flow from the posterior chamber of the eye through this space between the iris and the lens to the anterior chamber.
For many reasons such as small axial length of the eye and large lens mass, there will be direct contact between the iris and the lens and the space between them will be obliterated leading to high aqueous pressure in the posterior chamber which will push the iris forward, causing the peripheral part of the iris to bulge anteriorly and it will cover over the trabecular meshwork causing high intraocular pressure.
Sometimes this condition can be intermittent and it will be relieved either by the pupil gets miosed or constricted as in sleeping or with medications or when production of aqueous humor decreases as in sleeping also.
Blocking of the pupil also occurs in normal physiological conditions that cause the pupil to dilute in relatively small eyes. These conditions are emotional stress and dim light rooms.
Complete blocking of the pupil occurs when there are 360 degree adhesion around the pupillary margin between the iris and lens and there is no space for the aqueous to pass through from the posterior to the anterior chamber.
The intraocular pressure will increase dramatically with severe pain, redness and blurred vision and the only treatment for it is by iridectomy with anti glaucoma eye drops.
Causes of Pupillary Block
1- Posterior Synechia
In which there will be membrane adhesion between the pupillary margin of the iris and the lens. Formation of these membranes occurs after inflammation in the anterior chamber like in chronic uveitis.
Treatment of posterior synechia is with medications early and surgical release of these synechia lately.
Steroid to reduce inflammation such as pred forte eye drops.
Cyclopentolate or atropine eye drops to dilute the pupil and release of these adhesions.
Elevation in intraocular pressure in this case can be treated with medications such as Timolol Eye Drops. Sometimes when these adhesions can not be released, we can do iris iridectomy, which is a hole in the iris that communicates between the anterior and the posterior chamber to bypass the block at the pupillary margin.
2- In Pseudophakic Patient
Pseudophakia means removal of natural lens and replace it with anterior chamber or posterior chamber artificial intraocular lens. Pupillary block causes in pseudophakic patients are either anterior chamber lens or posterior synechia. The anterior chamber intraocular lens (I.O.L) is inserted infront of the iris and it will covers the pupil which can block the flow of aqueous humor.
That is why all cases with anterior chamber I.O.L should have peripheral iridectomy to prevent pupillary block. Posterior chamber I.O.L can cause pupillary block in cases of inflammation that occur either post-cataract surgery with formation of posterior synechia or with chronic intra-ocular inflammation or uveitis.
3- Aphakic Patient
With cataract surgery there will be complete extraction of cataract and without Intraocular lens insertion. Either the posterior capsule still intact with no vitreous out in the anterior chamber or the posterior capsule is ruptured with vitreous in the anterior chamber.
Pupillary block causes in aphakic patient are vitreous in the anterior chamber or vitreous pushing the posterior capsule forward with pupillary blocking.
In case posterior capsule ruptured during cataract eye surgery, the vitreous will be in the anterior chamber and block the pupil with pupillary block and High I.O.P. To treat this condition, the surgeon should undergo anterior vitrectomy with iris iridectomy.
In case of intact posterior capsule, the vitreous can push out the capsule anteriorly through the pupil with blockage of the pupil. Treatment of this condition should be with iris iridectomy or with the insertion of posterior I.O.L
4- After Posterior Vitrectomy
Sometimes after posterior vitrectomy with silicon oil injection in the posterior segment, in which silicon oil can push out the intact posterior capsule, posterior I.O.L or even the natural lens through the pupil with pupillary block formation.
Sometimes in case that the posterior capsule is ruptured, the silicon oil can pass through to the anterior chamber with raise in the I.O.P. Treatment of these conditions with silicon oil is with iris iridectomy or silicon oil removal
Usually the position of iris iridectomy is superiorly but in case the silicon oil in the anterior chamber, this iris iridectomy should be done inferiorly.
5- Natural Lens
Natural lens can cause pupillary block in two ways, first the lens becomes large enough to block the pupil margin and this type of glaucoma is called phacomorphic glaucoma.
The second way is the anterior dislocation of the lens through the pupil with pupillary block. Treatment of this condition is with cataract extraction.