Comparative evaluation of keratometric changes after pterygium excision surgery

Deepti Shukla; Indra Dandaliya; Preeti Mittal; Madhu Mathur

doi:10.4103/jcor.jcor_65_18

ORIGINAL ARTICLE

Year : 2019 | Volume : 7 | Issue : 3 | Page : 110-112

Comparative evaluation of keratometric changes after pterygium excision surgery

Deepti Shukla, Indra Dandaliya, Preeti Mittal, Madhu Mathur
Department of Ophthalmology, J.L.N. Medical College, Ajmer, Rajasthan, India

Date of Submission	09-Aug-2018
Date of Acceptance	15-Jan-2019
Date of Web Publication	11-Dec-2019

Correspondence Address:
Indra Dandaliya
Department of Ophthalmology, J.L.N. Medical College, Ajmer, Rajasthan
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jcor.jcor_65_18

Abstract

Aim: The aim of this study was to evaluate and compare keratometric changes after pterygium excision surgery. Settings and Design: The study was carried out at a tertiary eye care center in central Rajasthan, India. Materials and Methods: Total 50 patients of primary pterygium without any other corneal pathology were undergone to pterygium excision surgery with conjunctival autograft and selected for study after complete preoperative assessment. Keratometric values were measured using Bausch-Lomb keratometer preoperatively and postoperatively on day 1, day 7, and 1 month serially. Mean difference in keratometric values or mean keratometric astigmatic changes preoperatively and postoperatively were compared. Results: The mean age of the patients was 32.58 ± 9.67 years and male-to-female ratio was 2.12:1. The mean preoperative keratometric values were significantly decreased postoperatively in all grades of pterygium. Moreover, the amount of keratometric astigmatism varies with the grades of pterygium. In patients with pterygium Grade I, mean keratometric (K) value was reduced to 0.66 ± 0.30 diopter (D) at 1 month postoperatively. Similarly, in patients with pterygium Grade II, it was reduced to 0.71 ± 0.32D, and in pterygium Grade III and IV, it was reduced to 1.82 ± 0.27D and 2.72 ± 0.53 D, respectively at 1-month follow-up visit. Conclusion: The pterygium excision surgery significantly causes reduction in pterygium-induced keratometric astigmatism. Moreover, the differences in the K-reading are proportional to the grades of pterygium.

Keywords: Keratometric astigmatism, keratometric reading, pterygium-induced astigmatism, pterygium surgery

How to cite this article:
Shukla D, Dandaliya I, Mittal P, Mathur M. Comparative evaluation of keratometric changes after pterygium excision surgery. J Clin Ophthalmol Res 2019;7:110-2

How to cite this URL:
Shukla D, Dandaliya I, Mittal P, Mathur M. Comparative evaluation of keratometric changes after pterygium excision surgery. J Clin Ophthalmol Res [serial online] 2019 [cited 2023 Mar 23];7:110-2. Available from: https://www.jcor.in/text.asp?2019/7/3/110/272713

Cornea is transparent, avascular, and watch glass-like curved solenoid structure which forms one-sixth part of the eyeball. The central 3–4 mm of anterior surface of cornea is spherical and the periphery is flatter. The corneal stroma plays several pivotal roles within the eye, optically, it is main refracting lens to perfect transmission of light, and mechanically, it protects the inner contents of the eye.^[1] Pterygium is a degenerative triangular fibrovascular subepithelial growth of bulbar conjunctival tissue over the limbus onto the cornea.^[2] It is characterized by hyalinization and elastic degeneration of subconjunctival tissue which invades cornea, destroying superficial layers of the stroma, and Bowman's membrane. Histopathologically, the changes include epidermal proliferation, inflammatory infiltrates, activated fibroblasts, and extracellular matrix changes such as accumulation of elastin, glycosaminoglycans, and collagen.^[3],[4],[5] It can be divided into three types according to the size of lesion. Type 1 extends <2 mm on to the cornea, Type 2 involved 2–4 mm of the cornea which may interfere with tear film and induces astigmatism, while Type 3 involves >4 mm of the cornea and involves the visual axis. Furthermore, it can be categorized in four types according to the extent of corneal involvement of the pterygium: Grade I pterygium reaching up to the limbus, Grade II reaching midway between the limbus and the pupil, Grade III reaching up to the papillary margin, and Grade IV crossing the pupil. Exact pathogenesis is still unclear, but there are several environmental factors known to lead a pterygium such as ultraviolet ray exposure, dry, dusty climate, chronic inflammations, and dry eye among others. Advancing age and male gender are also identified as risk factors.^[6] The pterygium excision is indicated if it is progressive, involves visual axis, and induces astigmatism. We conducted this study to assess the effect of pterygium excision on pterygium-induced astigmatism postoperatively on day 1, day 7, and 1 month serially.

