|Year : 2020 | Volume
| Issue : 1 | Page : 36-40
A study of factors affecting visual outcome in small incision cataract surgery
Renu Magdum, Iqra Mushtaq, Aishwarya Koul
Department of Ophthalmology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pune, Maharashtra, India
|Date of Submission||24-Aug-2020|
|Date of Decision||11-Sep-2020|
|Date of Acceptance||24-Sep-2020|
|Date of Web Publication||16-Nov-2020|
Department of Ophthalmology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune - 411 018, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: In spite of the changing patterns of blindness seen globally, cataract remains the most common cause of blindness worldwide. Modern cataract surgery aims to achieve a better unaided visual acuity (VA) with rapid postsurgical recovery and minimal complications. Small incision cataract surgery (SICS) is the most common cataract surgery done all over the world due to its nondependence on expensive machines and easier learning curve. VA following surgery is one of the key indicators for evaluating the quality of surgery.
Methods: This descriptive observational study was conducted in the ophthalmology department of a tertiary care hospital. It included 50 eyes of patients with uncomplicated senile cataract who underwent SICS. Patients were first evaluated for cataract using visual assessment, slit-lamp examination, ophthalmoscopy, and B-scan in case of mature cataracts.
Results: Age of patients varied from 39 to 72 years. The hardness of the nucleus varied from Grade 1 to Grade 4 by lens opacities classification system III classification. The types of cataract operated were cortical cataract with posterior subcapsular cataract (n = 36) and nuclear cataract (n = 16). Thirty-eight eyes out of 50 eyes (68%) had unaided VA of 6/18–6/60, whereas only 24% of eyes had vision better than 6/18 on POD 1. Unaided visual outcome on POD 7 showed 60% cases with VA better than 6/18. In two cases, vision remained below 6/60. Intraocular lens power was determined using the SRK II formula. In majority of cases (48%), the incision size was between 6.5 and 7 mm. The contour of the external incision was straight in 72% cases and frown shape in 14% cases. Most eyes showed improvement of vision between 1st and 7th postoperative day. However, in one eye, vision remained below 6/60.
Conclusions: Sight restoring cataract surgery is undoubtedly one of society's most cost-effective medical commonly done surgeries not only in India but also all over the world. All grades of nuclear sclerosis can be dealt with by this technique. A surgeon can further improve his/her postoperative results by giving due attention to the site, size, and contour of his/her incisions and taking care to protect the corneal endothelium while doing intraocular maneuvers and nucleus removal.
Keywords: Cataract, small incision cataract surgery, visual outcome
|How to cite this article:|
Magdum R, Mushtaq I, Koul A. A study of factors affecting visual outcome in small incision cataract surgery. J Med Soc 2020;34:36-40
| Introduction|| |
In spite of the changing patterns of blindness seen globally, cataract remains the most common cause of blindness worldwide., To eliminate preventable blindness, the World Health Organization promotes high-volume, high-quality, and low-cost cataract surgeries. Modern cataract surgery aims to achieve a better unaided visual acuity (VA) with rapid postsurgical recovery and minimal complications. Phacoemulsification and small incision cataract surgery (SICS) are the two common cataract surgeries done nowadays. Phacoemulsification has the advantage of a very small self-sealing incision which leads to faster rehabilitation and a better vision. However, it also has the disadvantages of higher cost and a steep learning curve. However, SICS is the most common cataract surgery done all over the world due to its nondependence on expensive machines and easier learning curve., The visual demands of people have increased among all strata of society, and any SICS surgeon will aim at giving perfect vision to his/her patient. VA following surgery is one of the key indicators for evaluating the quality of surgery. Limburg recommended that more than 80% of eyes at 4 weeks of cataract surgery and more than 50% of eyes at the time of discharge should have ≥6/18 vision with pinhole. Hence, there is a need to routinely monitor the outcomes of cataract surgery and to follow standardized cataract surgical protocols and postoperative follow-up care.
This study attempts to provide a rationale as to what factors will affect the visual outcome in SICS and how the surgery can be modified to have an improved visual outcome.
