|Year : 2015 | Volume
| Issue : 4 | Page : 472-477
Dry eye following phacoemulsification surgery and its relation to associated intraoperative risk factors
PK Sahu, GK Das, Aman Malik, Laura Biakthangi
Department of Ophthalmology, UCMS and GTB Hospital, New Delhi, India
|Date of Web Publication||21-Oct-2015|
P K Sahu
Department of Ophthalmology, UCMS and GTB Hospital, New Delhi - 110 095
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Purpose: The purpose was to study dry eye following phacoemulsification surgery and analyze its relation to associated intra.operative risk factors.
Materials and Methods: A prospective observational study was carried out on 100 eyes of 100 patients without preoperative dry eye. Schirmer's Test I, tear meniscus height, tear break-up time, and lissamine green staining of cornea and conjunctiva were performed preoperatively and at 5 days, 10 days, 1-month, and 2 months after phacoemulsification surgery, along with the assessment of subjective symptoms, using the dry eye questionnaire. The correlations between these values and the operating microscope light exposure time along with the cumulative dissipated energy (CDE) were investigated.
Results: There was a significant deterioration of all dry eye test values following phacoemulsification surgery along with an increase in subjective symptoms. These values started improving after 1-month postoperatively, but preoperative levels were not achieved till 2 months after surgery. Correlations of dry eye test values were noted with the operating microscope light exposure time and CDE, but they were not significant.
Conclusion: Phacoemulsification surgery is capable of inducing dry eye, and patients should be informed accordingly prior to surgery. The clinician should also be cognizant that increased CDE can induce dry eyes even in eyes that were healthy preoperatively. In addition, intraoperative exposure to the microscopic light should be minimized.
Keywords: Dry Eye, Intra-operative Risk Factor, Microscope Exposure Time
|How to cite this article:|
Sahu P K, Das G K, Malik A, Biakthangi L. Dry eye following phacoemulsification surgery and its relation to associated intraoperative risk factors. Middle East Afr J Ophthalmol 2015;22:472-7
|How to cite this URL:|
Sahu P K, Das G K, Malik A, Biakthangi L. Dry eye following phacoemulsification surgery and its relation to associated intraoperative risk factors. Middle East Afr J Ophthalmol [serial online] 2015 [cited 2019 Aug 22];22:472-7. Available from: http://www.meajo.org/text.asp?2015/22/4/472/151871
| Introduction|| |
Dry eye is described as a state of abnormal tear film that can be caused by a number of conditions which alter its composition and affect its stability. It is one of the most important factors influencing the quality of life in elderly population. Moderate and severe dry eye can impair the ability of patients to perform activities of daily living, impact work productivity and influence mood and confidence. The overall impact of moderate dry eye on patients has in fact been quantified as being similar to the impact of moderate angina. In the United States alone, approximately 7-10 million Americans require artificial tear preparation, with consumers spending over 100 million dollars/year.
With recent advances in cataract and refractive surgeries, postoperative dry eye has been implicated as the most important obstacle to patient's satisfaction despite an excellent visual recovery. Khanal et al. in their study found that deterioration in corneal sensitivity and tear physiology is seen immediately after phacoemulsification. Li et al. also documented the incidence of dry eye to be increased dramatically after cataract surgery. Subjective dry eye type symptoms after routine cataract extraction were also demonstrated by Roberts and Elie.
Denervation of the corneal nerves by incision, production of free radicals due to ultrasound energy, microscope light exposure time during surgery and pre- and post-operative medications have been implicated as the possible causes of dry eye following phacoemulsification. A study by Cho and Kim revealed a significant correlation between the microscope light exposure and dry eye test values but did not find an association between the phacoemulsification energy and dry eye test values. Keeping these in mind, the present study was undertaken to find both the subjective and objective severity of dry eye in postphacoemulsification surgery using dry eye questionnaire (DEQ) and dry eye test values such as tear break-up time (TBUT), Schirmer I test (ST-I), tear meniscus height (TMH) and lissamine green (LG) staining of cornea and conjunctiva. The study also sought to find out the relation among microscope light exposure time, phacoemulsification energy, and postoperative dry eye.
| Materials and Methods|| |
This prospective observational study was performed between November 2011 and January 2013 after selecting 100 consecutive patients who attended the outpatient department of UCMS and GTB hospital for phacoemulsification surgery, with due approval by the Ethics Committee of the institutional review board. Prior informed consent was obtained from each subject, inclusion criteria being subjects over 45 years of age, with senile cataract, without preexisting dry eye. Any disorder of eyelids, past ocular surgeries, any other preexisting ocular or systemic disease, any ocular or systemic medication, and smokers were excluded from the study. The sample size was calculated assuming the prevalence of dry eye to be 50% in the 1st postoperative month., With 10% precision on either side, n = 97. The calculated sample size was 100.
