European Journal of Cardiovascular Medicine

Visual impairment remains a significant global public health issue. According to the World Health Organization (WHO), visual impairment is defined as a presenting visual acuity of less than 6/18 in the better eye. Subcategories include moderate visual impairment (less than 6/18 to 6/60), severe visual impairment (less than 6/60 to 3/60), and blindness (less than 3/60).¹ Subnormal vision, for the purposes of this study, refers to visual acuity worse than 6/18 following intraocular lens implantation in cataract surgery, despite the absence of overt surgical complications. ²

Cataract remains the leading cause of avoidable blindness globally. In recent decades, advances in surgical techniques, especially the widespread adoption of phacoemulsification with intraocular lens (IOL) implantation, have greatly improved the safety and effectiveness of cataract surgery. Despite this, a significant proportion of patients continue to experience suboptimal visual outcomes, often unexpectedly. ³

Several studies have attempted to quantify the prevalence of subnormal postoperative vision among pseudophakics. Reported prevalence rates vary by region and methodology, ranging from 10% to 30%. ⁴ Contributing factors can include unrecognized pre-existing retinal or optic nerve disease, refractive errors, posterior capsular opacification (PCO), cystoid macular edema (CME), corneal opacities, or ocular surface disorders. In some cases, the subnormal vision may also be attributed to systemic comorbidities such as diabetes or hypertension affecting ocular health. ⁵

Understanding the etiology and frequency of postoperative subnormal vision is crucial for both clinicians and patients. From the patient’s perspective, subnormal vision can lead to disappointment and reduced satisfaction with surgery, even when the procedure itself is technically successful. ⁶ For surgeons and healthcare systems, identifying the predictive factors can help improve preoperative screening, refine surgical techniques, and enhance postoperative follow-up and management strategies. ⁷

Objectives: In this study an attempt was made to categorize the post operative visual outcome. Analyze the causes for subnormal vision in patients undergoing manual small incision cataract surgery with posterior chamber intraocular lens implantation.

The present study  was conducted in the Department of Ophthalmology, AJ Institute of Medical Sciences and Research Centre, Mangalore. Ninety one patients were included in this prospective study from November 2023 to October 2024. Patients in the age group of 50 to 80 years who were diagnosed to have senile immature cataract (SIMC) with best corrected visual acuity (BCVA) of <6/18 and willing to undergo small incision cataract surgery (SICS) with posterior chamber intra ocular lens (PCIOL) implantation were included in the study. Patients with history of previous intraocular surgeries, trauma, congenital anomalies of the eye, glaucoma and any other ocular co-morbidity that causes subnormal vision were excluded. Study was conducted after obtaining ethical committee clearance and informed consent from the patients participating in the study.

A complete history followed by detailed pre operative evaluation was done in all the patients. BCVA using Snellen’s distance vision chart, slit lamp examination, dilated fundus examination, measurement of intra ocular pressure (IOP) by Goldmann applanation tonometer and lacrimal sac syringing was performed in all patients. Keratometry and A-scan biometry was done in all patients to calculate the power of the PCIOL to be implanted using Sanders Retzlaff Kraff II (SRK II) formula.

All patients were subjected to Electrocardiography, chest X-ray, and routine blood investigations like complete blood count, serology, blood sugar estimation and renal function tests.

After obtaining medical fitness, all patients underwent manual SICS with PCIOL implantation under local anesthesia done by single experienced surgeon. Superior approach, continuous curvilinear capsulorhexis (CCC) and poly methyl metha acrylate (PMMA) single-piece IOLs were used in all patients.

Post operative evaluation was scheduled on the 1^st post operative day, at the end of 1 week and 6 weeks. All patients were advised tapering dose of topical antibiotic steroid combination and non steroidal anti inflammatory drugs (NSAIDs) for 6 weeks post operatively. At each post operative evaluation, BCVA using Snellen’s distance vision chart, slit lamp examination, dilated fundus examination, measurement of IOP by Goldmann applanation tonometer was done. All ninety one patients were followed up without any drop out for a period of six weeks.

