INTRODUCTION

India is regarded as ‘the diabetic capital of the world’. According to International Diabetic Federation, prevalence of diabetes is estimated to be 69.1 million in India in 2015.The burden of diabetes is increasing year by year and it is projected to increase to approximately 79.4 million individuals by 2030¹. Diabetes mellitus causes micro vascular complications due to micro angiopathy, but are not necessarily directly linked to the level of hyperglycemia. Diabetes affects the eye in various forms. Cataract is frequently associated with diabetes along with glaucoma and diabetic retinopathy². 

Diabetes and cataract

As the incidence and progression of cataract is elevated in patients with diabetes mellitus, cataract is considered as the major cause of visual impairment in diabetics³. Patients with diabetes tend to develop cataract at a younger age compared to that of non-diabetics.

Hyperglycemia will be reflected as high level of glucose in aqueous humor, which diffuses into the lens. Normally the hexokinase pathway is used for the metabolism in the lens. But if blood glucose level exceeds 200mg%, the hexokinase gets saturated and aldose reductase convert the glucose into sorbitol⁴. Sorbitol is metabolized slowly by the lens. So, it gets accumulated in the lens cytoplasm. . Osmotic pressure inside the lens slowly increases, causing influx of water and swelling of lens fibres and this ultimately leads to the formation of lens opacities^{5, 6}.

Further studies revealed that osmotic stress in the lens produced by the sorbitol accumulation causes induction of apoptosis in the lens epithelial cells, which finally results in the development of cataract⁷. Also, hyperglycemia puts the antioxidant pathways into stress and along with the glycosylation of proteins, which results in abnormal cross linkage and aggregation, producing cataract⁸.

Diabetic retinopathy

Diabetic retinopathy is a frequent complication of  both type1 and type 2 diabetes and is one of the main causes of visual disability in patients with diabetes⁹. After 20 years of the disease, 95% of type 1 patients and 60% of type2 patients will show signs of retinopathy⁵. The risk of developing diabetic retinopathy is according to the type and duration of diabetes, blood pressure and the level of glucose and lipids in the blood¹⁰.Diabetic retinopathy is a microangiopathy of the retina which first presents with the appearance of retinal micro aneurysms preferentially at the posterior pole of the retina¹¹. It is believed that exposure to hyperglycemia over an extended period result in a number of biochemical and physiologic changes that ultimately cause endothelial damage. Specific retinal capillary changes include selective loss of pericytes and basement membrane thickening, which favor capillary occlusion and retinal non perfusion, as well as decompensation of the endothelial barrier function, which allows serum leakage and retinal edema to occur.

Diabetic retinopathy is classified into NPDR (Non Proliferative Diabetic Retinopathy) which is the background retinopathy and PDR (Proliferative Diabetic Retinopathy) which presents with neovascularization due to retinal ischemia.

Diabetic macular edema is an important manifestation of diabetes causing visual impairment. Diabetic retinopathy patients elevated VEGF levels in vitreous and retina ,which causes breakdown of blood – retinal barrier leading to the accumulation of fluid in the macula¹².

Diabetic retinopathy and cataract surgery

Because of the high correlation between the duration of diabetes and its complications¹³, older patients who are more likely to have cataract may also have diabetic retinopathy or macular edema. Earlier cataract surgery is important as the lens opacities may preclude the fundus details⁵. But, usually diabetic cataract extraction has been associated with higher post-operative complications than non-diabetics which include progression of diabetic retinopathy, worsening of macular edema, anterior segment neovascularization, posterior capsular thickening and fibrinous uveitis^14-16 which result in poor visual acuity post operatively.

The progression of diabetic retinopathy and macular edema worsening are considered to be due to breakdown of blood retinal barrier or due to the inflammatory mediators released after surgical trauma¹⁷. Compared to ICCE and ECCE, phacoemulsification is suggested to be safer to perform in diabetics as it is associated with lesser post-operative inflammation¹⁸. Thus a study on progression of diabetic retinopathy following uncomplicated phacoemulsification stands relevant.