Materials and Methods

This prospective, comparative, interventional study was designed to include 50 patients of various grades of pterygium who underwent excision surgery with conjunctival autografts after complete preoperative assessment. Patients who were having corneal diseases such as corneal lesion, opacity, degeneration, history of other ocular surgery and bleeding disorders, diabetes, hypertension, uremia, and connective tissue disorder were excluded from the study. Only those patients who had primary pterygium were included in the study. All patients were evaluated preoperatively and postoperatively on day 1, day 7, and 1 month. Complete ocular examination was done including best-corrected visual acuity, slit-lamp biomicroscopic examination, refraction (subjective and objective), ocular movements, details of pterygium, keratometry (Nidek's autokeratometer), and posterior segment examination. Mean difference in keratometric values or mean keratometric astigmatic changes preoperatively and postoperatively were compared using Bausch-Lomb keratometer.

All patients were operated by the same surgeon so as to exclude any surgeon bias. After giving peribulbar anesthesia, entire pterygium was removed. The defect created by the removal of pterygium is measured with calliper. The globe was rotated inferomedially to give access to uninvolved superotemporal bulbar conjunctiva and a raised bleb was formed, separating conjunctiva from the Tenon's capsule. A graft approximately 0.5 mm longer than the defect was dissected out taking care to leave Tenon's capsule intact. This graft was placed over the recipient bed, flattened, and then sutured to the adjacent conjunctiva with 8/0 silk. Donor site required no suturing and healed rapidly without scarring. The number of sutures applied depended upon the defect created by the removal of pterygium (the number of sutures applied varied from 5 to 7). On day 1, day7, and 1 month, keratometric values were measured using Bausch-Lomb keratometer to find mean difference in keratometric values or mean keratometric astigmatic changes.

Statistical analysis

All observed data were presented as mean and standard deviation. Complete statistical analysis was performed using commercially available statistical software SPSS (version 17). Moreover, P ≤ 0.05 was considered statistically significant.

