Clinical and Experimental Ophthalmology

2003;

31

: 305–309

Original Article

_____________________________________

Original Article

Clinical outcomes following laser photocoagulation treatment for diabetic retinopathy at a large Australian ophthalmic hospital

Qing Yi

MB MPH

,

1

Parapun Bamroongsuk

MD

,

1,2

Daniel J McCarty

PhD

,

1,3

Bickol N Mukesh

PhD

1

and C Alex Harper

FRANZCO

1

1

Centre for Eye Research Australia, University of Melbourne, Melbourne, Victoria, Australia,

2

Department of Ophthalmology, Siriraj Hospital, Mahidol University, Bangkok, Thailand, and

3

Marshfield Medical Research Foundation, Marshfield, Wisconsin, USA

A

BSTRACT

Objective:

To evaluate clinical outcomes of diabetic retin-opathy laser treatment at a large Australian ophthalmichospital.

Methods:

A retrospective medical record review of allpatients who had initial laser treatment for diabetic retinop-athy at the Royal Victorian Eye and Ear Hospital fromJanuary 1997 to December 1998.

Results:

The study included 322 eyes from 203 patients.The mean age was 65.8 years (range 18–89) and the meanfollow up was 18 months (range 2–33). Focal photocoagu-lation treatment alone was performed in 238 eyes. Clinicallysignificant macular oedema (CSME) resolved in 218 (91.6%)eyes. Vision was improved or maintained in 137 (57.6%) eyes.Moderate visual loss occurred in 49 (20.6%) eyes. Panretinalphotocoagulation (PRP) was performed in 84 eyes, including37 eyes with PRP alone and 47 eyes with PRP and focaltogether. Neovascularization regressed in 55 (65.5%) eyes.Vision was improved or maintained in 52 (61.9%) eyes. Mod-erate visual loss was observed in 20 (23.8%) eyes and severevisual loss was observed in 4 (4.8%) eyes.

Conclusions:

The clinical outcomes reported here aresimilar to those reported in other studies.

Key words:

Australia, clinical outcomes, diabetic retino-pathy, photocoagulation.

I

NTRODUCTION

Diabetic retinopathy is one of the leading causes of blind-ness worldwide. The prevalence of retinopathy in Australian

diabetic populations ranges from 21% to 36%.

1

Laserphotocoagulation treatments, if appropriately timed andrigorously applied, can significantly reduce the risk of visualloss in patients with proliferative diabetic retinopathy(PDR) or clinically significant macular oedema (CSME).

2–5

We have previously reported that the timing and para-meters of retinal photocoagulation treatment for diabeticretinopathy at a large Australian ophthalmic hospital werefound to be generally consistent with the AustralianNational Health and Medical Research Council (NHMRC)clinical practice guidelines.

6

Here we present the clinicaloutcomes following retinal photocoagulation for thesepatients.

M

ETHODS

This study was conducted at the Royal Victorian Eye andEar Hospital (RVEEH), a large ophthalmic tertiary referralhospital in Australia.

The methods for this study have been previously pub-lished.

6

Briefly, the RVEEH hospital computerized informa-tion system (PICK system) was searched and medicalrecords were retrospectively reviewed to identify all patientswho commenced initial argon laser treatment (panretinalphotocoagulation or focal treatment) for diabetic retinopa-thy during the period from January 1997 through December1998. Patients having had any diabetic retinopathy lasertreatment prior to the study period were excluded from thestudy. Data abstracted from the medical records includedpatient age, sex, diabetes onset, duration, treatment, gradingof patient’s retinopathy stage prior to laser treatment, typeof laser treatment, visual acuity before treatment and at lastfollow up, retinopathy changes, and treatment complica-tions.

Laser treatment protocols were based on Early TreatmentDiabetic Retinopathy Study treatment protocols and

�

Correspondence:

Dr Alex Harper, Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne, Vic. 3002,

Australia. Email: harperca@unimelb.edu.au

306 Yi

et al

.

NHMRC guidelines, and details of treatments in this groupof patients have been published.

6

Diabetic retinopathystages were graded using a simplified Wisconsin system inaccordance with the NHMRC guidelines.

1

Snellen chartwas used to record visual acuity. ‘Pin hole’ visual acuity wasused as best-corrected visual acuity. Moderate visual losswas defined as loss of 3 lines or more in logMAR chartbetween baseline and last follow up.

4,7

Snellen chart visualacuity was converted to logMAR visual acuity to assessmoderate visual loss.

