Charles D. Phelps

The pathogenesis of glaucoma in Sturge-Weber syndrome.

What is the cause of glaucoma in Sturge-Weber syndrome? Looking for the answer to this puzzling question, we examined 21 patients with the disease. Sixteen patients had gglaucoma: three bilateral and 13 unilateral. Episcleral hemangiomas were visible in all glaucomatous eyes. In general, the more extensive the hemangioma, the more severe was the glaucoma. During gonioscopy, blood could easily be made to reflux into Schlemms canal of glaucomatous eyes. Often the canal separated into multiple fine channels. Episcleral venous pressure, which we measured in 11 patients, was high in all glaucomatous eyes. These observations suggest that glaucoma in Sturge-Weber syndrome is caused by elevated episcleral venous pressure. Most likely, veins draining aqueous from the canal of Schlemm are part of an intrascleral or episcleral hemangioma. The canal of Schlemm itself may be part of the hemangioma. Arteriovenous shunts in the hemangioma raise episcleral venous pressure, which in turn elevates intraocular pressure.

The Normal Visual Field on the Humphrey Field Analyzer

To provide a bank of normal perimetric data, we tested the central and peripheral visual fields of 102 novice normal subjects using the Humphrey automated perimeter. All eyes used for visual field testing were first carefully examined to be sure that they were, indeed, normal. We calculated population means and standard deviations of each test location and for each decade for age. Average differential light sensitivity decreased with advancing age: -0.5 dB/decade at fixation, -0.6 dB/decade in the central (30-2) field, and -06. dB/decade in the peripheral (30/60-2) field. However, neither the slope nor the shape of the hill of vision changed with aging. Short-term fluctuation was not constant throughout the visual field, but instead was greater in the periphery than the center.

Measurement of intraocular pressure: A study of its reproducibility

Intraocular pressure was measured with Goldmann applanation tonometers by two independent examiners in 420 eyes. A difference between measurements of at least 3 mm Hg occurred in 30% of the eyes. Some evidence suggests that the differences between pressure measurements were caused by actual changes of intraocular pressure rather than by instrument inaccuracy or technician error. Der Innendruck von 420 Augen wurde mit dem Goldmann-Tonometer von zwei Untersuchern unabhängig voneinander gemessen. Ein Unterschied von 3 oder mehr mm Hg wurde bei 30% der Augen gefunden. Verschiedene Ergebnisse lassen vermuten, daß die Unterschiede in den Druckmessungen durch eine tatsächliche Änderung des Augeninnendruckes verursacht werden und weder durch Ungenauigkeit des Instrumentes noch durch Fehler der Untersucher.

Optic Disk and Visual Field Correlations in Primary Open-Angle and Low-Tension Glaucoma

If the amount of visual field loss is less than expected from the amount of optic disk cupping in low-tension glaucoma compared with primary open-angle glaucoma, it might imply a difference between the two conditions in the type of optic nerve lesion produced. To test this hypothesis, three observers independently examined, in a masked fashion, optic disk stereoscopic photographs of 127 eyes with primary open-angle glaucoma and 71 eyes with low-tension glaucoma. For each stereoscopic photograph the observer predicted whether the visual field loss would be mild, moderate, or severe. The visual field were then classified, according to the number of sectors defective on the Goldmann perimeter chart, as having mild (1 to 15 sectors), moderate (16 to 30 sectors), or severe (more than 30 sectors) visual field loss. For no observer did the frequency of underpredictions or overpredictions in the two conditions differ significantly. The results of this study, thus, did not support the theory that the optic disk damage in primary open-angle glaucoma differs from that in low-tension glaucoma.

Measurement of episcleral venous pressure.

Using materials available in any ophthalmology clinic, we constructed a useful and reliable instrument for measuring episcleral venous pressure. The instrument, a modification of the pressure chamber method of Seidel, utilizes a latex membrane and an air-filled chamber. These modifications facilitated ease of preparation for the measurement. Episcleral venous pressure in normal subjects was 9.0 +/- 1.6 mm Hg (mean +/- S.D.). Measurement of episcleral venous pressure facilitated diagnosis of diseases such as arteriovenous fistula and superior vena caval obstruction, which block drainage of venous blood from the orbit.

Prophylactic Timolol for the Prevention of High Intraocular Pressure after Cataract Extraction: A Randomized, Prospective, Double-Blind Trial

Eyes undergoing routine intracapsular cataract extraction (without alpha-chymotrypsin) often experience marked ocular hypertension in the first six hours after surgery. We conducted a randomized, prospective, double-blind study to determine if timolol maleate would prevent this increase in pressure. Thirty-five eyes undergoing routine cataract extraction were given a drop of either timolol 0.5% or placebo twice before and twice after surgery. Nine (56.3%) of 16 control eyes and 2 (10.5%) of 19 timolol-treated eyes had pressures above 30 mm Hg at six hours after surgery (P less than 0.025). Thus, prophylactic timolol 0.5% can substantially reduce the incidence of severe early postoperative ocular hypertension.

Visual Fields in Low-Tension Glaucoma, Primary Open Angle Glaucoma, and Anterior Ischemic Optic Neuropathy

We compared the type and location of visual field defects in 94 eyes with low-tension glaucoma, 225 eyes with primary open angle glaucoma, and 160 eyes with anterior ischemic optic neuropathy. The distribution of defects in two varieties of glaucoma were similar; both involved the upper half of the visual field more frequently, the lower half less frequently, and central vision much less frequently than did anterior ischemic optic neuropathy. These differences in distribution of field defects were independent of the severity of field loss and of patient age. The most frequent defects in both low-tension glaucoma and primary open angle glaucoma were superior nasal defects and superior arcuate scotomas; the most frequent defects in anterior ischemic optic neuropathy were inferior hemifield loss and central scotomas.

Contrast sensitivity in asymmetric glaucoma

We measured central contrast sensitivity in both eyes of 27 patients with asymmetric glaucomatous visual field loss or optic disc cupping. In 15 patients contrast sensitivity was less in the eye that by perimetry or ophthalmoscopy was the more severely damaged. In 10 patients contrast sensitivity was the same in the two eyes. In two patients, it was impaired more in the eye with the normal visual field. However, the latter two patients had ophthalmoscopic evidence of optic nerve damage (disc hemorrhage or large cup) in the eye with the lower contrast sensitivity, even though the visual field was normal. Asymmetry of contrast sensitivity was not found in normal control subjects.These results suggest that glaucoma does alter central vision, even when visual acuity remains normal and visual field defects are far from fixation. Contrast sensitivity may be impaired by a different mechanism than that which leads to visual dield loss. Although the two types of visual dysfunction often occur together, some patients may have more severe impairment of central vision (as measured by contrast sensitivity testing) in one eye and more severe loss of peripheral vision (as measured by perimetry) in the other eye.

Intraocular pressure in retinal detachment.

Relative hypotony in the affected eye was present in 40% of patients with uncomplicated unilateral retinal detachments. The average pressure asymmetry was only 1.3 mm Hg, but in one out of every four patients the difference was 3 mm Hg or more. In a control group, such a difference occured in only one out of every twenty patients. Relative hypotony persisted for longer than six months after scleral buckling operation, occuring even in patients that did not exhibit hypotony preoperatively.

Rieger's Syndrome: A Case Report With a 15-Year Follow-up

A 15-year follow-up examination of a boy with Riegers syndrome showed that the anterior segment changes in this disease may be slowly progressive in the absence of glaucoma or miotic treatment. The patient also had two recently recognized systemic features of the syndrome, umbilicus cutis and hypospadias.