Pellucid marginal degeneration (PMD) is an uncommon bilateral ectatic disorder of the cornea, orginally described by Schlaeppi in 1957.1 It is characterized by an area of noninflammatory crescent-shaped thinning in the lower periphery of the cornea. In PMD, the keratocytes reduce or alter the normal sulfatation pattern of the keratan sulfates.2
We treated both eyes in a patient presenting with PMD associated with cataracts. In 1991, a 66-year-old man was admitted for progressive loss of vision over several years. On examination, visual acuity was less than 0.1 in each eye (no correction possible with spectacles and intolerance to contact lenses). Posterior nuclear and subcapsular opacities were observed in both lenses. The corneas were transparent, but a thinning was noted in the inferior paralimbal portion, with corneal ectasia above the thinned area. Javal keratometry revealed irregular astigmatism with a magnitude exceeding the recording range of the keratometer. Based on these findings, the diagnosis of PMD was made.
In May 1991, we performed a combined technique consisting of phacoemulsification through an inferior approach followed by wedge keratectomy. Using the inferior approach, we made a nonperforating centripetal incision in the cornea to a depth of 90%, distal to the degenerated area and between the 4 and 8 o'clock positions. A lamellar dissection, 2.0 to 3.0 mm in width, was made between the 2 incisions at the pre-Descemet's level. The cataract was removed through this space by phacoemulsification. Thereafter, increasing each preincision, a full-thickness trapezium of corneal tissue was extracted.
On the first day postoperatively, keratometry of the left eye showed a highly regular astigmatism of −14.0 diopters (D) at 160 degrees. With optical correction, the patient's visual acuity was 0.5 with difficulty. At 6 weeks, the regular astigmatism was decreased to −0.5 D at 165 degrees with an uncorrected visual acuity of 0.7 partial. At 5 months, UCVA was 0.7 partial with −6.0 D at 93 degrees.
On the first postoperative day, keratometry of the right eye was −10.0 D at 170 degrees; however, with an irregular component. At 2 months, we observed an irregular astigmatism of approximately −3.0 D at 90 degrees, with the onset of vascularization and localized ectasia at the incision (Figure 1), so we decided to reoperate and perform an additional wedge keratectomy of the ectatic inferior nasal area. At the fourth month, keratometry was −3.0 D at 20 degrees, with a small irregularity in the keratometric figures.
The patient was re-examined 8 years after surgery, presenting with a cylinder of −10.0 D at 90 degrees (left eye) and −10.5 D at 90 degrees (right eye). His visual acuity was 8/10 with correction of +1.50 −6.00 × 90 in the left eye and 5/10 with correction of +0.75 −6.00 × 90 in the right eye. Because of the patient's intolerance to contact lenses, we planned to perform arcuate incisions posteriorly.
The standard management of PMD is keratoplasty. Between 1974 and 1978, Varley and coauthors3 performed a penetrating keratoplasty with a large eccentric graft in 12 eyes (11 patients) to finally obtain visual acuities of 20/30 and a mean astigmatism of 2.46 D in the short term.
Others (Pouliquen et al.,4 Parker and coauthors,5 and Speaker and coauthors6) report the same technique, also with visual acuities of around 20/30. Some authors have performed other methods; a large lamellar keratoplasty (Kremer and coauthors7) or an epikeratoplasty (Fronterrè and Portesani8). Dubroff9 and Cameron10 performed a wedge resection followed by relaxing incisions, obtaining satisfactory results in the short term, as in our case, but they have not reported the long-term effects as we do. Durán and coauthors11 used the technique of crescentic resection as a treatment for PMD and reported satisfactory results.
Similar to other authors, we think resection has several advantages over keratoplasty. The interest of this study lies in the fact that we monitored development over a long period (8 years) and stress that the decrease in induced astigmatism was considerable at the beginning but seemed to become stable about a year after surgery in ectatic corneas.
Pellucid macular degeneration appears rarely in elderly persons, but its association with cataract may be found, as in our case, creating the need to find a surgical technique that solves both problems in a single operation. We think that our combined technique of inferior phacoemulsification followed by wedge keratectomy may provide PMD patients with a satisfactory refractive solution during the early postoperative period, when spectacles can correct the residual astigmatism. Another surgical possibility is to perform the phacoemulsification temporally through a temporal corneal incision and do a large wedge resection inferiorly.
Bearing in mind that PMD is a progressive ectatic corneal disease, postoperative recurrence is possible if the results are analyzed over a long period, as happened in our patient. This is why we question the validity of other short-term studies. To prevent recurrence of the disease, one may try to perform a larger inferior wedge resection to embrace a larger area of pathological cornea.12, 13, 14, 15, 16.
Ma Elena Rodríguez-Gonzáles-Herrero MD
Angel Ramón Gutiérrez Ortega MD
Jaime Miralles de Imperial Mora-Figueroa MD
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