8

Severe visual loss was defined as visualacuity of less than 6/60 at last follow up. ‘Regression’ ofproliferative retinopathy was recorded as an outcome if thepatient notes specified that there was evidence of regressionof new vessels on clinical examination. ‘Resolution’ ofmacular oedema was recorded as an outcome if the patientnotes specified that CSME had resolved and/or the maculawas dry to clinical examination.

Continuous variables were checked for normality. Statis-tic analysis included comparison of proportions using chi-squared test and comparison of means using Student

t

-test.SPSS for Windows (version 9.0.1; SPSS, Chicago, IL, USA)was used for statistical analyses. This study was approved bythe RVEEH Human Research and Ethics Committee.

R

ESULTS

A total of 322 eyes from 203 patients were identified ashaving initial argon laser photocoagulation for diabeticretinopathy at the RVEEH from January 1997 to December1998. Focal photocoagulation was performed in 238 eyes of145 patients and panretinal photocoagulation (PRP) wasperformed in 84 eyes of 58 patients, including 37 eyes withPRP alone and 47 eyes with PRP and focal treatmenttogether.

The mean (

±

SD) age of the patients was 65.8

±

10.4 years(range 18–89 years) and 54% were men. Compared to PRPpatients, patients with focal treatment were older (67.3

vs

62.2,

P

= 0.006), they had a higher percentage of diabetesonset after age 30 (98.6%

vs

86.2%,

P

= 0.001) and weremore likely to be non-insulin treated (68.3%

vs

53.4%,

P

= 0.05) (Table 1).

The overall mean duration of follow up was 18

±

5.7months (range 2–33 months). Only one eye had follow upof less than 6 months. Eyes with focal treatment had longerfollow up (mean

±

SD 18.7

±

5.8 months; range 5–33 months)when compared to eyes with PRP treatment (mean

±

SD16.1

±

5.1 months; range 2–27 months).

Focal treatment

All 238 eyes with focal photocoagulation treatment alonehad CSME at the time of treatment. Of those, 194 (81.5%)eyes had mild/moderate non-proliferative diabetic retino-pathy (NPDR), 40 (16.8%) eyes had severe NPDR and four(1.7%) eyes had proliferative diabetic retinopathy (PDR).More than half (61.8%) of the eyes had visual acuity of 6/12or better prior to laser treatment (Table 2).

The majority (216, 90.8%) of the first follow ups afterinitial focal treatments were performed within 4 months, 13(5.5%) were between 4 and 6 months, and nine (3.7%) werebetween 6 and 10 months (overall range 0.4–9.8 months).

Table 1.

Characteristics of patients treated for diabetic retinopathy

Characteristic Total (

n

= 203)Focal alone (

n

= 145)PRP

(

n

= 58)

P

-value

Age (years)Mean

±

SD 65.8

±

10.4 67.3

±

9.0 62.2

±

12.7 0.006Range 18–89 38–89 18–82

Male (

n

, %) 109 (53.7) 72 (49.7) 37 (63.8) 0.07Duration of diabetes (years)

Mean

±

SD 14.7

±

7.6 14.4

±

7.8 15.3

±

7.3 0.45Range 1–40 1–40 2–30

Onset of diabetes at

≥

30 years old (

n

, %) 193 (95.1) 143 (98.6) 50 (86.2) 0.001Diabetic treatment without insulin (

n

, %) 130 (64.0) 99 (68.3) 31 (53.4) 0.05

PRP, panretinal photocoagulation.

Table 2.

Retinopathy stage and visual acuity at baseline inpatients treated for diabetic retinopathy

Baseline result Focal alone (

n

= 238)No. eyes (%)

PRP (

n

= 84) No. eyes (%)

Retinopathy stageMild/moderate NPDR 194 (81.5) 0Severe NPDR 40 (16.8) 3 (3.6)PDR 4 (1.7) 3 (3.6)High-risk PDR 0 54 (64.3)Advanced PDR 0 24 (28.6)

Visual acuity6/6 or better 39 (16.4) 12 (14.3)<6/6–6/12 108 (45.4) 15 (17.9)<6/12–6/60 89 (37.4) 50 (59.5)<6/60 2 (0.8) 7 (8.3)

NPDR, non-proliferative diabetic retinopathy; PDR, prolifera-tive diabetic retinopathy; PRP, panretinal photocoagulation.

