Year : 1996 | Volume
: 44 | Issue : 3 | Page : 145--148
Risk factors influencing the treatment outcome in diabetic macular oedema
Amod Gupta, Vishali Gupta, MR Dogra, SS Pandav
Postgraduate Institute of Medical Education and Research, Chandigarh, India
Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh 160 012
A multivariate analysis was done on 96 eyes to evaluate the effect of various risk factors on the final visual outcome after laser photocoagulation for clinically significant macular oedema (CSME) in diabetic retinopathy. Advanced age of the patient, large size of CSME and poor baseline visual acuity were found to be significantly associated with poorer outcome (p<0.05). The association of nephropathy and hypertension with poorer visual outcome was of boderline significance (p = 0.054 and 0.07, respectively). Wavelength of the laser (argon or krypton) used for treatment did not significantly influence the outcome.
|How to cite this article:|
Gupta A, Gupta V, Dogra M R, Pandav S S. Risk factors influencing the treatment outcome in diabetic macular oedema.Indian J Ophthalmol 1996;44:145-148
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Gupta A, Gupta V, Dogra M R, Pandav S S. Risk factors influencing the treatment outcome in diabetic macular oedema. Indian J Ophthalmol [serial online] 1996 [cited 2020 Oct 22 ];44:145-148
Available from: https://www.ijo.in/text.asp?1996/44/3/145/24574
Diabetic macular oedema is the most common cause of moderate visual loss in diabetic patients. Early Treatment Diabetic Retinopathy Study (ETDRS) research group has demonstrated that focal laser photocoagulation of clinically significant macular oedema (CSME) could reduce the risk of visual loss by 50%. The pathogenesis of diabetic macular oedema is multifactorial. Various potential risk factors include hypertension, proteinuria, duration of diabetes,3 use of insulin, cardiac and renal failure and panretinal photocoagulation. The influence of these and various other risk factors including age, sex, type of diabetes, size of CSME, involvement of the foveal centre, type of treatment (focal versus grid), repeat treatment and the laser wavelength used, for laser photocoagulation of macular oedema is still not clear. We performed a multivariate analysis to determine the effect of these factors on final visual results after focal or grid laser treatment of CSME.
MATERIALS AND METHODS
We reviewed the hospital records of 96 patients (96 eyes) that had undergone laser photocoagulation (focal or grid) for diabetic macular oedema between March, 1991 and April, 1993. One eye was chosen randomly from patients in which both eyes were treated in order to satisfy the assumption of independence among eyes for statistical analysis.
1. Availability of complete patient profile including the age, sex, type of diabetes, insulin usage and presence or absence of associated systemic diseases like hypertension, cardiac disease, diabetic nephropathy and neuropathy.
2. Record of best corrected visual acuity at pre laser and post laser visit at the end of 12 months.
3. Fundus photograph or fundus drawings clearly depicting the size, extent and location of CSME before laser treatment and at twevle months follow up.
4. Details of treatment including the type of treatment (focal versus grid), the wavelength used (argon green versus krypton red), repeat treatment if any, associated pan retinal photocoagulation (PRP) for pre-proliferative diabetic retinopathy (PPDR) or proliferative diabetic retinopathy (PDR) without any high risk characteristics (HRC).
5. A minimum follow up of 12 months after laser treatment.
1. Proliferative retinopathy with high risk characteristics as defined by the diabetic retinopathy study group.
2. Cystoid macular oedema (CME)
3. Macular ischaemia
Eyes with high risk characteristics were excluded because co-existent vitreous haemorrhage or pre-retinal bleed in these eyes are likely to cause decrease in visual acuity. The eyes with CME and macular ischaemia were excluded from the study because both these factors are known to be associated with poor prognosis.,
Ninety-six eyes included in the study were divided into two groups on the basis of final treatment outcome at the end of 12 months follow-up. The eyes with successful outcome were placed in group I, while group II included those with poor outcome. The criteria for grouping were as below:
Group I (Successful outcome): This group included eyes which fulfilled the following criteria:
1. Post laser visual acuity of 6/6 or better.
2. Post laser visual acuity of 6/9-6/18 which have shown more than 2 lines improvement on Snellen chart from their baseline pre laser visual acuity.
3. Regression of CSME if associated with criteria number 1 or 2 or with stablization of visual acuity i.e. post laser visual acuity within 2 lines of the pre laser visual acuity provided final visual acuity was 6/18 or better.
Group II: (Poor Outcome): This group included eyes with the following criteria:
1. Post laser visual acuity of 6/24 or less.
2. Post laser visual acuity of 6/9-6/18 which have shown >2 line deterioration on Snellen chart from the baseline pre laser visual acuity.
