Retinal cryotherapy in the management of proliferative diabetic retinopathy

Evaluation of the blood–aqueous barrier by laser flare cell photometry following retinal cryocoagulation

PURPOSE

To evaluate the influence of peripheral 360 degrees retinal cryocoagulation on the blood-aqueous barrier of patients with retinal vascular disorders.

METHODS

The aqueous of 50 eyes of 50 patients with diabetic retinopathy or central vein occlusion was measured by laser flare photometry (FC-2000, Kowa) before peripheral 360 degrees retinal cryocoagulation and 1 day, 1 week, and 1 month thereafter.

RESULTS

Mean aqueous flare values before treatment were 15.7 (+/-8.2) photon counts/ms; mean cell count was 9.8 (+/-14.8) cells/0.5 mm(3). One day after retinal cryocoagulation flare values had increased statistically significantly to a mean of 39.2 (+/-85.8) photon counts/ms, while the increase in mean cell number to 15.0 (+/-37.2) cells/0.5 mm(3) did not reach statistical significance. One week following treatment, mean flare values had dropped to 30.9 (+/-49.6) photon counts/ms and were no longer significantly elevated compared with baseline, while the mean cell count of 11.1 (+/-27.0) cells/0.5 mm(3) was now statistically significantly elevated compared with baseline. One month after treatment the flare values had decreased to a mean of 19.7 (+/-12.0) photon counts/ms, and mean cell count had decreased to 8.1 (+/-10.4) cells/0.5 mm(3); at this point neither parameter showed a statistically significant difference from baseline values.

CONCLUSION

Peripheral 360 degrees retinocryocoagulation does not lead to permanent disturbance of the blood-aqueous barrier.

Transconjunctival anterior retinal cryotherapy for proliferative diabetic retinopathy

Transconjunctival anterior retinal cryotherapy (ARC) for proliferative diabetic retinopathy (PDR) in 408 eyes was reviewed retrospectively. Of 266 eyes available for analysis for treatment effect on neovascularization, 138 (52%) had reduced neovascularization at 6 months. Eighty (30%) had no change in neovascularization, and 48 (18%) had increased neovascularization at 6 months. Factors having a significant effect on reduction of neovascularization were duration of diabetes and severity of retinopathy. Of 238 eyes available for analysis for treatment effect on vitreous hemorrhage at 6 months, 118 (50%) had reduced vitreous hemorrhage, 80 (33%) had no change, and 40 (17%) had increased vitreous hemorrhage. Severity of vitreous hemorrhage significantly affected the outcome in the subgroup of eyes with both neovascularization and vitreous hemorrhage. Of the total 408 eyes in this series, at 6 months, 172 (44%) had improved visual acuity, 89 (23%) had no change, and 126 (33%) had decreased visual acuity. Retinal detachments developed in 17 eyes (4%) post-treatment, 68 eyes (17%) had significant recurrent vitreous hemorrhage, and 61 eyes (15%) eventually underwent vitrectomy.

Cryoapplication in diabetic retinopathy

Thirty-five patients with diabetic retinopathy were treated with cryoapplication. This was used as an alternative to Argon laser or Zenon photocoagulation because the media was opaque from vitreous hemorrhage or cataract. It was difficult or impossible to treat with photocoagulation. The clinical impression indicates that cryoapplication is effective, showing adequate pigmentation and chorioretinal scarring with regression of diabetic retinopathy changes. However patients with vitreo-retinal fibrosis became frequently worse weeks later. This is considered a contraindication. The use of cryoapplication in diabetic retinopathy is recommended in situations where the ocular media is not clear, such as vitreous hemorrhage and cataract. It can also be used if there is difficulty with laser photocoagulation following lens implantation. It may be valuable in some developing countries where photocoagulation is not available. Cryomachines are frequently used in eye camps. It is inexpensive and does not necessarily require electricity.

Anterior retinal cryotherapy in diabetic vitreous hemorrhage

Recurrent vitreous hemorrhage associated with proliferative retinopathy can occur in eyes that do not satisfactorily respond to argon laser pantretinal photocoagulation. To evaluate the effect of relatively low-risk surgical intervention, we performed peripheral retinal cryopexy on 24 eyes of 23 diabetic patients with proliferative diabetic retinopathy and vitreous hemorrhage. In most cases, cryopexy followed complete or nearly complete panretinal photocoagulation which did not prevent subsequent vitreous hemorrhage. Existing vitreous hemorrhage cleared postoperatively in 23 of 24 eyes. The best corrected visual acuity improved in 15 eyes, remained unchanged in five, and worsened in four. Four postoperative anterior segment complications resolved completely within a short time. One patient, a 68-year-old woman who had had diabetes for 18 years, postoperatively had a macular hole in one eye and macular edema with tractional retinal detachment in the other.