CATARACT SURGERY AND PROGRESSION OF DIABETIC RETINOPATHY

1. Lumbini Rana-Ambika Eye Hospital, Bhairahawa, Nepal. Address for correspondence : Dr. Sudesh Subedi, MD, Vitreo retinal Surgeon Lumbini Rana-Ambika Eye Hospital P.O. Box: 30, Bhairahawa, Nepal ABSTRACT Patient with diabetes mellitus have a higher prevalence of lens opacity 1 and cataract development at an earlier age than non diabetic.2 Cataract in diabetes mellitus decreases the visual acuity, makes posterior segment evaluation and laser treatment difficult. Several studies have shown that there is progression of diabetic retinopathy after cataract surgery. In all studies, criteria for progression of diabetic retinopathy are: a) progression of any form/type or stage of diabetic eye (DE), nonproliferative diabetic retinopathy (NPDR) or proliferative diabetic retinopathy (PDR) to any advanced, recurrent form/ type or stage of NPDR or PDR and b) development of new clinically significant macular edema (CSME) and/or worsening/ recurrent of preexisting CSME defined by Early Treatment Diabetic Retinopathy Study (ETDRS).


CATARACT SURGERY AND DIABETIC RETINOPATHY
Various reports indicates that DR worsens after cataract surgery 3,9 but Sebestyen 10 found concurrent progression in the other eye also -Similar reports, after prospective study 11 on 205 eyes concluded that worsening of DR seems to be correlated with the natural course of the vascular disease.This study included the cases without preoperative diabetic retinopathy, untreated bilateral diabetic retinopathy and more advanced retinopathy with laser treatment.

TYPES OF CATARACT SURGERY
Now there is rapid progression on cataract from ICCE to manual phaco(SICS) and phacoemulsification.In the same way, the IOL technology also progressed from ordinary IOL to heparin coated lOLs which causes less post operative inflammation.
The ICCE and ECCE requires a large incision more trauma during nucleus delivery and more damage to blood retinal barrier in comparison to Phaco, which are responsible for more significant post operative inflammation and progressed diabetic retinopathy as well as decreased visual acuity.
Several studies had been done to show relationship between different surgical technique and progression of diabetic retinopathy which concluded that progression of DR is more in ICCE than ECCE with IOL 4,12 and SICS and Phaco. 13ogression of DR increased with complicated cataract surgery (PCR, vitreous loss) 4,13 and prolonged surgery 13 etc.

GLYCEMIC CONTROL BEFORE CATARACT SURGERY
Various reports showed high risk factor for progression of DR is preoperative hyperglycemic (Increased glycelated hemoglobin level) condition. 14,15,16

PREEXISTING DIABETIC RETINOPATHY AND CATARACT SURGERY
Most of the studies showed progression in DR after cataract surgery in preexisting DR.In more severe preoperative DR, much worse DR was found post operatively. 3,4,5,14,15,17,18

MINIMUM PERIODS OF FOLLOW UP
There are several prospective 5,11,17 and retrospective 10,13,15 studies in which the first 6 month was determined as a minimum period of follow up : at weekly or fortnigatly for first 3 month and 4 weekly for the next 3 month.

CYSTOID MACULAR EDEMA
Cystoid macular edema (CME) is most common after cataract extraction in diabetic patients than in nondiabetic patients 19,20 due to synergistic effects (which is described below) and more severe CME in eyes with DR changes than those of with out DR changes. 19,21,22

Age and duration of Diabetes Mellitus
DR increases with age and duration of DM. 23,24 In IDDM the progression of DR was much more than NIDDM, 4,6,16,23,25 where as it was just reverse in another study. 17

Sex
In female the progression of DR was more significant than male Jaffe & Burton. 3,17

Local Factors
Local factors which might accounts for the sudden vasculopathetic deterioration after cataract extraction are c) Reduced secretion of vaso inhibitory substances d) Increased synthesis of the endothelium that functions as an angiogenic agent within the iris stroma.

Nature of Diabetic Eyes
In diabetic eyes the anterior segment is also affected e.g.bigger lens, steeper anterior lens curvature, more pronounced miosis, more permeable iris vessels and diabetic vasculopathy etc which collectively causes more traumatized cataract surgery and increased postoperative inflammation.
Hence the local factors and the nature of the diabetic eye synergistically affect the progression of maculopathy and diabetic retinopathy. 5As mentioned in a retrospective study, 26 that visual outcome of cataract surgery in diabetics is largely determined by the degree of maculopathy.Phaco and ECCE give similar visual results.
Other nonsurgical inflammations like sarcoid uvietis, HIV infection, endophthalmitis 27,28 etc. play an important role in the progression of DR.

Systemic Factors
There are several systemic conditions / diseases 25 like hypertension, elevated cholestecol and triglycerides, renal diseases, cardiovascular diseases, which might affect the course of DR.Such cases were also included in various studies. 3,5,13,14,26,30. Hericson et.al. 14 and Robert N Johnson et.al. 30 mentioned no significant difference in progression of DR.The reports of United Kingdom Prospective Diabetic study (UKPDS) 31 accord with previous observational studies in type I, diabetes 32,33 and demonstrate both hypertension as a risk factor for DR and beneficial effect of tight blood pressure control.In type I and II diabetes target blood pressure should be ?130/80 mmHg.The presence of high-normal blood pressure resulted in a prospectively higher occurrence of retinopathy and of progression of preexisting retinopathy. 34ere was a significant trend for increasing severity of DR and retinal hard exudates with increasing cholesterol in IDDM. 35Glycalated hemoglobin and diastolic blood pressure were significant descriptors of the severity of retinopathy in younger-onsetpatients.Weber et.al. 36 found a positive relationship for triglyceride but not for cholesterol.

SUMMARY AND RECOMMENDATIONS
Most of the studies were done in small number of samples and majority of them showed progression of DR after cataract surgery.It also showed an important role of other risk factors in progression of DR.
But still there are some debatable and unanswered questions in which future study, done in large number of samples, can give more reliable answers.Some of the important debatable questions are: 1.What is the cause of progression of DR after cataract extraction?Is it natural course of the diabetic vascular disease or cataract extraction itself or a combination of these factors?2. Role of strict control of blood pressure and blood sugar etc. in prevention of progression of DR (before and after cataract surgery).Only few studies 30,14 have mentioned about non significant progression of DR with controlled Hypertension.3. Sex distribution: Only Jaffe and Burton 3,17 have shown that women are more at risk for progression of DR after cataract surgery than men.
absence of an angiogenic inhibitory factor which is present in the lens.b) Postoperative intraocular inflammation mediated by leukotrienos.

RISK FACTOR The other risk factors for the progression of diabetic retinopathy are:
Nondiabetic patients were also included in several studies as a control for comparison of visual outcome with diabetic patients without DR and with DR changes after cataract extraction.It shows similar visual outcome in non diabetic patient and diabetic patient without DR changes eyes.
It is better to postpone cataract surgery as late as possible till the patient demands clear vision or surgeon have difficulty in fundus examination or laser treatment due to cataract.2. If laser is indicated it is better to perform this treatment before cataract surgery and if it is not possible, do laser after cataract extraction.3. Preoperative good control of blood sugar (glycelated hemoglobin level) and hypertension (? 130/80 mm of Hg) is necessary.4. It is better to perform cataract surgery by an experienced surgeon. 5. Regular follow up after cataract surgery to evaluate progression of DR and for early laser treatment if indicated.