3. Persistence of CSME if associated with criteria number 1 or 2 or with a post laser visual acuity of 6/9 or less.
A number of prelaser baseline variables were chosen for analysis. All the patient variables including age, sex, type of diabetes, use of insulin, associated systemic diseases (i.e. hypertension, cardiac disease, diabeteic nephropathy and neuropathy), were recorded from the data available. Best corrected pre and post laser visual acuity and various treatment parameters including the type of treatment (focal versus grid), wavelength used (argon green versus krypton red) and repeat treatment done were also recorded. History of associated PRP if done for PPDR or PDR without high risk characteristics was recorded if it was done within three months of laser photocoagulation for CSME. Size of CSME was recorded from the fundus drawings or by projecting the pre laser color fundus photographs if available. The size of CSME was measured and expressed in the disc diameters by using the horizontal diameter of the optic disc (1500 um) as a size reference. Involvement of the foveal centre was also recorded similarly and was expressed as whether the centre was involved or not.
The data was analysed in two phases. In the first phase of analysis, the variables were subjected to Bartlett chi square test for homogeneity of group variance. Variables found significant (p<0.05) in the first phase were further analysed in the second phase by using multivariate logistic regression model (SPSS software).
There were 96 patients (96 eyes) who fulfilled the study criteria, 47 eyes were included in group I and 49 eyes in group II. The baseline characteristics of the patients were determined in each group [Table:1]. There was no significant difference in the gender distribution between the two groups. The distribution of a number of these variables in each group was determined [Table:1]. The variables were subjected to Bartlett chi square test for homogeneity of group variance in phase 1 of the analysis and the variables found to be statistically significant (p<0.05) were age of the patient, systemic hypertension, nephropathy, pre laser visual acuity and size of CSME [Table:2]. These five variables were further analysed in the second phase by using multivariate logistic regression model (SPSS software) [Table:3].
In the final multivariate model, the variables significant at p < 0.05 for poor outcome were age of the patient, pre laser visual acuity and size of CSME. The association of the presence of hypertension or nephropathy with poor outcome had boderline statistical significance. Tests for linear trend were also calculated with data stratified for baseline pre laser visual acuity, size of CSME and age of patient. These trends revealed that decreasing baseline visual acuity, advancing age and increasing size of CSME were associated with poorer treatment outcome.
The results of this analysis highlight the importance of older age, poor pre laser visual acuity and large size of macular oedema with respect to poorer visual outcome following laser photocoagulation for CSME in diabetics.
A number of studies have shown that good baseline pre laser visual acuity is a good prognostic factor.,, In our study also beneficial effect of treatment was demonstrated for the eyes with good initial visual acuity. Olk, however, in two of his studies, has documented that pre laser visual acuity could not statistically affect the visual outcome. He has also shown that presence of associated systemic hypertension and vascular disease did not statistically affect the visual outcome in these eyes. In our study, hypertension and nephropathy had boderline significance as poor prognostic factors.
Regarding the size of CSME, there are reports of diffuse macular oedema treated with grid treatment associated with poor visual prognosis., Linear trend for CSME has shown that prognosis for good post laser visual acuity and regression of CSME worsens as the size of CSME increases. Similarly, advancing age of the patient was also associated with poor treatment outcome.
It was also observed that involvement of the foveal centre by macular oedema was not a poor prognostic factor by itself unless centre involvement was associated with poor pre laser visual acuity. The prognosis was worse for the eyes which had poor prelaser visual acuity.
There have been conflicting reports in literature regarding the role of argon green and krypton red wavelengths for treating diabetic macular oedema. Marshall and Siegelman favour the use of krypton red laser to treat diabetic maculopathy. McDonald and Schatz, on the other hand, found argon green to be more effective than krypton red in the grid treatment of diffuse maculopathy. Olk and Cruess, however, found the results of both krypton red and argon green comparable while treating macular oedema. The results of our study show that both these wavelengths are equally effective in causing, a) regression of macular oedema b) improvement/stablization of visual acuity at the end of 12 months followup with no statistically significant difference (p > 0.05) between the two wavelengths. However, we made one important observation while examining these eyes on their followup visit that the scars caused by krypton red were more discrete, less pigmented and showed less post laser extension into the fovea as compared to those of argon green.
Contrary to the popular belief that panretinal photocogulation (PRP) is associated with worsening of macular oedema, we found that PRP done for coexistent PDR (which did not have vitreous hemorrhage or pre retinal bleed) and PPDR did not lead to worsening of the treatment outcome.
In conclusion, older age of the patient, increasing size of CSME, poor pre laser visual acuity were associated with poor prognosis. Involvement of the foveal centre was not an independent poor prognostic sign unless associated with poor baseline visual acuity. The results of our study suggest that diabetic maculopathy should be treated early when the visual acuity is normal or near normal and the size of CSME is still small provided it meets the diagnostic criteria of ETDRS. Furthermore, this study also suggest that the availability of a particular wavelength for photocoagulation of diabetic macular oedema does not compromise the quality of care and thus, krypton red can be used with efficacy equal to the standard argon green, in eyes with cataract and media opacities.
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