Regional variability in viual field enitivity during hypercapnia

Purpoe Previou invetigation have demontrated a relative vacular autoregulatory inefficiency of the inferior compared to the uperior retina in healthy ubject breathing increaed CO2. The purpoe of thi tudy wa to determine whether the uperior and inferior viual field enitivitie of healthy eye are imilarly affected during mild hypercapnia. Deign Experimental tudy. Method Viual field analyi (Humphrey Field Analyer; ITA tandard 24-2 program) wa carried out on one randomly elected eye of 22 ubject (mean age, 27.7 ± 5 year) during normal room air breathing and ioxic hypercapnia. The tudent paired t-tet were ued to compare the viual field indice mean deviation (MD) and pattern tandard deviation (PD) for each breathing condition. A econdary, ectoral analyi of mean pointwie enitivity wa performed for each condition. In each cae a P value of <.01 wa conidered tatitically ignificant (Bonferroni corrected). Reult Viual field MD wa −0.23 ± 0.95dB during room air breathing and −0.49 ± 1.04dB during hypercapnia (P = .034). ectoral pointwie mean enitivity deteriorated by 0.46dB (P = .006) in the upper viual hemifield during hypercapnia, wherea no ignificant difference wa oberved for the lower hemifield (P = .331). Concluion The upper viual hemifield exhibited a ignificantly greater degree of deterioration in pointwie viual field mean enitivity compared to the lower hemifield during hypercapnic condition. Thi ugget that the upper viual hemifield and hence inferior retina i more uceptible to inult during hypercapnia than the uperior retina in healthy individual. A regional uceptibility of inferior retinal function to altered vacular or metabolic effect may account for the earlier and more frequent inferior nerve fibre damage aociated with glaucomatou optic neuropathy.