Fig. 16.27 Appearance of the right macula of case 7 after vitrectomy surgery

presentation. Second, the perception that PRP worsens contracture of fibrovascular membranes

is prevalent among retina specialists, but has scant basis in peer reviewed literature.54–56 The

right eye shows worsening of an ERM temporally associated with supplemental PRP, but it cannot be said that the PRP caused the worsening. It may have occurred had PRP been withheld. It is unlikely that a clinical trial would ever be performed to determine an evidential basis for this perception. Third, the assessment of the effect of traction on visual function is also fraught with uncertainty. The center of the macula of the left eye was not detached, and several of the reviewers therefore did not consider vitrectomy surgery to be indicated, yet the case demonstrates that improvement can occur in such cases by relief of traction. Fourth, the clinical ability to judge ‘‘activity’’ of PDR is questionable; our reviewers were divergent in their assessments.57 In such cases, humility and careful longitudinal follow-up to detect change may be prudent. Finally, the use of intravitreal bevacizumab as an adjunct to surgery and laser

is far from standardized in 2009 as illustrated by the diversity of responses by the reviewers.9,34,58

Greater consensus regarding proper use of this drug may evolve with continued study and especially through well-designed prospective

randomized clinical trials regarding its many potential uses.g

16.8Case 8: What Is Maximal Focal/Grid Laser Photocoagulation for Diabetic Macular Edema?

16.8.1 Definition of the Problem

Although it is the rule in treating diabetic macular edema (DME) that multiple treatments will be necessary over time, eventually there is no more room for focal/grid laser treatment if DME persists. In Diabetic Retinopathy Clinical Research (DRCR) Network protocols and other studies, subjective definitions of maximal focal/grid laser are used. For example, here is the definition from the ISIS-DME study: ‘‘Maximal laser treatment was defined as a point at which the investigator felt that additional laser treatment would be of no benefit based on clinical judgement and the fluorescein angiogram.’’59 In DRCR Network studies, a fluorescein angiogram is not required to treat DME or to make a decision about whether maximal focal/grid laser treatment has been given. In the following cases (Figs. 16.28, 16.29, 16.30, 16.31, 16.32, 16.33, 16.34, 16.35, 16.36,

Fig. 16.28 Case 1 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

g Discussed by David J. Browning MD, PhD

Fig. 16.29 Case 2 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

Fig. 16.30 Case 3 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

Fig. 16.31 Case 4 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

Fig. 16.32 Case 5 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

16.37, and 16.38), patterns of focal laser used for center-involved clinically significant macular edema (CSME) are illustrated. All cases have persistent center-involved macular edema with central subfield mean thicknesses >250 mm on OCT despite previous treatment. Which case(s) have had maximal laser treatment and, in your hands, would not be offered any further focal/grid laser photocoagulation, but instead, would be declared treatment failures to that approach and either observed or treated with alternative therapies such as intravitreal or peribulbar pharmacologic therapy or vitrectomy surgery?

16.8.2 Discussion

A better designed exercise would be to have a sample of ophthalmologists examine the same set of patients together with their customarily acquired ancillary testing, but such is not possible within the constraints of a textbook. Acknowledging the limitations of the exercise and the data presented, we think the results are interesting to consider, if only to raise the seldom discussed issue ‘‘When does

Fig. 16.33 Case 6 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

Fig. 16.34 Case 7 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

one stop focal/grid laser? And what is maximal treatment?’’ Four of the co-authors returned comments on these cases. A redaction of their responses is shown in Table 16.1. Even with the small sample size, it is apparent that clinical judgement is variable on what constitutes maximal treatment.

Doctor B was reluctant to comment on 9 of the 11 cases. He mentioned that he relies exclusively on fluorescein angiography to determine where to apply re-treatment – to focal leaking microaneurysms

Fig. 16.35 Case 8 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

Fig. 16.36 Case 9 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

and ungridded areas of capillary nonperfusion – and therefore did not have as much information as he was accustomed to having to be able to respond. This was the approach outlined in the Early Treatment of Diabetic Retinopathy Study (ETDRS). In that study, ‘‘repeat fluorescein angiography was usually necessary to assess whether treatable lesions were present. All focal leaks more than 500 mm from the center of the macula were treated. Focal leaks 500 mm or less from the center of the macula were treated if the visual acuity was 20/40 or worse and if it was thought that the treatment would not destroy the remaining perifoveal capillary network. Grid

Fig. 16.37 Case 10 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

Fig. 16.38 Case 11 of 11 in a series addressing ‘‘What is maximal focal/grid laser photocoagulation?’’

treatment was not usually reapplied to areas that had already been treated.’’60

Twenty years after the ETDRS, the DRCR Network reported in one of its prospective trials that 49% of cases of CSME treated with focal/grid laser underwent treatment without fluorescein angiographic guidance.61 Internationally, the estimate is higher.62 It is not known if outcomes are different when focal/grid laser treatment is applied with or without fluorescein angiographic guidance because a randomized clinical trial of the question has not been performed. But because previously applied laser spots may be more easily detected from fluorescein angiography than from ophthalmoscopy alone, it is possible that decisions on maximal versus submaximal treatment depend on whether the ophthalmologist obtains the angiogram to inform his judgement.63 The point in this context is that variable use of fluorescein angiography may add to the variability among ophthalmologists in what constitutes maximal focal/grid laser.

Other pertinent comments to the question of maximal focal/grid laser were made. Three of four ophthalmologists remarked that cases 3 and 11 had received too much focal/grid laser – that is, above maximal. These cases were treated 20 years previously and demonstrate not only laser spots applied too close together and too intensely, but also the probable effects of laser scar expansion over 20 years.64 One ophthalmologist commented that he would not treat the thickened but nonperfused area of case 4. In the ETDRS, thickened but nonperfused areas of the macula up to 2 disk diameters from the center of the macula were treated