General patient information and detailed history of systemic and ocular disease were recorded, and thorough evaluation was carried out in all patients. 2 days before cataract surgery ST-I, TBUT, and TMH were measured. First, ST-I was evaluated without corneal anesthesia by using a standardized tear strip (Bio division Ltd., UK). In a quiet room, with dimmed light, the patient was made to sit comfortably and the strip was inserted into the lower temporal lid margin, after folding it at the notch and asking the patient to look up and in. After 5 min, the strip was removed, and the length of the moistened area was recorded. Next, the stability of the tear film over the conjunctiva and cornea TBUT was assessed using a slit-lamp with a cobalt blue filter and sodium fluorescein. The interval between ST-I and TBUT was at least 10 min. A fluorescein strip was applied in the lower palpebral conjunctiva, and the patient was asked to blink 5 times, after which he/she is asked to refrain from blinking. The appearance of black spots or lines indicates the onset of dry spots and the interval between the last blink and the first randomly distributed dry spot was taken as the TBUT. The average of three measurements was recorded and a value < 10 s was taken as abnormal. After 5 min, with the patient sitting on the same slit lamp, TMH was evaluated by adjusting the vertical length of slit beam on the tear meniscus at the center of the lower lid and the readings were noted from the slit lamp scale.
Lissamine green staining of the cornea and conjunctiva was done on the next day. For this, LG filter paper was applied in the lower palpebral conjunctiva and the patient was asked to blink several times. The grading was done as per 0-5 scale Oxford grading scheme of LG staining of cornea and conjunctiva, using a slit lamp, set at ×16 magnification with ×10 oculars with Haag-Streit slit lamp. A DEQ developed by Begley et al., was utilized to evaluate the risk factors and the frequency of specific symptoms of dry eye. It consists of 15 questions and in the majority of the questions, the responses were graded from 0 to 4 where zero implies absence of symptoms and four indicates maximal symptoms.
All the patients underwent phacoemulsification surgery under peribulbar block using 5 ml of 2% lidocaine for local anesthesia, ringer lactate as irrigating solution and hydroxyl propyl methyl cellulose as viscoelastic material after prior written informed consent by the main author (PKS). Combination of Ofloxacin and ketorolac eye drop was instilled 4 times a day, 1 day before surgery. Mydriasis was achieved using eye drop tropicamide 0.8% and phenylephrine 5.0% 1 h prior to the surgery. A standard surgical technique was used in all patients. A 3.2 mm superotemporal corneal incision was made just anterior to vascular arcades of the corneoscleral limbus using a calibrated knife. A paracentesis incision of 1 mm was made 60° apart with a calibrated knife. Capsulorrhexis, hydrodissection, and nucleus rotation were carried out sequentially. A phacoemulsification tip was used to emulsify the cataract using stop and chop technique. After emulsification of nuclear fragments and irrigation aspiration of residual cortical matter, a foldable intraocular lens was implanted inside the capsular bag. Removal of viscoelastic material was done, and finally, the incision was hydrated using a 30-gauge cannula. Total duration of surgery and cumulative dissipated energy (CDE) (from ALCON infinity machine, ALCON, USA) was noted down in every case. All the patients received a standard postoperative regime of topical steroid, antibiotic, cycloplegic and mydriatic, and nonsteroidal anti-inflammatory drugs in tapering doses for 4 weeks. In the event of any intra-operative complication or if any other drug used in the perioperative period, they were excluded from the study. In the postoperative period ST-I, TBUT, TMH, and LG staining of cornea and conjunctiva and dry eye symptoms by DEQ were examined on day 5, day 10, 1-month, and 2 month in the same manner and sequence as preoperative period.
The data were collected and checked for accuracy on a daily basis and entered in SPSS version 16 IBM corporations, Chicago, USA.
