Oxygen dissociation curveinEales's disease

SUMMARY Theoxyhaemoglobin dissociation curve(ODC)was investigated in15patients with Eales's disease and11 controls totest thehypothesis thatEales's disease iscausedbyretinal hypoxia secondary toimpaired oxygenrelease fromtheblood. Patients withtheperipheral fornofEales's disease didnothaveanysignificant difference intheir P50 values whencompared withthecontrols. However, theP50values weresignificantly lower(P<0005) forthepatients withmixedretinopathy. Thisdegree ofincreased oxygenaffinity isnotphysiologically significant butmay reflect an intrinsic abnormality oftheredcells inthese cases. Retinal perivasculitis isadescriptive termapplied to conditions wherethere issheathing andocclusion oftheretinal vessels whichmaybeassociated with retinal haemorrhages, new vessel growth, and vitreous haemorrhages whichultimately leadto retinal detachment, cataract, andglaucoma. Many ofthese cases aresecondary touveitis orsystemic disease, butinthemajority retinal perivasculitis occurs asaprimary oridiopathic condition ofthe eye.Thesepatients may beconsidered tohave Eales's disease, since theytypify hisoriginal description' 2 of'primary retinal haemorrhages in youngmen'. Thisappears tobeanoninflammatory condition andisthesubject ofthis paper. However, itmustbestressed that Eales's disease isadescriptive termwhichprobably shelters manyentities. Eales's disease usually affects healthy males between theagesof20and30years, butitmayoccur atanyageandalso infemales. Theclinical appearancesmayrangefromthose ofperipheral vessel closure andnewvessel growth resembling sickle cell retinopathy (Fig. 1)tothoseofdiffuse vascular disease anddiscneovascularisation