REVIEW OF LITERATURE

Cataract surgery in diabetic retinopathy patients is a common scenario for ophthalmologists to manage now-a-days. Definitive treatments of both the conditions are essential for a better visual prognosis for the patient. Diabetic retinopathy often results in poor visual acuity following cataract surgery than in patients without retinopathy. Earlier in the 90s, Jaffe²³ and Schatz et al. ²⁷found out that retinopathy progression is more in the operated eye compared with the fellow control eye. In a follow up study of 21 patients with symmetric NPDR who underwent ECCE and IOL for 18+/- 7 months by Jaffe et al.²³to determine the incidence and factors predictive of progression of diabetic retinopathy and the final visual acuity, 74% had progression of retinopathy. In 37% it progressed only in the operated eye whereas, no patients had progression in the fellow eye alone. In Schatz et al. study, twenty-three (72%) of the 32 study patients had asymmetric retinopathy (with the more severe retinopathy in the eye that underwent cataract surgery in each case) compared with three (9%) of the control group (P < .0005).the visual acuity results were poorer in eyes undergone cataract surgery with no eye achieving 20/20 or 20/2, only 3 eyes achieved 20/30 or 20/40.

Worsening macular oedema, continuing anterior and posterior segment proliferation, posterior capsule opacification, or unrelated events, such as retinal vein occlusion may be the cause of worsening of visual results. Posterior capsular opacification also found to be more in diabetics with retinopathy than in non-diabetics.

Kwon SI ²² and colleagues conducted a retrospective study on macular thickness changes after cataract surgery in 104 diabetic patients in Korea, using optical coherence tomography (OCT) done at 1week, 2 weeks and 6 weeks after the surgery. Study revealed that 18% patients had macular edema after cataract surgery, which had a peak incidence of 1 month post-surgery. They concluded that prior laser treatment might prevent post-operative macular edema until 2 months after cataract surgery in diabetic patients.

Various factors have been put forwarded as the cause of worsening of retinopathy. A study was conducted by Henricsson et al.²¹ in the department of ophthalmology in Helsingborg, UK including 70 patients with 35 mono ocularly and 35 binocularly operated on ( ECCE, SICS, phaco) followed up for 32 months, revealed the importance of good glycemic control in preventing the progression of retinopathy. Patients in this study including those with PDR obtained good visual acuity, better than in most of the previous studies. Mean level of HbAlC (p=0.04), duration of diabetes (p=0.02), insulin treatment (p=0.001), and presence of retinopathy at baseline (p=0.01) were the factors associated with the progression of retinopathy, which occurred in 30 among the 70 operated eyes.

Benson et al.²⁵ found that age was an important predictor of poor visual outcome. Patients aged 63 or less were more likely to achieve increase in visual acuity after cataract surgery. Poorer results in older patients were due to worsening of macular edema.

Various studies compared different surgical techniques of cataract in terms of post-operative results. A prospective study done by Dowler et al.²⁶ with 46 patients having diabetes and bilateral cataract to compare phacoemulsification with ECCE, revealed that phacoemulsification is associated with better post-operative visual acuity, less post-operative inflammation and less need for capsulotomy. But, there was no difference in incidence of post-operative CSME or progression of retinopathy or development of high risk retinopathy was identified between the two techniques.

Borrillo et al.²⁴ have done a retrospective review of 150 eyes of 119 diabetic patients who underwent phacoemulsification over 5 year period and the visual results and rate of progression of diabetic retinopathy after phacoemulsification were not much different from those reported using other techniques. The study proposed that pre-operative NPDR, prolonged surgical duration and limited surgical experience were statistically associated with retinopathy progression.