Diabetic retinopathy photocoagulation 307

The CSME resolved in 218 (91.6%) eyes following focallaser, 102 (42.9%) with initial treatment and 116 (48.7%)with repeated treatment. The average time to resolutionof macular oedema was 3.3

±

1.3 months (range 1.0–8.8months) for eyes that required only one treatment and5.1

±

3.9 months (range 1.0–27.8 months) for the wholegroup (Table 3).

Vision was improved or maintained in 137 (57.6%) eyes.Visual acuity improved by 3 or more Snellen lines in nine(3.8%) eyes and deteriorated by 3 or more Snellen lines in26 (10.9%) eyes (Fig. 1). Moderate visual loss, defined asloss of 3 lines or more in logMAR chart between baselineand last follow up, was observed in 49 (20.6%) eyes. Mod-erate visual loss was higher in patients with severe NPDRand early PDR (27.3%) compared to patients with mild andmoderate NPDR (19.1%), but this difference was not statis-tically significant. A higher proportion of moderate visualloss was also observed in patients without reduction inretinal thickening (30.0%) when compared to patients withreduction in retinal thickening (19.7%) (

P

= ns). Three(1.3%) eyes had visual acuity of less than 6/60 after treat-ment. The baseline visual acuity of these three eyes was6/12, 6/18 and 6/36, respectively.

PRP treatment

Panretinal photocoagulation was performed in 84 eyes, ofwhich 43 (51.2%) required re-treatment. Of the 84 eyesundergoing PRP treatment, three (3.6%) eyes had severeNPDR, three (3.6%) eyes had PDR, 54 (64.3%) eyes hadhigh risk PDR, and 24 (28.6%) eyes had advanced PDR atthe time of treatment. More than half (67.8%) of the eyeshad visual acuity wore than 6/12 at baseline (Table 2).

Neovascularization regressed in 55 eyes (65.5%), 24(28.6%) with initial treatment and 31 (36.9%) with repeatedtreatment. The mean duration from the last session in initialtreatment to the recording of neovascularization regressionwas 6.5

±

5.0 months (range 0.7–23.1 months; Table 3).This was longer in eyes that required re-treatment(7.1

±

5.7 months) when compared to eyes that did not(5.8

±

4.4 months). Eyes with PRP treatment alone had

significantly higher regression rate than eyes with PRP andfocal treatment together (83.8%

vs

51.5%; odds ratio [OR]= 2.2, 95% confidence interval [CI] = 1.3–3.8).

For the purpose of this study, complications were definedas events requiring vitrectomy surgery, development of vit-reous haemorrhage, traction retinal detachment, neovascu-lar glaucoma and phthisis. During the follow-up period,vitrectomy was performed in 12 (14.3%) eyes. Ten (11.9%)eyes developed new vitreous haemorrhage and vitreoushaemorrhage deteriorated in six (7.1%) eyes. Six eyes(7.1%) developed traction retinal detachment, and in one ofthese it was present before laser treatment. Two (2.4%) eyeshad neovascular glaucoma and two (2.4%) eyes hadphthisis.

Figure 1 shows the Snellen visual acuity changes of the84 eyes following PRP treatments (including eyes that hadfocal treatment as well). Vision was improved or maintainedin 52 (61.9%) eyes after the treatment, and deteriorated in32 (38.1%) eyes, including six eyes that lost more than3 lines. Moderate visual loss was found in 20 (23.8%) eyes

Figure 1.

Visual acuity changes following focal (

�

) and pan-retinal (

�

) photocoagulation treatments for diabetic retinopathy.

Table 3.

Retinopathy changes following focal (

n

= 238) and panretinal photocoagulation (

n

= 84) treatments

Retinopathy change No. eyes (%) Time to change (months) Mean Median Range

Reduction in retinal thickening following focal treatmentAfter repeated treatment 102 (42.9) 3.3 3.1 1.0–8.8After initial treatment 116 (48.7) 6.7 5.6 1.4–27.8Total 218 (91.6) 5.1 3.5 1.0–27.8

Neovascularization regression following PRP treatmentAfter initial treatment 24 (28.6) 5.8 4.4 0.7–23.1After repeated treatment 31 (36.9) 7.1 5.7 1.8–20.8Total 55 (65.5) 6.5 5.0 0.7–23.1

PRP, panretinal photocoagulation.