Of the ninety one patients who were operated, 47 (51.65%) were males and 44 (48.35%) females. While 49 (53.85%) patients underwent surgery in the right eye, 42 (46.15%) were operated in the left eye. Forty eight (52.75%) patients were in the age group of 50-60 years; while 34 (37.36%) belonged to 61-70 years age group and 9 (9.9%) were in age group of 71 to 80years. Mild visual loss was defined as BCVA range of <6/9 - 6/18, while Moderate visual loss amounted to BCVA <6/18 – 6/60 and Severe visual loss included BCVA <6/60 (Table 1).⁷

Table 1: Classification of vision loss*

*Based on the WHO criteria for visual outcome in cataract surgery.

On the first post operative day fifty seven (62.64%) patients had mild visual loss, twenty nine (31.87%) had moderate visual loss and five (5.49%) had severe visual loss. BCVA at the end of one week showed seventy one (78.02%) patients had mild visual loss while only fifteen (16.49%) had moderate visual loss and five (5.49%) had severe visual loss. At 6 weeks post operative period eighty (87.91%) patients had mild visual loss, seven (7.69%) had moderate visual loss and four (4.40%) patients still continued to have severe visual loss (Table 2).

Table 2: Visual outcome on post operative evaluation

The causes for subnormal vision on first post operative day included iridocyclitis in eighty nine (97.80%) patients, striate keratopathy in fifty one (56.04%), pigments on the IOL in eleven (12.09%), residual lens matter overlying the visual axis in seven (7.69%), pigments on the endothelium in five (5.50%),  inflammatory membrane in three (3.30%), decentration of IOL in one(1.10%) and vitreous in the anterior chamber (AC) in one (1.1%). More than one cause contributed to the visual outcome in at least two third of the patients. At the end of one week along with the causes of subnormal vision on first post operative day, astigmatism played a major role in hampering vision in forty seven (51.65%) patients. At six weeks post operative follow up astigmatism continued to be the major cause for subnormal vision in eighty six (94.51%) patients, followed by residual lens matter in four (4.40%) and cystoid macular oedema in three (3.30%) patients (Table 3).

Table 3: Causes of subnormal vision on post operative evaluation

Cataract being the most common cause of curable blindness is treated by surgical intervention worldwide.¹ Excellent visual recovery is the rule following uneventful state of the art surgery. However at times this may not be true. In the present study, at six weeks final follow up the post operative visual outcome was categorized and the causes for post operative subnormal vision in patients undergoing manual small incision cataract surgery with posterior chamber intraocular lens implantation were analyzed.

Manual small incision cataract surgery involves fashioning of a self sealing sclerocorneal tunnel that requires no sutures, through which nucleus is removed as a whole or divided in parts.⁸ In order to accomplish this, nucleus has to be maneuvered into the anterior chamber (AC) which results in manipulation close to the iris and cornea. Thus in the immediate post operative period iridocyclitis, striate keratopathy, pigments on IOL, pigments on endothelium, inflammatory membrane obscuring the pupillary area are all too common and are significant causes of visual loss in the immediate post operative period. In the present study in addition to the above causes, residual lens matter, vitreous in the AC and decentration of IOL contributed to visual loss. Iridocyclitis observed in nearly all patients, varied in severity depending on the duration of surgery, past history of uveitis and intra operative manipulation of iris tissue. Visual loss was directly proportional to the extent of anterior chamber cellular reaction and flare. Iridocyclitis also resulted in pigment dispersion and deposition of the same on the IOL and corneal endothelium thus contributing to the visual loss. Formation of inflammatory membrane in the pupillary area though not very commonly seen in the present study also contributed to visual loss in the immediate post operative period.^{9 - 11}   Residual lens matter obscuring the visual axis seen in seven patients (7.69%).  It was observed at the 12 o’clock position in all the patients. This occurs due to difficulty in aspirating the superior cortex due to the posteriorly placed tunnel and the capsulorhexis.¹² Clinical and pathological reports have shown that significant inflammation results in the eye with residual lens matter.^{13 - 15} Vitreous in the anterior chamber was seen in one patient. Vitreous loss most often occurs during superior cortical wash secondary  to inadvertent superior rent in the posterior capsule.^{10, 16, 21} Decentration of the IOL observed in one patient was due to the IOL being placed in the sulcus – in the bag. This was done in the patient in whom there was a superior rent in the posterior capsule. Such a placement destabilizes the IOL which gets easily displaced.¹³ Compromised vision results due to the lenticular astigmatism.