In a retrospective study conducted by Shuh-Bin Liao and colleague to analyze the progression of diabetic retinopathy following uncomplicated phaco emulsification with 3 years follow up, which included 37 diabetic patients with binocular surgery done in 14 patients and monocular surgery done in 23 revealed that patients who had mild to moderate NPDR pre-operatively had significantly greater progression of retinopathy post operatively compared to those without pre- operative NPDR. But, they couldn’t find any significant difference between the operated eyes and non-operated eyes in the progression of retinopathy¹⁹. Of 51 operated eyes, 33 (64.7%) achieved an uncorrected visual acuity of 20/40 at 1 year postoperatively, and 47 (92.1%) had improvement of visual acuity of more than two lines.

In a prospective trial study of 50 type 2 diabetes mellitus patients undergoing mono ocular phacoemulsification by Squirrell et al²⁰, to assess the grade of diabetic retinopathy and diabetic maculopathy in the operated eye and fellow eye pre operatively and 12 months post operatively concluded that un complicated phaco emulsification cataract surgery does not cause acceleration of diabetic retinopathy post operatively and any progression that is observed probably represents the natural history of the disease. Wagner et al.²⁸ study also revealed the same results.

There is still no definite data regarding whether phacoemulsification will lead to progression of diabetic retinopathy or not. Contradictory results have been obtained in this regard. Not many studies are conducted in Indian population where diabetes prevalence is very high. Thus a follow up study on progression of diabetic retinopathy following uncomplicated phacoemulsification with adequate sample size in Indian setting stands relevant.

AIMS AND OBJECTIVES

AIM :

To study the progression of diabetic retinopathy in uncomplicated phacoemulsification with a follow up of 6 months.

OBJECTIVES:

1. To assess the new development of retinopathy post-operatively

2. To study the post-operative progression of stage of diabetic retinopathy

3. To assess the post-operative worsening of macular edema

4. To determine the post-operative visual acuity

MATERIAL AND METHODS

STUDY AREA- Giridhar Eye Institute, Cochin.

STUDY POPULATION- Patients with diabetes undergoing phacoemulsification surgery in Giridhar eye institute, Kochi.

Inclusion Criteria:  The patients with established or no diabetic retinopathy in a known case of diabetes mellitus undergoing cataract surgery by phacoemulsification, with no intraoperative complications are included.

Exclusion criteria:  patients with co-existing other retinal pathology, previous intraocular surgeries or inflammation, complications during phacoemulsification procedure.

STUDY DESIGN- Prospective study

SAMPLE SIZE- 330 participants

STUDY DURATION- One and a half years (From January 2017 to June 2018)

METHODOLOGY

Pre-operative evaluation: Visual acuity, anterior segment examination, intra ocular pressure, 78 D examination, indirect ophthalmoscopy and colour fundus photography will be done. Optical Coherence Tomography (OCT) will be done if clinical evaluation is suggestive of macular edema or diabetic retinopathy. Fundus Fluorescein Angiography(FFA) will be done if there is evidence of diffuse macular edema/ severe NPDR/ PDR or prior to starting laser photocoagulation.

Post-surgery evaluation: Retinal examination will be done at 3 weeks, 3 months and 6 months.

Evaluation at each visit: Visual acuity, Anterior segment examination, intra ocular pressure, slit lamp examination by biomicroscopy, indirect ophthalmoscopy and colour fundus photography will be performed. Optical Coherence Tomography (OCT) will be done if clinical evaluation is suggestive of macular edema or diabetic retinopathy. Fundus Fluorescein Angiography (FFA) will be done if there is evidence of diffuse macular edema/ severe NPDR /PDR or prior to starting laser photocoagulation.

The treatment will be decided based on the tests.

The staging of the diabetic retinopathy and diabetic maculopathy will be done based on ETDRS classification. If OCT is taken, centre sparing or centre – involving macular edema will be noted.

The primary outcome measures are new development of retinopathy, progression of stage of diabetic retinopathy or worsening of macular edema based on OCT tests. The secondary outcome measure is post -operative visual acuity.

STATISTICAL METHODS

Descriptive analysis will be carried out using SPSS 16  version. Continuous variables will be expressed in terms of mean and standard deviation. Categorical variables will be expressed in terms of percentage and frequency. Further statistical test to be done will be based on the data obtained.

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