Cataracts are clouding of the lens and can be classified as cortical cataracts, nuclear cataracts and subcapsular cataracts depending on the site where the clouding occurs. Generally speaking, subcapsular cataract occurs mostly in the pupillary area, which has a greater impact on vision and will cause visual impairment earlier, while cortical cataract and nuclear cataract will cause visual impairment relatively later.
I. Special characteristics of cataracts in diabetic patients The cataracts suffered by diabetic patients belong to metabolic cataracts, and there are two states. One is true diabetic cataract (belonging to metabolic cataract). This is a cataract formation due to biochemical abnormalities in the internal environment after diabetes. This type of cataract is relatively rare and has the highest incidence in young and middle-aged diabetic patients, and is also common in juvenile diabetic patients. True diabetic cataract begins with the formation of small subcapsular vacuoles in the dense anterior capsule of the lens. As the disease progresses, the small vacuoles can rapidly develop into the typical gray-white patchy clouding located in the superficial layers of the anterior and posterior subcapsular cortex. After that, the patchy cloudiness expands and is evenly distributed in the cortical layer, like snowflakes floating in the gray sky, which is called “snowflake-like cloudiness”. This is called “snowflake-like clouding” and later progresses to a full blown cloudy state.
Another state is similar to age-related cataracts. For cataracts that occur in diabetic patients after middle age, it is difficult to distinguish accurately between diabetic and geriatric factors. However, cataracts caused by diabetes mellitus have all the morphologic features of senile cataracts, and there is much evidence to support the phenomenon that diabetic factors can cause senile cataracts to appear earlier or to progress faster.
The characteristic pathological change in the development of cataracts in diabetic patients is the rapid onset of high edema of the lens stroma and the massive formation of aqueous gaps, with the result that the lens swells and enlarges. Thus, a rapid increase in blood glucose can lead to significant myopia, whereas if the blood glucose is rapidly reduced to normal, farsightedness can result. These changes can be completed in a few days, but it takes several weeks to return to normal refractive status.
Compared with normal cataract patients, diabetic patients with cataracts not only affect their normal life with vision loss and make their quality of life decrease, but more importantly, the refractive interstitial clouding affects the doctor’s observation of the patient’s fundus, which may lead to the omission of fundus lesions and also delay the laser treatment of fundus lesions, bringing irreparable visual damage to the patients.
Treatment of cataracts in diabetic patients The means of treatment are basically the same regardless of the type of cataract. For patients who also have diabetes, the development of cataract is greatly related to the level of blood sugar, so controlling blood sugar is especially important, especially for true diabetic cataract.
In the early stage of cataract, when there is no visual impairment and it does not affect the observation of the fundus, special treatment is generally not required. At present, there are many anti-cataract drugs sold at home and abroad. Although these drugs theoretically try to treat the disease in terms of preventing abnormal metabolism and protein degeneration of the lens, there is no precise and simple scientific quantitative detection method and comparison of lens clouding changes, but only judging from the patient’s subjective feeling and vision changes, so there is no definite evaluation of efficacy.
Surgery is the most effective means of cataract treatment. For diabetic cataract patients, the purpose of surgery is twofold: one is to restore vision and improve quality of life, and the other is to facilitate the observation and treatment of fundus lesions. In diabetic patients, vision impairment caused solely by cataract can be substantially improved with successful surgical treatment, and the timing of surgery can be chosen with ease. In contrast, visual impairment caused by diabetic retinopathy is to some extent irreversible and can have serious consequences if the best time for treatment is missed. Therefore, the choice of cataract surgery timing for diabetic patients should first consider whether it is convenient for the treatment of fundus disease. Therefore, for some patients whose central vision is still good and the peripheral part of the lens or the posterior subcapsular cortex clouding has already affected the laser treatment of diabetic retinopathy, even if the cataract is not serious, timely surgery should be considered. In particular, it should be emphasized that if laser treatment is required for diabetic retinopathy, laser retinal photocoagulation should be completed as fully as possible before cataract surgery, and areas of insufficient photocoagulation should be supplemented as soon as the incision heals after surgery. For those whose laser treatment is affected by cataract before surgery, retinal photocoagulation should be completed as soon as possible after surgery.