Qualitative data were expressed by percentages with confidence intervals, whereas quantitative data and scores were expressed by mean and standard deviation. For normally distributed data mean scores were compared using paired t-test. When data were skewed, the mean scores were compared using Wilcoxon Rank Sum test. Correlation of CDE and microscopic light exposure time with ST-I, TBUT, TMH, LG staining, and DEQ were analyzed and studied.
| Results|| |
In our study, most of the patients were > 55 years of age with average being 60.80 ± 5.94 years (range: 46-70). There were more females (59%) as compared to males (41%). Preoperatively, the mean ST-I was calculated to be 17.56 ± 6.88. Postoperatively, it progressively decreased when assessed on day 5 and day 10, after which however, a gradual rising trend was seen up to our last follow-up of 2 months.
The preoperative mean TBUT was 16.11 ± 2.55 which also followed a similar trend of initial postoperative decline up to 1-month and then a gradual rise, as seen in ST-I. The mean preoperative TMH was 0.38 ± 0.047 which showed a decreasing trend up to 1-month postsurgery and then acquired a rising trend. The changes in ST-I value [Figure 1] and [Table 1], TBUT [Figure 2] and [Table 1] and TMH [Figure 3] and [Table 1] were all found to be statistically significant at all postoperative follow-up intervals.
Of 100 patients, prior to surgery, 97 had an LG grading of 0, and only 3 patients had a grading of 1, mean LG grading being 0.03 ± 0.17. Postsurgery, the lisaamine grading also increased till 1-month, then revealed a reversal trend, with statistically significant values at each period [Figure 4] and [Table 1].
The mean DEQ score, which was 13.13 ± 1.08 preoperatively, exhibited a sharp rise on the 5th postoperative day, followed by a very slow steady rising trend [Figure 5] and [Table 1]. This too showed statistical significance in each visit.
|Figure 5: Dry eye questionnaire score values at different time intervals|
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Correlation of cumulative dissipated energy and microscopic light exposure time with dry eye test values
The mean CDE was 12.256 ± 6.44 and mean microscopic light exposure time was 16.10 ± 3.48.
There was a negative correlation of the CDE and the microscopic light exposure time with ST-I, TBUT and TMH values, but this association was not statistically significant. The positive correlation of the CDE and the microscopic light exposure time with the LG grading values and the DEQ Score was noted, but these again, did not attain statistical significance [Table 2] and [Table 3].
|Table 3: Microscopic light exposure and its correlation with the change in dry eye test values|
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| Discussion|| |
This prospective observational study was carried out to determine changes in the tear film status and the occurrence of dry eye or the aggravation of its symptoms after phacoemulsification. It also attempted to define the possible intra-operative factors that might be responsible for the aforementioned changes. Our results revealed that all the dry eye parameters deteriorated after surgery when compared to preoperative values. The decline of these parameters was observed to be directly related to an increase in CDE, along with an increase in operating microscope light exposure time as well.
Cataract surgery has widely been seen to adversely affect the tear film status in the early postoperative period, hence leading to the development of dry eye in various studies., At the Hawaiian Eye 2011 meeting, a report was discussed the results of a prospective multicenter study which assessed the prevalence of dry eye in 272 eyes that underwent cataract surgery. The study found that > 60% of eyes had abnormal TBUT, 50% of eyes had central corneal staining and 21.3% of eyes had low Schirmer test results, all of which are diagnostic signs of dry eye or dry eye syndrome.
Comparison between preoperative and postoperative tear film parameters have been conducted by few studies, all of which reported short-term disruption in tear function postcataract surgery. When Ram et al. compared Schirmer scores and TBUT in 25 eyes before and after surgery, they noticed a decrease in both values at various time intervals up to 2 months postoperation. Li et al. demonstrated a similar deterioration of both Schirmer score and TBUT in 50 eyes, when followed up to 3 months. Besides the above 2 tests, Cho and Kim included TMH in their study conducted in 70 eyes of 35 patients after phacoemulsification and noticed a decline in all three test values, on a follow-up of 3 months.
Khanal et al. investigated postphacoemulsification changes in corneal sensitivity and tear physiology in a longitudinal, randomized trial on 18 patients. They found that deterioration in corneal sensitivity and tear physiology is seen immediately after phacoemulsification, and the tear functions recover within 1-month. We also observed a similar trend where the ST-I, TBUT, and TMH values started recovering after 1-month. In 2008, Liu et al. compared 25 diabetic cataract patients with 20 age-matched nondiabetic cataract patients. They found that tear secretion was reduced in diabetic cataract patients after phacoemulsification, which worsened their dry eye symptoms and predisposed them to ocular damage. The postoperative decrease in TBUT was seen in nondiabetics as well. Their study showed a reversal trend in TBUT after 1-week, similar to our study which showed the same, 10th day onwards. The unanticipated finding in their study, however, was an increase in ST-I in initial postoperative period, which returned to the preoperative value at day 90; the reason for which was not provided.