This study adhered to the tenets of the Declaration of Helsinki.
| Materials and Methods|| |
This descriptive observational study was conducted in the ophthalmology department of a tertiary care hospital in Western Maharashtra. The institutional ethical and scientific committees granted permission for the study. Fifty eyes of patients with uncomplicated senile cataract who underwent SICS were included in the study. Preoperative slit-lamp examination was done. Cases likely to cause difficulties during surgery such as eyes with pseudoexfoliation, poorly dilating pupils, very deep-set eyes, and subluxate lenses were excluded from the study. Furthermore, systemic conditions likely to affect wound healing such as uncontrolled diabetes mellitus and patients on systemic steroids were excluded from the study.
Demographic details such as age, sex, and occupation were recorded. Vision in each eye was recorded using Snellen's E chart held at 6 m distance. If the person was unable to identify the top line, VA was assessed at counting fingers at 3 m distance. The perception of light and projection of rays was noted in patients with very poor vision. Before surgery, both eyes were examined using the slit-lamp biomicroscope.
Preoperative evaluation included corneal keratometry, axial length assessment using A-scan ultrasound, and cataract grading according to the lens opacities classification system (LOCS) classification. The length of the SICS incision was decided according to the hardness and size of the nucleus. Intraocular lens (IOL) power was determined using the SRK II formula. The eye to be operated was dilated using mydriatic drops. The peribulbar block was used for anesthesia.
SICS surgery included the following steps:
Superior rectus bridle suture was applied. Conjunctival flap was raised and sclera exposed. Gentle cautery was done. Sclero-corneal tunnel incision was constructed using a Bard Parker handle with 15 number blade and crescent knife. Observations were made regarding the size of external wound, the contour of wound, and distance from the limbus; all were measured in mm. The side port was constructed using a stab knife and Trypan blue dye was injected to stain the anterior capsule. Dye was removed, the anterior chamber was washed with Ringer lactate, and a dispersive viscoelastic was injected. Anterior capsulotomy was done using a bent 26-gauge needle. Every attempt was made to create a continuous curvilinear capsulorrhexis. In unsuccessful cases, can opener capsulotomy was done. The main incision was opened in the center using 3.2 mm keratome. Hydrodissection was done using 26 number cannula and the nucleus was rotated and brought into AC under cover of viscoelastic. The main incision was opened using a 5.5 mm keratome. The nucleus was removed by viscoexpression or wire Vectis method. The cortical matter was removed using Simcoe's cannula. IOL was inserted under cover of viscoelastic in the capsular bag or the ciliary sulcus and dialed in position. Viscoelastic was removed and the stability of the AC was assessed after closing the side port by hydration. Sutures were applied, if needed, using 10/0 polyamide. Subconjunctival injection of gentamicin and dexamethasone was given. Eye pad was applied after instillation of moxifloxacin eye drops
Postoperatively, the eyes were examined for corneal clarity, anterior uveitis, shallow anterior chamber, presence of iris prolapse, and raised intraocular pressure. VA was assessed on 1st and 7th postoperative day using Snellen's E chart at 6 m distance.
| Results|| |
The visual outcome of fifty eyes operated by the SICS technique was evaluated with respect to the surgical steps.
Evaluation of the cataracts showed the presence of cortical, posterior, subcapsular, and nuclear forms of cataract. The hardness of the nucleus varied from Grade 1 to Grade 4 by LOCS classification. The types of cataract operated were cortical cataract with posterior subcapsular cataract (n = 36) and nuclear cataract (n = 16).
The demographic details showed a female preponderance, 32 female patients as compared to 18 male patients. The age of patients varied from 39 to 72 years [Figure 1].
The size of the incision varied from 5.5 mm to 7 mm depending on the hardness of the nucleus. In two cases, incision size had to be further increased at the time of nucleus delivery due to large and hard Grade 4 (LOCS) nucleus. In majority of cases (48%), the incision size was between 6.5 and 7 mm. Pie chart shows the incision size and number of cases [Figure 2].
Wound stability was maintained throughout surgery except in two cases, in which there was repeated iris prolapse.
Methods of nucleus removal were by wire Vectis method and viscoexpression. Hydroexpression was not practiced by any surgeon.
VA on 1st and 7th postoperative day was compared between different incision sizes
Bar graph shows VA on day 1 with different incision sizes [Figure 3].
Bar graph shows VA on day 7 with different incision sizes [Figure 4].
