Intraocular pressure-dependent light sensitivity in glaucoma

The intraocular pressure-dependent light sensitivity of discrete retinal points was measured using the Heijl-Krakau automated light-emitting diode perimeter with an appropriate software program. A total of 300 measurements of light sensitivity were recorded from six retinal points during the test period of 8-10 min; increased intraocular pressure was induced using a Langham scleral suction-cup system. The ocular pulsatile blood flow and the ophthalmic arterial pressure were measured in the same patients. The fluctuation of the light sensitivity was less than 5% over the test period in healthy eyes and remained unaffected by an intraocular-pressure increment of 20 mm Hg; a small decrease of sensitivity occurred at a pressure increment of 30 mm Hg. In glaucomatous eyes the light sensitivity was lower and the fluctuation of the light sensitivity at some but not all retinal points was substantially greater than in the controls. In the glaucomatous eyes, and intraocular-pressure increment of 20 mm Hg increased the fluctuation and decreased the light sensitivity. The pulsatile ocular blood flow was lower in the glaucomatous eyes but not severe enough to be solely responsible for the loss of vision. The coexistence of retinal points with normal and abnormal stabilities of light sensitivity in glaucomatous eyes was consistent with impaired blood flow in the lamina cribrosa.