Manometric Studies

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Congenital Glaucoma

This clinical condition provides a dramatic example of the absenceof a normal outflow system and the effects on intraocular pres-sure (IOP), the outflow facility, and the effect of high IOP on thecornea. The clinical signs of congenital glaucoma include thicken-ing, edema, clouding, and increased diameter of the cornea. Thecorneal edema and swelling precludes use of indentation andGoldmann tonometers to measure the IOP. Under these conditions,

cannulation of the anterior chamber using a manometric techniqueprovides a direct way to evaluate the IOP and to investigate thepossibility of surgical therapy.

A needle with a double-cutting edge connected to a bottle ofsterile saline set at approximately 4050 mmHg and connected to asterilized pressure transducer is inserted from the area of the cor-neal scleral junction and directed toward the middle of the anteriorchamber. The steady state IOP is determined by a short recordingof the IOP (Fig. 10.1). The steady state IOP in this patient was 40mmHg, the pulse amplitude was 2.2 mmHg, and the corresponding

rate of pulsatile blood flow was 365 l min1

. An attempt was thenmade to open up the trabecular meshwork with the cutting edgeof the recording needle; the needle was then brought into contactwith the trabecular meshwork and a cut of approximately 10 wasmade into the Schlemms canal. In this patient success was immedi-ate and the IOP started to fall (see Fig.10.1) with a new state IOPof 17 mmHg. In this patient it required only a very small openingthrough the meshwork to achieve a normal outflow and IOP. Fullrecovery ensued, and a normal IOP and transparency of the corneawere confirmed at 1 year.

This clinical case gave a good example of the abnormal drain-age of aqueous humor resulting in an abnormally high IOP from a

10Manometric Studies

on the Intraocular Pressureand Vascular Circulation in

Ophthalmic Disease

M.E. Langham, Ischemia and Loss of Vascular Autoregulation in Ocular andCerebral Diseases: A New Perspective, DOI: 10.1007/978-0-387-09716-9_10, Springer Science + Business Media, LLC 2009

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56 Chapter 10 Manometric Studies on the Intraocular Pressure and Vascular Circulation

mechanically induced high resistance in the trabecular meshwork,while the flow resistance distal to the canal of Schlemm remainedessentially normal.

This patient formed one of a series of four similar cases on chil-dren of less than 2 years of age with congenital glaucoma. In onecase, the IOP was 35 mmHg, but attempts to cut open the trabecu-lar meshwork failed despite making a penetrating cut exceeding

180. It was concluded that the abnormal outflow was due to theabsence of a normal trabecular meshwork and Schlemms canal,and the possible absence of a normal intrascleral drainage system.In the remaining two cases, the initial IOPs were 26 and 30 mmHg,respectively, and the operations were successful in normalizingthe IOP with several cuts into the trabecular meshwork, each ofapproximately 20.

Normal Adult Eyes

An opportunity to examine the flow resistance in the trabecularmeshwork in normal eyes was found in living eyes of severalyoung adults who had developed small melanomas in the choroid.In a typical case on a male of 22 years, the IOPs in the affected andunaffected eyes were 18 and 18 mmHg, respectively, measured byGoldman applanation tonometry, and the corresponding outflowfacilities measured by conventional indentation topography were0.22 and 0 23 l min1mmHg, respectively. On the basis of the sym-metry of the results, it was concluded that the IOPs and the aqueoushumor dynamics in the pairs of eyes were normal.

The affected eye was enucleated and measurements of the IOPdecay curves were made immediately. Analysis of the pressure

Figure 10.1. The IOP in a child of 2 months with congenital glaucomaand the results of surgery. The first recording shows the IOP approach-ing its steady state of 45 mmHg. The second recording shows the IOPdecay curve approaching the new steady state of 17 mmHg after a limitedsection (approximately 10) of the occluded angle using the sharpenedcannulating needle (From Langham.21 Reprinted from Glaucoma, TutzingSymposium. Used with permission from Basel-Karger.)


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Adult Open Angle Glaucoma 57

decay curve in the enucleated eye indicated an outflow facility of0.4 l min1 mmHg. The trabecular meshwork was then openedwith the cutting edge of the recording needle and the IOP decaycurve was recorded. The new outflow facility following the trab-eculectomy was 0.3 l min1 mmHg. The results confirmed the

marked increase in the outflow facility following enucleation andthe major resistance to outflow to be distal to Schlemms canal inthe living eye.

Similar results were recorded on two further enucleated eyes, andin both cases the major site of the outflow resistance was distal toSchlemms canal.

Adult Open Angle Glaucoma

A manometric investigation was made on a patient who had been

treated for open angle glaucoma for many years and then examinedwithin 3 h of death (in the morgue). Glaucomatous field loss hadbeen present in both eyes for more than 20 years and the patienthad been treated with increasing concentrations of pilocarpine andepinephrine for many years. The IOP recordings over the yearsranged from 23 to 29 mmHg in both eyes and the outflow facilitiesmeasured by conventional tonography were approximately 0.100.13 l min1mmHg in the two eyes. Perfusion studies were madeon one of the eyes in situ. The outflow facility based on analysis ofthe pressure decay curve from an IOP of 35 mmHg was 0.3 l min1

mmHg and, after opening the trabecular meshwork, increased to0.4 l min1mmHg. Thus, in this glaucomatous eye, the abnormallyhigh outflow resistance was distal to Schlemms canal and not inthe area of the trabecular meshwork.


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