Most eyes showed improvement of vision between 1st and 7th postoperative day. However, in one eye, vision remained below 6/60.
| Discussion|| |
Cataract is the leading cause of blindness in India, and SICS is the most common sight restoring surgery done due to its safety, economy, and effectivity. The patient's postoperative visual satisfaction, vision-related quality of life, ability to carry out day to day activities without obstacles, and overall productivity depend on the visual outcome of the surgery. A poor visual outcome following cataract surgery subjects a person to a lifetime of compromise. This study was done to evaluate postoperative VA and study surgical factors affecting the visual outcome.
The basis of SICS is the tunnel construction for entry into the anterior chamber. The parameters important for the structural integrity of the tunnel are the self-sealing property of the tunnel, the location of the wound in the sclera, and shape of the wound. Wound should be carefully planned according to the type of technique, hardness of the nucleus, and condition of the endothelium.
Since this study was conducted in patients of senile cataract, age of patients varied from 39 to 72 years. There was a female preponderance in our study with 32 females as compared to 18 males. Similar results were reported in a study done in 2015. They found female gender as a risk factor for poor outcome. However, some studies showed good outcomes in females. Two patients were below 40 years of age, may be due to hereditary factors, since trauma and diabetes mellitus had been ruled out. The above study also found increasing age as one of the risk factors for poor outcomes. Despite controlling for ocular morbidities, increasing age was found to be one of the predictors for poor outcome in their study. They suggested that denser cataracts made detection of ocular comorbidities difficult to detect preoperatively.
Thirty-six cases had cortical cataract, whereas 14 had nuclear cataract with nuclear density ranging from Grade1 to Grade 4 by LOCS classification.
Incision size varied from 5.5 mm to 7 mm, with the 5.5 mm to 6 mm range being the most common (48%). The size of the tunnel in SICS surgery can vary from 5.5 mm to 7.5 mm and remain stable. The hardness of the nucleus decides the incision size. A well-done pocketing can prevent endothelial damage. Burgansky et al. have shown increased induced astigmatism with increased incision size. They found induced astigmatism of 0.6 ± 0.3D for 6 mm incisions, 0.75 ± 0.67D for 6.5 mm, and 1.36 ± 0.77D for 7 mm incisions. Oshika et al., in a long-term prospective study over 3 years, compared the results of 3.2 mm and 5.5 mm SICS procedures. They found the 3.2 mm group to have significantly better VA in the early postoperative period. This difference was seen throughout the period of the study. They concluded that smaller incisions give better visual outcomes due to lesser surgical induced astigmatism.
All incisions were 1.5–2 mm away from the limbus. Maneuverability was hampered in especially deep-seated eyes.
Incision contour varied from straight (72%) to frown (14%) incision. The construction of a frown incision requires more dexterity but induces less astigmatism. Wound stability was maintained in all eyes except two, in which there was repeated iris prolapse during surgery.
Two cases were given a temporal incision as they were likely to require glaucoma surgery later on. Evaluation of surgically induced astigmatism was not included in our study, but several studies have shown lesser induced astigmatism in temporal and super temporal incisions as compared to superior incisions.,
The technique of nucleus delivery was viscoexpression and wire Vectis removal in almost equal number of cases. Some studies have reported inferior iridodialysis during viscoexpulsion due to the inferior part of the sphincter caught between Vectis and nucleus during nucleus delivery, causing tear at 6 o'clock position.
VA on 1st postoperative day varied from <6/60 to 6/9 by Snellen's chart. About 68% of eyes had vision between 6/60 and 6/18, whereas only 24% of eyes had a VA better than 6/18. The WHO recommendations state that at least 90% of cataract operated eyes should have a VA of ≥6/18. A series of white cataracts undergoing SICS had 7% eyes with corneal edema on 1st postoperative day.
Visual outcome on Day 7 showed 60% cases with vision better than 6/18. In a similar study done in Pakistan, 64% of eyes had vision better than 6/18 at 1 week postoperatively, which further improved to 66.3% eyes at 6 weeks postoperatively. We did not follow-up the eyes after 1 week in our study. In two cases, the vision remained below 6/60. Both eyes belonged to patients with Grade 4 nuclear cataracts with age >65 years. One of them required sutures to be applied. The poorer outcome may have been due to poor endothelial cell count due to age and surgical induced astigmatism due to sutures.