With appropriate use of post operative topical antibiotic steroid along with NSAIDs, follow up at the end of one week showed significant reduction in the severity of iridocyclitis and striate keratopathy which was reflected as improvement in visual outcome with 78.02% of patients having only mild visual loss.^{10, 11, 16 – 19, 21} Fashioning a good triplanar stable sclerocorneal incision which is self sealing without sutures is vital in reducing the surgically induced astigmatism that occurs with wound healing.¹²  In the present study, at the end of one week astigmatism was seen to contribute to the subnormal vision in forty seven patients (51.67%) of which thirty five patients (74.47%) had against the rule astigmatism. This could be attributed to the flattening of the meridian perpendicular to the incision that occurred in the immediate post operative period causing a reduction in the curvature of the vertical meridian. This observation was similar to the results seen in various other studies.^{9, 10} Residual lens matter had got absorbed in three of the seven patients, contributing to improved visual outcome.

Follow up at the end of six weeks revealed the following visual outcome of mild visual loss in 87.91%, moderate visual loss in 7.69% and severe visual loss in 4.40% patients. The major contributing cause was astigmatism that was seen in 86 patients (94.51%). Gradual regression of with the rule astigmatism resulted in change in astigmatism to against the rule in seventy three patients (80.22%). Mean astigmatism was 0.73D which was similar to that seen in other studies.^{9, 10, 22}  Residual lens matter seen in four patients (4.40%) and cystoid macular oedema observed in three patients (3.30%) added to the poor visual outcome at the end of six weeks post operative period follow up.

In the present study, immediate post operative complications like   shallow anterior chamber, distorted pupil, iris prolapse, hyphaema, and glaucoma that affect the visual outcome were not seen as the operating surgeon had considerable surgical skill and experience. Post operative endophthalmitis was also not seen in any patient during the entire follow up period though various studies have found the incidence to vary between 0.03% - 0.18% .^{13, 19, 23} Posterior capsular opacification (PCO) which is one of the important causes of poor visual outcome following cataract surgery is seen ranging anywhere from three months to four years.^{13, 21, 24, 25} Incidence of PCO was 11.8% at one year and 28.4% at the end of five years in the study conducted by Schaumberg  et al. ²⁵ In the present study at six weeks follow up though there were four patients with residual lens matter, PCO was not seen in any patient. However with longer post operative follow up similar incidence of PCO could occur in these patients that results in significant hampering of vision.

Though manual SICS is a safe surgery, ^{10, 11, 12} the surgeon has to be extra careful in tunnel construction so as to achieve a self-sealing incision which is vital for a wound architecture that results in the desired lowered astigmatism potential that translates as better visual outcome. Since manual SICS involves the prolapse of nucleus into the anterior chamber and its delivery through the tunnel resulting in manipulations very close to the iris and the cornea, the surgeon has to be extra careful with these structures. Post operative inflammation and corneal edema can be all too common if proper care is not taken while handling the tissues. Cortical wash has to be complete and be followed by capsular polishing, in order to prevent PCO that may occur in the late post operative period. All the above mentioned steps would go a long way in minimizing the incidence of sub normal visual acuity in the future in the patients undergoing manual SICS with PCIOL implantation.

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