Question posed to me:
My 87-year old mother in law had a torrid time post bilateral cataract surgery. She ended up with stromal folds and oedema. Vision 6/36 and 6/24. She also developed macular oedema in the right eye and ERM (epiretinal membrane) in the left eye. I have always been surrounded by friends and family who had fantastic outcomes with intra-ocular lenses, but then this happened. Could you shed some light on the matter?
Facts to look at first:
Age: 87-year old female
- Many elderly people have ocular and systemic co-morbidities. In a UK National Cataract Surgery Survey, one in three participants had a pre-existing ocular condition that could significantly affect cataract surgery outcomes. In that study, AMD was present in 15% of the participants, glaucoma in 10%, and diabetic retinopathy in 3%. The prevalence of these conditions, as expected, increases with age.
- This patient most probably had a mature and hard cataract requiring more phaco power, which will lead to corneal oedema and stromal folds.
- Older patients also have lower endothelial cell count. Which if stressed by mature cataract, higher phaco power and longer theatre time, could also lead to corneal oedema and stromal folds.
Corneal oedema and Stromal folds
The endothelium is the thin, innermost layer of the cornea. Endothelial cells are important in keeping the cornea clear. Normally, fluid leaks slowly from inside the eye into the stroma. The endothelium’s primary task is to pump this excess fluid out of the stroma. Without this pumping action, the stroma would swell with water and become thick and opaque.
In a healthy eye, a perfect balance is maintained between the fluid moving into the cornea and the fluid pumping out of the cornea. Unlike the cells in Descemet’s membrane, endothelial cells, destroyed by disease or trauma are not repaired or replaced by the body.
- Corneal oedema and stromal folds could lead to poor visual outcome in the initial post-operative period.
- If treated immediately by increasing the steroid drops, reducing intra-ocular pressure and using hypertonic saline, this can be reversed.
- If the corneal endothelial cell count is too low and the cellular stress was too much – corneal decompensation could take place.
- A corneal endothelial transplant may be necessary (DMEK – Descemet’s Membrane Endothelial Keratoplasty)
- Eyes with endothelial dystrophy, such as Fuch’s dystrophy, corneal dystrophy, pseudoexfoliation, mature cataracts, or high ametropia (>6 dioptres of myopia or hypermetropia), are all at greater risk than eyes without these features. Simple scoring systems have been devised to stratify patients into low, medium, and high risk.
- The incidence of early postoperative IOP increase is reported to be 2.3%–8.9% in all cataract extractions. The extent of such an early IOP increase was reported to be related to anterior chamber inflammation and prostaglandin release, capsulorhexis size, or residual viscoelastic material in the anterior chamber. This could also lead to corneal oedema.
Cystoid macular edema (CME) occurs when there is abnormal leakage and accumulation of fluid in the macula from damaged blood vessels in the nearby retina. Fluid buildup causes the macula to swell and thicken, which distorts vision.
- Macular edema may develop after any type of surgery that is performed inside the eye, including surgery for cataract, glaucoma, or retinal disease. A small number of people who have cataract surgery (experts estimate only 1-3 percent) may develop macular oedema within a few weeks after surgery. If one eye is affected, there is a fifty percent chance that the other eye will also be affected. Macular edema after eye surgery is usually mild, short-lasting, and responds well to non-steroidal anti- inflammatory drops.
- Another common cause of macular edema is diabetic retinopathy. Macular edema can also occur in association with age-related macular degeneration, or as a consequence of inflammatory diseases that affect the eye. Any disease that damages blood vessels in the retina can cause macular edema.
- Moreover, complicated cataract surgery, especially with vitreous loss, increases the risk of postoperative CME
Non-steroidal anti-inflammatory drops.
Intravitreal Anti-VEGF (like Avastin, Lucentis)
Intravitreal cortisone (Ozurdex or Vitreal S)
Vitrectomy – in rare resistant cases or where there is vitreo-macular traction
Epi-retinal membrane (ERM)
An epiretinal membrane is a thin sheet of fibrous tissue that can develop on the surface of the macular area of the retina and cause a disturbance in vision. An epiretinal membrane is also sometimes called a macular pucker, pre-macular fibrosis, surface wrinkling retinopathy or cellophane maculopathy.
A substantial under-detection of ERM in eyes before cataract surgery could incorrectly contribute to ERM incidence after surgery. According to a study published in the American Journal of Ophthalmology, ERM developed in 10% of eyes undergoing surgery. Less than 4% was found to be idiopathic while the rest had preretinal fibrosis pre-surgery.
Primary epiretinal membrane (ERM) is a common retinal disorder with a prevalence of 4% to 18.5%.
An eye with moderate cataract and an epiretinal membrane (ERM) demands strong presurgical diagnostic and decision-making skills.
The surgeon faces a two-part question:
- Which surgery—cataract or membrane peeling—should be performed first?
- Alternatively, should a combined procedure be performed?
To answer this, the surgeon must consider both the patient’s visual history and the information gleaned from OCT. If distortion is the main complaint – then the ERM is the leading cause, whereas blurred vision leans towards cataract. OCT will guide the surgeon.
Age Related Macular Degeneration (AMD)
In the literature, AMD is the most common co-morbidity that decreases visual outcome after cataract surgery. The prevalence of early AMD was 12.4% for those aged 66-74 years and 36% for those aged ≥ 85 years. Dr. Tin Y Wang (Effects of increasing age on cataract surgery outcomes in the elderly patients (BMJ 2001;332:1104-1106), reported that higher prevalence of pre-existing ocular diseases, like AMD, may affect cataract surgery outcomes in elderly patients.
The authors concluded that persons aged ≥ 85 years have a ten-fold higher prevalence of late AMD than those aged 70-74 years. Surgery is an effective treatment for age-related cataract-induced visual loss, though some clinicians suspect that such intervention may increase the risk of worsening underlying AMD, and thus may have deleterious effects on vi