Pellucid Marginal Degeneration Treatment & Management
- Author: Karim Rasheed, MD, MSc; Chief Editor: Hampton Roy, Sr, MD more...
Spectacle correction usually fails early in the course of pellucid marginal degeneration (PMD), as the degree of irregular astigmatism increases. In early-to-moderate cases, contact lenses are beneficial in providing visual rehabilitation.
- Spectacles and toric hydrophilic contact lenses are useful in mild pellucid marginal degeneration.
- Spherical hydrophilic contact lenses cannot correct the astigmatism associated with this condition.
- Hybrid contact lenses, which are easier than other lenses to fit to the ectatic cornea, may provide good vision for some patients; however, their poor oxygen permeability often leads to corneal neovascularization, which may adversely affect the prognosis for future corneal transplantation.
- Rigid gas permeable contact lenses provide excellent oxygen transmission to the cornea but are harder than the other lenses to fit.
- Problems in fitting result from the flattening of the superior cornea and the high degree of against-the-rule astigmatism that often causes the lens to dislocate inferiorly.
- The upper eyelid may support large-diameter rigid lenses with a high edge lift, but they often cause marked irritation and move excessively with movements of the eyelids, causing the patient's vision to periodically blur.
- Rigid gas permeable contact lenses may improve the vision of patients with pellucid marginal degeneration, as in those with keratoconus. However, evidence that these lenses have any effect on the progression of the disease is lacking.
- Scleral rigid contact lenses or "mini scleral" contact lenses made from gas permeable materials are an excellent alternative if fitted by a skilled practitioner.
In patients who cannot tolerate contact lenses or in those who do not achieve adequate visual acuity with rigid contact lenses because of the degree of ectasia, surgery may be considered.
A number of surgical procedures have been performed to provide visual rehabilitation. Standard-sized penetrating keratoplasty may produce poor results because the inferior edge of the transplant has to be sutured to an abnormally thin cornea, causing a high degree of postkeratoplasty astigmatism in the short- and long-term period. Continued thinning of the host cornea in the inferior aspect produces a situation similar to the situation that indicated surgery.
- Large-diameter grafts have been tried to remove as much of the affected cornea as possible, with good success. However, because of the proximity to the limbus and its blood vessels, these grafts may be prone to rejection.
- Regular-sized grafts that are deliberately decentered in the inferior aspect also work poorly. The degree of astigmatism is large because of the decentering, and the incidence of rejection is high because of the proximity to the limbus.
- Thermokeratoplasty and epikeratophakia are of only historical interest because the results obtained with these techniques are extremely poor.
- Excision of a crescentic wedge of corneal tissue from the inferior cornea, followed by tight suturing, has been reported to reduce the corneal ectasia.
- The procedure is usually well tolerated; however, the effect is typically short lived, and thinning and ectasia recur.
- In addition, this procedure may be hazardous in inexperienced hands. Several instances of wound dehiscence and resultant flat anterior chambers with its attendant problems have been reported with attempts of this procedure.
- Crescentic lamellar keratoplasty, in which a crescentic transplant is performed to reinforce the area of thinning, has been described, but it may result in a high degree of astigmatism that necessitates subsequent central penetrating keratoplasty.
- Currently, the combination of peripheral lamellar crescentic keratoplasty, followed by a central penetrating keratoplasty after a few months is a favored surgical treatment.
- The lamellar transplant restores normal thickness to the inferior cornea and enables good edge-to-edge apposition at the time of penetrating keratoplasty, reducing the possibility of high postkeratoplasty astigmatism.
- Furthermore, the central graft that is now sutured to normal-thickness host tissue can be treated with videokeratography-guided selective removal of sutures and astigmatic keratotomy in the usual way to reduce any residual astigmatism.
- Ophthalmologists have begun performing the 2 operations in the same sitting, with encouraging results, though this approach is technically difficult.
- Performing 2 keratoplasty procedures at different times necessitates the use of 2 separate corneas. By performing the 2 procedures in the same sitting, tissue from the same donor may be used, potentially reducing the antigenic load.
- Because a central graft almost always is needed, performing both procedures at the same time significantly decreases the time needed to attain best-corrected acuity; this is shown in the image below. This consideration is important, as patients are often young and in the active and working phase of their lives.
- The femtosecond laser has also been used to make lamellar dissections to place Intacs and Intracorneal ring segments.[2, 3]
- Corneal collagen cross linkage also may be of benefit in preventing progression.
- Long-term follow-up is required to assess the efficacy of these newer procedures.
Treatment of pellucid marginal degeneration with either contact lenses or surgery requires considerable experience. A cornea specialist should be consulted to ensure the best visual outcome.
Oie Y, Maeda N, Kosaki R, Suzaki A, Hirohara Y, Mihashi T, et al. Characteristics of ocular higher-order aberrations in patients with pellucid marginal corneal degeneration. J Cataract Refract Surg. 2008 Nov. 34(11):1928-34. [Medline].
Ertan A, Bahadir M. J. Intrastromal ring segment insertion using a femtosecondlaser to correct pellucid marginal corneal degeneration. J Cataract Refract Surg. 2006 Oct. 32(10):1710-6. [Medline].
Ghajarnia M, Moshirfar M, Mifflin MD. Descemet detachment after femtosecond-laser-assisted placement of intrastromal ring segments in pellucid marginal degeneration. J Cataract Refract Surg. 2008 Dec. 34(12):2174-6. [Medline].
Rasheed K, Rabinowitz YS. Results of combined lamellar and penetrating keratoplasty for pellucid marginal degeneration [abstr]. Ophthalmol Suppl. 1997. Oct:191.
Javadi MA, Karimian F, Hosseinzadeh A, Noroozizadeh HM, Sa'eedifar MR, Rabie HM, et al. Lamellar crescentic resection for pellucid marginal corneal degeneration. J Refract Surg. 2004 Mar-Apr. 20(2):162-5. [Medline].
Krachmer JH. Pellucid marginal corneal degeneration. Arch Ophthalmol. 1978 Jul. 96(7):1217-21. [Medline].
Kymionis GD, Aslanides IM, Siganos CS, Pallikaris IG. Intacs for early pellucid marginal degeneration. J Cataract Refract Surg. 2004 Jan. 30(1):230-3. [Medline].
Maccheron LJ, Daya SM. Wedge resection and lamellar dissection for pellucid marginal degeneration. Cornea. 2012 Jun. 31(6):708-15. [Medline].
Maguire LJ, Klyce SD, McDonald MB, Kaufman HE. Corneal topography of pellucid marginal degeneration. Ophthalmology. 1987 May. 94(5):519-24. [Medline].
Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998 Jan-Feb. 42(4):297-319. [Medline].
Schanzlin DJ, Sarno EM, Robin JB. Crescentic lamellar keratoplasty for pellucid marginal degeneration. Am J Ophthalmol. 1983 Aug. 96(2):253-4. [Medline].