Introduction

Presbyopia, often called eyestrain, is the condition of the eye that leads a human being of a certain age to have difficulty seeing close up.

Presbyopia is as old as mankind, the earliest reference to visual fatigue was probably from Aristotle (384-322 BC)1 who used the term presbytes, a word which in Greek meant "old man", from which the word presbyopia derived. Other ancient references to presbyopia can be found in some Latin authors: Cicero (Marcus Tulius Cicero, 106-43 BC)2, Lucius (Mestrius Plutarchus, 45-120 BC)2 and Cornelius Nepote (C. Cornelius Nepos, 24 BC)2.

Amato Lusitano (1511-1568)3 great teacher of Medicine in Healing 77, Quinta Centuria; 1561 <in qua agitur de viso diminuito...> left us a very complete report on Ophthalmology of his time.

In this period, in addition to other doctors, Johannes Kepler (1611)4 assumed the existence of three types of vision: short (good vision for near), long (for far) and neutral (far and near).

It was the Spanish Benito Daça de Valdés5 who in 1623 first made the correct description of Presbyopia in the first book on Ocular Optics "Use of spectacles for all kinds of visions" <in which one learns to know the degrees that each one is missing from his sight, and those who have any spectacles...>, with the reference that those who wanted good "spectacles" had to order them to "Madrid or Lisbon", clearly and accurately describing that "tired sight or poor sight is what older people have”.

As a curiosity, the Summary by Christopher Rodrigues Oliveira in 15513 shows the existence in Lisbon of four men who make glasses. At the same time, in 1554 the queen D. Catarina (1507-1578) ordered a Frenchman twenty-four pairs of spectacles in "veryll" stone, a variety of emerald abundant in India.

But it was Sturn (1697)6 who definitively established the term of Presbyopia to this physiological defect from the Greek (presbys, "old" plus ops "eye").

Presbyopia has its history linked to accommodation and to glasses for its correction.

ACCOMMODATION

Accommodation is understood as the capacity that the eye has to focus on an object when the distance varies.

The underlying cause for the loss of accommodation in presbyopia has not yet been elucidated and remains a subject of controversy among the medical community.

The accommodative phenomenon is characterized by a triple pseudo-synergy of movements that are generally simultaneous but which in special circumstances may act independently: accommodation, convergence, and accommodative miosis or Scheiner's phenomenon7.

In this chapter we will talk about the first thoughts and theories about accommodation, as well as the first methods used for centuries to correct it.

It was the Italian Benedictine Francesco Maurolico (Maurolycus or Maurolycius) who in 15758 first wrote about accommodation in his treatise on optics entitled "Photisme de lumine et umbra, called De conspiciliis", and discusses lenses, having recognized that crystallinus humor is in fact a convex lens, and includes in this treatise a discussion of the functioning of the eye.

Historically the existence of an accommodative mechanism was first demonstrated by the German Jesuit Christoph Scheiner (1619)7 (Figure 1) in the book published in Innsbruck "Oculus hoc est: Fundamentum opticum". He states that accommodation occurs as a result of modifications of the optical power of the eye obeying the laws of optics.

To prove his theory, he made two holes in a card and observed a target at the same distance and the vision of the target was clear, placing a second target closer the target appears blurred (Figure 2).

Some of the most famous philosophers and scientists of the time were interested in knowing how the eye was accommodating.

Johannes Kepler (Dioptrice, 1611)4 describes accommodation as an antero-posterior lens movement, as occurs in some fish. Although having some support, this theory was not accepted because these movements (about 10 mm) are not found in mammals9.

Like Maurilico, the French René Descartes (Renatus Cartesius 1637)10,11 also explained accommodation as a modification of the shape or curvature of the lens. In this historical perspective of presbyopia, the existence of the ciliary muscle was still unknown, and Descartes attributed the modification of the lens to the action of its contractile fibers.

For a long time, the lens was wrongly considered a muscular organ, the "musculus crystallinus".

Sturm (Dissertatio de Presbyopia et Miopia, 1697)6 explained the accommodation as a possible modification in the shape of the eyeball with the increase and decrease of the anteroposterior length, causing the retina to approach or move away from the lens, due to the action of the extra-ocular muscles, theory also advocated by Listing12 and Boerhaave13.