Results

The amount of keratometric astigmatism increases in accordance with increasing grades of pterygium. The mean age of the patients was 32.58 ± 9.67 years (age range 21–65) with male predominance (male-to-female ratio: 2.12:1). The distribution of pterygium was more common on nasal side and in rural population. The main complaints of the patients were redness (92%), foreign body sensation (92%), and watering (80%). Most of the cases of pterygium belong to Grade II (58%) followed by Grade III (20%) and Grade I (18%), and Grade IV contained only 4% patients. Pterygium Grade I and II were presented by 80%–90% patients of the age group of 21–40 years, whereas Grade III and IV were present in 60% patients of the age group of 40–50 years. The mean preoperative keratometric astigmatism was 2.30 ± 0.61 diopter (D) in pterygium Grade I, 2.70 ± 0.56 D in Grade II, 3.85 ± 0.59 D in Grade III, and 6.50 ± 0.83 D in Grade IV. In the pterygium with Grade I, the K-reading difference produced is between 2 and 2.5 D in 100% cases. Preoperatively, all patients of pterygium Grade I had 2–2.5 D difference in k-readings, Grade II had 2–3 D difference in 27 cases (54%), and only two cases (4%) had 3–4 D; Grade III included 3–4 D in all ten cases (20%), whereas Grade IV contained two cases (4%) with >5 D. Postoperatively, keratometric astigmatism reduced to mean k value of 1.64 ± 0.33 D in Grade I pterygium, 1.83 ± 0.39 D in Grade II, 2.3 ± 0.61 D in Grade III, and Grade IV reduced to 4.62 ± 0.88 D on early postoperative period that was day 1. On day 7, keratometric astigmatism further reduced to 1.25 ± 0.27 D in Grade I, 1.45 ± 0.30 D in Grade II, 1.97 ± 0.33 D in Grade III, and 3.56 ± 1.06 D in Grade IV. Moreover, reduction obtained on 30 days was 0.66 ± 0.30 D in Grade I, 0.71 ± 0.32 D in Grade II, 1.82 ± 0.27 D in Grade III, and reduced up to 2.72 ± 0.53 D in Grade IV [Table 1] and [Figure 1]. After 30-day follow-up visit, it was found that 14% patients had mean keratometric astigmatism of 0.6–1 D, one patient had 0.1–0.5 D, and only one patient presented with 1–1.25 D in Grade I. Patients with Grade II presented 0.6–1 D keratometric astigmatism in 30% patients, 0.1–0.5 D in 22%, and 1–15 D in 6% cases. Pterygium Grade III included 8% cases with 0.6–1 D and 12% cases with 0.1–0.5 D of mean keratometric values, while 2% cases had 2.5 D and 2% cases with 3–3.5 D in pterygium Grade IV.

Figure 1: Pre- and postoperative mean astigmatic changes according to the grading of pterygium

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Table 1: Distribution of cases in relation to grade of pterygium and mean astigmatism

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Discussion

The results of our study revealed that the amount of astigmatism increases with increasing grades of pterygium, and the significant reduction in keratometric astigmatism was noticed after pterygium excision surgery with limbal conjunctival autograft technique. As pterygium-induced astigmatism causes gradual loss of vision and when it involves central visual axis, vision is severely hampered.^[7] The pooling of the tear film at the leading edge of the pterygium and mechanical traction exerted by pterygium on cornea causes pterygium-induced astigmatism.^[8]

According to our study, pterygium was most common in the second to the fourth decade of life. Similar results were reported by Panchapakesan,^[9] and Gazzard et al.^[10] Another study by Youngson also reported that pterygium was more common in middle age group and rare in extreme ages.^[11] Rural and male preponderance was reported in our study, this is probably because males are exposed more to sun, dust, and wind due to their outdoor works. The results were identical with the earlier study.^[9] The nasal distribution of the pterygium was more common than temporal side.

It has been accepted that pterygium produces its impact on with the rule astigmatism by mechanical pulling or tear film alteration due to the leading edge of pterygium or both.^{[12],[13],[14]} Kalanchiarani et al. also reported that a positive correlation between grading of pterygium and pterygium-induced astigmatism.^[15] As pterygium stretches and flattens the cornea in horizontal diameter, so horizontal diameter increases according to the grades of pterygium and the amount of astigmatism increases. Pterygium-induced astigmatism is reduced by surgical excision of pterygium. There are various studies done with different opinions.^{[13],[16],[17]} There are varieties of excision technique which includes simple excision, excision with closure of conjunctival defect, and excision with autoconjunctival grafting. The difference in pre- and postoperative keratometric astigmatism was significantly reduced in all grades. Bahar et al. observed that there was a reduction of 3.12–2.5D after surgery with no axis change.^[16] Soriano et al. reported corneal astigmatism significantly reduced from 2.41 D to 1.29 D after pterygium excision.^[13] The results of our study coincide with the above-mentioned studies.

Limitations and future directions

In our study, the sample size was small, and majority of participants within the study were included from a single institution which could not truly represent the characteristic of whole population. Thus, the generalizability of results is limited. Future study should include large sample size from different centers.

Conclusion

The amount of keratometric astigmatism is proportional to grades of pterygium (size of pterygium), and pterygium excision with limbal conjunctival autograft significantly reduces the pterygium-induced astigmatism.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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