In terms of subjective symptoms of dry eye, Cho and Kim had concluded in 2009 that there is indeed an aggravation of dry eye symptoms after cataract surgery. Roberts and Elie also demonstrated that a clinically significant proportion of cataract surgery patients experienced some degree of dry eye symptoms after surgery. Dry eye symptoms increased in both diabetics and nondiabetics in Liu's study, but it returned to preoperative levels between day 30 and 180 in the nondiabetic group, while it remained elevated in diabetic group even on day 180. In the present study, all patients are nondiabetic and all of them exhibited an aggravation of subjective dry eye symptom postphacoemulsification, which did not show any reduction of symptoms even on day 60.
In terms of long-term effect, Srinivasan et al. and Gharaee et al. published that modern day cataract surgery has no significant effect on the ocular surface and the tear film on a long term basis., But their evaluation was done only from 3 months onward postoperatively and the status of parameters before 3 months is not known. Even after 3 months, the mean TBUT was significantly higher as compared to the preoperative value and was statistically significant.
On consideration of the pathological basis for the results of our study, the possible reason for reduced Schirmer scores seen could be the severing of corneal nerves as a result of the corneal sections. This could disrupt the corneal - lacrimal gland loop responsible for tear secretion, and thus reduce the same leading to decreased ST-I and TMH values.
The significant reduction in TBUT seen in our study indicates tear film instability in the operated eye, possibly resulting from either a surface irregularity at the site of the section, which induces a faster break-up of the tear film, or from a decreased mucin production by the conjunctiva as proposed by Li et al.
When Li et al. investigated pathogenic factors responsible for dry eye in patients after cataract surgery  their impression cytology demonstrated that even 3 months following cataract surgery, goblet cells were reduced in the bulbar conjunctiva along with the occurrence of squamous metaplasia, and this was most marked in the regions covered by the lower lid, suggesting that dry eye might be induced by eye drops. The authors concluded that the dry eye could develop or deteriorate dramatically following cataract surgery and misuse of eye drops is one of the major pathogenic factors responsible for it. Prior works of other authors have revealed similar findings,, however, at present more studies are required to understand the relationship between eye drops in the postoperative period and dry eye.
In an attempt to find out possible intra-operative causal factors for development of dry eye, we studied the amount of phaco-energy in each case, and found a negative correlation of the CDE with ST-I, TBUT and TMH postoperation, although this relationship was not statistically significant. This is in contrast to Cho and Kim, study, which observed that phaco-energy did not aggravate dry eye symptoms or signs. In our study, use of more ultrasound energy in some cases may have led to damage of corneal structures such as the epithelium, stroma, keratocyte, endothelium, and nerve plexuses leading to the observed increase in dry eye parameters.
Many reports have addressed iatrogenic retinal phototoxicity related to operating microscope exposure., Aside from retinal phototoxicity, microscope light exposure has been implicated in the aggravation of dry eye symptoms and signs as well in Cho's and Kim's study. In our study, a negative correlation was noted between microscope light exposure time and dry eye test values.
The main limitations of this study are short period of follow-up and varied results of ST-I, TBUT and TMH. Another limitation is the representation of dry eye symptoms like foreign body sensation, burning, dryness, etc., as a numerical value.
| Conclusion|| |
We observed that cataract surgery is indeed capable of inducing dry eye symptoms and signs. Therefore, prior to surgery, patients must be informed about the possible increase in dry eye symptoms, and if indicated, artificial tears may be prescribed in the postoperative period. Intra-operative exposure to the microscope light should be minimized by appropriate use of filters and shortening the exposure time. The clinician should also be cognizant that increased CDE can exacerbate dry eye symptoms and signs in eyes that were healthy preoperatively. Cautious and restricted use of ultrasound energy is advised by the authors. Future research should focus on realistic modifications to the phacoemulsification procedure to achieve a safer approach in patients with ocular surface disorders. Although we noticed an improvement in the tear film status, 1-month onward after surgery, studies with longer follow-up period are recommended to assess the time taken for the tear film to recover to its preoperative status.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]