The sixteenth and seventeenth centuries were marked by the knowledge of the accommodative mechanism, which generated numerous theories related to Presbyopia. Throughout these centuries many accommodation theories have been formulated: from the antero-posterior enlargement of the eye, modification on the surface of the cornea (Ramsden)14, anterior and posterior movement of the lens (Plempius)15 and even changes in the refractive index of the lens. Many of these theories never gained acceptance except for the work of Descartes who stated that accommodation was due to changes on the surface of the lens.

THE 18th CENTURY

The English physicist Henry Pemberton16 was probably the first to use the term accommodation to describe the ability of the lens to adapt to various distances without having a plausible explanation for it in his dissertation of 1719.

Lobé (1742)17 stated that it was the surface of the cornea that changed.

William Porterfield (A Treatise on the Eye, 1759)18 suggested that accommodation was a consequence of lens changes in adapting to different distances, for which he used Scheiner's simplification as an experiment. He placed two holes at different distances and observed directly having one eye seeing clearly and the other seeing blurred.

Albrech von Haller (1763)19 considered that the contraction of the pupil diminished the diffusion circles, thus explaining the phenomenon, based on a dark chamber present in some animals.

Home (1795)20 observed that the aphakic eye of a young man, still has considerable accommodation, and this is due to the change in the curvature of the cornea in the effort phase.

THE 19TH AND 20TH CENTURIES

The English physician and physicist Thomas Young (1801)21, after several experiments, affirmed that the crystalline lens was in fact responsible for the accommodation and formed his theory stating that an aphakic eye could not accommodate close distances, even though there were reports of accommodation being present in eyes without crystalline22,23. These later however, were based on depth of focus and not on accommodation. The ciliary body had not yet been discovered and he claimed that the changes in the surface of the lens were caused by an inner muscular mechanism.

Purkinje24 observed images of a lamp reflected on the anterior and posterior surface of the lens.

In 1849, Langenbeck25 using a lamp and enlarging the image with a glass was able to observe in one patient that the Purkinje’s images reflected on the anterior surface of the lens became smaller during accommodation, thus concluding that the anterior surface of the lens was more convex during accommodation. He later claimed that the ciliary muscle discovered by Ernest Brücke26,27 and William Bowman28 in 1847, tightened the crystalline lens.

Antoine Cramer (1851)29, based on the observations of Langenbeck, proved that during accommodation the anterior surface of the lens became more convex but that the posterior one did not suffer alterations, and suggested that during accommodation the contraction of the ciliary muscle acted on the choroid, which compressed the vitreous against the posterior surface of the lens, and this pressure increased the anterior curvature.

Hermann von Helmholtz (1855)30,31 (Figure 3), using Purkinje’s procedures, also confirmed Cramer's conclusions, showing that the posterior surface of the lens was also modified, by hypothesizing that during accommodation the ciliary muscle relaxed and the lens became more spherical, concluding that the active accommodative organ was the ciliary muscle that transmitted its action to the lens through the zonula. He later stated that presbyopia was related to age, due to a decrease in accommodation resulting from sclerosis of the lens.

Finally, Helmholtz observed that in aphakia both the older and young patients had no accommodation, because this power depended on the lens.

The German anatomist Heinrich Müller (1858)32 described the existence of circular muscle fibers in addition to the longitudinal ones described by William Bowman in 1847, called the Müller’s muscle, that form a ring of smooth muscle parallel to the edge of the lens, which facilitates its action on the zonula.

Knapp (1860)33 proved that the modifications that the crystalline lens suffered during accommodation, sufficiently explained the variety of accommodation.

In 1864, Donders34 studied the amplitude changes of accommodation with age, and concluded that the accommodation amplitude decreases linearly with age, due to a decrease in the contraction force of the ciliary muscle; this theory was opposite to that of Helmholtz, who blamed the loss of accommodation to crystalline sclerosis with age, which reduced its elasticity.

