The Microperimetry of Resolved CWS in Hypertension and Diabetic Patients

Abstract

Purpose: : Retinal Cotton wools spots (CWS) are an important manifestation of retinovascular disease in hypertension(HTN) and diabetes(DM). We have shown that permanent structural changes can be imaged after resolution of these lesions. Our purpose is to evaluate retinal sensitivity after documented CWS regression. If a permanent defect can be seen, documentation of such deficits may be a way to determine lifelong cumulative retinal insult due to systemic disease.

Methods: : Scanning laser microperimetry using eye tracking and image stabilization was used to image macular resolved retinal CWS and normal control areas. This was done by overlaying images of the cotton wool spots 10 to 119 ( median 51) months after photographic documentation of the lesion. Image Stabilized Microperimetry was done using simultaneous Scanning Laser ophthslmoscopy and a step ladder microperimeter. (OPKO health, Miami, Fla.). The microperimetry algorithm was customized to use a step-ladder algorithm and a 108 micron target spot size of white light (Goldmann III). We determined retinal sensitivity in the area of the resolved CWS and compared it to adjoining uninvolved areas nearby.

Results: : We imaged a total of 34 lesions in 16 eyes (6 CWS in HTN patients and 28 CWS in DM). We used a paired analysis comparing the control and lesion areas in the same eye and used SAS GEE methods (SAS inc, Carey North Carolina) to control for intra-eye and intrapatient correlations. The mean sensitivity in the CWS lesion was 8.0000±5.4606 dB and in the control areas was 12.1909±3.4271 dB. The difference between CWS lesion and control area was statistically significant (p=0.0041). The DM sesnsitivity was significantly lower than the controls (p=0.0090). The HTN was also reduced vs control (p=0.0330). No significant difference between HTN lesions and DM lesions (p=0.1252). There was a trend suggesting that DM had a deeper scotoma than HTN (7.2143± 5.4796 dB vs 11.6667±3.8816 dB).

Conclusions: : Retinal CWS in DM and HTN leave permanent microperimetrically documented relative scotomas. Scotomas are deeper in eyes with DM than HTN possibly because the diabetics have a more impaired retinal circulation prior to the arteriolar infarction which produces the cotton wool spot. The device we used does use eye tracking technology to stabilize the Microperimetry testing image on the retina however the rate of eye tracking may not fully compensate for microsaccades which have a magnitude of 144 microns and 0.1~5 hertz.

Keywords: diabetic retinopathy • imaging/image analysis: clinical • retina