III. Some issues about cataract surgery 1. Preparation before surgery: including two aspects of eye preparation and whole body preparation. First of all, the eye preparation includes detailed eye examination and auxiliary examination, and a comprehensive understanding of the outer eye and ocular surface of the operated eye, the characteristics of lens clouding and the degree of nuclear sclerosis, and whether there are other eye diseases affecting visual function. In addition, a thorough assessment of the possible problems encountered during surgery and the possibility of recovery of vision after surgery should be made to prepare the patient psychologically and physically. Secondly, topical antibiotics and corticosteroids or NSAIDs should be applied 1-3 days prior to surgery, and NSAIDs can also be given orally 3 days prior to surgery as appropriate, which helps to cleanse the conjunctival sac and prevent postoperative intraocular infectious or non-infectious inflammation, as well as to maintain pupil dilation during surgery. In patients with combined diabetic retinopathy, preoperative determination of the need for retinal photocoagulation should be based on the degree of lens clouding and whether fundus angiography should be performed.
In addition to the systemic condition of the heart, brain, liver and kidney, as in non-diabetic cataract patients, special attention should be paid to the change of blood sugar. Poor blood glucose control not only increases the risk of surgery, but also increases the incidence of postoperative complications. The standard of control is generally: fasting blood sugar ≤ 8.3mmol/L, glycosylated hemoglobin ≤ 11%.
2. Choice of surgical method: Simple cataract, like other cataract surgeries, can be performed by ultrasonic emulsification intracameral aspiration combined with IOL implantation or cataract extracapsular extraction combined with IOL implantation. Because of the advantages of small incision and mild postoperative reaction, ultrasonic cataract surgery should be preferred in hospitals that have the conditions. For patients with proliferative retinopathy requiring vitrectomy, the decision to combine or stage the procedure should be made on a case-by-case basis.
Whether to implant an IOL in a patient depends on the specifics of the patient’s ocular complications. Most people believe that proliferative diabetic retinopathy should not be a contraindication to IOL implantation, but the following cases are indeed contraindicated: severe proliferative diabetic retinopathy with extensive traction retinal detachment; iris neovascularization; neovascular glaucoma.
3, how to choose an IOL for diabetic patients: the choice of IOL for diabetic patients should take into account whether the patient is combined with diabetic retinopathy and other ocular complications. Because anterior chamber IOLs affect fundus examination and may cause anterior chamber angle damage and aggravate iris neovascularization, so many doctors have not recommended the use of patients. In order to facilitate postoperative fundus observation and laser treatment in diabetic patients, many publications have recommended the implantation of large diameter (6.5mm-7mm) IOLs in the past. Most of the folding IOLs currently in clinical use have an optical diameter of 6 mm, which basically meets the needs of postoperative fundus observation and laser treatment. As far as IOL materials are concerned, there are many types on the market today. Most IOLs are available, except for silicone gel IOLs, which are not suitable for patients with combined diabetic retinopathy who may require vitrectomy and silicone oil filling. Heparin surface-treated IOLs have the advantage of reducing ocular inflammation and may be the preferred choice. In addition, the use of multifocal IOLs is not recommended for patients who require retinal laser photocoagulation after surgery.
4. Postoperative precautions: Diabetic patients have relatively heavy reactions after cataract surgery, which may cause anterior chamber fiber exudation and iris adhesions, or even IOL iris entrapment. Since diabetic patients are special in terms of medication, it is especially important to use reasonable medication after surgery. Our practice is to use glucocorticoids and nonsteroidal anti-inflammatory drugs to punctuate the eye for 1 month and to use short-acting dilators to move the pupil as appropriate. Since some glucocorticoid eye solutions can cause an increase in intraocular pressure, changes in intraocular pressure in the operated eye should be detected during the medication period and the medication should be adjusted in a timely manner.
Postoperative observation of the fundus is also very important. Health care providers should do a good job of educating patients and emphasize the importance of regular fundus examination in diabetic patients. If the condition requires, fundus fluorescence angiography is feasible 2 weeks after surgery, and fundus laser treatment is feasible 1 month after surgery.
Posterior capsule lens epithelial hyperplasia may occur after any cataract surgery, causing a decrease in the clarity of the refractive interstitium, leading to a decrease in the patient’s visual acuity and affecting fundus observation. At this time, YAG laser posterior capsulotomy or surgical posterior capsulotomy may be performed as appropriate.
There are different reports on whether the progression of diabetic retinopathy will be aggravated after IOL implantation in diabetic patients, but some studies have shown that the progression of retinopathy after cataract surgery is closely related to the status of glycemic control at the time of surgery.