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Clinical Conundrums: Case History 1
I recently examined a 63 year old patient who came in for a re-check. He had been seen by my colleague a few weeks earlier and at the time his spectacles were updated; one pair for distance and one pair for near.
He came in complaining of not being able to read with both eyes open and that everything in the Left eye appeared to slant. He therefore found it more comfortable to close his left eye whilst reading.
His previous ocular history was as follows:
Summer 2006: R cataract extraction
Autumn 2006: L retinal detachment, followed by repair, L cataract extraction, during which a rise in IOP resulted in short-term Timolol medication.
Currently his IOP is stable and he has been taken off Timolol.
Refractive status:
R +0.50/-0.75 x90
L -0.50/-1.00 x120 Near Add +2.50 R&L
Distance Oculomotor Balance:
R 9 prism dioptres UP with 1.5 IN
He had been previously prescribed 8 prism dioptres UP in RE and he was happy with this and is currently not experiencing any problems.
Near Oculomotor Balance:
I tried prescribing the prism in his reading glasses but this was not helpful.
So, what next?
Simon Frackiewicz // Mar 3, 2007 at 1:56 pm
Hi Priya,
Your case does indeed seem very interesting. Below are a few of my thoughts on how I personally would proceed.
Firstly, did the Px have surgery to repair their detachment, i.e. did they have a scleral buckle fitted? If so, as you are no doubt aware, the vitreoretinal surgeons disinsert some of the rectus muscles in order to make the repair, which may not always be put back in the same place. It is a common cause of diplopia in these cases, either from incorrect repositioning of the eye muscles, or from mechanical limitation caused by the buckle. A buckle compressing the globe may cause ’slanting’ of the image, as may a laterally displaced vertical rectus muscle (i.e. if the superior rectus muscle was inserted nasally, it would have less incyclorotational power, and thus cause a relative excyclo deviation.)
If there is no buckle, then I would be interested to know the origin of the vertical deviation. What did ocular motility show? Was there a mechanical or neurogenic pattern? Which way did the image slant? Was it always there, but not noticed due to poor vision from cataract, or could it have been caused by damage to the vertical muscles at the time the retrobulbar anaesthetic was injected for the cataract surgery? I know of at least one study which showed that the LEFT inferior rectus muscle can become damaged if the anaesthetic block is given by a right-handed anaesthetist - bizarre, but true! This would fit with a Base UP prism in the right eye (L/R deviation), which would increase on depression. Whilst ’slanting’ of an image suggests torsion, which in turn implicates the oblique muscles, the vertical recti also have a torsional tertiary action, which is what they may be experiencing.
Next, you mention prism in his specs, and that he is happy with his DV pair. Are there already prisms in the NV pair? It may be useful to measure the deviation in depression with Maddox rod, and maybe even use the double rod test to measure the extent of torsion. Remember that if there is a mechanical limitation of the LEFT eye, a L/R deviation in the primary position may well become R/L in depression, thus needing a change in prism base direction. Equally, a vertical muscle weakness (e.g. Left inferior rectus or superior oblique) will increase in downgaze. I’d also suggest from the patient’s point of view that Fresnel prisms would be ideal to use in the short-term so as to avoid them needing too many reglazes.
Sorry for the disjointed nature of the above. To summarise, my approach would be:
1 - compare the size of deviation in primary position and depression
2 - establish neurogenic/mechanical nature of diplopia (i.e. ductions vs. versions)
3 - try to correct in depression with Fresnel prisms, consider occlusion if not successful
4 - if necessary, refer to Orthoptist for investigation with Hess screen (bear in mind that Fresnel prisms are free to the patient in the HES)
I hope this helps. It would be great to learn the outcome
Simon
Priya Morjaria // Mar 6, 2007 at 1:43 pm
Hi Simon
Thanks for the detailed reply. Much appreciated.
Have booked the patient back in so that I can do a full BV examination taking in board the recommendations that you have made.
Shall let you know the outcome.
Thanks for the help once again.
Priya
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