ACCOMMODATION THEORIES

After knowing the anatomical structure responsible for accommodation by the experiences of Thomas Young (1801), the next step was to know the precise mechanism of accommodation, and there were several theories.

CRAMER (1851) – VITREOUS THEORY

For Cramer, during accommodation the contraction of the ciliary muscle acted on the choroid, which in turn compressed the vitreous against the posterior surface of the lens, and the anterior surface when compressed against the pupil curved, thereby increasing its curvature.

Later this theory was abandoned, when accommodation was demonstrated in patients with aniridia35.

HELMHOLTZ (1853) – THE RELAXATION THEORY

He proposed that on the anterior, posterior and equatorial surfaces, the zonula exerts a simultaneous tension. He noted that when the eye is in a state of no accommodation and focused in the distance, the ciliary muscle is relaxed, and elastic zonular fibers are in a state of tension, pulling the lens out at the equator, and leaving the lens more flattened. During accommodation the ciliary muscle contracts, causing a reduction in the zonular tension, that allows an increase of the curvature and the crystalline thickness (its diopter power increases) with a decrease of the equatorial diameter, an increase in anterior curvature with only a slight change in posterior curvature, and a 0.50 mm increase in the axial thickness of the lens. Since the volume of the lens is constant³⁶, Helmholtz concluded that the equatorial diameter decreases during accommodation.

TSCHERNING (1894) – THE ACCOMMODATION THEORY

Danish ophthalmologist Marius Hans Erik Tscherning37 published his accommodation theory, noting that this occurs due to the temporal formation of an anterior lenticone, and this phenomenon is possible because the superficial layer of the lens (Tscherning’s Accommodative Layer) had the ability to change its shape due to its thick gelatinous consistency. This theory differs from Helmholtz's theory in two basic phenomena:

1. When the ciliary muscle contracts, the zonula instead of relaxing contracts and the anterior surface of the lens increases its curvature forming a central lenticone, accompanied by a flattening of its periphery.
2. Contraction of the pupil during accommodation would eliminate the peripheral parts of the lens, reducing spherical aberration (Koke 1942).

Tschering's theory immediately resulted in a major controversy that persists to this day (Schachar et al, 1993).

ALVAR GULLSTRAND (1911) – THE INTERNAL ACCOMODATION THEORY

According to this theory38, a third of the accommodation was due to the crystalline fibers themselves, increasing the index of refraction in the center. This internal accommodation would enhance external accommodation related to the anterior curvature of the lens. However, this and other theories have not been widely accepted (Atchinson, 1995; Martin et al, 2005).

FINCHAM (1924) – THE THEORY OF PLASTICITY

According to this theory39, the crystalline lens is a plastic organ shaped by an elastic capsule not having its own shape. Its shape is imposed by the elasticity of the capsule and the deformity would be maximal in areas where it is thinner, especially in the anterior central zone, caused by the tension in the zonula that relaxes due to a strong muscular contraction.

Coleman (1970) – THE CATENARY THEORY

In the unified model of accommodation40, later referred to as the theory of hydraulic suspension in 1986, Coleman said that the differential pressure between the vitreous and aqueous spaces acts as a hydraulic change of the crystalline, and showed further that the vitreous-crystalline and aqueous-crystalline system suspended by the zonular fibers, could be compared to a catenary suspension. In this model, the release of tension in the zonular fibers will produce a more pronounced anterior crystalline curvature, with the vitreous resistance to the posterior protuberance of the lens. He argued that the ciliary body is the driving force for a predictable degree of accommodation and that his model explained certain physiological processes that could not be explained only by the widely accepted Helmholtz’s capsular theory. The theory of accommodation of hydraulic suspension is an attempt to explain the respective roles played by the different anatomical structures involved in the accommodative mechanism.

Martin et al41 questioned this theory and Fisher questioned the role of vitreous in accommodation.

SCHACHAR (1993) – ACCOMMODATION THEORY

According to this theory42, the ciliary muscle contracts during accommodation, leading to an increase in the tension of the equatorial fibers of the zonule that accentuates the central surface of the lens (increasing its convexity), increasing the anterior diameter and flattening the peripheral surfaces, while zonular relaxation results in a central flattening and a peripheral tilt of the lens. The crystalline equator is drawn to the sclera by the tension of the equatorial fibers of the zonule.

