angiography in guiding treatment but published guidelines to direct retreatment are not publicized.70 A second respondent believed that fluorescein angiography-determined enlargement of the foveal avascular zone carries a poorer prognosis in managing diabetic macular edema and that this information is helpful in counseling patients. Although intuitively logical such subclassification of diabetic macular edema based on degree of macular ischemia has not been demonstrated to enhance patient care by allowing advice on a differential natural history or differential response to therapy.71

The discussant believes that the approach of the second respondent reflects a fundamental change in our current clinical expectations in managing diabetic macular edema. The Early Treatment Diabetic Retinopathy Study defined clinically significant macular edema as the indication to benefit from focal/grid laser. The demonstrated benefit of that treatment was to decrease the risk of developing moderate visual loss (defined as loss of 15 or more letters between baseline and follow-up visit). Reports with intravitreal triamcinolone, intravitreal antiVEGF agents, and focal/grid laser photocoagulation demonstrate that visual improvement is not uncom-

mon following treatment of diabetic macular edema.72,73,48 When patients currently demonstrate

visual loss following therapy for diabetic macular edema clinicians tend not to counsel patients that ‘‘their vision would have been even worse had treatment not been done’’ but instead to search for alternative therapies to reverse the decline. The discussant believes that in managing diabetic macular edema we are in a current era where loss of vision is considered a ‘‘failure’’ of therapy and that improvement in vision may not be an unreasonable hope.i

16.10Case 10: Macular Edema Following Panretinal Photocoagulation for Proliferative Diabetic Retinopathy

A 72-year-old man with diabetes of 22 years duration had focal/grid laser photocoagulation for diabetic macular edema with regression bilaterally. His

best corrected visual acuity was R – 20/63, L – 20/ 25. On regular follow-up he was found to have small areas of neovascularization elsewhere (NVE) without preretinal hemorrhage in each eye. He underwent panretinal photocoagulation (PRP) of the right eye and called in to report blurring 2 weeks later. He wanted to put on hold the scheduled panretinal photocoagulation of the left eye. Examination revealed vision of R – 20/63, L – 20/25. The maculas were clinically unchanged and without thickening, but the pre-PRP and post-PRP Optical Coherence Tomograms (OCT) are shown in Fig. 16.41. How would you manage this patient?

16.10.1 Discussion

This case demonstrates the importance of listening to the patient who notes vision loss even though Snellen visual acuity remains unchanged. The OCT showed recurrent macular thickening follow-

ing the PRP laser, which is a known complication of this treatment.31,74,75 OCT often detects macular

edema not seen clinically, and macular edema fluctuations can cause symptoms without diminution of visual acuity.76

There are several reasonable management options for the right eye. One is to simply observe the eye as the edema may resolve. If the patient is sufficiently distressed that an intervention is deemed necessary, the least invasive treatment option would be a trial of topical steroidal or nonsteroidal drugs, an approach advocated by one of the five physicians who reviewed this case. There is no published evidence to support topical therapy in post-PRP recurrence of DME, but there is a biological rationale, assuming that the recurrence is based on inflammation and that the drugs can penetrate to the posterior segment. Other reasonable options would include periocular or intravitreal triamcinolone injection or intravitreal bevacizumab injection.77,64 Periocular triamcinolone injection might be more effective than topical therapy and would be associated with a 10% risk of intraocular pressure elevation and 10% risk of ptosis.77 Intravitreal triamcinolone would probably be more effective in

reducing the edema, although with an increased risk of intraocular pressure elevation and cataract formation and the additional risk of vitreous hemorrhage, hypotony, and endophthalmitis.72,78–81 An intravitreal injection of bevacizumab could be considered, although several reviewers thought that it is less effective than triamcinolone in such a circumstance.82 A fluorescein angiogram might be useful; if there were angiographic evidence of worsening focal retinopathy with untreated microaneurysms then adding focal photocoagulation would be reasonable assuming maximal photocoagulation had not already been applied.

For the left eye, there is no rush to treat based on the non-high-risk characteristics of the NVE, and respect for the patient’s reluctance to proceed suggests that observation for a period until the right eye stabilizes would be prudent. Ideally, the patient was told before the right eye PRP that his vision

might be worse after laser, which now makes it easier to explain that this blurring will likely resolve over time with observation or with one of the treatments outlined previously. Once the right eye has improved or stabilized, then treatment of the left eye might be encouraged, but perhaps preceded by a peribulbar triamcinolone injection to reduce the chance of post-PRP DME. The PRP laser treatment might be split into small sessions to prevent reactive edema, although in an eye with no edema, there is evidence that multiple session and single session PRP are associated with similar rates of post-PRP DME.83 An alternative acceptable plan would be continued deferral of PRP with close serial observation until high-risk characteristics were reached.j

j Discussed by David G. Telander MD, PhD