308 Yi

et al

.

and severe visual loss (defined as visual acuity of less than6/60 at last follow up) was observed in four (4.8%) eyes.Vitrectomy or other complications was significantly associ-ated with severe visual loss (17.4%

vs

0%, Fisher’s exact

P

= 0.005). Severe visual loss was significantly higher ineyes that did not achieve neovascularization regression thanin eyes that achieved regression (13.8%

vs

0%, Fisher’s exact

P

= 0.012).Among 37 eyes that had PRP alone, vision was improved

or maintained in 25 (67.6%) eyes and deteriorated in 12(32.4%) eyes following treatment. Moderate visual losswas found in five (13.5%) eyes and severe visual loss wasobserved in two (5.4%) eyes.

D

ISCUSSION

This study provides clinical outcome data following retinalphotocoagulation treatment for diabetic retinopathy. Usingthis same patient series, we have previously reported theapplication of photocoagulation and follow up for diabeticretinopathy at this tertiary referral institution conforms withAustralian clinical practice guidelines.

6

Focal treatment for CSME

In our study, moderate visual loss occurred in 20.6% of eyes,and 1.3% of eyes had visual acuity of less than 6/60 follow-ing focal treatment with a mean follow up of 18 months.These outcomes are similar to those reported in otherstudies.

4,9

The Early Treatment Diabetic Retinopathy Study(ETDRS) reported moderate visual loss at 1 year of 5.3% inpatients having macular oedema with less severe retinopathyand 16.2% in patients having macular oedema with moresevere retinopathy, and 7.6% and 21.1%, respectively, at2 years post-treatment.

9

In a national study in Great Britain,Bailey

et al.

reported that 9.2% of the patients with focaltreatment had moderate visual loss and 3.3% had visualacuity of less than 6/60 at follow-up of 9 months.

4

TheETDRS excluded eyes with baseline visual acuity of lessthan 20/200 (equal to less than 6/60 in Snellen chart).

9

Bailey

et al.

reported that 19% of focal treatments wereperformed on eyes without CSME in their study.

4

Therelatively worse baseline levels of visual acuity and moreadvanced maculopathy in our study population (which mayrelate to suboptimal community screening and late presen-tation) could explain some of the poor visual outcomesfollowing focal treatment. Furthermore, blood glucose,hypertension and lipid measures were not directly assessedin these studies; however, these are important features ofoptimizing diabetes control and are strongly related toretinopathy treatment outcomes.

10–13

Bailey

et al.

found that diffuse maculopathy was an inde-pendent risk factor significantly associated with moderatevisual loss.

4

They identified that the risk of moderate visualloss was 8.5% for eyes with exudative maculopathy, 15.4%for eyes with oedematous maculopathy and 28.9% for eyes

with diffuse oedematous maculopathy. We did not attemptto classify the types of maculopathy in our study subjectsbut the degree of moderate visual loss in our study lieswithin the above range.

Resolution of either focal or diffuse macular oedemafollowing focal laser photocoagulation may take manymonths. Because of this, it is recommended that repeat laserphotocoagulation should not be performed earlier than3 months postoperatively.

14

In our study, 91% of the initialfocal treatments were reviewed within 4 months, which isthe recommended interval in the NHMRC guidelines,

1

andthe average time to thickening reduction was about3.3 months for eyes that required only one treatment, and5.1 months for the group as a whole. In this study, we didnot report information on clearance of hard exudate as therewas a potential of underestimation, perhaps due to insuffi-cient follow-up time of the treated patients. In addition,some of the eyes in our study did not have hard exudate atbaseline (as the diagnosis of CSME does not depend on thepresence of a hard exudate

16

), but may have developed hardexudate as the macular oedema resolved following focaltreatment.

PRP treatment for retinopathy

In our study, 51.2% eyes required re-treatment with PRP,which is more than reported by Kaiser

et al.

(39%).

5

Thisimplies that our initial treatment was inadequate; however,only 4/84 (4.7%) of these eye had less than ETDRS fullscatter initial treatment (1200–1600 burns of 500 microns atthe retina) as reported in our previous study.

6

In addition,our study population seemed to have comparably poorerbaseline retinopathy stages than Kaiser

et al

. Among patientsreceiving PRP, half required focal treatment as well, whereasKaiser

et al.

reported only 10% of their PRP treated eyes alsohad focal treatment.

We found that vision was improved or maintained in61.9% of eyes and decreased in 38.1% of eyes. Causes ofvisual loss in PRP treated eyes included worsening maculo-pathy, vitreous haemorrhage and traction retinal detach-ment; however, it was not possible to collect data regardingthe exact causes of visual loss in all patients in this retrospec-tive audit. After excluding eyes with coexisting CSME fromour analysis, the visual outcome from the 37 eyes under-going PRP alone was slightly worse than a study from Kaiser

et al.

where 80.5% improved or maintained vision and only19.5% deteriorated.