However, several other factors, which were not a part of this study, may also affect postoperative visual outcome. Low preoperative endothelial cell counts and surgically induced astigmatism were not evaluated. Surgery-induced uncorrected refractive error has been reported as the most common cause of poor visual outcome. These and a small sample size remain the shortcomings of this study.
| Conclusions|| |
Manual SICS is a relatively safe surgery with a gentler learning curve. All grades of cataract can be dealt with by this technique. Certain points, if kept in mind while performing this surgery, can further improve visual outcomes, maybe even similar to phacoemulsification. A well-constructed sclerocorneal tunnel, keeping in mind the square architecture, leads to a stable anterior chamber and a self-sealing wound needing no sutures. Nearer to the cornea the external incision, greater is the likelihood of induced astigmatism. An adequate capsulotomy leads to easier and less traumatic nucleus prolapse in AC. Hydro-procedures further reduce the size of the nucleus for easier delivery through the incision. Adequate cortical cleanup should be done using side port and in-the-bag placement of the IOL should be the aim in all surgeries. Meticulous attention to each surgical step will give an improved visual outcome in each case. There is a need to follow standardize cataract protocols and postoperative follow-up care. Sight restoring cataract surgery is undoubtedly one of society's most cost-effective medical commonly done surgeries not only in India but also all over the world. All grades of nuclear sclerosis can be dealt with by this technique. A surgeon can further improve his/her postoperative results by giving due attention to the site, size, and contour of his/her incisions and taking care to protect the corneal endothelium while doing intraocular maneuvers and nucleus removal. This study studied fifty eyes which underwent this procedure for the visual outcome at 1st and 7th postoperative day and attempted to correlate the visual outcome with the surgical steps.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Foster A, Gilbert C, Johnson G. Changing patterns in global blindness: 1988-2008. Community Eye Health. 2008; 21:37-9
Tabin G, Chen M, Espandar L. Cataract surgery for the developing world. Curr Opin Ophthalmol. 2008; 19:55-9
Limberg H, Foster A, Gilbert C, Johnson GJ, Kyndt M. Routine monitoring of visual outcome of cataract. Part 1: development of an instrument. Br J Ophthalmol 2005;89:45-49
Shamanna BR, Dandona L, et al.
Economic burden of blindness in India. Ind J Ophthalmol 1998; 46:169-72
Singh AJ, Garner P, Floyd K. Cost effectiveness of public funded options for cataract surgery in India. Lancet 2000; 355:180-4
Khandekar RB, Jain BK, Sudhan AK, Pandey KP. Visual acuity at 6 weeks after small incision cataract surgery and role of audit in predicting visual acuity. Eur J Ophthalmol 2010:345-352
Limburg H. Monitering cataract surgical outcomes: methods and tools. Community Eye Health 2002;15:51-3
Malta S, Park J, Palamaner Subhash Shantha G, Khanna RC, Rao GN. Cataract Surgery Visual Outcomes and Associated Risk Factors in Secondary Level Eye Care Centres of L V Prasad Eye Institute, India. PLoS ONE 11(1):e0144853
Haldipurkar SS, Shikare HT, Gokhale V. Wound construction in manual small incision cataract surgery. Indian J Ophthalmol 2009;57:9-13
Venkatesh R, Muralikrishnan R, Balent LC, Prakash SK, Prajna NV (2005) Outcomes of high volume cataract surgeries in a developing country. Br J Ophthalmol 89:1079-1083
Burgansky Z, Isakov I, Avizemer H Bartov E. Minimal astigmatism after sutureless planned extracapsular cataract extraction. J Cataract Refract Surg 2002;28:499-503.
Oshika T, Nagahara K, Yaguchi S, Emi K, Takenaka H, Tsuboi S et al.
Three year prospective randomised evaluation of intraocular lens implantation through 3.2 and 5.5mm incisions. J Cataract Refract Surg 1998;24:509-14
Singer JA. Frown incision for minimising induced astigmatism after small incision cataract surgery with rigid intraocular lens implantation. J Cataract Refract Surg 1991;17 suppl:677-88
Gokhale NS, Sawhney S. Reduction in astigmatism in manual small incision cataract surgery through change in incision site. Indian J Ophthalmol 2005;53:201-3
Venkatesh R, Das M, Prasanth S, Muralikrishnan R. Manual Small Incision Cataract Surgery in eyes with white cataracts. Indian J Ophthalmol 2005;53:173-6
Olawoye OO, Ashaye AO, Bekibele CO, Ajai BG. Visual outcome after cataract surgery at the University College Hospital, Ibadan. Ann lb Postgrad Med 2011 Jun; 9: 8–13. Br J Ophthalmol 2005;89:1079-83.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]