When you examine the anterior chamber or the anterior vitreous in the posterior chamber with a slit lamp, the proper illumination is key to performing a thorough evaluation of these structures. In this second of our two-part mini-series Turn Up the Light, I present two additional cases that illustrate how important it can be to crank the rheostat higher.
Case 1: Slit Lamp Exam Of the Anterior Chamber
History. A 33-year-old female complained of redness, pain and decreased visual acuity in the left eye for the past 18 hours. This was her fourth episode with these symptoms; the first occurred 15 years earlier, and the next two occurred two years and one year before this visit.
Clinical findings. Visual acuity was 20/20- O.U. Applanation tonometry yielded intraocular pressure readings of 17mm Hg O.D. and 10mm Hg O.S. Slit lamp exam showed 3+ cells and fine keratic precipitates in the left eye, with no hypopyon. All other findings were normal.
I diagnosed anterior uveitis in the left eye, and prescribed homatropine 5% q6h; Pred Forte 1% (prednisolone acetate, Allergan) q30 min x 6h, then q1h; and TobraDex (tobramycin and dexamethasone, Alcon) at bedtime. (I prefer to prescribe steroid ointment for overnight use, but because it is not available without the antibiotic, I prescribe TobraDex. The other option is to have the patient wake up a few times a night to apply the steroid drops.) I instructed the patient to return for follow-up in 24 hours.
Under normal illumination (left), the cells in the anterior chamber are difficult to see, but turning up the rheostat yields a much more illuminating picture (right).
Follow-up. The cells had increased, and hypopyon was present. I decided that this patient required oral medications, which a consulting physician prescribed.
Treatment now consisted of prednisone, to be tapered from 60mg to 20mg a day over three weeks, then continuing with topical drops. Her iritis resolved in 2-3 weeks on this medication schedule.
Discussion. You will always miss cells in the anterior chamber unless the rheostat is turned up bright enough. I have been guilty of this, and so have almost everyone I have worked withstudents, O.D.s and M.D.s.
If you have a patient with a red eye, the diagnosis of primary or secondary iritis is easy to miss. As this case illustrates, 3+ cells are hard to miss, but 1+ cells are easy to miss unless the light is turned up.
Turn up the rheostat all the way. Use a very narrow slit section and set the light to focus in the anterior chamber space.
Case 2: Slit Lamp Exam of Anterior Vitreous
History. A 63-year-old male said that for the past two weeks the vision in his right eye had appeared as if a shade was pulled down over his eye. About three months before this visit, he said that he had noticed flashes in the right eye; two months later he noticed that his vision was involved.
Tobacco dust (Shafers sign) was much easier to visualize in this patient with the rheostat turned to the highest setting (low rheostat above, high setting below).
He did not seek out care because he was vacationing abroad. He said he had never needed distance glasses, only readers.
Clinical findings. Visual acuities were finger counting at 6 feet O.D. and 20/20 O.S. A dilated, indirect slit lamp exam revealed 2+ Shafers sign, or tobacco dust, in the anterior vitreous.
Discussion. If the patient complains of seeing spots, floaters or haze, I always check the status of the anterior vitreous with a slit lamp exam through a dilated pupil before I put on my indirect scope. This will give me a good idea of whether the problem is inflammatory (white cells), a retinal break (pigment cells or red cells) or a posterior vitreous detachment. By turning up the slit lamp rheostat all the way, youre better able to view the anterior vitreous.
Using a narrow slit section, view behind the lens into the anterior
vitreous area. It helps to have the patient look up and then back to straight fixation. With the illumination turned up, you should see the vitreous moving.
Look at the normal structure. In patients without a history of inflammation, trauma or pigment dispersion syndrome, there usually will be no pigment in the vitreous. If you do see pigment cells in the vitreous and the patient complains of sudden, multiple spots, you probably have a retinal break.
I hope that these suggestions will help you detect significant clinical details and make the correct diagnosis more readily. I continually must remind myself in the clinic to turn up the light with both the slit lamp and BIO. But when I do, the results are often enlightening and illuminating.
Dr. Garston is professor of optometry at New England College of Optometry, Boston, and senior staff optometrist at the Massachusetts Institute of Technology Medical Department in Cambridge, Mass. He is also on staff at Harvard University Health Services in Cambridge, and has been an optometric educator for more than 30 years.