5

This difference may also be partlyexplained by the worse baseline retinopathy severity in ourpatients. Severe visual loss occurred in four (4.8%) eyes inthe present study, which is similar to the DRS study(5.8%)

16

and a British national diabetic retinopathy lasertreatment audit (2.4%).

4

In our study, about 65.5% eyes with PDR achievedregression of neovascularization following PRP, which washigher than findings by Bailey

et al.

(50.8%).

4

For the mostpart, the complication rates in our study are similar to those

Diabetic retinopathy photocoagulation 309

from Bailey

et al.

4

and Kaiser

et al.

5

Our rates of vitreoushaemorrhage were between those reported by Bailey

et al.

and Kaiser et al. but our rates of vitrectomy and tractionalretinal detachment were slightly higher.

It is possible that we can improve visual outcomes andreduce rates of complications further by earlier detectionand prompt treatment of diabetic retinopathy. In addition,achieving better blood glucose control in diabetic patientsshould limit the progression of diabetic retinopathy andimprove visual outcomes following PRP or focal treatment.

Although direct comparison is difficult, the clinical out-comes observed from our study appeared to be similar topublished results from other studies.

REFERENCES

1. National Health and Medical Research Council. Clinical Prac-tice Guidelines for the Management of Diabetic Retinopathy. Canberra:Commonwealth of Australia, 1997.

2. The Diabetic Retinopathy Study Research Group. Indicationsfor photocoagulation treatment of diabetic retinopathy.Diabetic Retinopathy Study Report 14. Int Ophthalmol Clin1987; 27: 239–53.

3. Early Treatment of Diabetic Retinopathy Study ResearchGroup. Photocoagulation for diabetic macular edema. EarlyTreatment of Diabetic Retinopathy Study Report, 4. Int Oph-thalmol Clin 1987; 27: 265–72.

4. Bailey CC, Sparrow JM, Grey RHB, Cheng H. The nationaldiabetic retinopathy laser treatment audit III: clinical out-comes. Eye 1999; 13: 151–9.

5. Kaiser RS, Maguire MG, Grunwald JE et al. One-year out-comes of panretinal photocoagulation in proleferative diabeticretinopathy. Am J Ophthalmol 2000; 129: 178–85.

6. Bamroongsuk P, Yi Q, Harper CA, McCarty DJ. Delivery ofphotocoagulation treatment for diabetic retinopathy at a large

Australian ophthalmic hospital: comparisons with nationalclinical practice guidelines. Clin Experiment Ophthalmol 2002; 30:115–9.

7. Early Treatment Diabetic Retinopathy Study Research Group.Photocoagulation for diabetic macular edema. ETDRS ReportNumber 1. Arch Ophthalmol 1985; 103: 1796–806.

8. Holladay JT. Proper method of calculating average visualacuity. J Refract Surg 1997; 13: 388–91.

9. Early Treatment Diabetic Retinopathy Study Research Group.Early Photocoagulation for diabetic retinopathy. ETDRSReport Number 9. Ophthalmology 1991; 98: 766–85.

10. The Diabetes Control and Complications Trail ResearchGroup. The effect of intensive diabetes treatment on theprogression of diabetic retinopathy in insulin-dependentdiabetes mellitus. N Engl J Med 1993; 329: 977–86.

11. UK Prospective Diabetic Study (UKPDS) Group. Intensiveblood-glucose control with sulphonylureas or insulin com-pared with conventional treatment and risk of complicationsin patients with type 2 diabetes. Lancet 1998; 352: 837–53.

12. UK Prospective Diabetic Study (UKPDS) Group. Tight bloodpressure control and risk of macrovascular and microvascularcomplications in type 2 diabetes. BMJ 1998; 317: 703–13.

13. Early Treatment Diabetic Retinopathy Study Research Group.Association of elevated serum lipid levels with retinal hardexudate in diabetic retinopathy. Arch Ophthalmol 1996; 114:1079–84.

14. Karlin DB, ed. Lasers in Ophthalmic Surgey. Cambridge: BlackwellScience, 1995; 104.

15. Early Treatment Diabetic Retinopathy Study Research Group.Treatment techniques and clinical guidelines for photocoagu-lation of diabetic macular edema. ETDRS Report Number 2.Ophthalmology 1987; 94: 761–74.

16. The Diabetic Retinopathy Study Research Group. Preliminaryreport on effects of photocoagulation therapy. Am J Ophthalmol1976; 81: 383–97.