In this theory the equatorial fibers of the zonule play a dominant role, while the anterior and posterior fibers are passive.

Schachar and Bax43 and other researchers used mathematical models and finite nonlinear elements.

Glasser and Kaufman44 did not agree with this position because their experiences have shown that the crystalline equator moves away from the sclera during accommodation.

CORRECTION OF PRESBYOPIA: GLASSES

In ancient times, people of advanced age with eye fatigue had their slave for reading. This view is supported by a letter written by a prominent Roman, near 100 BC, in which he emphasized his renunciation to old age, because he could no longer read and for that he would have to trust his slaves. As may be imagined, prior to the invention of the spectacles, eyedrops or artifacts were used in order to improve vision.

Historical Perspective of Presbyopia

Senator Seneca (Lucius Annaeus Seneca) born in 4 BC claimed to have read "all the books in Rome", examining them through a glass globe with water to produce magnification. Roman Emperor Nero used an emerald as he watched the gladiators fight, not as a magnifying glass, but probably to filter the sunlight through its green color. Daça de Valdés5 in Chapter XI of the book "Why the Elders Have Distant and Not Near Vision," stated that impaired vision should be aided by wearing glasses and convex lenses.

THE ORIGIN OF THE GLASSES

The first glasses were probably made between 1268 and 1289. The English monk and philosopher Roger Bacon (also known as Dr. Mirabilis) wrote in his Opus Majus in 1268: "if one observes letters or other tiny objects through a glass or another transparent substance and if it has the shape of a small sphere segment with the convex side to the eye, one will see the letters much better and larger”.

On the 23rd of February 1306, the Italian Blessed Giordano da Rivalto de Pisa45, an eminent preacher, gave a sermon at the Church of Santa Maria Novella in Florence and recalled that the invention of glasses, "one of the most useful arts in the world", was already 20 years old, and added, "I saw a man who, first of all, discovered and made a pair of glasses, and I talked to him." Nothing is known of this remarkable inventor, perhaps he was a contemporary of Giordano. Monk Alessandro della Spina, of whom it was told that "he created his glasses and freely taught the art to others," was perhaps a member of the Guild of Venetian Crystal Workers, where the making of glasses was already known in 1301. Salvino D 'Armati (1258-1312) is cited as the inventor of the first glasses in 1285 in Italy, although there are some doubts as to its veracity.

Leopoldo del Migliore in his story about Florence in 1684 wrote that the Church of Santa Maria Maggiore had a memorial in honor of D'Armati with the following inscription: "Here is Salvino degl'Armati, son of Armato of Florence, inventor of glasses. May God forgive his sins, AD 1317". Some historians are suspicious of the claim, since the church has been rebuilt several times.

MYTHS

There are several reports of the discovery and date of the existence of glasses and, for the sake of the history of Ophthalmology, these must be remembered and questioned.

• At the time of Confucius (K'ung Chung-ni or Confucius, 551-479 BC) the glasses were already used in China. This is false, the Chinese themselves do not claim to be the inventors of the glasses and even there, there are no reports of their existence.
• Emperor Nero (Claudius Caesar Nero, 54-68 BC) used a green emerald to protect himself from the glare of light in the gladiatorial struggle. Just as Plinius (Plinius Secundos, 23-70 BC), who ruled Spain, also speaks of emeralds.
• The English Monk and Philosopher Roger Bacon (1214-1294), likely inventor of the glasses in 1268, was also denied centuries later. Perhaps he was the first to make known in writing the possibility of correcting presbyopia with magnifying glasses.
• Marco Polo (1254-1324) in the book “The Travels of Marco Polo”, refers to the existence of glasses in China before the birth of Christ, but there are no proofs or passages of their existence. When consulting several translations and editions, in all of them Marco Polo refers to several things that were strange to him, but in none he mentions the glasses. However, his arrival in Venice in 1295 coincides with the discovery of the glasses; perhaps here lies the confusion.